Updating the b=AS line for Transcoded Calls

The Oracle Communications Session Border Controller can evaluate transcoding call scenarios and mitigate between end stations and policy servers to request appropriate bandwidth. The user can configure a specific value to be included in the SDP's b=AS line to ensure that it requests the correct bandwidth for transcoded calls. Depending on the transcoding scenario, this value may or may not be used.

The Oracle Communications Session Border Controller can change a call's egress answer b=AS line to a value based on the media profile configuration of the codec to which the media is being transcoded. This ensures that the Oracle Communications Session Border Controller makes bandwidth requests that are applicable to the leg on which that codec is used.

Use the syntax below to specify 124 kbps for a media profile's b=AS line.

(media-profile)#as-bandwidth 124

The parameter's default value is zero, meaning it is disabled. The range is from 0 to 4294967295, measured in kbps.

The Oracle Communications Session Border Controller can modify a b=AS: line at both the SDP media level and SDP session level. Session level b=AS modification does not use an as-bandwidth setting.

The Oracle Communications Session Border Controller updates a media level b=AS: line to the configured as-bandwidth value only for the Egress SDP Answer, not the offer.

The Oracle Communications Session Border Controller modifies a session level b=AS: value only if every m-line in the SDP also has a b=AS: value. If an incoming message has SDP with a session level b=AS value, and every m-line in the SDP has a b=AS value, then the Oracle Communications Session Border Controller updates the outgoing message's session level b=AS value to the sum of the transcoding/IPv4-IPv6 adjusted media level b=AS values in the outgoing message. If an incoming message has SDP with a session level b=AS value, but not every m-line in the SDP has a b=AS value, the Oracle Communications Session Border Controller does not modify the session level b=AS value in the outgoing message.

When the Oracle Communications Session Border Controller updates a b=AS: line in the egress answer's SDP to a configured as-bandwidth value, and the original ingress offer SDP already had a b=AS: line, the Oracle Communications Session Border Controller changes the egress answer SDP's b=AS: back to the ingress offer's b=AS: value, not to the configured as-bandwidth value.

Important operational considerations include:

The value can be understood as IP neutral, meaning the system recognizes when the call is IPv4 to IPv6 interworking, and adjusts the value of the b=AS line to compensate for the IP version of the applicable leg. The Oracle Communications Session Border Controller does this for both transcoded and non-transcoded calls in both the egress offer and answer.
The configuration has no effect if the initial message received has no b=AS line.
The configuration has no effect if the m line is not transcoded.
The system does not change a session b=AS value if the SDP has a media line with b=AS value of 0.