Why do you want to turn SIP into an authorization service? Why wouldn't the actual proxy use something like a web service or other data query/response mechanism to ask your server what to do with the call?
Are you anticipating deploying this in an IMS environment? If so, an application server can do what you want. In an non-IMS environment, every server implementation I've seen has some way to access an external authorization mechanism of one kind or another. That would be proprietary, but probably still the most appropriate response. If you WANT to be on the call path, then you have a real proxy server, and your proxy server would just respond with a redirect. I presume that "denial" is actually redirect to some announcement generator, so it's always a redirect one way or another. Brian _____ From: McFarland, Keith A. [mailto:[EMAIL PROTECTED] Sent: Tuesday, August 21, 2007 7:34 PM To: [email protected] Subject: [Sip] SIP Recommended Call Flows for an MVNO? All, I have been reviewing SIP documents at IETF and have come to the conclusion that there is not an exact recommended procedure to cover my desired use of the SIP implementation. As you can tell from my email address I am the voice architect at Virgin Mobile USA, LLC. I am currently, considering future implementations to interface with our prepaid rating engine. As part of this consideration I am evaluating leapfrog to IP call control versus an evolution within SS7. My preference is to move to SIP if possible. However, in an MVNO the use of SIP would vary slightly from the current best practices. I would envision the SIP proxy to be replaced with a SIP 3rd Party Call Authorization and Control Server. This 3rd Party server does not sit in the middle of the SIP call flow (as does a proxy or 3pcc) but sits off to the side and other proxies (MSC or PSTN switches, in this case they act as SIP gateways) would call out to this 3rd party SIP server to get direction on voice call treatment. This call treatment could include just simple authorization to proceed, denial, redirection with or without special treatment etc. What I am trying to find is a best practices to cover this scenario. Perhaps it exists and you could just help me out by pointing me to the best practices document. If it doesn't, what are our options to go down the path to develop one? We are willing to move forward with an implementation of this but would prefer to do so with the support of a best practices or recommended practices from IETF. Having this would obviously benefit our efforts as we would have to work with multiple switch vendors for any modifications. Obviously, it would be more advantageous to these vendors to implement this if it is based off of recommended practices as the resale potential goes up. Appreciate your time, Keith A. McFarland Voice Architecture Manager Virgin Mobile USA, LLC 925-457-6536
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