Wi-Fi Technology

1. INTRODUCTION

1.1. NEED FOR A NETWORK:

In the world of computers, networking is the practice of linking two or more computing devices

together for the purpose of sharing data. Networks are built with a mix of computer hardware

and computer software. Networking provides various advantages like sharing of resources, files

and information as well as sharing of Internet connection. With the advent of technology, it is

possible to share data between computers without physical connections.

Inter-networking evolved as a solution to three key problems: isolated LANs, duplication of

resources, and a lack of network management. Isolated LANS made electronic communication

between different offices or departments impossible. Duplication of resources meant that the

same hardware and software had to be supplied to each office or department, as did a

separate support staff. This lack of network management meant that no centralized method of

managing and troubleshooting networks existed.

1.2. WIRED V/S WIRELESS NETWORKS:

The wired network that has been in use till date has certain limitations as follows:

There is difficulty in installing the wired network, as it requires the fiber optic cables to

be put up, which may not be feasible in all cases.

The cost of installation is high and hence is not economic to one and all.

One cannot connect the network wherever one wants to do so since it requires space

for the cables to run.

Connecting the laptop to the network becomes difficult.

The traffic increases with everyone trying to use the services at a time.

Mobility is not much and hence productivity declines.

The performance is not that great and can be improved.

The speed of data transfer is less.

Due to the above pitfalls of the wired Ethernet network connection, the wireless networks have

come up.

Wireless LANs provide all the functionality of wired LANs, but without the physical

constraints of the wire itself.

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Wireless LAN configurations include independent networks, offering peer-to-peer

connectivity, and infrastructure networks, supporting fully distributed data

communications.

A wireless LAN-LAN bridge is an alternative to cable that connects LANs in two

separate buildings.

Wireless LANs provide flexibility, improved quality and easy installation.

1.3. VARIOUS WIRELESS TECHNOLOGIES:

In the process of development in technology, a variety of wireless technologies have been

developed. Various application specific technologies have been developed. The various

wireless technologies are listed below:

1. WI-FI (802.11):

It is used for wireless Internet access in devices like laptops, computers. It has a limited

range and hence used for local area network.

2. WI-MAX (802.16):

It is an emerging wireless technology, which will be used for metropolitan area network.

Thus the speed and range is high.

3. BLUETOOTH (802.15):

It is used to connect two peripherals like computers within a range of 33 feet.

4. GSM (GLOBAL SYSTEM FOR MOBILE COMMUNICATION):

It is used in digital cellular telephone system.

5. 3GSM:

It has the same use as GSM but has a higher speed.

6. GPRS (GENERAL PACKET RADIO SERVICE):

It is an interface overlaid on existing GSM networks to allow for Internet access.

7. CDMA (CODE DIVISION MULTIPLE ACCESS):

It is used in digital telephone system mainly in U.S.

8. CDPD (CELLULAR DIGITAL PACKET DATA):

It is used to transmit data over analog cellular networks. In today’s world it is not

applicable.

9. TDMA (TIME DIVISION MULTIPLE ACCESSS):

It is also used in digital telephone system with a speed of 64-120 Kbps.

1.4. WI-FI IN A NUTSHELL.

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IEEE 802.11 is a standard that digresses slightly from the OSI model in that it provides a

standard for wireless data transmission. To do this, the standard defines the MAC and PHY

layers of the OSI model for use of DSSS, FDSS, and OFDM. The MAC layer is responsible for

managing data transfer from higher-level functions to PHY media. This standard details how

data is modulated for transmission and correlated at the receiving end. The topology of wireless

networks is fairly simple. In a BSS, an AP is connected to an existing LAN from which wireless

stations can access the network. An ESS extends this topology to expand the network. Using an

ad hoc topology, stations (PCs) can communicate directly with one another. Mobility measures

permit wireless users to access the wireless network from any point on the network and maintain

their connection regardless of where they roam on the network.

802.11 has a number of built-in measures, including WEP, to protect a network from external

threats. Should the network manager feel that WEP is not adequate to protect the network based

on the previous equation, a number of other measures can be added to the network to heighten

the level of security in the network. With the addition of external security measures, 802.11

networks can be as secure as most wired networks

In summary, 802.11 presents the best of all possible worlds for the small office/home office

(SOHO) subscriber in providing telephony as good or better than the PSTN while delivering an

overwhelming advantage in bandwidth. The spread of broadband Internet access to a majority of

households will probably happen in the form of 802.11. The demand for broadband will have

the effect of bringing different forms of delivery (DSL, cable modem, and 802.11) into the

marketplace. The form of access that is least expensive and most easily deployed will win.

