3Com S7902E, Configuration Manual

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BFD Configuration
When configuring BFD, go to these sections for information you are interested in:
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Introduction to BFD
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Configuring BFD Basic Functions
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Enabling Trap
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Displaying and Maintaining BFD
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The term “router” or router icon in this document refers to a router in a generic sense or an Ethernet
switch running routing protocols.
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The S7900E Series Ethernet Switches are distributed devices supporting Intelligent Resilient
Framework (IRF). Two S7900E series can be connected together to form a distributed IRF device.
If an S7900E series is not in any IRF, it operates as a distributed device; if the S7900E series is in
an IRF, it operates as a distributed IRF device. For introduction of IRF, refer to IRF Configuration in
the System Volume .
Introduction to BFD
To reduce the impact on services caused by communication failures and enhance network availability, a
device needs to quickly detect communication failures so that measures can be taken in time to ensure
service continuity.
Currently, the main fault detection methods include the following:
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Hardware detection: Detects link failures by sending hardware detection signals, such as SDH
(synchronous digital hierarchy) transmission system alarms. Hardware detection can quickly
detect failures, but it is not supported by all media types.
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Hello mechanism: Devices can use the hello mechanism of a routing protocol for failure detection,
which has a failure detection rate in seconds. However, for high-speed data transmission, such as
Gigabit data transmission, a detection rate slower than one second will cause a large quantity of
data to be dropped; for delay-sensitive services, such as voice services, the rate is not acceptable
either. Moreover, this detection method largely relies on the routing protocol.
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Other detection methods: Different protocols sometimes provide dedicated detection mechanisms.
However, such a mechanism is hard to be deployed for inter-system communications.
Bidirectional forwarding detection (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. Normally, devices in a network may employ the following detection methods: