[SIPForum-techwg] Question re Application Server

[Chris Sibley]

Hi Paul,

Firstly, my apologies for taking so long to respond. I have been on
vacation and it's taken a while to dig myself out.

Secondly, thanks for your very astute comments! You are quite right
that, given the current wording, calls between Enterprises (handled by
the SP) would require a B2BUA. When this text was written, we were
(only) contemplating calls that ORIGINATED from the PSTN and were
destined to an Enterprise. So, in this scenario, since the headers are
actually being created for the first time the text would be correct.

However, as you pointed out, there is certainly significant value in the
SP handling calls BETWEEN Enterprises. That said, I think we need to
clarify Section 13 to define rules for calls that originate from the
PSTN (current wording) as well as calls that originate from another
Enterprise (and handled by the SP, of course). 

What do you think? If everyone agrees I can put together something today
/ tonight and send it out for your review..

Thanks,

--Chris


> -----Original Message-----
> From: techwg-bounces at sipforum.org [mailto:techwg-bounces at sipforum.org]
On
> Behalf Of Paul Kyzivat
> Sent: Friday, September 01, 2006 1:41 PM
> To: SIP Forum Tech WG
> Subject: [SIPForum-techwg] Question re Application Server
> 
> I am trying to understand the nuances of draft 5, and there is
something
> I am unsure of: Is the Application Server required to act as a B2BUA,
or
> is it permitted to act as a proxy? There is no mention of B2BUAs in
the
> document, but I think it may be implied.
> 
> In particular, suppose we have one service provider servicing two
> enterprises: acme.com and bozo.com.
> 
> Acme has a phone number +12125551234, and Bozo has +14085556789. Then
> Acme calls Bozo. According to the spec, the call from Acme is
addressed
> as:
> 
> 	INVITE sip:+14085556789 at serviceprovider.net;user=phone SIP/2.0
> 	To: <sip:+14085556789 at serviceprovider.net;user=phone>
> 	From: <sip:+12125551234 at acme.com;user=phone>
> 
> But then the instructions for service provider addressing say that
when
> this is sent to Bozo that it should be addressed as:
> 
> 	INVITE sip:+14085556789 at bozo.com;user=phone SIP/2.0
> 	To: <sip:+14085556789 at bozo.com;user=phone>
> 	From: <sip:+12125551234 at serviceprovider.net;user=phone>
> 
> To change the To and From fields in this way requires that the
> Application Server be a B2BUA. If this is routed using proxy routing,
> then the message going to Bozo would perhaps look like:
> 
> 	INVITE sip:+14085556789 at bozo.com;user=phone SIP/2.0
> 	To: <sip:+14085556789 at serviceprovider.net;user=phone>
> 	From: <sip:+12125551234 at acme.com;user=phone>
> 
> So, is it a requirement to have a B2BUA in the path, or is proxy
routing
> ok?
> 
> 	Thanks,
> 	Paul
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