Section C ch16 the networking and internet basics notes

1. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 1
Name:___________________________ Class:____ __( )
HKDSE Information and Communication Technology
Section C. Internet and its Application
Topic a. The Networking and Internet basics
(Book 2 Ch. 16 & 17)
Learning Outcomes Remarks
• Define and compare Local Area Network (LAN)
and Wide Area Network (WAN).
• Discuss the common services available in a Services include internal communications,
networked environment. conferencing and resources sharing.
• Explain the functions of the hardware required for This includes communication links (phone line,
a network. coaxial cable, fibre optics, microwave, satellite,
etc.), modem (including cable modem), network
interface card, network connecting devices (hub,
switch and router, etc.).
• Compare common methods for Internet access in This includes connections in wireless, leased line
terms of speed, cost, security and availability. and broadband etc.
• Understand the need for communications software
and communication protocols.
• Describe how data is transmitted over the Internet
and understand concepts of Internet Protocol (IP),
Uniform Resource Locator (URL), Domain Name
System (DNS) and Hypertext Transfer Protocol
(HTTP).

2. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 2
16.1 Computer Networks
The Logical Structure of the Internet: a Network of Networks
Computer network is a system of interconnected computers, peripherals and communication devices that can
exchange information and share resources. Networking is widely used in government departments,
corporations, educational institutions and homes. Internet - the world’s largest computer network connecting
billions of computers together around the world.

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16.2 Local Area networks (LANs) and Wide Area Networks (WANs)
Networks are categorized according to the area they cover.
Local area network (LAN)
A network that connects computers within a relatively limited area, such as an office, a building or a campus.
Wide area network (WAN)
A network that spans a wide geographical area, usually across cities, countries or even continents.
Comparison between LAN and WAN
LAN WAN
Data transfer LANs have a high data transfer rate WANs have a lower data transfer rate as
rates: compared to LANs
Connection: one LAN can be connected to other LANs LANs over any distance via telephone lines
over any distance via telephone lines and and radio waves Computers connected to a
radio waves wide-area network are often connected
through public networks, such as the
telephone system. They can also be
connected through leased lines or satellites
Set-up costs: If there is a need to set-up a couple of extra In this case since networks in remote areas
devices on the network, it is not very have to be connected hence the set-up costs
expensive to do that are higher
Definition: LAN (Local Area Network) is a computer WAN (Wide Area Network) is a computer
network covering a small geographic area, network that covers a broad area (e.g., any
like a home, office, schools, or group of network whose communications links cross
buildings. metropolitan, regional, or national
boundaries over a long distance
Maintenance Because it covers a relatively small Maintaining WAN is difficult because of its
costs: geographical area, LAN is easier to wider geographical coverage, and is its
maintain at relatively low costs. maintenance costs.
Technology: Tend to use certain connectivity WANs tend to use technology like ATM,
technologies, primarily Ethernet and Token Frame Relay and X.25 for connectivity over
Ring the longer distances
Example: Network in an organization can be a LAN Internet is the best example of a WAN
Geographical Have a small geographical range and do not Have a large geographical range generally
spread: need any leased telecommunication lines spreading across boundaries and need leased
telecommunication lines
Ownership: Typically owned, controlled, and managed WANs (like the Internet) are not owned by
by a single person or organization any one organization but rather exist under
collective or distributed ownership and
management over long distances

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Local Area Network (LAN)
- Consists of networked computers, or workstations, shared peripheral devices, communication devices and
links.
Two popular types of LANs:
1. Peer-to-peer (P2P) networks
2. Client/server networks
Peer-to-peer network
A network of workstations without a server
All the workstations can communicate directly with
each other.
Each computer can access the resources which are
shared by all the other peer workstations.
Usually have a small number of workstations.
Cost of setting up is relatively low.
Usually found in small companies and homes.
Client/server network
Client workstations are connected to a central server,
or a host computer.
Clients can access the resources stored on the server.
The set-up cost is relatively high.
It provides better security controls and network
services in a large-scale network environment.
Ideal for medium or large organizations.
Wide Area Network (WAN)
Refers to a communication network that spans a large geographical area, across regions or continents.
Consists of two or more remote LANs.
LANs are connected via different communication
channels
1. Telephone lines
2. Leased lines
3. Microwave
4. Satellites
5. Optical fibre cables
The Internet is the largest WAN in the world.

