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Manual Migration and Rollback of UEs in the MSC Pool Networking If the MSC is faulty or needs to be upgraded, you can migrate UEs from the faulty MSC to another MSC. The migration is divided into the following phases: - Phase 1: UE-triggered migration. When the UE initiates a combined attach, periodic routing area update (RAU) procedure or tracking area update (TAU) procedure, the MME selects another MSC for the UE.
- Phase 2: MME-triggered migration. The MME sends an IMSI detach request to the UEs that have not been migrated in phase 1, for example, UEs in connected state. During the TAU procedure, the MME selects another MSC for the UEs and implement the UE migration.
After having initiated the UE migration, whenever needed, you can issue a command to terminate the migration. Upon receiving the termination command, the OMS starts the migration rollback. When a UE initiates combined attach, periodic RAU procedure or TAU procedure, the MME forcibly updates the SGs interface and allocates the UE back to the original MSC. Most UEs can be migrated back to the original MSC after one RAU period. http://localhost:7904/pages/31185560/15/31185560/15/resources/public_sys-resources/icon-note.gif NOTE: If you issue the migration termination command during phase 1 migration, the OMS will not perform phase 2 migration. Therefore, before issuing the migration termination command, you are advised to run DSP VLR in the MML command window on the OMS to check whether the UE has been migrated. Figure 3 shows the procedures for manual migration and rollback of UEs in the MSC pool networking. Figure 3 Procedure for manual migration and rollback of UEs in the MSC pool networking
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