SIP-to-SIP T.38 on only one call leg

[budmiller]

We are designing a solution to do faxing over a SIP trunk however we have learned from the provider that their SIP switch does not support T.38.  Would it be possible to terminate the SIP trunk from the provider on a Cisco gateway (2911) and form another SIP trunk between the gateway and the Rightfax with T.38 enabled?  I have looked for documentation on this but haven't seen anything specifying one way or another.

Any help is greatly appreciated.

Thanks,

Bud

[Steven Holl · Accepted solution]

budmiller wrote:
Would it be possible to terminate the SIP trunk from the provider on a Cisco gateway (2911) and form another SIP trunk between the gateway and the Rightfax with T.38 enabled?
Thanks,
Bud

No way to currently do this.  It would be nice to be able to invoke a transcoder and convert pass-through to T.38, but it would require some significant enhancements on the transcoder side on the GW and in CCM.

The only way to do it is to loop the calls through a T1 looped back to the same router, and make sure calls to the fax number loop through this.  It's not a clean design.

New versions of the Brooktrout driver support g711 passthrough.  You may consider investigating that, and forcing g711 on the calls to the fax server.

Or, get a provider that supports T.38.  ;-)

[budmiller]

Thank you Steven.  Very helpful!