1-3
State
Indicates…
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All neighbors are bi-directionally reachable or DLDP has been in
active state for more than five seconds. This is a relatively stable
state where no unidirectional link has been detected.
Probe
DLDP enters this state if it receives a packet from an unknown
neighbor. In this state, DLDP sends packets to check whether the
link is unidirectional. As soon as DLDP transits to this state, a probe
timer starts and an echo timeout timer starts for each neighbor to be
probed.
Disable
A port enters this state when:
z
A unidirectional link is detected.
z
The contact with the neighbor in enhanced mode gets lost.
In this state, the port does not receive or send packets other than
DLDPDUs.
DelayDown
A port in the Active, Advertisement, or Probe DLDP link state transits
to this state rather than removes the corresponding neighbor entry
and transits to the Inactive state when it detects a port-down event.
When a port transits to this state, the DelayDown timer is triggered.
DLDP timers
Table 1-2
DLDP timers
DLDP timer
Description
Active timer
Determines the Interval for sending Advertisement packets with RSY
tags, which defaults to 1 second. That is, a device in the active DLDP
link state sends one Advertisement packet with RSY tags every second
by default. The maximum number of advertisement packets with RSY
tags that can be sent successively is 5.
Advertisement timer
Determines the interval to send advertisement packets, which defaults
to 5 seconds.
Probe timer
Determines the interval to send Probe packets, which defaults to 0.5
seconds. That is, a device in the probe state sends two Probe packets
every second by default. The maximum number of Probe packets that
can be sent successively is 10.
Echo timer
This timer is set to 10 seconds and is triggered when a device transits to
the Probe state or an enhanced detect is launched. When the Echo
timer expires and no Echo packet has been received from a neighbor
device, the state of the link is set to unidirectional 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.
Entry timer
When a new neighbor joins, a neighbor entry is created and the
corresponding entry timer is triggered. 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.
