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(b) Assume a router uses 4 buffers to store different traffic flows. It receives

ID: 3874542 • Letter: #

Question

(b) Assume a router uses 4 buffers to store different traffic flows. It receives the packets listed in Table Q2 at about the same time, in the order listed. All buffers are initially empty, and transmission is not possible until all packets are received. Packet Size Flow 240 240 360 320 200 200 160 160 Table Q2 Give the order in which packets are transmitted assuming Fair ueuing appliedto all buffers. 6 marks] ( Give the order in which packets are transmitted assuming that buffer 1 is a Priority Queue, and that buffers 2, 3 and 4 are scheduled using Weighted Fair Queuing, with flow 2 having weight 4, flow 3 having weight 2 and flow 4 having weight

Explanation / Answer

Answer (i):

According to Fair Queueing in Packet fair queueing we send the packet which has smallest flow. Henccethe order in which packets will flow are:

Packet 1 (240), Packet 2(240), Packet 4(320), packet 3(360), packet 5(200), packet 6(200), packet 7(100),, packet 8(100).

Answer (ii):

Flow 2 has weight: 160, Flow 3 has weight 360,320; Flow 4 has weight 240,240

The flow of packets will be Packet 1 and packet 2 will have total weight 160=160=320

The flow of packets will be Packet 4 and Packet 3 having wieght 320+360=680

Th eflow of apckets will be Packet 7 and Packet 8 having eight 240+240=480

Hence the correct flow will be wrt to packets: Pakcet 1, packet2, packet 7, packet 8, packet 4, packet 3.