R3303-HP HSR6800 Routers High Availability Configuration Guide

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:
• CFD, DLDP, and Ethernet OAM are data link layer fault detection technologies.
• BFD is a generic fault detection technology that can be used at any layer.
• NQA is used for diagnosis and evaluation of network quality.
• Track works along with other high availability technologies to detect faults through a collaboration
mechanism.
Table 2 Fault detection technologies
Technolo
gy
Introduction Reference
CFD
CFD, which conforms to IEEE 802.1ag CFM and ITU-T Y.1731, is an
end-to-end per-VLAN link layer OAM mechanism used for link
connectivity detection, fault verification, and fault location.
"Configuring CFD"
DLDP
DLDP deals with unidirectional links that might occur in a network.
When detecting a unidirectional link, DLDP, as configured, can shut
down the related port automatically or prompt users to take actions to
avoid network problems.
"Configuring
DLDP"
Ethernet OAM
As a tool monitoring Layer 2 link status, Ethernet OAM is mainly used
to address common link-related issues on the last mile. You can
monitor the status of the point-to-point link between two directly
connected devices by enabling Ethernet OAM on the two devices.
"Configuring
Ethernet OAM"
BFD
BFD provides a single mechanism to quickly detect and monitor the
connectivity of links or IP forwarding in networks. To improve network
performance, devices must quickly detect communication failures to
restore communication through backup paths as soon as possible.
"Configuring BFD"
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.
Network
Management and
Monitoring
Configuration
Guide