H3C Technologies H3C S3100 Series Switches - Manual (Page 191)

1-2
Figure 1-1 Fiber cross-connection
Figure 1-2 Fiber broken or not connected
Switch A
GE1/1/1 GE1/1/2
Switch B
GE1/1/1 GE1/1/2
PC
Device link detection protocol (DLDP) can detect the link status of an optical fiber cable or copper
twisted pair (such as super category 5 twisted pair). If DLDP finds a unidirectional link, it disables the
related port automatically or prompts you to disable it manually according to the configurations, to avoid
network problems.
A copper twisted-pair cable (such as a Category 5e twisted-pair cable) contains eight wires. Some of
these wires only transmit data, while the others only receive data. When the wires that only receive data
or those that only transmit data all fail while the others are normal, a unidirectional link occurs.
DLDP provides the following features:
z As a link layer protocol, it works together with the physical layer protocols to monitor the link status
of a device.