[Asterisk-Users] ISDN transfer, handoff to masterswitch

[Peter Svensson]

On Wed, 4 May 2005, Alex Mack wrote:

> I've setup * with a Junghanns.net QuadBRI card agaisnt an Ericsson 
> MD-110 PBX. All four ISDN channels are setup to simulate  EuroISDN 
> Point-to-Point ("Anlagenanschluss" in Germany) from the Ericsson's side. 
> Works well and I have had little problems at all.
> 
> Now what's happening during a call transfer of an ISDN call to another 
> ISDN destination? Does such a transfer block 2 b-channels (one in and 
> one out)? Or is it automatically handed off to the Ericsson so * is out 
> of the loop? Is EuroISDN capable of such a handoff? Or do I have to use 
> another protocol like Q.SIG for that feature?

In EuroISDN this functionallity is provided by ECT (Explicit Call
Transfer) for established calls and CD (Call Deflection) for calls in the 
setup phase. Bristuff supports these according to the documentation.

Q.SIG has one (or possibly several) ways of doing this. At least one of 
these have been implemented in libpri. 

> I don't have experience with Q.SIG at all. I was happy * worked with the 
> EuroISDN trunk so well. But there's the issue with congestioning the 
> link to the PBX with too many (in my case 4) forwarded calls.
> 
> Does anyone have experiences with this? Are there references for Q-SIG 
> out there?

I think at least some of the standards are published at
http://www.ecma-international.org/activities/Communications/QSIG_page.htm

Peter