System enhancements for the use of IP Multimedia Subsystem (IMS) services in local breakout and optimal routeing of media
This study intends to investigate the general problem of system enhancements for the use of IMS services in local breakout and optimal routeing of media.
In particular the above issues will be addressed identifying
- solutions for the home operator to control
- whether the IMS user may connect to a PDN in the visited network, and
- whether connections to PDNs provided from the home and visited network may exist in parallel;
- solutions to enable the IMS network to be aware of whether local breakout can be invoked or not;
- solutions to allow the home operator to determine which of the IMS sessions (for a given UE) can be handled in local breakout and which in home routed mode, and what information (e.g. operator's policies, customer's subscription profile, UE connectivity, and location of the remote end terminal/service) is needed for the decision;
- solutions to allow the UE to concurrently use IMS services through local breakout and other IMS services through home routeing;
- the feasibility of having the local breakout option in IMS service nodes:
- is there a need for a P-CSCF at both PDN accesses?
- if one P-CSCF is enough, what requirements are there for connectivity between the PDNs?
- if methods are necessary to discover an additional P-CSCF in the visited network after the UE has moved to the visited network, even if the network-layer mobility mechanisms can sustain IP connectivity to the previously discovered P-CSCF in the home network;
- the exact location of the decision point in the home network whether to use local breakout (application or delegated to IP-CAN);
- solutions for SIP/SDP signalling related to the use of IMS services through local breakout.
- interactions with network entities such as NAT (as specified in TS 23.228 [8]) when providing IMS services through local breakout;
- interactions with and support of PCC to provide IMS services through local breakout;
- security implications if there is need for multiple P-CSCFs per UE.
Moreover:
- describing a set of scenarios where the selection of an alternative media path (i.e., different to the signalling path) provides benefits to IMS operators by reducing the number of network entities in the media path;
- providing requirements for suitable mechanisms to achieve optimal media routeing;
- analysing the potential solution(s) to solve those scenarios in line with IMS procedures, while taking into account any impact of extensions required to existing functions/procedures (e.g., NAT, transcoding, Security, PCC, BCF, LI, etc.);
- reducing the number of options for solving the same requirement and agree on a preferred solution.
In the end this study will provide conclusions with respects to what further specification work is required in order to fulfil the requirements for the use of IMS services through local breakout and achieve optimal routeing of media.