Cork Institute of Technology
Higher Certificate in Science in Computing in Information Technology Support –
Stage 1
(NFQ – Level 6)
Spring 2006
Computer Networks 1
(Time: 2 Hours)
Answer any 4 questions,
All questions carry equal marks.
Examiners:
Mr. J. Greenslade
Mr. J. Sherwin
Question 1:
a) What are the differences between LANs and WANs?
(6 marks)
b) Give a brief outline of the layers of the TCP/IP reference model.
(7 marks)
c) What are the differences between the TCP/IP model and the OSI reference model?
(3 marks)
d) List two IEEE standards that specify LAN technologies, and also give the names
by which those technologies are better known.
(4 marks)
e) A network user has just transferred a 500KB file from his machine to a remote
server and experienced a throughput of 2Kbps. How long did the transfer take?
(5 marks)
Question 2:
a) Describe the composition of the fibre-optic cable that is used for networking.
(6 marks)
b) The company in which you work is installing a new network. As network support
specialist, you have an opportunity to give input to the design process. The new
network must provide service to offices, some of which are in separate buildings
within the same campus, and to terminals on a factory floor. What type of cable
would you recommend for horizontal cabling in the offices and on the factory
floor, and for the vertical cabling between buildings? Give reasons for your
answers.
(8 marks)
c) List 3 similarities and three differences between bridges and switches. (6 marks)
d) What are the functions of a router?
(5 marks)
Question 3:
a) Give a brief account of MAC addresses.
(5 marks)
b) Describe the signaling scheme used on a Standard Ethernet network, and graph the
signal that will represent the following stream of bits: 100110.
(6 marks)
c) Which characteristics do the 10Mbps, 100Mbps and 1Gbps versions of Ethernet
have in common, and which are different?
(5 marks)
d) Why and how do switches use the Spanning Tree protocol?
(5 marks)
e) Outline the possible sources of delay that a signal experiences on its way across a
network from a transmitting source computer to its destination.
(4 marks)
Question 4:
a) Contrast IPv4 addresses with IPv6 addresses.
(4 marks)
b) Describe DHCP (Dynamic Host Configuration Protocol).
(4 marks)
c) Given the network address ‘193.12.34.0’, and assuming the network must be
divided into 20 subnets, answer these questions:
i)
What class of address is this?
ii)
How many bits must be borrowed?
iii)
What is the subnet mask for this network?
iv)
What is the broadcast address of the first useable subnet?
(13 marks)
d) What is the difference between an Interior Gateway Protocol and an Exterior
Gateway Protocol? Give an example of each.
(4 marks)
Page 2
Question 5:
a) Below is a transcript of an FTP session. Comment on the purpose of each
command issued by the user and the response from the server to each command.
C:\>ftp 157.190.182.202
Connected to 157.190.182.202.
220 mc-b222la-js3.cit.ie FTP server (Version 6.00LS) ready.
User (157.190.182.202:(none)): anonymous
331 Guest login ok, send your email address as password.
Password:
230 Guest login ok, access restrictions apply.
ftp> dir
200 PORT command successful.
150 Opening ASCII mode data connection for '/bin/ls'.
total 4
dr-xr-xr-x 2 0 operator 512 Sep 19 2001 bin
dr-xr-xr-x 2 0 operator 512 Sep 19 2001 etc
drwxrwxrwt 3 0 operator 512 Mar 26 09:36 incoming
drwxr-xr-x 2 0 operator 512 Mar 19 2003 pub
226 Transfer complete.
ftp: 210 bytes received in 0.01Seconds 21.00Kbytes/sec.
ftp> cd pub
250 CWD command successful.
ftp> dir
200 PORT command successful.
150 Opening ASCII mode data connection for '/bin/ls'.
total 14
-rw-r--r-- 1 0
operator
818 Oct 30 2001 routerAconf.txt
-rw-r--r-- 1 0
operator
824 Oct 30 2001 routerBconf.txt
-rw-r--r-- 1 0
operator
820 Oct 30 2001 routerCconf.txt
-rw-r--r-- 1 0
operator
712 Oct 30 2001 routerDconf.txt
-rw-r--r-- 1 0
operator
618 Oct 30 2001 routerEconf.txt
-rw-r--r-- 1 14 operator 8704 Mar 19 2003 test.ppt
226 Transfer complete.
ftp: 431 bytes received in 0.01Seconds 43.10Kbytes/sec.
ftp> type binary
200 Type set to I.
ftp> get test.ppt
200 PORT command successful.
150 Opening BINARY mode data connection for 'test.ppt' (8704 bytes).
226 Transfer complete.
ftp: 8704 bytes received in 0.00Seconds 8704000.00Kbytes/sec.
ftp> bye
221 Goodbye.
C:\>
(15 marks)
b) A user on a network has reported that she cannot connect to the Internet using her
computer. Outline the process by which you would search for the cause of the
problem (assuming the cause is network-related).
(10 marks)
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