B.4 IMS Session Termination

29.2133GPPPolicy and charging control signalling flows and Quality of Service (QoS) parameter mappingRelease 17TS

B.4.1 Mobile initiated session release / Network initiated session release

Figure B.4.1.1 presents the mobile or network initiated IMS session release without access network information retrieval. The session release may be signalled by a SIP BYE message, or any SIP 3xx redirect response, or any 4xx, 5xx, or 6xx SIP final error response to an initial INVITE request. If any 4xx, 5xx, or 6xx SIP final error response to Re-INVITE or UPDATE request just terminates the transaction, then the session is not released, otherwise if the error response terminates the dialog then the session is released.

Figures B.4.1.2 and B.4.1.3 presents the network initiated and the mobile initiated IMS session release with access network information retrieval, respectively.

Figure B.4.1.1: IMS session termination without access network information retrieval

1. SIP BYE message, a SIP 3xx redirect response, or any 4xx, 5xx, or 6xx SIP final error response to an initial INVITE or any 4xx, 5xx, or 6xx SIP final error response to Re-INVITE or UPDATE which terminates the dialog is received by the P-CSCF.

2. P-CSCF forwards the BYE message, or the SIP 3xx redirect response, or any 4xx, 5xx, or 6xx SIP final error response.

3. The Interactions in in Figure 4.3.1.2.3.1.1 or Figure 4.3.1.2.3.2.1are applicable.

Figure B.4.1.2: network initiated IMS session termination with access network information retrieval

1. SIP BYE message is received by the P-CSCF.

2. The P-CSCF forwards the BYE message.

3. In parallel to step 2, the Interactions in Figure 4.3.1.2.3.1.1 or Figure 4.3.1.2.3.2.1 take place. Within those interactions, the P-CSCF requests and receives the access network information.

4. The P-CSCF receives the SIP 200 OK (BYE) SIP message.

5. The P-CSCF forwards the SIP 200 OK (BYE) SIP message. It includes the access networking information obtained in step 3 as the network provided location information.

Figure B.4.1.3: mobile initiated IMS session termination with access network information retrieval

1. SIP BYE message is received by the P-CSCF.

2. The Interactions in Figure 4.3.1.2.3.1.1 or Figure 4.3.1.2.3.2.1 are applicable. Within those interactions, the P-CSCF requests and receives the access network information.

3. The P-CSCF forwards the BYE message. It includes the access network information obtained in step 2 as the network provided location information.

B.4.2 IP-CAN Bearer Release/Loss

An IP-CAN Bearer Release or Loss event may affect all IP-Flows within an IMS Session. Flows in clause 4.3.2.2.1 (AF located in the HPLMN) or 4.3.2.2.2 (AF located in the VPLMN) apply for case 1. Flows in clause 4.4.2.1.1 (Home Routed case) or 4.4.2.2.1 (Visited Access case) apply for case 2a and case 2b.