2. IEEE 802.11 ARCHITECTURE

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802.11 supports three basic types of topologies:

1. Ad-Hoc/IBSS

2. BSS (Basic Services set)

3. ESS (Extended services set)

2.1.AD – HOC / IBSS

Ad hoc networking connects a set of PCs with wireless adapters. This arrangement is sometimes

called peer-to-peer networking. Any time two or more wireless adapters within range of each

other can set up an independent network. These on-demand networks typically require no

administration or pre-configuration.

Advantages:

1. Cost savings

2. Gives peer-to-peer networks in some applications a great deal of power.

3. Rapid setup time

4. Can’t provide access to applications and servers on a wired network.

Disadvantages:

1. Covers a very small area

2. Security

FIG1.AD-HOC ARCHITECTURE

2.2. BASIC SERVICE SET / INFRASTRUCTURE.

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A basic service set is made of stationary or mobile wireless stations and a possible central base

station, known as the Access point (AP). There are two types of access points:

i. Dedicated hardware access points (HAP).

ii. Software Access Points that run on a computer equipped with a wireless network

interface card as used in an ad-hoc or peer-to-peer wireless network. It includes features

not commonly found in hardware solutions, such as extensive configuration flexibility,

but may not offer the full range of wireless features defined in the 802.11 standard

Access points can extend the range of independent WLANs by acting as a repeater,

effectively doubling the distance between wireless PCs.

The access point also performs a number of other roles, such as connecting the nodes to the

Internet or other WAN (wide area network), connecting multiple wireless networks, connecting

the wireless nodes to a wired network, and providing management and security functionality.

The access points not only provide communication with the wired network but also mediate

wireless network traffic in the immediate neighborhood. Multiple access points can provide

wireless coverage for an entire building or campus.

Advantages:

1. Connect to the wired network and allow users to efficiently share network resources

2. Provides management and security functionality

3. Covers a large area

FIG2.BSS / INFRASTRUCTURE NETWORK

2.3. EXTENDED SERVICE SET / INFRASTRUCTURE.

Ethernet LAN

Access Point

Laptop

Desktop computer Desktop

Computer

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The Extended service set (ESS) is made up of two or more BSSs with APs. The BSSs are

connected through a distribution system, which is usually a wired LAN. The distribution system

connects the APs in the BSSs. The distribution system can be any IEEE LAN such as Ethernet.

Thus, ESS uses 2 types of stations: mobile and stationary. The mobile stations are normally

inside the BSS; the stationary stations are AP stations that are a part of the wired LAN.

In this network, the stations within reach of one another can communicate without the use of an

AP. However, communication between two stations in two different BSSs usually occurs via

two APs.

Advantages:

1. Covers a larger area

2. Allows sharing of network resources

FIG3.ESS/INFRASTRUCTURE

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3. UNDERLYING TECHNOLOGY

3.1. OPEN SYSTEM INTERCONNECTION (OSI) MODEL.

The Open System Interconnection (OSI) reference model describes how information from a

software application in one computer moves through a network medium to a software

application in another computer. The OSI reference model is a conceptual model composed of

seven layers, each specifying particular network functions. The model was developed by the

International Organization for Standardization (ISO) in 1984, and it is now considered the

primary architectural model for inter computer communications. The OSI model divides the

tasks involved with moving information between networked computers into seven smaller, more

manageable task groups. Each layer is reasonably self-contained so that the tasks assigned to

each layer can be implemented independently. This enables the solutions offered by one layer to

be updated without adversely affecting the other layers.

The seven layers of the OSI reference model can be divided into two categories:

1. Upper layers: The upper layers of the OSI model deal with application issues and

generally are implemented only in software. The highest layer, the application layer, is

closest to the end user. Both users and application layer processes interact with software

applications that contain a communications component. The term upper layer is

sometimes used to refer to any layer above another layer in the OSI model.

2. Lower layers: The lower layers of the OSI model handle data transport issues. The

physical layer and the data link layer are implemented in hardware and software. The

lowest layer, the physical layer, is closest to the physical network medium (the network

cabling, for example) and is responsible for actually placing information on the medium.

Actual communication is made possible by using communication protocols. A protocol is a

formal set of rules and conventions that governs how computers exchange information over a

network medium. A protocol implements the functions of one or more of the OSI layers. A

system that implements protocol behavior consisting of a series of these layers is known as a

'protocol stack' or 'stack'. Protocol stacks can be implemented either in hardware or software, or

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a mixture of both. Typically, only the lower layers are implemented in hardware, with the higher

layers being implemented in software.

