[Sipping] Request / Response (RPC-like) exchange in SIP?

Hey all,

Is there any interest now or has there been discussion in the past on a
SIP extension that supports a request/response (RPC-like) dialog? If so,
would someone be willing to summarize the outcome of such a discussion.  

What I'm thinking is a SIP method that could be used to construct a simple
Request/Response dialog between two endpoints. In principal, I suppose it
could be designed to support a more extended dialog of request/response
messages, but a single request/response would be the norm. 

The intent would be to provide SIP with a mechanism for doing a kind of
RPC, very much the way Web-services based architectures use HTTP GET/POST
dialogs to implement an RPC mechanism.

I know this may sound like heresy, but my desire for such a mechanism is
based on the utility of RPC within the context of a SIP service control
network. That is, for certain types of services there are times when you
want to do an RPC-like request/response transaction from one endpoint to
the other (e.g., perhaps to perform a commercial service purchase
transaction between two parties). In a converged services framework, say
based on SIP, it'd be convenient to be able to do this with SIP, rather
than via some other (parallel) signaling protocol (e.g. web-services), so
that the service signaling can a) be managed by a single protocol and b)
travel a common signaling path for the purposes of service tracking and
settlement.   ..hence my question.

I can imagine trying to use existing SIP mechanisms for this purpose, such
as Subscribe/notify, info, or message, but none of these seems designed
for this purpose.

So what do people think about an RPC-like request/response mechanism for
SIP?

Oh wait a second.... 

........... ok, I've got my fire retardant suit on.... 

... flame away!

-Steve

_______________________________________________
Sipping mailing list  https://www1.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use sip-implementors@cs.columbia.edu for questions on current sip
Use sip@ietf.org for new developments of core SIP