Re: [Sip] Dual registration without Outbound

[Iñaki Baz Castillo <ibc at aliax.net>]

El Martes, 7 de Octubre de 2008, Paul Kyzivat escribió:
> The question is: why would a *single* UA establish two distinct contacts
> and register them for the same AOR?

I don't know if the following is used, but I've been thinking about it:

A PBX (a UA with AoR sip:ua at domain.org) has two PSTN numbers asigned in its 
SIP provider/registrar:

1) +34111111
2) +34222222

Imagine it just creates a registration with:
  Contact: <sip:ua at UA_IP>

Then when the proxy receives a call for +34111111 or +34222222 it will 
transform the RURI into:
   INVITE sip:ua at UA_IP SIP/2.0

So how could the UA know which number was dialed? Note that reading the "To" 
header is not valid since the call could has been previously forwarded.


But now imagine that the UA uses two registrations, the first one with:
  Contact: <sip:+34111111 at UP_IP>
and the second with:
  Contact: <sip:+34222222 at UP_IP>

So if the proxy receives a call for +34111111 it could select the location of 
UA matching the username, and the UA would know which PSNT number was used.


Anyway I don't know how "llegal" is selecting an AoR location based on 
the "Contact" username.


-- 
Iñaki Baz Castillo
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