3com WX3000 User Manual

 

1-2 

Figure 1-2 Fiber correct connection/disconnection in one direction 

GE1/0/10      SwitchA       GE1/0/11

GE1/0/10      SwitchB       GE1/0/11

PC

 

 

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. While the auto-negotiation mechanism on the physical layer detects physical signals 

and faults; DLDP identifies peer devices and unidirectional links, and disables unreachable ports. 

z 

Even if the links of both ends can normally operate individually on the physical layer, DLDP can 

detect (at the link layer) whether these links are connected correctly and packets can be 

exchanged normally between the two ends. This detection cannot be implemented by the 

auto-negotiation mechanism. 

 

z 

When the port works in mandatory full duplex mode and the mandatory rate, DLDP can detect fiber 

disconnection in one direction as shown in 

. 

z 

When the port works in auto-negotiation duplex mode and auto-negotiation rate, even if DLDP is 

enabled, it does not take effect when fiber in one direction is disconnected as shown in 

in that case, it considers that the port is down. 

 

A link can be in one of these DLDP states: initial, inactive, active, advertisement, probe, disable, and 

delaydown. 

Table 1-1 DLDP status 

Initial 

DLDP is not enabled.  

Inactive 

DLDP is enabled but the corresponding link is down 

Active 

DLDP is enabled and the link is up, or an neighbor entry is cleared 

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All neighbors communicate normally in both direction, or DLDP 
remains in active status for more than five seconds and enters this 
status. It is a stable status when no unidirectional link is found