Graceful Routing Engine switchover (GRES) is supported in case
of a Routing Engine failure. A failure of the Routing Engine stops
the pgcpd process. When the JUNOS software high-availability framework
detects the Routing Engine failure, it switches control of the BGF
to the pgcpd process on the backup Routing Engine. The pgcpd process
stores completed H.248 states, and these states survive a restart
or a switchover. After the restart or switchover is completed, the
pgcpd process reapplies the states.
Gate Synchronization Procedure
When the IPC connection between the pgcpd process and the services
PIC or MS-DPC is being reestablished, a synchronization process restores
the previous state of gates, so session and call continuity is achieved.
That is, existing calls stay active and voice sessions are not disconnected.
The synchronization process can result in the mismatching of
gates. Mismatched gates are handled as follows:
If the pgcpd process detects gates that exist in the Routing
Engine, but are missing in the PIC or DPC, the pgcpd process reinstalls
the gates on the PIC or DPC. Existing calls receive service from the
PIC or DPC when the synchronization is complete.
If the pgcpd process detects gates that exist on the PIC
or DPC, but not on the Routing Engine, the pgcpd process removes the
gates from the PIC or DPC. This removal causes the associated sessions
to be closed, and the session resources to be released.
If the pgcpd process detects gates that exist on the PIC
or DPC and on the Routing Engine, but the versions of the gates do
not match, the pgcpd process forces the Routing Engine version. Doing
so maintains call continuity by making sure that the databases are
synchronized, while limiting the effect to existing calls and sessions.
You can control the number of mismatches by configuring the
synchronization properties.
Configuring Synchronization Properties
You can configure the maximum number of mismatches allowed during
the synchronization process between the PIC or DPC and the pgcpd process.
Step-by-Step Procedure
To configure properties for synchronization between the PIC
or DPC and the pgcpd process:
Access the graceful restart configuration.
[edit services pgcp]
edit gateway bgf-1 graceful-restart
Configure the maximum number of mismatches
allowed during the synchronization procedure. If the number of mismatches
exceeds this number, the pgcpd process clears the state of the PIC
or DPC and the state of the pgcpd process. All calls and sessions
are terminated and existing resources are released.
Configure the number of milliseconds
within which you want the synchronization process to complete. If
the process is not complete when this time expires, the pgcpd process
clears the state of the PIC or DPC and the state of the pgcpd process.
Displaying the Status of the Routing Engine Synchronization
Purpose
To determine the status of the synchronization between the main
Routing Engine and the backup Routing Engine, display the value of
the replication socket field.
Action
user@host> show services pgcp active-configuration
