FAX Scenario 3

The following ingress and egress policies are used for this FAX scenario.

Ingress Policy		Egress Policy
allow-codecs	*	allow-codecs	*
add-codecs-on-egress		add-codecs-on-egress	PCMU, G729 ,T.38
order-codecs		order-codecs
force-ptime	disabled	force-ptime	disabled
packetization-time		packetization-time

1. In the following diagram, PCMU and telephone-event codecs are received by Oracle® Enterprise Session Border Controller .The egress codec policy has PCMU, G729 and T.38 add-codecs-on-egress.
   Since there is a faxable codec in the SDP offer and T.38 in add-on-egress, the non-faxable codec G729 is stripped and T.38 is added to egress offer.

   In the A0 answer the audio m-line is zero indicating disabled and the port for the image m-line is non-zero (20000) so the called party has selected T.38. Hence PCMU in realm A is transcoded to T.38 in realm B.

   
2. In the following diagram, PCMU and T38 are received by the Oracle® Enterprise Session Border Controller. The egress codec policy has PCMU, G729, and T.38 add-codecs-on-egress.

   T.38 is present in the O0 offer, and therefore will not be explicitly added by the egress codec policy to the O2 Offer. The logic to remove non-faxable codecs is only invoked when T.38 is added by the add-codecs-on-egress parameter. In this example, T.38 is not added since is already present in SDP. With PCMU and T.38 received, G729 as a non-faxable codec is not removed. Therefore, PCMU, T.38, and G729 are all present in the O2 SDP offer sent to the answerer.

   In the A0 answer, the audio m-line port is 0 indicating that audio is disabled, and the port for the image m-line is nonzero (20000), thus the called party has selected T.38. In the A1 answer the OCSBC send the audio m-line port as 0 indicating that audio is disabled, and the port for the image m-line is nonzero (20000). This set-up results in a non-transcoded T.38 -OCSBC -T.38 fax call.