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Networks

What is a network?What is a network?

A Network is a collection of

computers and devices connected

together, often wirelessly via

communication devices and

transmission media, allowing

computers to share resources.

Advantages of NetworkingAdvantages of Networking

1. Facilitating communications2. Sharing hardware3. Sharing data and information4. Sharing software5. Transferring funds

LAN’s, MAN’s, WAN’s & LAN’s, MAN’s, WAN’s & BAN’sBAN’s• Networks usually fall under the 3

categories:– Local Area Network (LAN)– Metropolitan Area Network (MAN)– Wide Area Network (WAN)

• Future developments in Networks– Body Area Networks (BAN); where

a series of wearable or implented body sensors can turn the human body into a router for wireless communication devices, allowing data to be transmitted from the body to technology in order to achieve a task.

– For example, saving a word processing document to a portable wrist device and than walking to a touch activated printer.

Local Area Network (LAN)Local Area Network (LAN)a LAN is a network that connects computers

and devices in a limited geographical area such as a home, school computer lab, office building or closely positioned group of buildings around university or college.

Node – each computer or device on a network, such as a desktop, printer/fax, large hard disks. Nodes are connected by via cables.

Wireless LAN (WLAN)Wireless LAN (WLAN)

Is a LAN that has no physical connection between nodes.

Each node such as a computer or other devices must have wireless capability, wireless network card, USB network adapter, Express Card module, PC Card or flash card. E.g. Wireless access point like a wireless modem for Internet access,

Metropolitan Area Network Metropolitan Area Network (MAN)(MAN) high speed network that connects

local area networks in a city or town and handles the communications activity across that region. Made up of one or more LAN’s, but covers a smaller geographic area compared to a MAN.

MAN network providers are telephone companies, cable TV operators and other organisations associated with MAN.

Wide Area Network (WAN)Wide Area Network (WAN)Covers a large geographic area

like a city, country, state, emirate or globally using communication channels that combine many types of media such as telephone lines, cables and radio waves.

The Internet is the largest WAN.

Network ArchitectureNetwork ArchitectureIs the layout of computers,

devices and various media in a network.

Can be categorised as:◦Client/server◦Peer-to-Peer

Client/Server NetworkClient/Server Networkuse to network 10 or more computersWhere one or more computers act as a server (master computer) or host computers

A Client is other computers or mobile devices on the network that rely on the server for their resources or instructions in order to use other devices like a printer. For example, a server might store a database of customers. The clients on the network access the customer database on the server.

Client/Server NetworkClient/Server Network

Advantages:

Centralized management, Strong Security, Expansion and Create redundant systems

Disadvantages:

Expensive, difficult to implement and Central Point of failure

Peer-to-Peer NetworkPeer-to-Peer Networkuse to network 10 or less

computersEach computer or Peer can work

as a server and as a client

Peer-to-Peer NetworkPeer-to-Peer Network

Advantages:

Lower Cost, Easy to setup and good for temporary network setup

Disadvantages:

Limited growth, No central location, Weak Security, To many passwords

Internet Peer-to-Peer Internet Peer-to-Peer NetworkNetwork

A network that allows users to access each other’s hard disk and exchange files directly over the Internet.

Sometimes referred to as a file sharing network

Examples are:◦Bit Torrent◦Gnutella◦Kazaa◦Lime Wire – used to swap music files via

Web

Business Benefits to P2PBusiness Benefits to P2P

Companies & employees exchange files

In e-commerce, it allows buyers & sellers to share information like database records

Network TopologiesNetwork TopologiesTopology – is the physical layout

of computers and devices in a communications network

3 network topologies are:◦Bus Network◦Ring Network◦Star Network

Bus NetworkBus NetworkThis network is made up of:

◦A bus◦Cables◦Personal computers◦Other devices like a printer, modem,

switch/hub

Bus NetworkBus Network◦Advantages of a bus network are that

computers can connect and disconnect without affecting the other machines.

◦Disadvantages of a bus network are bandwidth, if two machines are hogging the bus as they exchange some huge files, then the others have to wait.

◦problem becomes worse as the network grows. So a bus is good for small to medium sized networks.

Ring NetworkRing NetworkThis network is made up of:Cable connectionsServerClient computersOther devices like a printer, modem, switch/hub

Ring NetworkRing Network◦Advantages of a bus network are: that it

is simple to set up with no complicated addressing needed. So its useful for small office networks

◦Disadvantages of a bus network are: is that if one of the links is broken then computers on one side of the break can't communicate with those on the other side.

