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Revision 2011

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Introduction

OSI Reference Model (Revision) Ports and Sockets

TCP/IP Reference Model (Revision)

Protocol Data Units

Flow control Automatic Repeat Request (ARQ) Protocols

End-to-End Versus Hop-by-Hop

Sliding Window

A Transaction Implications for Network design

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Week 2

Data Link Layer

1. Logical Link Control

2. Medium Access Control Schemes

2.1. Traditional LANs (revision)

2.2. High-Speed LANs3. Collision Domains

Switched LANs

Spanning tree protocol Redundancy

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Week 3

Cabling standards

TIA/EIA-568-A

TIA/EIA-569

Network design

Repeaters, Hubs, Bridges, Switches and Routers

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Week 4

Transmission Media Signal types

Characteristics of Signals

Bandwidth and Fourier analysis

Transmission Impairments

Signal to Noise - measured in dB

Shannon's Theory - relates the capacity of a channel to

bandwidth, and signal to noise ratio Transmission medium

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Week 5 IP1.The Internet Layer2. Delivering the Data3. Subnetting4. Routing

4.1 Interior Gateway Protocols4.2 Exterior Routing Protocols4.3 Fragmentation

5. Addressing and Address ResolutionARPstatic vs dynamic

6. Reverse Address Resolution Protocol7. Encapsulation

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Week 6 Routing Protocols

Routing metrics

RIP

Timers

Updates Problems with RIP

slow convergence

instability

Triggered update - improves stability Split horizon

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Week 7

TCP1. TCP and IP operation

2. Transport Layer

2.1 TCP

2.2 Port Addresses

2.3 Connection Establishment

2.4 Data Transfer

2.5 Connection Release3 TCP Transmission Policy

4. Ports and Sockets

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Week 8

World Wide Web1. DNS

2. Web Clients and Server Applications3. HTTP Operation

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Week 9

Multimedia networking applications

Delays and jitter

Streaming multimedia

Audio and Video compression Real-Time Control Protocol (RTCP)

Principles for QOS Guarantees

Scheduling And Policing Mechanisms

Signaling in the Internet

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Week 10Introduction to Wireless Systems Electromagnetic Spectrum

Transmission Impairments

Antenna

Regulatory Bodies and Band Planning

Modulation

Topology

X

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Test / Exam 2 hours

Answer anytwo questions.

Read each question thoroughly before you start toanswer it

Be sure that you answer the question that is asked!

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Jan 2011

2 hoursAnswer Question 1 and two of the remaining three

questions.

Question 1 is worth 40 marks

The remaining questions are worth 30 marks each.

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Q1.A company needs to create 7 subnets using a Class C IP address. The

given IP address is 192.168.10.0

a. What is the subnet mask going to be for the new sub-networks?[2 marks]

b. What is the maximum number of hosts possible on each subnet?[2 marks]

c. Are any addresses wasted? If they are, why are they wasted? [2 marks]

d. Show the subnetwork address, broadcast address and the range of hostaddresses for the first 5 subnets use the grid below. You may use the firstsubnet (zero subnet) [14 marks]

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Subnet number Subnetwork address Host range (1st and last usable

address)

Broadcast address

1

2

3

4

5

Show all your workings in your answer, including the binary used to work

out your subnetting scheme. Use the template below.

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Q1 continued

e. A router uses a routing protocol to exchangeinformation with its neighbours. Explain how a routing

protocol that you know works. Include in your answer adiscussion about the timers and how updates arehandled.

[20 marks]

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Q2. Two hosts are separated by 20,000 kilometres and are

connected by a direct link of bandwidth 10 Mbps. A file of400 Kbytes is sent from A to B continuously as one bigpacket with one acknowledgement of 40 bytes using Stopand Wait ARQ.

Assume the propagation delay is 5 s per km.

i. Ignoring any overheads, calculate the total time taken totransmit the file and receive the acknowledgement.[10 marks]

Ans 0.520032 sec

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b. The network is changed and the same message is now

sent as four equal sized blocks. An acknowledgement of40 bytes must still be received before the next block canbe sent. Assume that the processing delays are negligible.

Calculate how long it would now take to transmit thesame file with the acknowledgements, using the Stop andWait method. [8 marks]

Ans 1.120128 sec

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c. Claude Shannon developed a mathematical expression

for digital data which relates the capacity of a channel tobandwidth, and signal to noise ratio.

If a channel has a bandwidth of 3 kHz, and a S/N of

30dB, what is the capacity of the channel?

S/N dB = 10log10 (S/N)

C = B log2(1+S/N)[12 marks]

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3. a. Quality of Service (QoS) means that a service can be

tailored to meet the needs of the type of traffic beingcarried. This is particularly useful when eithercompressed video or real time voice traffic is beingcarried.

i. Discuss the minimum requirements of real time trafficwhen it travels across a network. [6 marks]

ii. Describe the possible effects that can be experiencedwhen real time traffic encounters unpredictable delays.

[8 marks]

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b. A packet travelling across a network will pass through a

number of different routers along the route and it canexperience a number of different types of delays.Delays accumulate as the packet travels to itsdestination, to give the total delay experienced.

