Levels Of Reliability Requirements; Reliability Specifications - Huawei AR530 Series Configuration Manual

Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Reliability

1.1 Levels of Reliability Requirements

There are three requirement levels according to the objective and implementation.
lists three levels of reliability requirements.
Table 1-1 Levels of reliability requirements
Level
1
2
3
The reliability requirements at level 1 need to be considered during network device design and
production; the reliability requirements at level 2 need to be considered during network
architecture design; the reliability requirements at level 3 are met using reliability technologies
according to the network architecture and service characteristics during network deployment.

1.2 Reliability Specifications

The Mean Time Between Failures (MTBF) and Mean Time to Repair (MTTR) are used to
evaluate system reliability.
MTBF
The MTBF refers to the average time (usually expressed in hours) when a component or a device
works without any failure. A larger value of the MTBF indicates higher reliability.
MTTR
The MTTR refers to the average time that a component or a device will take to recover from
any failure. MTTR also involves device management and customer service, and is an important
specification for device maintenance.
MTTR = Fault detection time + Hardware replacement time + System initialization time + Link
recovery time + Route convergence time + Forwarding recovery time
Issue 01 (2014-11-30)
Objective
Fewer faults in the system
software and hardware
No impact on the system
when a fault occurs
Rapid recovery from a fault
that affects the system
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1 Introduction to Reliability
Table 1-1
Implementation
l Hardware: simplified
circuit design, improved
production technique, and
reliability test
l Software: software
reliability design and test
Device and link redundancy
design, switchover policy,
and switchover success rate
Fault detection, diagnosis,
isolation, and recovery
2