Download CIS110 Assignment 3 2007-8

CIS110 Assignment 3 2007-8
Set by Dr. Rodger Kibble, Goldsmiths College, Monday March 17th 2008.To be
submitted electronically by 5pm, Monday April 21st 2008 (instructions to follow).
There are 100 marks available on this assignment. Alll answers should be expressed
in your own words. You should give details of any references you have consulted.
Any material from published sources (including the subject guide) should be clearly
identified as a quotation.
I. Multiple choice questions (15 marks):
NB: marks will be deducted for incorrect choices.
1. In the context of networked computing, a protocol is:
a. A program that transfers data over a network according to standard
conventions.
b. A set of common rules specifying the format of messages and how
they are processed.
c. A report from the World Wide Web Consortium laying down rules for
data communication.
d. A set of rules prohibiting obscene, defamatory or otherwise offensive
content in emails and webpages.
2. The process of breaking up messages into fixed-size segments which can
follow independent paths to the destination is called:
a. Packet scheduling
b. Message switching
c. Packet switching
d. .Store and forward
3. A connectionless protocol is one where:
a. Messages are transmitted to a destination address without first
establishing a connection with the destination.
b. A message is sent to all nodes on a network but only the intended
receiving system will process it.
c. There is no physical connection; messages are sent via a wireless link.
d. There is no persistent connection between source and destination
nodes; a new connection is opened and closed for each transaction.
4. What does a DNS name server do?
a. Provides web services for part of a computer network which is
identified by a particular domain name.
b. Verifies the syntax of a domain name
c. Translates computer names into IP addresses
d. Lists all the computers belonging to a particular named domain.
5. According to the TCP/IP model, which levels do the following functions
belong to out of Application, Transport and Internet:
a. Opening and closing connections
b. Logical addressing scheme which gives a unique address to every
computer connected to the Internet
c. Finding a route from the source to the destination computer
d. Slowing down or speeding up transmissions to avoid overloading the
destination computer or under-utilising the network connection
e. Displaying messages to the end user.
6. What would be the consequences if corrupt or poorly designed routing tables
caused a loop in a section of the Internet?
a. Packets will travel around the loop indefinitely, until the network is
reconfigured.
b. Packets keep a trace of the route so far in an extension of the header,
and will be discarded if they revisit the same router.
c. Routers keep a record of all packets that arrive within a specified
interval and will discard duplicates.
d. Packets will travel around the loop until the Time to Live counter in
the IP header reaches zero, then they will be discarded.
7. What is meant by a client in the context of networked computing?
a. Someone who pays a subscription to an ISP for an Internet connection.
b. An application that initiates a connection with another application on a
remote host.
c. Any program that uses application layer protocols.
d. An application that requests services from another program on the
network.
8. What is meant by a server in the context of networked computing?
a. A computer that provides services to other systems on the network,
such as access to files, databases or web pages.
b. An application program that offers services to other systems on the
network, such as access to files, databases or web pages.
c. A program that waits for other programs to initiate network
connections.
d. A company that provides Internet connections for a monthly fee.
9. What happens if a TCP segment does not arrive at the destination system
within a pre-set time limit?
a. The receiving system will send a request for the segment to be re-sent.
b. The application will time out and have to be re-started.
c. Transport level software at the sending system will automatically send
another copy of the segment.
d. The application program at the sending system will re-create the data
and a new segment will be constructed and transmitted.
10. What is meant by a worm in the context of nextworked computing?
a. A malicious program that can transmit itself through a network.
b. An acronym for Write-Once Random Memory
c. A malicious program that hides itself by overwriting portions of a
legitimate program.
d. A malicious program disguised as something desirable, for instance a
game or utility program.
II. IP Addressing (25 marks)
(a) Explain how the following addresses identify a particular network, host computer
and application, assuming the class-based addressing scheme.
(i)
(ii)
205.188.159.153:110
128.232.0.20:80
(b) Given the following pairs of IP addresses and subnet masks, identify the network,
subnet and host addresses in each case, assuming the classfull addressing scheme.
Justify your answers.
i.
ii.
Mask: 255.255.192.0
IP Address: 145.123.125.10
Mask: 255.255.0.0
IP Address: 13.23.45.7
III. Web authoring (25 marks)
(a) Consider the following examples of a web page and an external style sheet. For
each line of the poem, list the font family, style, weight, size and colour that will be
used when the page is displayed in a standard browser. Justify your answer.
<html>
<head>
<title>Tyger</title>
<link rel = "stylesheet" type = "text/css" href = "tyger.css" />
<style type = "text/css">
div {font-family:arial;color:red;margin:20px 50px;}
div.emph {font-style:italic;}
div.bold {font-weight:bold;font-size:20px;}
div.gothic {font-family:"Copperplate Gothic Bold";margin:50px 100px;}
div.blue {color:blue;}
</style>
</head>
<body>
<div class = "emph">Tyger, tyger burning bright</div>
<div class = "bold" style = "margin:10px 20px 0px;">In the forests of
the night</div>
<div class = "emph bold">What immortal hand or eye</div>
<div class = "gothic blue" style = "font-size:24px;">Dare frame thy
fearful symmetry?</div>
</body>
</html>
Web page
div {font-size:16px;font-family:Courier;}
div.blue {border-style:solid;background-color:midnightblue;}
Style sheet
(b) Explain the relationship between XML, HTML and XHTML. Why does the
World-Wide Web Consortium recommend the use of XHTML standards in place of
HTML?
(c) What is meant by strict, transitional and frameset variants of HTML and XHTML?
How can you indicate which of these you are using in a web document, and how can
you verify that your document conforms to the relevant standard?
IV. Security, legal and social issues (35 marks)
(a) Explain the following terms in the context of computer security. Locate an
example of each in the recommended reading for the course or on appropriate web
sites and give a brief description.
(i)
(ii)
(iii)
denial of service
buffer overflow
Trojan horse
(b) Suppose you are starting up a small mail-order company which uses a website to
collect personal details of your customers, such as name, address, credit card details
etc, which are then stored on a database. Describe in your own words what you
would have to do to make sure you are complying with the UK Data Protection Act
1998. You should support your answers with reference to the eight principles of data
protection (or "good information handling") which are incorporated in the 1998 Act
(c) Do you think it is justifiable for employers to monitor all their employees’ emails
and website accesses from machines on company premises? Consider arguments for
and against the proposition.
Your answers to (b) and (c) should be at most 500-800 words in length.