Brocade Multi-Service IronWare QoS and Traffic Management Configuration Guide (Supporting R05.6.00) - Manual (Page 71)

Multi-Service IronWare QoS and Traffic Management Configuration Guide 57
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Egress port and priority based rate shaping
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Configuring mixed strict priority and weight-based
scheduling
When configuring the mixed strict priority and weight-based scheduling option, queues 5 - 7 are
allocated to strict priority-based scheduling and queues 0 - 4 are allocated to weight-based
scheduling.
To configure mixed priority and weight-based scheduling use a command such as the following.
Brocade(config)# qos scheduler profile Mixed0 mixed 100 80 60 40 20
Syntax: [no] qos scheduler profile name mixed queue4-weight queue3-weight queue2-weight
queue1-weight queue0-weight
The queue4-weight variable defines the relative value for queue4 in calculating queue4’s allocated
bandwidth.
The queue3-weight variable defines the relative value for queue3 in calculating queue3’s allocated
bandwidth.
The queue2-weight variable defines the relative value for queue2 in calculating queue2’s allocated
bandwidth.
The queue1-weight variable defines the relative value for queue1 in calculating queue1’s allocated
bandwidth.
The queue0-weight variable defines the relative value for queue0 in calculating queue0’s allocated
bandwidth
The acceptable range for queuex-weight variables is 1-128.
Refer to “Calculating the values for WRR weight-based traffic scheduling” for information on
assigning queue0-weight to queue4-weight values.
Egress port and priority based rate shaping
Rate shaping is a mechanism to smooth out the variations in traffic above a certain rate. The
primary difference between rate shaping and rate limiting is that in rate limiting, traffic exceeding a
certain threshold is dropped. In rate shaping, the traffic that exceeds a threshold is buffered so
that the output from the buffer follows a more uniform pattern. Rate shaping is useful when
burstiness in the source stream needs to be smoothed out and a more uniform traffic flow is
expected at the destination.
NOTE
Because excess traffic is buffered, rate shaping must be used with caution. In general, it is not
advisable to rate shape delay-sensitive traffic.
Brocade devices support egress rate shaping. Egress rate shaping is supported per port or for each
priority queue on a specified port.