What is DLDP? - Ruijie Community

In current private line services, most of them are implemented using the multi-service transmission platform (MSTP). MSTP is based on the Synchronous Digital Hierarchy (SDH) and its common applicationis that Ethernet ports of two devices interwork with each other through the MSTP of an operator. The Ethernet, however, does not have the link negotiation and detection mechanisms. If an internal link of the operator fails, Ethernet devices at both ends of the link cannot perceive the failure and the Ethernet ports are still in the Up state. If data is still transmitted along this link,it is discarded by intermediate devices of the operator. Then, how to detect whether data forwarding of a link is normal? The Device Link Detection Protocol(DLDP) is a solution.

DLDP actually is to transmit an ICMP ECHO packet to detect accessibility of a destination address. If DLDP receives an ICMP REPLY packet, the destination address is accessible. If it fails to receive an ICMP REPLY packet, the destination address is inaccessible and DLDP detection result is failed. In this case, DLDP sets the protocol state of the port to down to make routes and forwarding information to the port become ineffective, thereby implementing traffic switching.