alok> what are the pitfalls of sending the acknowledgment directly
alok> to the caller??? (callee know the ip address of the caller
alok> by now!!!
vkg> There aren't any pitfalls, per se. SIP supports either of
vkg> the modes. There may be certain services which require all
vkg> signaling information to pass through the service elements.
bob> Besides the requirement that the appropriate path (Via for
bob> resonponses and Record-Route+Contact for the ACK) be followed,
bob> the problem is that the intervening proxies will have state
bob> about the transaction. The messages must traverse the path
bob> so that the proxies can cleaup the state.
This does bring up an interesting point -- if a UAC decides NOT
to honor the R-R by creating a Route set, then what Bob describes
above will occur, namely proxies may retain transaction state.
But, from the protocol point of view, a proxy cannot force the
UA to create a route set from the R-R's. If the UA insists on
not creating a route set from R-Rs (which is a MUST now), then
it is not compliant to the spec. Things were murky with RFC
2543 on creating Route sets from R-R's, but are spelled out
much more clearly in -09bis.
Regards,
- vijay
--
Vijay K. Gurbani vkg@{lucent.com,research.bell-labs.com,acm.org}
Internet Software and eServices Group
Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
Naperville, Illinois 60566 Voice: +1 630 224 0216 Fax: +1 630 713 0184
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