Create Emergency Session Call Flow

This section describes the create emergency session (IMEI, Unauthenticated IMSI) call flow.

Create Emergency Session Call Flow

For an Emergency call, cnSGW-C receives an Initial Attach Request in CSR with an UnAuthenticated IMSI, or with an IMEI only. cnSGW-C allocates TEID and SEID from the Node Manager and sends the Sx Establishment Request with local SEID to the UP to establish the session.

Once cnSGW-C receives the Sx Establishment Response from the UP with the UP SEID and the local GTPU TEID for S5 and S1 GTPU FTEID, cnSGW-C sends the Create Session Request to the PGW using EGTP EP. After receiving response from the PGW for Create Session Response, cnSGW-C sends the Sx Modification Request to connect S5-GTPU tunnel between PGW-U and SGW-U. On successful reception of Sx Modification Response, cnSGW-C sends the Create Session Response to the MME and the session is created in CDL.

With Initial attach procedure, cnSGW-C supports handling of Modify Bearer Request which connects S1 GTPU tunnel between eNodeB and SGW-U. When cnSGW-C receives MBR, it sends Sx Modification Request to connect S1 GTPU tunnel between eNodeB and SGW-U. After receiving Sx Modification Response, cnSGW-C sends Modify Bearer Response to the MME. Session is updated in CDL as the end of transaction.