Networking Hardware

Computer Science 2AB / 3AB

L.O. (SSS Carramar)

What is networking?• A network is called a

Communication Dyad

• Two components Source and Receiver

• A network is when two or more computers are joined together

• Means of Transport is can be via air, electromagnet radiation, or voltage

• Carriers allow the transmission of data i.e. air carries sound radio on an electromagnetic wave and wire for voltage

• They share resources

• Files and hardware

How are networks joined?• Cable

• Wireless (radio signals)

• Satellite

• Internet (remote access)

Which method of connection is best for me?

• Cable is your BEST choice

• Wireless Cable not practical used

between buildings

• Depends on your situation

What services does the server provide?

• Application access

• Centralised storage area

• Database

• Printer access

Proxy Server• The proxy server is used to

access Web pages by the other computers.

• When another computer requests a Web page, it is retrieved by the proxy server and then sent to the requesting computer.

• The net effect of this action is that the remote computer hosting the Web page never comes into direct contact with anything on your network.

• Proxy servers can also make your Internet access work more efficiently. If you access a page on a Web site, it is cached (stored) on the proxy server.

So what type of network is the World Wide Web?

• It is a Client/Server network

• The Web is a Wide Area Network (WAN)

I want to see myfavourite website. I will send arequest

I have received arequest . I will sendthe web page to theclient

Web Server

How is data transfer measured?

• The type of cable used will decide how big the transfer rate is.

• K= Kilo (Thousands)• M= Mega (millions)• G= Giga (Billions)• B-= bytes• Ps= per second

Data transfer is in bits per second

So 10 Mbps is what?10 Million bits transferred every second!

Internet Connection RatesDial up internet connection = 33kbps to 56 kbpsBroadband connection = 256 kbps to 8 Mbps

Types of Networks

• Cellular Networks• Personal Area Network (PAN)• Local Area Network (LAN)• Wide Area Network (WAN)• Structure of the Internet

Cellular Networks• Cell Phones use high frequency radio waves

(900 Mhz)• Antennas are placed in metropolitan areas• Areas divided into cells• Users move between cells and transmission is

automatically switched to the new cell to keep transmission

• Cell phones can now transmit all types of data i.e. E-mail, browse Internet

Personal Area Network (PAN)• PAN• Definition: PAN is an acronym for a personal area

network such as a home office or small business office wireless computer network. They are normally used when an person is connecting their mobile device to a desktop to transfer files.

• Examples: You would use a PAN to update your home office desktop with information from your laptop.

What is a local and wide area network?

LAN means: Local Area Network WAN means:

Wide Area Network

Characteristics of a WAN

WAN characteristicsCovers a much wider geographical area

LAN’s connected by satellite link or microwave link or telephone (POTS Plain Old Telephone System)

WAN is a mixture of locally/ publically owned leased or rented

High speed (1000Mbps)Three main connection types: Dial up, Dedicated and Switched Network connections

No limit of computers can connect to the network

The Internet is a WAN so a WAN can have global coverage

Linked by POTS, ISDN Optic fiber cable, Radio or Microwave

A WAN is made up of two or more LAN’s or a collection of networks

Every computer on a network has its own network address

Computers connected to the Internet have their own numerical IP address Internet will have many pathways that connect components

What is a dial up connection?• Public Switched Telephone Network (PSTN)

• A phone line connection– Carrier Twisted Pair Wire– Analogue transmission, the analogue wave varies with voltage this variation represents

the sound wave– Voice transmission at 300 to 3300 Hz

What is an IP address?Just as you live in a house with an address. So

does every computer (node) have its own address on the Internet.

This unique address is shown as a unique number to identify the computer or any other device

A computer with an IP address can now:receive data from the web serversend files, information, messages

Numbers start at 0.0.0.0 to 255.255.255.255. It gives over 4 billion combinations

Some numbers are used for Dynamic HostConfiguration Protocol

DHCP allows several computers use the same IPaddress like laptops

IP address is made up of four sets of decimal figures and range from 0 to 255

203. 109. 252. 72 is hawerahs.school.nz

Identifies the network

Indentifies the computer

IP addresses are given out by the Internet Corporation for Assigned Names and Numbers (ICAAN)

How does IP work ?

How does a computer user connect to a wide area network?

• We know that to connect computers you usually use a cable

• To connect computers over a wider area you need a ‘middle man’

• In the WAN world the ‘middle man’ is your Internet Service Provider (ISP)

• You ISP connects many networks so they can talk to each other

What is a firewall?• It is either software or hardware

• Its job is to protect the user against outside hazards i.e. viruses

• Your firewall will look at the data and only allow it through to a port in your computer if it meets certain rules

• It is placed between the user and the LAN or WAN network

NO FIREWALL YOU ARE GOING TO GET UNWELCOME VISITORS DOING BAD THINGS:Read dataAlter data No immediate detectionDelete dataStop communication between computers

What is a port?

A room will have one or two doors as entry points Your computer has thousands of entry points

The Firewall will:Monitor all entry pointsPrevent unwanted/ unauthorised data enteringBlocks unused ports

How do all these different computers and devices talk to each other over a network?What are the rules of a

market place?

