Developing SIP applications that support PRACK on Liberty

A SIP response to an INVITE request can be final or provisional. Final responses are always sent reliably, but provisional responses typically are not. For cases where you need to send a provisional response reliably, you can use the PRACK (Provisional response acknowledgment) method.

Before you begin

To develop applications that support PRACK, the following criteria must be met:
  • To indicate that the client supports PRACK, the client that sends the INVITE request must put a 100rel tag in the Supported or the Require header.
  • The SIP servlet must respond by invoking the sendReliably() method instead of the send() method.

About this task

PRACK is described in the following standards:
  • RFC 3262 ("Reliability of Provisional Responses in the Session Initiation Protocol (SIP)"), which extends RFC 3261 ("SIP: Session Initiation Protocol"), adding PRACK and the option tag 100rel.
  • Section 5.7.1 ("Reliable Provisional Responses") of JSR 289 ("SIP Servlet Specification Version 1.1").

Procedure


Icon that indicates the type of topic Task topic

File name: twlp_sip_devprak.html