1,  List six access technologies. Classify each one as residential access, company access, or wide-area wireless access.
 
2, Is HFC transmission rate dedicated or shared among users? Are collisions possible in a downstream HFC channel? Why or why not.
 
3, What is the transmission rate of Ethernet LANs?
 
4,  Suppose there are exactly two packet switches 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 user 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.)
 
5,   (a) How long does it take for a packet of length 2,048 bytes to propagate over a link of distance 2,400 km, propagation speed 2.5x108 m/s, and transmission rate 2Mbps? 
(b) More generally, how long does it take a packet of length L to propagate over a link of distance d, propagating speed s, and transmission rate R bps? 
(c) Does this propagation delay depend on packet length? 
(d) Does this propagation delay depend on transmission rate?
 
6,  Suppose Host A wants to send a large file to Host B. The path from Host A to Host B has three links, of rate R1=512kbps, R2=1.5Mbps, and R3=1Mbps.

(a) Assume no other traffic in the network, what is the throughput for the file transfer?
(b) Suppose the file is 4 million bytes. Dividing the file size by the throughput, roughly how long will it take to transfer the file to Host B?
 
7, Suppose users share a 2Mbps link. Also suppose each user requires 1Mbps when transmitting, but each user transmits only 30% of the time. (See the discussion of statistical multiplexing in Section 1.3)

a,  When circuit switching is used, how many users can be supported?
 
b,  For the remainder of this problem, suppose packet switching is used. Why will there be essentially no queuing delay before the link if two or fewer users transmit at the same time? Why will there be a queuing delay if three users transmit at the same time?

c,  Find the probability that a giving user is transmitting.

d, Suppose now there are three users. Find the probability that at any given time, all three users are transmitting simultaneously. Find the fraction of time during which the queue grows.