184 CHAPTER 22: DLDP CONFIGURATION
Figure 49 Unidirectional fiber link: cross-connected fiber
Figure 50 Unidirectional fiber link: fiber not connected or disconnected
DLDP Introduction Device Link Detection Protocol (DLDP) can detect the link status of a fiber cable or
twisted pair. On detecting a unidirectional link, DLDP can shut down the related
port automatically or prompt users to take measures as configured to avoid
network problems.
As a data link layer protocol, DLDP cooperates with physical layer protocols to
monitor the link status of a device. The auto-negotiation mechanism provided by
physical layer protocols detects physical signals and faults. DLDP, however,
performs operations such as identifying peer devices, detecting unidirectional
links, and shutting down unreachable ports. The cooperation of physical layer
protocols and DLDP ensures that physical/logical unidirectional links be detected
and shut down. For a link with the devices on the both sides of it operating
properly, DLDP checks to see if the cable is connected correctly and if packets can
be exchanged between the two devices. Note that DLDP is not implemented
through auto-negotiation.
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Device B
PC
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Device A
Device B
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