Missed call communication protocol

Richard Bennett richard.bennett at skynet.be
Wed Feb 7 15:51:35 CET 2007

On Wednesday 07 February 2007 15:08, Rodney Arne Karlsen wrote:
> Hi there
> While you can choose your callerID when using a sip server, it may not stay
> the way you set it once it passes through the PSTN gateway. I tried playing
> with CallerID stuff some time back here in South Africa and our PSTN
> provider will only allow you to set your caller ID to a number that is
> assigned to the line you are using. If you are lucky enough to have a PRI
> line then you start with around 100 numbers.
> Sorry to throw a spanner in the works but I'm not sure that this will work
> here. It may work in other countries. I think I heard about it working in
> the US.

True that can be an issue. 
There are however many carriers that are used for wholesale termination (as 
opposed to VOIP collecting). They generally offer 2 service levels, premium 
and second quality. In second quality they will often not pass any CLIs on, 
but the premium quality lines are supposed to pass on all CLIs, as long as 
they are valid e164 numbers.
So we need a bit of research to find out which SIP termination companies pass 
on the CLI as sent.
This is not something your average end-user would setup themselves, but it is 
something that could be easily setup as a service, you could compare it to 
setting-up a VOIP gateway, and doesn't cost anything to run really, as no 
calls are actually connected.

I'll put together a test server for us to experiment with, once I have a 


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