HP A5120 EI Series Configuration Manual page 46

In contrast to SP, WRR queuing schedules queues in a round-robin way to guarantee each queue certain
service time in each scheduling cycle. In WRR queuing, each queue has a scheduling weight, which
determines the percentage of resources assigned to the queue.
The A5120 EI switches support packet-based WRR, which allocates bandwidth to queues in terms of
packets. For example, configure the scheduling weights of queues 0 through 7 on a port as 5, 5, 3, 3, 1,
1, 1, and 1. Then, the switch schedules these queues in a round-robin fashion and dequeues a certain
number of packets from a queue according to its weight.
WRR also improves bandwidth use efficiency. With WRR, the service time for each queue is not fixed. If a
queue is empty, WRR immediately moves to the next queue.
WFQ queuing
Figure 15 Schematic diagram for WFQ queuing
Packets to be sent through
this port
WFQ achieves almost the same queuing effect as WRR, except that WFQ supports the minimum
guaranteed bandwidth configuration.
You can configure minimum guaranteed bandwidth for each WFQ queue to assure each WFQ queue of
the specified bandwidth when congestion occurs. The assignable bandwidth is allocated to queues based
on queue priority (assignable bandwidth = total bandwidth – the sum of the minimum guaranteed
bandwidth for each queue).
For example, assume the total bandwidth of a port is 10 Mbps, and the port has five flows, with the
precedence being 0, 1, 2, 3, and 4 and the minimum guaranteed bandwidth being 128 kbps, 128 kbps,
128 kbps, 64 kbps, and 64 kbps respectively.
The assignable bandwidth = 10 Mbps – (128 kbps + 128 kbps + 128 kbps + 64 kbps + and 64

kbps) = 9.5 Mbps.
The total assignable bandwidth quota is the sum of all the (precedence value + 1)s, 1 + 2 + 3 + 4 +

5 = 15.
The bandwidth percentage assigned to each flow is (precedence value of the flow + 1)/total

assignable bandwidth quota. The bandwidth percentages for the flows are 1/15, 2/15, 3/15,
4/15, and 5/15, respectively.
The bandwidth assigned to a queue = the minimum guaranteed bandwidth + the bandwidth

allocated to the queue from the assignable bandwidth.
Queue 1 Band width 1
Queue 2 Band width 2
......
Queue N-1 Band width N-1
Packet
classification
Queue N Band width N
Sent packets
Sending queue
Queue
scheduling
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Interface