How do all these different computers and devices talk to each other over a network?

• A universal language is essential in the computer world that’s why protocols are used

• Protocols are rules and procedures which tell the computers how to talk to each other

• That means that Window PCs, Apple and Linux computers can talk to each other without confusion.

• An Eskimo and China man meet, neither understand each other but the protocol of a handshake and smile is understood

How to avoid data collisions on an Ethernet network?

• So much data traffic on the cables causes collisions

• Just like us we need to look before we go on the road.

• The computer must look before it send data on the cable

• The Ethernet uses a sub protocol called Carrier Sense Multiple Access Collision Detection (CSMACD)

What is a node?

• Ethernet network can have upto 255 nodes

• Any piece of hardware connected to the network – Routers– Hubs– Computers– Printers– Scanners

What is a MAC address (Media Access Control) address?

• Real World every house has a unique address

• Every Network Interface Card (NIC) has a unique number in the whole world called a MAC address

What processes are involved in getting data from A to B?

A

BI want to get a file from computer ‘A’.

What processes are involved in getting data from A to B?

A B

Step1Computer B opens Microsoft’s network explorer application My Network places and found computer A icon. The icon is clicked and computer A talks to computer B

Step 2Computer A runs a security check to see what computer B is and is not allowed to do. Finding that computer B has the necessary rights it will allow it to browse its shared folders and files. That file is then dragged to the desktop of computer B

Step 3The application on computer A sends the file to the Network interface Card (NIC) for transfer to the network

Step 4Computer A’s NIC prepares the file to be sent by adding the MAC address of computer B NIC card and computer A’s NIC card. Special data is also added called Cyclic Redundancy Check or CRC. This allows the receiving computer B NIC card to check that the data has not been corrupted

Computer A’s NIC then creates a Frame and places data into it. If there is too much data to put into one frame it will chop the data up and put it in several frames

Step 5Computer A NIC checks to the line to see if it is clear to send the data. It will wait until it is the will send the data frame to the network Hub which copies it and sends it down each network cable

Step 6When the frame reaches each computer the recipients MAC address is read to see if it is meant for the NIC. If it is not meant for that computer the frame is not opened.

A bit like if an envelope comes to you with the wrong address on it. You will not open it but put it back in the post box!

When the frame reaches computer B and the MAC address is the same as computer B’s NIC the frame is opened and data sent to the appropriate application

MAC addressing limitationsProblem 1• Hubs replicate the data and frames so

100 computers makes 99 frames

• All computers to wait as data is sent

• Bigger the network slower it gets

Problem 2• Data moving from LAN to WAN moves across different transport media

– Telephone Lines– Optical cable– Satellite

• Different transport media has different signals so need different frames; some don’t support MAC addresses

What are the characteristics of TCP/IP?

• Two protocols designed– Transmission Control Protocol– Internet Protocol

• Designed to solve inter-network compatibility problems

What makes IP different from MAC addressing?

RECAP: • All NIC have a unique MAC address• MAC address lost when goes over different transport media as

NIC frame replaced with transport medias own frameYou want to e-mail a messageIP software puts message into data package (envelope)Envelope stamped with IP addressEnvelope given to NIC and put in MAC frame

TO: 132.254.87.1From: 192.175.53.5

Message Data Package Frame

TO: 132.254.87.1From: 192.175.53.5

Data reaches different transport mediaMAC frame taken away and replaced with transport media’s own frameData package and IP address stay intact, does not matter how many different frames it goes through

TO: 132.254.87.1From: 192.175.53.5

Data reaches the receiving networkFrame changed back to MAC frameData gets to receiving computerNIC takes data out of MAC frameNIC gives data package (envelope) to IP softwareIP software takes message out of data packageMessage goes to appropriate application

Networks in General

• First networks were (proprietary) only used by company which designed the network

• No need to connect to other networks as no data be exchanged between them

• Early network was AppleTalk for Apple Macs 1982

What is Ethernet?

• Used on LAN’s• Connections via cable

or wireless• Speed decreases with

number of computers

Early Ethernet or Bus Network

Today's Ethernet us a hub

Wireless Application Protocol (WAP)

• The Wireless Application Protocol (WAP) is the de-facto world standard for the presentation and delivery of wireless information and telephony services on mobile phones and other wireless terminals.

• The WAP Forum has published a global wireless protocol specification, based on existing Internet standards such as XML and IP, for all wireless networks.

• WAP is supported by the wireless telecommunication community so that the entire industry and most importantly, its subscribers, can benefit from a single, specification.

• WAP is designed to work with most wireless networks such as CDPD, CDMA, GSM,

What is topology?

This is the way data physically moves around the network

What are network topologies?Network topology is a description of thelogical configuration or shape of a network

Physical shaped determined by the buildings

When drawing the network lines would bestraight and of the same length

2 topologies: STAR & WIRELESS

What is a star network topology?• All computers connected to a

Hub or Switch or Patch Board

• Star works like a Bus network

• Uses Ethernet network hardware protocol

• Much greater reliability than a bus, cable breaks only affects one computer

• Most commonly used network

What is network hardware?