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Example:
Jimmy Lam constructs a peer-to-peer network to connect 20 computers of the staff members in the office.
(a) Give two advantages of setting up a peer-to-peer network over the client-server network.
1. No need to set up specific servers such as FTP server, printer server.
2. Each user has the right to control his/her resources sharing.
(b) A scanner is to be shared by these 20 computers. Describe, step by step, how to achieve printer sharing
among the computers.
1. Install the scanner on one of the computers and make the printer a sharable device
2. Install the sharable scanner driver on each of the other 9 computers
(c) Give one disadvantage of the scanner sharing method described in (b).
If the computer that physically connected to the printer is turned off, other computers in the network will not
be able to use the printer.
(d) A company allows its employees to work at home. In the office, computers are connected together to
form a local area network, Network A. The employees connect their computers to Network A through the
Public Telephone Network (PTN) to form Network B as follows:
(i) What is the hardware device X, which is installed at home?
modem
(ii) Besides the operating system, what is the necessary software for the home computer to connect to
Network A?
Communication software/ dialup software
(iii) Give two disadvantages of Network B over Network A regarding the performance of home connection.
1. Network B has lower data transfer rate.
2. Network B is less secure.

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16.3 Network Services
When a computer is connected to a network, it can provide more extensive services.
Major services provided by a network are:
Service Description Remark
Internal Communication between computes in a Examples: e-mail, instant messaging, file
communication LAN or a WAN transfer
Hardware LAN: sharing hard disks, printers and Better monitoring and utilization
sharing scanners Saving costs
WAN: hard disk storage space
Centralized data Centralizing data in a network server Keeping information updated
management Better security control
Increasing productivity and efficiency
Software Sharing network licensed software among Lower cost
sharing computers simultaneously Saving time for installation
Internet access Accessing the Internet via a computer Lower cost
network Better monitoring and network protection
Network Network communication via two-way Video signals must be compressed
conferencing audio and video signals Instant and cost saving
Information Backup information on individual For rapid system recovery
backup computers to a server via a network
Example: (b) Mr. Chung redesigns the LAN, as shown below
Mr. Chung builds a LAN in a school, as shown and thinks that it is now better. What is the
below. improvement?
Printer
Switch
Printer
Switch
(a) How does this LAN benefit the users of the
computers? Give two examples. 1. Computer A can still use the printer when
1. User of Computer A can use the printer Computer B is off.
2. The Users can share files. (share software/ 2. Occupies less resource of Computer B
communication) though Computer A is using the printer.

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16.4 Connecting to a Computer Network
Question: What hardware do you need in PC to connect to the router? Network Interface Card (NIC)
Network Interface Card (NIC) – is an expansion
board for connecting a computer to a network.
Each NIC has a unique media access control (MAC)
address for identifying the computer on the network.
Classification Example
Connector BNC and RJ-45
Expansion bus ISA, PCI, PCMCIA and USB
Bandwidth 10 Mbps, 100 Mbps and
1,000 Mbps
Network cables
Twisted-pair cable
Widely used in local area networks. Looks similar to a telephone cable and has an
RJ-45 on both ends. Winding two conductors together
→ eliminate electromagnetic interference
Shielded twisted-pair (STP) Unshield twisted-pair (UTP)
Has a metal wrapper around each wire to reduce Does not have metal shielding
noise and electromagnetic interference Low-cost substitution for the STP cable
Maximum data transmission speed of Cat 6 UTP
cable is about 1,000 Mbps within 100 m distance
limit.

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Coaxial cable Commonly used for VCR and cable television connections.
Has a BNC connector on both ends.
Higher ability to retain the strength of a transmitting signal over a long
distance than a twisted-pair cable
Consists of: a copper wire, a sheath of insulation, a wire mesh that
conducts and shields against interference, an outside coating,
Strengthened insulation allows coaxial cables to transmit more
information than twister-pair cables.
Optical fibre cable Advantages: Disadvantages:
Made of a bundle of glass Greater signal-carrying capacity Very high cost
threads that transmit light Faster data transmission Difficult to install
beams. Reduced susceptibility to interference Require a device for signal
Better security for transimission conversion
Thinner, ligher and more durable Once installed, it is difficult to
change

9. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 9
Example:
Which of the following will be assigned by a manufacturer when a network interface card is produced?
A. URL
B. IP address
C. MAC address
D. Memory address
Example:
Which of the following is least sensitive to external interference?
A. UTP cable
B. Optical fibre cable
C. Microwave
D. STP cable
Example:
(a) The company is going to subscribe a broadband Internet service. Mr Chung has investigated the
existing ISPs in Hong Kong and the results are as follows:
ISP A ISP B ISP C
Transmission media Optical fibre cables Telephone lines Coaxial cables
(i) State two advantages and two disadvantages of optical fibre cables over coaxial cables.
Advantages:
● The data transmission speed is higher.
● Optical fibre cables are less susceptible to electromagnetic interference.
Disadvantages:
● The cost is higher as special networking devices are required.
● It is much more difficult to set up networks using optical fibre cables.
(ii) Regarding ISP C, answer the following questions.
(I) State one common connector standard used by coaxial cables. BNC
(II) State another kind of signals that are delivered by coaxial cables in household networks.
TV signals
Example: Which of the following descriptions about network interface cards (NICs) is correct?
A. NICs nowadays use BNC connectors only.
B. The minimum bandwidth of an NIC is 1 Gbps.
C. Each NIC has a unique IP (Internet Protocol) address.
D. The NICs may use USBs as their expansion buses.
Example:
Arrange the following communication media in descending order of their data transmission rates.
(1) Coaxial cable
(2) Optical fibre
(3) Telephone line
A. (1) > (2) > (3)
B. (2) > (1) > (3)
C. (2) > (3) > (1)
D. (3) > (2) > (1)

10. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 10
Hardware components of networking
Network connecting devices
Device Function / Application
Hub Connection of computers and servers
Central connection point for a network of low data transmission speed.
The signals entering a hub are echoed to all other ports, a phenomenon called broadcasting.
Switch Connection of computers and servers
Central connection point for a network of a high data transmission speed, ranging from 10
Mbps to 1 Gbps.
Unlike hub, a switch does not echo signals to all other ports. It keeps a table of the MAC
address for each port.
Repeater Connection of remote devices
Amplifying received signals
Removing unwanted noises
Sending the amplified signals to the connected device
Bridge Interconnection of LANs
Interconnecting two or more LANs of the same type
Router Interconnection between different types of LANs / between a LAN and the Internet
Translating signals from different networks
Each router keeps a routing table internally and is able to determine the best path for signals
Gateway (not examined) interfaces with another network of different protocols
Modem Dial-up modem: Converting between digital signals Setting up a dial-up connection to a
and analogue telephone signals network
Cable modem: Converting between digital signals Broadband service via cable TV cables
and analogue cable TV signals
Digital subscriber line (DSL) modem: Filtering DSL Broadband service via telephone cables
signals , Converting DSL signals to signals that a
computer can process and vice versa.

11. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 11
Example:
The following diagram shows a network of four computers, A, B, C and D and two devices, X and Y. A is
sending data to C.
(a) Suppose X is a hub and Y is a switch
(i) Can the data also be obtained by B? Explain briefly.
(ii) Can the Data also be obtained by D? Explain briefly.
(b) Suppose X is a switch and Y is a hub
(i) Can the data also be obtained by B? Explain briefly.
(ii) Can the Data also be obtained by D? Explain briefly.
You are given the task of designing a simple LAN for a multimedia learning centre in your school on the
third floor. The centre has 40 standalone PCs. Each PC is currently running Microsoft Windows 7
operating system and some Microsoft Office applications. All others PCs in the school are sharing a 100
Mbps broadband Internet service except for this multimedia learning centre.
(a) Which type of cable should be used in the LAN? Explain briefly.
(b) In addition to the cables, what other two components are needed for the PCs to be connected together
in the LAN?
(c) Draw a diagram to illustrate your design

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Radio connections
Satellite broadband Microwave broadband
Can be used to establish a connection to the Internet in Communicates with the ISP by a microwave
remote areas where wired broadband is not available. signal.
Requires a dedicated satellite and a satellite dish on Broadband subscriber and the ISP send and
each end of the connection. receive radio signals directly to each other.
Average upload and download speeds are around Consists of a number of access points and
50Kbps and 500Kbps respectively. subscriber units.
Despite the low transmission speeds, the set-up cost and Access points mounted on top of buildings since
the monthly charge can be very expensive each subscriber unit must have a line-of-sight to
the access point
Practical coverage: up to 1.5 km
Data transmission speed: up to 100 Mbps
May be affected by rainstorms and connection
may become unstable or even breaks up.

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Example
Mr Lam is the IT manager of a university in London. There are two computer network separately located
in Building C and Building D which are used by students and staff respectively. The two buildings are 1
km apart, as shown in the figure below.
Connection across the building
(Distance: 1km)
Y X
.
. .
Internet X . Y .
.
Building D Building C
(Staff) (Students)
(a) (i) What network connecting devices are X and Y?
X: ___________________ Y: ___________________
(ii) Suggest a suitable type of network cable for the connection across the buildings and justify you
answer.
(iii) Instead of using a wired connection, Mr Lam wants to connect two networks by installing
microwave dishes on the roofs of the buildings. State two disadvantages of this approach.
(b) Mr Lam subscribes to an Internet connection which requires a cable modem to connect the campus
network to the Internet. What is the function of the cable modem?

