Question 1

a) Define the term Concurrency and no global clock in Distributed Systems

b) Transparency is defined as the concealment from the user and the application programmer of the separation of components in a distributed system. Describe what "replication transparency" is.

c) What do you understand by "Ubiquitous computing"?

d) Explain how might the clocks in two computers that are linked by a local network be synchronised without reference to an external time course.

e) List the three main software components that may fail when a client process invokes a method in a server object, giving an example of a failure in each case.

Question 2

a) What factors affect the responsiveness of an application that accesses shared data managed by a server? Describe remedies that are available and discuss their usefulness.

b) Distinguish between caching and buffering.

c) The failure model defines the ways in which failure may occur in order to provide an understanding of the effects of failure. Give one type of failure with a brief description of the failure.

d) The Internet is far too large for any router to hold routing information for all destinations. How does the Internet routing scheme deal with this issue?

e) Explain how it is possible for a sequence of packets transmitted through a wide area network to arrive at their destination in an order that differs from that in which they were sent. Why can't this happen in a local network? Can it happen in an ATM network?

Question 3

a) Define what is quality of service in mobility?

b) Explain the purpose of the session and transport layer of the OSI protocol.

c) Explain what is IP spoofing? .

d) Describe two of the characteristics of Inter-process Communication.

e) Give a brief description of the following key words in the TCP stream communication.

i) Flow Control

ii) Message duplication and ordering

iii) Message destination

Question 4

a) Describe what is RPC (Remote Procedure Call).

b) Discuss the invocation semantics that can be achieved when the requestreply protocol is implemented over a TCP/IP connection, which guarantees that data is delivered in the order sent, without loss or duplication. Take into account all of the conditions causing a connection to be broken.

c) In RMI invocation semantics, Request-reply protocols can be implemented in different ways to provide different delivery guarantees. What are the three main choices?

d) Discuss each of the tasks of encapsulation, concurrent processing, protection and scheduling.