As its name implies, a transaction stateful proxy maintains state associated with a single transaction. Once the transaction is complete, it does not maintain any information about the dialog and generally does not need to stay in the signaling path for subsequent messages.
A call stateful proxy maintains state for the duration of the dialog. It therefore needs to receive all subsequent requests and responses that are related to the session. This can be accomplished using the Record-Route and Route headers. Note that a call stateful proxy is still just a proxy server. A request goes in one side of a proxy and out the other. Both requests are associated with the same dialog. The proxy is also bound by the rules that the protocol places on proxy servers (e.g. they cannot originate new requests autonomously). UAC <--- d1 ---> Proxy <--- d1 ---> UAS A B2BUA is a concatenation of a user agent server and a user agent client. A request goes into a B2BUA and the UAS component terminates that dialog. The UAC component of the B2BUA forwards the requests out on a different dialog. The B2BUA is not limited in the same way that proxy servers are. They can, for example, originate new requests autonomously, for example to end the call. UAC <--- d1 ---> B2BUA <--- d2 ---> UAS Much has been written about proxy servers and B2BUAs and their similarities and differences. Search the sip-implementors archives for more details. -- Gary Cote www.awardsolutions.com _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
