Anita Tailor wrote:
Hi All,I have some queries related to expires header in SIP message./RFC 3261 Section 20.19/// /" The value of this field is an integral number of seconds (in decimal) between 0 and (2**32)-1, measured from the receipt of the request"/Does this mean 0 is a valid value of Expires header ? I am confused because of "between" word here as meaning might different if "from 0 to (2**32)-1" have used.
Its certainly valid in *some* contexts. For instance in REGISTER and SUBSCRIBE this is the way to terminate a registration or subscription.
Does Expires value in INVITE is modified by intermittent SIP entities before it reaches to its destination?
According to table 2 of 3261, proxies are not permitted to add, modify, or delete this header. But of course a B2BUA can do as it wishes.
If yes, then what should be UAS behavior when it receives INVITE with value 0 in Expires header ? Should UAS respond with 487 ?/Section 13.1.1 [1]/ / "If the request is an INVITE that contains an Expires header field, the UAS core sets a timer for the number of seconds indicated in the header field value. When the timer fires, the invitation is considered to be expired. If the invitation expires before the UAS has generated a final response, a 487 (Request Terminated) response SHOULD be generated."/
The above is SHOULD strength. I expect you will find many UAs that don't bother with this.
But if you are implementing the UAS, this would be a good thing to do. There is no point in establishing a session if the caller no longer wants it.
Paul _______________________________________________ Sip mailing list https://www.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use sip-implementors at cs.columbia.edu for questions on current sip Use sipping at ietf.org for new developments on the application of sip