Hi Linda, Sorry for the late response.
Juniper Business Use Only From: Linda Dunbar <[email protected]> Sent: Thursday, August 1, 2024 8:19 PM To: Jeffrey (Zhaohui) Zhang <[email protected]>; [email protected] Cc: [email protected] Subject: questions about draft-zzhang-dmm-5gdn-end-marker [External Email. Be cautious of content] Jeffrey, When a UE moves from gNB1 to gNB2, I thought the End Marker from gNB1 is sent to UPF (instead of being sent to the gNB2 as described in you draft). Is it correct? Zzh> 23.501 only talks about who sends the end marker, so I did a google search and here is the result: ------------ AI Overview: In a 5G mobile network, an end marker is used to preserve the order of packets during a handover between Access Nodes (ANs). When a mobile device (UE) moves from one AN to another, the User Plane Function (UPF) sends an end marker to the source AN after sending the last packet over the old tunnel. The source AN then redirects the inflight packets to the target AN, which buffers the data until it receives the end marker. The target AN then forwards the buffered and new data to the UE. ------------ For the distributed UPFs, when a UE moves from UPF1 to UPF2, UPF1 and UPF2 might have different public IP addresses. How does PE be able to handle the End Marker? Is it necessary for PEs (which are on N6 interface) to even care? Zzh> Using the example of DL traffic via the hub PE, and assuming that the reordering issue needs to be handled (if we don't care about the reordering issue then it is a moot point). Zzh> UPF1 does not know that the hub PE switched the UE route to the UPF2 so it would not send out the end marker w/o the new procedures in this document. It needs a trigger from the hub PE (when the hub PE changes the UE route to via UPF2) so the PE needs to care even though it is not part of the 5GS. The trigger is an ICMP message addressed to the UPF1 (not PE1) address. This UPF address can be piggy backed when the UPF initially announced the UE routes. Zzh> Thanks. Zzh> Jeffrey Thank you. Linda
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