High Availability Overview; Availability Requirements; Availability Evaluation - H3C S9500E Series Configuration Manual

High availability overview

Communication interruptions can seriously affect widely-deployed value-added services such as
IPTV and video conference. Therefore, the basic network infrastructures must be able to provide
high availability.
There are three effective ways to improve availability:
•
Increasing fault tolerance
•
Speeding up fault recovery
•
Reducing impact of faults on services

Availability requirements

Availability requirements fall into three levels based on purpose and implementation, as shown in
Table 1.
Table 1 Availability requirements
Level Requirement
Decrease system software and
1
hardware faults
Protect system functions from being
2
affected by failures
Enable the system to recover as fast
3
as possible
The level 1 availability requirement should be considered during the design and production
process of network devices. The level 2 availability requirement should be considered during
network design. The level 3 availability requirement should be considered during network
deployment, according to the network infrastructure and service characteristics.

Availability evaluation

Typically, MTBF and MTTR are used to evaluate the availability of a network.
MTBF
MTBF is the predicted elapsed time between inherent failures of a system during operation. It is
typically expressed in hours. A higher MTBF means a higher availability.
Solution
Hardware: Simplified circuit design, enhanced
•
production techniques, and reliability tests.
Software: Reliability design and tests
•
Device and link redundancy and switchover
Fault detection, diagnosis, isolation, and recovery
technologies
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