4.12 Multiple PDN Support

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

General high level principles for the support of multiple PDNs are provided in TS 23.401 [4], clause 5.10.1. In addition, the following applies:

– Simultaneous exchange of IP traffic to multiple PDNs is supported in the EPS, when the network policies, non-3GPP access and user subscription allow it. UE Support for multiple overlapping IP address spaces is optional.

– Multiple PDN connections for a given APN and UE can be supported with the restrictions that all PDN connections for a given APN and UE shall use the same access network and shall all be moved to a new access network during handovers.

– If an additional PDN connection to the same APN occurs, and an existing PDN connection to that APN exists, the same PDN GW shall be selected.

– Multiple PDN connections to different APNs may use different access networks. The UE selects the access network where to route a specific PDN connection based on user preferences and operator’s policies.

– A UE that is capable of routing different simultaneously active PDN connections through different access networks can do so if the UE is authorized by subscription to access each of the involved PDNs and each of the involved access networks.

– The access networks the UE can stay simultaneously connected with shall include no more than one 3GPP access and one and only one non-3GPP access.

NOTE: During the handover procedure the UE moves the PDN connections one-by-one, but the selective handover of the PDN connections to the same APN is not supported.

Once a specific IP mobility protocol is selected during initial attach for a specific non-3GPP access, it is not possible for the UE to use different mobility protocols for any of the PDNs that it obtains connectivity on the same non-3GPP access after initial attach. It is not possible for a UE that is connected to multiple PDNs over a 3GPP access to perform a handover to a non-3GPP access and then use different mobility protocols for the various PDNs that it connected with on the same non-3GPP access.

For the purpose of using MAPCON, the UE shall try to simultaneously connect to different APNs through different access networks only if the home network supports such simultaneous connectivity. The UE determines that the network supports such simultaneous connectivity over multiple accesses if the UE is provisioned with or has received per-APN inter-system routing policies (see clause 4.8.2.1) from the home network.