H3C H3C S5100-SI, Operation Manual, Page: 175 / 830

1-6
z
In normal DLDP mode, only fiber cross-connected unidirectional links (as shown in Figure 1-1 ) 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 1-1 ). The other refers to fiber pairs with one fiber not
connected or disconnected (as shown in Figure 1-2 ). 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/processes the DLDP packets received from the peer device. DLDP packets sent in
different DLDP states are of different types.
Table 1-5 DLDP state and DLDP packet type
DLDP state Type of the DLDP packets sent
Active Advertisement packets, with the RSY flag set or not set.
Advertisement Advertisement packets
Probe Probe packets
2) A DLDP packet received is processed as follows:
z
In authentication mode, the DLDP packet is authenticated and is then dropped if it fails the
authentication.
z
The packet is further processed, as described in Table 1-6 .
You can prevent network attacks and illegal detect through DLDP authentication. Three DLDP
authentication modes exist: non-authentication, plain text authentication, MD5 authentication.
Table 1-6 The procedure to process a received DLDP packet
Packet type Processing procedure
If the corresponding neighbor entry does not exist on the
local device, DLDP creates the neighbor entry, triggers
the entry aging timer, and switches to the probe state.
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packet Extracts neighbor
information
If the corresponding neighbor entry already exists on the
local device, DLDP resets the aging timer of the entry.
Flush packet Removes the neighbor entry from the local device