Slow Start to Fast Start Translation

When you configure your Oracle® Enterprise Session Border Controller to support H.323 Slow Start to Fast Start translations, you enable an H.323 endpoint that only supports Slow Start to initiate and sustain communication with an H.323 Fast Start endpoint. The Oracle® Enterprise Session Border Controller resolves the Slow Start limitation of exchanging information about media (OLC messages) after the call is connected. The OLC message opens a logical channel, or a unidirectional or bi-directional path used to transmit media packets. Using the Oracle® Enterprise Session Border Controller, you can negotiate the construction of media flows differently, which is described in this section.

When you enable the Fast Start option for calls in the H.323 stack configuration, the Oracle® Enterprise Session Border Controller performs the translation of a Slow Start call into Fast Start. When it receives a Slow Start call, the Oracle® Enterprise Session Border Controller determines its destination and the H.323 stack it uses for the outgoing call.

It is a requirement of this kind of translation that you configure and use media profiles. Since a Slow Start call does not negotiate media until after the call is connected, there needs to be an assumption made about the media to set up a Slow Start to Fast Start call. Media profiles fill this role, and they are assumed to be part of a correct configuration.

The following describes possible scenarios for Slow Start to Fast Start translations.

• When a Slow Start call arrives at the Oracle® Enterprise Session Border Controller and matches one of the session agents that has a media profiles list configured, the outgoing call is set up as a Fast Start call. The session agent’s media profiles are used for the logical channels. You must configure the media profiles to reference a codec the endpoint accepts.

  If there are no media profiles configured for the session agent, then the Oracle® Enterprise Session Border Controller uses the media profiles list in the H.323 stack configuration to open the logical channels.

• If a Slow Start calls arrives at the Oracle® Enterprise Session Border Controller and its destination does not match one of the session agents, the Oracle® Enterprise Session Border Controller uses the media profiles list in the H.323 stack configuration for the outgoing call. If there is a list of media profiles, the outgoing call is set up as a Fast Start call with the media profiles list used to open the logical channels.

  If there is no list of media profiles for the outgoing H.323 interface, the Oracle® Enterprise Session Border Controller does not perform Slow Start to Fast Start translation. The Slow Start call exits the Oracle® Enterprise Session Border Controller as it arrived—as a Slow Start call.

• If the egress H.323 interface has the Fast Start option disabled, then the outgoing call uses the Slow Start mode, and the Oracle® Enterprise Session Border Controller does not perform Slow Start to Fast Start translation. In this case, the Slow Start call also exits the Oracle® Enterprise Session Border Controller as it arrived—as a Slow Start call.