Codec Reordering
Certain carriers deploy voice services where their peering partners do not use the carriers’ preferred codecs. The Oracle® Enterprise Session Border Controller can now reorder the codecs so that the preferred one is selected first.
Take the example of a carrier that deploys a voice service using G.729 rather than G.711. If that carrier has a peering partner providing call origination for the VoIP customers with G.711 used as the preferred codec, there can be issues with codec selection.
The Oracle® Enterprise Session Border Controller resolves this issue by offering its codec reordering feature. Enabled for realms and session agents, this feature gives the Oracle® Enterprise Session Border Controller the ability to reorder the default codec in an SDP offer to the preferred codec before it forwards the offer to the target endpoint. When you enable this feature, you increase the probability that the target endpoint will choose the preferred codec for its SDP answer, thereby avoiding use of the undesired codec.
You enable codec reordering feature by setting the preferred-codec=X (where X is the preferred codec) option in the realm and session agent configurations. You set it in the realm from which the Oracle® Enterprise Session Border Controller receives SDP offers (in requests or responses), and for which the media format list needs to be reordered by the Oracle® Enterprise Session Border Controller prior to being forwarded. To configure additional codec ordering support for cases when a response or request with an SDP offer is from a session agent, you can set this option in the session agent configuration.
If you enable the option, the Oracle® Enterprise Session Border Controller examines each SDP media description before if forwards an SDP offer. And if necessary, it performs reordering of the media format list to designate that the preferred codec as the default.
The Oracle® Enterprise Session Border Controller determines preferred codecs in the following ways:
- If the response or request with an SDP offer is from a session agent, the Oracle® Enterprise Session Border Controller determines the preferred codec by referring to the session agent configuration. You set the preferred codec for a session agent by configuring it with the preferred-codec=X option.
- If the response or request with an SDP offer is not from a session agent or is from a session agent that does not have the preferred-codec=X option configured, the Oracle® Enterprise Session Border Controller determines the preferred codec by referring to the preferred-codec=X option in the realm.
- If the Oracle® Enterprise Session Border Controller cannot determine a preferred codec, it does not perform codec reordering.
Note:
that the Oracle® Enterprise Session Border Controller performs codec reordering on the media format list only. If the rtpmap attribute of the preferred codec is present, the Oracle® Enterprise Session Border Controller does not reorder it.