FIG4: NETWORK ARCHITECTURE BASED ON OSI MODEL

Description of layers

1. Physical Layer:

The physical layer defines the electrical, mechanical, procedural, and functional specifications

for activating, maintaining, and deactivating the physical link between communicating network

systems. Physical layer specifications define characteristics such as voltage levels, timing of

voltage changes, physical data rates, maximum transmission distances, and physical connectors.

This includes the layout of pins, voltages, and cable specifications. Hubs and repeaters are

physical-layer devices. The major functions and services performed by the physical layer are:

establishment and termination of a connection to a communications medium.

participation in the process whereby the communication resources are effectively shared among

multiple users. For example, conversion between the representation of digital data in user

equipment and the corresponding signals transmitted over a communications channel. These are

signals operating over the physical cabling - copper and fiber optic, for example. SCSI operates

at this level.

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It conveys the bit stream - electrical impulse, light or radio signal -- through the network at the

electrical and mechanical level. It provides the hardware means of sending and receiving data on

a carrier, including defining cables, cards and physical aspects. Fast Ethernet, RS232, and ATM

are protocols with physical layer components.

2. Data link layer:

The Data link layer provides the functional and procedural means to transfer data between

network entities and to detect and possibly correct errors that may occur in the Physical layer.

Different data link layer specifications define different network and protocol characteristics,

including physical addressing, network topology, error notification, sequencing of frames, and

flow control. Physical addressing (as opposed to network addressing) defines how devices are

addressed at the data link layer. Network topology defines how devices are to be physically

connected, such as in a bus or a ring topology. Error notification alerts upper-layer protocols

that a transmission error has occurred, and the sequencing of data frames reorders frames that

are transmitted out of sequence. Finally, flow control moderates the transmission of data so that

the receiving device is not overwhelmed with more traffic than it can handle at one time.

The data link layer is divided into two sublayers: The Media Access Control (MAC) layer and

the Logical Link Control (LLC) layer.

The MAC sublayer controls how a computer on the network gains access to the data and

permission to transmit it. It thus manages protocol access to the physical network medium.

The LLC layer controls frame synchronization, flow control and error checking. The Logical

Link Control (LLC) sublayer of the data link layer manages communications between devices

over a single link of a network.

3. Network layer:

The Network layer provides the functional and procedural means of transferring variable length

data sequences from a source to a destination via one or more networks while maintaining the

quality of service requested by the Transport layer. The Network layer performs network

routing, switching, flow control, segmentation/desegmentation, and error control functions. It

converts the segments into smaller datagrams that the network can handle. The router operates

at this layer -- sending data throughout the extended network and making the Internet possible,

although there are layer 3 (or IP) switches. This is a logical addressing scheme - values are

chosen by the network engineer. The addressing scheme is hierarchical.

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4. Transport layer:

The purpose of the Transport layer is to provide transparent transfer of data between end users,

thus relieving the upper layers from any concern with providing reliable and cost-effective data

transfer. The transport layer controls the reliability of a given link. Some protocols are stateful

and connection oriented. This means that the transport layer can keep track of the packets and

retransmit those that fail. The best known example of a layer 4 protocol is TCP.

5. Session layer:

The session layer establishes, manages, and terminates communication sessions.

Communication sessions consist of service requests and service responses that occur between

applications located in different network devices. These requests and responses are coordinated

by protocols implemented at the session layer. The session layer sets up, coordinates, and

terminates conversations, exchanges, and dialogues between the applications at each end.

6. Presentation layer:

The Presentation layer relieves the Application layer of concern regarding syntactical

differences in data representation within the end-user systems. It provides a variety of coding

and conversion functions that are applied to application layer data. These functions ensure that

information sent from the application layer of one system would be readable by the application

layer of another system. Encoding, encryption and similar manipulation of the presentation of

data is done at this layer.Presentation layer implementations are not typically associated with a

particular protocol stack.

7. Application layer:

This layer supports application and end-user processes. This layer interfaces directly to and

performs common application services for the application processes.

This layer interacts with software applications that implement a communicating component.

Such application programs fall outside the scope of the OSI model. Application layer functions

typically include identifying communication partners, determining resource availability, and

synchronizing communication.

When identifying communication partners, the application layer determines the identity and

availability of communication partners for an application with data to transmit.

