> Am I correct in thinking that the PBX should > be sending an ACK to the 200 OK not the proxy?
I don't understand that sentence; but it sounds like the answer is no. Within your original question, the PBX and proxy both added Record-Route entries (as shown within copied 200 OK snippet). The phone builds the ACK with a Route based upon those Record-Route entries (I'm assuming that the PBX in the example behaves as a proxy). The phone sends ACK to PBX; PBX adjusts/sends ACK to proxy; proxy adjusts/sends ACK to SBC. The 200 OK from the SBC is formatted as such: SIP/2.0 200 OK Via SIP/2.0/UDP <PROXY IP> Via: SIP/2.0/TLS <PBX IP> Via: SIP/2.0/TLS <Phone IP> From: "SIP Phone" IP To: <sip:destination at SBC IP> Call-ID Cseq: 1 INVITE Record-Route <sip:111151bc at PROXY IP:5060;transport=udp;lr> Record-Route: <sip:PBX IP:5061;transport=tls;lr> Accept: application/sdp, application/isup, application/dtmf, application/dtmf-relay, multipart/mixed Contact: <sip:number at SBC IP:5060> _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
