Select all right choices while avoid selecting wrong ones: Refer to Fig. above.

Question

Select all right choices while avoid selecting wrong ones:

Refer to Fig. above. Flow 1 and flow 2 are the flows of traffic from host A to host B and from host C to host B respectively. Assume host A and host C transmit towards router R at rate R1 and R2 respectively, and R1+R2 >= R, where R is the maximum outgoing transmission rate of router R towards host B. Assume A and C utilize UDP and do not retransmit upon packet losses. Adding more buffer capacity at router R will

a) Reduce the chance of packet loss

b) Reduce the average queuing delay for flows 1 and 2

c) Increase the average queuing delay for flows 1 and 2

d) increase the throughput seen at host B. (The throughput is the combined throughput of flows 1 and 2)

Explanation / Answer

Correction choices are a) and d)

On increasing the buffer size, obviously packets coming from A and C will get queued in available buffer space of Router R .Earlier the queue was getting filled quickly due to its small size leading to drop of packets.But with increased queue size of buffer ,lesses no. of packets will be dropped.

Throoughput is the average rate of successful message delivery from over a communication channel.Also Throughput is directly proportional to data flows 1 & 2. Since there will less packet loss with increased buffer size, so data flow will be increased.This will increase throughput too.

Increase in buffer capacity will have very less impact on queuing delay as the buffer of Router R is not the sole cause of queuing delay.The window size of Hosts A and B also play an important role in Queuing Delay.

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