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When determining resource availability, the application layer must decide whether sufficient

network resources for the requested communication exist. In synchronizing communication, all

communication between applications requires cooperation that is managed by the application

layer.

The above OSI model is the same for both wired and wireless transmission. The only difference

comes in the protocol used at the physical layer and the data link layer, which is different for

both wireless and wired transmissions.

Thus here we now concentrate on the protocols used at the physical layer and data link layer

while communicating using Wi-Fi technology.

3.2. PHYSICAL LAYER

IEEE 802.11 defines specifications for the conversion of bits to a signal in the physical layer.

The 1997 802.11 standard specifies three transmission techniques allowed in the physical layer.

One specification is in infrared and the other two are short-range radio frequency.

INFRARED TECHNOLOGY:

The infrared option uses line of sight transmission at .85 or .95 microns. Two speeds are

permitted: 1Mbps and 2Mbps. Infrared signals cannot penetrate walls, so cells in different

rooms are well isolated from each other. Nevertheless, due to the low bandwidth (and the fact

that sunlight swamps infrared signals), this is not a popular option.

RADIO FREQUENCY TECHNOLOGY:

The other basic technology is Spread spectrum radio. The fundamental concept of spread

spectrum radio is the use of a wider frequency bandwidth than that needed by the information

that is transmitted. Using extra bandwidth would seem to be wasteful, but it actually results in

several benefits, including reduced vulnerability to jamming, less susceptibility to interference,

and coexistence with narrowband transmissions. Several spread spectrum techniques are

available, out of which FHSS and DSSS are most widely used.

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FHSS (FREQUENCY-HOPPING SPREAD SPECTRUM):

IEEE 802.11 FHSS describes the frequency-hopping spread spectrum (FHSS) method for signal

generation in a 2.4-GHz ISM band. FHSS is the method in which the sender sends on one

carrier frequency for a short period of time, then hops to another carrier frequency for the same

amount of time, hops again to still another for the same amount of time, and so on. After N

hoppings, the cycle is repeated .If the bandwidth of the original signal is B, then the allocated

bandwidth of the spread spectrum is N*B. In FHSS the sender and receiver agree on the

sequence of the allocated bands. Hence spreading makes it difficult for unauthorized persons to

make sense of transmitted data. FHSS uses a 2 .4 GHz industrial, scientific, and medical band.

The modulation technique `in this specification is FSK at 1 Mbands/s. The system allows 1 or 2

bits/baud, which results in a data rate of 1 or 2 Mbps.

DSSS (THE DIRECT SEQUENCE SPREAD SPECTRUM):

IEEE 802.11 DSSS describes the direct sequence spread spectrum (DSSS) method for signal

transmission in a 2.4 GHz ISM band. In DSSS, each bit sent by the sender is replaced by a

sequence of bits called a chip code. To avoid buffering, however, the time needed to send one

chip must be the same as the time needed to send one signal bit. If N is the no. of bits in each

chip code, then the data rate for sending chip codes is N times the data rate of the original bit

stream. DSSS uses 2.4 GHz ISM band. The bit sequence uses the entire band. The modulation

technique in this specification is PSK at 1 Mbaud/s. The system allows 1 or 2 bits/baud, which

results in a data rate of 1 or 2 Mbps.

MEDIUM ACCESS CONTROL (MAC) SUBLAYER

The MAC sublayer is the sublayer of data link layer. It controls how a computer on the network

gains access to the data and permission to transmit it. It thus manages protocol access to the

physical network medium. Thus the MAC layer is responsible for managing data transfer from

higher-level functions to the physical media.

Devices using the IEEE 802.11 PHY and MAC as part of a WLAN are called stations. Stations

can be endpoints or APs. APs are stations that act as part of the DS and facilitate the distribution

of data between endpoints. The MAC provides nine logical services: authentication,

deauthentication, association, disassociation, reassociation, distribution, integration,

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privacy, and data delivery. An AP uses all nine services. An endpoint uses authentication,

deauthentication, privacy, and data delivery. Each service utilizes a set of messages with

information elements that are pertinent to the services.

MAC data transfer is controlled through two distinct coordination functions. The first is the

distributed coordination function (DCF), which defines how users contend for the medium as

peers. DCF data transfers are not time sensitive and delivery is asynchronous i.e. they do not use

any kind of central control. The second is the point coordination function (PCF), which provides

centralized traffic management for data transfers that are sensitive to delay and require

contention-free access. Thus it uses the base station to control all activity in its cell. All

implementations must support DCF but PCF is optional.

