D-Link DES-3326S Layer 3 Switch CLI Reference
config scheduling
Purpose Used to configure traffic scheduling for each of the Switch’s QoS
queues.
Syntax
config scheduling <class_id 0-3> {max_packet <value 0-
255>|max_latency <value 0-255>}
Description The Switch contains four hardware priority queues per device.
The Switch’s default settings draw down the four hardware
queues in order, from the highest priority (Class 3) to the lowest
priority (Class 0). Starting with the highest priority queue
(Class 3), the highest priority queue will transmit all of the packets
and empty its buffer before allowing the next lower priority queue
to transmit its packets. The next highest priority queue will empty
before proceeding to the next queue and so on. Lower priority
queues are allowed to transmit only if
the higher priority queue(s)
in the buffer are completely emptied. Packets in the higher priority
queues are always emptied before any in the lower priority
queues regardless of latency or volume of the lower priority
queues.
The default settings for QoS scheduling employ this strict priority
scheme to empty priority queues.
The config scheduling command can be used to specify the
round robin rotation by which these four hardware priority queues
are reduced. To use a round-robin scheme, the max_packets
parameters and/or the max_latency parameters must be changed
from the default value of 0.
The max_packets parameter allows you to specify the maximum
number of packets a given priority queue can transmit before
allowing the next lowest priority queue to begin transmitting its
packets. A value between 0 and 255 packets can be specified.
For example, if a value of 5 is specified, then the highest priority
queue (queue 3) will be allowed to transmit 5 packets. Then the
next lower priority queue (queue 2) will be allowed to transmit 5
packets, and so on, until all of the queues have transmitted 5
packets. The process will then repeat.
The max_latency parameter allows you to specify the maximum
amount of time that packets will be delayed before being
transmitted. For a given priority queue, a value between 0 and
255 can be specified. This number is then multiplied by 16
milliseconds to determine the maximum allowed latency. For
example, if 3 is specified for queue 3, the maximum latency
allowed will be 3 X 16 ms = 48 ms. When queue 3 has been
waiting to transmit packets for longer than 48 ms, the currently
transmitting priority queue is allowed to finish transmitting its
current packet, and then queue 2 is allowed to begin transmitting
its packets.
Parameters
<class_id> − Specifies which of the four priority queues the
config scheduling command will be applied to. The four priority
queues are identified by number − from 0 to 3 − with queue 3
being the highest priority.
max_packet <value 0-255> − Specifies the maximum number of
packets the above specified priority queue will be allowed to
transmit before allowing the next lowest priority queue to transmit
its packets. A value between 0 and 255 packets can be
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