DLDP status
A link can be in one of these DLDP states: initial, inactive, active, advertisement, probe, disable, and
delaydown.
Table 17-2
DLDP status
Status
Description
Initial
Initial status before DLDP is enabled.
Inactive
DLDP is enabled but the corresponding link is down
Active
This state indicates that:
z
DLDP is enabled and the link is up.
z
The neighbor entries are cleared.
Advertisement
All neighbors communicate normally in both directions, or DLDP remains in
active state for more than five seconds and enters this status. It is a stable
state where no unidirectional link is found
Probe
DLDP sends packets to check whether the link is a unidirectional link. It
enables the probe sending timer and an echo waiting timer for each target
neighbor.
Disable
DLDP detects a unidirectional link, or finds (in enhanced mode) that a
neighbor disappears. In this case, DLDP does not receive or send DLDP
packets.
Delaydown
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.
DLDP timers
Table 17-3
DLDP timers
Timer
Description
Advertisement
sending timer
Interval between sending advertisement packets, which can be configured on
a command line interface.
By default, the timer length is 5 seconds.
Probe sending
timer
The interval is 0.5 seconds. In the probe state, DLDP sends two probe packets
in a second.
Echo waiting timer
It is enabled when DLDP enters the probe state. The echo waiting timer length
is 10 seconds.
If no echo packet is received from the neighbor when the Echo waiting timer
expires, the state of the local end is set to unidirectional link (one-way audio)
and the state machine turns into the
disable
state. DLDP outputs log and
tracking information, sends flush packets. Depending on the user-defined
DLDP down mode, DLDP disables the local port automatically or prompts you
to disable the port manually. At the same time, DLDP deletes the neighbor
entry.
17-4
