Exercise 10 (28.-31.3.) (Tanenbaum pp. 424-502)

1. Answer shortly the following questions ("review type" problem: answers are usually found in lecture notes or in Tanenbaum's book).
a) Why is BGP protocol needed?
b) How does CIDR increase IP addresses?
c) How are optional functionalities handled in the IPv6 protocol? Why they are handled like this? By the way where is the IPv5 protocol?
d) What is a jumbogram?
e) What do UNI and NNI mean? How do they differ from each other?
f) What are CBR, VBR and ABR UBR?
g) How is routing done in ATM network? What are the benefits of this kind of routing?
h) How ATM network tries to cope with congestion
i) Why is transport layer so important and necessary?

2. Suppose hosts A and B have been assigned the same IP address on the same Ethernet, on which ARP is used. B starts up after A. What will happen to A's existing connections? Could RARP-protocol be useful in this situation? Or is it possble to do something else to avoid situations like this?

3. A computer Host 1 connected to a LAN1 in the area A1 of the autonomous system AS2 (e.g. as in Tanenbaum's figure 5-53) sends a message to a host Host2 in the area A2 of the same autonomous system AS2. Draw a picture showing both hosts and their areas. Describe how the message is routed. Especially explain, what information is needed , where the information is stored and how it is maintained. Do not use passive, but explain who does and what.

4. a) IPv6 uses 16-byte addresses. Is that enough? If a block of 1 million addresses is allocated every
nanosecond, how long will the addresses last?
b) When the IPv6 protocol is introduced, to what amount does the ARP protocol have to be changed?

5. Discuss problems of transport connection establishment and release: give a short description
about the most interesting aspects. What problems does it cause to use a two-way handshake rather
than a three-way handshake to set up connections? Is it enough, in all situations, to use the three-way
handshake and timers? Could connection establishment or release lead to a deadlock situation?

6. Alice sends Bob e-mail about going to lunch together. Bob answers and agrees to have lunch with Alice. Outside the weather is as terrible as usual and neither Bob nor Alice is willing to out, if she /he is not absolutely sure that also the other is coming. How do they continue to exchange messages?
Alice and Bob can agree on the lunch also by phone. Why is it easier? Or is it easier?
A variation: a bank application makes a money transfer from an account a in the bank M to an account b in the O. How can this be made to succeed? How does this differ from Alice and Bob going to have lunch? Or is there any difference at all?