Introduction To Bfd; Bfd Overview; Bfd Features Supported By The Ar2200-S - Huawei AR2200-S Series Configuration Manual

Huawei AR2200-S Series Enterprise Routers
Configuration Guide - Reliability

3.1 Introduction to BFD

BFD rapidly detects communication faults between a local device and its neighbors. This
minimizes the impact of the faults on services.

3.1.1 BFD Overview

BFD is a uniform detection mechanism for an entire network. It detects faults quickly and
monitors the forwarding and connectivity of links or IP routes of the network.
On a network, a link fault is detected in either of the following methods:
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The following problems exist in the preceding methods:
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BFD is developed to resolve these problems.
BFD provides the following functions:
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3.1.2 BFD Features Supported by the AR2200-S

This topic describes BFD features supported by the AR2200-S.
BFD provides fast failure detection for multiple protocols.
On the AR2200-S, you can configure the BFD session establishment mode, single-hop BFD and
multi-hop BFD, BFD for VRRP, BFD for static routes, and BFD for routing protocols, associate
the BFD session status with the interface status, modify BFD parameters, and bind a BFD session
to a VPN instance.
BFD Session Establishment
BFD uses local and remote discriminators to differentiate BFD sessions. The AR2200-S supports
the following BFD session types:
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Issue 01 (2012-01-06)
Hardware detection signals, such as those provided by the Synchronous Digital Hierarchy
(SDH) alarm function, are used to detect a link fault rapidly.
If the hardware detection method is unavailable, the Hello mechanism of a routing protocol
is used to detect faults.
Hardware is used by only part of mediums to detect faults.
The routing protocol-specific Hello mechanism takes more than 1 second to detect a fault.
If data is forwarded at gigabit rates, a large amount of data is dropped.
On a small-scale Layer 3 network, if no routing protocol is deployed, the routing protocol-
specific Hello mechanism does not detect faults. This means that a fault between
interconnected systems is difficult to locate.
Detects faults rapidly along paths between neighboring forwarding engines, with light loads
and high speeds.
Uses a single mechanism to monitor any kind of medium and protocol layer in real time.
Detection time and costs vary.
Static BFD sessions with manually specified discriminators
Static BFD sessions with automatically negotiated discriminators
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