Traffic Class Scheduling Policy; Figure 10 Strict Priority And Weighted Round Robin Scheduler; Table 27 Supported Scheduling Configurations - Brocade Communications Systems Converged Enhanced Ethernet 8000 Administrator's Manual

11
Scheduling
Deficit Weighted Round Robin (DWRR) is an improved version of WRR. DWRR remembers the
excess used when a queue goes over its bandwidth allocation and reduces the queue's bandwidth
allocation in the subsequent rounds. This way the actual bandwidth usage is closer to the defined
level when compared to WRR.

Traffic class scheduling policy

The traffic classes are numbered from 0 to 7; higher numbered traffic classes are considered
higher priority. Fabric OS v7.0.0 provides full flexibility in controlling the number of SP-to-WRR
queues. The number of SP queues is specified in N (SP1 through 8), then the highest priority traffic
classes are configured for SP service and the remaining eight are WRR serviced.
describes the set of scheduling configurations supported.
When you configure the QoS queue to use strict priority 4 (SP4), then traffic class 7 will use SP4,
traffic class 6 will use SP3, and so on down the list. You use the strict priority mappings to control
how the different traffic classes will be routed in the queue.
TABLE 27
Supported scheduling configurations
Traffic Class SP0
7 WRR8
6 WRR7
5 WRR6
4 WRR5
3 WRR4
2 WRR3
1 WRR2
0 WRR1
Figure 10
straightforward. All SP queues are considered strictly higher priority than WRR so they are serviced
first. Once all SP queues are drained, then the normal WRR scheduling behavior is applied to the
non-empty WRR queues.
FIGURE 10
Scheduling the QoS queue
To specify the schedule to use, perform the following steps from privileged EXEC mode.
1. Enter global configuration mode.
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DRAFT: BROCADE CONFIDENTIAL
SP1 SP2
SP1 SP2
WRR7 SP1
WRR6 WRR6
WRR5 WRR5
WRR4 WRR4
WRR3 WRR3
WRR2 WRR2
WRR1 WRR1
shows that extending the frame scheduler to a hybrid SP+WRR system is fairly
Strict priority and Weighted Round Robin scheduler
switch#configure terminal
SP3 SP4
SP3 SP4
SP2 SP3
SP1 SP2
WRR5 SP1
WRR4 WRR4
WRR3 WRR3
WRR2 WRR2
WRR1 WRR1
Converged Enhanced Ethernet Administrator's Guide
Table 27
SP5 SP6
SP5 SP6
SP4 SP5
SP3 SP4
SP2 SP3
SP1 SP2
WRR3 SP1
WRR2 WRR2
WRR1 WRR1
53-1002163-02
SP8
SP8
SP7
SP6
SP5
SP4
SP3
SP2
SP1