[{"name":"SP-240556","title":"LS from CT WG4: LS on Subscription of UPF event via I-SMF","source":"CT WG4","contact":"Bruno Landais","contact-id":68755,"tdoctype":"LS in","for":"Information","abstract":"CT WG4 has the following observations on CR 23.502 #4786 rev.3 (S2-2405685) agreed at SA WG2#162 (April 2024). The CR enables the anchor SMF to subscribe to I-UPF events via the I-SMF by extending the Nsmf_PDUSession API (anchor SMF initiated Update Request towards I-SMF) with the UPF event subscription related information. CT WG4 understands that this approach would require adding to the Nsmf_PDUSession API (in the anchor SMF initiated Update Request and Response) all the information and mechanisms defined in the Nupf_EventExposure to support subscribing to UPF events, modifying the subscription, unsubscribing from those events, including signaling the (successful or unsuccessful) response back to the anchor SMF. Lots of attributes of the Nupf_EventExposure would need to be duplicated in the Nsmf_PDUSession API. A potential alternative solution not impacting the Nsmf_PDUSession API could be to require the anchor SMF to invoke the Nsmf_EventExposure service produced by the I-SMF (see below), to request the I-SMF to subscribe to the I-UPF events as specified in clause 4.15.4.5 of TS 23.502 and clause 5.34.7.2 of TS 23.501. {. . .} CT WG4 would like SA WG2 to clarify: a) whether they considered both approaches above, and if so, on which criteria should the anchor SMF invoke the Nsmf_PDUSession API vs. the Nsmf_EventExposure to subscribe to UPF events via the I-SMF? b) whether the anchor SMF should be able to determine if the requested UPF events\/service are supported by the I-SMF\/I-UPF, before triggering a subscription towards the I-SMF, and if so, how. c) whether the anchor SMF may need to subscribe to UPF events at the ULCL\/BP and\/or at the local PSA UPF; d) how to support subscriptions at the anchor SMF targeting ANY UE, e.g. ANY UE in a specific area, e.g. whether the anchor SMF should determine by itself the UEs present in the specific area and trigger then subscriptions, per PDU session, for the corresponding UEs?","secretary_remarks":"Related to SA WG2 CR Pack SP-240581. Noted","agenda_item_sort_order":9,"ainumber":"2.1","ainame":"Incoming LSs - proposed to note","tdoc_agenda_sort_order":10060,"status":"noted","reservation_date":"2024-05-21 14:11:30","uploaded":"2024-06-04 04:48:49","revisionof":"","revisedto":"","release":"Rel-18","crspec":"","crspecversion":"","workitem":"","crnumber":"","crrevision":"","crcategory":"","tsg_crp":"","lsreplyto":"","lsto":"SA WG2","Cc":"TSG SA, CT WG3","lsoriginalls":"C4-242333","lsreply":"","link":"https:\/\/www.3gpp.org\/ftp\/TSG_SA\/TSG_SA\/TSGS_104_Shanghai_2024-06\/Docs\/SP-240556.zip","group":"SP","meeting":"SP-104","year":2024,"uicc_affected":"","me_affected":"","ran_affected":"","cn_affected":"","clauses_affected":"","crsinpack":null,"crsinpacknumber":0}]