Configuration Guide      RLDP Configuration 
RLDP Configuration   
RLDP Overview 
Understanding RLDP 
The Rapid Link Detection Protocol (RLDP) is one of Ruijie's proprietary link protocol designed 
to detect Ethernet link fault quickly. 
General  Ethernet  link  detection  mechanism  only  makes  use  of  the  status  of  the  physical 
connections and detects the connectivity of the link via the auto-negotiation of the  physical 
layer. This detection mechanism has restrictions and sometimes cannot provide reliable link 
detection information for the user. For example, if the optical fiber receiving line pair on the 
optical interface is misconnected, due to the existence of the optical converter, the related port 
of the device is "linkup" physically but actually the corresponding layer-2 link cannot work for 
communications.  Here  is  another  example.  There  is  an  intermediate  network  between  two 
Ethernet devices. Due to the existence of the network transmission relay devices, the same 
problem may occur if those relay devices are faulty. 
The RLDP enables easy detection of Ethernet device link fault, including the one-way link fault, 
two-way link fault and loop link fault. 
The RLDP implements the detection by exchanging the RLDP messages at the two ends of the 
link, as shown in Figure-1: 
Figure-1: 
 
The RLDP defines two protocol messages: Probe message and Echo message. The RLDP 
sends the Probe message of this port to the port with RLDP configured and in linkup status on 
regular basis, and waits for the Echo message from the neighbor port and waits for the Probe 
message sent by the neighbor ports. If a link is correct both physically and logically, a port shall 
be able to receive the Echo message of the neighbor port as well as the Probe message of the 
neighbor port. Otherwise, the link is considered abnormal.