Redundancy - Alcatel-Lucent 7450 Basic System Configuration Manual

Redundancy

The redundancy features enable the duplication of data elements and software functionality
to maintain service continuation in case of outages or component failure.
Refer to the Integrated Services Adapter Guide for information about redundancy for the
Integrated Service Adapter (ISA).
Software Redundancy
Software outages are challenging even when baseline hardware redundancy is in place. There
should be a balance to provide high availability routing otherwise router problems typically
propagate not only throughout the service provider network, but also externally to other
connected networks possibly belonging to other service providers. This could affect
customers on a broad scale. Presently, there are several software availability features that
contribute to the percentage of time that a router is available to process and forward traffic.
To fully appreciate high availability you should realize that all routing protocols specify
minimum time intervals in which the peer device must receive an acknowledgment before it
disconnects the session.
Therefore, router software has to recover faster than the specified time interval to maintain
up time.
Configuration Redundancy
Features configured on the active device CPM are saved on the standby CPM as well. When
the active device CPM fails, these features are brought up on the standby device CPM that
takes over the mastership.
Even with modern modular and stable software, the failure of route processor hardware or
software can cause the router to reboot or cause other service impacting events. In the best
circumstances, failure leads to the initialization of a redundant route processor, which hosts
the standby software configuration, to become the active processor. The following options are
available.
Basic System Configuration Guide
• OSPF default session timeout is approximately 40 seconds. The timeout intervals are
configurable.
• BGP default session timeout is approximately 120 seconds. The timeout intervals are
configurable for the 7750 SR and 7950 XRS only.
System Management
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