School of Specs 23.501v20.2.0

3GPP 23.501 v20.2.0 — the document's own text

5.37.9.4 Usage of UDP Option transferring media related information over N6

Taught in 23. Very fast, very reliable, very picky (The 5G system architecture, in depth).

The mechanism described in this clause uses connect-udp in tunnel mode for On-path N6 signalling to establish a UDP tunnel between the UPF as HTTP/3 client and the AS as HTTP/3 proxy according to clause 5.37.9.2 to securely transfer media related information. This clause defines the differences with the mechanisms defined in clause 5.37.9.2 when media related information is carried over UDP Option.

The media related information is encoded into UDP-Option as defined in IETF RFC 9868 [202] and transferred through the UDP tunnel over N6, in which the inner UDP datagram contains end-to-end encrypted XRM media packet between AS proxy and UE and the outer UDP datagram between AS proxy and UPF contains UDP-Option carrying media related information (see Annex W).

NOTE 1: The UDP option kind value and the format of the media related information carried by the specific UDP-Option and exchanged between the UPF and the AS proxy are defined in TS 29.561 [132]).

The usage of UDP-Option transferring media related information over N6 is supported as defined in clause 5.37.9.2 with following differences:

  • When the AF provides On-path N6 signalling information for connect-udp, it may also provide an indication of UDP-Option in Protocol Description for transferring media related information. This is to instruct the PSA UPF that the media related information is carried in UDP-Option in UDP datagram over N6.
  • The inner UDP datagrams contain the unmodified payload for both UL and DL traffic and the media related information is included in the UDP option of the DL outer UDP datagram.
  • The UPF supports the HTTP/3 Client functionality for negotiation of security keys used for encrypting media related information carried in the UDP-Option. The UPF shall remove the UDP-Option carrying media related information before forwarding the XRM media packets over right PDU Session towards the (R)AN and the UE.

NOTE 2: Protection of Media related information when using UDP Options is defined in TS 33.501 [29].