Exercise 1 ( 13. - 16.3.2007)

1. Bits, binary numbers and power prefixes

   1. If an identification field is 8, 16 or 32 bits long, how many different items can be identified using it?
   2. Show the desimal number 246 as a binary number and as a hexadecimal number.
   3. Show the binary number 101101101 as a decimal number and as a hexadecimal number.
   4. Do the addition of three binary numbers: 10010011, 10101010 ja 01110111.
   5. How large is a nanosecond, one terabit per second, one picometer and a petabyte?

2. Flow control and congestion control
   What is meant by flow control and congestion control? Why they are needed? How do they differ in the connection oriented Internet service? Do they have any meaning in the connectionless Internet service?

3. Reliable transport service in Internet
   What is meant by Internet's reliable transport service? What means does the connection oriented service use to provide reliable transport?

4. Different networks and their advantages and disadvantages
   What are the advantages and disadvantages of circuit switched networks when compared with packet switched networks? What are the advantages and disadvantages of virtual circuit networks when compared with datagram networks?

5. Transmission rate bps: Cyclist example
   1. A cyclist carries 5 diskets, each with 1.6 Mbytes information. The speed of the cyclist is 18 km/hour. To what distances does the cyclist transmit informaton faster than a line of i) 9600 bps, ii) 10 Mbps or iii) 1 Gbps?
   2. Suppose the cyclist carries 5 double sided DVDs, each with 8,5 Gbytes information. To what distances does the cyclist transmit informaton faster than a line of i) 9600 bps, ii) 10 Mbps or iii) 1 Gbps?
   3. Couldn't we just use brisk cyclists, each with a big bag of DVDs, to take care of large amount of data communication? What are the benefits and drawbacks of this kind of information transmission? To what kind of situations does it fit well, to what very badly?

6. The computer science department net
   You can find information about networks and their technologies in the web. Let's go searching!

   1. What is the physical structure of the Helsinki University network in principle? What different technologies are used in the network? Here it is enough just to give names or terms. It is not necessary to understand the technology.
   2. You send a message from a computer in Exactum to United States. Explain in principle (country/town) how the message travels.
      Hints: www.helsinki.fi/atk, www.funet.fi, www.nordu.net