Consider two hosts, A and B, directly connected by a link of 40,000 Km, propagat
ID: 3746476 • Letter: C
Question
Consider two hosts, A and B, directly connected by a link of 40,000 Km, propagation speed 2.5*108 m/s, and transmission rate R=5 Mbps. Assume zero queuing delay.
(a) (10 points) How long does it take to move a packet of length 1000 bytes from one A to B?
(b) (10 points) Generally, how long does it take to move a packet of length L over a link of distance d, propagation speed s, and transmission rate R bps?
(c) (10 points) Assume the transmission time of the packet is dtrans and the propagation delay dprop. Suppose that host A begins to transmit a packet at time t=0. At time t= dtrans where is the last bit of the packet?
(d) (5 points) Suppose dprop is greater than dtrans. At time t= dtrans, where is the first bit of the packet?
(e) (5 points) Suppose dprop is less than dtrans. At time t= dtrans, where is the first bit of the packet?
(f) (10 points) Calculate the bandwidth-delay product R* dprop.
(g) (10 points) Consider sending a file of 1,200,000 bits from host A to host B. Suppose the file is sent continuously as a large message. What is the maximum number of bits that will be in the link at any time? (Hint: the answer shall be the smaller value of bandwidth-delay product and packet size)
(h) (10 points) What is the width (in meters) of a bit in the link? (Hint: the width of a bit = length of link / bandwidth-delay product)
Explanation / Answer
Answer a. time=d/s=(40000*10^3)/(2.5*10^8)=160 msec
b. time=d/s
c. the last bit of the packet is just leaving the host A.
d. bit is in the link & yet not reached the other side that is host B.