[Asterisk-Users] Forwarded call flag

[Peter Svensson]

On Tue, 8 Mar 2005, Tom Samplonius wrote:

> On Tue, 8 Mar 2005 13:36:39 -0700, Dr. Matthew Roller
> <matthewroller at gmail.com> wrote:
> > When I forward my PSTN phone(Qwest) to my cellphone and someone calls
> > it, my cellphone(AT&T) shows an arrow next to the caller id showing it
> > is a forwarded call, is there any way to set that forward flag when
> > forwarding a phone call through asterisk?
> 
>   It is possible using PRI signalling (ni2 for sure).  When running
> q931 debugging on a PRI gateway, I can see that incoming calls that
> have been forwarded actually have the redirecting number listed, and
> the type of redirection (always, na/busy, etc).  I really doubt that
> libpri has the capability to build these kinds of messages, let alone
> an API to set the fields.  And then try to find a PRI provider won't
> strip the messages (called GTD, if you talk to them).

There are several possible fields in isdn for this (isn't isdn great? ;-).
Some of these can be set in libpri, some can not. 

 * using Call Deflection on the isdn link before answering. Possible with 
   bristuffed versions of Asterisk.
 * using Explicit Call Transfer for an answered call. Same as above.
 * possibly using Redirecting Number, if your telco allows that from
   the user to the network.
 * Using the "special arrangement" option of ETS 300 092-1 paragraph 9.4 
   and Annex B. This allows the sending of two Calling Party Number 
   elements, one of which can be set arbitrarily to the caller id of the 
   forwarded call. This seems to be available all over Europe at least. 
   Support is being added to Asterisk by Frank Sautter.
 * Using ROSE invokes for Diverting Leg Information. Already in libpri.

Peter