3.1.4 Higher-Layer Triggered Events
The higher layer can initiate a request to disconnect an established call session. When the higher layer requests to disconnect an established call session, the LAC/LNS MUST initiate the session teardown, as specified in section 5.6 of [RFC2661]. After the session teardown is complete, if no more call sessions exist between LAC and LNS, the control connection between LAC and LNS SHOULD be disconnected by initiating the control connection teardown, as specified in section 5.7 of [RFC2661].