The T.38 Fax Fallback to G.711 feature provides the functionality for enterprise networks managed by Communication Manager to interoperate with older Verizon networks that do not support T.38 Fax for fax transport. A new codec type, T.38 Fax with Fallback to G.711 Pass-Through, is added to the IP codec set for Fax mode.

T.38 Fax Fallback to G.711 operates in the following way:

• The call connection is signaled for a standard T.38 fax relay.

• If T.38 fax relay is successfully negotiated, Communication Manager issues a re-INVITE to G.711 mode.

• The fax call is in G.711 mode until the user disconnects. This feature works only over SIP trunks.

For more information about the T.38 Fax Fallback to G.711 feature, see Avaya Aura® Communication Manager Feature Description and Implementation.