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88525ca373d6c27ca925fc02f42c683a | 23.007 | 16.1.0 SGW Failure | When a SGW fails, all its Bearer contexts affected by the failure become invalid and may be deleted. SGW storage of subscriber data is volatile.
When the SGW receives a GTP‑U PDU for which no Bearer context exists, it shall discard the GTP‑U PDU and return a GTP error indication to the originating node (the PGW, the eNodeB, the S4-SGSN, or if Direct Tunnel is established, the RNC) or follow the procedures specified in clause 27.2.2.5 if the restoration of PDN connections after an SGW failure is supported.
The SGW should ensure as far as possible that previously used TEID values are not immediately reused after a SGW restart, in order to avoid inconsistent TEID allocation throughout the network. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 16.1.1 Restoration Procedures | After an SGW restart, the SGW shall delete all MM Bearer contexts affected by the restart that it may have stored.
During or immediately after an SGW Restart the SGW shall place local SGW restart counter value in all GTPv2 Echo requests/responses messages and PMIPv6 heartbeat responses the SGW sends.
16.1a Restart of the SGW-C
16.1a.1 SGW-C failure
When a SGW-C fails, all its Bearer and Session contexts, Sx Association(s) affected by the failure become invalid and may be deleted.
If F-TEID allocation is performed in the SGW-C, the SGW-C should ensure as far as possible that previously used F-TEID values are not immediately reused after a SGW-C restart, in order to avoid inconsistent TEID allocation throughout the network.
NOTE: This is to ensure that F-TEIDs are not reused until earlier PDN connections using them are released e.g. in eNB or PGW.
16.1a.2 Restoration procedure
During or immediately after an SGW-C Restart, the SGW-C shall place local SGW-C Recovery Time Stamp value in all Heartbeat Request/Response and Sx Association Setup Request/Response Messages.
16.1b Restart of the SGW-U
16.1b.1 SGW-U failure
When a SGW-U fails, all its Sx session contexts and Sx Association(s) affected by the failure become invalid and may be deleted.
If F-TEID allocation is performed in the SGW-U, the SGW-U shall ensure that previously used F-TEID values are not immediately reused after a SGW-U restart, in order to avoid inconsistent TEID allocation throughout the network and to enable the restoration of Sx sessions affected by the failure. How this is ensured is implementation specific.
NOTE: As the user plane F-TEID pool is partitioned in the SGW-U across the multiple SGW-Cs controlling the SGW-U, the SGW-U does not need to wait for the re-establishment of all the Sx associations from all SGW-Cs to start assigning new F-TEID for new Sx sessions for a particular SGW-C.
16.1b.2 Restoration procedure
During or immediately after an SGW-U Restart, the SGW-U shall place local SGW-U Recovery Time Stamp value in all Heartbeat Request/Response and Sx Association Setup Request/Response Messages.
16.1A Restart of a peer node
16.1A.1 MME/S4-SGSN Failure
16.1A.1.1 General
The SGW will receive the MME/S4-SGSN restart counter in GTPv2 Echo requests and Echo response messages that the SGW receives from the MME/S4-SGSN.
When an SGW detects that a peer MME /S4-SGSN has restarted (see clause 18 "GTP-C based restart procedures") it shall either:
- delete all PDN connection table data/MM bearer contexts associated with the peer node that fails as well as freeing any internal SGW resources associated with those PDN connections. The SGW may optionally perform other implementation specific actions such as messages to clear other external resources (e.g. PCC messages to clear the resources in the PCRF or GTP/PMIP messages to release the corresponding PDN connection in the PGW);
or
- follow the network triggered service restoration procedure as specified in clause 25 if the MME, the S4-SGSN and the SGW support this procedure.
16.1A.2 PGW Failure
The SGW will receive the PGW restart counter in GTPv2 Echo requests/ responses and PMIPv6 heartbeat responses that the SGW receives from the PGW.
When an SGW detects that a peer PGW has restarted (see clause 18 "GTP-C based restart procedures") it shall delete all PDN connection table data/MM bearer contexts associated with the peer node that fails as well as freeing any internal SGW resources associated with those PDN connections. In addition, if the optional feature PGW Restart Notification is supported by the SGW and MME/S4-SGSN as specified in clause 8.83 in 3GPP TS 29.274[13], the SGW shall initiate the cleanup of the hanging PDN connections associated with the SGW and the restarted PGW at the corresponding MMEs/S4-SGSNs by sending GTPv2 message(s) PGW Restart Notification, with the control plane IP address of the restarted PGW and the control plane IP address of the SGW on the S11/S4 interface included. The SGW may optionally perform other implementation specific actions such as messages to clear other external resources (e.g. PCC messages).
If an SGW detects that a peer PGW has failed and not restarted, it may delete all PDN connection table data/MM bearer contexts associated with the peer node that fails as well as freeing any internal SGW resources associated with those PDN connections. In addition, if the optional feature PGW Restart Notification is supported by the SGW and MME/S4-SGSN as specified in clause 8.83 in 3GPP TS 29.274[13], the SGW may also send a PGW Restart Notification message to the MME or S4-SGSN. The PGW Restart Notification message shall include the control plane IP address of the PGW, the control plane IP address of the SGW on the S11/S4 interface and the cause value "PGW not responding". It is an implementation matter how an SGW becomes aware that a PGW has failed and has not restarted, e.g. the SGW detects a signalling path failure with the PGW for a duration exceeding the maximum path failure duration timer (see clause 20.2.1).
When the MME/S4-SGSN receives this message, according to the control plane IP address of the restarted PGW and the control plane IP address of the SGW on the S11/S4 interface included in the message, the MME/S4 SGSN should delete all PDN connection table data/MM bearer contexts associated with the SGW and the restarted PGW as well as freeing any internal MME/S4-SGSN resources associated with those PDN connections. Additionally the MME/S4-SGSN may decide to restore certain PDN connections based on operator's policy e.g. based on the QCI and/or ARP and/or APN. If so,
- the S4-SGSN shall deactivate the corresponding PDN connections using the "reactivation requested" cause value as specified in clause 9.2.4.2 of 3GPP TS 23.060 [5];
- the MME shall deactivate the corresponding PDN connections using the "reactivation requested" cause value as specified in clause 5.10.3 of 3GPP TS 23.401 [15] if only a subset of the PDN connections of the UE need to be restored or if the UE has a SCEF PDN connection or if the UE supports Attach without PDN connectivity as specified in clause 5.3.8.3 of 3GPP TS 23.401 [15]; if all the PDN connections of the UE need to be restored and the UE does not have a SCEF PDN connection and the UE does not support Attach without PDN connectivity, the MME shall initiate the "explicit detach with reattach required" procedure as specified in clause 5.3.8.3 of 3GPP TS 23.401 [15].
The MME/S4-SGSN may prioritize the PDN connections to restore based on operator's policy e.g. based on the QCI and/or APN. Besides, the MME/SGSN may use the subscribed Restoration Priority per APN, if received from the HSS, and if permitted by service level agreements for in-bound roamers, to determine the relative restoration priority among PDN connections to the same APN. The MME/SGSN may use a locally configured value as default restoration priority if the restoration priority for a user's PDN connection is not received from the HSS or not permitted by service level agreement for in-bound roamers.
NOTE 1: The Restoration Priority can e.g. allow to restore with a higher priority users with an IMS voice subscription over IMS users without an IMS voice subscription.
The MME/S4-SGSN may optionally perform other implementation specific actions such as to clear external resources (e.g. S1-MME messages to clear eNodeB resources or Iu messages to clear RNC resources) or more advanced forms of restoration.
NOTE 2: The SGW will have the identity of the MME/S4-SGSN and PGW currently in use for a PDN connection available in the SGW's PDN connection table as part of existing EPC procedure.
If PMIPv6 based S5/S8 interface is used and if the SGW needs to send a request for Gateway Control and QoS Policy Rules Provision procedure towards a PCRF which is known to have restarted since the Gateway Control Session Establishment, the SGW may discard the request and may tear down the associated PDN connection, based on operator policy, by sending a Delete Bearer Request message for the default bearer towards the MME/S4-SGSN with the cause set to "Reactivation requested". Additionally, SGW initiates an SGW initiated PDN Disconnection procedure towards PGW. This leads the UE to initiate a UE requested PDN connectivity procedure for the same APN. Emergency and eMPS sessions should not be torn down.
NOTE 3: The procedure above just enables to clean up the PDN connection affected by the PCRF failure when a specific interaction with the PCRF is required. Prior to that interaction, PCC controlled services cannot be provided to the UE.
For a split SGW, if the SGW-C detects a PGW failure, it shall initiate a Sx Session Deletion procedure towards the SGW-U.
16.1A.3 SGW-C Failure
The SGW-U will receive the recovery time stamps of the PFCP entity(ies) in the SGW-C in PFCP heartbeat request/response messages.
When an SGW-U detects that a peer PFCP entity in the SGW-C has restarted, the SGW-U shall delete all its Sx session contexts affected by the restart. When the SGW-U receives a GTP‑U PDU not matching any PDRs, it shall discard the GTP‑U PDU and return a GTP error indication to the originating node (the PGW, the eNodeB, the S4-SGSN, or if Direct Tunnel is established, the RNC); as an exception, if the restoration of PDN connections after an SGW failure is supported as specified in clause 27, the SGW-U shall not send Error indication message for a configurable period after the restart in the SGW-C.
NOTE: The period needs to be longer than the time required for the peer node to detect the restart of the SGW-C, e.g. the interval between two echo request messages. This ensures that the MME/SGSN or PGW does not deactivate the bearers before it detects the SGW-C failure and triggers the restoration procedure.
When a SGW-U detects that a peer PFCP entity in the SGW-C is not reachable for a preconfigured time, the SGW-U shall delete all session contexts affected by the unreachability of the peer PFCP entity in the SGW-C that it may have stored.
16.1A.4 SGW-U Failure
The SGW-C will receive the recovery time stamps of the PFCP entity(ies) in the SGW-U in PFCP heartbeat request/response messages.
After an SGW-U restart, the Sx association between SGW-C(s) and the SGW-U has to be re-established.
NOTE: The SGW-C can determine to re-establish the Sx Association if it receives the cause code "No established PFCP Association" in a response message, or if it detects all peer PFCP entities in the SGW-U have restarted.
Restoration of Sx sessions includes:
- if re-establishment of Sx association is required, the SGW-C may start immediately the Sx association setup procedure, and then;
- when re-establishing a Sx session and if F-TEID allocation is performed in the SGW-U by network configuration, the SGW-C shall include a restoration indication in the PFCP Session Establishment Request message to indicate to the SGW-U it is for a restoration of an existing PFCP session and the SGW-U shall accept SGW-C allocated F-TEID if possible.
- if the restoration is supported in the SGW-C on a proactive basis, the SGW-C may start re-establishing Sx sessions matching any PDRs.
- if the restoration is supported in the SGW-C on a reactive basis:
- the SGW-C shall establish an Sx session with a wildcarded PDR to instruct the UP function to forward G-PDU packets which are not matching any other PDRs to the CP function (to a F-TEID uniquely assigned in the CP function for this Sx-u tunnel);
- upon receipt of G-PDUs from this Sx-u tunnel, the CP function shall then check if it has an active session for each received G-PDU packet:
- if so, the CP function shall perform Sx Session establishment procedures to re-establish the corresponding Sx sessions in the SGW-U;
- otherwise the CP function shall generate a GTP-U Error Indication with a destination address set to the source IP address of the received G-PDU, and send it to the UP function. The UP function shall forward this GTP-U Error Indication transparently. The CP function shall delete the G-PDU after the check for active sessions.
NOTE 1: The SGW-U can filter the G-PDU packets with same target F-TEID and send only one such G-PDU to the CP function.
NOTE 2: Such Sx-u tunnel to forward GTP-U Error Indication can be established per UP function and can also be used to send End Marker packets generated by the CP function. See clause 5.3.2 of TS 29.244 [43]
The SGW-U shall not send Error indication message for a configurable period after a PFCP entity restart in the SGW-U when the SGW-U receives G-PDU not matching any PDRs.
NOTE 3: If restoration on a reactive basis is used, the period needs to be longer than the time required by the SGW-C to detect the SGW-U restart, establish the Sx association and provision the wildcarded PDR. Otherwise, the period needs to be longer than the time required by the SGW-C to restore all the Sx sessions on a proactive basis.
When the SGW-C detects the failure of an SGW-U without a restart, the SGW-C may select an alternative SGW-U which can take over the IP addresses of the failed one to restore the Sx sessions in the UP function. How this is performed is implementation specific. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 16.2 Partial Failure Handling at SGW | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 16.2.1 General | See Clause 23.
In addition, the following applies. If an SGW, which supports the feature receives Delete PDN Connection Set Request/Reply messages from MME or the PGW it shall forward the messages to the appropriate peer.
If the SGW does not support the feature then partial failure handling does not apply to that specific PDN connection. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 16.2.2 Procedures during PDN Connection Establishment | If the SGW supports the feature, the following procedures apply.
During a PDN connection establishment, the SGW shall provide one SGW FQ-CSID for that particular PDN connection to the PGW. Similarly, the SGW shall provide one SGW FQ-CSID for that particular PDN connection to the MME if the MME supports partial failure handling. The SGW shall store the Node-ID and CSID from the FQ-CSID provided by the PGW and the MME respectively for that particular PDN connection in its PDN Connection table maintained as part of "EPS Bearer Contexts" table as specified in Table 5.7.3-1 in 3GPP TS 23.401 [15].
The SGW shall forward the MME FQ-CSID provided by the MME on S11 to the PGW in the S5/S8 Create Session Request (Proxy Binding Update for PMIPv6) for that PDN connection. Similarly, the SGW shall forward the PGW FQ-CSID provided by the PGW on S5/S8 to the MME in the S11 Create Session Response for that PDN connection if the MME supports partial failure handling.
The SGW determines that the MME supports partial failure handling by the presence of the MME FQ-CSID in the S11 Create Session Request.
The SGW determines that the PGW supports partial failure handling by the presence of the PGW FQ-CSID in the S5/S8 Create Session Response for GTPv2 based S5/S8 and the Proxy Binding Acknowledgement for PMIPv6 based S5/S8. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 16.2.3 Procedures during SGW Partial Failure | If the SGW supports the feature, the following procedures apply.
When an SGW detects that it has undergone a partial failure, it shall verify that one or more corresponding CSID(s) are present for the component undergoing a partial fault. If there is no such CSID, then the following does not apply. When one or more CSIDs are currently assigned, the SGW shall perform the following.
The SGW may perform implementation-specific operations to clean up any residual state associated with the CSID(s).
The SGW shall send the GTPv2 Delete PDN Connection Set Request containing all the SGW CSIDs of the component(s) failing in SGW FQ-CSID to MME peers supporting the feature. The SGW shall send the GTPv2 Delete PDN Connection Set Request (or PMIP6 Binding Revocation Indication with G bit set) message containing the equivalent SGW FQ-CSID(s) to PGW peers supporting the feature.
Upon receiving a GTPv2 Delete PDN Connection Set Response message with Cause value "Success", the SGW shall conclude that the PGW (for GTPv2 S5/S8) or the MME (for S11) has initiated the internal deletion of the PDN connections corresponding to the FQ-CSID(s) present in the GTPv2 Delete PDN Connection Set Request message. Similarly, upon receiving a successful PMIP6 Binding Revocation Acknowledgment message with G bit set, the SGW shall conclude that the PGW has initiated the internal deletion of the PDN connections corresponding to the CSID(s) present in the PMIP6 Binding Revocation Indication message.
The SGW is not required to perform any further recovery actions towards MME and PGW peers for PDN connections in the connection set identified by the SGW FQ-CSID(s). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 16.2.4 Procedures during a Peer's Partial Failure | If the SGW supports the feature, the following procedures apply.
When an SGW receives a S11 GTPv2 Delete PDN Connection Set Request message from an MME, the SGW shall retrieve all the PDN connections corresponding to each of the FQ-CSID(s) present in the message. The SGW shall send a S5/S8 GTPv2 Delete PDN Connection Set Request (or PMIP6 Binding Revocation Indication with G bit set) message containing the FQ-CSID(s) provided by the MME to PGW peers supporting the feature. The SGW shall delete all the retrieved PDN connections and the associated resources. Other implementation-specific actions may be performed.
As a response, the SGW shall send a S11 GTPv2 Delete PDN Connection Set Response message with an appropriate Cause value immediately to the MME.
When an SGW receives a S5/S8 GTPv2 Delete PDN Connection Set Request (or PMIP6 Binding Revocation Indication with G bit set) message from a PGW, the SGW shall retrieve all the PDN connections corresponding to each of the FQ-CSID(s) present in the message. The SGW shall send a S11 GTPv2 Delete PDN Connection Set Request message containing the FQ-CSID(s) provided by the PGW to MME peers supporting the feature. The SGW shall delete all the retrieved PDN connections and the associated resources. Other implementation-specific actions may be performed.
As a response, the SGW shall send a S5/S8 GTPv2 Delete PDN Connection Set Response message with an appropriate Cause value to the PGW. On PMIP6-based S5/S8 interface, the SGW shall send a PMIP6 Binding Revocation Acknowledgment message with G bit set.
If the SGW detects the full/complete failure of an MME or PGW, e.g., through the Echo Request/Echo Response procedure, it may send a Delete PDN Connection Set Request (or PMIP6 Binding Revocation Indication with G bit set) message, containing all of the FQ-CSIDs of the associated hanging PDN connections of the failed node, to the corresponding remote node (MME or PGW). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 16.2.5 Procedures during PDN Connection Removal or Modification | Only if the SGW supports the feature, the following procedures apply.
During a S11 or an S5/S8 procedure, impacting an existing PDN connection removal or modification the following apply:
1) If the MME is being relocated then the SGW shall clear the currently stored MME FQ‑CSID value (if any).
2) For inter MME and intra SGW HO/TAU, and if the new MME supports the feature, then the SGW shall:
- include SGW FQ-CSID in the S11 Modify Bearer Response. If PGW supports the feature, the SGW shall also include PGW FQ-CSID into the message.
- inform the feature supporting PGW about the change of FQ-CSID values with the following messages:
- Modify Bearer Request, when Modify Bearer Request message needs to be sent to the PGW as specified in the 3GPP TS 23.401 [15], e.g. if the sending of this message is triggered by user location reporting procedure. The message shall contain both SGW FQ-CSID and MME FQ-CSID.
- Update PDN Connection Set Request message, only if Modify Bearer Request is not sent. The message shall contain both SGW FQ-CSID and MME FQ-CSID.
- Proxy Binding Update (if PMIPv6 is used). The message shall contain both SGW FQ-CSID and MME FQ-CSID.
3) For inter MME and intra SGW HO/TAU, and if the new MME does not support the feature, then the SGW shall:
- not include any FQ-CSID in the S11 Modify Bearer Response.
- inform the feature supporting PGW with the following messages:
- Modify Bearer Request when Modify Bearer Request message needs to be sent to the PGW as specified in the 3GPP TS 23.401 [15], e.g. if the sending of this message is triggered by user location reporting procedure. The message shall contain only SGW FQ-CSID.
- Update PDN Connection Set Request message, only if Modify Bearer Request is not sent. The message shall contain only SGW FQ-CSID.
- Proxy Binding Update (if PMIPv6 is used). The message shall contain only the SGW FQ-CSID.
NOTE: The patial failure handling is not supported by the S4-SGSN, therefore, during the RAU/HO to S4-SGSN procedure, the SGW can behave in the same way as the TAU/HO to a MME which does not support the feature.
4) For inter SGW HO/TAU, if the new MME supports the feature, then the new SGW shall:
- include SGW FQ-CSID in the S11 Create Session Response. If PGW supports the feature, the SGW shall also include PGW FQ-CSID into the message.
- inform the feature supporting PGW about the change of FQ-CSID values with the following messages:
- Modify Bearer Request. The message shall contain both SGW FQ-CSID and MME FQ-CSID.
- Proxy Binding Update (if PMIPv6 is used). The message shall contain both SGW FQ-CSID and MME FQ-CSID.
5) For inter SGW HO/TAU, if the MME does not support the feature, then the SGW shall:
- not include any FQ-CSID in the S11 Create Session Response.
- inform the feature supporting PGW about the change of SGW FQ-CSID value with the following messages:
- Modify Bearer Request. The message shall contain only SGW FQ-CSID
- Proxy Binding Update (if PMIPv6 is used). The message shall contain only the SGW FQ-CSID.
6) If the SGW receives a FQ-CSID value of a PGW over S5/S8, or a FQ-CSID value of a MME over S11, the SGW shall overwrite the current stored FQ‑CSID value with the received value.
7) During the PDN connection removing procedures, a PGW removes the PDN data as well as any stored FQ-CSID values(s) of the MME and SGW FQ-CSIDs.
8) For the following procedures, if the procedures as specified in 3GPP TS 23.401 [15] e.g. Location Change reporting is enabled, the SGW shall send its own FQ-CSID and the MME FQ-CSID in Modify Bearer Request and Proxy Binding Update across S5/S8 interface to the respective PGW even if the MME did not update its FQ-CSID, e.g.:
- X2-based Handover without SGW relocation
- TAU without MME and without SGW relocation
- UE Triggered Service Request
During a S11 or S5/S8 procedure removing an existing PDN connection the SGW simply removes the PDN data as well as any stored FQ-CSID values(s) of the PGW FQ-CSID and MME FQ-CSID or pointers to such data. The same actions are done on the old SGW if there is an SGW relocation.
An SGW determines that the MME supports partial failure handling if MME FQ-CSID is present in the received S11 Modify Bearer Request or S11 Create Session Request (with both MME and SGW change) messages.
A new SGW determines that the PGW supports partial failure handling if PGW FQ-CSID is present in the S5/S8 Modify Bearer Response for GTPv2 based S5/S8 or in the Proxy Binding Acknowledgement for PMIPv6 based S5/S8. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17 Restoration of data in the PGW | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.1 Restart of the PGW | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.1.0 PGW Failure | When a PGW fails, all its Bearer contexts affected by the failure become invalid and may be deleted. PGW storage of subscriber data is volatile.
When the PGW receives a GTP‑U PDU for which no Bearer context exists, it shall discard the GTP‑U PDU and return a GTP error indication to the originating node i.e. the SGW/ePDG/TWAN.
The PGW should ensure as far as possible that previously used TEID values are not immediately reused after a PGW restart, in order to avoid inconsistent TEID allocation throughout the network. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.1.1 Restoration Procedures | After a PGW restart, the PGW shall delete all MM Bearer contexts affected by the restart that it may have stored.
During or immediately after a PGW Restart, the PGW shall place this PGW restart counter value in all GTPv2 echo requests/responses and PMIPv6 heartbeat responses the PGW sends.
