Nortel Networks 1000E User Manual

Page 462 of 488

 Configuring MG 1000T survivability and alternate primary controller

553-3041-210 Standard 4.00 September 2007

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If survivability is configured on an MG 1000T, the following scenarios can 
trigger a switchover to Survival Mode:

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Automatic Switchover — triggered when the MG 1000T Expansion 
loses communication with the primary controller and the Switchover 
Time Out (SWOTO) timer expires. This can occur if there is a 
catastrophic failure of the primary controller, or the IP link is lost 
between the MG 1000T Core and the MG 1000T Expansion.

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Manual Switchover — triggered with the Switchover to Survival (SOTS) 
command in LD 135.

When an MG 1000T, with survivability configured, loses communication 
with the primary controller, the MG 1000T automatically switches over to 
Survival Mode when the SWOTO timer expires. 

If the IP link is detected as down again before the expiration of the SWOTO 
timer, the timer stops, and the MG 1000T remains in Survival operating 
mode.

The state of communication between the primary controller and the 
MG 1000T Expansion is monitored by a simple polling mechanism called a 
Heartbeat. 

This example illustrates the tasks performed by an MG 1000T Expansion 
when communication with the MG 1000T Core is lost.

The MG 1000T Expansion attempts to re-establish the connection to the 
MG 1000T Core. After four re-connection attempts with a pre-defined 
delay between each attempt, the SWOTO starts.