3.2.5.3.2 Relying Party Security Realm Discovery

As specified in section 3.1.1.5.1, a requestor IP/STS MAY store a session identifier for the web browser requestor in an HTTP session cookie (for more information, see [RFC2965]). It uses this identifier and its Outbound Sessions List to develop the list of relying parties to which it SHOULD<63> send wsignoutcleanup1.0 request messages.