Question

Q2.3. (15%) Suppose that the WFQ scheduling policy is applied to a buffer that supports three classes (of priority packets), and suppose the weights are class has XT ose at sequence might the three a large number of packets in the bulTer. In wh classes be served in order to achieve the WFQ weights?

Answer 1

a)

The WFQ (Weighted Fair Queuing) scheduling is a circular order a round roubin strategy in ascending order depends on weights.

Assume the three classes weights are 0.25, 0.5, and 0.75 respectively.

If same weight have for two or more classes then give highest order is the first preference class.

The sequence order that the three classes served is :1 2 1 3 1 2 1 3….

Another possible sequence order that the three class are: 1 1 2 1 1 3 1 1 2 1 1…

b)

Consider the classes 1 and 2 have a large number of packets in the buffer, and there are no class 3 packets in the buffer.

The sequence might the three classes be served in to achieve the WFQ weights are 1 1 2 1 1 2 1 1 2….

Another sequence sequence might the three classes be served in to achieve the WFQ weights are 1 1 3 1 1 3 1 1 …

or Another solution might be-

(a) Possibility 1: 1 1 2 3 1 1 2 3 1 1 2 3 … Possibility 2: 1 2 1 3 1 2 1 3 1 2 1 3 …

(b) The new value of weights for class 1 and class 2 has to satisfy: w1new = 2*w2new w1new = 2/3 w1new + w2new = 1 w2new = 1/3 Possible solution: 1 1 2 1 1 2 1 1 2