Star NetworkStar NetworkThis network is

made up of:Switch/hubServerClient computersCable connectionsOther devices like a

printer, modem, switch/hub

Star NetworkStar Network◦Advantages of a bus network are: that

each link to the server is independent of the others so the computers do not have to share bandwidth with each other (unlike a bus arrangement).

◦Disadvantages of a bus network are: that more cabling is needed that other network arrangements.

◦if the central server is broken, then the whole network is broken.

IntranetsIntranetsWhat is the difference between the Internet

and an Intranet?An Intranet is a private network within a

company and it is only available to staff or members of the organisation.

The Internet is a computer network that connects computers worldwide or public network

An Intranet example are applications containing information related to a company, for example, policies, procedures, rules, contact lists, social events, newsletters etc.

What is an extranet?What is an extranet?An Extranet is a computer network that

allows businesses outside the central company to access their network.

For example, the car company Ford has its own (huge) internal computer network that spans the world. However, it allows some of its main suppliers direct access to a small part of the network in order to allow them to share data with Engineers and Purchasing staff.

Network Communication Network Communication StandardsStandardsNetwork standards are

guidelines that specify the way computers access the medium to which they are attached, the types of medium used, the speeds used on different types of networks, and types of physical cable and/or the wireless technology used.

ProtocolsProtocolsA protocol is a set of rules for the

exchange of data between a terminal and a computer or between 2 computers.

For example transmission speed. If one machine is talking at 56,600bps and the other is listening at 28,800 bps, the message doesn’t get through.

Protocols include prearranged messages such as “are you ready?” ; “I am about to start sending a data file”

ProtocolsProtocolsProtocols for both wired and wireless networks

include:1. Ethernet2. Token ring3. TCP/IP4. Wi-Fi5. Bluetooth6. UWB7. IrDA8. RFID9. WiMAX10.WAP

Ethernet Ethernet A network standard that specifies no

central PC or device on the network (nodes) when data is transmitted

Is based on bus topology, but can be wired on a star pattern

Controls how devices (e.g. Modems, routers, ec) share access to media (e.g. Cables & lines) and how devices transmit data over communications channel.

EthernetEthernetExamples of

Ethernet are cables that plug into PC’s and other devices like printers for networks

Token RingToken RingA token is a series of bits

that function like a ticketOnly a device at a time with

a token can transmit data over the network

Token ring is based on ring topology

Physical configuration of a network includes cables, network cards and devices

Data transfer rate can either 4 Mbps, 16Mpbs, 100 Mbps or 1 Gbps

TCP/IPTCP/IPTransmission Control Protocol/Internet Protocol

(TCP/IP)TCP is responsible for checking that data has

been delivered correctly from your computer (the client) to another computer (the server). If data is lost, then TCP requests that the data is re-sent.

packets are small pieces of a message divided up for transmission

PC’s use TCP/IP for uploading web pages over the Internet. Web page is broken up into packets with its own address and reassembled once the web page arrives at your computer.

Routers send packets over the Internet from web server to your PC

How TCP/IP sends data as How TCP/IP sends data as PacketsPackets

Wi-FiWi-FiWireless fidelity or 802.11Uses radio technology within a LAN802.11 standards are 2 wireless devices

communicate over the air Wi-Fi works in conjunction with TCP/IP when

accessing the InternetWi-Fi network is popular with hot spots, where

users can connect to the Internet in shopping malls

Many homes & shops use Wi-Fi to network computers & devices wirelessly

In open areas Wi-Fi range is up to a range of 30 meters or more

University’s/colleges use Wi-Fi mesh network

How Wi-Fi technology How Wi-Fi technology worksworks

Bluetooth Bluetooth Bluetooth or 802.15Wireless technology

that enables Mobile phones, Handheld computers & PC’s to communicate with each other regardless of OS

Uses radio technology like Wi-Fi to transmit data only up to a range of 10 meters

Used for room-size personal area networks (PAN)

A Bluetooth devices contains a small chip that allows it communicate with other Bluetooth devices. If device is not Bluetooth enabled, than a Bluetooth wireless port adapter will convert existing USB port into a Bluetooth port

Ultra-WidebandUltra-WidebandA low power, short-range radio wave

technologyTransmits ultra-high-speed signals over a wide

spectrum of frequenciesAt 10 meters, data is transferred at 110 Mbps up to 2 meters, data is transferred at 480 MpbsBest suited for transmission of large files like

video, graphics & audioFor example files are transferred wirelessly

from a digital video camera to a media player or displaying a slide show on a projector.

IrDAIrDAIs infrared technologyHas a 1 meter rangeApproximate speed of 9600 bpsUsed for data exchange between

personal digital assistants (PDA’s)Requires a clear line of sight

between sending and receiving data.