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Wi-Fi connections [Wireless fidelity (Wi-Fi) ]
The network based on the IEEE 802.11 wireless local area network (WLAN) standard. Data is transmitted
by radio waves. Any two Wi-Fi-enabled devices can create a wireless connection to communicate with each
other.
To transmit data:
The sender translates digital data into radio signals and transmits it to the receiver
The receiver then translates the received radio signals back to digital data.
STANDARD 802.11a 802.11b 802.11g 802.11n
Data transmission Up to 54 Mbps Up to 11 Mbps 54 Mbps or above Up to 600 Mbps
speed
Maximum signal Indoor: 35m Indoor: 38m Indoor: 38m Indoor: 70m
coverage
Outdoor: 120m Outdoor: 140m Outdoor: 140m Outdoor: 250m
Radio frequency 5 GHz 2.4 GHz 2.4 GHz 2.4 GHz and/or 5
GHz
Cost High Lowest Low Very high
Popularity Unpopular Very popular Very popular -
Without the limitations of cables, it can be connected to a wired LAN by means of an access point.
Access Point - A device that allows a wireless device to communicate to other wireless devices by radio
frequencies
(Or communicates to a wired network by converting digital signals to radio frequencies and vice versa.)
Advantages: Disadvantages:
Cost of building up a network is lower. Effective data transfer rate is highly affected by the
Network structure can be modified if surrounding environment.
required. The risk of intrusions is higher.
A network can be extended to an outdoor The maximum data transmission speed of a WLAN is
area. significantly lower than that of a wired network.
The coverage of a wireless router or access point is limited.
The cost of building up a large wireless network can be very
high
Wireless (IEEE
Twisted-pair cable Coaxial cable Optical fibre cable
802.11 standard)
Data Maximum rate
100 Mbps to several
transmission 10 Mbps, 100 Mbps Up to 299 Mbps ranges from 11
Gbps
speed Mbps to 600 Mbps
Transmission
Electrical Electrical Optical Radio waves
signal
Varied, dependent on
Cost Cheap Expensive Most expensive
network size

15. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 15
Example:
The manager of a shopping centre plans to provide a free Internet connection service for customers.
(a) The manager decides that UTP sockets will not be provided to access the Internet. Give two possible
reasons to support the manager’s decision.
(b) The manager sets up a wireless network in the shopping centre. The wireless access points are installed
as shown below. Assume that the floors and the walls do not affect the signal transmission and the radius
of signal coverage of each of the wireless access points is 35 meters.
(i) Suggest a location where the customer may not be able to receive the wireless signal. Explain your
answer.
(ii) If a customer walks from access point A to access point B, what will happen to his connection? Explain
your answer
(iii) The manager plans to add one more wireless access point to improve the situation in (b)(i). Suggest
the best location for the new device. Explain your answer.
(c) What will happen if too many customers try to use the wireless network at the same time? Explain your
answer.
Example:
When buying a wireless broadband router for a network at home, which of the following considerations is
not necessary?
A. The data transfer rate of the broadband connection
B. Security protocols
C. The IP address of the router
D. Coverage of the router

16. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 16
16.5 Methods of Internet Access
Internet service provider (ISP)
An ISP is a company that provides Internet access services. It usually offers subscribers a communication
software package for establishing a connection with the ISP server. Includes a username, a password and
other necessary information. Data transmission speed or bandwidths vary from 56 Kbps to 1,000 Mbps.
Dial-up connection
Basic equipment:
1. Dial-up modem
2. A telephone line
Integrated Services Digital Network (ISDN)
ISDN works on the same principle as a dial-up connection.
Need an ISDN modem connected to a conventional telephone line to establish an ISDN connection to the
ISP server.
Broadband connections
A much higher data transmission speed than the standard 56 Kbps modem
Constant availability without dialing required
Simultaneous use of data and voice connections
Equipments required:
Digital modem: can send and receive digital data from the ISP through a dedicated transmission cable.
Network interface card
Main broadband systems for home users:
ADSL SDSL Cable modem
It uses standard telephone lines to It has identical upstream and It connects a computer to a cable
connect with an ADSL modem. downstream data transmission TV network.
The system is ‘asymmetric’ speed.
It has a designated capacity of 30
because the download speed (from The maximum data transmission
Mbps, but this has to be shared
1.5 to 9 Mbps) is higher than the speed is 24 Mbps.
among users at the same location.
upload speed (from 16 to 640 They use the whole bandwidth of
The data transmission speed is
Kbps). the communication cable for the
normally much lower.
Example: Netvigator broadband service and therefore
Example: i-Cable
the cable cannot be used for the
transmission of vocal signals.
T-carrier Mainly used by large companies and schools those need a continuous Internet connection.
Provides a permanent connection between the network server and the ISP’s server.
Allows network users to access the Internet simultaneously.
Various types of carriers support different data transmission speeds:
Maximum data transmission speed of T-1: 1.54 Mbps
Maximum data transmission speed of T-3: 44 Mbps

