3Com Switch 7750 Configuration Guide Guide

DLDP Overview 203
DLDP implementation
1 If the DLDP-enabled link is up, DLDP sends DLDP packets to the peer device, and
analyses and processes DLDP packets received from the peer device. DLDP in
different status sends different packets.
2 DLDP analyzes and processes received packets as follows:
■ In authentication mode, DLDP authenticates the packets, and discards those do
not pass the authentication.
■ DLDP processes the received DLDP packets.
3 If no echo packet is received from the neighbor, DLDP performs the following
processing:
Table 130 Types of packets sent by DLDP
DLDP status Packet types
Active Advertisement packets, including those with or without RSY tags
Advertisement Advertisement packets
Probe Probe packets
Table 131 Process received DLDP packets
Packet type Processing procedure
Advertisement
packet
Extract neighbor
information
If this neighbor entry does not exist on the local device,
DLDP creates the neighbor entry, enables the entry
aging timer of the neighbor entry, and turns to probe
status.
If the neighbor entry already exists on the local device,
DLDP refreshes the entry aging timer.
Flush packet Delete the neighbor entry from the local device
Probe packet
Send echo packets
containing both
neighbor and its
own information to
the peer
Create the neighbor entry if this neighbor entry does
not exist on the local device.
If the neighbor entry already exists on the local device,
refresh the entry aging timer.
Echo packet
Check
whether
the local
device is
in probe
status
No Discard this echo packet
Yes
Check whether
neighbor
information in
the packet is the
same as that on
the local device
No Discard this echo packet
Yes
Set the neighbor flag bit to
bidirectional
If all neighbors are in
bidirectional communication
state, DLDP turns from
probe status to
advertisement status, and
sets the echo waiting timer
to 0.