3Com Switch 4800G 24-Port Configuration Manual page 189

Table 34 Procedures for processing different types of DLDP packets
Packet type Processing procedure
Echo packet Retrieves the
neighbor
information.
Disable packet Check to see if
the local port is in
Disable state.
RecoverProbe Check to see if
packet the local port is in
Disable or
Advertisement
state.
RecoverEcho Check to see if
packet the local port is in
Disable state.
LinkDown packet Check to see if
the local port
operates in
Enhanced mode.
3 If no echo packet is received from the neighbor, DLDP performs the following
processing.
Table 35 Processing procedure when no echo packet is received from the neighbor
No echo packet received from the
neighbor
In normal mode, no echo packet is
received when the Echo timer expires.
In enhanced mode, no echo packet is
received when the enhanced timer
expires.
DLDP neighbor state
A DLDP neighbor can be in one of the three states described in Table 36. You can
check the state of a DLDP neighbor by using the display dldp command.
Table 36 Description on DLDP neighbor states
DLDP neighbor
state Description
Unknown A neighbor is in this state when it is just detected and is being probed.
No information indicating the state of the neighbor is received. A
neighbor is in this state only when it is being probed. It transits to Two
way state or Unidirectional state after the probe operation finishes.
If the corresponding neighbor entry does not exist,
creates the neighbor entry, triggers the Entry timer,
and transits to Probe state.
The If the neighbor information it carries
correspondi conflicts with the corresponding locally
ng neighbor maintained neighbor entry, drops the
entry packet.
already
Otherwise, sets the flag of the neighbor
exists
as two-way connected. In addition, if
the flags of all the neighbors are
two-way connected, the device transits
from Probe state to Advertisement
state and disables the Echo timer.
If yes, no process is performed.
If not, the local port transits to Disable state.
If not, no process is performed.
If yes, returns RecoverEcho packets.
If not, no process is performed.
If yes, the local port transits to Active state if the
neighbor information the packet carries is consistent
with the local port information.
If not, no process is performed.
If yes and the local port is not in Disable state, the
local transits to Disable state.
Processing procedure
DLDP transits to the Disable state, outputs log and
tracking information, and sends Disable packets. In
addition, depending on the user-defined DLDP
down mode, DLDP shuts down the local port or
prompts users to shut down the port, and removes
the corresponding neighbor entry.
Overview 189