17.1a Restart of the PGW-C
17.1a.1 PGW-C failure
When a PGW-C fails, all its Bearer, session contexts and Sx associations affected by the failure become invalid and may be deleted.
If F-TEID allocation is performed in the PGW-C, the PGW-C should ensure as far as possible that previously used F-TEID values are not immediately reused after a PGW-C restart, in order to avoid inconsistent TEID allocation throughout the network.
NOTE: This is to ensure that F-TEIDs are not reused until earlier PDN connections using them are released.
17.1a.2 Restoration Procedures
After a PGW-C restart, the PGW-C shall delete all MM Bearer and session contexts, and Sx Associations affected by the restart that it may have stored.
During or immediately after a PGW-C Restart, the PGW-C shall place local PGW-C Recovery Time Stamp value in all Heartbeat Request/Response and Sx Association Setup Request/Response Messages.
17.1b Restart of the PGW-U
17.1b.1 PGW-U failure
When a PGW-U fails, all its Session contexts and Sx associations affected by the failure become invalid and may be deleted.
If F-TEID allocation is performed in the PGW-U, the PGW-U shall ensure that previously used F-TEID values are not immediately reused after a PGW-U restart, in order to avoid inconsistent TEID allocation throughout the network and to enable the restoration of Sx sessions affected by the failure. How this is ensured is implementation specific.
The PGW-U shall not send Error indication message for a configurable period after an PGW-U restart when the PGW-U receives G-PDU not matching any PDRs.
17.1b.2 Restoration Procedures
During or immediately after an PGW-U Restart, the PGW-U shall place local PGW-U Recovery Time Stamp value in all Heartbeat Request/Response and Sx Association Setup Request/Response Messages.
Immediately after the re-establishment of an Sx association between the PGW-C and the PGW-U, the PGW-C may start restoring Sx sessions in the PGW-U.
NOTE : Restoring Sx sessions in a PGW-U on a reactive basis (like defined for an SGW-U restart in clause 16.1A.4) is not supported in this release. In some cases, a restarted PGW-U cannot determine from the UE IP address the CP function reponsible for an incoming packet for which no session exists, e.g. when a UP function is controlled by multiple CP function for the same APN and when the UE IP address was assigned by the PDN.
17.1A Restart of a peer node
17.1A.1 SGW/ePDG/TWAN Failure
The PGW will receive the SGW/ePDG/TWAN restart counters in GTPv2 echo requests/responses and PMIPv6 heartbeat responses that the PGW receives from the SGW/ePDG/TWAN.
When a PGW detects that a peer ePDG/peer TWAN has restarted it shall delete all PDN connection table data/MM bearer contexts associated with the peer node that fails as well as freeing any internal PGW resources associated with those PDN connections. The PGW may optionally perform other implementation specific actions such as messages to clear other external resources (e.g. PCC messages).
When a PGW detects that a peer SGW has failed with or without restart it shall either:
- proceed as specified above when the PGW detects that a peer ePDG/TWAN fails; or
- follow the procedures specified in clause 27 to restore the PDN connections affected by the SGW failure, if the MME/S4-SGSN and the PGW support these procedures.
NOTE: The PGW will have the identity of SGW/ePDG/TWAN currently in use for a PDN connection available in the PGW's PDN connection table as part of existing EPC procedure.
For multi-access PDN connection in the Network-initiated NBIFOM mode, when the PGW detects ePDG/TWAN has failed, the PGW may:
- maintain the PDN connection on the 3GPP access and notify the PCRF the removal of Non-3GPP access. Then the PCRF can determine to move the affected traffic to the 3GPP access by updating the PCC rules as specified in the clause 5.8 in the 3GPP TS 23.161 [39].
For multi-access PDN connection in the Network-initiated NBIFOM mode, when the PGW detects that the SGW has failed, the PGW may:
- maintain the PDN connection on the Non-3GPP access and notify the PCRF the removal of 3GPP access. Then the PCRF can determine to move the affected traffic to the 3GPP access by updating the PCC rules as specified in the clause 5.8 in the 3GPP TS 23.161 [39], if the SGW restoration procedures as specified in clause 27 are not supported; or,
- follow the SGW restoration procedures specified in clause 27, e.g. maintain the PDN connection on both non-3GPP access and 3GPP access without notify the PCRF about SGW failure, if the SGW restoration procedures are supported.
17.1A.2 PCRF Failure
If the PGW needs to send a request for IP-CAN Session Modification procedure towards a PCRF which is known to have restarted since the IP-CAN session establishment, the PGW may discard the request and may tear down the associated PDN connection, based on operator policy, by initiating a PGW initiated bearer deactivation procedure for the default bearer towards the MME/S4-SGSN with the cause set to "Reactivation requested". This leads the UE to initiate a UE requested PDN connectivity procedure for the same APN. Emergency and eMPS sessions should not be torn down.
NOTE: The procedure above just enables to clean up the PDN connection affected by the PCRF failure when a specific interaction with the PCRF is required. Prior to that interaction, PCC controlled services cannot be provided to the UE.
17.1A.3 PGW-C Failure
The PGW-U will receive the recovery time stamps of the PFCP entity(ies) in the PGW-C in PFCP heartbeat requests/responses.
When a PGW-U detects that a peer PFCP entity in the PGW-C has restarted, the PGW-U shall delete all session contexts affected by the restart that it may have stored.
When a PGW-U detects that a peer PFCP entity in the PGW-C is not reachable for a preconfigured time, the PGW-U shall delete all session contexts affected by the unreachability of the peer PFCP entity in the PGW-C that it may have stored.
17.1A.4 PGW-U Failure
The PGW-C will receive the recovery time stamps of the PFCP entity(ies) in the PGW-U in and PFCP heartbeat requests/responses.
The PGW-C may start restoring Sx sessions in the PGW-U and it may:
- if re-establishment of Sx association is required, immediately re-establish the Sx association between the PGW-C and the PGW-U;
- re-establish Sx sessions affected by the PGW-U failure. .
- when re-establishing a Sx session and if F-TEID allocation is performed in the PGW-U by network configuration, the PGW-C shall include a restoration indication in the PFCP Session Establishment Request message to indicate to the PGW-U it is for a restoration of an existing PFCP session and the PGW-U shall accept PGW-C allocated F-TEID if possible.
NOTE: The PGW-C can determine to re-establish the Sx Association if it receives the cause code "No established PFCP Association" in a response message, or if it detects all peer PFCP entities in the PGW-U have restarted. When a PGW-C detects the failure of a PGW-U without a restart, the PGW-C may select an alternative PGW-U to restore the Sx sessions in the UP function. How this is performed is implementation specific. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.2 Partial Failure Handling at PGW | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.2.1 General | See Clause 23. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.2.2 Procedures during PDN Connection Establishment | If the PGW supports the feature, the following procedures apply.
During a PDN connection establishment, the PGW shall provide one FQ-CSID containing exactly one CSID for that particular PDN connection to the SGW, the ePDG or the TWAN. The PGW shall store the FQ-CSID provided by the SGW and the MME in the PDN Connection table maintained as part of P-GW Context as specified in Table 5.7.3-1 in 3GPP TS 23.401 [15]. Similarly, the PGW shall store the FQ-CSID received from the ePDG or the TWAN.
The PGW should ensure as far as possible that previously used FQ-CSIDs are not immediately reused after a partial/full failure of a PGW.
PGW determines that the partial failure handling does not apply to this PDN connection if it does not receive an SGW FQ-CSID in the S5/S8 Create Session Request (for GTP based interface) or in Proxy Binding Update (for PMIPv6 based interface), or if it does not receive a TWAN FQ-CSID in the S2a Create Session Request (for GTP based S2a) or in Proxy Binding Update (for PMIPv6 based S2a), or if it does not receive an ePDG FQ-CSID in the S2b Create Session Request (for GTP based S2b) or in Proxy Binding Update (for PMIPv6 based S2b). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.2.3 Procedures during PGW Partial Failure | If the PGW supports the feature, the following procedures apply.
When a PGW detects that it has undergone a partial failure, it shall verify that one or more corresponding CSID(s) are present for the component(s) undergoing a partial fault. If there is no such CSID, then the following does not apply. When one or more CSIDs are currently assigned, the PGW shall perform the following:
- The PGW may perform implementation-specific operations to clean up any residual state associated with the CSID(s).
- The PGW shall send the GTPv2 Delete PDN Connection Set Request (or PMIPv6 Binding Revocation Indication with G bit set) message containing all the PGW FQ-CSID(s) of the component(s) failing to the SGW, the TWAN or the ePDG that support the feature.
Upon receiving a GTPv2 Delete PDN Connection Set Response message with Cause value "Success", the PGW shall conclude that the SGW, the ePDG peer or the TWAN peer has initiated the internal deletion of the PDN connections corresponding to the FQ-CSID(s) present in the GTPv2 Delete PDN Connection Set Request message. Similarly, upon receiving a PMIP6 Binding Revocation Acknowledgment message with G bit set, the PGW shall conclude that the SGW, the ePDG or the TWAN has initiated the internal deletion of the PDN connections corresponding to the CSID(s) present in the PMIPv6 Binding Revocation Indication message with G bit set.
The PGW is not required to perform any further recovery actions towards SGW, MME peers, an ePDG peer or a TWAN peer for PDN connections in the connection set identified by the PGW FQ-CSID regardless of the "Cause" value in the response. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.2.4 Procedures during a Peer's Partial Failure | If the PGW supports the feature, the following procedures apply.
When a PGW receives a GTPv2 Delete PDN Connection Set Request (or PMIPv6 Binding Revocation Indication with G bit set) message from an SGW, an ePDG or a TWAN, the PGW shall retrieve all the PDN connections corresponding to each of the FQ-CSIDs present in the message. The PGW shall delete all the retrieved PDN connections and the associated resources. Other implementation-specific actions may be performed.
As a response, the PGW shall send a GTPv2 Delete PDN Connection Set Response message. On PMIPv6-based S5/S8 interface, the PGW shall send a PMIPv6 Binding Revocation Acknowledgment message with G bit set. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 17.2.5 Procedures during PDN Connection Removal or Modification | If the PGW supports the feature, the following procedures apply.
During a S5/S8 procedure, impacting an existing PDN connection Removal or Modification the following apply:
1) If an SGW is being relocated then the PGW shall clear the currently stored MME and SGW FQ‑CSID values.
2) If the SGW includes a SGW FQ-CSID in the S5/S8 Modify Bearer Request (Proxy Binding Update for PMIPv6), or Update PDN Connection Request message, then the PGW shall include PGW FQ-CSID in the S5/S8 Modify Bearer Response (Proxy Binding Acknowledgement for PMIPv6), or Update PDN Connection Response message.
3) If the new SGW does not include a SGW FQ-CSID in the S5/S8 Modify Bearer Request (Proxy Binding Update for PMIPv6), then the new SGW does not support the feature and the feature does not apply for this PDN connection. In such case, PGW shall not include PGW FQ-CSID in the S5/S8 Modify Bearer Response (Proxy Binding Acknowledgement for PMIPv6).
4) If the PGW receives an SGW FQ-CSID and/or an MME FQ-CSID value of a SGW over S5/S8 then the PGW shall overwrite the respective stored FQ-CSID value with the received value.
5) If the PGW receives an Update PDN Connection Request, a Modify Bearer Request or Proxy Binding Update with an SGW FQ-CSID but without an MME FQ-CSID then the PGW shall erase the MME FQ-CSID value (i.e. the current MME does not support the feature).
6) During a S5/S8 procedure removing an existing PDN connection the PGW simply removes the PDN data as well as any stored FQ-CSID values(s) of the MME and SGW or pointers to such data.
During an S2a/S2b procedure, impacting an existing PDN connection Removal or Modification the following apply:
1) If the PGW receives a TWAN or an ePDG FQ-CSID value then the PGW shall overwrite the respective stored FQ-CSID value with the received value;
2) During an S2a/S2b procedure removing an existing PDN connection, the PGW removes the corresponding PDN data as well as any stored FQ-CSID value of the TWAN or the ePDG FQ-CSID.
17A Restoration of data in the MBMS GW
17A.1 Restart of the MBMS GW
When a MBMS GW fails, all its MBMS Bearer contexts affected by the failure become invalid and will be deleted. MBMS GW storage of subscriber data is volatile.
After a MBMS GW restart, all the MBMS Bearer contexts stored in the MBMS GW and affected by the restart become invalid and will be deleted. All the SGmb Diameter sessions affected by the restart are also lost in the MBMS GW.
When the SGSN/MME detects a restart in a MBMS GW (see clause 18 "GTP-C based restart procedures") with which it has MBMS Bearer contexts activated, it shall deactivate all the related MBMS Bearer contexts locally and towards E-UTRAN/UTRAN in which the MBMS bearer service is active. The MME shall initiate a M3AP Reset procedure (see clause 8.5 of 3GPP TS 36.444 [28]), or an MBMS Session Stop procedure per affected MBMS service (see clause 8.3 of 3GPP TS 36.444 [28]), towards the MCE(s) to deactivate the related MBMS services in E-UTRAN. The SGSN shall initiate an MBMS Session Stop procedure per affected MBMS service (see clause 8.38 of 3GPP TS 25.413 [29]), towards the RNC(s) to deactivate the related MBMS services in UTRAN.
If the MBMS GW receives a non-initial message (i.e. MBMS session update or MBMS session stop request) from the BM-SC for which no SGmb Diameter session exists, the MBMW GW shall discard the message and return a Diameter error indication to the originating BM-SC.
In deployments without a Diameter Agent between the BM-SC and the MBMS GW, the BM-SC shall detect a restart in the MBMS GW using either:
- the Diameter Origin-State-Id AVP as specified in the Diameter Base Protocol. To enable fast detection of restart, the Diameter Origin-State-Id AVP shall be included (at least) in Capabilities-Exchange-Request and Capabilities-Exchange-Answer commands; or
- the Diameter Restart-Counter AVP as specified in the MBMS Heartbeat procedure (see clause 29), if this procedure is supported.
In deployments with a Diameter Agent between the BM-SC and the MBMS GW, the BM-SC shall detect a restart in the MBMS GW using the Diameter Restart-Counter AVP as specified in the MBMS Heartbeat procedure (see clause 29).
NOTE 1: The intermediate Diameter Agent can remove or update the Diameter Origin-State-Id AVP, e.g. if it needs to modify the Origin-Host-ID. Thus the Diameter Origin-State-Id AVP, if received by the BM-SC or MBMS GW, does not reflect the state of the remote MBMS peer but the state of the Diameter Agent.
When the BM-SC detects a restart in a MBMS GW with which it has at least one MBMS Bearer context, the BM-SC shall maintain the related MBMS bearer context(s), assume that all related SGmb Diameter session(s) have been terminated and clean-up internal resources associated with these lost session(s). The BM-SC should then re-establish the active MBMS bearer services affected by the MBMS GW restart by initiating MBMS Session Start procedure(s) towards the restarted MBMS GW (or an alternative MBMS GW). The BM-SC shall encode the MBMS Session Start Request with the same contents as in the original MBMS Session Start Request (or per the last MBMS Session Update Request sent by the BM-SC if the original parameters were updated) with the following exceptions:
- the BM-SC shall set the "MBMS session re-establishment indication" flag to signal that this message is used to re-establish an MBMS session;
- if no absolute start time ("MBMS data transfer start" parameter) has been sent, the BM-SC may change the relative start time ("time to MBMS data transfer" parameter) to fasten the restoration of the MBMS service in E-UTRAN;
- the BM-SC should set the estimated session duration to a value corresponding to the remaining duration of the session.
NOTE 2: If the BM-SC is instructed to modify an MBMS Session during the MBMS GW failure/restart, the contents of the MBMS Session Start Request sent to the MBMS GW after the MBMS GW restart can also differ from the parameters sent to the MBMS GW before its restart for the parameters that can be modified by the MBMS session update procedure (i.e. MBMS Session Area, MBMS Time to Data Transfer, MBMS Data Transfer Start).
17A.2 Restart of a peer node
17A.2.1 MME failure
The behaviour of an MBMS GW when it detects that a peer MME has restarted is described in clause 14.1.1.
17A.2.2 SGSN failure
The behaviour of an MBMS GW when it detects that a peer SGSN has restarted is described in clause 11.1.
17A.2.3 BM-SC failure
In deployments without a Diameter Agent between the BM-SC and the MBMS GW, the MBMS GW shall detect a restart in the BM-SC using either:
- the Diameter Origin-State-Id AVP as specified in the Diameter Base Protocol. To enable fast detection of restart, the Diameter Origin-State-Id AVP shall be included (at least) in Capabilities-Exchange-Request and Capabilities-Exchange-Answer commands; or
- the Diameter Restart-Counter AVP as specified in the MBMS Heartbeat procedure (see clause 29), if this procedure is supported.
In deployments with a Diameter Agent between the BM-SC and the MBMS GW, the MBMS GW shall detect a restart in the BM-SC using the Diameter Restart-Counter AVP as specified in the MBMS Heartbeat procedure (see clause 29).
NOTE: The intermediate Diameter Agent can remove or update the Diameter Origin-State-Id AVP, e.g. if it needs to modify the Origin-Host-ID. Thus the Diameter Origin-State-Id AVP, if received by the BM-SC or MBMS GW, does not reflect the state of the remote MBMS peer but the state of the Diameter Agent.
When the MBMS GW detects a restart of the BM-SC with which it has at least one MBMS Bearer context, the MBMS GW shall assume that all related SGmb Diameter session(s) have been terminated and shall deactivate all the related MBMS Bearer contexts locally and towards E-UTRAN/UTRAN in which the MBMS bearer service is active by sending MBMS Session Stop messages to their controlling MME/SGSNs.
17B Restoration of data in the ePDG
17B.1 Restart of the ePDG
17B.1.1 ePDG Failure
When an ePDG fails, all its Bearer contexts/PDN connections affected by the failure become invalid and may be deleted. ePDG storage of subscriber data is volatile.
When the ePDG receives a GTP‑U PDU over GTPv2 based S2b for which no Bearer context exists, it shall discard the GTP‑U PDU and return a GTP error indication to the originating node (i.e. the PGW).
The ePDG should ensure as far as possible that previously used TEID values are not immediately reused after an ePDG restart, in order to avoid inconsistent TEID allocation throughout the network.
When the ePDG receives a user packet with an unknown GRE Key over PMIPv6 based S2b, the ePDG shall discard the packet and optionally response back with an ICMP message, as specified in Clauses 8.2 and 8.3 of IETF RFC2473 [31] for the node unreachable error case.
17B.1.2 Restoration Procedures
After an ePDG restart, the ePDG shall delete all MM Bearer contexts affected by the restart that it may have stored.
During or immediately after an ePDG Restart the ePDG shall place local ePDG restart counter value in all GTPv2 Echo requests/responses messages and PMIPv6 heartbeat responses the ePDG sends to the PGW.
17B.1A Restart of a peer node
17B.1A.1 PGW Failure
The ePDG will receive the PGW restart counter in GTPv2 Echo requests/ responses and PMIPv6 heartbeat responses that the ePDG receives from the PGW.
When an ePDG detects that a peer PGW has restarted (see clause 18 "GTP-C based restart procedures" and clause 19 "PMIPv6 based restart procedures") it shall delete all PDN connection table data/MM bearer contexts associated with the peer node that fails, free any internal ePDG resources associated with those PDN connections and initiate the release of the corresponding SWu instances (i.e. IKEv2 tunnels).
17B.2 Partial Failure Handling at ePDG
17B.2.1 General
See clause 23.
The partial failure feature is optional for ePDG.
If the ePDG does not support the feature then partial failure handling does not apply to that specific PDN connection.
17B.2.2 Procedures during PDN Connection Establishment
If the ePDG supports the feature, the following procedures apply.
During a PDN connection establishment, the ePDG shall provide one ePDG FQ-CSID containing exactly one CSID for that particular PDN connection to the PGW. The ePDG shall store the Node-ID and CSID from the FQ-CSID provided by the PGW for that particular PDN connection in its PDN Connection table.
The ePDG determines that the PGW supports partial failure handling by the presence of the PGW FQ-CSID in the Create Session Response for GTPv2 based S2b and/or Proxy Binding Acknowledgement message for PMIPv6 based S2b.
17B.2.3 Procedures during ePDG Partial Failure
If the ePDG supports the feature, the following procedures apply.
When an ePDG detects that it has undergone a partial failure, it shall verify that one or more corresponding CSID(s) are present for the component undergoing a partial fault. If there is no such CSID, then the following does not apply. When one or more CSIDs are currently assigned, the ePDG shall perform the following.
The ePDG may perform implementation-specific operations to clean up any residual state associated with the CSID(s).
The ePDG shall send Delete PDN Connection Set Request containing all the ePDG CSIDs of the component(s) failing in ePDG FQ-CSID over the GTPv2 based S2b interface or PMIPv6 Binding Revocation Indication with G bit set message containing the equivalent ePDG FQ-CSID(s) over the PMIPv6 based S2b interface to PGW peers supporting the feature.
On the GTPv2 based S2b interface, upon receiving a GTPv2 Delete PDN Connection Set Response message with Cause value "Success", the ePDG shall conclude that the PGW has initiated the internal deletion of the PDN connections corresponding to the FQ-CSID(s) present in the GTPv2 Delete PDN Connection Set Request message. Similarly, on the PMIPv6 based S2b interface, upon receiving a successful PMIP6 Binding Revocation Acknowledgment message with G bit set, the ePDG shall conclude that the PGW has initiated the internal deletion of the PDN connections corresponding to the CSID(s) present in the PMIP6 Binding Revocation Indication message.
The ePDG is not required to perform any further recovery actions towards PGW peers for PDN connections in the connection set identified by the PGW FQ-CSID(s).
17B.2.4 Procedures during PGW Partial Failure
If the ePDG supports the feature, the following procedures apply.
When an ePDG receives a GTPv2 Delete PDN Connection Set Request or PMIP6 Binding Revocation Indication with G bit set message from a PGW, the ePDG shall retrieve all the PDN connections corresponding to each of the FQ-CSID(s) present in the message. The ePDG shall delete all the retrieved PDN connections, free the associated internal resources and initiate the release of the corresponding SWu instances (i.e. IKEv2 tunnels). Other implementation-specific actions may be performed.
As a response, the ePDG shall send a GTPv2 Delete PDN Connection Set Response message with an appropriate Cause value or a PMIPv6 Binding Revocation Acknowledgment message with G bit set to the PGW.
17B.2.5 Procedures during PDN Connection Removal or Modification
For the modification of an existing PDN connection established over 2b, if the corresponding ePDG and PGW support the partial failure feature, when the ePDG receives an FQ-CSID value of a PGW over S2b, the ePDG shall overwrite the currently stored FQ CSID value with the received value.