Distributed Coordination Function (DCF) The DCF defines how the medium is shared

among members of the wireless network. It provides mechanisms for negotiating access to the

wireless medium as well as mechanisms for reliable data delivery. One of the fundamental

differences between wired and wireless media is that it is difficult to detect and manage data

collisions on wireless media. The primary reason for this is that stations in a radio network are

not guaranteed to hear every other station's transmissions. This is typically the case when an AP

is used in IEEE 802.11's infrastructure BSS and is called the hidden-node problem.

Point Coordination Function (PCF) The PCF polls associated stations and manage frame

transmissions on their behalf. A station performing PCF traffic management is called a point

coordinator (PC). The PCF is an optional capability that provides connection-oriented services

for delay-sensitive traffic. The PCF is more complex to implement, but it provides a moderate

level of priority frame delivery for time-sensitive transmissions

The basic access method for 802.11 is the DCF, which uses CSMA/CA. This requires each

station to listen for other users. If the channel is idle, the station may transmit. If the station is

busy, it waits until transmission stops and then enters into a random back off procedure. This

prevents multiple stations from seizing the medium immediately after completing the preceding

transmission.

4. VERSIONS OF WI-FI

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The WLAN standards began with the 802.11 standard, developed in 1997 by the IEEE. This

base standard allowed data transmission of up to 2 Mbps. Over time, this standard has been

enhanced. These extensions are recognized by the addition of a letter to the original 802.11

standard. Thus, various standards have come up but the following are the ones that are being

used. A comparison of the most commonly used standards is discussed below.

TABLE 1

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TABLE.1 continued

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5. SECURITY

Security can be defined as keeping people from doing things you do not want them to do with,

on, or from your data, computers, or peripheral devices. Stored information, the accuracy and

value of information, access to internal and external services, and the organization's privacy are

at risk.

Unlike wired systems, which can be physically secured, wireless networks are not confined to

the inside of buildings. They can be picked up as far as 1,000 feet outside of the premises with a

laptop and a gain antenna. This makes wireless local area networks (WLANs) inherently

vulnerable to interception.

The basic security mechanisms are WEP, password protected shared drives and resources,

changing the network name from the default (the service set identifier [SSID]), using Media

Access Control (MAC) address filtering, using session keys, and using a virtual private network

(VPN) system.

5.1. BASIC 802.11 SECURITY AND ITS KNOWN PROBLEMS

When IEEE 802.11b was first defined, its security depended on two basic security mechanisms:

the SSID and WEP. Some manufacturers have added MAC address filtering to their products.

The SSID is a string used to define a common roaming domain among multiple access points

(APs). Different SSIDs on APs can enable overlapping wireless networks. The SSID was once

thought to be a basic password without which the client could not connect to the network.

However, this claim can be easily overridden since APs broadcast the SSIDs multiple times per

second and any 802.11 analysis tool can be used to read it. Because users often configure

clients, this so-called password is often widely known.

5.2. WIRED EQUIVALENT PROTOCOL (WEP)

The IEEE 802.11b standard also defines an authentication and encryption method called WEP

to mitigate security concerns.

802.11 uses WEP for both encryption and authentication.

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Four options are available when using WEP:

Do not use WEP.

Use WEP for encryption only.

Use WEP for authentication only.

Use WEP for authentication and encryption only.

WEP encryption is based on RC4, which uses a 40-bit key in conjunction with a 24-bit random

initialization vector (IV) to encrypt wireless data transmissions. If enabled, the same WEP key

must be used on all clients and APs for communication. Most vendors today also offer 128-bit

WEP (which uses a 104-bit key). This is a stronger encryption method that makes it more

difficult for eavesdroppers to decipher over-the-air transmissions.

To prevent unauthorized access, WEP also defined an authentication protocol. Two forms of

authentication are defined by 802.11b: open system and shared key.

Open system:

Open system authentication enables any 802.11b client to associate with the AP and skip the

authentication process. It can be used for public access WLANs, which can be found in coffee

shops, airports, hotels, conference centers, and other similar venues where the public is invited

to use the network. Typically, the open network authenticates the user using user name

password over a secure login web page. For closed networks such as the home or enterprise, this

mode can be used when other methods of authentication are provided.

Shared key:

Using shared key authentication, the AP sends a challenge phrase to the client radio that is

requesting authentication. The client radio encrypts the challenge phrase using the shared key

and returns it to the AP. If the AP successfully decrypts it back to the original challenge text, it

proves that the client has the correct private key. The client is then allowed to make a network

connection.

