Computer Networking course - Network delay and throughput Consider the simple ne

Question

Computer Networking course - Network delay and throughput

Consider the simple network shown in the figure. The source and destination nodes are interconnected with N optical fiber links. The source host segments a long message into 3 smaller packets and sends the packets into the network. The links' transmission rates and lengths are(R_1, R_2, ..., R_N) and (d_1, d_2, ..., d_N), respectively. The figure's timing is drawn to scale. a. Explain which link has the highest transmission bit rate and which one has the lowest transmission bit rate. b. Explain which link has the longest propagation distance.

Explanation / Answer

Solution :

1)

Transmission delay : Tt = L/R : Where L is length of message and R is transmission rate of the connected link.

here there are N links with transmission rates R1, R2, ... RN.

In given scenario, there are three packets with length of message L1, L2 and L3.

Now, packet size remains constant for each link but transmission rate is different for each link.

Transmission delay is inversely proportional to transmission rate, i.e for larger transmission rate, transmission delay is less and smaller transmission rate has more transmission delay.

Hence in given network, the link with smallest transmission delay has highest transmission rate and link with highest transmission delay has smallest transmission rate.

2)

Propagation delay Tp = d/s : d = propagation distance and s = propagation speed.

Here, considering propagation speed of all the links constant, we get that propagation delay and distance are directly proportional with each other.

So we can say that, increase in propagation distance, propagation delay increases and decrease in propagation distance, propagation delay decreases.

Hence link with highest propagation delay has highest distance and link with lowest propagation delay has lowest distance.

If you have any doubts then you can ask in comment section.

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