For the removal of an existing PDN connection established over S2b, if the corresponding ePDG and PGW support the partial failure feature, an ePDG removes the corresponding PDN data as well as any relevant stored FQ-CSID value of the PGW FQ-CSID.
17C Restoration of data in the TWAN
17C.1 Restart of the TWAN
17C.1.1 TWAN Failure
When a TWAN fails, all its Bearer contexts/PDN connections affected by the failure become invalid and may be deleted. TWAN storage of subscriber data is volatile.
When the TWAN receives a GTP‑U PDU over GTPv2 based S2a for which no Bearer context exists, it shall discard the GTP‑U PDU and return a GTP error indication to the originating node (i.e. the PGW).
The TWAN should ensure as far as possible that previously used TEID values are not immediately reused after a TWAN restart, in order to avoid inconsistent TEID allocation throughout the network.
When the TWAN receives a user packet with an unknown GRE Key over PMIPv6 based S2a, the TWAN shall discard the packet and optionally respond back with an ICMP message, as specified in Clauses 8.2 and 8.3 of IETF RFC2473 [31] for the node unreachable error case.
17C.1.2 Restoration Procedures
After a TWAN restart, the TWAN shall delete all Bearer contexts affected by the restart that it may have stored and place local TWAN restart counter value in all GTPv2 Echo requests/responses messages and PMIPv6 heartbeat responses the TWAN sends to the PGW.
17C.1A Restart of a peer node
17C.1A.1 PGW Failure
The TWAN will receive the PGW restart counter in GTPv2 Echo requests/ responses and PMIPv6 heartbeat responses that the TWAN receives from the PGW.
When a TWAN detects that a peer PGW has restarted (see clause 18 "GTP-C based restart procedures" and clause 19 "PMIPv6 based restart procedures") it shall delete all PDN connection table data/bearer contexts associated with the peer node that fails, and may free the associated internal TWAN resources.
17C.2 Partial Failure Handling at TWAN
17C.2.1 General
See clause 23.
The partial failure feature is optional for TWAN.
If the TWAN does not support the feature then partial failure handling does not apply to that specific PDN connection.
17C.2.2 Procedures during PDN Connection Establishment
If the TWAN supports the feature, the following procedures apply.
During a PDN connection establishment, the TWAN shall provide one TWAN FQ-CSID containing exactly one CSID for that particular PDN connection to the PGW. The TWAN shall store the Node-ID and CSID from the FQ-CSID provided by the PGW for that particular PDN connection in its PDN Connection table.
The TWAN determines that the PGW supports partial failure handling by the presence of the PGW FQ-CSID in the Create Session Response for GTPv2 based S2a and/or Proxy Binding Acknowledgement message for PMIPv6 based S2a.
17C.2.3 Procedures during TWAN Partial Failure
If the TWAN supports the feature, the following procedures apply.
When a TWAN detects that it has undergone a partial failure, it shall verify that one or more corresponding CSID(s) are present for the component undergoing a partial fault. If there is no such CSID, then the following does not apply. When one or more CSIDs are currently assigned, the TWAN shall perform the following.
The TWAN may perform implementation-specific operations to clean up any residual state associated with the CSID(s).
The TWAN shall send Delete PDN Connection Set Request containing all the TWAN CSIDs of the component(s) failing in TWAN FQ-CSID over the GTPv2 based S2a interface or PMIPv6 Binding Revocation Indication with G bit set message containing the equivalent TWAN FQ-CSID(s) over the PMIPv6 based S2a interface to PGW peers supporting the feature.
On the GTPv2 based S2a interface, upon receiving a GTPv2 Delete PDN Connection Set Response message with Cause value "Success", the TWAN shall conclude that the PGW has initiated the internal deletion of the PDN connections corresponding to the FQ-CSID(s) present in the GTPv2 Delete PDN Connection Set Request message. Similarly, on the PMIPv6 based S2a interface, upon receiving a successful PMIPv6 Binding Revocation Acknowledgment message with G bit set, the TWAN shall conclude that the PGW has initiated the internal deletion of the PDN connections corresponding to the CSID(s) present in the PMIPv6 Binding Revocation Indication message.
The TWAN is not required to perform any further recovery actions towards PGW peers for PDN connections in the connection set identified by the PGW FQ-CSID(s).
17C.2.4 Procedures during PGW Partial Failure
If the TWAN supports the feature, the following procedures apply.
When an TWAN receives a GTPv2 Delete PDN Connection Set Request or PMIP6 Binding Revocation Indication with G bit set message from a PGW, the TWAN shall retrieve all the PDN connections corresponding to each of the FQ-CSID(s) present in the message. The TWAN shall delete all the retrieved PDN connections, and may free the associated internal TWAN resources.
As a response, the TWAN shall send a GTPv2 Delete PDN Connection Set Response message with an appropriate Cause value or a PMIPv6 Binding Revocation Acknowledgment message with G bit set to the PGW.
17C.2.5 Procedures during PDN Connection Removal or Modification
For the modification of an existing PDN connection established over S2a, if the corresponding TWAN and PGW support the partial failure feature, when the TWAN receives an FQ-CSID value of a PGW over S2a, the TWAN shall overwrite the currently stored FQ CSID value with the received value.
For the removal of an existing PDN connection established over S2a, if the corresponding TWAN and PGW support the partial failure feature, a TWAN removes the corresponding PDN data as well as any relevant stored FQ-CSID value of the PGW FQ-CSID.
17D Restoration of data in the BM-SC
17D.1 Restart of the BM-SC
When a BM-SC fails, all its MBMS Bearer contexts affected by the failure become invalid and will be deleted.
After a BM-SC restart, all the MBMS Bearer contexts stored in the BM-SC and affected by the restart become invalid and will be deleted. All the SGmb Diameter sessions affected by the restart are also lost in the BM-SC. If Group Communication Service (GCS) is supported, the BM-SC also loses the knowledge of the TMGIs it had allocated to the Group Communication Service Application Server(s) (GCS AS) before restarting.
When the MBMS GW detects the restart of a BM-SC, it shall behave as described in clause 17A.2.3.
When the GCS AS detects the restart of a BM-SC, it shall behave as described in clause 17E.1. The restoration of MBMS services by content providers other than GCS AS after a BM-SC failure or restart is out of scope of 3GPP.
NOTE: The reference point from content providers other than GCS AS to the BM-SC is not standardised by 3GPP.
17D.2 Restart of the GCS AS
In deployments without a Diameter Agent between the GCS AS and the BM-SC, the BM-SC shall detect a restart in the GCS AS using either:
- the Diameter Origin-State-Id AVP as specified in the Diameter Base Protocol. To enable fast detection of restart, the Diameter Origin-State-Id AVP shall be included (at least) in Capabilities-Exchange-Request and Capabilities-Exchange-Answer commands; or
- the Diameter Restart-Counter AVP as specified in the MBMS Heartbeat procedure (see clause 29), if this procedure is supported.
In deployments with a Diameter Agent between the GCS AS and the BM-SC, the BM-SC shall detect a restart in the GCS AS using the Diameter Restart-Counter AVP as specified in the MBMS Heartbeat procedure (see clause 29).
NOTE: The intermediate Diameter Agent can remove or update the Diameter Origin-State-Id AVP, e.g. if it needs to modify the Origin-Host-ID. Thus the Diameter Origin-State-Id AVP, if received by the BM-SC or GCS AS, does not reflect the state of the remote MBMS peer but the state of the Diameter Agent.
When the BM-SC detects a restart of the GCS AS, the BM-SC shall deallocate (locally) all the TMGIs that had been assigned to the restarted GCS AS and the BM-SC shall stop all the related MBMS bearers to free the corresponding resources in E-UTRAN.
17E Restoration of data in the GCS AS
17E.1 Restart of the GCS-AS
After a GCS AS restart, the GCS AS loses its MBMS bearer contexts and the knowledge of the TMGIs it had been allocated by the BM-SC(s) before restarting.
When the BM-SC detects the restart of a GCS AS, it shall behave as described in clause 17D.2.
17E.2 Restart of the BM-SC
In deployments without a Diameter Agent between the GCS AS and the BM-SC, the GCS AS shall detect a restart in the BM-SC using either:
- the Diameter Origin-State-Id AVP as specified in the Diameter Base Protocol. To enable fast detection of restart, the Diameter Origin-State-Id AVP shall be included (at least) in Capabilities-Exchange-Request and Capabilities-Exchange-Answer commands; or
- the Diameter Restart-Counter AVP as specified in the MBMS Heartbeat procedure (see clause 29), if this procedure is supported.
In deployments with a Diameter Agent between the GCS AS and the BM-SC, the GCS AS shall detect a restart in the BM-SC using the Diameter Restart-Counter AVP as specified in the MBMS Heartbeat procedure (see clause 29).
NOTE: The intermediate Diameter Agent can remove or update the Diameter Origin-State-Id AVP, e.g. if it needs to modify the Origin-Host-ID. Thus the Diameter Origin-State-Id AVP, if received by the BM-SC or GCS AS, does not reflect the state of the remote MBMS peer but the state of the Diameter Agent.
When the GCS AS detects a restart of the BM-SC, the GCS AS shall assume that all the TMGIs that had been assigned by the restarted BM-SC have been de-allocated and that all the related MBMS bearers have been deactivated.
The GCS AS may restore the MBMS delivery using the MB2-C procedures specified in 3GPP TS 29.468 [35].
17F Restoration of data in the UCMF
17F.1 Restart of the UCMF
The UCMF is assumed as a front-end application function with a persistent database connected. The UCMF may restart but all dictionary mapping information between UE Radio Capability and UE Radio Capability IDs can be retained, hence, in this case, a UCMF shall not update its Recovery Time Stamp if the UCMF has restarted.
Editor' Note: The handling of Version ID within PLMN assigned UE Radio Capability IDs at UCMF Restart is ffs.
17F.2 Restart of the MME
When a UCMF detects that a peer MME has failed with or without restart (relying on restart counter as specified in clause 19B "URCMP based restart procedures" or implementation e.g. a preconfigured path failure timer as specified in clause 20 "Path management procedures"), it shall delete the subscription created by the failed MME. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 18 GTP-C based restart procedures | Across GTP-C based interfaces an SGSN, GGSN, MME, SGW, PGW, TWAN, ePDG and HRPD Access Node utilize either GTPv1-C or GTPv2-C Echo Request and Echo Response messages or GTP-C messages containing the Recovery Information Element to detect and handle a restart.
A GTP-C entity shall maintain two Restart counters:
- in volatile memory a remote Restart counter of a peer with which the entity is in contact;
- in non-volatile memory own, or local Restart counter that was sent to a peer.
After a GTP-C entity has restarted, it shall immediately increment all local Restart counters and shall clear all remote Restart counters.
A GTP-C entity may have a common local Restart counter for all peers, or it may have a separate local Restart counter for each peer.
A GTP-C entity may probe the liveliness of each peer with which it is in contact by sending an Echo Request message (see clause 20 "Path management procedures") . The presence of the Restart counter in Echo Request or in a GTP-C message depends on the GTP-C version and therefore is specified in 3GPP TS 29.060 [8] and 3GPP TS 29.274 [13], respectively. The restart counter signalled in the GTP-C message is associated with the GTP-C entity identified by the sender's F-TEID or SGSN/GGSN IP address for control plane if present in the message, otherwise (e.g. in echo request message) it is associated with the GTP-C entity identified by the source IP address of the message.
The GTP-C entity that receives a Recovery Information Element in an Echo Response or in another GTP-C message from a peer, shall compare the received remote Restart counter value with the previous Restart counter value stored for that peer entity.
- If no previous value was stored the Restart counter value received in the Echo Response or in the GTP-C message shall be stored for the peer.
- If the value of a Restart counter previously stored for a peer is smaller than the Restart counter value received in the Echo Response message or the GTP-C message, taking the integer roll-over into account, this indicates that the entity that sent the Echo Response or the GTP-C message has restarted. The received, new Restart counter value shall be stored by the receiving entity, replacing the value previously stored for the peer.
- If the value of a Restart counter previously stored for a peer is larger than the Restart counter value received in the Echo Response message or the GTP-C message, taking the integer roll-over into account, this indicates a possible race condition (newer message arriving before the older one). The received new Restart counter value shall be discarded and an error may be logged.
Based on operator's policy, when a Recovery IE is received in an Echo Request or in any incoming GTP-C request message (which includes a Recovery IE) from a peer GTP-C entity, with a Restart counter value larger than the value of the Restart counter previously stored for the peer GTP-C entity, the GTP-C entity may verify whether the peer GTP-C entity has really restarted by:
- sending one or more Echo Request message(s) towards the peer GTP-C entity, or by monitoring other GTP-C request messages it may have sent for any PDN connections (e.g. Update Bearer Request message) towards the peer GTP-C entity; and
- determining that the peer GTP-C entity has restarted if the value of the restart counter received in the Recovery IE in the Echo Response message or in the corresponding GTP-C response messages (e.g. Update Bearer Response) is larger than the value of the Restart counter previously stored for the peer GTP-C entity.
NOTE: This can be used e.g. when two GTP-C entities are connected via a roaming interface and Network Domain Security (e.g. IPsec ESP) is not applied or may not provide sufficient protection of the GTP-C signalling, e.g. against IP address spoofing.
18A GTP-U based restart procedure
The support of GTP-U based restart procedure is optional for a GTP-U entity.
When the feature is supported, across GTP-U based interfaces, i.e. the S1-U, S11-U, S2a, S2b, X2, S4, S5, S8, S12, M1 and Sn interfaces of the Evolved Packet System in EPS, and the F1-U, Xn, N3, N9, N19, N3mb and N19mb interfaces of the 5G System in 5GS, a GTP-U entity shall utilize GTP-U Echo Request, Echo Response messages and GTP-U Error Indication message containing the Recovery Time Stamp Information Element to detect and handle a restart.
A GTP-U entity shall be prepared to receive an Echo Request message at any time (even from unknown peers), and it shall reply with an Echo Response message.
A GTP-U entity shall maintain two Recovery Time Stamps:
- in volatile memory a remote Recovery Time Stamp of a peer GTP-U entity with which the entity is in contact;
- in non-volatile memory own, or local Recovery Time Stamp that was sent to a peer GTP-U entity.
After a GTP-U entity has (re)started and all its GTP-U contexts have been lost, and if the GTP-U entity knows these GTP-U contexts are not to be restored, e.g., by its Control Plane function, it shall immediately update all local Recovery Time Stamps and shall clear all remote Recovery Time Stamps. When peer GTP-U entities information is available, e.g. when the first GTP-U tunnel towards the peer GTP-U entity is established, the (re)started GTP-U entity may send its (updated) Recovery Time Stamps in an Echo Request message to the peer GTP-U entity before sending GTP-U packets.
NOTE: The GTP-U entity needs to be configured to know if the GTP-U contexts can be restored or not. It is implemention specific how to handle the scenario that the GTP-U entity interworks with some control plane nodes supporting restoration of GTP-U contexts while others not supporting, for example, it can use different IP addresses.
A GTP-U entity may have a common local Recovery Time Stamp for all peer GTP-U entities, or it may have a separate local Recovery Time Stamp for each peer GTP-U entity.
A GTP-U entity may probe the liveliness of each peer GTP-U entity with which it is in contact by sending an Echo Request message.
The Recovery Time Stamp signalled in the GTP-U Echo Request and Response messages is associated with the GTP-U entity identified by the source IP address of the message.
The Recovery Time Stamp signalled in the GTP-U Error Indication is associated with the source IP address of the GTP-U Error Indication or associated with a list of IP address(es) which are sharing the same Recovery Time Stamp if those IP address(es) are explicitly included in the GTP-U Error Indication message.
The GTP-U entity that receives a Recovery Time Stamp Information Element from a peer GTP-U entity shall compare the received remote Recovery Time Stamp value with the previous Recovery Time Stamp value stored for that peer GTP-U entity.
- If no previous value was stored, the Recovery Time Stamp value received in the Echo Request or Response messages or the GTP Error Indication message shall be stored for the peer GTP-U entity.
- If the value of a Recovery Time Stamp previously stored for a peer GTP-U entity is smaller than the Recovery Time Stamp received in the Echo Request or Response messages or the GTP-U Error Indication messages, this indicates that the entity that sent the Echo Request or Response messages or the GTP-U Error Indication messages has restarted. The received, new Recovery Time Stamp value shall be stored by the receiving entity, replacing the value previously stored for the peer GTP-U entity.
- If the value of a Recovery Time Stamp previously stored for a peer GTP-U entity is larger than the Recovery Time Stamp value received in the Echo Request or Response messages or the GTP-U Error Indication messages, this indicates a possible race condition (newer message arriving before the older one). The received new Recovery Time Stamp value shall be discarded and an error may be logged.
Based on operator's policy, when a Recovery Time Stamp IE is received in an Echo Request from a peer GTP-U entity, with a Recovery Time Stamp larger than the value of the Recovery Time Stamp previously stored for the peer GTP-U entity, the GTP-U entity may verify whether the peer GTP-U entity has really restarted by:
- sending one or more Echo Request message(s) towards the peer GTP-U entity; and
- determining that the peer GTP-U entity has restarted if the Recovery Time Stamp in the Echo Response message is larger than the value of the Recovery Time Stamp previously stored for the peer GTP-U entity. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 19 PMIPv6 based restart procedures | Across PMIPv6 based interfaces, SGW, PGW, TWAN and ePDG utilize PMIPv6 Heartbeat mechanism for node restart detection as specified in 3GPP TS 29.275 [16].
A PMIPv6 entity shall maintain two restart counters:
- in volatile memory a remote restart counter of a peer with which the entity is in contact;
- in non-volatile memory an own, or local restart counter that was sent to a peer.
After a PMIPv6 entity has restarted, it shall immediately increment all local restart counters and shall clear all remote restart counters.
A PMIPv6 entity may have a common local restart counter for all peers, or it may have a separate local restart counter for each peer.
19A PFCP based restart procedures
Across PFCP based interfaces, an SGW-C, SGW-U, PGW-C and PGW-U Node shall utilize PFCP Heartbeat Request and Heartbeat Response messages to detect and handle a peer PFCP entity failure or restart. A PFCP entity shall be prepared to receive a Heartbeat Request message at any time (even from unknown peers), and it shall reply with a Heartbeat Response message.
A PFCP entity shall maintain two Recovery Time Stamps:
- in volatile memory a remote Recovery Time Stamp of a peer PFCP entity with which the entity is in contact;
- in non-volatile memory own, or local Recovery Time Stamp that was sent to a peer PFCP entity.
After a PFCP entity has restarted, it shall immediately update all local Recovery Time Stamps and shall clear all remote Recovery Time Stamps. When peer PFCP entities information is available, i.e. when the PFCP Association is still alive, the restarted PFCP entity shall send its updated Recovery Time Stamps in a Heartbeat Request message to the peer PFCP entities before initiating any PFCP session signalling.
A PFCP entity may have a common local Recovery Time Stamp for all peer PFCP entities, or it may have a separate local Recovery Time Stamp for each peer PFCP entity.
A PFCP entity may probe the liveliness of each peer PFCP entity with which it is in contact by sending a Heartbeat Request message (see clause 20 "Path management procedures").
The Recovery Time Stamp signalled in the PFCP Heartbeat Request and Response messages is associated with the PFCP entity identified by the source IP address of the message.
The Recovery Time Stamp signalled in the PFCP Session Establishment Request messages is associated with the IP address in the CP F-SEID IE.
The PFCP entity that receives a Recovery Time Stamp Information Element from a peer PFCP entity shall compare the received remote Recovery Time Stamp value with the previous Recovery Time Stamp value stored for that peer PFCP entity.
- If no previous value was stored, the Recovery Time Stamp value received in the Heartbeat Request or Response messages or the PFCP Session Establishment Request messages shall be stored for the peer PFCP entity.
- If the value of a Recovery Time Stamp previously stored for a peer PFCP entity is smaller than the Recovery Time Stamp value received in the Heartbeat Request or Response messages or the PFCP Session Establishment Request messages, this indicates that the entity that sent the Heartbeat Request or Response messages has restarted. The received, new Recovery Time Stamp value shall be stored by the receiving entity, replacing the value previously stored for the peer PFCP entity.
- If the value of a Recovery Time Stamp previously stored for a peer PFCP entity is larger than the Recovery Time Stamp value received in the Heartbeat Request or Response message or the PFCP Session Establishment Request messages, this indicates a possible race condition (newer message arriving before the older one). The received Sx node related message and the received new Recovery Time Stamp value shall be discarded and an error may be logged.
A PFCP function shall ignore the Recovery Timestamp received in PFCP Association Setup Request and PFCP Association Setup Response messages (see clause 6.2.6 of 3GPP TS 29.244 [43]).
When a NAT device is deployed between PFCP entities, e.g. between the CP function and UP function, the following requirements shall apply in addition to the above requirements:
- the Heartbeat Request message may include a Source IP Address IE;
- when the Source IP Address IE is present, the Recovery Time Stamp signalled in the Heartbeat Request message shall be associated with the Source IP Address IE, instead of the source IP address of the message.
19B URCMP based restart procedures
Across URCMP based interfaces, an MME and UCMF Node shall utilize URCMP Heartbeat Request and Heartbeat Response messages to detect and handle a peer URCMP entity failure or restart. A URCMP entity shall be prepared to receive a Heartbeat Request message at any time (even from unknown peers), and it shall reply with a Heartbeat Response message.
A URCMP entity shall maintain two Recovery Time Stamps:
- in volatile memory a remote Recovery Time Stamp of a peer URCMP entity with which the entity is in contact;
- in non-volatile memory own, or local Recovery Time Stamp that was sent to a peer URCMP entity.
After a URCMP entity has restarted and if it loses all dictionary mapping information between UE Radio Capability Information and UE Radio Capability IDs, it shall immediately update all local Recovery Time Stamps and shall clear all remote Recovery Time Stamps.
A URCMP entity may have a common local Recovery Time Stamp for all peer URCMP entities, or it may have a separate local Recovery Time Stamp for each peer URCMP entity.
A URCMP entity may probe the liveliness of each peer URCMP entity with which it is in contact by sending a Heartbeat Request message (see clause 20 "Path management procedures").
The Recovery Time Stamp signalled in the URCMP Heartbeat Request and Response messages is associated with the URCMP entity identified by the source IP address of the message.
The URCMP entity that receives a Recovery Time Stamp Information Element from a peer URCMP entity shall compare the received remote Recovery Time Stamp value with the previous Recovery Time Stamp value stored for that peer URCMP entity.
- If no previous value was stored, the Recovery Time Stamp value received in the Heartbeat Request or Response messages shall be stored for the peer URCMP entity.
