H3C Technologies H3C SecBlade LB Cards - Manual (Page 10)

2
MTTR = fault detection time + hardware replacement time + system initialization time + link recovery time
+ routing time + forwarding recovery time. A smaller value of each item means a smaller MTTR and a
higher availability.
High availability technologies
Increasing MTBF or decreasing MTTR can enhance the availability of a network. The high availability
technologies described in this section meet the level 2 and level 3 high availability requirements in the
aspect of decreasing MTTR.
High availability technologies can be classified as fault detection technologies or protection switchover
technologies.
Fault detection technologies
Fault detection technologies enable detection and diagnosis of network faults:
• NQA is used for diagnosis and evaluation of network quality.
• Track work along with other high availability technologies to detect faults through a collaboration
mechanism.
Table 2 Fault detection technologies
Technology Introduction Reference
NQA
NQA analyzes network performance, services and service quality
through sending test packets, and provides you with network
performance and service quality parameters such as jitter, TCP
connection delay, FTP connection delay and file transfer rate.
"Configuring
NQA"
Track
The Track module implements collaboration between different
modules. The collaboration involves three sets of modules:
application, Track, and detection. These modules collaborate with
one another through collaboration entries. The detection modules
trigger the application modules to perform certain operations through
the Track module. The detection modules probe such items as link
status and network performance, and inform the application modules
of the detection result through the Track module. Once notified of
network status changes, the application modules use the changes to
avoid communication interruption and network performance
degradation.
"Configuring
Track"
Protection switchover technologies
Protection switchover technologies aim at recovering network faults. They back up hardware, link, routing,
and service information for switchover in case of network faults to ensure continuity of network services.
A single availability technology cannot solve all problems. You should use a combination of availability
technologies, chosen on the basis of detailed analysis of network environments and user requirements,
to enhance network availability. For example, access-layer devices should be connected to
distribution-layer devices over redundant links, and core-layer devices should be fully meshed. Network
availability should be considered during the planning stage.