Radio Frequency Radio Frequency IdentificationIdentification

Radio frequency identificationA reading tool that uses radio waves to

communicate with RFID tagsRFID tag or transponder broadcasts its unique ID

number to the reader, which digitizes the info for input into a computer

RFID tags or transponders can be cards, car sticker on a windscreen, grain of rice, bar codes on books, etc..

The tag consists of an antenna and memory chip that transmits information via radiowaves

How RFID Toll WorksHow RFID Toll Works

Student task: Read page 481, fig 9-21 and create a flow chart on how road tolls work using RFID standards. E.g. Refer to road tolls in Dubai. Email your work through to Mr. Greg

RFID versus Bar CodesRFID versus Bar Codes

Bar code reader – a tool that uses light to read universal product codes, inventory codes and other codes created out of patterns of variable-width bars. E.g. Used at check outs in supermarkets

Bar code readers are attached to point-of-sale (POS) terminals POS send scanned information to a computer, it determines

price, calculates taxes and totals and records transaction Reading text from books, magazines & other printed documents

is challenging RFID readers use radio waves to communicate with RFID tags RFID tags can be read from a greater distance Hard plastic antitheft cards attached to clothes at shops contain

RFID tags for security purposes RFID tags used to identify books, goods on pallets, etc RFID tags are designed to be read by computers quickly and

accurately

WiMAXWiMAXWorldwide interoperability for microwave

access or 802.16Is a network standard used for wireless

devicesA wireless alternative to cable or DSL servicesA powerful tool for connecting Wi-Fi networksProvides wireless broadband Internet access

at a good price over long distances to business and home users

Many mobile devices have built in WiMAX standards

WiMAX TowersWiMAX TowersWiMAX towers have a 48 km radius, connects to the Internet or to another WiMAX tower

WAPWAPWireless application protocolDetermines how mobile

devices like smart phones can display content of Internet services such as Web, email and chat rooms.

Uses a client/server networkMobile devices contain client

software that connects to the server of the ISP

Communications SoftwareCommunications SoftwareConsists of programs that:

1. Help users establish a connection to a another computer or network

2. Manage the transmission data, instructions and information

3. Provide an interface for users to communicate with one another

Examples of application software for communications are e-mail, FTP, web browser, chat rooms, instant messaging, video conferencing and VoIP

Communications over the Communications over the NetworkNetworkPublic switched telephone network (PSTN) is a worldwide telephone system that handles voice-oriented telephone calls

Data, instructions and information are transmitted over telephone network using dial up lines or dedicated lines.

Dial up LinesDial up LinesIs a temporary connection that uses one or

more analog telephone lines for communicatesCosts more to operate than a phone call

Dedicated LinesDedicated LinesIs a type of always on connection

that is established between two communications devices

Five types of dedicated lines are:1. ISDN lines2. DSL3. FTTP4. T-carrier lines5. ATM

ISDN LinesISDN LinesISDN stands for integrated services

digital networkUsed for small business and home

usersIs a standard for digital

transmission of data over standard copper telephone lines

Can carry 3 or more signals through a telephone line, by multiplexing the signal

DSLDSLDigital subscriber lineTransmits at fast speeds on copper telephone

wiresADSL is the most popular DSL typeADSL-asynchronous digital subscriber lineADSL supports faster transfer speeds when

receiving or downstreaming data and sending or upstreaming data

ADSL is ideal for Internet accessDo ADSL connections transmit data

downstream faster than upstreaming?

FTTPFTTPFiber to the premisesUses fiber optic cables to provide extremely high-speed Internet access2 types of FTTP are FTTH & FTTBFTTH for home usersFTTB for organisationsWith FTTP service, an optic terminal receives signals and transfers them to a router

connected to your computer.Will become more affordable when the cost of fiber optics decreases

T-Carrier LinesT-Carrier LinesAre long distance telephone lines that carry many

signals over single communication linesUses multiplexing, to provide very fast data transfer

ratesT1 line is the most popular with Internet access

providers, when providing services to homes and small businesses

T1 gets slower when more users are addedT3 is equal in speed to T1T3 lines are very expensiveT3 include large organisations, telecommunication

companiesWAN like the Internet use T3 lines

ATMATMAsynchronous transfer modeCarries voice, data, video and multimedia Transfer data at very high speedUsed for Internet,Gradually replacing T3 lines as the

standard for data transmission

Communications DevicesCommunications DevicesIs any type of hardware capable of

transmitting data, instructions, information between a sending device and a receiving device.

At the sending device a set of instructions are initiated to transmit data, instructions or information

At the receiving device the transmission of data, instructions or information is received from other devices.

