User Manual - Configuration Guide (Volume 3)

Chapter 3

Versatile Routing Platform

Congestion Management

III. CQ

C la s s ific a tio n

Q u e u e

Q u e u e 1

Q u e u e 2

...

1 0 %

1 0 %

P a c k e ts le a v in g th e in te rfa c e

P a c k e ts s e n t fr o m th is in te r fa c e

Q u e u e 1 6

D e q u e u in g d is p a tc h

3 0 %

Figure QC-3-4Schematic diagram of custom queuing

As shown in the figure above, CQ classifies the packets into 17 categories (corresponding to 17 queues in CQ) following the specified policy. According to its category, the packets queue up and enter the corresponding queue of CQ based on the first-in first-out policy. Of the 17 queues of CQ, No.0 queue is a system queue, and No.1 to No.16 are user queues. And the user can configure the proportion of interface bandwidth occupied for each user queue. When the queues are dispatched, the packets in the system queue are sent with priority until the queue is empty. Then according to the bandwidth configured beforehand, a specific amount of packets in No.1 to No.16 queues are sent out in the polling mode in sequence.

PQ assigns absolute priority to the packets with higher priority level compared with the packets with lower priority level. Although this ensures that the key service data can be transmitted with priority, the packets with lower priority level will all be congested if the bandwidth is occupied completely for transmitting massive packets with higher priority. If CQ is adopted, this case can be avoided. There are 17 queues in CQ. The user can configure the policy of flow classification, and specify the proportion of interface bandwidths occupied by the 16 user queues. Thus, the packets of different services are allocated with different bandwidths, ensuring that key services can get more bandwidths while preventing from no bandwidth available for ordinary services.

In the network diagram shown in figure QC-2-1, suppose the server of LAN 1 sends key service data to the server of LAN 2, and PC of LAN 1 sends ordinary service data to PC of LAN 2. The serial port connected with WAN is configured with CQ for congestion management. Key service data flow between the server enters queue A, and ordinary service data flow between PCs enters queue B. The proportion of interface bandwidth occupied by queue A against queue B is configured to 3:1 (for example, queue A in each dispatching can continuously send 6000 bytes of packets, and queue B in each dispatching can continuously send 2000 bytes of packets). In this way, CQ treats the two packet types of different services in different ways. When queue A is dispatched, the packets is sent continuously till the number of bytes being sent is no less than 6000 or the queue is empty, then CQ turns to dispatching the next user queue. When queue B is dispatched, the dispatching will not end till the number of bytes being sent continuously is no less than 2000 or the queue B is empty. In this way, if congestion occurs and there are always packets in queue A and B to be sent, from the statistics result it can be seen that the proportion of the bandwidths acquired by the key services against the bandwidths acquired by the ordinary services is approximately 3:1.

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Huawei v200r001 user manual Iii. Cq