labs questions

Question 1

Performance is inversely related to delay. When you use the Internet, which of the following applications are more sensitive to delay?

a. Sending an e-mail
b. Copying a file
c. Surfing the Internet.

Answer 1

1. most sensitive to delay is surfing the internet. when we send a request, we want to receive a reply and expect immediate access
2. email stays in inbox
3. file does not get copied immediately, also dependent on size

Question 2

Compare the telephone network and the Internet.
What are the similarities?
What are the differences?

Answer 2

similarities:
1. made up of interconnections between small networks
2. public networks and can be used by anyone who is subscribed
differences:
1. telephone network designed for voice com, internet for data com
2. telephone network is circuit switched, internet is packet switched

Question 3

An alternative to LAN (Local Area Network) is simply a big timesharing system with terminals for all users.
Give 4 advantages of a client-server system using a LAN.

Answer 3

1. exchange of data is fast because of the network links that are directly connected
2. set up cost is low
3. less delay since data is backed up using a centralized server and can be easily fetched
4. if client does not work, the rest of the network is still unaffected

Question 4

The performance of a client server system is influenced by two network factors:
1. the bandwidth of the network (how many bits/sec it can transport)
2. and the latency (how many seconds it takes for the first bit to get from the client to the server).
Give an example of high bandwidth and high latency. Then give an example of low bandwidth and low latency.

Answer 4

1. high latency & high bandwidth:
   a satellite communicating with stations on earth will have high bandwidth, but because the distance is incredibly far from the station and the fact that satellites have a specific geographic coverage, the latency will also be high.
2. low latency & low bandwidth:
   Bluetooth connections have low latency because the connections done are at a short distance (there is also a maximal distance) and have low

low bandwidth because Bluetooth use low amount of power therefore can only transfer less/smaller packets of data.

Question 5

Besides bandwidth and latency, what other parameter is needed to give good characterization of the quality of service offered by network used for digitized voice traffic?

Answer 5

• uniform delivery time

- low variability

Question 6

Suppose the Internet is roughly doubling in size every 18 months. Assume the number of hosts in the Internet was 7 million in January 1996. What would have been the expected number of Internet hosts in the year 2008?

Answer 6

1996             2008 
7m hosts     x hosts
2008 – 1996 = 12 years
12 * 12 = 144 months
144 / 18 = 8^2 =256
256 * 7,000,000= 1.792 billion hosts in 2008