3Com WX3000 Series Operation Manual page 154

Timer
Enhanced timer
Delaydown timer
DLDP operating mode
DLDP can operate in two modes: normal and enhanced.
Table 1-3 DLDP operating mode and neighbor entry aging
DLDP operating
mode
Normal mode
Enhanced mode
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.
In enhanced mode, if no packet is received from the neighbor
when the entry aging timer expires, DLDP enables the enhanced
timer for the neighbor. The timeout time for the enhanced timer is
10 seconds.
The enhanced timer then sends one probe packets every one
second and totally eight packets continuously to the neighbor.
If no echo packet is received from the neighbor when the
Enhanced timer expires, the local end is set to unidirectional
communication status and the state machine turns into disable
status. DLDP outputs log and tracking information, and sends
flush packets. Depending on the user-defined DLDP down mode,
DLDP disables the local port automatically or prompt the user to
disable the port manually. DLDP deletes the neighbor entry.
When a device in the active, advertisement, or probe DLDP state
receives a port down message, it does not removes the
corresponding neighbor immediately, neither does it changes to
the inactive state. Instead, it changes to the delaydown state first.
When a device changes to the delaydown state, the related DLDP
neighbor information remains, and the Delaydown timer is
triggered. The Delaydown timer is configurable and ranges from 1
to 5 seconds.
A device in the delaydown state only responds to port up
messages.
A device in the delaydown state resumes its original DLDP state if
it receives a port up message before the delaydown timer expires.
Otherwise, it removes the DLDP neighbor information and
changes to the inactive state.
Whether DLDP
probes neighbor
during neighbor
entry aging
No
Yes
1-4
Description
Whether entry aging
timer is enabled
during neighbor
entry aging
Yes (the neighbor
entry ages after the
entry aging timer
expires)
Yes (the enhanced
timer is enabled after
the entry aging timer
expires)
Whether enhanced
timer is enabled
when entry aging
timer expire
No
Yes (When the
enhanced timer
expires, the local end
is set to single pass
status, and the
neighbor entry ages)