SIP PRACK Interworking

When you configure your Oracle® Enterprise Session Border Controller with PRACK interworking for SIP, you enable it to interwork between endpoints that support RFC 3262, Reliability of Provisional Responses in the Session Initiation Protocol, and those that do not.

As its title indicates, RFC 3262 defines a reliable provisional response extension for SIP INVITEs, which is the 100rel extension tag. While some endpoints do not support the RFC, other SIP implementations require compliance with it. A session setup between two such endpoints fails. However, you can configure your Oracle® Enterprise Session Border Controller to supply the provisional response on behalf of endpoints that do not support it—and thereby enable sessions between those endpoints and the ones requiring RFC 3262 compliance.

You need to configure PRACK interworking for a SIP interface associated with the endpoints that need RFC 3262 support. To enabled the feature, you set the 100rel-interworking option. The Oracle® Enterprise Session Border Controller applies PRACK interworking for either the UAC or the UAS. TheOracle® Enterprise Session Border Controller checks to see whether or not it needs to apply PRACK interworking when an INVITE arrives at the ingress or egress SIP interface with the option enabled. First, it checks the Require header for the 100rel tag; if not found there, it checks the Supported header.

Since there is a slight difference in the application of this feature between the UAC and UAS, this section explains both.

Note:

If SDP is included in a PRACK request sent to a SIP interface where PRACK interworking is enabled, it will not be responded to, nor will any SDP be included in the locally-generated 200 OK to that PRACK.