HP A6600 Configuration Manual page 55

WFQ
Figure 18 WFQ
Packets to be sent
through this interface
Before WFQ is introduced, ensure you have understood FQ. FQ is designed for fairly allocating network
resources to reduce delay and jitter of each traffic flow as possible. In an attempt to balance the interests of
all parties, FQ follows these principles:
 Different queues have fair dispatching opportunities for delay balancing among streams.
 Short packets and long packets are fairly scheduled: if long packets and short packets exist in queues,
statistically the short packets should be scheduled preferentially to reduce the jitter between packets on
the whole.
Compared with FQ, WFQ takes weights into account when determining the queue scheduling order.
Statistically, WFQ gives high-priority traffic more scheduling opportunities than low-priority traffic. WFQ can
automatically classify traffic according to the ―session‖ information of traffic (protocol type, TCP or UDP
source/destination port numbers, source/destination IP addresses, IP precedence bits in the ToS field, and
so on), and try to provide as many queues as possible so each traffic flow can be put into these queues to
balance the delay of every traffic flow on a whole. When dequeuing packets, WFQ assigns the outgoing
interface bandwidth to each traffic flow by precedence. The higher precedence value a traffic flow has, the
more bandwidth it gets.
For example, assume that five flows exist in the current interface with precedence 0, 1, 2, 3, and 4,
respectively. The total 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 bandwidth
quota. The bandwidth percentages for flows are 1/15, 2/15, 3/15, 4/15, and 5/15, respectively.
Because WFQ can balance the delay and jitter of each flow when congestion occurs, it is suitable for
handling some special occasions. For example, WFQ is used in the AF services of the RSVP. In GTS, WFQ
schedules buffered packets.
Queue 1 weight 1
Queue 2 weight 2
......
Queue N-1 weight N-1
Classify
Queue N weight N
Packets sent
Interface
Schedule Sending queue
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