All, RFC3261 Section 16 states the following regarding Proxy Behavior:
Being a proxy is a logical role for a SIP element. When a request arrives, an element that can play the role of a proxy first decides if it needs to respond to the request on its own. For instance, the request may be malformed or the element may need credentials from the client before acting as a proxy. The element MAY respond with any appropriate error code. When responding directly to a request, the element is playing the role of a UAS and MUST behave as described in Section 8.2. Please consider the following call flow scenario: OUA sends INVITE to Proxy Proxy sends 100 Trying to OUA Proxy routes INVITE to SBC SBC sends 100 Trying to Proxy SBC routes INVITE to TUA SBC does not receive 100 Trying from TUA and retransmits INVITE several times OUA sends CANCEL to Proxy Proxy responds to CANCEL with 200OK Proxy routes CANCEL to SBC SBC does not route CANCEL to TUA A CANCEL timer on Proxy pops and Proxy sends 487 for INVITE request to OUA Several seconds elapse and Timer B pops on the SBC and it sends a 408 back to the Proxy for the INVITE request The proxy does not ACK the 408 response; therefore, the SBC retransmits the 408 for 64*T1 seconds Note: The SBC is acting as a proxy and not a B2BUA Question: Is the proxy behaving correctly by sending the 487 response to the INVITE request on its own? Regards, Tina Iliff _______________________________________________ Sip-implementors mailing list Sip-implementors@cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