Types of communication Types of communication devicesdevicesDial-up modemsDigital modems; ISDN, DSL &

CableWireless modemsNetwork cardsWireless access points (WAP)RoutersHubs

Dial-Up ModemsDial-Up ModemsConverts digital signals to analogue signals, so data

to travel along telephone linesDial-up means connecting to the Internet or the

World-Wide-Web by using an old-fashioned analogue modem

Dial-up connection is very slow at 56kbs compared to broadband 512kb and more.

Other devices than computers like fax-machine can convert scanned digitised image into an analog signal that is sent to a recipient’s fax machine.

Digital ModemsDigital ModemsDigital modem sends and receives data to and from a

digital lineBeing ISDN, DSL and Cable modems ISDN modem- sends digital data and information from

a computer to an SIDN line and receives digital data and from an IDSN line

DSL – Digital subscriber line Transmits at fast speeds on copper telephone

wiresoffer Internet broadband speeds and beyond. The more commonly used abbreviation is ADSL Cable modems – digital modem that sends and

receives digital data over the cable television network

Wireless ModemsWireless Modems It just helps network connect to the internet wirelessly, via

technology that uses Radio frequencies to transmit and receive data.

A popular wireless network technology is called "Wi-Fi". Wireless modems can be available with USB flash drive and

other PC cards etc.Easy to connect and portable and easy to useConnection can be interrupted and could be slow because of

range.

Network Network CardsCards

Communication device that enables a computer or device that does not have a built in networking capability to access to a network.

There are network cards that provide wireless data transmission which are called wireless network cards

Network card follows the guidelines of a particular network communications standard such as Ethernet or token ring.

Network cards are required in every machine connected to the network.

They allow the signal from the network to be transmitted to the machine – this could be via a fixed cable, infra red or radio waves.

NICs slot into the Motherboard

Wireless Access PointsWireless Access PointsA central communication deviceallows computers and devices to

transfer data wirelessly among themselves

Transfers data wirelessly to a wired network

WAP allows students to wirelessly work from classrooms, a library and other locations

To access a network, a laptop or mobile device must have a built-in wireless capability or a wireless network card

RoutersRoutersA router allows multiple connectionsMany are protected via firewalls of different strengthsSome routers include abilities to print via wireless connectivityCan use a DSL modem or a normal cable modemA router will accept incoming data packets arriving from a

connected L AN, router reads the destination address embedded in each data

packet and works out which of the other LANs is connected to the best one to use for that particular data packet.

Hubs and SwitchesHubs and Switchesnetwork hub is a hardware device that connects

multiple computers in a network. It allows networked computers to share data

packets.  A switch is a component which is used within a

computer network.A switch has a number of ports and it stores the

addresses of all network devices that are directly or indirectly connected to it on each port.

As a data packet comes into the switch, its destination address is examined and a direct connection is made between the sending and receiving machines

Home NetworksHome NetworksConnects computers and devices togetherHome networks have the following capabilities:

◦ Connect to the Internet ◦ Share a single high-speed Internet connection◦ Access files and programs on the other

computers in the home◦ Share peripherals such as a printer, scanner,

external hard drive, optical disc drive◦ Connect game consoles to the Internet◦ Subscribe to and use VoIP

Wired Home NetworksWired Home NetworksA home network can be wired or wireless or

both.Wired home networks are:

◦ Ethernet network◦ Powerline cable network◦ Phoneline network

Wireless Home NetworksWireless Home NetworksMost wireless home networks use a Wi-Fi

networks that sends data up to 1,500 ft.Computers accessing a Wi-Fi network use

built in wireless networking capabilities or wireless network cards

In wireless networks one PC will connect to a router/wireless access point

Walls, ceilings and electrical can run interference with wireless network signals

Communications ChannelCommunications Channel Is the transmission media on which data, instructions

or information travel in a communications systems.Bandwidth – being the amount of data, instructions,

information that can travel over a communications channel

Latency – the time it takes a signal to travel from location to the next in a network

Transmission media – are materials that can carry a signal e.g. Fiber optics, copper twisted wires, etc

Broadband - can carry multiple channels of data. Each channel can carry a different signal e.g. moving images, sound or text. With broadband more data can be carried at the same time.

Physical transmission Physical transmission MediaMedia

Physical transmission media used in communications include:◦ Twisted-pair cable◦ Coaxial cable◦ Fiber-optic cable

Wireless Transmission Wireless Transmission MediaMediaMore convenient than installing

cablesTypes of wireless transmission

media include:◦Infrared◦Broadcast radio◦Cellular radio◦Microwave radio◦Communications satellite

NETWORK REVIEWNETWORK REVIEWPage 503 of Discovering

Computers true/false questions1-11 multiple choice questions 1-8