Service Availability Versus High Availability; Figure 1: Junose Software Service Availability Layers - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - SERVICE AVAILABILITY CONFIGURATION GUIDE 2010-10-08 Configuration Manual

JunosE 11.3.x Service Availability Configuration Guide
99.999%

Service Availability Versus High Availability

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Figure 1: JunosE Software Service Availability Layers

Protects infrastructure against DoS attacks
Network Resiliency
Protects against port, link (fiber cuts), and network node failures
Software Availability
Protects against software crashes and minimizes downtime from software upgrades
Hardware Redundancy and Design
1:1 or N:1 component-level protection
The security layer protects the network from DoS attacks.
The network resiliency layer protects against port, link, and node failures. You can
configure IEEE 802.3 ad link aggregation for Ethernet, and Virtual Router Redundancy
Protocol (VRRP) to improve network resiliency.
The software availability layer protects against software failures by using hot-fixes or
installing a higher-numbered software release. You can perform a unified in-service
software upgrade (ISSU) instead of the conventional software upgrade to reduce outage.
You can eliminate or reduce single points of failure by configuring stateful SRP switchover
(high availability). Any network component with an uptime of 99.999 percent is
considered highly available with a downtime of less than 5 minutes in a year.
The hardware redundancy and design layer introduces redundancy in the network in the
form of multiple power supplies, cooling devices, line modules, and sometimes even a
router. For instance, you can install a backup line module in your router to protect against
line module failure. You can also configure a router as a backup router that accepts
subscriber login requests when the master router fails.
High availability is a measure of the uptime of a network or network component. A network
component that has a downtime of 5 minutes is accessible or available 99 percent of
the time. If a failure occurs, a backup component is available within 5 minutes. A highly
available network is a network that has components that either have high reliability or
have the ability to recover very quickly from a failure, or both.
Service availability refers to the ability to provide uninterrupted delivery of services. For
example, from the time when a component fails to the time when the backup component
is accessible, the delivery of services is interrupted. To provide uninterrupted delivery of
services, highly available components must maintain session details and other data
across failures. Service availability can thus be defined as the ability to provide
uninterrupted delivery of services using a highly available network.
Understanding Service Availability Features on page 5
Security
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