Binding the session

In an ISC session, IMS can assume either the primary half-session role (send the BIND) or the secondary half-session role (receive the BIND). However, when session restart and recovery are required, session polarity must be maintained.

Definition: Session polarity means that the same session role (primary versus secondary) is in effect at the point of failure and is reestablished by the session initiation request. Otherwise, the request is rejected. When the session is initiated using an IMS /OPNDST command and session restart and recovery are not required, IMS requests to be the primary half session.