This involves all the hardware needed to getthe data from one computer to another

Type of hardware depends on

Type ofNetwork

NetworkTopology

Distance data has totravel from LAN to WAN

What is a data transport medium?

• Hardware which data travels along

• Cable• Infra red • Satellite

• WAN use telephone lines made from copper wiring

What is a modem?

• MODulation DEModulation

• Needed for computers to understand the data

• Converts digital to analogue and analogue to digital

What is a broadband connection?

• A fast Internet connection• Bandwidth

– Telecommunication connection– Has a wide band/ frequency– Describes speed of data

transmission– Wider the bandwidth faster the

connection • To increase bandwidth is to increase the amount of traffic a link

can handle i.e. bits per second. This could be done by changing the cable from coaxial to UTP or Optical

ADSL modems

• Asymmetric Digital Subscriber Line• To move data really quickly but much

cheaper than using an ISDN line– Downstream (ISP to you 8Mbps)– Upstream (You to ISP 1.5Mbps)

• Needs a good quality phone line within 1-2Km of exchange

• Connect to PC using an Ethernet Cat5 (UTP) network cable or USB

What are twisted pair cables?STP= Shielded Twisted Pair UTP=Unshielded Twisted Pair

Plastic Jacket

Metallic shieldingTwisted pairs of insulated wires

Twisted pairs of insulated wires

Plastic Jacket

Most common cable used today

Both cable made up of copper wire which are twisted

Twisted wire reduces interference

Cables are generally two or four pairsThe cable used will depend on what network it is for i.e. STP is used for Token Ring Networks

What is fibre optic cable?• Data signals transmitted as optical

light

• Data travels much further and faster

• Not affected by EMI

• Cable has reflective cladding to keep light moving along cable rod

• Protective cover made of Kevlar

Disadvantages– Costly– Fragile– Hard to install

Laser• Acronym for Light Amplified by

Simulated Emission of Radiation

• Light source used to transmit data along a fibre optic

• Light frequency is modulated to allow transmission of data

Network Requirements/ Operations

• Cabled Ethernet network needs NIC card• NOS operating system

– Arranging out going data in format to be transferred over the network using TCP/IP protocol

– Placing incoming data into the correct computer

• All computers to have a Media Access Address (MAC) address

What is an NIC (Network Interface Card)?

• A card that connects to the computer

• Turns digital to electronic data

• Receiving computer turns electronic to digital data

• Speed of network based on type of cable and network card

• All NICs have a unique MAC address

• Wireless NICs have a transmitter/ receiver

• Radiographic NICs send have an antenna and send and receive radio waves like a mobile phone

What is a switch?• A clever hub

• Learns MAC address of computers attached to it

• Gives message to one computer not all

• Advantage far less traffic so a faster more efficient network

What is a router?• Really clever switch• Connects WANs and networks with

different transport medium• Reads the IP address of all devices

connected to it• Looks at the IP address on the data

and sends it down the correct cable• Determines the quickest route• Router can re-route data to avoid

problems

• Can have one modem connection and be shared with other computers either cable or wireless

• Provide a firewall and security for wireless

Wireless Access Point• Wireless access points (APs or WAPs)

are specially configured nodes on wireless local area networks (WLANs). Access points act as a central transmitter and receiver of WLAN radio signals.

• Access points support Wi-Fi wireless communication standards.

Error Checking / Detection

Parity CheckEven parity (parity bit shaded) – parity bit is added so that the total number of “1”s is even.

Even parity (parity bit shaded)

1 0 0 1 1 1 0 1 1

Odd parity (parity bit cross shaded)

1 0 0 1 1 1 0 1 0

Odd parity (parity bit shaded) – parity bit is added so that the total number of “1”s is odd.

Checksum• Here a checksum (1 byte) is added to the end of the message.• Calculated by adding the decimal value of each character of the

message; dividing it by 255, and using the remainder as the checksum.

• The receiver calculates its own checksum and the two are compared.• If the same, it is assumed there are no errors.• Will detect up to 95% of errors.

H e l l o ! tot chksm

72 101 108 108 111 33 533 -255 23

Block sum check (Longitudinal redundancy Checking, LRC)

Frame oriented data transmission.• blocks of 8 bytes of data are transmitted. • Each character is assigned a parity bit.• Column data for the block of data is also assigned a parity value. • If anomalies appear in the parity values, the entire block is retransmitted.

This line is the block check characterOdd parity for each column. This is the (ODD)

parity bit for the parity column.

1 0 1 1 0 0 1 0 0

0 1 1 1 1 1 1 1 1

0 0 0 0 0 1 1 0 0

1 0 0 0 0 0 0 1 0

1 1 1 0 0 0 1 1 1

0 1 1 1 0 1 1 1 0

0 1 1 0 1 0 0 0 1

1 1 1 0 1 1 0 1 0

1 0 1 0 0 1 1 0 0

Even Parity per row

Produces an error detection rate above 98%.