D-Link DES-3550 Command Line Interface Reference Manual page 131

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>]
The Switch contains 4 hardware priority queues. Incoming packets must be mapped to
Description
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 you 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 you 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.
<class_id 0-3> − This specifies which of the four hardware priority queues the config
Parameters
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 3 specifies 3 X
16 = 48 ms. The queue will continue transmitting the last packet until it is finished when
the max_latency timer expires.
Restrictions Only administrator-level users can issue this command.
DES-3550 Layer 2 Fast Ethernet Switch
127