Link recovery design incorporates three separate timers that monitor the period of time that the server or gateway spends in specific link recovery processes. The table lists the timer parameters.
H.248 Link Recovery timers
Timer
Location
Description
Value range in minutes (default)
Link Loss Delay Timer
Server
The length of time that the server retains call information while the gateway attempts to reconnect to either its primary server or to alternate resources.
1-30(5)
Final Cleanup Timer
Server
Removes preserved connections that do not have disconnect supervision (not administrable).
120
Primary Search Timer
Gateway
The length of time that the gateway spends trying to connect to the primary server.
1-60(1)
Total Search Timer
Gateway
The length of time that the gateway spends trying to connect to all alternate resources.
1-60(30)
The sequence of events during Link Recovery is described in the table.
General Link Recovery process
Process sequence
Description
1.
Link failure detected
2.
The Primary and Total Search Timers begin running. The gateway attempts to re-establish the H.248 link with original server, which is the first element in the Media Gateway Controller (MGC) list.
If the gateway cannot reconnect with the original server, then it searches the MGC list (in order) for alternate resources (list elements 2-4) that are above the Transition Point (if set). These alternate resources can be:
Supported servers and Duplicated servers: For supported servers, see Avaya Aura® Communication Manager Hardware Description and Reference.
The Total Search Timer continues running.
See Administering the MGC list for instructions on administering this list and on setting the Transition Point.
4.
If the Primary Search Timer expires before the gateway can re-establish the link to the alternate resources that are above the Transition Point in the MGC list, then the gateway crosses the Transition Point and begins searching the other resources in the list. The gateway makes 2 connection attempts with any resources below the Transition Point: one on the encrypted link, the other on the unencrypted link.
5.
If the gateway cannot re-establish the link to any of the resources below the Transition Point, then it starts over at the top of the MGC list and continues to the end, making only 1 reconnection attempt to each element in the list. This continues until the Total Search Timer expires.
6.
If the gateway still cannot connect to any alternate resources and Total Search Timer expires, it reboots itself. For more information on the server and gateway alarm notification strategies, see Maintenance during recovery.
The server’s Link Loss Delay Timer should be the last timer to expire, meaning that the server holds its call control information until all other means of re-establishing have been exhausted.
Note:
If the Link Loss Delay Timer expires but the gateway successfully connects with an alternate resource, the system generates a warning alarm anyway, even though the H.248 link is up to another server.
