[SR-Users] R-URI for ACK

[David Wilson]

Hello All,

I’m trying to interop with a provider whose ACK during an inbound call seems to be misrouted.

During the INVITE, OK, ACK handshake, my understanding (which matches the examples in RFC 3665) is that the R-URI in the ACK should be the Contact specified in the 200 OK.  

I have also found multiple discussions that imply that this is necessary.  However, I can’t find a convincing normative reference for this...  Is there a reference (ideally in RFC 3261) that makes this clear?

Cheers,
Dave.