IP-COM G3210P, Руководство пользователя

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100
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Advanced Settings
When congestion occurs on the network, the problem that many packets compete for
resources must be solved, usually in the way of queue scheduling. The switch provides
two schedule modes: SP(Strict-Priority
）
and WRR (Weighted Round Robin).
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Strict Priority Mode
Strict Priority Queueing is specially designed to meet the demands of critical services or
applications. When congestion occurs on the network, the system will ask for service
preferentially to reduce response delay. For example, 4 egress queues 3, 2, 1 and 0 with
descending priority are configured on a port.
Then under SP algorithm, the port strictly prioritizes packets from higher priority queue
over those from lower priority queue. Namely, packets in the queue with lower priority are
sent only when the queue with higher priority is empty. Thus High-priority packets are
always processed before those of less priority. Medium-priority packets are always
processed before low-priority packets. The lowest priority queue would be serviced only
when highest priority queues had no packets buffered.
Disadvantages of SP: The SP queueing gives absolute priority to high-priority packets
over low-priority traffic; it should be used with care. The moment a higher priority packet
arrived in its queue, however, servicing of the lower priority packets would be interrupted
in favor of the higher priority queue or packets will be dropped if the amount of
high-priority traffic is too great to be emptied within a short time.
The disadvantage of SP queue is that: if there are packets in the queues with higher
priority for a long time in congestion, the packets in the queues with lower priority will be
“starved to death” because they are not served.
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Weight Round Robin Mode (WRR)