H3C Technologies H3C S3600 Series Switches - Manual (Page 226)

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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 and
processes the DLDP packets received from the peer device. DLDP in different states sends
different types of packets.
Table 1-5 Types of packets sent by DLDP
DLDP state Packet type
Active Advertisement packets, including those with or without an RSY tag
Advertisement Advertisement 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 1-6 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.