- If the value of a Recovery Time Stamp previously stored for a peer URCMP entity is smaller than the Recovery Time Stamp value received in the Heartbeat Request or Response messages, this indicates that the entity that sent the Heartbeat Request or Response messages has restarted. The received, new Recovery Time Stamp value shall be stored by the receiving entity, replacing the value previously stored for the peer URCMP entity.
- If the value of a Recovery Time Stamp previously stored for a peer URCMP entity is larger than the Recovery Time Stamp value received in the Heartbeat Request or Response message, this indicates a possible race condition (newer message arriving before the older one). The received Sx node related message and the received new Recovery Time Stamp value shall be discarded and an error may be logged. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20 Path management procedures | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.1 General | This clause specifies path management procedures for GTP-C based, PMIP and PFCP based interfaces.
For GTP based interfaces, Echo Request / Response procedure is used. The usage depends on the GTP-C version in the following way:
- GTPv1-C entity may periodically send an Echo Request message as specified in 3GPP TS 29.060 [8].
- GTPv2 entity shall probe the liveliness of each peer with which it is in contact by sending an Echo Request messages (see TS 29.274 [13]). When and how often a GTPv2 Echo Request message may be sent is implementation specific but an Echo Request shall not be sent more often than every 60 s on each path. This does not prevent resending an Echo Request with the same sequence number according to the T3-RESPONSE timer.
It is recommended that GTPv2 Echo Request should be sent only when a GTP-C entity has not received any GTP response message for a previously sent request message on the GTP-C path for, an implementation dependent period of time.
A GTP-C entity (both GTPv1-C and GTPv2) shall be prepared to receive an Echo Request message at any time and it shall reply with an Echo Response message.
For the PMIP based S5/S8 interface, the SGW and PGW shall detect respectively a peer PGW and SGW as currently unavailable by sending a series of PMIPv6 Heartbeat Request messages, and not receiving within a period of time respectively a PMIPv6 Heartbeat Response message (see 3GPP TS 29.275 [16]).
For PFCP based Sxa/Sxb/Sxc interfaces, the CP function shall detect a peer UP function (or vice versa) as currently unavailable by sending a series of PFCP heartbeat Request messages, and not receiving within a period of time respectively a PFCP Heartbeat Response message (see 3GPP TS 29.244 [43]).
For URCMP based S17 interface, the URCMP entity shall detect a peer URCMP entity as currently unavailable by sending a series of URCMP heartbeat Request messages, and not receiving within a period of time respectively a URCMP Heartbeat Response message (see 3GPP TS 29.674 [44]). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2 Signalling path failure detection and handling | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.1 General | GTP-C entities shall support detection of path failure by using Echo Request / Echo Response messages in the following way. A peer's IP address specific counter shall be reset each time an Echo Response message is received from that peer's IP address and incremented when the T3-RESPONSE timer expires for an Echo Request message sent to that peer's IP address. The path shall be considered to be down if the counter exceeds N3-REQUESTS.
PMIP entities shall support detection of path failure as specified for Failure Detection in IETF RFC 5847 [22].
Upon detecting a path failure, the network node should notify the failure via the Operation and Maintenance system and may either:
- delete the PDN connections (EPS bearer contexts) or PDP contexts associated with this peer's IP address; or
- maintain the PDN connections (EPS bearer contexts) or PDP contexts associated with the peer's IP address during an operator configurable maximum path failure duration. The network node shall delete the maintained resources if the path is still down when this duration expires. The network node may delete the maintained resources if control/user plane signalling is received across other interface(s) during the path failure and before the maximum path failure duration timer expires.
NOTE 1: During transient path failures (e.g. path failures not exceeding few minutes at most), maintaining the EPS bearer contexts or PDP contexts associated with the peer's IP address enables the delivery of end user services (when the path is reestablished again) and also avoids unnecessary signalling in the network for restoring those connections.
NOTE 2: It is not intended to maintain PDN connections during long path failures (e.g. exceeding few minutes at most) as this would imply undesirable effects like undue charging.
The following clauses specify further specific network element requirements. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.2 SGW functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.2.1 S11/S4 path failure | It is optional for the SGW to maintain the S5/S8 bearer contexts when the SGW detects a path failure to the MME/S4-SGSN (see clause 20.2.1). However upon detecting a path failure to the MME/S4-SGSN, an SGW that supports the network triggered service restoration procedure (see clause 25) should maintain the S5/S8 bearer contexts eligible for network initiated service restoration and proceed with the network triggered service restoration procedure with the following modification:
- if the path to the MME/S4-SGSN is down for a duration exceeding the maximum path failure duration and if there is no alternative reachable path, e.g. another MME/S4-SGSN in the same pool or another control plane IP address belonging to the same MME/S4-SGSN, the SGW should locally delete the maintained PDN connections associated with the failed path.
In addition, for UEs in connected state associated with the failed path, the SGW should continue sending downlink packets to the eNodeB/RNC as long as the impacted PDN connections are maintained, regardless of whether the SGW supports the network triggered service restoration procedure or not. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.2.2 S5 path failure | The SGW may support the PGW triggered SGW restoration for an S5 path failure. If so, then the SGW should support the PGW Restart Notification procedure. After detecting a path failure to the PGW, the SGW may delete all the PDN connections affected by the path failure and should also send a PGW Restart Notification message to the MME or S4-SGSN if the the PGW Restart Notification procedure is supported by the SGW and MME/S4-SGSN (see clause 16.1A.2).
NOTE: The PGW Restart Notification procedure can help the MME to restore the PDN connections earlier since the SGW will detect the S5 path failure and send PGW Restart Notification triggering a PDN connection restoration at the MME, before the PGW sends the PGW Downlink Triggering Notification.
The SGW should proceed with the PGW triggered SGW restoration procedure (see clause 27.2.3.3) with the following modification:
- The SGW shall include the PGW F-TEID or PGW IP address and GRE key for control plane in the PGW Downlink Triggering Notification message that it sends to the MME/S4-SGSN, if this information is present in the PGW Downlink Triggering Notification/PMIP Update Notification message received from the PGW. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.3 MBMS GW functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.3.1 Sm path failure | The MBMS GW may be provisioned with the list (or a sublist) of the MMEs pertaining to the MME pool.
NOTE 1: The MBMS GW expects only one MME of the MME pool in BM-SC requests received across the SGmb interface.
Upon detecting an Sm path failure, the MBMS GW should maintain the MBMS bearer contexts associated with the peer's MME IP address.
During a transient Sm path failure (e.g. before the maximum path failure duration timer expires), the MBMS GW may process MBMS requests from the BM-SC and intended for the MME for which the Sm path has failed as follows:
- for new MBMS Session Start Request, the MBMS GW may select an alternative MME in the same MME pool and send the MBMS Session Start Request to this alternative MME;
- for MBMS Session Update Request or MBMS Session Stop Request, the MBMS GW may select an alternative MME in the same MME pool, send a MBMS Session Start Request message to this alternative MME and, if successful, send subsequently the MBMS Session Update Request or MBMS Session Stop Request to this alternative MME.
After having selected an alternative MME, the MBMS GW shall consider the MME answering to the MBMS Start Request as the controlling MME for the MBMS session and send any subsequent MBMS Session Update or MBMS Session Stop for this MBMS Session to this MME.
NOTE 2: Each MME of the MME pool provisioned in the MBMS GW supports an M3 interface with the MCE(s).
When detecting a non-transient Sm path failure at the MBMS GW (e.g. the maximum path failure duration timer of the MBMS GW expires), the MBMS GW may move the control of all the affected active MBMS sessions to another MME in the same MME pool (if any other MME is reachable by the MBMS GW) by initiating new MBMS Session Start Request(s) to alternative MME(s).
NOTE 3: This allows to re-establish the MBMS sessions when a MME fails without restart.
The maximum path failure duration timer of the MBMS GW should be configured with a shorter value than the maximum path failure duration timer of the MME to avoid interrupting active MBMS sessions upon a non-transient Sm path failure. The MBMS GW timer should be shorter than the MME timer by at least the period between two Echo Request messages sent by the MME, to avoid that the MME timer expires before the MBMS GW timer if the MME starts its timer before the MBMS GW.
NOTE 4: This enables the MCE to receive a MBMS Session Start request from the new MME controlling the MBMS session before the MCE receives a request to stop the MBMS service from the previous controlling MME.
When sending an MBMS Session Start Request sent to an alternative MME, the MBMS GW shall encode the contents of the request with the same contents as in the original MBMS Session Start Request (or per the last MBMS Session Update Request sent by the MBMS GW if the original parameters were updated) with the following exceptions:
- the MBMS GW shall set the "MBMS session re-establishment indication" flag to signal that this message is used to re-establish an MBMS session;
- if no absolute start time ("MBMS data transfer start" parameter) has been received, the MBMS GW may change the relative start time ("time to MBMS data transfer" parameter) to fasten the restoration of the MBMS service in E-UTRAN;
- the MBMS GW should set the estimated session duration to a value corresponding to the remaining duration of the session.
NOTE 5: Per the requirements above, if the MBMS GW had started an MBMS session within an MME with the MBMS Service Area (1, 2, 3) and receives during an Sm path failure (towards this MME) an MBMS Session Update from the BM-SC modifying the MBMS Service Area to (3, 4, 5), the MBMS GW will encode the original MBMS Service Area (1, 2, 3) in the MBMS Session Start Request sent to the alternative MME and subsequently send an MBMS Session Update Request with the MBMS Service Area (3,4,5) to the new MME controlling the MBMS session.
NOTE 6: If the previous MME received an MBMS Session Update Request from the MBMS GW but could not propagate it to the MCE due to a M3AP path failure, the contents of the MBMS Session Start Request sent to the MCE via the new MME can also differ from the parameters sent to the MCE via the previous MME for the parameters that can be modified by the MBMS session update procedure (i.e. MBMS Session Area, MBMS Time to Data Transfer, MBMS Data Transfer Start).
After detecting an Sm path failure, the MBMS GW shall determine whether the failure is transient or non transient from the perpective of the MME (e.g. the MBMS GW is provisioned with the maximum path failure timer of the MME). The MBMS GW shall assume that the failure is non transient from the perspective of the MME if the Sm path recovers after a period longer than the maximum path failure timer of the MME plus the period between two Echo Request messages sent by the MME, to ensure that the MME also determines this is a non transient path failure if the MBMS GW starts its timer before the MME. The MBMS GW shall consider that the MBMS session has been released by the MME if the Sm path failure is non transient for the MME. If the Sm path failure remains transient for the MME, the MBMS GW shall behave as follows upon detecting the Sm path recovery:
- if the MBMS GW has already moved the control of the MBMS session to an alternative MME(s), the MBMS GW shall send an MBMS Session Stop Request message to the MME previously controlling the MBMS session with a "Local MBMS bearer context release" indication to instruct that MME to release its MBMS bearer context locally, without sending any message to the MCE(s).
- if the MBMS GW has not yet moved the control of the MBMS session to an alternative MME (e.g. if the MBMS restoration procedures are not supported in the network),
- if the Sm path failure is transient from the perspective of the MBMS GW, the MBMS GW shall consider that MBMS session is still controlled by the related MME and proceed as if there had been no Sm path failure;
- if the Sm path failure is non transient from the perspective of the MBMS GW, the MBMS GW shall send an MBMS Session Start Request to the MME for the session and encode it as specified above (for a message sent to an alternative MME).
NOTE 7: The MBMS GW cannot know whether the MME will see the Sm path failure as transient or non transient if the Sm path recovers in the period between the maximum path failure timer of the MME plus and minus the period between two Echo Request messages sent by the MME. This can possibly lead the MBMS GW to send an MBMS Session Stop request to the MME for a session that has already been terminated by the MME (if the MME determined the failure is non transient) or to send an MBMS Session Start request (with the "MBMS session re-establishment indication" flag) to the MME for a session that is still alive at the MME (if the MME determined the failure is transient). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.3.2 Sn path failure | The MBMS GW may be provisioned with the list (or a sub list) of the SGSNs belonging to the SGSN pool.
NOTE: The MBMS GW expects only one SGSN of the SGSN pool in BM-SC requests received across the SGmb interface.
An MBMS GW and SGSN shall handle Sn path failure similar to the Sm path failure as described in clause 20.2.3.1 For IP Unicast over Sn/Iu when the SGSN changes the MBMS GW has to move the user plane which is affected by the Sn-path failure additionally. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.3.3 SGmb path failure | In deployments without a Diameter Agent between the BM-SC and the MBMS GW, the MBMS GW shall detect an SGmb path failure using either:
- mechanisms as specified in the Diameter Base Protocol (e.g. transport connection failure, BM-SC peer not responding, Diameter Device-Watchdog-Request and Device-Watchdog-Answer messages during periods when there is no need for other MBMS signalling); or
- the MBMS Heartbeat procedure (see clause 29), if this procedure is supported.
In deployments with a Diameter Agent between the BM-SC and the MBMS GW, the MBMS GW shall detect an SGmb path failure using the MBMS Heartbeat procedure (see clause 29).
NOTE 1: A transport connection failure does not allow to identify a failure of the remote MBMS peer. Likewise, it is not possible to rely on Diameter Device-Watchdog-Request / Answer messages to test the responsiveness of the remote MBMS node during periods when there is no need for other MBMS signalling as these messages are only exchanged between Diameter peers with a direct transport connection.
Upon detecting an SGmb path failure, the MBMS GW should maintain the MBMS bearer contexts associated with the peer's BM-SC during an operator configurable maximum path failure duration.
If the SGmb path to the BM-SC is down for a duration exceeding the maximum path failure duration, the MBMS GW should deactivate all the related MBMS Bearer contexts locally and send MBMS Session Stop Requests towards all MME/SGSNs in which the MBMS bearer services are active.
NOTE 2: This enables to free corresponding radio resources in E-UTRAN/UTRAN for MBMS services if the BM-SC has failed without restart.
The MBMS GW shall pass on the "MBMS session re-establishment indication" flag in the MBMS Session Start Request it sends to MME/SGSNs if received from the BM-SC.
The MBMS GW shall pass on the "Local MBMS bearer context release" indication in the MBMS Session Stop Request it sends to MME/SGSNs if received from the BM-SC.
The MBMS GW shall accept an MBMS Session Start Request received for an on-going MBMS bearer service (i.e. with the same TMGI and, if provided, MBMS Flow Identifier) from the same BM-SC that currently controls the MBMS session if the message includes the "MBMS session re-establishment indication" flag. The MBMS GW shall replace the SGmb related resources for this MBMS service by those received in the MBMS Session Start Request (if different). The MBMS GW should not send MBMS Session Start Request message(s) towards the involved MME/SGSN(s) if no parameters other than the estimated duration and relative start time have changed. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.4 MME functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.4.1 Sm path failure | Upon detecting an Sm path failure, the MME should maintain the MBMS bearer contexts associated with the peer's MBMS GW IP address during an operator configurable maximum path failure duration.
The MME should behave as specified for the case of an MBMS GW restart (see clause 17A.1) if the Sm path to the MBMS GW is down for a duration exceeding the maximum path failure.
NOTE 1: This enables to free corresponding radio resources in E-UTRAN for MBMS services if the MBMS GW has failed without restart.
The MME shall pass on the "MBMS session re-establishment indication" flag in the MBMS Session Start Request it sends to MCEs if received from the MBMS GW.
The MME should accept an MBMS Session Start Request received for an on-going MBMS bearer service (i.e. with the same TMGI and, if provided, MBMS Flow Identifier) from a different MBMS GW than the MBMS GW that currently controls the MBMS session if the message includes the "MBMS session re-establishment indication" flag. If it accepts the request from the new MBMS GW, the MME shall replace the Sm related resources (i.e. TEID-C) for this MBMS service associated to the previous MBMS GW by those associated to the new MBMS GW and consider that the MBMS session is now being controlled by the new MBMS GW. The MME shall then send an MBMS Session Start Request message including the "MBMS session re-establishment" flag (and the new M1 transport parameters) towards all involved MCE(s).
The MME may accept an MBMS Session Start Request received for an on-going MBMS bearer service (i.e. with the same TMGI and, if provided, MBMS Flow Identifier) from a different MBMS GW than the MBMS GW that currently controls the MBMS session even if the message does not include the "MBMS session re-establishment indication" flag. If it accepts the request from the new MBMS GW, the MME shall replace the Sm related resources (i.e. TEID-C) for this MBMS service associated to the previous MBMS GW by those associated to the new MBMS GW and consider that the MBMS session is now being controlled by the new MBMS GW; the MME shall then either:
- stop the on-going MBMS bearer service and then start the new MBMS bearer service (without including the "MBMS session re-establishment indication" flag in the MBMS Session Start Request sent to the MCE(s)); or
- behave as if it had received an MBMS Session Start Request including the "MBMS session re-establishment indication" flag (i.e. include the "MBMS session re-establishment indication" flag in the MBMS Session Start Request sent to the MCE(s)).
The MME shall accept an MBMS Session Start Request received for an on-going MBMS bearer service (i.e. with the same TMGI and, if provided, MBMS Flow Identifier) from the same MBMS GW that currently controls the MBMS session if the message includes the "MBMS session re-establishment indication" flag. The MME shall replace the Sm related resources (i.e. TEID-C) for this MBMS service by those received in the MBMS Session Start Request (if different). The MME should not send MBMS Session Start Request message(s) towards the involved MCE(s) if no parameters other than the estimated duration and relative start time have changed.
The MME shall reject an MBMS Session Stop Request received for an on-going MBMS bearer service from a different MBMS GW than the MBMS GW that currently controls the MBMS session.
NOTE 2: Upon a non-transient SGmb path failure, if the BM-SC moves the control of an MBMS session to an alternative MBMS GW, the same MME can receive an MBMS Session Stop Request from the old MBMS GW after an MBMS Session Start Request from the new MBMS GW.
The MME shall release the MBMS bearer context resources locally without sending any message to the MCE(s) if it receives a MBMS Session Stop Request with a "Local MBMS bearer context release" indication for an on-going MBMS bearer service from the MBMS GW currently controlling the MBMS session. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.4.2 S5 path failure | The MME may support invoking the PGW triggered SGW restoration (see clause 27.2.3) upon receiving a PGW Downlink Triggering Notification message when the S11 path for the related UE is still available (see clause 20.2.1). If so, upon receiving a PGW Downlink Triggering Notification while the S11 path for the related UE is still available, the MME should proceed with the PGW triggered SGW restoration procedure (see clauses 27.2.3.2 and 27.3.2.2) with the following modifications:
- if the PGW F-TEID or PGW IP address and GRE key for control plane received in the PGW Downlink Triggering Notification message does not match the stored PGW F-TEID or PGW IP address and GRE key for control plane of any PDN connection(s) for that UE, the MME shall not proceed with the PGW triggered SGW restoration procedure but just respond to the SGW with a PGW Downlink Triggering Acknowledge message with an acceptance cause code;
NOTE 1: This can happen e.g. if the PDN connection has already been restored by the MME upon receipt of a preceding PGW Restart Notification message. In this case, the PDN connection remains hanging in the PGW until the timer monitoring the maximum duration to restore the PDN connection expires in the PGW.
- if the PGW F-TEID or PGW IP address and GRE key for control plane received in the PGW Downlink Triggering Notification message matches the stored PGW F-TEID or PGW IP address and GRE key for control plane of any PDN connection(s) for that UE, the MME shall proceed with the PGW triggered SGW restoration procedure.
- if the related UE is in connected mode, the MME may restore the PDN connection(s) of that UE by performing the MME triggered Serving GW relocation procedure as defined in clause 5.10.4 of 3GPP TS 23.401 [15].
NOTE 2: This avoids to tear down the S1 connection of the UE and thus to negatively affect other PDN connections of that UE that would not be impacted by the S5 path failure. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.5 SGSN functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.5.1 Sn path failure | Upon detecting an Sn path failure, the S4-SGSN should maintain the MBMS bearer contexts associated with the peer's MBMS GW IP address during an operator configurable maximum path failure duration.
The S4-SGSN should behave as specified for the case of an MBMS GW restart (see clause 17A.1) if the Sn path to the MBMS GW is down for a duration exceeding the maximum path failure.
NOTE 1: This enables to free corresponding radio resources in UTRAN for MBMS services if the MBMS GW has failed without restart.
The S4-SGSN shall pass on the "MBMS session re-establishment indication" flag in the MBMS Session Start Request it sends to RNCs if received from the MBMS GW.
The S4-SGSN should accept an MBMS Session Start Request received for an on-going MBMS bearer service (i.e. with the same TMGI and, if provided, MBMS Flow Identifier) from a different MBMS GW than the MBMS GW that currently controls the MBMS session if the message includes the "MBMS session re-establishment indication" flag. If it accepts the request from the new MBMS GW, the S4-SGSN shall replace the Sn related resources (i.e. TEID-C) for this MBMS service associated to the previous MBMS GW by those associated to the new MBMS GW and consider that the MBMS session is now being controlled by the new MBMS GW. The S4-SGSN shall then send an MBMS Session Start Request message including the "MBMS session re-establishment" flag (and the new M1 transport parameters) towards all involved RNC(s).
The S4-SGSN may accept an MBMS Session Start Request received for an on-going MBMS bearer service (i.e. with the same TMGI and, if provided, MBMS Flow Identifier) from a different MBMS GW than the MBMS GW that currently controls the MBMS session even if the message does not include the "MBMS session re-establishment indication" flag. If it accepts the request from the new MBMS GW, the S4-SGSN shall replace the Sn related resources (i.e. TEID-C) for this MBMS service associated to the previous MBMS GW by those associated to the new MBMS GW and consider that the MBMS session is now being controlled by the new MBMS GW; the S4-SGSN shall then either:
- stop the on-going MBMS bearer service and then start the new MBMS bearer service (without including the "MBMS session re-establishment indication" flag in the MBMS Session Start Request sent to the RNC(s)); or
- behave as if it had received an MBMS Session Start Request including the "MBMS session re-establishment indication" flag (i.e. include the "MBMS session re-establishment indication" flag in the MBMS Session Start Request sent to the RNC(s)).
The S4-SGSN shall accept an MBMS Session Start Request received for an on-going MBMS bearer service (i.e. with the same TMGI and, if provided, MBMS Flow Identifier) from the same MBMS GW that currently controls the MBMS session if the message includes the "MBMS session re-establishment indication" flag. The S4-SGSN shall replace the Sn related resources (i.e. TEID-C) for this MBMS service by those received in the MBMS Session Start Request (if different). The S4-SGSN should not send MBMS Session Start Request message(s) towards the involved RNC(s) if no parameters other than the estimated duration and relative start time have changed.
The S4-SGSN shall reject an MBMS Session Stop Request received for an on-going MBMS bearer service from a different MBMS GW than the MBMS GW that currently controls the MBMS session.
