3Com WX3000 operation manual Dldp Fundamentals, Dldp status, Status Description

Figure 1-2Fiber 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:

zAs 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.

zEven 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.

zWhen the port works in mandatory full duplex mode and the mandatory rate, DLDP can detect fiber disconnection in one direction as shown in Figure 1-2.

zWhen 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 Figure 1-2, in that case, it considers that the port is down.

DLDP Fundamentals

DLDP status

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

Table 1-1DLDP status

Status	Description
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
	All neighbors communicate normally in both direction, or DLDP
Advertisement	remains in active status for more than five seconds and enters this
	status. It is a stable status when no unidirectional link is found
	1-2