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To the casual observer, it would seem that the shared key authentication process is more secure

than the open key authentication process. However, since both the challenge phrase (which was

sent in clear text) and the challenge are available, a hacker can derive the WEP key. Thus,

neither open system authentication nor shared key authentication is secure.

Because the 802.11 standard relies on external key management services to distribute the secret

keys to each station and does not specify key distribution services, most 802.11 client access

cards and APs rely on manual key distribution. This means that the keys remain static unless the

network administrator changes them. This results in problems as changing the keys on each

station in a large network can be extremely time consuming. If a station is lost due to theft or

accident, the keys will need to be changed on all stations.

Another concern about the robustness of WEP is that it only provides at most four-shared static

encryption keys. This means that the four encryption keys are the same for all clients and APs

every time a client accesses the network. With enough time, physical proximity, and tools

downloaded from the Web, hackers can determine the encryption key being used and decrypt

data. Since the whole company is using the same set of keys at any one particular time, it is just

a matter of a few hours before enough data is collected to crack a 128-bit key.

5.3. MAC ADDRESS FILTERING.

Besides the two basic security mechanisms that 802.11 provides, many companies implement

MAC address filtering in their products. This mechanism is not flawless either.

The MAC address filter contains the MAC addresses of the wireless network interface cards

(NICs), which may associate with any given AP. Some vendors provide tools to automate the

entry and update processes; otherwise, this is an entirely manual process. A MAC filter is also

not very strong security since it is easy to discover known good MAC addresses with a sniffer.

Although not perfectly secure, MAC address filtering is one more layer on the onion—it makes

it more difficult for someone to gain access.

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5.4. WLAN SECURITY MODEL

Intruders can inflict four major classes of attack on a system: interception, fabrication,

modification, and interruption. A fifth class of attacks-repudiation-is an attack against the

accountability of information. It is an attack from within the system by either the source entity

or the destination entity.

ATTACK ON SOLVED BY

Interception Confidentiality and privacy Encryption/decryption

Fabrication Authenticity Authentication

Modification

Replay

Reaction

Integrity Digital signatures on every message can

solve attacks on Integrity.

Interruption Availability No effective solutions exist for interruption

/ Denial of Service attacks on availability.

Repudiation Nonrepudiation Non-repudication currently still suffers of

cases of identity theft.

TABLE 2

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FIG5.TYPICAL NETWORK ARCHITECTURE WITH WLAN AND WIRELESS FIREWALL

ADDED

MOBILITY AND SECURITY

If mobility is used, the solution must be secure during handoff. Handoffs open the network up to

a redirection attack. If the network is not properly secured, the intruder can take over the

communication with the destination entity after the handoff.

SECURITY POLICY

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TABLE.3

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TABLE.3 continued

CONCLUSION

802.11 has a number of built-in measures, including WEP, to protect a network from external

threats. Should the network manager feel that WEP is not adequate to protect the network based

on the previous equation, a number of other measures can be added to the network to heighten

the level of security in the network.

No network is absolutely secure. With the addition of external security measures, 802.11

networks can be as secure as most wired networks!

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6. APPLICATIONS AND FUTURE OF WI-FI

6.1. ADVANTAGES OF WI-FI

1. INSTALLATION FLEXIBILITY / ECONOMIC ADVANTAGE

Many businesses cannot receive broadband data services as no fiber-optic cable runs to their

building(s). The cost of securing permission to dig a trench through another property and

running the requisite cable is prohibitive. With 802.11b and its associated technologies, it is

possible to merely beam the data flow to that building. This solution carries over to the small

office/home market in that the data flow can be beamed to homes and small businesses in places

where no fiber-optic or other high-bandwidth service exists.

2. UNLICENSED SPECTRUM

Wireless data requires spectrum on which to transmit over the airwaves at a given frequency.

802.11 and most of its associated protocols operate on what is known as unlicensed spectrum.

Unlicensed spectrum does not require the operator to obtain an exclusive license to transmit on a

given frequency in a given region.

3. IMPROVED QUALITY OF LIFE WITH WIRELESS NETWORKS

When deployed as a broadband IP network solution, 802.11b will enable an improved standard

of living in the form of telecommuting, lower real-estate prices, and improved quality of life. A

wave of opportunity for wireless applications lies in the form of broadband deployment. The

potential for better living through telecommunications lies largely with the ubiquitous

availability of broadband.

4. DISRUPTIVE TECHNOLOGY

Although it is too early to point out the incumbent service providers driven out of business by

802.11b, its technologies could be potentially disruptive to incumbent telephone companies. The

migration of wired line telephone traffic to cellular is a powerful example of this trend.

