An initiutive explanation could be that, since a CANCEL may be sent out before receiving a '180 Ringing' route headers cannot be present in the CANCEL. Between the time an INVITE is sent out and the receipt of response from the remote end, there is no route-set (it can only be formed when a response from the remote end is recd). Therefore a CANCEL must rely on a mechanism separate from the route headers thus forcing incomplete transactions in the proxy to keep track of the next hop to which the request was sent.
>Vikram, > >If the proxy is stateful, then the transaction state >tells the proxy where >it sent the request. The proxy will have one or more >client transactions >associated with a server transaction (See Figure 3 in >section 16.2 of >bis-05). A stateful proxy must retain these until the >transaction completes. >If the transaction has completed, then the CANCEL is >too late and does not >need to be forwarded. >cheers, >(-:bob Robert F. Penfield Chief Software Architect Acme Packet, Inc. 130 New Boston Street Woburn, MA 01801 [EMAIL PROTECTED] __________________________________________________ Do You Yahoo!? Send your FREE holiday greetings online! http://greetings.yahoo.com _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
