Dialog Transparency

This section explains how to configure dialog transparency, which prevents the Oracle Communications Session Border Controller from generating a unique Call-ID and modifying dialog tags.

Overview

With dialog transparency enabled, the Oracle Communications Session Border Controller is prevented from generating a unique Call-ID and from modifying the dialog tags; the Oracle Communications Session Border Controller passes what it receives. Therefore, when a call made on one Oracle Communications Session Border Controller is transferred to another UA and crosses a second Oracle Communications Session Border Controller, the second Oracle Communications Session Border Controller does not note the context of the original dialog, and the original call identifiers are preserved end to end. The signalling presented to each endpoint remains in the appropriate context regardless of how many times a call crosses through a Oracle Communications Session Border Controller or how many Oracle Communications Session Border Controllers a call crosses.

Without dialog transparency enabled, the Oracle Communications Session Border Controller’s SIP B2BUA rewrites the Call-ID header and inserted dialog cookies into the From and To tags of all messages it processes. These dialog cookies are in the following format: SDxxxxxNN-. Using these cookies, the Oracle Communications Session Border Controller can recognize the direction of a dialog. However, this behavior makes call transfers problematic because one Oracle Communications Session Border Controllers’ Call-ID might not be properly decoded by another Oracle Communications Session Border Controller. The result is asymmetric header manipulation and failed call transfers.

Dialog Transparency Configuration

You set one parameter in your SIP configuration to enable dialog transparency.

• For new configurations, this feature defaults to enabled

  To enable SIP dialog transparency:

1. In Superuser mode, type configure terminal and press Enter.

   ORACLE# configure terminal

2. Type session-router and press Enter to access the session-router path.

   ORACLE(configure)# session-router

3. Type sip-config and press Enter. The system prompt changes to let you know that you can begin configuring individual parameters.

   ORACLE(session-router)# sip-config

4. Use the ACLI select command so that you can work with the SIP configuration.

   ORACLE(sip-config)# select

5. dialog-transparency—Enter the state of SIP dialog transparency you require for your Oracle Communications Session Border Controller. The default value is enabled. The valid values are:

   • enabled | disabled