On 11/29/2010 11:06 AM, Alex Balashov wrote:
> On 11/29/2010 10:44 AM, Ali Kemal MAYUK wrote:
>
>> I am investigating about how Centrex work with SIP. If an enterprise
>> customer has a 2 different locations, how they call each other with short
>> numbers(4 digit) ? Which SIP headers are used for it? Is there a
>> standartization ? Does any one have a solution documentation? How the big
>> companies handle it?
>
> This is not a question about SIP protocol mechanics or implementation,
> although you may not know that.
>
> Your question is about an abstraction of SIP endpoint behaviour
> (initiating calls between two or more endpoints) to serve the needs of a
> high-level application and/or marketable product. There is nothing
> special whatsoever about how "Centrex"-like products are implemented
> using SIP endpoints, nor any specific accommodation for this kind of
> functionality within the protocol.
>
> Your real question is, "How do I dial between SIP endpoints using
> arbitrary routing designations?"
good restatement
> The answer is: the same way you'd
> dial in any other scenario. As usual, the dialed digits are present in
> the Request URI and (usually) the To header.
There are at least two answers (probably more):
- as you state, R-URI contains dialed digits. Some server acting on
behalf of caller translates this into a more complete one - e.g. E.164
format - and then routes appropriately.
- the calling phone may be provisioned with enough of the dial plan so
that *it* can expand the dialed digits into a complete URI for the
called party, then sends the INVITE.
Thanks,
Paul
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