17. CFSS HKDSE ICT – [Section C] Topic a. The Networking and Internet Basic (Ch. 16 & 17) Page: 17
Wireless Internet access - can access the Internet or connect to a computer network instantly almost
anywhere with our notebook computer or other mobile devices.
Popular wireless connection methods:
Wi-Fi hot spots, Wireless Application Protocol (WAP), General Packet Radio Services (GPRS)
Comparison of Internet access methods
Dial-up Broadband Wi-Fi hot
ISDN WAP GPRS
connection connection spot
Data Maximum Maximum 1.5 Mbps – 11 Mbps– 10 Kbps – Maximum
transmission 56 Kbps 128 Kbps 1,000 Mbps 600 Mbps 153 Kbps 115.2 Kbps
speed
Cost Low Average High Very high Very high Very high
ADSL: Area
covered by
the telephone Area covered
Area covered Area covered Area Area covered
network by the
by the by the Covered by by the mobile
Availability mobile
telephone telephone Cable: Area Wi-Fi access phone
phone
network network covered by points network
network
the cable TV
network
Security High Very high High Low Average Average
Internet
Schools Households Internet access by:
Remote
Companies Schools Travellers access by: Smart phone
Application households
Large Large PDA users Smart phone PDA
Travellers
organizations organizations PDA Notebook
computer
Popularity Minority Minority Majority Moderate Minority Minority
16.6 Methods of Internet Access
Latest development for data communications
A new wireless transmission protocol has been developed, it can transmit data at 2.5 Gbps. The fastest Wi-Fi
connection is available in the market today. However, the security concerns about wireless transmission is
still an unsolved problem .No encryption method is proved to make a wireless network as safe as a wired
network. It may take ten more years to complete the migration of all existing 10/100 Mbit computer
networks to Gigabit networks.

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Example:
A tourist plans to live in a hotel that provides three different Internet connection options in the rooms as
well as in the business centre. The three different options are as follows:
Modem Upstream Downstream IP
A ADSL 640 kbps 9 Mbps Static IP address
B SDSL 30 Mbps 30 Mbps Static IP address
C Cable TV 300 kbps 1.5 Mbps dynamic IP address
D Dial-up 33 kbps 56 kbps dynamic IP address
(a) Are the four options all using broadband connection services? Explain briefly.
(b) Describe the meaning of the bandwidth of an Internet connection. How is it measured?
(c) What does upstream rate indicate? Why is the upstream rate less than the downstream rate in A, C, D
connections?
(d) Connecting the modems to outside, the hotel has chosen wire X for option A and another type of wire
Z for option C. Name X and Z.
(e) Which type of connection option do you expect to be used in the business centre of the hotel? Explain
briefly.
(f) For Internet connection using ADSL modem, suggest one added-value service that might also be
provided.
(g) In what circumstances would you use dial-up modem in Z for Internet connection?
(h) Describe one advantage of using a dynamic IP address instead of a static IP address.

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Example:
A network is set up in ABC School. All computers are connected together by an Ethernet 100BaseTX
network. Category 5 unshielded twisted pairs (UTP) cables are used in the network as transmission media.
For an Ethernet 100BaseTX network, each UTP cable segment should not be longer than 100 metres.
(a) As shown in the figure below, why are the wires in UTP cables twisted?
(b) If optical fibres are used instead of UTP cables, should the optical fibres be twisted like the wires in the
UTP cables? Explain your answer.
(c) The Principal of ABC School plans to connect his computer to the network 150 metres away. State the
number of UTP cable segments and an additional network device required. Explain your answer and
describe briefly how these are connected.
(d) The teachers in ABC School always use video conferencing to share lessons with other schools over
the Internet. Which of the following types of Internet connection services should be used: modem dial-up,
leased line or broadband? Give two reasons to support your answer.
Example
(a) There is currently a trend of using wireless networks rather than using wired networks. State two
advantages of using wireless networks.
(b) State two disadvantages of current wireless networks