Question

1. Consider a client and a server connected through one router. Assume the router can start transmitting an incoming packet after receiving its first h bytes instead of the whole packet. Suppose that the link rates are R byte/s and that the client transmits one packet with a size of L bytes to the server. What is the end-to-end delay? Assume the propagation, processing, and queuing delays are negligible. Generalize the previous result to a scenario where the client and the server are interconnected by N routers.

Answer 1

The end-to-end delay increases linearly with the number of routers (N) and the value of h.

Packet transmission on the client-side:

- Time to send the first h bytes: h / R

- Time to send the remaining (L - h) bytes: (L - h) / R

Packet processing on the router:

- Time to receive the first h bytes: h / R

- Time to receive the remaining (L - h) bytes: (L - h) / R

- Time to start transmitting the first h bytes: negligible (assumed)

Packet transmission on the server-side:

- Time to receive the first h bytes: h / R

- Time to receive the remaining (L - h) bytes: (L - h) / R

Total end-to-end delay (T):

T = (Client transmission time) + (Router processing time) + (Server reception time)

T = [(h + L - h) / R] + [h / R] + [(h + L - h) / R]

T = 2L / R + h / R

End-to-end delay with N routers:

Client transmission: Same as the single-router case: h / R + (L - h) / R

Transmission through each router:

- Each router receives the packet and starts transmitting after h bytes.

- Each transmission time is (L - h) / R

Server reception: Same as the single-router case: h / R + (L - h) / R

Total end-to-end delay (T):

T = (Client transmission) + (N * Router transmission) + (Server reception)

T = (h + L - h) / R + N * (L - h) / R + (h + L - h) / R

T = 2L / R + Nh / R

Therefore, the end-to-end delay increases linearly with the number of routers (N) and the value of h.

Answer 2

As the total bytes are L, when h bytes out of L are sent from client to router the router immediately send these h bytes forward to next router. Thus simultaneously another set of h bytes reaches the router and therefore many actions are being performed in a simultaneous way.

Step-by-step explanation:

For finding end to end delay, calculations are done and briefed.

All the paper work along with explanation is attached for better understanding.