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DES-3500 Layer 2 Fast Ethernet Switch CLI Reference Manual
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9 no_limit no_limit no_limit no_limit
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DES-3526:admin#
config scheduling
Purpose Used to configure the traffic scheduling mechanism for each COS
queue.
Syntax
config scheduling <class_id 0-3> [max_packet <value 0-255> |
max_latency <value 0-255>]
Description The Switch contains 4 hardware priority queues. Incoming packets
must be mapped to one of these four queues. This command is used to
specify the rotation by which these four hardware priority queues are
emptied.
The Switch’s default (if the config scheduling command is not used, or
if the config scheduling command is entered with both max_packet and
max_latency parameters are set to 0) is to empty the 4 hardware
priority queues in order − from the highest priority queue (hardware
queue 3) to the lowest priority queue (hardware queue 0). Each
hardware queue will transmit all of the packets in its buffer before
allowing the next lower priority queue to transmit its packets. When the
lowest hardware priority queue has finished transmitting all of its
packets, the highest hardware priority queue can again transmit any
packets it may have received.
The max_packets parameter allows the user to specify the maximum
number of packets a given hardware priority queue can transmit before
allowing the next lowest hardware priority queue to begin transmitting
its packets. A value between 0 and 255 can be specified. For example,
if a value of 3 is specified, then the highest hardware priority queue
(number 3) will be allowed to transmit 3 packets − then the next lowest
hardware priority queue (number 2) will be allowed to transmit 3
packets, and so on, until all of the queues have transmitted 3 packets.
The process will then repeat.
The max_latency parameter allows users to specify the maximum
amount of time that packets are delayed before being transmitted to a
given hardware priority queue. A value between 0 and 255 can be
specified. This number is then multiplied by 16 ms to determine the
maximum latency. For example, if 3 is specified, the maximum latency
allowed will be 3 X 16 = 48 ms.
When the specified hardware priority queue has been waiting to
transmit packets for this amount of time, the current queue will finish
transmitting its current packet, and then allow the hardware priority
queue whose max_latency timer has expired to begin transmitting
packets.
Parameters
<class_id 0-3> − This specifies which of the four hardware priority
queues the config scheduling command will apply to. The four
hardware priority queues are identified by number − from 0 to 3 − with
the 0 queue being the lowest priority.
max_packet <value 0-255> − Specifies the maximum number of
packets the above specified hardware priority queue will be allowed to
transmit before allowing the next lowest priority queue to transmit its
packets. A value between 0 and 255 can be specified.
max_latency <value 0-255> − Specifies the maximum amount of time
the above specified hardware priority queue will be allowed to transmit
packets before allowing the next lowest hardware priority queue to
begin transmitting its packets. A value between 0 and 255 can be
specified − with this value multiplied by 16 ms to arrive at the total
allowed time for the queue to transmit packets. For example, a value of