Traffic Class Scheduling Policy; Figure 8 Wrr Schedule - Two Queues; Table 20 Supported Scheduling Configurations - Dell 53-1002116-01 Administrator's Manual

Figure 8
higher numbered queue is considered higher priority (WRR2) and the weights indicate the network
bandwidth should be allocated in a 2:1 ratio between the two queues. In
receive 66 percent of bandwidth and WRR1 receives 33 percent. The WRR scheduler tracks the
extra bandwidth used and subtracts it from the bandwidth allocation for the next cycle through the
queues. In this way, the bandwidth utilization statistically matches the queue weights over longer
time periods.
FIGURE 8
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. The Dell M8428-k 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 20 Supported scheduling configurations
Traffic Class SP0
7 WRR8
6 WRR7
5 WRR6
4 WRR5
3 WRR4
2 WRR3
1 WRR2
0 WRR1
Dell Converged Enhanced Ethernet Administrator's Guide
53-1002116-01
describes the frame scheduling order for a WRR scheduler servicing two WRR queues. The
WRR schedule — two queues
SP1 SP2
SP1 SP2
WRR7 SP1
WRR6 WRR6
WRR5 WRR5
WRR4 WRR4
WRR3 WRR3
WRR2 WRR2
WRR1 WRR1
SP3 SP4 SP5
SP3 SP4 SP5
SP2 SP3 SP4
SP1 SP2 SP3
WRR5 SP1 SP2
WRR4 WRR4 SP1
WRR3 WRR3 WRR3
WRR2 WRR2 WRR2
WRR1 WRR1 WRR1
10
Scheduling
Figure 8 WRR2 should
Table 20
SP6 SP8
SP6 SP8
SP5 SP7
SP4 SP6
SP3 SP5
SP2 SP4
SP1 SP3
WRR2 SP2
WRR1 SP1
105