3Com 4500 Configuration Manual page 155

Table 1-5 DLDP state and DLDP packet type
DLDP state
Active
Advertisement
Probe
2) A DLDP packet received is processed as follows:
In authentication mode, the DLDP packet is authenticated and is then dropped if it fails the
authentication.
The packet is further processed, as described in
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
Advertisement Extracts neighbor
packet information
Flush packet Removes the neighbor entry from the local device
Sends echo packets
containing both
Probe packet neighbor and its own
information to the
peer
Checks to
see if the
Echo packet local device
is in the
probe state
3) If no echo packet is received from the neighbor, DLDP performs the following processing:
Type of the DLDP packets sent
Advertisement packets, with the RSY flag set or not set.
Advertisement packets
Probe packets
Table
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.
If the corresponding neighbor entry already exists on the
local device, DLDP resets the aging timer of the entry.
Creates the neighbor entry if it does not exist on the local
device.
Resets the aging timer of the entry if the neighbor entry
already exists on the local device.
No Drops the echo packet
Checks to
see if the
neighbor
information
Yes contained in
the packet is
the same as
that on the
local device
1-7
1-6.
No Drops the echo packet
Sets the flag bit of the neighbor
to bidirectional link
If all neighbors are in the
Yes
bidirectional link state, DLDP
switches from the probe state to
the advertisement state, and
sets the echo waiting timer to 0.