-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Scott Lawrence
Sent: Friday, December 11, 2009 2:48 PM
To: Mark Gertsvolf
Cc: sipX-dev
Subject: Re: [sipX-dev] SIP trunk gateway selection by sipXbridge

On Fri, 2009-12-11 at 17:11 -0500, Mark Gertsvolf wrote:
> This post is in reference to http://track.sipfoundry.org/browse/XX-7235
> 
> sipXecs dial plan logic is implemented in sipXproxy. sipXbridge
> maintains ITSP accounts (SIP trunk gateways) and it is in charge of the
> ITSP account selection when handling outgoing calls.
> Even though sipXproxy dial plan logic knows the ITSP account (SIP trunk
> gateway) chosen for a particular call it does not tell sipXbridge
> explicitly what the account is. Instead it sets the domain name in R-URI
> and also sets the CallerID ("from" header) before sending the request to
> sipXbridge.
> 
> In order to find the right ITSP account sipXbridge looks at the target
> domain in R-URI and finds the ITSP account with matching domain. If
> there are multiple ITSP accounts with the same domain the "from" header
> is used for disambiguation.
> 
> This mechanism to signal the choice of ITSP account from sipXproxy to
> sipXbidge is not sufficiently reliable. It breaks when multiple accounts
> exist with the same target domain name and when an external caller is
> making a call, which is routed to sipXbridge. In case where the caller
> is external sipXproxy CallerAlias plugin refuses to manipulate the
> CallerID and the disambiguation of the ITSP accounts does not work.
> 
> It is not totally clear to me why CallerAlias does not manipulate
> CallerID for external callers, but regardless, it seems that the current
> communication mechanism between the dial plan logic and sipXbridge is
> not good enough.
> 
> I think a better mechanism is required to communicate the ITSP account
> information to sipXbridge rather then letting it guess which account to
> use.
> In the past similar communication details have been sent between sipXecs
> components via proprietary headers. Is there a room for another such
> header (something like: X-Sipx-itsp-account) to communicate the ITSP
> account name to sipXbridge.
> 
> Comments?

I'd like to start with a question... 

What is the point of having multiple ITSP 'accounts' to the same domain?
What is different about them and why do they exist?

(more on some of the details above later - there are some good questions
there, but I've got to go off line now)



An example of multiple ITSP "Accounts" to the same domain.   

System installed for one company that sublets some of their empty office
space, however, the sublets need trunks for their own set of billing
requirements.  One way to handle is separate domain names if the ITSP
supports this, but if they don't, then you need a method of identifying
calls from one group of users to use one specific group of trunks for
billing purposes.

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