WiFi Networking

8/3/2019 WiFi Networking

1/47

WiFi Networking


2/47

WiFi

WiFi is the wireless way to handle networking.

It is also known as 802.11 networking.

The big advantage of WiFi is its simplicity.

You can connect computers anywhere in your homeor office without the need for wires. The computers

connect to the network using radio signals, andcomputers can be up to 100 feet or so apart.


3/47

Outline for Today

The next slides, we will discuss the basic technologythat makes WiFi networking possible.

Then we will discuss the hardware you need tocreate a WiFi network, and help you understandhow to set up and access a WiFi hotspot in your

home.

Finally, we will look at a demonstration by DimitriDemergis.


4/47

Wireless NetworkingStandards

WiFi refers to the protocols that allow wirelessnetworking.

These protocols are codified in standards.

Standards are mutually agreed upon rules adoptedby the industry on how the wireless networksoperate.

There are several standards that enable wirelesslocal area networks (WLANs).


5/47

Wireless NetworkingStandards

Some WLAN standards include: HiperLAN,Bluetooth, HomeRF.

There are a couple of standards that describe Wi-Fi. All of them are part of the 802.11 suite.

The core protocols are listed in the 802.11standards, which was originally available in 1997.


6/47

802.11 Suite

Since then, several new extensions have beenadded to the core 802.11 protocols.

The most relevant of these additions are: 802.11a,802.11b, and 802.11g.

Next time, we will look at this core protocol (802.11)and these three expansions in more detail.


7/47

Understanding WirelessNetworking


8/47

Walkie-Talkie Network

If you want to understand wireless networking at itssimplest level, think about a pair of $5 walkie-talkiesthat you might purchase at Wal-Mart.

These are small radios that can transmit and receiveradio signals.

Recall, when you talk into a Walkie-Talkie, yourvoice is picked up by a microphone, encoded onto aradio frequency and transmitted with the antenna.


9/47

Walkie-Talkie Network (Contd)

Another walkie-talkie can receive the transmissionwith its antenna, decode your voice from the radiosignal and drive a speaker.

Simple walkie-talkies like this transmit at a signalstrength of about 0.25 watts, and they can transmitabout 500 to 1,000 feet.

We wish to consider how these walkie-talkies can beused to communicate between the two computers.


10/47


In order to do this, we require

Each computer is equipped with a walkie-talkie.

We would give each computer a way to setwhether it wants to transmit or receive.

And we would give the computer a way to turn its

binary 1s and 0s into two different beeps that thewalkie-talkie could transmit and receive andconvert back and forth between beeps and 1s/0s.


11/47


This would actually work.

The only problem would be that the data rate would

be very slow. A $5 walkie-talkie is designed tohandle the human voice (and it's a pretty scratchyrendition at that), so you would not be able to sendvery much data this way. Maybe 1,000 bits persecond.

Another problem: the walkie-talkies could not beused to connect to the internet.


12/47

WiFis Radio Technology

The radios used in WiFi are not so different from theradios used in $5 walkie-talkies.

They have the ability to transmit and receive.

They have the ability to convert 1s and 0s into radio

waves and then back into 1s and 0s.

There are major differences, of course.


13/47


(Contd)

WiFi radios that work with the 802.11b and 802.11gstandards transmit at 2.4 GHz, while those thatcomply with the 802.11a standard transmit at 5 GHz.

Normal walkie-talkies normally operate at 49 MHz.The higher frequency allows higher data rates.

WiFi radios use much more efficient codingtechniques (process of converting 0s and 1s intoefficient radio signals) that also contribute to themuch higher data rates.


14/47


(Contd)

The radios used for WiFi have the ability to changefrequencies.

For example, 802.11b cards can transmit directly onany of three bands, or they can split the availableradio bandwidth into dozens of channels andfrequency hop rapidly between them.

The advantage of frequency hopping is that it ismuch more immune to interference and can allowdozens of WiFi cards to talk simultaneously withoutinterfering with each other.


15/47

802.11b, 802.11a, and 802.11g

802.11b was first to reach the marketplace. It is theslowest and least expensive of the three. 802.11btransmits at 2.4 GHz and go up to 11 Mbps.

802.11a was next. It operates at 5 GHz and canhandle up to 54 Mbps.

802.11g is a mix of both worlds. It operates at2.4Ghz (giving it the cost advantage of 802.11b) but

it has the 54 megabits per second speed of802.11a. It is also backward compatible to802.11b.