NOTE 2: Upon a non-transient SGmb path failure, if the BM-SC moves the control of an MBMS session to an alternative MBMS GW, the same S4-SGSN can receive an MBMS Session Stop Request from the old MBMS GW after an MBMS Session Start Request from the new MBMS GW.
The S4-SGSN shall release the MBMS bearer context resources locally without sending any message to the RNC(s) if it receives a MBMS Session Stop Request with a "Local MBMS bearer context release" indication for an on-going MBMS bearer service from the MBMS GW currently controlling the MBMS session. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.5.2 S5 path failure | The S4-SGSN may support invoking the PGW triggered SGW restoration (see clause 27.2.3) upon receiving a PGW Downlink Triggering Notification and the S4 path of the related UE is still available (see clause 20.2.1). If so, S4-SGSN shall proceed as defined for the MME in clause 20.2.4.2, with the following modification:
- if the related UE is in connected mode, the S4-SGSN may restore the PDN connection(s) of that UE by performing the S4-SGSN triggered Serving GW relocation procedure as defined in clause 9.2.2.4 of 3GPP TS 23.060 [5]. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.6 BM-SC functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.6.1 SGmb path failure | In deployments without a Diameter Agent between the BM-SC and the MBMS GW, the BM-SC shall detect an SGmb path failure using either:
- mechanisms as specified in the Diameter Base Protocol (e.g. transport connection failure, MBMS GW peer not responding, Diameter Device-Watchdog-Request and Device-Watchdog-Answer messages during periods when there is no need for other MBMS signalling); or
- the MBMS Heartbeat procedure (see clause 29), if this procedure is supported.
In deployments with a Diameter Agent between the BM-SC and the MBMS GW, the BM-SC shall detect an SGmb path failure using the MBMS Heartbeat procedure (see clause 29).
NOTE 1: A transport connection failure does not allow to identify a failure of the remote MBMS peer. Likewise, it is not possible to rely on Diameter Device-Watchdog-Request / Answer messages to test the responsiveness of the remote MBMS node during periods when there is no need for other MBMS signalling as these messages are only exchanged between Diameter peers with a direct transport connection.
Upon detecting an SGmb path failure, the BM-SC should maintain the related MBMS bearer contexts.
During a transient SGmb path failure (e.g. before the maximum path failure duration timer expires), the BM-SC should consider all related MBMS bearer contexts as active in the MBMS GW. The BM-SC may initiate new MBMS sessions via an alternative MBMS GW (if available). The BM-SC should defer any MBMS session update or stop procedure for on-going MBMS sessions in the MBMS GW affected by the SGmb path failure until the transient path failure ends.
NOTE 2: Re-establishing an MBMS session via an alternative MBMS GW can generate network signalling over many interfaces and interrupt transiently the delivery of the MBMS data stream due to the need for related eNB/RNCs to switch to the new IP multicast group over M1. Thus during a transient SGmb path failure it is recommended to defer any MBMS session update or stop procedure for on-going MBMS sessions in the MBMS GW affected by the SGmb path failure. However if the MBMS session update or stop procedure is for time critical services, the BM-SC can immediately re-establish the active MBMS bearer services affected by the SGmb path failure by initiating MBMS Session Start procedure(s) towards an alternative MBMS GW (if available) as specified below, and subsequently send the MBMS Session Update or Stop message.
When detecting a non-transient SGmb path failure (e.g. the maximum path failure duration timer of the BM-SC expires), the BM-SC should re-establish the active MBMS bearer services affected by the SGmb path failure by initiating MBMS Session Start procedure(s) towards an alternative MBMS GW (if available) or towards the same MBMS GW (once the SGmb path is recovered). If the MBMS session is not re-established and if it was activated by a Group Communication Service Application Server(s) (GCS AS), the BM-SC shall notify the GCS AS that the MBMS session has been deactivated.
NOTE 3: This enables to re-establish the MBMS sessions when a MBMS GW fails without restart.
The maximum path failure duration of the BM-SC should be configured with a shorter value than the maximum path failure duration timer of the MBMS GW to minimize the interruption of the active MBMS sessions upon a non-transient SGmb path failure. The BM-SC timer should be shorter than the MBMS GW timer by at least the period between two Diameter Device-Watchdog-Request messages or MBMS Heartbeat Request messages sent by the MBMS GW, to avoid that the MBMS GW timer expires before the BM-SC timer if the MBMS GW starts its timer before the BM-SC.
NOTE 4: This enables the MCE/RNC to receive a MBMS Session Start request from the new MME/SGSN (and MBMS GW) controlling the MBMS session before the MCE/RNC receives a request to stop the MBMS service from the previous controlling MME/SGSN (and MBMS GW).
When re-establishing the active MBMS bearer services affected by the SGmb path failure, the BM-SC shall encode the MBMS Session Start Request with the same contents as in the original MBMS Session Start Request (or per the last MBMS Session Update Request sent by the BM-SC if the original parameters were updated) with the following exceptions:
- the BM-SC shall set the "MBMS session re-establishment indication" flag to signal that this message is used to re-establish an MBMS session;
- if no absolute start time ("MBMS data transfer start" parameter) has been sent, the BM-SC may change the relative start time ("time to MBMS data transfer" parameter) to fasten the restoration of the MBMS service in E-UTRAN;
- the BM-SC should set the estimated session duration to a value corresponding to the remaining duration of the session.
NOTE 5: If the BM-SC is instructed to modify an MBMS Session during the SGmb path failure, the contents of the MBMS Session Start Request sent to the MBMS GW after the SGmb path failure can also differ from the parameters sent to the MBMS GW before the SGmb path failure for the parameters that can be modified by the MBMS session update procedure (i.e. MBMS Session Area, MBMS Time to Data Transfer, MBMS Data Transfer Start).
After detecting an SGmb path failure, the BM-SC shall determine whether the failure is transient or non transient from the perpective of the MBMS GW (e.g. the BM-SC is provisioned with the maximum path failure timer of the MBMS GW). The BM-SC shall assume that the failure is non transient from the perspective of the MBMS GW if the SGmb path recovers after a period longer than the maximum path failure timer of the MBMS GW plus the period between two Diameter Device-Watchdog-Request messages or MBMS Heartbeat Request messages sent by the MBMS GW, to ensure that the MBMS GW also determines this is a non transient path failure if the BM-SC starts its timer before the MBMS GW. The BM-SC shall consider that the MBMS session has been released by the MBMS GW if the SGmb path failure is non transient for the MBMS GW. If the SGmb path failure remains transient for the MBMS GW, the BM-SC shall behave as follows upon detecting the SGmb path recovery:
- if the BM-SC has already moved the control of the MBMS session to an alternative MBMS GW, the BM-SC shall send an MBMS Session Stop Request message to the MBMS GW previously controlling the MBMS session with a "Local MBMS bearer context release" indication to instruct that MBMS GW to release the MBMS bearer context locally in the MBMS GW and in the associated MME/SGSN(s) without sending any message to the MCE/RNC(s).
- if the BM-SC has not yet moved the control of the MBMS session to an alternative MBMS GW (e.g. if the MBMS restoration procedures are not supported in the network),
- if the SGmb path failure is transient from the perspective of the BM-SC, the BM-SC shall consider that the MBMS session is still controlled by the related MBMS GW and proceed as if there had been no SGmb path failure;
- if the SGmb path failure is non transient from the perspective of the BM-SC, the BM-SC shall send an MBMS Session Start Request to the MBMS GW for the session and encode it as specified above (for a message sent to an alternative MBMS GW).
NOTE 6: The BM-SC cannot know whether the MBMS GW will see the SGmb path failure as transient or non transient if the SGmb path recovers in the period between the maximum path failure timer of the MBMS GW plus and minus the period between two Diameter Device-Watchdog-Request messages or MBMS Heartbeat Request messages sent by the MBMS GW. This can possibly lead the BM-SC to send an MBMS Session Stop request to the MBMS GW for a session that has already been terminated by the MBMS GW (if the MBMS GW determined the failure is non transient) or to send an MBMS Session Start request (with the "MBMS session re-establishment indication" flag) to the MBMS GW for a session that is still alive at the MBMS GW (if the MBMS GW determined the failure is transient). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.6.2 MB2-C path failure | In deployments without a Diameter Agent between the BM-SC and the GCS AS, the BM-SC shall detect an MB2-C path failure using either:
- mechanisms as specified in the Diameter Base Protocol (e.g. transport connection failure, GCS AS peer not responding, Diameter Device-Watchdog-Request and Device-Watchdog-Answer messages during periods when there is no need for other MB2 signalling); or
- the MBMS Heartbeat procedure (see clause 29), if this procedure is supported.
In deployments with a Diameter Agent between the BM-SC and the GCS AS, the BM-SC shall detect an MB2-C path failure using the MBMS Heartbeat procedure (see clause 29).
NOTE 1: A transport connection failure does not allow to identify a failure of the remote MBMS peer. Likewise, it is not possible to rely on Diameter Device-Watchdog-Request / Answer messages to test the responsiveness of the remote MBMS node during periods when there is no need for other MB2 signalling as these messages are only exchanged between Diameter peers with a direct transport connection.
Upon detecting a non-transient MB2-C path failure, the BM-SC shall deallocate (locally) all the TMGIs that had been assigned to the GCS AS and the BM-SC shall stop all the related MBMS bearers to free the corresponding resources in E-UTRAN. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.7 PGW functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.7.1 S5 path failure | The PGW may support invoking the PGW triggered SGW restoration procedure (see clause 27.2.3) when detecting a path failure to an SGW (see clause 20.2.1). If so, after detecting a path failure to an SGW, the PGW should maintain the S5 bearer contexts eligible for restoration and proceed with the PGW triggered SGW restoration procedure with the following modifications:
- for GTP-based S5, the PGW shall include the PGW F-TEID for control plane in the PGW Downlink Triggering Notification message;
- for PMIP-based S5, the PGW shall include the PGW IP address and uplink GRE key for control plane in the PMIP Update Notification message; |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.8 GCS AS functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.8.1 MB2-C path failure | In deployments without a Diameter Agent between the BM-SC and the GCS AS, the GCS AS shall detect an MB2-C path failure using either:
- mechanisms as specified in the Diameter Base Protocol (e.g. transport connection failure, BM-SC peer not responding, Diameter Device-Watchdog-Request and Device-Watchdog-Answer messages during periods when there is no need for other MB2 signalling); or
- the MBMS Heartbeat procedure (see clause 29), if this procedure is supported.
In deployments with a Diameter Agent between the BM-SC and the GCS AS, the GCS AS shall detect an MB2-C path failure using the MBMS Heartbeat procedure (see clause 29).
NOTE 1: A transport connection failure does not allow to identify a failure of the remote MBMS peer. Likewise, it is not possible to rely on Diameter Device-Watchdog-Request / Answer messages to test the responsiveness of the remote MBMS node during periods when there is no need for other MB2 signalling as these messages are only exchanged between Diameter peers with a direct transport connection.
Upon detecting a non-transient MB2-C path failure, the GCS AS shall assume that all the TMGIs that had been assigned by the BM-SC have been de-allocated and that all the related MBMS bearers have been deactivated.
The GCS AS may restore the MBMS delivery e.g. via a different BM-SC using the MB2-C procedures specified in 3GPP TS 29.468 [36]. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.9 Sx interface functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.9.1 Sxa path failure | If the path to the SGW-U is down, the SGW-C should handle this as SGW-U Failure without Restart, see clause 16.1A.4.
If the path to the SGW-C is down, the SGW-U should handle this as SGW-C Failure without Restart, see clause 16.1A.3. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.2.9.2 Sxb path failure | If the path to the PGW-U is down, the PGW-C should handle this as PGW-U Failure without Restart, see clause 17.1A.4.
If the path to the PGW-C is down, the PGW-U should handle this as PGW-C Failure without Restart, see clause 17.1A.3. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3 User plane path failure detection and handling | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.1 General | GTP-U entities shall support detection of path failure by using Echo Request / Echo Response messages in the following way. A path counter shall be reset each time an Echo Response is received on the path and incremented when the T3-RESPONSE timer expires for any Echo Request message sent on the path. The path shall be considered to be down if the counter exceeds N3-REQUESTS.
Upon detecting a path failure, the network node should notify the failure via the Operation and Maintenance system and may either
- delete the bearer contexts associated with the path in failure; or
- maintain the bearer contexts associated with the path in failure during an operator configurable maximum path failure duration. The network node shall delete the maintained resources if the path is still down when this duration expires.
An MME may also perform relevant restoration procedure(s) if the S1-U path failure notification feature as specified in the following clause(s) is supported.
NOTE 1: During transient path failures (e.g. path failures not exceeding few minutes at most), maintaining the bearer contexts associated with the peer's IP address enables the delivery of end user services (when the path is re-established again) and also avoids unnecessary signalling in the network for restoring those bearers.
NOTE 2: It is not intended to maintain bearer contexts during long path failures (e.g. exceeding few minutes at most) as this would imply undesirable effects like undue charging. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.2 MBMS GW functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.2.1 SGi-mb path failure | An MBMS GW may support the detection of an SGi-mb path failure.
NOTE 1: How an MBMS GW detects an SGi-mb path failure is implementation specific. E.g. an MBMS GW can monitor the receipt of downlink user plane from the BM-SC (synchronization sequences are transmitted continuously e.g. in case of MBSFN transmissions, even if there is no MBMS user data to be sent).
Upon detecting a non-transient SGi-mb path failure (operator configurable maximum path failure duration), based on operator's policy, the MBMS GW may tear down the affected MBMS sessions by sending MBMS Session Stop Request message(s) to the MME/SGSN(s) serving the MBMS sessions and Session Termination Request message(s) to the BM-SC with a terminating cause signalling a user plane failure.
NOTE 2: This enables to free corresponding radio resources in E-UTRAN/UTRAN and to attempt to re-establish the MBMS session(s). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.3 BM-SC functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.3.1 SGi-mb path failure | Upon receipt of a Session Termination Request message from an MBMS GW with a terminating cause signalling a user plane failure, the BM-SC may attempt to re-establish the MBMS session via the same MBMS GW (using different user plane resources over SGi-mb) or an alternative MBMS GW.
When re-establishing the MBMS session, the BM-SC shall encode the MBMS Session Start Request with the same contents as in the original MBMS Session Start Request (or per the last MBMS Session Update Request sent by the BM-SC if the original parameters were updated) with the following exceptions:
- the BM-SC shall set the "MBMS session re-establishment indication" flag to signal that this message is used to re-establish an MBMS session;
- if no absolute start time ("MBMS data transfer start" parameter) has been sent, the BM-SC may change the relative start time ("time to MBMS data transfer" parameter) to fasten the restoration of the MBMS service in E-UTRAN;
- the BM-SC should set the estimated session duration to a value corresponding to the remaining duration of the session;
- the BM-SC shall provide the new user plane resources assigned to the MBMS session over SGi-mb.
If the MBMS session is not re-established and if it was activated by a Group Communication Service Application Server(s) (GCS AS), the BM-SC shall notify the GCS AS that the MBMS session has been deactivated. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.4 With Control and User plane Separation of SGW or PGW nodes | With a split SGW or PGW (see 3GPP TS 23.214 [42]), user plane path failure detection and handling shall be supported as specified in clause 20.3.1 with the following additional requirements:
- upon detecting a GTP-U user plane path failure, the SGW-U or PGW-U shall report the user plane path failure to the SGW-C or PGW-C respectively, by sending an PFCP Node Report Request (see 3GPP TS 29.244 [43]) including a User Plane Path Failure Report with the IP address of the remote GTP-U peer(s) towards which a failure has been detected;
- upon detecting a failed GTP-U user plane path become recovered, the SGW-U or PGW-U shall report the user plane path recovery to the SGW-C or PGW-C respectively, by sending an PFCP Node Report Request (see 3GPP TS 29.244 [43]) including a User Plane Path Recovery Report with the IP address of the remote GTP-U peer(s) associated with the user plane path recovered;
- upon being notified about the user plane path failure, when deciding to delete the bearer contexts associated with the path in failure, the SGW-C or PGW-C shall modify or delete the affected PFCP sessions in the SGW-U or PGW-U.
NOTE: The SGW-C and PGW-C need to take care to smooth the signalling load towards the SGW-U and PGW-U if a large number of PFCP sessions are affected by the user plane path failure.
An SGW-C may support S1-U path failure notification feature as specified in clause 20.3.5.
20.3.4A Reporting of a Peer GTP-U Entity Restart
When Control Plane and User Plane Separation (CUPS) is deployed, to reduce massive amount of Sx signalling to report the receiving of GTP-U Error Indication messages and to perform subsequent PFCP Session Modification for PFCP sessions affected by the peer GTP-U restart, a user plane function (SGW-U or PGW-U) and a control plane function (SGW-C or PGW-C) may optionally support reporting of a peer GTP-U entity restart.
A GTP-U entity, e.g. in a SGW-U or a PGW-U, may detect the restart of the peer GTP-U entity as specified in clause 18A.
When the user plane function detects the peer GTP-U entity has restarted via receiving one or more GTP-U Error Indication message(s) or Echo Request/Response message(s) containing a larger Recovery Time Stamp, and when the control plane function supports Reporting of a GTP-U Entity Restart, it shall send a PFCP Node Report Request message to the control plane function to report that:
- the peer GTP-U entity identified by Remote GTP-U Peer IE has restarted; and
- all PFCP sessions associated with the restarted peer GTP-U entity have been modified by the user plane function, i.e. the F-TEID(s) that had been allocated by the restarted GTP-U entity have been removed from the FARs and the Apply-Action in these FARs changed to BUFF and NOCP, if the restarted GTP-U entity is a RNC or eNB.
NOTE: The UP function can learn if the restarted GTP-U entity is a RNC or eNB by using the Destination Interface Type included in the Forwarding Parameters in the FAR (which contains the F-TEID that had been allocated by the restarted GTP-U entity).
The control plane function shall send a PFCP Node Report Response message to acknowledge the receipt of the report of the peer GTP-U entity restart; and the control plane may further behave as if it receives a GTP-U Error Indication Report for those PFCP sessions affected by the peer GTP-U entity restart, e.g. to trigger Downlink Data Notification procedure as part of Network Triggered Service Request procedure if the restarted GTP-U entity is a RNC or eNB. (see also clauses 21.7 and 21.8) |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.5 SGW functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.5.1 S1-U path failure | An SGW, with or without CUPS support, may optionally support the following S1-U path failure notification feature.
If the feature is supported and deployed in the network, after detecting a S1-U user plane path failure:
- If the SGW decides to keep the bearer contexts associated with the failed path (e.g. when the operator configurable maximum path failure duration timer has not expired), the SGW shall notify the MME of the S1-U path failure in subsequent signalling procedures associated with those PDN connections that are affected by the failed S1-U path as follows:
- when the SGW receives a Create Session Request message with eNodeB F-TEID(s), e.g. in an S1/X2 handover with SGW relocation procedure, or a Modify Bearer Request message or a Modify Access Bearer Request message, e.g. in a Service Request procedure:
- if all default bearer contexts are associated with failed S1-U paths, the SGW shall reject the request messages with the cause code "S1-U Path Failure" at the message level;
- if the bearer context(s) associated with the failed S1-U path(s) is not the default bearer context, the SGW may partially accept the Create Session Request or the Modify Bearer Request message and shall include the cause code "S1-U Path Failure" at the bearer context level for the bearer context(s) associated with failed S1-U path(s);
- if at least one of default bearers among multiple PDN connections from the same UE is not associated with the failed S1-U path, the SGW may partially accept the Modify Access Bearer Request message including the cause code "S1-U Path Failure" at the bearer context level for the bearer context associated with failed S1-U path;
- at reception of downlink packets to be sent towards an S1-U bearer associated with a failed S1-U path, the SGW shall send a Downlink Data Notification message with the cause code "S1-U Path Failure".
- If the SGW decided to delete the bearer contexts associated with the failed path, the SGW shall include a cause code "S1-U path failure" in the Delete Bearer Request message. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.6 MME functionality | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 20.3.6.1 S1-U path failure | An MME may optionally support the following S1-U path failure notification feature.
If the feature is supported and deployed in the network, after receiving the cause code "S1-U Path Failure" in a Create Session Response or a Modify Bearer Response or a Modify Access Bearer Response or a Downlink Data Notification or a Delete Bearer Request message:
- the MME shall derive the S1-U path information (e.g. the eNB F-TEID and the SGW F-TEID) from the UE Context and mark it as failed, and the MME shall store such information for a configurable period, and before the configured period is expired;
- the MME should avoid selecting the SGW with a failed S1-U path towards the eNB for subsequent PDN connection establishment procedures and mobility procedures with SGW relocation;
- if an alternative SGW without an S1-U path failure is available, the MME shall perform an SGW relocation procedure at a Service Request procedure for the PDN Connection(s) where the default bearer is associated with a failed S1-U path as specified in clause 5.10.4 of 3GPP TS 23.401 [15].
- if an alternative SGW without an S1-U path failure is available, the MME should perform an SGW relocation procedure for all active PDN connections where the default bearer is associated with the failed S1-u path as specified in clause 5.10.4 of 3GPP TS 23.401 [15].
- the MME should deactivate the corresponding PDN connections using the "reactivation requested" cause value as specified in clause 5.10.3 of 3GPP TS 23.401 [15] if it receives a Delete Bearer Request with the cause "S1-U Path Failure" for deleting the PDN connection;
- the MME shall deactivate the corresponding E-RAB for the bearer context(s) associated with failed S1-U path(s) if it receives a Delete Bearer Request message with the cause "S1-U Path Failure" for deleting dedicated bearer context(s). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21 Error Indication handling | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.1 General | The following clauses specify a network element behaviour, if it receives a GTPv1-U Error Indication message. The reception of the message triggers a node internal procedure and/or a Control Plane procedure (GTPv1-C, GTPv2, RANAP, S1-AP).
For the PMIP based S5/S8 interface, an error in the form of an ICMP message is used instead of a GTPv1-U Error Indication message for the Error Indication handling. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.2 GGSN | GTP error indication message shall be handled as follows:
- If the GGSN receives a GTP error indication for a PDP context that has the DTI flag set (i.e. from an RNC), the GGSN should not delete the associated PDP context but mark it as invalid. Any subsequent packets arriving for an invalid PDP context should be discarded. The GGSN shall inform the SGSN that the GGSN received a GTP error indication from RNC. The SGSN shall re-establish the tunnel between the SGSN and GGSN as specified in 3GPP TS 29.060 [8], which sets the related PDP context as valid again in the GGSN. The GGSN then forwards any subsequent downlink packets to the SGSN.
