7.6.4 SGSN Failure

23.1193GPPGateway Location Register (GLR)Release 17Stage 2TS

After an SGSN restart, the SGSN deletes all MM and PDP contexts affected by the restart. When GGSN detects the SGSN restarted by polling function (echo request and response), it shall delete all PDP contexts associated to the SGSN. After that during restoration procedure the SGSN initiates location update procedure. However the GLR does not need to know that the SGSN restart and it only proceeds usual location procedure.

The restoration procedure of SGSN Failure is illustrated in Figure 7.6/6. Each step is explained in the following list.

Figure 7.6/6: Restoration of the SGSN

Procedure:

1. After the SGSN restart, it may broadcast a Reset message within SGSN area. This causes the MS to reinitiate Attach and Activate PDP context procedures.

2. When the SGSN receives Attach Request message and identifies no MM context for the MS, it initiates update location procedure.

3. The GLR initiates insert subscriber data procedure as normal update location procedure.

4. When the SGSN receives the Update GPRS Location ack message from the GLR, it returns the Attach Request ack message to the MS.

5. The MS which receives the message re-initiates Activate PDP context procedures, if needed.