19. Calculate the delay × bandwidth product for the following links. Use one-way

Question

19. Calculate the delay × bandwidth product for the following links. Use one-way delay, measured from first bit sent to first bit received.

(a) 100-Mbps Ethernet with a delay of 10 µs.

(b) 100-Mbps Ethernet with a single store-and-forward switch like that of Exercise 16(b), packet size of 12,000 bits, and 10 µs per link propagation delay.

(c) 1.5-Mbps T1 link, with a transcontinental one-way delay of 50 ms.

(d) 1.5-Mbps T1 link between two groundstations communicating via a satellite in geosynchronous orbit, 35,900 km high. The only delay is speed-of-light propagation delay from Earth to the satellite and back.

Explanation / Answer

(a) 100-Mbps Ethernet with a delay of 10 µs.
Ans:

Here,
Delay * bandwidth
Given Delay = 10 µs ,
Given Bandwidth = 100-Mbps
=> 10 µs * 100-Mbps = 10 * 100 bps = 1000 bps

(b) 100-Mbps Ethernet with a single store-and-forward switch like that of Exercise 16(b),
packet size of 12,000 bits, and 10 µs per link propagation delay.

Ans:

Delay= propagation * transmit * queue
propagation = distance / speed of light
transmit = size/bandwidth
= 12000bits/100Mbps
= 120 * 10 ^-6 s
Delay * Bandwidth = 120 * 10^-6 * 100 Mbps
= 12 K bits

(c) 1.5-Mbps T1 link, with a transcontinental one-way delay of 50 ms.

Ans: 50 *(10^-3s)*1.5 Mbps
= 75 K bits

(d) 1.5-Mbps T1 link between two groundstations communicating via a satellite in geosynchronous orbit, 35,900 km high. The only delay is speed-of-light propagation delay from Earth to the satellite and back

Ans:

propagation = distance/ speed of light
= (35000 * 1000 m) /(3 * 10^8)m/s
=116 ms

Delay * bandwidth = 116ms *1.5Mbps
=174 K bits

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