H3C Technologies H3C WX6000 Series Access Controllers - Manual (Page 296)

27-4
DLDP timer Description
Entry timer
When a new neighbor joins, a neighbor entry is created and the corresponding
entry timer is triggered. And when a DLDP packet is received, the device
updates the corresponding neighbor entry and the entry aging timer.
In the normal mode, if no packet is received from a neighbor when the
corresponding entry aging timer expires, DLDP sends advertisement packets
with RSY tags and removes the neighbor entry.
In the enhanced mode, if no packet is received from a neighbor when the Entry
timer expires, DLDP triggers the enhanced timer.
The setting of an Entry timer is three times that of the Advertisement timer.
Enhanced timer
In the enhanced mode, this timer is triggered if no packet is received from a
neighbor when the entry aging timer expires. Enhanced timer is set to 10
seconds.
After the Enhanced timer is triggered, the device sends up to eight probe
packets to the neighbor at a frequency of one packet per second. If no Echo
packet is received from the neighbor when the Echo timer expires, the link is set
as a unidirectional link and the device transits to the Disable state. In this case,
the device sends Disable packets, prompts the user to shut down the port or
shuts down the port automatically (depending on the DLDP down mode
configured), and removes the corresponding neighbor entries.
DelayDown timer
A device in the Active, Advertisement, or Probe DLDP link state transits to
DelayDown state rather than removes the corresponding neighbor entry and
transits to the Inactive state when it detects a port-down event.
When a device transits to this state, the DelayDown timer is triggered. The
setting of the timer ranges from 1 to 5 (in seconds). A device in DelayDown state
only responds to port-up events.
A device in the DelayDown state resumes its original DLDP state if it detects a
port-up event before the DelayDown timer expires. Otherwise, it removes the
corresponding DLDP neighbor information and transits to the Inactive state.
RecoverProbe timer
Determines the interval to RecoverProbe packets, which are used to detect
whether a unidirectional link is restored. This timer is set to 2 seconds.
DLDP mode
DLDP can operate in two modes: normal mode and enhanced mode, as described below.
z
In normal DLDP mode, when an entry timer expires, the device removes the corresponding
neighbor entry and sends an Advertisement packet with RSY tag.
z
In enhanced DLDP mode, when an entry timer expires, the Enhanced timer is triggered and the
device sends up to eight Probe packets at a frequency of one packet per second to test the
neighbor. If no Echo packet is received from the neighbor when the Echo timer expires, the device
transits to the Disable state.
Table 27-3 DLDP mode and neighbor entry aging
DLDP mode
Detecting a neighbor
after the corresponding
neighbor entry ages out
Removing the neighbor
entry immediately after the
Entry timer expires
Triggering the Enhanced
timer after an Entry timer
expires
Normal DLDP
mode
No Yes No
Enhanced
DLDP mode
Yes No Yes
The enhanced DLDP mode is designed for addressing black holes. It prevents the cases where one end
of a link is up and the other is down. If you configure the speed and the duplex mode by force on a