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UNIVERSITY OF LONDON
GOLDSMITHS COLLEGE
B. Sc. Examination 2009 (Internal)
COMPUTER SCIENCE
INTERNET COMPUTING
IS53026A (CIS339)
Enterprise Networking
Duration: 2 hours 15 minutes
Date and time:
This paper is in two parts, Part A and Part B. There is one compulsory question in Part A.
There are a total of three questions in Part B. You should answer the question from Part A
and two questions from Part B.
Full marks will be awarded for complete answers to a total of three questions, one from Part
A and two from Part B. Each question carries 25 marks. The marks for each part of a question
are indicated at the end of the part in [.] brackets.
There are 75 marks available on this paper.
No calculators should be used.
THIS PAPER MUST NOT BE REMOVED FROM THE EXAMINATION ROOM
IS53026A (CIS339)
2009
1
TURN OVER
SECTION A
Answer the compulsory question from Section A.
Question 1
(a)
State, in your answer book, which of the following statements are true and which are
false and, if false, write out a corrected version of the statement:
i.
ii.
iii.
iv.
(b)
Connectionless protocols require a lot of state information to be held within the
network.
A network design must include hardware and software configurations of all network
equipment.
Network design will usually involve a trade-off between cost and other requirements.
One of the outputs of the design process is a geographically accurate map of the
network.
[3]
A charity has a requirement to connect its 8 charity shops up to a central computer
system at its head office. Data has to be collected from each shop at the close of the
day in a file, whose maximum size is 50 Kbytes. Suppose that cost is the main
consideration.
The design options you should consider are:
i.
An Internet solution using ADSL to an ISP at each shop and at the charity’s
head office.
ii. A solution using the PSTN and a modem at each shop and at the head office.
iii. An ISDN Solution using ISDN2 at each branch and ISDN16 at the head office.
iv.
A low speed private circuit solution using a star topology to connect each shop
to head office.
(c)
Give reasons why you would or would not recommend each design.
[4]
State which of the above design options best suits the requirements.
[1]
A new school is being planned and there is a requirement for a local area network to be
implemented with access from every classroom. There are to be 100 PCs in the
computer labs and another 50 dispersed in various rooms around the building, as well
as 20 laptops which teachers will expect to be able to use in any room. It is expected
that each PC will require no more than 50 kbit/s. Cost is to be the primary design
consideration.
You should consider the following design options:
i.
802.11b Wireless LAN.
ii. 10Base-T Ethernet using unshielded twisted pair wiring.
iii. 10Base-F Ethernet using fibre optic cable.
iv.
Fibre Distributed Data Interface.
Give reasons why you would or would not recommend each design.
IS53026A (CIS339)
2009
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TURN OVER
[4]
State which of the above design options best suits the requirements.
[1]
(d)
Identify the main differences between WANs and LANs.
[4]
(e)
Why was Variable Length Subnet Masking Introduced on the Internet?
[2]
Design a subnetwork addressing scheme for an IP network with the network address
193.26.106.0/24, supporting 2 LANs with up to 62 hosts, 3 LANs with up to 30 hosts
and up to 8 point-to-point WAN circuits. Your answer should be in the form of a table
with columns showing the subnetwork, the bits in the fourth byte of the address, the
subnetwork address (including the prefix), the first valid host address and the last valid
host address in each subnetwork.
[6]
IS53026A (CIS339)
2009
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TURN OVER
SECTION B
Answer two questions from Section B.
Question 2
(a)
State, in your answer book, which of the following statements are true and which are
false and, if false, write out a corrected version of the statement:
i.
ii.
iii.
iv.
Developing a new product in an existing market is called product development.
Insurgent operators nearly always employ a differentiation focus strategy.
ISPs have diversified into providing broadband access to the Internet.
A Bluetooth piconet can support up to 255 active devices.
[3]
(b)
Explain why incumbent operators have diversified into the solutions and outsourcing
businesses.
[5]
(c)
List four different schemes that a network manager can use to define which stations
belong to a VLAN and which addresses are used in each case.
[4]
(d)
Identify three positive and three negative aspects of monopolistic network operators.
[6]
(e)
Copy the following diagram into your answer book and use the Spanning Tree
Protocol to determine which bridge ports should be blocked. Show which bridge is
elected as the root bridge and show the path costs from each bridge port to the root
bridge. Mark all the root ports with an R, all the designated ports with a D, and all the
blocked ports with an X. Draw the spanning tree with thick lines.
[7]
IS53026A (CIS339)
100Base-T2
Cost = 19
Priority 2
Address 2
10Base-T
Cost = 100
Priority 1
Address 5
Priority 2
Address 4
Priority 2
Address 1
10Base-T
Cost = 100
Priority 1
Address 3
1000Base-T
Cost = 4
2009
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TURN OVER
(a)
i.
ii.
iii.
iv.
Question 3
State, in your answer book, which of the following statements are true and which are
false and, if false, write out a corrected version of the statement:
The station with the lowest MAC address on a Token Ring will become the active
monitor.
Traffic between different VLANs must be routed because it cannot be bridged.
Positions in geostationary orbit are allocated by the ITU-T.
The RTT on a VSAT network is twice as great as that for normal satellite
communications.
[3]
(b)
Identify four major weaknesses of the PSTN local loop.
[4]
(c)
Explain why an SMDS MAN or WAN is well-suited to connecting LANs. [4]
(d)
What are the main reasons that caused network operators to replace their
Plesiochronous Digital Hierarchy transmission networks with Synchronous Digital
Hierarchy transmission networks?
[6]
(e)
Draw the network diagram below in your answer book and use Dijkstra’s algorithm to
calculate the shortest route between F and all the other nodes, where the numbers
represent distances between the nodes. On your diagram, show the node labels
(including any temporary ones) you have used at each step of the algorithm.
A
5
4
H
B
12
8
3
11
13
10
C
G
2
6
F
9
1
D
7
[6]
E
Based on this information, devise a routing table for Node F showing the shortest
distance to each of the other nodes and the next node to be traversed for the optimum
route.
[2]
IS53026A (CIS339)
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TURN OVER
Question 4
(a)
State, in your answer book, which of the following statements are true and which are
false and, if false, write out a corrected version of the statement:
i.
ii.
iii.
iv.
ATM can carry or be carried by data link protocols such as HDLC, PPP and Ethernet.
MPEG 2 is used to compress video files for downloading via the Internet.
A trap is an SNMP function that can be used to catch unauthorised intruders on the
network.
It is often cheaper to over-provide network capacity than to get a network designer to
optimise it.
[3]
(b)
Describe the advantages and disadvantages of internetworking with layer 2 Ethernet
switches versus layer 1 Ethernet hubs.
[4]
(c)
Identify six common causes of network faults.
[6]
(d)
Contrast fault management and performance management.
[4]
(e)
If the availabilities of two components are A1 and A2. Write down expressions for the
overall system availability (A), when the components are connected in series and when
they are connected in parallel. With reference to probabilities, provide an explanation
of why the expressions should take these forms.
[4]
A satellite operator has two satellites in geostationary orbit, each with an availability of
99.9%. One is operational and one is on hot standby and it can be assumed that it can
take over without any interruption in service. A satellite circuit is configured via the
operational satellite between two earth stations. Each earth station has an availability
of 99.99%. Derive an expression for the overall availability of the satellite circuit
configured through both earth stations.
[4]
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END OF EXAM