Configuring Dldp; Overview - HPE FlexFabric 5700 Series Configuration Manual

Configuring DLDP

Overview

Unidirectional links occur when one end of a link can receive packets from the other end, but the
other end cannot receive packets sent by the first end.
Unidirectional fiber links occur in the following cases:
•
Fibers are cross-connected.
•
A fiber is not connected at one end or one fiber of a fiber pair is broken.
Figure 6 shows a correct fiber connection and the two types of unidirectional fiber connections.
Figure 6 Correct and incorrect fiber connections
Physical layer detection mechanisms, such as auto-negotiation, can detect physical signals and
faults. They cannot detect communication failures for unidirectional links where the physical layer
state is connected.
As a data link layer protocol, the Device Link Detection Protocol (DLDP) detects whether the fiber
link or twisted-pair link is correctly connected at the link layer, and whether the two ends can
exchange packets correctly. When DLDP detects unidirectional links, it can automatically shut down
the faulty port to avoid network problems. Alternatively, a user can manually shut down the faulty port.
DLDP cooperates with physical layer protocols to monitor link status and avoid physical and logical
unidirectional links.
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