Klaus, CANCEL is hop-by-hop only in stateful processing and in this case, yes, it has only on VIA. But if you have stateless processing, CANCEL is end-2-end and it will have multiple VIAs... Does 3665 obsoletes stateless SIP or it is just not covering it??? regards, bogdan Klaus Darilion wrote: > Looks like it is defined clearly and openser is not 100% standard conform. > > regards > klaus > > fancy wrote: > > >> Hi Klaus: >> RFC 3665 page 54 line 4: >>

>> A CANCEL constructed by a >> client MUST have only a single Via header field value matching the >> top Via value in the request being cancelled. >> >> and RFC 3665 at page 53: >>

>> CANCEL is referred to as a "hop-by-hop" request, since it is >> responded to at each stateful proxy hop. >> >> and RFC 3665 at page 21: >>

>> Client: A client is any network element that sends SIP requests >> and receives SIP responses. Clients may or may not interact >> directly with a human user. User agent clients and proxies are >> clients. >> >> So, for my opinion, the role of proxy in this case of RFC 3665 section 3.8 is a client when it sends CANCEL message to Bob. >> >> If I misunderstand any RFC meanings, please correct me. >> Thank you very much. >> >> Best Regards, >> Fangyu Ling >> >> >> >> >>> fancy wrote: >>> >>> >>>> According to RFC 3665 section 3.8 and RFC 3261 section 9, >>>> there is only one via header in CANCEL message >>>> (message F11, F13 at page 72 of RFC 3665). >>>> >>>> >>> Hi! >>> >>> I could find it in RFC 3665, but not in 3261. Where exactly in RFC 3261 >>> is mentioned that the CANCEL has only 1 Via header? >>> >>> Further, the example has only one Via header - but I could not find any >>> definition if this is a MUST or not. >>> >>> >>> >>>> How can I remove the 2nd via header? >>>> >>>> >>> You would have to modify tm module and change the code which generates >>> the CANCEL message. >>> >>> regards >>> klaus >>> >>>