- If the GGSN receives a GTP error indication for a PDP context that has the no DTI flag set (i.e. from an SGSN), the GGSN shall delete its PDP context and may notify the Operation and Maintenance network element. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.3 Gn/Gp SGSN | GTP error indication message shall be handled as follows:
- If the SGSN receives a GTP error indication from a GGSN, the SGSN shall delete its PDP context and may notify the Operation and Maintenance network element. Additionally it shall send a Deactivate PDP Context Request message to the MS with cause "re-activation required"
- If the SGSN receives a GTP error indication from the RNC it shall locally release the RAB. The SGSN should preserve the associated PDP context. The SGSN may initiate the RAB Assignment procedure in order to re-establish the RAB.
- For MBMS, when an Error Indication is received from an SGSN, the receiving GGSN shall delete all information associated with the relevant SGSN in its MBMS Bearer Context and the GGSN may notify the Operation and Maintenance network element. In addition, for broadcast mode the GGSN may request the re-establishment of the MBMS Bearer Context by sending an MBMS Session Start Request message (see clause 7.5A.2.5 of 3GPP TS 29.060 [8]). Furthermore, if the GGSN serves only one downstream SGSN for MBMS data transfer and the GGSN does not support the re-establishment procedure, the GGSN shall delete its MBMS Bearer Context together with the affected MBMS UE Context(s). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.4 S4 SGSN | GTP error indication message shall be handled as follows:
- If the S4-SGSN receives a GTP error indication from a SGW, the S4-SGSN shall delete its Bearer context and may notify the Operation and Maintenance network element. Additionally it shall send a Deactivate PDP Context Request message to the MS with cause "re-activation required"
- If the S4-SGSN receives a GTP error indication from the RNC it shall locally release the RAB. The S4-SGSN should preserve the associated Bearer context. The S4-SGSN may initiate the RAB Assignment procedure in order to re-establish the RAB. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.5 RNC or NodeB | GTP error indication message shall be handled as follows:
- When the RNC receives GTP error indication from the SGSN, it shall initiate the RAB Release procedure with the error cause "GTP Resources Unavailable" and shall immediately locally release the RAB (i.e. without waiting for a response from the SGSN).
- If the RNC receives a GTP error indication from the GGSN (i.e. if Direct Tunnel is established), it shall initiate the RAB Release procedure with the error cause "GTP Resources Unavailable" and immediately locally release the RAB (i.e. without waiting for a response from the SGSN). The SGSN shall delete the related PDP context at the SGSN and send a Deactivate PDP Context Request message to the MS with cause "re-activation required".
- If the RNC receives a GTP error indication from the SGW (i.e. if Direct Tunnel is established), it shall initiate the RAB Release procedure with the error cause "GTP Resources Unavailable" and immediately locally release the RAB (i.e. without waiting for a response from the SGSN). The SGSN shall delete the related PDP context and send a Deactivate PDP Context Request message to the MS with the cause "re-activation required". If the deleted PDP context is a primary PDP context, the SGSN shall set the "Tear down indicator" bit in the Deactivate PDP Context Request message. The SGSN may also optionally send a Delete Bearer Command or a Delete Session Request message to the SGW if the deleted PDP context is a secondary PDP context or a primary PDP context respectively.
NOTE: Sending a Delete Bearer Command or a Delete Session Request message to the SGW can help the SGSN to determine whether the GTP error indication was due to the release of the bearer context or the release of the UE context in the SGW. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.6 eNodeB | GTP error indication message shall be handled as follows:
- If the eNodeB receives a GTP error indication from the SGW over an S1-U tunnel not doing indirect forwarding, it shall initiate the E-RAB Release procedure and immediately locally release the E-RAB (i.e. without waiting for a response from the MME). If the MME receives the E-RAB Release Indication for a default bearer that is not the last default bearer of a UE or that the UE has a SCEF PDN connection or that the UE supports Attach without PDN connectivity as specified in clause 5.3.8.3 of 3GPP TS 23.401 [15], the MME should send a Delete Session Request to the SGW. Additionally the MME may also send a Deactivate EPS Bearer Context Request to the UE with the ESM cause set to "Reactivation Requested" if the MME has decided to restore the PDN connection based on operator policy, QCI and/or ARP and/or APN. If the MME receives the E-RAB Release Indication for the last default bearer of a UE and the UE does not have a SCEF PDN connection and the UE does not support Attach without PDN connectivity as specified in clause 5.3.8.3 of 3GPP TS 23.401 [15], the MME shall initiate a MME initiated Detach procedure with the detach type "re-attach required". If the MME receives the UE Context Release Request from the eNB, the MME shall send a Release Access Bearers Request to the SGW but if the SGW responds with a "context not found" cause and the UE does not have a SCEF PDN connection and the UE does not support Attach without PDN connectivity, then the MME shall initiate a MME initiated Detach procedure with the detach type "re-attach required".
- If the eNodeB receives a GTP error indication from a peer eNodeB over an X2-U direct forwarding tunnel or from an SGW over an S1-U indirect forwarding tunnel, the eNodeB may ignore the error indication received over the forwarding tunnels or delete the forwarding tunnel context locally without deleting the EPS bearers.
- For dual connectivity case as specified in 3GPP TS 36.300 [32]:
- If the MeNodeB receives a GTP error indication from the SGW over an S1-U tunnel, it shall initiate the E-RAB Release procedure and immediately locally release the E-RAB (i.e. without waiting for a response from the MME);
- If the MeNodeB/SeNodeB receives a GTP error indication from the peer SeNodeB/MeNodeB, the MeNodeB/SeNodeB shall delete the X2-U tunnel locally;
- If the SeNodeB receives a GTP error indication from the SGW over an S1-U tunnel, it shall delete the S1-U tunnel locally;
- The MeNodeB and SeNodeB may initiate an additional dual connectivity procedure(s) as specified in 3GPP TS 36.300 [32]. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.7 SGW | GTP error indication message shall be handled as follows:
- For an 'Active' mode UE having a user plane connection with an RNC, i.e. SGW has F-TEIDs assigned by RNC for user plane for the UE,when the SGW receives a GTP Error Indication for a Bearer Context that has the DTI flag set (i.e. from an RNC), the SGW should not delete the associated Bearer Context but delete all the RNC GTP-U tunnel TEIDs for this MS and sends a Downlink Data Notification message to the SGSN (the complete behaviour is specified in clause 22). Then the SGW starts buffering downlink packets received for this MS.
- For an 'Active' mode UE having a user plane connection with an eNB, i.e. SGW has F-TEIDs assigned by eNB for user plane for the UE, when the SGW receives a GTP Error Indication for a Bearer Context from an eNodeB, the SGW should not delete the associated Bearer Context but delete all the eNodeB GTP-U tunnel TEIDs for this UE and sends a Downlink Data Notification message to the MME (the complete behaviour is specified in clause 22). Then the SGW starts buffering downlink packets received for this UE.
- For a UE having an S11 user plane connection with an MME, i.e. SGW has S11-U F-TEIDs assigned by MME for user plane for the UE, when the SGW receives a GTP Error Indication for a Bearer Context from an MME, the SGW may:
- delete all the Bearer contexts associated with the PDN connection (identified by the default bearer) and notify the Operation and Maintenance network element, or as an alternative,
- delete the MME GTP-U tunnel TEID for this UE and send a Downlink Data Notification message to the MME to re-establish the user plane path without deleting the PDN connection (the complete behaviour is specified in clause 22). Then the SGW starts buffering downlink packets received for this UE.
- If the SGW receives a GTP error indication from S4-SGSN for a Bearer Context other than the default bearer when S4-U is used, the SGW may delete its Bearer context and may notify the Operation and Maintenance network element, or as an alternative, the SGW may send Downlink Data Notification message to the S4-SGSN to re-establish the user plane path without deleting the bearer context.
- If the SGW receives a GTP error indication from S4-SGSN for the default bearer when S4-U is used, the SGW may delete all the Bearer contexts associated with the PDN connection (identified by the default bearer) and may notify the Operation and Maintenance network element, or as an alternative, the SGW may send Downlink Data Notification message to the S4-SGSN to re-establish the user plane path without deleting the PDN connection.
- If the SGW receives a GTP error indication from a PGW for the bearer other than the default bearer, the SGW shall delete its Bearer context and may notify the Operation and Maintenance network element.
- If the SGW receives a GTP error indication from a PGW for the default bearer, the SGW shall delete all the Bearer contexts associated with the PDN connection (identified by the default bearer) and may notify the Operation and Maintenance network element. The SGW may send the Delete Bearer Request for the default bearer to the MME/S4 SGSN to delete the associated PDN connection.
PMIP error indication message shall be handled as follows:
- If the SGW receives an ICMP message from a PGW that indicates the UE specific error indication, as specified in the 3GPP TS 29.275 [16], the SGW may delete the associated PDN connection (identified by the GRE key included in the ICMP message) and may notify the Operation and Maintenance network element. In this case, the SGW may also:
- send the Delete Bearer Request for the default bearer to the MME/S4 SGSN to delete the associated PDN connection, and/or,
- perform other implementation specific actions, such as: sending messages to release other external resources (e.g. PCC messages). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.8 PGW | GTP error indication message shall be handled as follows:
- If the PGW receives a GTP error indication from a SGW/a TWAN /an ePDG for the bearer other than the default bearer, the PGW shall delete its Bearer context and may notify the Operation and Maintenance network element.
- If the PGW receives a GTP error indication from a SGW/a TWAN /an ePDG for the default bearer, the PGW shall delete all the Bearer contexts associated with the PDN connection (identified by the default bearer) and may notify the Operation and Maintenance network element.
PMIP error indication message shall be handled as follows:
- If the PGW receives an ICMP message from an SGW/an ePDG/a Trusted Non-3GPP IP access node that indicates the UE specific error indication as specified in the 3GPP TS 29.275 [16], the PGW may delete the associated PDN connection (identified by the GRE key included in the ICMP message) and may notify the Operation and Maintenance network element. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.9 MBMS GW | GTP Error Indication message shall be handled as follows:
- If the MBMS GW receives a GTP Error Indication from a SGSN, the MBMS GW shall delete its Bearer context and may notify the Operation and Maintenance network element. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.10 ePDG | GTP error indication message shall be handled as follows:
- If the ePDG receives a GTP error indication from a PGW for the bearer other than the default bearer, the ePDG shall delete its Bearer context and may notify the Operation and Maintenance network element.
- If the ePDG receives a GTP error indication from a PGW for the default bearer, the ePDG shall delete all the Bearer contexts associated with the PDN connection (identified by the default bearer) and initiate the release of the corresponding SWu instance (i.e. IKEv2 tunnel). The ePDG may notify the Operation and Maintenance network element.
PMIP error indication message shall be handled as follows:
- If the ePDG receives an ICMP message from a PGW that indicates the UE specific error indication as specified in the 3GPP TS 29.275 [16], the ePDG may delete the associated PDN connection (identified by the GRE key included in the ICMP message) and initiate the release of the corresponding SWu instance (i.e. IKEv2 tunnel) . The ePDG may notify the Operation and Maintenance network element. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.11 TWAN | GTP error indication message shall be handled as follows:
- If the TWAN receives a GTP error indication from a PGW for the bearer other than the default bearer, the TWAN shall delete its Bearer context and may notify the Operation and Maintenance network element.
- If the TWAN receives a GTP error indication from a PGW for the default bearer, the TWAN shall delete all the Bearer contexts associated with the PDN connection (identified by the default bearer) and may initiate the release of the corresponding WLAN specific resource. The TWAN may notify the Operation and Maintenance network element.
PMIP error indication message shall be handled as follows:
- If the TWAN receives an ICMP message from a PGW that indicates the UE specific error indication as specified in the 3GPP TS 29.275 [16], the TWAN may delete the associated PDN connection (identified by the GRE key included in the ICMP message) and may initiate the release of the corresponding WLAN specific resource. The TWAN may notify the Operation and Maintenance network element. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 21.12 MME | GTP error indication message shall be handled as follows:
- If the MME receives a GTP error indication from an SGW, the MME shall delete its Bearer context and may notify the Operation and Maintenance network element. Additionally the MME shall deactivate the corresponding PDN connection towards the UE with the cause "re-activation required", or initiate an explicit detach with reattached required procedure, as appropriate, see 3GPP TS 24.301 [19]. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 22 Downlink Data Notification Handling at MME/S4 SGSN | If the MME/S4 SGSN receives a Downlink Data Notification message from the SGW as a result of the SGW having received an Error Indication message from the eNodeB/RNC or S4-SGSN over S4 User Plane, the MME/S4 SGSN should perform the following:
- If the UE is in IDLE state, upon receipt of the Downlink Data Notification message, the MME/S4 SGSN shall perform the Network Triggered Service Request procedure as specified in 3GPP TS 23.060 [5] and 3GPP TS 23.401 [15].
- If the UE is in CONNECTED state, upon receipt of the Downlink Data Notification message, the MME shall perform S1 Release procedure and perform Network Triggered Service Request procedure as specified in 3GPP TS 23.401 [15].
- If the UE is in CONNECTED state, upon receipt of the Downlink Data Notification message and Direct Tunnel is used, the S4-SGSN shall perform Iu Release procedure and perform Network Triggered Service Request procedure as specified in 3GPP TS 23.060 [5] if the cause value included in Downlink Data Notification is "Error Indication received from RNC/eNodeB/S4-SGSN",
- If the UE is in CONNECTED state, upon receipt of the Downlink Data Notification message and Direct Tunnel is not used, the S4-SGSN should re-establish all of the S4-U bearers of this UE if the cause value included in Downlink Data Notification is "Error Indication received from RNC/eNodeB/S4-SGSN".
Upon receipt of a Downlink Data Notification message from the SGW, caused by an Error Indication message received from the MME over the S11 User Plane, the MME should perform the following if the UE is known by the MME:
- If the UE is in IDLE state, the MME shall perform the Network Triggered Service Request procedure as specified in 3GPP TS 23.401 [15].
- If the UE is in CONNECTED state, the MME may perform an S1 Release procedure and a Network Triggered Service Request procedure as specified in 3GPP TS 23.401 [15], or as an alternative, the MME may keep the existing S1 signalling connection and just send a Modify Bearer Request message to the SGW to re-establish the S11-U tunnel.
If the MME receives a Downlink Data Notification message from the SGW as a result of the SGW having detected a S1-U path failure, and if the MME supports S1-U path failure notification feature, the MME shall behave as specified in clause 20.3.6. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 23 General partial failure handling procedures | The partial failure handling is an optional feature for MME, SGW, ePDG, TWAN and PGW. Partial failure handling is an optional feature between SGW-C, PGW-C, SGW-U and PGW-U for split SGW and PGW (see 3GPP TS 23.214 [42]).
For split SGW and PGW, the description in this clause related to SGW applies to SGW-C and PGW applies to PGW-C as well.
A partial failure handling feature may be used when a hardware or software failure affects a significant number of PDN connections while a significant number of PDN connections are unaffected. This feature may also be used for the degenerate case of a full/complete failure of a remote node (MME or PGW) in order to cleanup hanging PDN connections associated with the failed node. When it is impossible to recover the affected PDN connections (for example, using implementation-specific session redundancy procedures), it is useful to inform the peer nodes about the affected PDN connections for recovery on the peer nodes. Such a notification could be performed using an identifier that represents a large set of PDN connections rather than on individual PDN connection basis.
NOTE 1: If a hardware or software failure happens to impact only an insignificant number of PDN connections the node experiencing the fault need not treat the failure as a partial fault but may tear down connections one by one.
For the purposes of partial fault handling the term "node" refers to an entity that takes the role of an MME, PGW, ePDG, TWAN or SGW as defined in an SAE network.
A PDN Connection Set Identifier (CSID) shall identify a set of PDN connections within a node that may belong to an arbitrary number of UEs. A CSID is an opaque parameter local to a node. Each node that supports the feature maintains a local mapping of CSID to its internal resources. When one or more of those resources fail, the corresponding one or more fully qualified CSIDs are signalled to the peer nodes.
The fully qualified CSID (FQ-CSID) is the combination of the node identity and the CSID assigned by the node which together globally identifies a set of PDN connections.
NOTE 2: The node identifier in the FQ-CSID is required since two different nodes may use the same CSID value. A partial fault in one node should not cause completely unrelated PDN connections to be removed accidentally.
The node identifier shall be globally unique across all 3GPP EPS networks. Its format is defined in 3GPP TS 29.274 [13]
For the purposes of partial fault handling the term peer is used as follows: For a particular PDN connection two nodes are peers if both nodes are used for that PDN connection. For a PDN Connection Set the nodes are peers if they have at least one PDN connection in the PDN Connection Set where both nodes are used for that PDN connection. In particular PGW and MME are generally peers for the purposes of partial fault handling.
An FQ-CSID is established in a node and stored in peer nodes in the PDN connection at the time of PDN connection establishment, or during a node relocation, and used later during partial failure handling in messages defined in 3GPP TS 29.274 [13] and 3GPP TS 29.275 [16]. Each node that support the feature, including the MME, SGW, ePDG, TWAN and the PGW, shall maintain the FQ-CSID provided by every other peer node for a PDN connection. The FQ-CSIDs stored by PDN connection are later used to find the matching PDN connections when a FQ-CSID is received from a node reporting a partial fault for that FQ-CSID.
With the exception of the GTPv2 Delete PDN Connection Set Request and PMIPv6 Binding Revocation Indication BRI messages, each feature supporting MME, SGW, ePDG, TWAN or PGW shall assign only one FQ-CSID for itself in messages and each FQ-CSID shall have exactly one CSID within the FQ-CSID.
Following rules shall apply for all the nodes:
1) If a node (MME, SGW, ePDG, TWAN or PGW) supports the partial failure handling feature, it shall generate and include its own FQ-CSID during the PDN connection establishment, node relocation procedures. Explicit list of the relevant GTPv2 messages is given in the respective clauses (14.3 "Partial Failure Handling at MME", 16.2 "Partial Failure Handling at SGW", 17B.2 "Partial Failure Handling at ePDG", 17C.2 "Partial Failure Handling at TWAN" and 17.2 "Partial Failure Handling at PGW"). A node that supports partial failure handling feature shall also store peers' FQ-CSIDs.
2) Additionally, if an SGW supports partial failure handling feature, it shall forward the peer node's (of an MME or of a PGW, depending on the direction) FQ-CSID and also Delete Connection Set Request/Response messages. Also, if the SGW detects the full/complete failure of an MME or PGW, e.g., through the Echo Request/Echo Response procedure, it may send a Delete PDN Connection Set Request (or PMIPv6 Binding Revocation Indication with G bit set) message containing all of the FQ-CSIDs of the associated hanging PDN connections of the failed node to the corresponding remote node (MME or PGW) .
3) If a node that supports partial failure handling feature receives peer node's FQ-CSID during the procedures, which are specified in Rule 1, it shall conclude that the peer node supports the feature. Subsequently, the node shall store the peer node's FQ-CSID and shall send appropriate partial failure handling messages to the peer.
4) If a node that supports partial failure handling feature does not receive the peer's FQ-CSID during the procedures, which are specified in Rule 1, it shall conclude that the peer node does not support the feature.
5) A node that supports partial failure handling feature shall not send any FQ-CSID IE or any partial failure handling specific messages to the peer node if the sender is aware (see Rule 4) that the receiver does not support the feature.
6) If a node does not support the partial failure handling feature, it shall ignore any received FQ-CSID IE or any partial failure handling specific message.
7) During session management procedures as specified in 3GPP TS 23.401 [15] and 3GPP TS 23.402 [18] (such as a dedicated bearer activation/deactivation/update), a node supporting the partial failure handling feature may update its FQ-CSID to the supporting peer node(s) in the Create Bearer Request/Response, Delete Bearer Request/Response or Update Bearer Request/Response.
NOTE 3: FQ-CSID handling for the Initial Attach and various handover cases are addressed in clauses 14, 16 and 17.
In addition to the above requirements, for split SGW and PGW, the following applies:
1) If a node (SGW-C, SGW-U, PGW-C or PGW-U) supports the partial failure handling feature, it shall generate and include its own FQ-CSID during the Sx Session Establishment procedure.
2) The SGW-C shall initiate Sx Session Modification procedure to update the SGW-U with the MME FQ-CSID, PGW-C FQ-CSID if changed;
3) The PGW-C shall initiate Sx Session Modification procedure to update the PGW-U with the MME FQ-CSID, SGW-C FQ-CSID, TWAN FQ-CSID, or ePDG FQ-CSID if changed;
4) The SGW-C and the PGW-C may change its FQ-CSID during a Sx Session Modification procedure if its SEID is changed;
5) When the node (SGW-C, SGW-U, PGW-C or PGW-U) detects that it has undergone a partial failure, it shall send a Sx Session Set Deletion Request message containing all the its CSIDs of the component(s) failing to its peer node;
6) For a SGW-C or a PGW-C, it shall also send Sx Session Set Deletion Request to the SGW-U or PGW-U respectively containing MME FQ-CSID, ePDG FQ-CSID, TWAN FQ-CSID, PGW-C FQ-CSID or SGW-C FQ-CSID if it receives the corresponding GTPv2 message Delete PDN Connection Set Request message containing those FQ-CSID.
7) The SGW-C and the PGW-C shall initiate the restoration procedure to restore the Sx Sessions affected by the partial failure in the SGW-U or the PGW-U in the same way as specified in the clause 16.1A.3 for the SGW-U failure and 17.1A.3 for the PGW-U failure respectively, when receiving an Sx Session Set Deletion Request message including a SGW-U or a PGW-U FQ-CSID(s) which is associated with the partial failure from the SGW-U or the PGW-U.
Figure 23-1 illustrates FQ-CSID establishment during the Attach or PDN connection establishment procedures for 3GPP E-UTRAN access as specified in the above rules.
Figure 23-1: FQ-CSID establishment during the Attach or PDN establishment procedure for 3GPP E-UTRAN access
1. If an MME supports partial failure handling, the MME shall send own FQ-CSID to SGW with a Create Session Request message across S11 interface.
The MME's FQ-CSID indicates to the SGW that MME supports partial failure handling. If the SGW does not receive MME's FQ-CSID, then the SGW shall never send partial failure handling related messages or IEs to the MME.
If the SGW does not support partial failure handling, then the SGW shall silently discard MME's FQ-CSID.
If the SGW does support partial fault handling it shall store the MME's FQ-CSID in it's PDN connection table.
2. If the SGW supports partial failure handling, the SGW shall forward MME's FQ-CSID to PGW with a Create Session Request message or a Proxy Binding Update message across S5/S8 interface. The SGW shall also include own FQ-CSID into the message.
The SGW's FQ-CSID indicates to the PGW that the SGW supports partial failure handling.
If the PGW does not support partial failure handling, then the PGW shall silently discard both FQ-CSIDs.
