Cbq - HP MSR4080 Configuration Manual

Short packets and long packets are equally scheduled. If long packets and short packets exist in
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queues, statistically the short packets are scheduled preferentially to reduce the jitter between
packets.
WFQ considers weights when determining the queue scheduling order. Statistically, WFQ gives
high-priority traffic more scheduling opportunities than low-priority traffic. To balance the delay of every
traffic flow, WFQ automatically classifies traffic according to the "session" information of traffic, and
attempts to provide as many queues as possible for traffic flows. The session information of traffic
includes protocol type, TCP or UDP source/destination port numbers, source/destination IP addresses, IP
precedence bits in the ToS field. 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, 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 special situations. For example, WFQ is used in the assured forwarding (AF) services of the
RSVP, and WFQ is used to schedule buffered packets in GTS.

CBQ

Figure 16 CBQ
Class-based queuing (CBQ) extends WFQ by supporting user-defined classes. When network
congestion occurs, CBQ uses user-defined traffic match criteria to enqueue packets. Before packets are
enqueued, congestion avoidance actions, such as tail drop or WRED and bandwidth restriction check,
are performed. When being dequeued, packets are scheduled by WFQ.
CBQ provides the following queues:
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