DOEACC Society 2006 DOEACC C Level C12 Distributed Systems ( ) - Question Paper

C12-R3: DISTRIBUTED SYSTEMS
NOTE:
Time: three Hours Total Marks: 100
1.
a) How can a remote object be implemented in a single-threaded server such that remote
invocations are atomic?
b) Distinguish ranging from active and passive replication.
c) Why is it sometimes so hard to hide the occurrence and recovery from failures in a
distributed system?
d) elaborate the properties of a transaction?
e) elaborate the basic requirements for mutual exclusion with respect to a resource?
f) What is a collaborative agent? provide an example.
g) How an ACLs implemented in a Unix file system?
(7x4)
2.
a) Consider the subsequent figure and obtain out any anomaly that can be rectified using a clock
synchronization algorithm. Name the algorithm that you will use to do the rectification
and show the various steps. Draw the rectified figure.
P0 P1 P2
0 0 0
2 five 10
4 m1 10 20
6 15 30
8 20 40
10 25 m2 50
12 30 60
14 35 70
16 40 m3 80
18 45 90
20 m4 50 100
22 55 110
b) Why and how are shadow blocks created?
(12+6)
3.
a) Why it may not be useful to let every scheduler in a distributed transaction system
independently implement strict two-phase locking?
b) discuss the two-phase commit protocol and mention what happens if the coordinator
crashes at a few point.
(9+9)
C12-R3 Page one of two July, 2006
1. ans ques. one and any 4 ques. from two to 7.
2. Parts of the identical ques. should be answered together and in the identical
sequence.
4.
a) What is the difference ranging from a name service and a directory service? Which 1 is
difficult to scale worldwide and why?
b) What info is needed to be stored in a system-wide object reference for
supporting remote method invocation?
c) How is X.500 directory implemented?
(8+5+5)
5.
a) How does communication ranging from a client and a server take place in NFS?
b) How can an organization enforce the use of a Web proxy gateway and prevent its users
to directly access external Web Servers?
(10+8)
6.
a) discuss how an RPC system or a remote message sends system such as Java RMI
might deal with
i) The loss of a reply to a remote call or method innovation.
ii) The crash of the server.
b) Explain, briefly the various services given by CORBA.
(9+9)
7.
a) How does AFS handle the user request of writing a file?
b) discuss briefly how the gossip architecture works.
c) Why thrashing is an important problem in Distributed Shared Memory (DSM) system and
what models are available for dealing with it?
(5+4+9)
C12-R3 Page two of two July, 2006

Earning:   Approval pending.