Understanding Service Availability Features; Module Redundancy; Stateful Srp Switchover; Stateful Line Module Switchover - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - SERVICE AVAILABILITY CONFIGURATION GUIDE 2010-10-08 Configuration Manual

Understanding Service Availability Features

Module Redundancy

Stateful SRP Switchover

Stateful Line Module Switchover

Copyright © 2010, Juniper Networks, Inc.
Service availability refers to ability of a network or a network component to provide
uninterrupted delivery of services using highly available, redundant, and reliable
components. This topic provides brief overviews of the benefits of using the following
service availability features:
Module Redundancy on page 5
Stateful SRP Switchover on page 5
Stateful Line Module Switchover on page 5
Unified ISSU on page 6
VRRP on page 6
Interchassis Redundancy on page 6
For hardware components, Juniper Networks provides redundancy solutions to ensure
that the router continues to operate in the event of a hardware fault. Redundancy also
enables you to hot-swap various components within your E Series router.
Stateful SRP switchover (high availability) enables you to reduce or eliminate single
points of failure in your network. Stateful SRP switchover provides both hardware-specific
and software-specific methods to ensure minimal downtime and ultimately improve the
performance of your network.
Stateful SRP switchover minimizes the impact to the router of a stateful switchover from
the active SRP module to the standby SRP module. Stateful SRP switchover maintains
user sessions and data forwarding through the router during the switchover, thus improving
the overall availability of the router.
High availability of line modules increases the overall availability of the router by ensuring
that all the subscribers who were connected during a line module recovery continue to
remain logged in and can access network resources during the switchover from the
primary line module to the secondary line module. Forwarding of data through the fabric
slice for those subscribers continues with a brief disruption of two minutes. If you
configured stateful line module switchover on a router, when a switchover occurs, a
message is displayed on the active SRP module after the secondary line module
successfully takes over the role of the previously configured primary line module. If the
primary line module fails, the secondary line module takes the role of the primary line
module. Mirrored configuration data and any mirrored volatile data are already resident
in memory. The protocols and other applications re-initialize from the mirrored data and
resynchronize communications with the line modules (non-volatile configuration and
volatile state). Data forwarding operation continues to function normally with the
secondary line module operating on behalf of the primary line module (with a small loss
Chapter 1: Service Availability
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