Nortel Networks 1000M - Manual (Page 299)

Description 299
Switchover to survival mode
A survivable IP Expansion Cabinet or Chassis is able to restart after it loses
communication with the Main Cabinet or Chassis, due to an outage of the
Main Cabinet or Chassis or due to a failure of the link between the cabinets
or chassis. During the restart procedure, the survivable IP Expansion
Cabinet or Chassis attempts to register with the Main Cabinet or Chassis.
If a connection cannot be made with the Main Cabinet or Chassis within
approximately two minutes, the IP Expansion Cabinet or Chassis switches
to survival mode and acts as a stand-alone Small System.
Triggers
If Survivability is configured on a cabinet or chassis, the following two
scenarios can trigger a switchover to survival mode:
• Automatic Switchover is triggered when the IP Expansion Cabinet or
Chassis loses communication with the Main Cabinet or Chassis and the
Switchover Time Out timer (SWOTO) expires. This can occur if there is
a catastrophic failure of the Main Cabinet or Chassis, or the link is lost
between the Main Cabinet or Chassis and the IP Expansion Cabinet
or Chassis.
• Manual Switchover is triggered with the Switchover to Survival (SOTS)
command in LD 135.
Automatic switchover to survival mode
When an IP Expansion Cabinet or Chassis, with Survivability configured,
loses communication with the Main Cabinet or Chassis, the IP Expansion
Cabinet or Chassis automatically switches over to survival mode when the
SWOTO timer expires.
The state of communication between the Main Cabinet or Chassis and
the IP Expansion Cabinet or Chassis is monitored by a simple polling
mechanism called a Heartbeat.
The following example illustrates the tasks performed by the Small System’s
IP Expansion Cabinet or Chassis when communication with the Main
Cabinet or Chassis is lost:
1. The IP Expansion Cabinet or Chassis attempts to reestablish the
connection to the Main Cabinet or Chassis. After four reconnection
attempts with a predefined delay between each attempt, the SWOTO
starts.
2. The SWOTO expires after the time defined in LD 117.
3. The IP Expansion Cabinet or Chassis restarts. As the IP Expansion
Cabinet or Chassis is going through the restart procedure, it attempts
to register with the Main Cabinet or Chassis.
4. If a connection cannot be made to the Main Cabinet or Chassis, the IP
Expansion Cabinet or Chassis comes up in survival mode.
Nortel Communication Server 1000
Communication Server 1000M and Meridian 1 Small System Installation and Commissioning
NN43011-310 01.04 Standard
Release 5.0 13 May 2008
Copyright © 2008, Nortel Networks
.