Hi All, SBC has a call for the our phone, which is behind a NAT with the pinhole kept open by fast registers.
SBC sends out an INVITE my phone replies with a 180, with 100rel required and an RSeq: 81 SBC send back a PRACK to which the phone sends 200 OK. 20 seconds later I still hasn’t picked up. According to RFC 3581 which handles NATs “the binding may expire before a final response is received. To keep the binding fresh, the client SHOULD retransmit its INVITE every 20 seconds or so. These retransmissions will need to take place even after receiving a provisional response.” So SBC retransmit the original INVITE. This is where things start to go awry. SBC retransmits original INVITE My Phone replies with a 180, with 100rel required and the exact same Rseq: 81 The SBC discards this message as the Rseq has not been incremented. This is from RFC 3262 “The value of the RSeq in each subsequent reliable provisional response for the same request MUST be greater by exactly one.” But since this is not truly a new request we have received, we are not sending an increased RSeq. I believe we are correct in this behaviour but how can we elicit a response from the SBC. Do we expect a new PRACK..? RFC 3262 also says that a UAC SHOULD NOT retransmit the PRACK request when it receives a retransmission of the provisional response" Also I want to tell you that our phone does not support RFC 3581. Is phone behavior justified? What should phone need to do here? Thanks, Isshed. _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