Discuss the different types of delays that packetsexperience on networks. Include in your answer andiscussion about the possible effects on these delaysthat can be caused by other factors such as packet size.

[16 marks]

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4. Web Servers are essential for e-commerce in this day

and age.

a. Discuss the two different techniques that are used to

deliver dynamic content to a user. [16 marks]

b. Users need to connect to a Web Server to retrieveinformation and to order and pay for goods. Describe

ALL the steps that occur to enable a remote user toconnect to a server and submit a query. [14 marks]

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c. Large files are usually split into small chunks to be sent

across a network.

i. Discuss the reasons for fragmenting a large data fileinto a number of smaller packets.

[4 marks]

ii. A packet can be variable length or fixed length. Statethe advantages and disadvantages that are found ineach case. [6 marks]

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Class Test 14th Jan 2010Ensure that you put your name and Banner ID on this paper.

Attempt ALL ten (10) questions on this paper. Write your answers for eachquestion in the space provided. You may use the reverse of the paper if youneed more space.

Return this paper at the end of the test.

Q1. Examine the running configuration files below,from two newly configured routers. There are a numberof errors in these configuration files, which arepreventing these routers from functioning correctly.Examine the configuration details for these two routersand identify all the errors present (there are more thanone). Circle the line number where there is an error,cross out the mistake and then correct the error.

(10 marks)

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Line # Running Configuration file for Router 1

{assume all the passwords have been set up Correctly}Running Configuration file for Router 2

1 enable enable

2 config t config t3 hostname Router-1 hostname Router-1

4 int fa0/0 int fa0/0

5 ip address 193.40.70.1 255.255.255.0 ip address 193.40.70.1 255.255.255.0

6 description Connected to Ethernet network 193.40.70.0 description Connected Ethernet network

193.40.80.0

7 no shutdown shutdown

8 int s0/0/1 int s0/0/0

9 ip address 193.40.60.2 255.255.255.0 ip address 193.40.60.1 255.255.255.0

10 description Connected to router Router-2 description Connected to router Router-1

11 no shutdown no shutdown

12 router rip router rip

13 network 193.40.60.0 network 193.50.60.0

14 network 193.40.70.0 network 193.40.30.0

15 exit exit

16 ip host Router-1 193.40.60.2 193.40.70.1 ip host Router-2 193.40.60.1 193.40.80.1

17 ip host Router-2 193.40.70.2 193.40.80.1 ip host Router-1 193.40.60.2 193.40.70.1

18 exit exit

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Q2. Switches use the Spanning-Tree Protocol (STP).

Explain the purpose of the STP

what it is used for andwhy it is needed. (Note - You do not need to describehow the protocol works.)

(10 marks)

Q3. Switches use two methods for passing frames

between input ports and output ports. These are cut-through and store-and-forward. Explain the differencebetween these two methods of switching.

(10 marks)

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Q4. A company needs to create 9 subnets using a

Class C IP address. The given IP address is192.168.10.0 (10 marks)

a) What is the subnet mask going to be for the new

networks?

a) Are any addresses wasted? If they are, why are theywasted?

a) What is the maximum number of hosts possible oneach subnet?

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d) Show the subnetwork address, broadcast address and

the range of host addresses for the first 4 subnetsuse the grid below. You may use the first subnet (zero

subnet)Show allyour workings in your answer, including the binary used to

work out your subnetting scheme.

The next page has been left blank for you to use for your workings.

Subnet

#

Subnetwork

address

Host range (1st

and last usable

address)

Broadcast

address

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Q5. A 500 km link operating at 100 Mbps connects a host (A)

to a remote server (B). The dialogue between the twomachines (A and B) consists of sequences of 128 byterequests from A to B and 4,096 byte responses from B to A.

The signal propagation delay over the link is 5 microsecondsper km.

i. Ignoring any protocol overheads, calculate the total time

required for one request-response cycle. (8 marks) Ans 0.00533792 s

ii. What is the throughput achieved? (2 marks)

Ans 958,121.1245 b/s

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Q6. Claude Shannon developed a mathematical

expression for digital data which relates the capacity ofa channel to bandwidth, and signal to noise ratio.

If a channel has a bandwidth of 3 kHz, and a S/N of 30dB,

what is the capacity of the channel?(10 marks)

S/N dB = 10log10 (S/N)

C = B log2(1+S/N)

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Q7. Users need to connect to the Web Server to retrieveinformation and to order and pay for goods. DescribeALLthe steps that occur to enable a remote user to connect to aserver and submit a query.

(10 marks)

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Q8.

a. Explain the difference between the Transmission Delayand the Propagation delay? [ 4 marks]

b. What effect does it have on the delays experienced by a

packet if the distance a packet travels increasessignificantly? [3 marks]

c) How is the overall delay affected if the transmissionspeed is increased but the distance stays the same?

[3 marks]

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Q9. Explain how the routing protocol RIP works. Includein your answer the role of the timers.

(10 marks)

Q10. Discuss the problems that slow convergence cancause in RIP networks. Include in your answer at leastone method of how this can be prevented.

(10 marks)

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Revise ALL tutorials

Practice with previous exam papers

Read the notes

Look at the labs