3.1.2.6 Timer Events

When the SIP registrar's expiry timer for a binding expires, the registrar MUST remove the binding and clear any state related to the binding. If the routable field was previously set to "true", it SHOULD be changed to "false". If the keep-alive timer specified in [MS-CONMGMT] section 3.4.5.2 fires, the binding SHOULD be removed.