Review

Compare a LAN and WAN

Answer• Geography– LAN Local – WAN remote

• Communication– Internal LAN – External WAN

• Connectivity– LAN Owned by business – WAN 3rd Party

• Configuration– Virtual network can go over both LAN and WAN

Describe bandwidth

Answer• Measures hw much data can travel

along a communication channel• More frequencies more data• Reported as BPS• Higher bandwidth means more data

can travel

Describe a switch

Answer• switch (1) a concentrator for

the network (1) allows cables to be plugged into it to redirect traffic (1)

Describe a NIC

Answer• network Interface Card (NIC)

(1) gives computer unique MAC address (1) • allows physical connection via

cable to network (1)

Describe a WAP

Answer• Dedicated frequencies/channels that can

be connected to.• Hardwired into network supporting• Radio signals received by WAP• Broadcasts the data packed intended for

wireless devices• Security for wireless connections

List as many ways you can connect

to the internet as possible

Broadband

What providers do

you have?

What affects broadband

speeds?

Answer• Number of users• Number of frequencies

available• Distance from exchange

Develop a weebly site guide to....

• ADSL• Cable• Wireless• Leased Line• Satellite• Review Areas

– availability – connection type – bandwidth – multimedia – symmetry

• Email your weblink to me to check

This type of connection sends data down existing copper wires at different frequencies.

Most of the data transmitted is downloaded so more frequencies are provided for the downstream than the upstream.

This graph shows the frequencies used totransmit data.PSTN: Public Switched Telephone Network

(The frequency you use to talk to others!)

ADSL (Asymmetric Digital Subscriber Line)

As you can see from this speed test…

The download speed is far greater than the upload speed.

ADSL connections are asymmetric because they have different upload and download speeds.

Companies who host websitesusually request to have ahigher upload speed so webpages can be downloadedfaster.

ADSL (Asymmetric Digital Subscriber Line)

ADSL connections provide the ‘always on’ service.

When people used dial up modems to connect to the internet they had to make sure no one was using the telephone.

If someone tried to ring they would get an engaged sound!

If someone picked up the telephone whilst you were connected to the internet your connection could drop.

ADSL connections do not suffer from the same problems.

ADSL (Asymmetric Digital Subscriber Line)

The bandwidth of ADSL connections can be affected by:

◦ The distance your house is from the telephone exchange.

◦ Local AM frequencies can cause some interference…thus reducing the number of usable frequencies thus reducing the bandwidth.

◦ Other devices connected to the same telephone cable (e.g. fax machines).

◦ Electrical interference on the copper wire.

◦ The number of sockets in your house can also have an affect on your bandwidth.

ADSL (Asymmetric Digital Subscriber Line)

• ADSL is mainly used in households.

• Large companies tend to need higher upload speeds.

• ADSL also has the disadvantage being that the bandwidth is shared.– This means that during busy periods bandwidth

actually reduces.

ADSL (Asymmetric Digital Subscriber Line)

Broadband connections can be provided by television companies.

The data is transmitted via fibre-optic cables resulting in higher bandwidth being achieved.

Because of the nature of the service, the upstream/downstream ratios tend to be equal.

In reality, as the cables are often shared, the ratio may change due to increased traffic on the cable.

Cable

CableSwitch in the street

ISP

The introduction of 3G technology has made wireless broadband far more popular.

Wireless speeds, as of 2009, were between 7.2 Mbps and 14.4 Mbps.

Although the bandwidth is good, it does require a good 3G signal.

Connecting to a 3G network requires the user to connect their device to a mobile using Bluetooth, a USB cable or a USB modem stick.

Wireless

Wireless

A leased line connects two locations together.

Contention ratios are non-existent as the line directly connections two routers.

Because this is a fixed line it requires specialists to set up the connection.

This method is obviously more expensive but for large companies this is the preferred method.

As the line is direct between two routers it is harder for those wanting to intercept transmissions as they do not have access to that line.

Leased Line

Many schools make use of leased lines which connect schools to the local authority.

At present, many schools use fibre-optic cables which allow bandwidth speeds of up to 10 Mbps.

This obviously causes some bottlenecks to occur, especially when lots of data is being downloaded at the same time.

For this reason many local authorities are planning on upgrading to 100 Mbps connections.

It is important to note that this does not prevent bottlenecks...it merely eases the problem.

Leased Line

• This is mainly used were physical and wireless connections are not possible.– These tend to be in remote locations such as

the countryside or in the desert!!

• There are two types of broadband available:– One-way– Two-way

Satellite

• This method uses a satellite to download data but uses a modem and the telephone line to upload information.

One-Way Satellite Broadband

Satellite Dish(one-way)

Computer

Satellite Modem

Satellite

Satelliteup/down link

Telephone Socket

The Internet

Telephone Line

• This method uses a satellite to upload and download data. It is asymmetric meaning upload and download speeds are different.

Two-Way Satellite Broadband

Satellite Dish(one-way)

Computer

Satellite Modem

Satellite

Satelliteup/down link

The Internet

The satellites used are geosynchronous meaning they are currently hovering about 37,000 km above the Earth.

Because of the large distance they are not particularly great for downloading large quantities of data.

This makes them inappropriate for video conferencing and gaming.

Line of sight is required also meaning satellites need to be positioned as far away as possible.

