Technically, you can send the ACK with either TCP or UDP. >From RFC 3261, you can use UDP upto a certain message size:
If a request is within 200 bytes of the path MTU, or if it is larger than 1300 bytes and the path MTU is unknown, the request MUST be sent using an RFC 2914 [43] congestion controlled transport protocol, such as TCP. If this causes a change in the transport protocol from the one indicated in the top Via, the value in the top Via MUST be changed. This prevents fragmentation of messages over UDP and provides congestion control for larger messages. However, implementations MUST be able to handle messages up to the maximum datagram packet size. For UDP, this size is 65,535 bytes, including IP and UDP headers. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Andrey Kovalenko Sent: 31 July 2008 08:35 To: [email protected] Subject: [Sip] Route header and transport Hello. I have following problem: For example, UAC decides to send INVITE via TCP transport and does it like so: INVITE sip:[EMAIL PROTECTED] SIP/2.0 Call-ID: e271e3d45ca69c0a CSeq: 1 INVITE From: "user" <sip:[EMAIL PROTECTED]>;tag=1e5f7ab5 To: <sip:[EMAIL PROTECTED]> Via: SIP/2.0/TCP 192.168.1.4:5060;branch=z9hG4bKce32ffc97438620028ba85a78311d3cb Max-Forwards: 70 Contact: <sip:[EMAIL PROTECTED]:5060> Content-Type: application/sdp Content-Length: 227 Then OK is receivied and it looks like so SIP/2.0 200 OK Via: SIP/2.0/TCP 192.168.1.4:5060;branch=z9hG4bKce32ffc97438620028ba85a78311d3cb;received =192.168.1.4 Record-Route: <sip:88447-212.53.40.72.dialog.cgatepro;lr>,<sip:212.53.40.72:5060;lr>,< sip:212.53.40.40:5060;lr> From: "user" <sip:[EMAIL PROTECTED]>;tag=1e5f7ab5 To: <sip:[EMAIL PROTECTED]>;tag=000000000518036-57737A9D_lnqxjfk-660DE7A8 Call-ID: e271e3d45ca69c0a CSeq: 1 INVITE Contact: <sip:[EMAIL PROTECTED]> Supported: 100rel,timer,replaces,histinfo User-Agent: CommuniGatePro-callLeg/5.2.6 Allow: INVITE,ACK,BYE,CANCEL,OPTIONS,INFO,MESSAGE,SUBSCRIBE,NOTIFY,PRACK,REFER Content-Type: application/sdp Content-Length: 193 Then ACK is sent to URI that is defined in Contact header: ACK sip:[EMAIL PROTECTED];transport=tcp SIP/2.0 Via: SIP/2.0/TCP 192.168.1.4:5060;branch=z9hG4bKca9dbdeb9f803d0cdba2c2124abd9440 CSeq: 1 ACK From: "user" <sip:[EMAIL PROTECTED]>;tag=1e5f7ab5 To: <sip:[EMAIL PROTECTED]>;tag=000000000518036-57737A9D_lnqxjfk-660DE7A8 Call-ID: e271e3d45ca69c0a Supported: 100rel,timer,replaces,histinfo User-Agent: CommuniGatePro-callLeg/5.2.6 Allow: INVITE,ACK,BYE,CANCEL,OPTIONS,INFO,MESSAGE,SUBSCRIBE,NOTIFY,PRACK,REFER Max-Forwards: 70 Route: <sip:212.53.40.40:5060;lr>,<sip:212.53.40.72:5060;lr>,<sip:88447-212.53. 40.72.dialog.cgatepro;lr> Contact: <sip:[EMAIL PROTECTED]:5060> Content-Length: 0 Should this ACK be sent via TCP or UDP, whether URI in Route header does not explicitly defines transport? -- Best regards, Andrey mailto:[EMAIL PROTECTED] _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
