H.323 trunk ringback problem

Hello.

 

We have a problem with one of our h323 customers. The connection is of GW-GW type.

 

The diagram is as following:

 

Softswitch ---- SBC ---- Cisco2811

 

Calls, which goes from SSW to customer's Cisco2811, do not have ringback tones, only silence and normal voice session as soon as customer picks up the phone.

 

The dump shows that Cisco sends Alerting message without Progress indicator information to SBC, but the SBC forwards this Alerting with Progress indicator present.

 

I need to force the SBC to tell the Softswitch to provide ringtones for calling party. Unfortunately Progress indicator is described only in IWF applications in Configuration guide.