[cisco-voip] QSIG over H323 with GK

[James Brown]

All,

We have an opportunity to convert some existing QSIG E1 tie-lines 
(between TDM PBXs) to IP and at the same time allow our UCM cluster to 
reach the PBX sites. I wondered if anyone could spare a few minutes to 
advise me on the implementation please?

My preferred setup would be:

UCM H225 Trunk <--> GK <--> H323 IOS GW <--> TDM PBX

The reason I like H323 in this instance is that this environment 
includes four separate PBXs and I'd like to keep the old dial-plan away 
from UCM and use GK CAC. The PBXs are various Nortel models and I 
believe the IOS H323 implementation may offer slightly more flexibility 
when integrating.

Having read around the topic, it seems that UCM supports ISO QSIG 
whereas IOS supports ECMA QSIG. To make matters worse, UCM tunnels QSIG 
over H323 using Annex M, while IOS uses the GTD field within a GKTMP 
message.

Could anyone tell me whether a Cisco GK could successfully reconcile 
what looks like a different versions of QSIG and different tunnelling 
mechanisms please? Is the approach I'm taking valid, or would I be 
better using MGCP? Does anyone have any experiences they could share 
when integrating with a Nortel Option 61/81 with QSIG?

Many thanks,

James.