This section provides an overview of the Avaya SIP signaling header manipulation (SigMa) feature for the Avaya SBC product. This feature provides the ability to add, change, and delete any of the headers and other information in a SIP message. You can also configure such manipulation at each flow level in a highly flexible manner using a proprietary scripting language.

• SigMa Scripting Language: The proprietary scripting language, known as Sigma, developed by Avaya to define any SIP message manipulation that will be performed by Avaya SBC.

• Packet Path and Hook Points: The packet path where a message transverses through the Avaya SBC stack and the hook points within the path where actions defined in a SigMa script can be acted upon.

• Avaya SBC GUI SigMa Editor: Access to the SigMa Editor for creating SIP signaling manipulation scripts that is provided through the standard Avaya SBC Configuration/Management Graphical User Interface.

If you configure a Sigma profile in server configuration without configuring a server flow Sigma profile, the server configuration Sigma profile is always used.

If you configure a Sigma profile in server configuration and server flow, the system applies the server flow Sigma profile at the PRE-ROUTING and POST_ROUTING stages. The system applies server configuration Sigma profile at the AFTER_NETWORK stage.

You must not configure a Sigma profile in server configuration and then add new Sigma profiles created for that server configuration in server flows. In this scenario, The system does not apply server configuration Sigma profile because the server flow Sigma profile takes priority.