Most WiFi cards nowadays are capable of all three

of these radio technologies.


16/47

Adding WiFi to Your Computer

One of the best things about WiFi is how simple it is.

Many new laptops already come with a WiFi cardbuilt in -- in many cases you don't have to doanything to start using WiFi.

It is also easy to add a WiFi card to an older laptopor a desktop PC.


17/47

Adding WiFi to an OlderComputer

Buy a 802.11a, 802.11b or 802.11g network card.

For a laptop, this card will normally be a PCMCIAcard that you slide into a PCMCIA slot on your

laptop. Or you can buy a small external adapterand plug it into a USB port.

For a desktop machine, you can buy a PCI cardthat you install inside the machine, or a small

external adapter that you connect to the computerwith a USB cable.

Install the card


18/47

Adding WiFi to an OlderComputer

Install the drivers for the card

Find an 802.11 hotspot.

Access the hotspot.

Hotspot: a connection point for a WiFi network. It is asmall box that is hardwired into the Internet. The boxcontains an 802.11 radio that can simultaneously talkto up to 100 or so 802.11 cards.


19/47

Locating Hotspots

There are many WiFi hotspots now available inpublic places like restaurants, hotels, libraries andairports. For example, Starbucks.

The number of hotspots in the world is growing daily.

You can also create your own hotspot in your home,

as we will see in a little bit.

One way to find a hotspot is to go on-line.


20/47

Finding Hotspots O-Line


21/47

Connecting to a Hotspot

There are actually two steps to making a connection.

The first is to have your notebook "talk" to thehotspot, which means that the hardware and hotspotmust recognize each other. This should happenautomatically as long as your wireless hardware isturned on and new.


22/47

Connecting to a Hotspot(Contd)

On the newest machines, an 802.11 card willautomatically connect with an 802.11 hotspot and anetwork connection will be established. As soon asyou turn on your machine, it will connect and you willbe able to browse the Web, send email, etc. usingWiFi.

On older machines you often have to go through asimple 3-step process to connect to a hotspot.


23/47


Access the software for the 802.11 card -- normallythere is an icon for the card down in the system trayat the bottom right of the screen.

Click the "Search button" in the software. The cardwill search for all of the available hotspots in thearea and show you a list.

Double-click on one of the hotspots to connect to it.


24/47


On ancient 802.11 equipment (more than 2-3 yearsold), there is no automatic search feature.

You have to find what is known as the SSID of the

hotspot (usually a short word of 10 characters orless) as well as the channel number (an integerbetween 1 and 11) and type these two pieces ofinformation in manually.

All the search feature (in newer equipment) is doing

is grabbing these two pieces of information from theradio signals generated by the hotspot anddisplaying them for you.


25/47


On most notebook models, you will see some sort ofsignal icon on the bottom right hand corner of yourscreen or a lit indicator on the notebook itself, which

will give you feedback for "On" and signal strength(a red screen means your radio is Off; a greenscreen indicates it is On).

OFF ON


26/47


You can also see the quality of the signal by clickingon the radio icon (may vary by system):


27/47


Your next step is to sign up with a wireless Internetservice provider and configure your notebookaccording to their instructions.

Most of the time, this is a matter of simply launchingyour web browser. It will automatically go to thewireless service provider's sign-in page.

Keep in mind that different hotspot locations workwith different service providers, but each hotspotlocation should provide easy and clear instructionson how to connect.


28/47


If you don't subscribe to a service, chances are youwill need to use your credit card to pay for accessevery time you want to connect.

Always make sure you know what the serviceprovider charges, as there can be a wide range ofprices.

After this, you will end up at the log-on page of thewireless provider (or, in some cases, the wirelesslocation).


29/47


If so, simply follow the instructions to sign up for theservice, or enter your user name and password ifyou are already a customer.

Once you successfully log on, you should see thefollowing icon in your tool bar, indicating theconnection has been made:


30/47

WiFi Security

WiFi hotspots can be open or secure.

If a hotspot is open, then anyone with a WiFi cardcan access the hotspot.

If it is secure, then the user needs to know a WEP

key to connect.

WEP stands for Wired Equivalent Privacy


31/47

WiFi Security (Contd)

WEP is an encryption system for the data that802.11 sends through the air.

Encryption system prevents any non-authorizedparty from reading or changing data.

Specifically, it is the process of encoding bit streamin such a way that only the person (or computer)with the key (a digital sequence) can decode it.


