D Quality of Service 10 03 00 00 10 81 06 3e 39 80 21 10 04 00 00 10 00 00 00 00 00 03 10 20 Text item (text), 25 bytes Packets: 1633 Displayed: 1633 Marked: ( Figure 4.13 A captured End User Address information element carrying GTPv1 IP addressing information of IPv4v6 PDP Type (unknown to Wireshark version used for capturing). The PDP Type numbering follows the PPP Data Link Layer Protocol Numbers Internet Assigned Number (IANA) registry (See http://www.iana.org/assignments/ppp-numbers.) for IPv4 and IPv6. However, there is no suitable value defined by the IETF for PDP Type IPv4v6, thus 3GPP has allocated its own value 0x8D (in hexadecimal) to it. The PDP Type Organization could also be the European Telecommunications Standards Institute (ETSI) in addition to IETF, but none of the protocols under the ETSI PDP Type Organization have ever been very popular, and are not even used anymore in EPS, thus we can safely always assume IETF as the organization for protocol definitions. On GTPv1 signaling, the IID part of the IPv6 address has no meaning, other than historically. (Full IPv6 addresses are exchanged in the signaling due the early sup- port for Legal Interception (LI) in SGSNs.) Only the prefix has significance, and it is notable that the prefix length is assumed to be /64. There is no separate field for a prefix length. IPv6 in 3GPP Networks Regarding the IPv6 addresses, they are full addresses containing both prefix, which is fixed to /64, and a 64-bit IID selected by the GGSN (or under some cases by the PGW). PDP Context Information Element The PDP Context information element may be present in both SGSN Context Response and Forward Relocation Request GTPv1 messages that are used during the inter-SGSN Routing Area Update (RAU) and inter-Radio Access Technology (RAT) handover and the related context transfer. The PDP Context information element contains user plane IP address information within the PDP Address field. Either IPv4 or IPv6 address can be included in the PDP Address field. Prior to 3GPP Release-9 