Hi, section 14.2 (UAS Behavior) of RFC3261 states the following: "A UAS that receives a second INVITE before it sends the final response to a first INVITE with a lower CSeq sequence number on the same dialog MUST return a 500 (Server Internal Error) response to the second INVITE and MUST include a Retry-After header field with a randomly chosen value of between 0 and 10 seconds."
I have a question about the "with a lower CSeq sequence number" part. Is that about the first INVITE or the second INVITE? For example: INVITE (CSEQ 1) <--- 180 RINGING (CSEQ 1) ---> INVITE (CSEQ 2) <--- 500 SERVER INTERNAL ERROR (with Retry-After header) (CSEQ 2) ---> ACK (CSEQ 2) <--- or: INVITE (CSEQ 3) <--- 180 RINGING (CSEQ 3) ---> INVITE (CSEQ 2) <--- 500 SERVER INTERNAL ERROR (with Retry-After header) (CSEQ 2) ---> ACK (CSEQ 2) <--- Because the second case doesn't make sense to me, because when the UAC would retry the INVITE would be rejected again because of the lower sequence number. -- kind regards, Sigrid Thijs _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
