QUESTION $1$

a$)$ Give an example of a distributed system. Explain why it is distributed and what advantage it has over a non$-$distributed implementation of the same system.

b$)$ Describe Access, Location and Migration transparency in a distributed system.

c$)$ What is an open distributed system and what benefits does openness provide?

d$)$ What is client$-$server computing? Which of these roles is an active role, and which is a passive one? Explain remote invocation in this context.

QUESTION $2$

a$)$ What are the advantages and disadvantages of HTML$,$ URLs and HTTP as core technologies for information browsing?

b$)$ Are any of these technologies suitable as a basis for client$-$server computing in general? $(2)$

c$)$ Explain the any THREE characteristics of a peer$-$to$-$peer service. Give TWO examples of peer$-$to$-$ peer middleware?

d$)$ Describe the role of middleware in distributed systems.

QUESTION $3$

a$)$ Explain two major types of services provided at the application "layer" in the TCP$/$IP model?

b$)$ List four application$-$layer protocols.

c$)$ Explain the role of the protocol layers in a network system?

d$)$ The two types of transport services that the Internet provides to its applications are TCP and UDP. Discuss the main characteristics that separate these services.

QUESTION $4$

a$)$ Cryptography is the science of keeping messages secure$.$ Explain, with an example, how it can be used in authentication to maintain confidentiality.

b$)$ Describe the main differences between public key and symmetric key cryptosystems. Explain the gdvantages and disadvantages of each.

c$)$ Briefly explain the following terms associated with network threats or security defense in a distributed computing system:

$($i$)$ Social engineering Attack

$($ii$)$ Denial of Service