Transfer call to server B and drop channel on server A


We have a limited amount of G729 licenses per server. We need to transfer some calls to the IVR server for customer satisfaction surveys as self service.

The problem comes in that even if the call is transferred to the IVR server and the work is being done there, the channel is still open on the original inbound server. (Meaning the channel between the SIP provider and the server still points to inbound server instead of IVR server).
Is there a way to transfer the call and have the channel open between SIP provider and IVR server, and drop the channel pointing to the original inbound server ?

Theoretically, yes: you transfer the call. At the moment you are probably relaying it.

However, it is unlikely that an ITSP would honour a transfer, and if they did, they would probably charge you for the call between your two machines.

If you can avoid tone generation, recording, whispering, conferences, and transcoding, you can operate G.729 in pass through mode, without any licences.

There is slightly more chance that your ITSP will accept direct media re-invites, which will allow you to relay just the signalling. Note that various features (e.g. anything that requires recording or mid-call DTMF detection) will inhibit this. Most ITSPs probably don’t permit direct media re-invites.

Note that the transfer application is relatively little tested and may still be fragile in error cases.

Hi David,

Ok, G729 licenses aren’t exactly expensive, so as per your explanation the best option will be then to just relay the call and have an overhead of licences on the server from which the call originates.

Thanks for this! :smile: