[Serusers] Bug # 2925

[Jiri Kuthan]

At 08:45 AM 4/20/2005, Juha Heinanen wrote:
>Jiri Kuthan writes:
>
> > In case people do keep asking: it is really so, and receivers
> > MUST be able to deal with ACK branch different from branch
> > in INVITE.
>
>that is correct.
>
> > >The bug report is invalid, ignore it. branch=0 in ACK to a 200
> > >is perfectly valid according to RFC3261. 
>
>but i'm not sure that branch=0 would be valid according to rfc3261,
>which says (section 8.1.1):
>
>The branch parameter value MUST be unique across space and time for all
>requests sent by the UA.
>
>0 thus hardly qualifies. also
>
>The branch ID inserted by an element compliant with this specification
>MUST always begin with the characters  z9hG4bK.

Actually you are right syntactically. I don't think there is a point
semantically -- branch id is used to provide uniqueiness to
a) identify request retransmission (not applicable to ACK) 
and 
b) match replies to requests (not applicable to ACK either).

-jiri