Section: 16.3a.3 AAA-Initiated Bearer termination
Content: RADIUS is used as the protocol between the P-GW and the AAA server or proxy for applications (e.g. MMS) to deliver information related to EPS user session. However some IP applications could need to interwork with the P-GW to release the corresponding resource (e.g. terminate a particular bearer or Resource Allocation Deactivation procedures as defined in TS 23.402[ Architecture enhancements for non-3GPP accesses ]  [78]). For this purpose, the AAA server or proxy may send a RADIUS Disconnect Request to the P-GW. On receipt of the Disconnect-Request from the AAA server, the P-GW shall release the corresponding resources and reply with a Disconnect-ACK. If the P-GW is unable to release the corresponding resources, it shall reply to the AAA server with a Disconnect-NAK. For more information on RADIUS Disconnect, see IETF RFC 3576 [41]. If the P-GW deletes the corresponding bearer, it need not wait for the response from the S-GW or non-3GPP IP access or ePDG before sending the RADIUS DisconnectResponse to the AAA server. The Teardown-Indicator in the RADIUS Disconnect Request message indicates to the P-GW that all IP-CAN bearers for this particular user and sharing the same user session shall be deleted. The IP-CAN bearers that belong to the same IP-CAN session are identified by the Acct-Session-Id. The Charging-Id contained in the Acct-Session-Id can be of any IP-CAN bearer of the user. The P-GW is able to find out all the related IP-CAN bearers sharing the same user session once it has found the exact IP-CAN bearer from the Acct-Session-Id. If a user has the same user IP address for different sets of IP-CAN bearers towards different networks, only the IP-CAN bearers linked to the one identified by the Acct-Session-Id shall be deleted. If the value of Teardown-Indicator is set to "0" or if TI is missing, and if the Acct-Session-Id identifies the default bearer, the P-GW shall tear-down all the IP-CAN bearers that share the same user session identified by the Acct-Session-Id. The following Figure 25a.3 is an example message flow to show the procedure of RADIUS AAA-Initiated Bearer termination, which applicable for GTP based S5/S8: NOTE: As shown on figure 25a.3, the P-GW need not wait for the Delete Bearer Response from the S-GW to send the RADIUS DisconnectResponse to the AAA server. Figure 25a.3: AAA-initiated bearer termination with RADIUS