Satellite

Optical Methods

(Infrared, fibre optic, Laser)

• This type of technology has been around for many years and are often found in remote controls for televisions and some computer consoles.

Infrared

Click!

Early mobile phones used infrared technology to allow data transfer to take place.

People used to share contacts and play games using infrared technology.

This soon became redundant because of the introduction of Bluetooth technology

One of the limitations of infrared technology was that it needed direct line of site and wouldn’t work over more than 10 metres.

Bandwidth was also very slow with a maximum speed of 115.2kbps.

Infrared

Communication can’t take place if something gets in the way.

X

This method of communication at speeds which have not been beaten by other optical communication methods.

This type of technology is mainly used where large distances are covered (over 100 metres).

You can find fibre optic cables in a lot of house holds which have an entertainment unit. Fibre optic cables are often used to transmit the sound from the device (such as a blu-ray player) to the amp.

Fibre Optic

• These work by having two laser devices in direct line of sight to each other.

• Each device can send and receive laser beams to each other.

Laser

Data is transmitted at the speed of light (like in fibre optics) but doesn’t need a physical connection.

Laser technology is easy to set up and is portable which means they could be used in different locations.

A TV crew could film an event and send the footage back to a satellite van which can then transmit to the station.

Video sent to receiver

Lasers work incredibly well but only when atmospheric conditions are right.

Problems often occur when the weather isn’t at its best.

Although they aren’t all that common, there have been experiments to communicate between satellites in space.

Bandwidths can reach speeds of around 1.5Gbps at distances of up to 4km.

Laser

Activity• Complete this table:

UTP Coaxial Fibre OpticAdvantages

Disadvantages

Communication Media

• It is important to consider the type of interconnection when building a network.

• Factors to consider include:– The predicted bandwidth.– The environment.– The distance between clients.– The level of security needed.– The cost of the interconnection.

• Computers can be connected to a network through different media. Sample media include:– Twisted pair.– Coaxial cable.– Fibre optics.– Wireless connections.

Communication Media

Many networks use this cable.

It is light, flexible and cheap and has been around a long time which means network engineers are familiar with it.

Used extensively at home to connect computers to the telephone system.

Consists of pairs of conductors covered in insulation material and then twisted together.

Within one cable you might have 4 pairs but there are different designs, each with their or characteristics.

Twisting the wire reduces the effects of electrical interference at minimal costs.

You can further reduce this electrical interference by covering the cables in silver foil.

Unshielded twisted pair (UTP)

• Many people have debated the ups and downs of UTP over STP (Shielded Twisted Pair) and these discussions can be found on the net.

• It is important to note that the bandwidth of UTP is slower then coaxial and fibre optic cable and you need repeaters more often with UTP also.– i.e. It has more resistance and a higher level of data

degradation over longer distances.

Unshielded twisted pair (UTP)

Unshielded Twisted Pair (UTP)

Coaxial• Made up of a central conducting core wrapped in protection within a cable.

• Wrapped around the installation is a think metal sheath that provides the electrical interference protection.

• Finally, the cable has an outer covering.

• It is the cable of choice when connecting a television to an aerial.

• It is heavier and less flexible compared to a UTP and also more expensive too.

• Cable lengths can be longer than UTP but still not as long as fibre optic cables.

• You need less repeaters than a UTP too and is mechanically strong and has a high level of resistance to electrical interference.

Coaxial

Fibre optic cable• Consists of glass cores surrounded in protective material.

• Signals are sent via light sources. As signals are not electrical they do not suffer from electrical interference.

• Also, the cables do not suffer from the effects of moisture as they are non-metallic (like most cables).

• The cables are extremely brittle compared to metallic cables and need to be well protected.

Fibre optic cable• They are high bandwidth compared to UTP cables and are often

used for networks were video conferencing is needed.

• The cost of these cables are relatively cheap compared to metallic ones but they require specialists to install them which makes them expensive overall.

• Often used as the backbone for LAN networks to connect servers to switches and located in places where there are clusters of computers.– After the switches UTP and coaxial cables tend to be used.

• The bandwidth is so impressive that speeds of up to 1Gbit/sec is easily reached.

Fibre optic cable

Fibre optic cable• Note: the angle of the acceptance cone. If the cable

is bent too much the light will not be able to travel through it.

Activity• Complete this table:

UTP Coaxial Fibre OpticAdvantages

Disadvantages

Activity1. Describe how wireless networks can be used

to improve the speed and delivery of medical care at the scene of an emergency, perhaps in an ambulance.

2. Describe the use and the technology behind the wireless network used to deliver education to children in remote parts of the Australian outback. You will need to research this.

Activity1. Discuss the problem of balancing ‘over engineering’ with ‘future

proofing’ in a new network.

2. Use the Internet and define the term Wi-Fi. Describe its benefits in the business environment.

3. What is UTP and list the reasons why it is commonly used for LANs.

4. Discuss in what circumstances a company might selecta. Coaxial Cable orb. Fibre Optics for its network.

5. Define Ethernet.

Activity1. Explain what is meant by ‘collision avoidance’ and ‘collision

detection’.

2. How does an Ethernet deal with data collision?

3. What is meant by a ‘switched Ethernet LAN’?

4. Why do communications slow down when there are many users connected to a LAN?

5. Describe how a switch can reduce the number of collisions in a LAN and therefore improve communications.