1. Suppose there are exactly two packet switches (switch#1 and switch#2) between
ID: 3585018 • Letter: 1
Question
1. Suppose there are exactly two packet switches (switch#1 and switch#2) between a sending host and a receiving host. The transmission rate between the sending host and switch#1 is R1. The transmissions rate between switch#1 and switch#2 and between switch#2 and the receiving host are R2 and R3, respectively. Assuming that the switches use store-and-forward packet switching, what is the total end-to-end delay to send a packet of length L? (Ignore queuing, propagation delay, and processing delay.)
2.a) How long does it take for a packet of length 1,000 bytes to be delivered from the sending host to the receiving host over a link of distance 1,200 km, propagation speed 2.4x108 m/s, and transmission rate 10Mbps (consider both transmission delay and propagation delay)? b) More generally, how long does it take a packet of length L to be delivered from the sending host to the receiving host over a link of distance d, propagating speed s, and transmission rate R bps? c) How long does it take for the first bit of the packet to arrive at the receiving host (start to count the time when the sending host starts to transmit the packet)? d) How long does it take for the last bit of the packet to be put on the link (start to count the time when the sending host starts to transmit the packet)?
Explanation / Answer
1.
The delay from Sending host to switch#1 is L/R1
The delay from switch#1 to switch#2 is L/R2
The delay from switch#2 to Receiving host is L/R3
The total end to end delay is L/R1+L/R2+/L/R3
= L(R2R3 + R1R3 + R1R2)/R1R2R3
2 .a) How long does it take for a packet of length 1,000 bytes to be delivered from the sending host to the receiving host over a link of distance 1,200 km, propagation speed 2.4x108 m/s, and transmission rate 10Mbps (consider both transmission delay and propagation delay)?
Given,
L= 1000bytes
d = 1200km
s = 2.4*10^8
R= 10Mbps
So,
Tp = 1200/2.4*10^8 = 5msec,
Ttr = 1000*8/10*10^6 = 0.8msec,
So the total time = Tp + Ttr = 5.8msec
b) More generally, how long does it take a packet of length L to be delivered from the sending host to the receiving host over a link of distance d, propagating speed s, and transmission rate R bps?
Total Time(T)= (L/R+ d/s) seconds
c) How long does it take for the first bit of the packet to arrive at the receiving host (start to count the time when the sending host starts to transmit the packet)?
Answer: 5.0000001
(d) How long does it take for the last bit of the packet to be put on the link (start to count the time when the sending host starts to transmit the packet)?
Answer: 0.8m sec
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