32/47

WEP

WEP has two variations: 64-bit encryption (really 40-bit) and 128-bit encryption (really 104-bit).

40-bit encryption was the original standard but wasfound to be easily broken.

128-bit encryption is more secure and is what mostpeople use if they enable WEP.

For a casual user, any hotspot that is using WEP isinaccessible unless you know this WEP key.


33/47

WEP (Contd)

If you are setting up a hotspot in your home, youmay want to create and use a 128-bit WEP key to

prevent the neighbors from casually eavesdroppingon your network.

Whether at home or on the road, you need to know

the WEP key, and then enter it into the WiFi card'ssoftware, to gain access to the network.


34/47

Setting up a Hotspot at Home

If you already have several computers hookedtogether on an Ethernet network and want to add awireless hotspot to the mix, you can purchase a

Wireless Access Point and plug it into the Ethernetnetwork.

Wireless Access Point


35/47

Setup #1


36/47

Alternate Setup using aWireless Router

If you are setting up a network in your home for thefirst time, or if you are upgrading, you can buy aWireless Access Point Router.

This is a single box that contains: 1) a port to connect to your cable modem or DSL

modem, 2) a router, 3) an Ethernet hub,

4) a firewall and 5) a wireless access point.

You can connect the computers in your home to thisbox either with traditional Ethernet cables or withwireless cards.


37/47

Alternate Setup (Contd)


38/47

WiFi Range

Regardless of which setup you use, once you turnyour Wireless Access Point on, you will have a WiFihotspot in your house.

In a typical home, this hotspot will provide coveragefor about 100 feet (30.5 meters) in all directions,although walls and floors do cut down on the range.

Even so, you should get good coverage throughouta typical home. For a large home, you can buyinexpensive signal boosters to increase the range ofthe Hotspot.


39/47

One Type of Amplifier

Or a directionalantenna can beused to give

better range ina particulardirection.

A h W A lif WiFi


40/47

Another Way to Amplify WiFiSignals

A WiFi repeateris installed toextendcoverage.

WirelessAccess Point


41/47

Configuring a Hotspot

Most wireless access points come with defaultvalues built-in.

Once you plug them in, they start working with thesedefault values.

However, you may want to change things.

You normally get to set three things on your accesspoint.

Thi t C fi i


42/47

Things to Configure in aHotspot

The SSID -- Service Set IDentifier is a sequence ofcharactersthat uniquely names a WLAN.

It will normally default to the manufacturer's name

(e.g. "Linksys" or "Netgear"). You can set it to any word or phrase you like.

The channel the radio link used by accesspoint/router to communicate to wireless devices.

Normally it will default to channel 6. However, if a nearby neighbor is also using an

access point and it is set to channel 6, there canbe interference. Choose any other channelbetween 1 and 11.


43/47

Things to Configure (Contd)

The WEP key -- The default is to disable WEP.

If you want to turn it on, you have to enter a WEPkey and turn on 128-bit encryption.

WEP can be in text format.

Access points come with simple instructions forchanging these three values. Normally you do it witha Web browser. Once it is configured properly, youcan use your new hotspot to access the Internetfrom anywhere in your home.


44/47

Infrastructure versus Ad Hoc

All the connections that we have talked about todayrequire a connection from a device equipped with awireless network interface card (NIC) to a wirelessaccess point.

Generally, all such connections are operating inwhat is known as the infrastructure mode. Here thewireless network resembles a cellular architecture.

Wireless devices can also communicate directly witheach other, i.e., it is not required that theycommunicate with an access point first.


45/47

Infrastructure versus Ad Hoc

When devices with NIC cards communicate directlywith each other, the wireless network operates in adhoc mode.

Essentially peer-to-peer communication is enabled.


46/47

Ad Hoc Mode

Ad Hoc connections can be used to shareinformation directly between devices. This mode isalso useful for establishing a network where wirelessinfrastructure does not exist.

Some uses,

Synchronize data between devices.

Retrieve multimedia files from one device and

play them on another device. Print from a computer to a printer without wires.

There are many applications of ad hoc networking inthe military and in specialized networks.


47/47

Demo and Next Time

Next, we will look at some demonstrations of WiFinetworks operating in infrastructure mode.

Next time, we will look at a demonstration of the adhoc mode.

Next time, we will also look at the protocols thatenable all this WiFi networking.

Documents

WiFi Networking