Bfd Overview; Bfd Features Supported By The S3700 - Huawei Quidway S3700 Series Configuration Manual

Quidway S3700 Series Ethernet Switches
Configuration Guide - Reliability

6.1 BFD Overview

BFD, a uniform detection mechanism for an entire network, rapidly detects faults 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 the preceding problems.
BFD provides the following functions:
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6.2 BFD Features Supported by the S3700

This section describes the BFD features supported by the S3700.
The S3700s send BFD control packets based on the negotiated period. If an S3700 does not
receive the packet of the peer within the detection time, the S3700 sets the BFD session in Down
state. The upper-layer application can take actions according to the status of the BFD session.
BFD Session Establishment Supported by the S3700
BFD uses the local discriminator and remote discriminator to differentiate multiple BFD sessions
between the same pair of systems. According to the difference in the modes of creating the local
discriminator and the remote discriminator, the S3700 supports the following BFD session types:
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A dynamic BFD session triggered by a protocol is implemented as follows:
Issue 01 (2011-10-26)
NOTE
The S3700SI does not support BFD.
Hardware detection signals, such as in the Synchronous Digital Hierarchy (SDH) alarm
function, are used to detect a link fault rapidly.
If the preceding method is unavailable, the Hello mechanism of a routing protocol is used
to detect a fault.
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 a fault. This means that a fault between the
interconnected systems is hard to locate.
Detects faults rapidly in paths between neighboring forwarding engines, with light loads
and high speeds.
Uses a single mechanism to monitor any medium and protocol layer in real time. In addition,
the detection time and costs are variable.
Static BFD sessions with manually specified discriminators
Static BFD sessions with automatically negotiated discriminators
Dynamic BFD sessions triggered by a protocol
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