Question

WILL RATE

2) Host A and B are directly connected with a 100 Mbps link. There is one TCP connection between the two hosts, and Host A is sending to Host B an enormous file over this connection. Host A can send its application data into its TCP socket at a rate as high as 120 Mbps but Host B can read out of its TCP receive buffer at a maximum rate of 60 Mbps.

a) Describe the effect of TCP flow control (assuming TCP is always sending at its maximum rate (i.e., ignoring slow-start and congestion avoidance), see if you can describe the precise times at which flow control takes effect). What is the ultimate average throughput of the file transfer?

b) What is the ultimate average throughput of the file transfer?

Answer 1

A) Describe the effect of TCP flow control (assuming TCP is always sending at its maximum rate (i.e., ignoring slow-start and congestion avoidance), see if you can describe the precise times at which flow control takes effect).

Ans :-

Since the link capacity is only 100 Mbps, so host A’s sending rate can be at most 100Mbps.Still, host A sends data into the receive buffer faster than Host B can remove data from thebuffer. The receive buffer fills up at a rate of roughly 40Mbps. When the buffer is full, HostB signals to Host A to stop sending data by setting RcvWindow = 0. Host A then stopssending until it receives a TCP segment with RcvWindow > 0. Host A will thus repeatedlystop and start sending as a function of the RcvWindow values it receives from Host B. On average, the long-term rate at which Host A sends data to Host B as part of this connection isno more than 60Mbps.

B)What is the ultimate average throughput of the file transfer? ?

Ans:-