Congestion avoidance on 6500
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Tail drop advanced |
WRED |
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Drops packets with a certain CoS when a certain threshold is reached When 50% of queue is filled, drop CoS 0 and 1 When 60% is filled, drop CoS 2 and 3 |
Defines a min and max threshold CoS 0 and 1 has a min threshold of 50 and max of 70. When queue reaches 50, WRED starts dropping packets in random and when it reaches 70 will drop all packets |
Scheduling
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WRR – Weighted Round Robin |
Strict Priority |
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Queues emptied in round robin fashion based on the weights By default, has 2 queues. Queue 1 is served 70% of the time and Queue 2 is served 30% of the time |
Always the priority queue will be emptied first. After each packet from the other queues are send, the priority queue will be checked and emptied |
Available queue configurations on 6500
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Map CoS to queue thresholds |
Cos 0 maps to Queue 1 Threshold 1 Cos 1 maps to Queue 1 threshold 2 |
set qos map 2q2t tx 1 1 cos 0 set qos map 2q2t tx 1 2 cos 1 |
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Define the threshold levels for tail drop or WRED |
Threshold 1 is 80 Threshold 2 is 100 |
set qos drop-threshold 2q2t tx queue 1 80 100 – tail drop set qos wred 2q2t tx queue 1 80 100 — WRED |
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Queue serving time |
Queue 1 served 5/260 Queue 2 served 255/260 |
set qos wrr 2q2t 5 255 |
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Assigning buffer length |
Queue 1 has 80 (low priority queue is assigned more buffer) Queue 2 has 20 |
set qos txq-ratio 2q2t 80 20 |
