z
In normal DLDP mode, only fiber cross-connected unidirectional links (as shown in
Figure 17-1
)
can be detected.
z
In enhanced DLDP mode, two types of unidirectional links can be detected. One is fiber
cross-connected links (as shown in
Figure 17-1
). The other refers to fiber pairs with one fiber not
connected or disconnected (as shown in
Figure 17-2
). To detect unidirectional links that are of the
latter type, you need to configure the ports to operate at specific speed and in full duplex mode.
Otherwise, DLDP cannot take effect.
DLDP implementation
1) If the DLDP-enabled link is up, DLDP sends DLDP packets to the peer device, and analyzes and
processes the DLDP packets received from the peer device. DLDP in different states sends
different types of packets.
Table 17-5
Types of packets sent by DLDP
DLDP state
Packet type
Active
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packets
Probe Probe
packets
2) DLDP analyzes and processes received packets from the peer device as follows:
z
In authentication mode, DLDP authenticates the packets, and discards those failing to pass the
authentication.
z
DLDP processes the received DLDP packets.
Table 17-6
Process received DLDP packets
Packet type
Processing procedure
If this neighbor entry does not exist on the local device,
DLDP creates the neighbor entry, enables the entry
aging timer, and switches to the probe state.
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packet
Extracts neighbor
information
If the neighbor entry already exists on the local device,
DLDP updates the entry aging timer.
Flush packet
Deletes the neighbor entry from the local device
Creates the neighbor entry if this neighbor entry does
not exist on the local device.
Probe packet
Sends echo packets
containing both
neighbor and its own
information to the
peer
If the neighbor entry already exists on the local device,
updates the entry aging timer.
17-6
