3Com 4210 PWR Configuration Manual page 308

306 C 28: Q S C
HAPTER O
Burst
ONFIGURATION
In the following section, weighted round robin (WRR), and HQ-WRR (High
Queue-WRR) queues are introduced.
WRR queuing
Figure 96 Diagram for WRR queuing
Packets to be sent
through this port
classification
WRR queue-scheduling algorithm schedules all the queues in turn and every
queue can be assured of a certain service time. Assume there are eight priority
queues on a port. WRR configures a weight value for each queue, which is w7,
w6, w5, w4, w3, w2, w1, and w0. The weight value indicates the proportion of
obtaining resources. On a 100 M port, configure the weight value of WRR
queue-scheduling algorithm to 50, 50, 30, 30, 10, 10, 10, and 10 (corresponding
to w7, w6, w5, w4, w3, w2, w1, and w0 in order). In this way, the queue with the
lowest priority can get 5 Mbps bandwidth at least. Another advantage of WRR
queue is that: though the queues are scheduled in order, the service time for each
queue is not fixed; that is to say, if a queue is empty, the next queue will be
scheduled. In this way, the bandwidth resources are made full use.
HQ-WRR queuing
HQ-WRR is an improvement over WRR. With queue 3 allocated with the highest
priority, the switch will ensure that this queue get served first and will perform
round-robin scheduling to the other three queues when the traffic has exceeded
the bandwidth capacity of a port.
The Burst function can provide better packet cache function and traffic forwarding
performance. It is suitable for networks where
Large amount of broadcast/multicast packets and large burst traffic exist.
■
Packets of high-rate links are forwarded to low-rate links or packets of multiple
■
links with the equal rates are forwarded to a single link that is of the same rate
as that of the incoming links.
Queue 1 Weight 1
Queue 2 Weight 2
Queue 2 weight 2
Queue N - 1 Weight N - 1
Queue N - 1 weight N - 1
Packet
Queue N Weight N
Queue N weight N
Sent packets
Interface
Queue Sending queue
scheduling