5. MOBILITY IMPROVES PRODUCTIVITY AND SERVICE

Wireless LAN systems can provide LAN users with access to real-time information anywhere in

their organization. This mobility supports productivity and service opportunities not possible

with wired networks.

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6. INSTALLATION SPEED AND SIMPLICITY

Installing a wireless LAN system can be fast and easy and can eliminate the need to pull cable

through walls and ceilings.

7. SCALABILITY

Wireless LAN systems can be configured in a variety of topologies to meet the needs of specific

applications and installations. Configurations are easily changed and range from independent

networks suitable for a small number of users to full infrastructure networks of thousands of

users that allow roaming over a broad area.

8. INTEROPERABILITY WITH WIRED INFRASTRUCTURE

Most wireless LAN systems provide industry-standard interconnection with wired systems,

including Ethernet (802.3) and Token Ring (802.5). Standards-based interoperability makes the

wireless portions of a network completely transparent to the rest of the network. Wireless LAN

nodes are supported by network operating systems in the same way as any other LAN nodes via

drivers. Once installed, the NOS treats wireless nodes like any other component of the network.

9. SIMPLICITY/EASE OF USE

Users need very little new information to take advantage of wireless LANs.

Since only the access points of WLANs require cabling. The portable nature of WLANs lets

network managers preconfigure and troubleshoot entire networks before installing them at

remote locations. Once configured, WLANs can be moved from place to place with little or no

modification.

10. COST IS NOT A PROBLEM

WLAN eliminates the direct costs of cabling and the labor associated with installing and

repairing it. Second, because WLANs simplify moves, adds, and changes, they reduce the

indirect costs of user downtime and administrative overhead.

11. HIGH PERFORMANCE

Today's wireless networks offer high performance and bandwidth to keep all your essential

applications and transactions running. Throughput speeds comparable with or better than 10-

baseT wired networks provide reliable access to e-mail, the Internet, file sharing, and other

network resources away from the desk.

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6.2. DISADVANTAGES OF WI-FI

1. QUALITY OF SERVICE (QOS)

One of the primary concerns about wireless data delivery is that, like the Internet over wired

services, QoS is inadequate. Contention with other wireless services, lost packets, and

atmospheric interference are recurring problems for 802.11b and its associated wireless

protocols as alternatives to the PSTN. QoS is also related to the ability of a wireless Internet

service provider (WISP) to accommodate voice on its network. The PSTN cannot be replaced

until an alternative, competent replacement for voice over copper wire is available.

2. INTERFERENCE

The subscriber must have a direct line of sight from the service provider's transmitter. Many

people are concerned that the airwaves, since they are not as controllable or predictable as

copper wire or fiber cables, will deliver an inferior quality of service (QoS) or may be

susceptible to interference from other emitters in the electromagnetic spectrum.

As these local area networks (LANs) (and other devices in the ISM band) operate at fairly low

power levels, the actual risk of interference is relatively slight, but it does exist.

3. SECURITY

802.11b has two built-in basic network security mechanisms: the service set identifier (SSID)

and Wireless Equivalency Privacy (WEP). These measures may be adequate for residences and

small businesses, but they are inadequate for entities that require stronger security. A number of

measures that will provide the necessary level of security for the subscriber can be added to

those wireless networks.

4. RANGE

In most applications, 802.11b offers a range of about 100 meters. Range is a function of antenna

design and power, but mostly antenna design. With the right antenna, the range of 802.11 is

extended to tens of miles.

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6.3. APPLICATIONS OF WI-FI

SMART HOMES: We can create smart homes which consist of lighting that changes

with music, intelligent ACs, and drapes with remote access. Hi- Definition swivel

Plasma walls that can be summoned with the drop down projector and media streaming

in the entire house. The entire house is Wi-Fi enabled and the security system includes

surveillance cameras, motion sensors, and glass break and fire alarms. There are touch

panel controls for the entire system, remote access via Internet and an EPBAX that sends

you SMS alerts.

SMART CLASSROOMS: In these classrooms the boards can be connected to the

laptops used by each student using Wi-Fi technology. Training sites at corporations and

students at universities use wireless connectivity to facilitate access to information,

information exchanges, and learning. Senior executives in conference rooms can make

quicker decisions because they have real-time information at their fingertips.

TECH-CITY: There are cities in the U.S. where the entire city is connected using Wi-Fi

technology and hence the various users can be using Internet or all the devices connected

to the wireless network wherever they go in the city.

