Dldp Fundamentals - Huawei Quidway S3900 Series Operation Manual

Operation Manual - DLDP
Quidway S3900 Series Ethernet Switches-Release 1510
GE2/1/3 GE2/1/3 GE2/1/3 GE2/1/3
GE2/1/3 GE2/1/3 GE2/1/3 GE2/1/3
Figure 1-2 Fiber which is not connected or disconnected
DLDP provides the following features:
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.
When auto-negotiation mechanism and DLDP are enabled, they work together to
detect and disable physical and logical unidirectional links, and to prevent the
failure of other protocols, such as Spanning Tree Protocol (STP).
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.

1.1.1 DLDP Fundamentals

I. DLDP status
A link can be in one of these DLDP states: initial, inactive, active, advertisement, probe,
disable, and delaydown.
Table 1-1 DLDP status
Status
Initial
Inactive
Active
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SwitchA SwitchA SwitchA SwitchA
GE2/1/4 GE2/1/4 GE2/1/4 GE2/1/4
GE2/1/4 GE2/1/4 GE2/1/4 GE2/1/4
SwitchB SwitchB SwitchB SwitchB
PC PC PC PC
DLDP is not enabled.
DLDP is enabled but the corresponding link is down
DLDP is enabled and the link is up, or an neighbor entry is cleared
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
Huawei Technologies Proprietary
1-2
Chapter 1 DLDP Configuration
Description