1. Exercise (25. -29.1) (Tanenbaum pp. 1-28)
Exercise 1 is compulsary so that only those who have marked it done are regarded to be actively participating in exercises.

1. Answer shortly the following questions
a) What is the meaning of following acronyms: PSTN, ISDN, LAN, MAN, WAN, NMT, GSM?
b) What are internet and Internet?
c) What is meant by multicast and broadcast?
d) How is it possible that a message in a data communication network can
     -  totally disappear
      - multiply
      - pop up to a receiver much later than many of its followers (in principal even many days later)
e) What does "store-and-forward" mean?

2. An alternative  to a LAN is simply a big timesharing system with terminals for all users. Give the advantages of a client-server system using  a LAN. (Tanenbaum p. 74, problem 2. )

3. In connection management  following pairs of concepts  are used.
   - connectionless  - connection-oriented,
  -  confirmed - unconfirmed.
 Explain the meaning  of both pairs.  What is the principle difference between connectionless communication and connection oriented  service?  What is the difference between a confirmed service and  an unconfirmed service?Which combinations are possible in some situations? Give examples.
(Tanenbaum p. 74, problems 7 and 9.)

4. a) A communication link has the bit error rate (BER) of 0.0001 (on average one bit in 1000 will be transformed). The message size is 256 bytes. What is the message error rate (how many messages will be corrupted)? (Compute if you can how long it takes for one message to arrive intact).
b) Assume that BER is 10**(-9) and the message size is 256 bytes or 2 Kbytes. What is the message error rate for both message sizes.

5. A bicyclist carries with him 5 discetts each containing 1.6 Mbytes information For what range of distances does the cyclist carry information faster than a line of a) 9600 bps, b) 10 Mbps?

6. When transferring a file between two computers (at least two) acknowledgement  strategies are possible. In the first one, the file is chopped up into packets, which are individuelly acknowledged by  the receiver, but the file transfer as a whole is not  acknowledged. In the second one, the packets are not acknowledged individually, but the entire file is acknowledged when it arrives. Discuss these two approaches. (Tanenbaum p. 75, problem 23).