Given the case where local transport is unable to send a request due to the failure in establishing the connection to the next hop, the condition must be treated as 503 (Service Unavailable) status code. But there is a requirement that transaction layer must submit an ACK for this response as stated in RFC3261, Section 17.1.1.1 Overview of INVITE Client transaction:
When in either the "Calling" or "Proceeding" states, reception of a response with status code from 300-699 MUST cause the client transaction to transition to "Completed". The client transaction MUST pass the received response up to the TU, and the client transaction MUST generate an ACK request, even if the transport is reliable (guidelines for constructing the ACK from the response are given in Section 17.1.1.3) and then pass the ACK to the transport layer for transmission. So in the case where local transport has failed, there is no point in submitting an ACK request to the local transport as the 503 response was received due to the failing local transport. How would you suggest to approach this situation? Would this be something implementation specific? Thank you, Brez _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