3. If the SGW has indicated the support for partial failure handling to PGW, then the PGW, which supports the feature shall send own FQ-CSID back to the SGW with a Create Session Response message or a Proxy Binding Acknowledgement message across S5/S8 interface. PGW's FQ-CSIDs in the S5/S8 Create Session Response or a Proxy Binding Acknowledgement message indicates to the SGW that PGW supports partial failure handling.
If the SGW has not indicated support for partial failure handling, then PGW shall never send partial failure handling related messages or IEs to the SGW.
4. If the MME has indicated the support for partial failure handling to SGW, then the SGW, which supports the feature, shall forward PGW's FQ-CSID to MME with a Create Session Response message across S11 interface. The SGW shall also include own FQ-CSID into the message.
Figure 23-2 illustrates FQ-CSID establishment during the Attach or PDN connection establishment procedures for untrusted non-3GPP access as specified in the above rules.
Figure 23-2: FQ-CSID establishment during the Attach or PDN establishment procedure for non-3GPP access
1. If an ePDG/TWAN supports partial failure handling, the ePDG/TWAN shall send own FQ-CSID to PGW with a Create Session Request message across GTPv2 based S2b/S2a interface or a Proxy Binding Update message across PMIPv6 based S2b/S2a interface.
The ePDG's/TWAN's FQ-CSID indicates to the PGW that ePDG/TWAN supports partial failure handling. If the PGW does not receive ePDG's/TWAN's FQ-CSID, then the PGW shall never send partial failure handling related messages or IEs to the ePDG/TWAN.
2. If the PGW supports partial failure handling, it shall store the ePDG's/TWAN's FQ-CSID in its PDN connection table and it shall send own FQ-CSID back to the ePDG/TWAN with a Create Session Response message across GTPv2 based S2b/S2a interface or a Proxy Binding Acknowledgement message across PMIPv6 based S2b/S2a interface. PGW's FQ-CSIDs in the Create Session Response or Proxy Binding Acknowledgement indicates to the ePDG/TWAN that PGW supports partial failure handling. The ePDG/TWAN shall then store the PGW's FQ-CSID in its PDN connection table.
If the PGW does not support partial failure handling, then the PGW shall silently discard ePDG's/TWAN's FQ-CSID.
Figure 23-3 illustrates FQ-CSID establishment during the Sx Session Establishment procedure for 3GPP access, with a split SGW, as specified in the above rules.
Figure 23-3: FQ-CSID establishment during the Sx Session Establishment procedure
1. If an SGW-C supports partial failure handling, the SGW-C shall send its own FQ-CSID and MME FQ-CSID to the SGW-U in the Sx Session Establishment Request.
2. If the SGW-U supports partial failure handling, it shall store the SGW-C FQ-CSID and MME FQ-CSID for the related Sx Session and it shall send its own FQ-CSID back to the SGW-C in the Sx Session Establishment Response message. The SGW-U's FQ-CSID in the Create Session Establishment Response implicitly indicates to the SGW-C that SGW-U supports partial failure handling. The SGW-C shall then store the SGW-U's FQ-CSID for the related Sx Session. If the SGW-C does not receive an SGW-U FQ-CSID from the SGW-U, then the SGW-C shall not further send partial failure handling related messages or IEs to the SGW-U.
If the SGW-U does not support partial failure handling, then the SGW-U shall silently discard the SGW-C's FQ-CSID and MME FQ-CSID.
Figure 23-4 illustrates FQ-CSID establishment during the Sx session Establishment procedure with a split PGW as specified in the above rules.
Figure 23-4: FQ-CSID establishment during the Sx session establishment procedure
1. If a PGW-C supports partial failure handling, the PGW-C shall send its own FQ-CSID, SGW-C FQ-CSID, TWAN FQ-CSID, ePDG FQ-CSID and MME FQ-CSID to PGW-U in the Sx Session Establishment Request.
2. If the PGW-U supports partial failure handling, it shall store the PGW-C FQ-CSID, SGW-C FQ-CSID, TWAN FQ-CSID, ePDG FQ-CSID and MME FQ-CSID for the related Sx Session and it shall send its own FQ-CSID back to the PGW-C in the Sx Session Establishment Response message. The PGW-U's FQ-CSIDs in the Sx Session Establishment Response implicitly indicates to the PGW-C that PGW-U supports partial failure handling. The PGW-C shall then store the PGW-U's FQ-CSID for the related Sx Session. If the PGW-C does not receive a PGW-U FQ-CSID from the PGW-U, then the PGW-C shall not further send partial failure handling related messages or IEs to the PGW-U.
If the PGW-U does not support partial failure handling, then the PGW-U shall silently discard PGW-C's FQ-CSID.
Figure 23-5 illustrates FQ-CSID establishment during the Sx Session Establishment procedures to provide the PGW-C FQ-CSID to the SGW-U after receiving a PGW-C FQ-CSID in Create Session Response from PGW-C on the S5/S8 interface.
Figure 23-5: FQ-CSID establishment to provide a PGW-C FQ-CSID to the PGW-U
1. If an SGW-C supports partial failure handling and the SGW-U has indicated its support of partial failure in the Sx Session Establishment Response, the SGW-C shall send PGW-C FQ-CSID received on S5/S8 interface to the SGW-U in an Sx Session Modification Request.
2. If the SGW-U supports partial failure handling, it shall store the PGW-C FQ-CSID for the related Sx Session and send a reply to the SGW-C.
If the SGW-U does not support partial failure handling, then the SGW-U shall silently discard the PGW-C's FQ-CSID. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 24 Restoration of data in the PCRF | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 24.1 Restart of the PCRF | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 24.1.0 PCRF Restart | PCRF storage of PCC contexts is volatile. When a PCRF fails, the PCC contexts and Diameter sessions affected by the failure are lost in the PCRF.
When a PCRF receives a non-initial message for which no Diameter session exists, it shall discard the message and return a Diameter error indication to the originating PCRF client. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25 Network triggered service restoration procedure | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.1 General | The network triggered service restoration procedure is an optional feature for the MME, S4-SGSN and SGW. A node that supports this feature shall support the network triggered service restoration procedure without ISR as specified in clause 25.2 and the network triggered service restoration procedure with ISR as specified in clause 25.3 if it supports Idle mode Signalling Reduction (ISR) (see 3GPP TS 23.401 [15] and 3GPP TS 23.060 [5]).
The network triggered restoration procedure without ISR shall apply to UEs for which ISR is not active at the time the ISR associated node fails. The network triggered restoration procedure with ISR shall apply to UEs for which ISR is active at the time the ISR associated node fails. Both procedures may run in parallel if there is a mix of UEs with ISR and without ISR at the time the ISR associated node fails.
For the PMIP based S5/S8 case, the terminology "S5/S8 bearer" used through clause 25 shall be read as "S5/S8 IP traffic flow" within the GRE tunnel. The detailed concepts of the "IP traffic flow" are specified in 3GPP TS 23.402 [18]. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.2 Network triggered service restoration procedure without ISR | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.2.1 General | The following requirements shall apply if the MME or S4-SGSN and the SGW support this feature.
If an SGW detects that an MME or S4-SGSN has restarted (see clause 18 "GTP-C based restart procedures"), instead of removing all the resources associated with the peer node, the SGW shall maintain the PDN connection table data and MM bearer contexts for some specific S5/S8 bearer contexts eligible for network initiated service restoration, and initiate the deletion of the resources associated with all the other S5/S8 bearers.
NOTE 1: This enables the SGW to still receive downlink user plane or control plane data from the PGW or from a PCRF (PMIP based S5/S8) for the maintained S5/S8 bearers.
The S5/S8 bearers eligible for network initiated service restoration are determined based on operator's policy, e.g. based on the QCI and/or ARP and/or APN, and such operator's policy shall be applicable for both the SGW and the MME/SGSN. The Delay Tolerant Connection Indication (DTCI), if set, may also be used to determine that the S5/S8 bearer is not eligible for network initiated service restoration, based on operator's policy when using QCI and/or ARP and/or APN is not sufficient, e.g. for Home routed roaming scenario.
Emergency PDN connections for users without authenticated IMSI do not need to be maintained by the SGW and cannot be restored at the initiative of the network.
NOTE 2: Users with an emergency call in progress can re-attach and re-establish the emergency PDN connection after detecting the loss of the signalling connection with the RAN. IMS Emergency PSAP callback is not supported for unauthenticated users with an emergency registration but without an emergency call in progress.
If at least one S5/S8 bearer needs to be maintained, the SGW shall also start a timer controlling the maximum duration during which those bearers shall be maintained. There is one operator configurable timer per SGW. The timer value may be equal to the periodic tracking area update timer (timer T3412) as specified in 3GPP TS 24.301 [19] or the periodic routing area update timer (timer T3312) as specified in 3GPP TS 24.008 [20]. This timer ensures that the S5/S8 bearers eligible for network initiated service restoration are maintained until the corresponding UE reattaches to the network. If the timer expires, the maintained resources shall be locally deleted assuming that the corresponding UE might have reattached to the network via a different SGW.
The SGW shall not release the default bearer of a PDN connection for which one or more dedicated bearers are maintained. Any downlink user plane or control plane packet received on a default bearer which is not eligible for network initiated service restoration but which is maintained for dedicated bearer(s) eligible for such procedure shall be silently discarded by the SGW.
When releasing the maintained S5/S8 bearers, the SGW may optionally perform other implementation specific actions such as messages to clear other external resources (e.g. PCC messages to clear the resources in the PCRF or GTP/PMIP messages to release the corresponding PDN connection in the PGW).
If the SGW receives a Create Session Request message for a UE for which some S5/S8 bearers are maintained, the SGW shall delete all the bearers for this UE and proceed with the Create Session Request message handling as specified in 3GPP TS 29.274 [13]. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.2.2 SGW procedure | Upon receipt of the first downlink user plane or control plane packet on a maintained S5/S8 bearer or PCC signalling from PCRF, the SGW shall immediately send a Downlink Data Notification message including the IMSI to the respective MME or S4-SGSN. In addition, depending on the received downlink packet type the SGW shall proceed as follows:
- if the received downlink packet contains user plane data, the SGW shall silently discard it but the SGW shall continue maintaining the corresponding bearers. If the SGW receives another downlink user plane packet for an ARP value other than the ARP included in the Downlink Data Notification sent before, it shall proceed as specified in clause 5.3.4.3 "Network Triggered Service Request" of 3GPP TS 23.401 [15] with the exception that the packet shall be discarded by the SGW.
- For the S5/S8 GTP case:
- if the received downlink packet contains a control plane message other than a Delete Bearer Request message then the SGW may reject the message and shall continue maintaining the corresponding bearers. If the SGW receives another control plane message for an ARP value other than the ARP included in the Downlink Data Notification sent before, it shall proceed as specified in clause 5.3.4.3 "Network Triggered Service Request" of 3GPP TS 23.401 [15] with the exception that the message may be rejected by the SGW.
- if the received downlink packet contains the Delete Bearer Request message, the SGW shall accept the message, and shall release the corresponding S5/S8 bearer(s) immediately.
- For the S5/S8 PMIP case:
- if the received packet contains a control plane message other than the message of the Gateway Control and QoS Rules Provision procedure as specified in 3GPP TS 29.213 [21] clause 4.4.3 which results in the SGW to decide to deactivate an existing dedicated bearer, then the SGW may reject the message and shall continue maintaining the corresponding bearers. If the SGW receives another control plane message for an ARP value other than the ARP included in the Downlink Data Notification sent before, it shall proceed as specified in clause 5.3.4.3 "Network Triggered Service Request" of 3GPP TS 23.401 [15] with the exception that the message may be rejected by the SGW.
- if the received downlink packet contains the message of the Gateway Control and QoS Rules Provision procedure as specified in 3GPP TS 29.213 [21] clause 4.4.3 which results in the SGW to decide to deactivate an existing dedicated bearer, the SGW shall accept the message, and shall release the corresponding S5/S8 bearer(s) immediately.
The SGW may send the Downlink Data Notification message including the IMSI to the respective MME or S4-SGSN, if there is some DL data buffered for a UE when detecting the MME or S4-SGSN restart.
NOTE: For a UE using a power saving feature, DL data can be buffered for an extended duration in the SGW. The above requirement can allow the MME or S4-SGSN to restore the service to such a UE at the next occasion the UE becomes reachable. The SGW needs to pace the sending of Downlink Data Notification to the MME or S4-SGSN to avoid signalling storms over S11 and S4.
The SGW may send the Downlink Data Notification message to another MME or S4-SGSN (the same type of mobility node as the failed one) located in the same pool as the failed node if the SGW cannot send it to the failed MME or S4-SGSN (e.g. because it did not restart). It is an implementation/deployment matter how an SGW becomes aware that an MME/S4-SGSN has failed and has not restarted. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.2.3 MME/SGSN procedure | Upon receipt of a Downlink Data Notification message including the IMSI, the MME or S4-SGSN shall respond to the SGW with a Downlink Data Notification Acknowledge message and should page and force the UE to re-attach to the network. The paging area and subscriber's identity i.e. IMSI or S-TMSI/P-TMSI used during the paging procedure is implementation dependent. The MME or S4-SGSN may support and apply this procedure to a UE using extended idle mode DRX, and if so, they shall page the UE with the S-TMSI/P-TMSI.
NOTE 1: Upon receiving a page message with
- the IMSI, the UE starts the reattach procedure as specified in clause 5.6.2.2.2 of 3GPP TS 24.301 [19] and clause 4.7.9.1.2 of 3GPP TS 24.008 [20];
- the S-TMSI, the UE starts the service request procedure which is rejected by the MME with Cause #10 – Implicitly detached; the UE then re-attaches to the network as specified in clause 5.6.2.2.1 of 3GPP TS 24.301 [19];
- the P-TMSI, in case of Iu mode, the UE starts the service request procedure which is rejected by the S4-SGSN with Cause #10 – Implicitly detached; the UE then re-attaches as specified in clauses 4.7.9.1.1 and 4.7.13 of 3GPP TS 24.008 [20];
- the P-TMSI, in case of A/Gb mode, the UE sends any LLC frame and subsequently re-attaches to the network as specified in clause 8.1.4 of 3GPP TS 23.060 [5].
NOTE 2: Paging in the MME or S4-SGSN serving area will cause excessive use of radio resources. How to reduce the paging area is implementation dependent.
NOTE 3: It is the responsibility of the MME/S4 SGSN to avoid unnecessary IMSI Paging.
NOTE 4: How the restarted or alternative MME/S4-SGSN knows the UE's DRX parameter or the extended DRX parameters to page the UE is implementation dependent.
NOTE 5: A restarted MME will not receive S1AP UE Context Active message as part of UE initiated Connection Resume procedure, since the eNB would have deleted the AS context for all UEs associated with this MME after detecting the MME restart.
The MME or S4-SGSN may request the SGW to immediately release the maintained S5/S8 bearers by sending the "Downlink Data Notification Acknowledge" message or a "Downlink Data Notification Failure Indication" message with the specific cause "UE already re-attached", e.g. if the UE has already re-attached to the network. The Downlink Data Notification Acknowledge and Downlink Data Notification Failure Indication shall include the IMSI to identify the UE context in the SGW. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.3 Network triggered service restoration procedure with ISR | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.3.1 General | The following requirements shall apply if the involved MME, S4-SGSN and SGW support the ISR feature and the network triggered service restoration feature.
NOTE: The procedure in this clause does not consider the case where one of ISR associated nodes, i.e. the MME or the S4-SGSN, does not support the network triggered service restoration procedure.
In the rest of this clause, the term "non-failed" node refers to the CN node (MME or S4-SGSN) that remains in normal operation during this procedure, as opposed to the "restarted" node which refers to the CN node (MME or S4-SGSN) that has failed and restarted.
The procedure in the SGW towards the restarted node differs from the procedure towards the non-failed ISR associated node (see clause 25.3.2). |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.3.2 SGW procedure | If an SGW detects that an ISR associated CN node (i.e. MME or S4-SGSN) has restarted (see clause 18), the SGW shall maintain all the PDN connection table data and MM bearer contexts associated with the non-failed and the restarted ISR associated nodes, and start a timer controlling the maximum duration during which the SGW shall consider that ISR is still active. There is one operator configurable timer per SGW. The timer value may be set to a value that is the greater value of the periodic tracking area update timer (timer T3412) as specified in 3GPP TS 24.301 [19] and the periodic routing area update timer (timer T3312) as specified in 3GPP TS 24.008 [20]. This timer ensures that the SGW can still send Downlink Data Notification messages to the restarted MME or S4-SGSN until the corresponding UE learns that ISR is deactivated. If the timer expires, the SGW shall deactivate ISR by locally releasing the resources for the maintained restarted CN node (i.e. restarted CN node control plane F-TEID).
Upon receipt of the downlink user plane or control plane packet on a maintained S5/S8 bearer for a UE in idle mode or in connected state with the failed CN node, the SGW shall initiate the network triggered service request procedure towards the non-failed CN node as specified in 3GPP TS 23.401 [15] clause 5.3.4.3. In addition, if the S5/S8 bearer is eligible for network initiated service restoration, the SGW shall also immediately send a Downlink Data Notification message including the IMSI towards the restarted CN node as specified in clause 25.2.2. The SGW shall continue to forward downlink user plane or control plane packet for a UE in connected state in the non-failed ISR associated node.
The S5/S8 bearers eligible for network initiated service restoration are determined by the SGW based on operator's policy e.g. based on the QCI and/or ARP and/or APN.
Emergency PDN connections for users without authenticated IMSI do not need to be maintained by the SGW and cannot be restored at the initiative of the network.
NOTE 0: Users with an emergency call in progress can re-attach and re-establish the emergency PDN connection after detecting the loss of the signalling connection with the RAN. IMS Emergency PSAP callback is not supported for unauthenticated users with an emergency registration but without an emergency call in progress.
The SGW may send the Downlink Data Notification message with the IMSI to another MME or S4-SGSN (the same type of mobility node as the failed one) in the same MME or S4-SGSN pool if the SGW cannot send it to the failed MME or S4-SGSN (e.g. because it did not restart). It is an implementation/deployment matter how an SGW becomes aware that an MME/S4-SGSN has failed and has not restarted.
Upon receipt of a Downlink Data Notification message including the IMSI, the restarted CN node shall respond to the SGW with a Downlink Data Notification Acknowledge message and should page the UE and force it to re-attach to the network as specified in clause 25.2.
NOTE 1: If the UE camps under the service area of the restarted CN node, then the UE re-attaches to the network (see NOTE 1 in clause 25.2.3).
If the paging is successful (i.e. Modify Bearer Request is received) for the non-failed ISR associated CN node, the SGW may send a Stop Paging Indication message including the IMSI to the restarted CN node (or the alternative node in the same pool to which the Downlink Data Notification message with the IMSI has been sent before) to stop the paging procedure.
If the SGW receives a Create Session Request message as part of Initial Attach procedure for a UE for which the PDN connections, MM bearer context and ISR state have been maintained, the SGW shall stop the timer, deactivate ISR, and delete the maintained resources associated to the restarted CN node (i.e. CN node control plane F-TEID). The SGW may additionally send a Stop Paging Indication message to the non-failed ISR associated CN node to stop the paging procedure.
NOTE 2: The SGW may have already deleted the restarted CN node resources since Delete Session Request from non-failed ISR associated CN node may arrive earlier than the Create Session Request message.
If the non-failed ISR associated CN node received a Cancel Location message from HSS/HLR with "Initial Attach procedure" Cancellation Type, the non-failed CN node shall delete all the bearer contexts and send Delete Session Request message(s) to SGW. The SGW shall then release all the resources for this UE and sends one of the following messages to PGWs involved to release all the resources maintained in the PGWs as specified in 3GPP TS 23.401 [15] and 3GPP TS 23.402[18].
- For the GTP based S5/S8 case, Delete Session Request message(s)
- For the PMIP based S5/S8 case, PBU message(s) with Lifetime set to "0"
The SGW shall stop the timer and delete the resources for the maintained restarted CN node (i.e. restarted CN node control plane F-TEID) if it receives one of the following messages while the timer is running:
- a Modify Bearer Request message indicating that ISR is not active, e.g. from the non-failed CN node during a TAU/RAU procedure; or
- a Modify Bearer Request message indicating that ISR is active from another mobility management node with the same type as the restarted node. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 25.3.3 MME/S4-SGSN procedure | If an MME/S4-SGSN detects a restart of an ISR associated counterpart (see clause 18), the MME/S4-SGSN shall wait for the next RAU/TAU procedure to deactivate ISR.
NOTE: As an implementation option, an MME/S4-SGSN may internally mark the ISR as not active, but this should not be visible in messages sent to the SGW.
The non-failed CN node may initiate the GUTI Relocation or P-TMSI Relocation Procedure with a non-broadcast TAI or RAI to force the UE to perform the TAU/RAU procedure for ISR deactivation, e.g. if a signalling connection is established with the UE following receipt of a Downlink Data Notification message.
If afterwards the non-failed MME/S4-SGSN receives TAU/RAU Request, then the MME/S4-SGSN shall inform the UE in the TAU/RAU Accept message to disable ISR as specified in 3GPP TS 23.401[15] and 3GPP TS 23.060 [5]. The non-failed CN node shall send a Modify Bearer Request message to the SGW, even if the MME/S4-SGSN did not change during the TAU/RAU, to request the SGW to disable ISR and to update the SGW with the latest RAT Type and Serving Network values. Upon receipt of that message, the SGW shall disable ISR and shall stop sending Downlink Data Notification message with IMSI to the restarted CN node. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 26 Mobile terminated CS service delivery via an alternative MME in MME pool | This procedure is an optional feature for VLR and MME. It enables the network to continue delivering mobile terminated CS services to UEs via an alternative MME in the MME pool where the UE is located when the MME to which the UE was registered fails without restart or fails for a long duration.
NOTE 1: UEs in idle mode are not aware of an MME failure until they need to send some uplink data or signalling (e.g. a periodic Tracking Area Update) or until they are forced to re-attach e.g. via the network trigerred service restoration procedure. Without support of the procedure defined in this clause, UEs that remain under LTE may not be able to receive mobile terminated CS services for a long duration after an MME failure without restart or a long MME failure.
The following requirements shall apply if the VLR and MME support this feature.
When the VLR has to page the UE for a mobile terminated CS service (e.g. upon receipt of an incoming CS call), if the VLR detects that the MME serving the UE is no longer in service, the VLR should send an SGs paging request with a CS restoration indicator to one alternative MME in the same MME pool. The VLR should load-balance the paging requests among the available MMEs in the pool during the restoration procedure.
