Overview

With dialog transparency enabled, the Oracle® Enterprise Session Border Controller is prevented from generating a unique Call-ID and from modifying the dialog tags; the Oracle® Enterprise Session Border Controller passes what it receives. Therefore, when a call made on one Oracle® Enterprise Session Border Controller is transferred to another UA and crosses a second Oracle® Enterprise Session Border Controller, the second Oracle® Enterprise 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® Enterprise Session Border Controller or how many Oracle® Enterprise Session Border Controllers a call crosses.

Without dialog transparency enabled, the Oracle® Enterprise 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® Enterprise Session Border Controller can recognize the direction of a dialog. However, this behavior makes call transfers problematic because one Oracle® Enterprise Session Border Controllers’ Call-ID might not be properly decoded by another Oracle® Enterprise Session Border Controller. The result is asymmetric header manipulation and failed call transfers.