High Availability
Page 156 7210 SAS M, X Basic System Configuration Guide
High Availability
This section discusses the high availability (HA) routing options and features available to service
providers that help diminish vulnerability at the network or service provider edge and alleviate the
effect of a lengthy outage on IP networks.
High availability is an important feature in service provider routing systems. High availability is
gaining momentum due to the unprecedented growth of IP services and applications in service
provider networks driven by the demand from the enterprise and residential communities.
Downtime can be very costly, and, in addition to lost revenue, customer information and business-
critical communications can be lost. High availability is the combination of continuous uptime
over long periods (Mean Time Between Failures (MTBF)) and the speed at which failover or
recovery occurs (Mean Time To Repair (MTTR).
The popularity of high availability routing is evident at the network or service provider edge where
thousands of connections are hosted and rerouting options around a failed piece of equipment can
often be limiting. Or, a single access link exists to a customer because of additional costs for
redundant links. As service providers converge business-critical services such as real-time voice
(VoIP), video, and VPN applications over their IP networks, high availability becomes much more
stringent compared to the requirements for best-effort data. Network and service availability
become critical aspects when offering advanced IP services which dictates that IP routers that are
used to construct the foundations of these networks be resilient to component and software
outages.
HA Features
As more and more critical commercial applications move onto the IP networks, providing high
availability services becomes increasingly important. This section describes high availability
features for devices.
• Redundancy on page 156
→ Component Redundancy on page 157
Redundancy
The redundancy features enable the duplication of data elements to maintain service continuation
in case of outages or component failure.
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