The VLR may know the set of MMEs pertaining to the same MME pool by local configuration or by checking the MME Group ID within the MME name that MMEs signal to the VLR in the SGsAP-LOCATION-UDATE-REQUEST, SGsAP-RESET-INDICATION or SGsAP-RESET-ACK messages. The MME should send an SGsAP-RESET-INDICATION message to the VLR after restart.
The VLR may detect that an MME is no longer in service if there are no more SCTP associations in service with that MME.
NOTE 2: Semi-permanent SCTP associations are established between the MME and VLR, i.e. the SCTP associations remain up under normal circumstances.
The VLR should adjust its paging retransmission delay to avoid requesting again the UE to re-attach before the restoration procedure completes.
The MME shall behave as specified in clause 14.1.3 upon receipt of an SGs paging request not including the CS restoration indicator.
The MME shall accept the SGs paging request and proceed as follows upon receipt of an SGs paging request including the CS restoration indicator:
- if the IMSI is unknown by the MME, or if the IMSI is known and the UE is marked as EMM-DEREGISTERED, the MME shall send the paging request with the location information provided by the VLR, regardless of the value of the "MME-Reset" indicator. If no such location information is provided, the MME may either page the UE in all the tracking areas corresponding to that MME or in the tracking areas served by the MME and by the VLR, or reject the paging request per operator policy. The paging request shall include the IMSI and the CN domain indicator set to "PS" to request the UE to re-attach;
- if the IMSI is known by the MME and the UE is considered to be attached to both EPS and non-EPS services or for SMS only (for an SGs paging request with an 'SMS indicator'), the MME shall page the UE based on the location information stored in the MME.
The MME may support and apply this procedure to a UE using extended idle mode DRX for MT-SMS service, and if so, the MME shall page the UE with the S-TMSI.
NOTE 3: How the alternative MME knows the UE's DRX parameter or the extended DRX parameters to page the UE is implementation dependent.
Upon receipt of a paging request including the IMSI and the CN domain indicator set to "PS", or upon receipt of a Service Reject with Cause #10 – Implicitly detached (when using S-TMSI paging), the UE re-attaches to one MME of the pool (that may not be necessarily the MME that initiated the paging procedure towards the UE) and a new SGs association is established with the VLR. This may be a different VLR than the VLR that initiated the SGs paging procedure, e.g. if Intra Domain Connection of RAN Nodes to Multiple CN Nodes is deployed for GERAN or UTRAN (see 3GPP TS 23.236 [24]).
NOTE 4: The UE can receive a Service Reject with Cause #10 – "Implicitly detached" upon being paged by an alternative MME with the S-TMSI assigned by the MME that has failed. The UE then re-attaches to the network as specified in clause 5.6.2.2.1 of 3GPP TS 24.301 [19].
If the new SGs association is established towards the same VLR, the VLR should repeat the SGs paging request after the UE has re-attached to non-EPS services. The MT CS service or SMS is then delivered according to normal procedures.
If the new SGs association is established towards a different VLR, the MT CS service may be delivered via the new VLR using Mobile Terminating Roaming Retry or Mobile Terminating Roaming Forwarding (see 3GPP TS 23.018 [23]); the on-going MT SMS is retransmitted by the SMS-SC using the existing SMS procedures (SMS alert).
Subsequent MT CS services are delivered as per normal procedures.
NOTE 5: A UE with ISR active before the MME failure and using GERAN or UTRAN radio access will not receive the paging request sent by the alternative MME. The VLR can deliver the MT CS service by paging the UE on the A/Iu interface as per existing principles of 3GPP TS 29.118 [14] when the UE does not respond to a first paging on the SGs interface. Paging the UE on the A interface fails if the network operates in NMO I and the UE is in PS connected mode in GERAN.
See 3GPP TS 29.118 [14] for a comprehensive description. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27 Restoration of PDN connections after an SGW failure | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.1 General | The procedures specified in this clause enable to restore in the EPC the PDN connections affected by an SGW failure with or without restart, and thus to resume delivery of downlink data towards the UE with minimum service interruption and with minimal signalling in the network.
All the procedures specified in this clause are optional to support.
The procedures specified in clause 27.2 apply to UEs for which ISR is not active when the SGW fails. The procedures specified in clause 27.3 apply to UEs for which ISR is active when SGW fails. The procedures specified in these clauses only apply to PDN connections established between MME/S4-SGSN and PGW pertaining to the same operator, i.e. for non-roaming and roaming scenarios with local breakout. The MME/S4-SGSN and the PGW shall behave as per the restoration requirements specified in clauses 14.1A.1 and 17.1A.1 for PDN connections established between nodes pertaining to different operators, i.e. as if the remote peer node does not support these SGW restoration procedures.
The procedures specified for an SGW in clauses 27.2 and 27.3 apply as well to an SGW-C. An SGW-C shall always apply in addition the related PFCP procedures towards the SGW-U.
NOTE 1: The applicability of these procedures is restricted to PDN connections established between MME/S4-SGSN and PGW pertaining to the same operator to ensure, simply by local configuration, that MME/S4-SGSN and PGWs apply the same logic i.e. same operator's policies when determining whether and which PDN connections should be restored. This enables to restore in particular IMS PDN connections (even in roaming scenarios, for which local break out is used).
NOTE 2: The use of these SGW restoration procedures may be extended by Service Level Agreements to PDN connections established between MME/S4-SGSN and PGW pertaining to different operators, i.e. for roaming scenarios with home routed traffic, but this is not further considered in 3GPP specifications. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2 Restoration of PDN connections after an SGW failure for UEs without ISR | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.1 General | The PGW triggered SGW restoration procedure is an optional add-on feature for the MME/S4-SGSN, SGW and PGW on top of the MME/S4-SGSN triggered SGW restoration procedure as specified in clause 27.2.2. A node that supports the PGW triggered SGW restoration procedure shall support the requirements specified in clause 27.2.2 and in clause 27.2.3. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.2 MME/S4-SGSN triggered SGW restoration | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.2.1 General | The following requirements shall apply if the MME/S4-SGSN, the SGW, the PGW, and the PCRF support this feature.
The MME/S4-SGSN, PGW, and PCRF for PMIP based S5, shall know by local configuration whether this MME/S4-SGSN triggered SGW restoration procedure is supported in the PLMN, i.e. by peer PGWs, PCRFs and MME/S4-SGSNs. The PGW shall assume that either all or none of the MMEs/S4-SGSNs in the PLMN support this procedure.Upon detecting an SGW failure with or without restart (relying on restart counter as specified in clause 18 "GTP-C based restart procedures" and clause 19 "PMIP based restart procedures", or implementation e.g. preconfigured path failure timer), the MME/S4-SGSN and PGW shall maintain the bearers and MM contexts of the PDN connections affected by the SGW failure and eligible for restoration, instead of removing associated resources as per procedures specified in clauses 14.1A.1 and 17.1A.1.
For PMIP based S5, when the PCRF detects an SGW failure or restart, the PCRF shall maintain the IP-CAN sessions and delete locally the Gxc sessions affected by the SGW failure.
NOTE 1: The PGW notifies the PCRF about the termination of IP-CAN sessions associated to PDN connections that are not restored by the MME/S4-SGSN within an operator configurable period.
The PDN connections eligible for restoration are determined by the MME/S4-SGSN and PGW based on same operator's policies, e.g. based on QCI, ARP and/or APN.
NOTE 2: The PCRF is not aware of which PDN connections are eligible for restoration. When the PGW detects an SGW failure, the PGW requests the PCRF to terminate IP-CAN sessions associated to PDN connections affected by the SGW failure and not eligible for restoration.
Maintaining the PDN connections affected by the SGW failure enables the MME/S4-SGSN to restore the corresponding bearers of the UE by selecting a new SGW or the restarted SGW. These PDN connections are maintained for an operator configurable period (T-Release-PDN timer), which is locally provisioned on MME/S4-SGSN and PGW, that by default should cover the periodic tracking area update timer (timer T3412) as specified in 3GPP TS 24.301 [19] or the periodic routing area update timer (timer T3312) as specified in 3GPP TS 24.008 [20]. After the expiry of the T-Release-PDN timer the MME/S4-SGSN and the PGW should delete any EPS bearer contexts that have not been restored via a new or the restarted SGW.
NOTE 3: The PGW's capability of supporting this SGW restoration procedure is stored per PDN and per UE by the serving MME/S4-SGSN. For a UE with multiple active PDN connections, some PGWs may support the SGW restoration procedure while others do not support the same. E.g. SGW restoration procedure may be supported for a PDN connection with local breakout while not supported for another PDN connection with home routed traffic. The restoration procedures upon SGW failure specified in clauses 14.1A.1 and 17.1A.1 apply to the PDN connections for which the SGW restoration procedure is not supported or not applicable. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.2.2 MME/S4-SGSN procedure | After detecting an SGW failure, the MME/S4-SGSN should attempt to restore the PDN connections eligible for restoration for all the UEs affected by the SGW failure, i.e. including UEs in ECM_IDLE / PMM-IDLE / GPRS STANDBY not engaged in any Service Request, or Connection Resume procedure or other mobility procedure. The MME/S4-SGSN shall control the pace of the SGW relocations to avoid core network node overload. The MME/S4-SGSN should prioritize the SGW relocation for UEs engaged in a Service Request, or a Connection Resume, or RAU/TAU procedures or having GBR bearers over UEs which are not engaged in any mobility procedure and that do not have a signalling connection to the MME/S4-SGSN nor GBR bearers. The MME/S4-SGSN should also prioritize the SGW relocation for UEs with an emergency PDN connection.
The MME/S4-SGSN may further prioritize the PDN connections to restore, e.g. for UEs ECM_IDLE / PMM-IDLE / GPRS STANDBY not engaged in any Service Request or Connection Resume procedure, based on operator's policy e.g. based on the QCI and/or APN. Besides, the MME/SGSN may use the subscribed Restoration Priority per APN, if received from the HSS, and if permitted per service level agreements for in-bound roamers, to determine the relative restoration priority among PDN connections to the same APN. The MME/SGSN may use a locally configured value as default restoration priority if the restoration priority for a user's PDN connection is not received from the HSS or not permitted by service level agreement for in-bound roamers.
NOTE 1: This is to allow all the affected UEs to be reconnected to the network in a relatively short time (that is function of the speed of the SGW relocations that the MME/S4-SGSN performs, based on implementation and the network load) so that downlink packets may be delivered to the UEs with minimum service interruption.
NOTE 2: Prioritizing the restoration of emergency PDN connections can enable to preserve emergency calls in progress for authenticated and unauthenticated users, and enable PSAP to call back authenticated users with an emergency registration but without an emergency call in progress.
NOTE 3: The Restoration Priority can e.g. allow to restore with a higher priority users with an IMS voice subscription over IMS users without an IMS voice subscription.
To restore the PDN connection(s) of a UE, the MME/S4-SGSN shall perform an SGW relocation procedure by sending a Create Session Request message (per PDN connection to restore) to the new or restarted SGW as per the steps 8-11 of a Tracking Area Update procedure with Serving GW change in clause 5.3.3.1 in 3GPP TS 23.401[15]. For PDN connections with GBR bearers existing before the SGW failure, the MME/S4-SGSN may either request to restore or remove the GBR bearers in the Create Session Request (e.g. depending on how quickly the PDN connection is restored). The MME/S4-SGSN shall restore the PDN connections of the affected UEs after the SGW failure as follows:
1) for UEs in ECM_IDLE/PMM-IDLE/GPRS STANDBY state:
- the MME/S4-SGSN shall select a new SGW or the restarted SGW based on the last visited TAI/RAI. When Dedicated Core Networks are deployed, the UE Usage Type shall also be used for the SGW selection as specified in 3GPP TS 29.303 [37];
- the MME/S4-SGSN shall then perform an SGW relocation procedure as specified above.
2) for UEs in ECM_CONNECTED/PMM-CONNECTED/GPRS READY state not engaged in any mobility procedure (TAU/RAU, Handover):
- the MME/S4-SGSN shall release the S1/Iu/radio resources; if the eNodeB/RNC detects the SGW failure, the eNodeB/RNC may request the MME/S4-SGSN to release the S1/Iu resources;
- the MME/S4-SGSN shall then handle these UEs as specified for UEs in ECM_IDLE/PMM-IDLE/GPRS STANDBY state, or for UEs performing a mobility procedure if the UE performs subsequently such a mobility procedure (e.g. a Service Request to re-establish the S1/Iu/radio bearers);
- as an exception to these rules, for UTRAN without direct tunnel and GERAN, the S4-SGSN may perform SGW relocation while keeping the UEs in PMM-CONNECTED/GPRS READY state (i.e. without tearing down the Iu/radio resources) because S4 user plane is used and the SGW failure remains not visible to the radio network.
NOTE 4: An SGW failure with restart may be visible to the radio network and cause bearers to be released for bearers with on-going uplink traffic if an Error Indication is received from the SGW before the S4-SGSN detects the SGW restart.
3) for UEs in ECM-IDLE/PMM-IDLE/GPRS STANDBY state initiating a Service Request procedure or a Connection Resume procedure:
- the MME/S4-SGSN shall first perform the SGW relocation procedure as specified above and then continue with the Service Request or the Connection Resume procedure since the MME/S4-SGSN has no valid SGW F-TEID to send in the S1-AP Initial Context Setup Request towards the eNodeB or in the Iu RAB Assignment Request message towards the RNC if Direct Tunnel is used.
4) for UEs initiating an intra-MME or intra-S4-SGSN TAU/RAU procedure:
- the MME/S4-SGSN shall perform the SGW relocation procedure as specified above before the TAU/RAU procedure;
5) for UEs initiating an inter-MME/SGSN TAU/RAU procedure:
- If both the source and target MME/S4-SGSNs support this SGW restoration procedure, the source MME/S4-SGSN should indicate to the target MME/S4-SGSN in the GTPv2 Context Response message that an SGW relocation procedure is needed due to an earlier SGW failure. Upon reception of such indication, the target MME/S4-SGSN shall perform the SGW relocation procedure as specified above and then proceed with the TAU/RAU procedure. The source MME/S4-SGSN may perform the SGW relocation procedure as specified above before responding to the GTPv2 Context Request message if the target MME/S4-SGSN does not support the SGW restoration procedure, e.g. during inter-PLMN RAU/TAU procedures when the target PLMN does not support the SGW restoration procedure.
6) for UEs in ECM-CONNECTED/PMM-CONNECTED/GPRS READY state for which a handover procedure is initiated:
- The source MME/S4-SGSN should reject the Handover Required / Relocation Required message received from the RAN (for UEs with PDN connection(s) affected by an earlier SGW failure that have not been restored yet); the MME/S4-SGSN should then release the S1/Iu/radio resources of these UEs to force them to enter idle mode. The MME/S4-SGSN shall then proceed with the procedures specified above for UEs in ECM_IDLE/PMM-IDLE/GPRS STANDBY state, or for UEs performing a mobility procedure if the UE performs subsequently such a mobility procedure (e.g. a Service Request to re-establish the S1/Iu/radio bearers).
NOTE 5: S1/Iu/radio resources of UEs in ECM-CONNECTED/PMM-CONNECTED/GPRS READY state affected by an SGW failure are released very shortly after the SGW failure. Therefore only very few UEs affected an SGW failure and with PDN connections not restored yet may be subject to a handover, e.g. handovers taking place just after the SGW failure before the eNodeB/RNC or the MME/S4-SGSN release the S1/Iu/radio resources. This is why it is not necessary to support SGW relocation during Intra/Inter-CN handover procedures.
After detecting a combined SGW/PGW failure, the MME/S4-SGSN behavior shall be same as in the case when an MME/S4-SGSN receives the optional PGW Restart Notification message. Either of the following shall apply:
- MME/S4-SGSN behavior is determined by clause 16.1A.2 "PGW Failure";
- PDN connections can be restored by the MME (this does not apply to S4-SGSN), as specified in clause 31.3 "MME triggered PDN connection restoration". |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.2.3 PGW procedure | The PGW shall maintain the PDN connections affected by the SGW failure and eligible for restoration for an operator configurable period (T-Release-PDN timer), as specified in clause 27.2.2.1.
The PGW should maintain the GBR bearers of the PDN connections eligible for restoration for an operator configurable period (T-Release-GBR), which should be much shorter than the T-Release-PDN timer. Upon expiry of the T-Release-GBR timer, the PGW shall release GBR bearers that have not been restored yet and inform the PCRF about the corresponding PCC rule inactivation, with a cause as specified in 3GPP TS 29.212 [25].
NOTE: This is a safeguard mechanism to avoid e.g. overcharging the user in IMS for sessions not already terminated by IMS (e.g. by the far end user of a VoIP call).
The PGW shall discard downlink packets received for a PDN connection maintained after an SGW failure that has not been restored yet.
The PGW shall stop charging for PDN connections maintained after an SGW failure which have not been restored yet.
If the IP-CAN Session Modification Request is received for a PDN connection maintained after an SGW failure but not restored yet, the PGW shall reject the request if the request contains the installation/modification of PCC rules and other policy decisions (e.g. change of APN-AMBR), however the P-GW shall accept to remove the PCC rule if the removal of PCC rules is included in the request. The PGW shall accept an IP-CAN Session Modification Request if it only includes the removal of PCC rules. Refer to 3GPP TS 29.212 [25] clause B.3.14 for the detail. For these IP-CAN sessions for which an IP-CAN session modification has been rejected, the PGW shall subsequently inform the PCRF when the PDN connection is restored as specified in clause B.3.14 of 3GPP TS 29.212 [25]. This would enable the PCRF to update the PCC rules in the PGW if necessary. After the PDN connection is restored, the PGW shall initiate the bearer modification/deactivation procedure if necessary to modify or remove the resources associated with the PCC rules that were removed during the SGW failure.
The PGW shall accept an IP-CAN Session Termination Request received for a PDN connection maintained after an SGW failure but not restored yet, with an acceptance cause as specified in 3GPP TS 29.212 [25] and release the affected PDN connection locally. If subsequently the MME/S4-SGSN attempts to restore the PDN connection, the PGW shall reject the Modify Bearer Request (for GTP based S5) or the Proxy Binding Update (for PMIP based S5) with the cause "Context Not Found" as specified in 3GPP TS 29.274 [13] and 3GPP TS 29.275 [16] after the corresponding PDN connection has been released locally. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.2.4 PCRF procedure | If the PGW rejects an IP-CAN session modification procedure with the rejection cause as specified in clause 27.2.2.3, the PCRF should maintain the corresponding IP-CAN session and refrain from sending any further IP-CAN session modification request to the PGW until being notified by the PGW that the PDN connection is restored.
For PMIP based S5, the PCRF cannot send any message to the SGW once the Gxc session in the PCRF is removed. The PCRF may however behave as for GTP based S5, e.g. send signalling to the PGW via the Gx interface. The Gxc session is restored when the PCRF receives Gateway Control Session Establishment from the SGW as specified in 3GPP TS 29.212 [25]. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.2.5 SGW procedure | After the SGW restarts, the SGW shall not send Error indication message for a configurable period when the SGW receives a GTP-U PDU for which no Bearer context exists.
NOTE: The period needs to be longer than the time required for the peer node to detect the restart of the SGW, e.g. the interval between two echo request messages. This ensures that the MME/SGSN or PGW does not deactivate the bearers before it detects the SGW failure and triggers the restoration procedure. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.3 PGW triggered SGW restoration | |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.3.1 General | The following requirements shall apply if the MME/S4-SGSN, the SGW and the PGW support this feature.
NOTE: The PGW triggered SGW restoration procedure does not require any further requirements from the PCRF than those already specified for the MME/S4-SGSN triggered SGW restoration procedure in clause 27.2.2.1.
The PGW shall know by local configuration whether this PGW triggered SGW restoration procedure is supported in the PLMN. The MME/S4-SGSN/SGW may know the same by local configuration. When supported in the PLMN, the PGW supporting this procedure should be configured with the address of alternative(s) SGW(s) also supporting this procedure. The PGW shall assume that either all or none of the MMEs/S4-SGSNs in the PLMN support the procedure. All MMEs/S4-SGSNs in an MME/S4-SGSN pool should support this procedure when it is deployed.
The PGW triggered SGW restoration procedure does not apply to emergency PDN connections for users without authenticated IMSI.
NOTE: The MME/S4-SGSN can prioritize the restoration of emergency PDN connections (see clause 27.2.2.2). IMS Emergency PSAP callback is not supported for unauthenticated users with an emergency registration but without an emergency call in progress. |
88525ca373d6c27ca925fc02f42c683a | 23.007 | 27.2.3.2 MME/S4-SGSN procedure | During normal mode of operation (i.e. before SGW failure with/without restart):
The MME/S4-SGSN supporting the PGW triggered SGW restoration procedure shall include the MME/S4-SGSN identifier IE in existing signalling over the S11/S4 interface, i.e. in
- Create Session Request messages during an E-UTRAN Initial Attach, a UE requested PDN connectivity, and a PDP Context Activation procedure;
- Create Session Request message during TAU/RAU procedures with a SGW change;
- Create Session Request message during X2 based handover/Enhanced SRNS Relocation procedure with a SGW change;
- Modify Bearer Request message during Inter-RAT Handover procedures with/without a SGW change;
- Modify Bearer Request message during Intra-RAT handover procedure with a SGW change;
- Modify Bearer Request message during Inter-RAT TAU/RAU procedures without a SGW change;
- Modify Bearer Request message over S11/S4 if the message is deemed to be sent to the PGW due to other reasons, e.g. reporting ULI, time zone.
During SGW restoration procedure:
Upon receipt of a PGW Downlink Triggering Notification message for which it cannot find a UE context corresponding to the received IMSI, the MME/S4-SGSN shall send a PGW Downlink Triggering Acknowledge message with the rejection cause code "Context Not Found" to the SGW to inform the SGW that the PGW Downlink Triggering Notification message has been received by the MME/S4-SGSN. If the PGW Downlink Triggering Notification message contains an MME/S4-SGSN identifier, the MME/S4-SGSN shall also include the IMSI and the MME/S4-SGSN identifier in the PGW Downlink Triggering Acknowledge message.
Upon receipt of a PGW Downlink Triggering Notification message for which it can find a UE context corresponding to the received IMSI, the MME/S4-SGSN shall send a PGW Downlink Triggering Acknowledge message back to the SGW with an acceptance cause code, and perform S-TMSI/P-TMSI paging as part of Network Initiated Service Request procedure as specified in clause 5.3.4.3 of 3GPP TS 23.401 [15] and in clause 6.12.1A of 3GPP TS 23.060 [5]. When receiving a Service Request message from the UE, the MME/S4-SGSN shall perform the SGW restoration procedure as specified in the clause 27.2.2 with the addition that the MME/S4-SGSN shall include the MME/S4-SGSN identifier IE in the create session request message. |
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