Report of sa wg2 meeting #114

Discussion and conclusion:

Postponed TD S2 154274 from meeting #112. Response drafted in TD S2 160588 (withdrawn). This LS was postponed to meeting #114.

TD S2 160588 [DRAFT] Reply LS on SIP deregistration in GERAN and UTRAN (no VOPSSI).

Discussion and conclusion:

Response to TD S2 160024. This was not provided and was withdrawn.

TD S2 160202 LS from CT WG1: LS on CT1 view on LS on SIP deregistration in GERAN and UTRAN (no VOPSSI). (CT WG1)
Abstract: CT WG1 has discussed an incoming LS from GSMA NG RiLTE on 'SIP deregistration in GERAN and UTRAN (no VOPSSI)' and wants to provide CT WG1 view to SA WG2. CT WG1 decided not to send an outgoing LS to GSMA NG RiLTE but rather to provide our view to SA WG2 such that SA WG2 will send a consolidate 3GPP view to GSMA. CT WG1 has the following comments on the proposal from GSMA NG RiLTE which requires the UE to perform a SIP deregistration when moving out of E UTRAN coverage and into either GERAN coverage or UTRAN coverage not indicating VOPSSI:
1. UE may do cell reselection and quickly move back to E-UTRAN. So sending the
deREGISTER would be followed by REGISTER, hence causing additional signalling.
The new initial REGISTER would require authentication, which includes several
messages and would cause processing load on P-CSCF, I-CSCF, S-CSCF and HSS. In
addition initial Filter Criteria have to be processed an 3rd party REGISTER to be sent to
AS.
2. According to current standards, when UE goes from E-UTRAN to UTRAN/GERAN, the
UE can perform re-registration (to change capabilities), can perform de-registration (if
UE wants to do so) or can do nothing. It is UE implementation specific which of those
options the UE chooses.
Action: CT WG1 asks SA WG2 group to discuss the CT WG1 view on 'SIP deregistration in GERAN and UTRAN (no VOPSSI)'. If seen appropriate please include the CT WG1 view in the outgoing LS to GSMA NG RiLTE.