Introduction To Dldp - Huawei Quidway S3700 Series Configuration Manual

Quidway S3700 Series Ethernet Switches
Configuration Guide - Reliability

1.1 Introduction to DLDP

This section describes the concept of DLDP.
On a network, unidirectional link faults often occur. That is, the local device can receive packets
from the remote device through the link layer, but the remote device cannot receive packets from
the local device.
Take the fiber as an example. The fault of unidirectional link may be caused by crossed
connection of fibers or disconnection of one fiber.
Figure 1-1 Crossed connection of fibers
Ethernet0/0/1
Ethernet0/0/1
Figure 1-2 Disconnection of one fiber
Ethernet0/0/1
Ethernet0/0/1
DLDP can detect the link status of fibers or copper twisted pairs. If a unidirectional link exists,
DLDP automatically disables the interface or prompts the user to manually disable the interface.
This prevents network faults. Currently, the S3700 supports DLDP detection for up to 256
neighbors.
As a link layer protocol, DLDP works with the physical layer protocol to detect the link status.
The auto negotiation mechanism on the physical link detects physical signals and faults on the
Issue 01 (2011-10-26)
SwitchA
Ethernet0/0/2
Ethernet0/0/2
SwitchB
SwitchA
TX
RX
RX TX
SwitchB
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