1. Developer Guide
  2. Composing SIP Applications
  3. Join and Replaces Header Support

Join and Replaces Header Support

Converged Application Server provides support for the use of both the Join and Replaces headers. To learn how to create SIP applications that use the functionality provided by the Join and Replaces headers, refer to the JSR 359 documentation and APIs.

About the Join Header

The Join header, defined in RFC 3911, is for use with SIP Call Control and Multi-Party applications. The Join header logically joins an existing SIP dialog with a new SIP dialog. You can use this to enable features such as Call Forwarding, Message Screening, and Call Center Monitoring.

The Join header contains information an application can use to match an existing SIP dialog to a new dialog. You can use the Join header to add a new dialog or SIP application session to an existing SIP application session in the same way that an encoded URI is used. This is achieved by setting the call-id, to-tag, and from-tag in the Join header of the SIP INVITE to match that of the existing dialog.

About the Replaces Header

The Replaces header, defined in RFC 3891, logically replaces an existing SIP dialog with a new SIP dialog. You can use this functionality to enable features such as Attended Call Transfer and Call Pickup.

The Replaces header contains information used to match and replace an existing SIP dialog (using the call-id, to-tag, and from-tag) to the newly created dialog. The Join header can be used to replace an existing SIP session associated with a SIP application session with a new dialog/session. This is achieved by setting the call-id, to-tag, and from-tag in the Replaces header of the INVITE to match that of an existing dialog.

Note:

The SIP application must determine to send a BYE message using the original dialog. Converged Application Server does not automatically send a BYE message to terminate the original dialog.

Enabling Support for Join and Replaces Headers

Support for the Join and Replaces headers is disabled by default. If you have applications that need to use the Join and Replaces headers, you must enable Converged Application Server to handle these types of headers.

Note:

Enabling support for the Join and Replaces header may affect the performance of Converged Application Server. When enabling this feature ensure that your deployment of Converged Application Server has enough memory, computing power, and network bandwidth to function properly using Join- and Replaces-enabled applications.

To enable support for Join and Replaces headers, edit the entry for the –Dwlss.dialog.index.enabled=false command in the startWebLogic.sh script, and set its value to true. The startWebLogic.sh script is located in the DOMAIN_HOME/bin directory, where DOMAIN_HOME is the domain's home directory. When support for Join and Replace headers is enabled, the entry in the startWebLogic.sh script appears as shown below: 

–Dwlss.dialog.index.enabled=true

See the Converged Application Server Administrator's Guide learn more about the startWebLogic.sh script and the start-up options it controls.