> From: Iñaki Baz Castillo [i...@aliax.net] > > > And the SIP > > element can process a set of incoming requests in any order it > > chooses, because the sender has no way to tell how the network may > > have reordered the requests (for UDP anyway). > > But if the UAC sends OPTIONS (Cseq 10) followed by INFO (Cseq 11), and > OPTIONS arrives later than INFO, the UAS would reply 500 due to the > Cseq value (minor than the last received).
That's true, but you diagrammed the messages as arriving in-order. The risk of the requests being processed out-of-order (and hence one of them receiving a 500 respone) is why UAs rarely send a request while another request is outstanding. > > I assume you mean "a non-100 1xx response", as a 100 response is not > > end-to-end and Alice won't receive it. > > Right, sorry, I should print 180 or whatever but 100. "1xx" is usually sufficient. > >> 3) IN-DIALOG-1 = INFO, IN-DIALOG-2 = OPTIONS > >> > >> And here? > > > > In this case, the diagram is incorrect, because non-INVITE requests > > can never generate 1xx responses. > > But they do... sometimes :) > > > Without the 1xx response, Bob can > > pretend to have received IN-DIALOG-1 and IN-DIALOG-2 in whichever > > order he chooses. But his responses must be consitent with one > > request being fully processed before processing of the other request > > starts. (One case causes the second request to receive a 500 > > response.) There is a difficulty if a non-INVITE transaction sends a 1xx response. Once Bob sents the 1xx response to a request, Bob has committed to having received the request, and Bob is committed to *when* he has received the request. (If Alice receives the 1xx response before she sends her second request, she *knows* that Bob received the second request after receiving the first request, and must (in theory) have processed the two requests in order. The consequence is that if Bob sends a 1xx response to a non-INVITE request, Bob must then complete that request before starting to process any request that arrived after the 1xx was sent. Bob cannot pretend to have received them in the reverse order. Dale _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