WI-FI IN TAIWAN: The Wi-Fi technology is being implemented at Taiwan while

constructing mobile hospitals, national parks, microwave in remote areas, voice and fax

machines, etc.

WI-FI LIFELINE FOR NEPAL’S FARMERS: They are taking advantage of a Wi-Fi

network set up in a remote region of the mountain kingdom where there are no phones or

other means of communication.

IN INDIA, MYSORE IS THE CITY: Mysore is going to be “the city” and better than

Bangalore. The authority has made a plan for making the entire city connected using the

Wi-Fi technology.

A quick network setup can be used for consulting or accounting audit teams or small

workgroups to increase productivity

Network managers in dynamic environments minimize the overhead of moves, adds, and

changes with wireless LANs, thereby reducing the cost of LAN ownership.

Network managers installing networked computers in older buildings find that wireless

LANs are a cost-effective network infrastructure solution.

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Wi-Fi Technology

Retail store IS managers use wireless networks to simplify frequent network

reconfiguration.

Trade show and branch office workers minimize setup requirements by installing

preconfigured wireless LANs needing no local support.

Warehouse workers use wireless LANs to exchange information with central databases

and increase their productivity.

Network managers implement wireless LANs to provide backup for mission-critical

applications running on wired networks.

Doctors and nurses in hospitals are more productive because hand-held or notebook

computers with wireless LAN capability deliver patient information instantly.

6.4: FUTURE OF WI-FI - WiMAX

WiMAX is short for Worldwide Interoperability for Microwave Access. The WiMAX

protocol is a way of networking computing devices together; for example to provide internet

access, in a similar way to Wi-Fi. WiMAX is a wireless metropolitan area network (MAN)

technology that can connect IEEE 802.11(Wi-Fi) hotspots to the Internet and provide a wireless

extension to cable and DSL for last mile (last km) broadband access. It has the potential to

enable millions more to access the Internet wirelessly, cheaply and easily. WiMAX is both

faster and has a longer range than Wi-Fi. However, WiMAX does not necessarily conflict with

Wi-Fi, but is designed to co-exist with it and may indeed complement it. According to WiMAX

promoters, a WiMAX base station would beam high-speed Internet connections to homes and

businesses in a radius of up to 50 km (31 miles); these base stations will eventually cover an

entire metropolitan area, making that area into a WMAN and allowing true wireless mobility

within it, as opposed to hot-spot hopping required by Wi-Fi.

TECHNOLOGY:

The original WiMAX standard, IEEE 802.16, specifies WiMAX in the 10 to 66 GHz range.

802.16a added support for the 2 to 11 GHz range, of which some parts are unlicensed

internationally and other require domestic licenses.

An important aspect of the IEEE 802.16 is that it defines a MAC layer that supports multiple

physical layer (PHY) specifications. This is crucial to allow equipment makers to differentiate

their offerings. Hence WiMAX can be described as a 'framework for the evolution of wireless

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Wi-Fi Technology

broadband' rather than a static implementation of wireless technologies feasible to be

implemented at the current time. The MAC is significantly different from that of Wi-Fi. In Wi-

Fi, the Ethernet uses contention access - all subscriber stations wishing to pass data through an

access point are competing for the AP's attention on a random basis. This can cause distant

nodes from the AP to be repeatedly interrupted by less sensitive, closer nodes, greatly reducing

their throughput. By contrast, the 802.16 MAC is a scheduling MAC where the subscriber

station only has to compete once (for initial entry into the network). After that it is allocated a

time slot by the base station. The time slot can enlarge and constrict, but it remains assigned to

the subscriber station meaning that other subscribers are not supposed to use it but take their

turn. This scheduling algorithm is stable under overload and oversubscription (unlike 802.11). It

is also much more bandwidth efficient. The scheduling algorithm also allows the base station to

control Quality of Service by balancing the assignments among the needs of the subscriber

stations.

HOW DOES IT WORK?

In practical terms, WiMAX would operate similar to Wi-Fi but at higher speeds, over greater

distances and for a greater number of users.

A WiMAX system consists of two parts:

A WiMAX tower, similar in concept to a cell-phone tower - A single WiMAX tower

can provide coverage to a very large area -- as big as 3,000 square miles.

A WiMAX receiver - The receiver and antenna could be a small box or PCMCIA card,

or they could be built into a laptop the way Wi-Fi access is today.

A WiMAX tower station can connect directly to the Internet using a high-bandwidth wired

connection. It can also connect to another WiMAX tower using a line-of-sight, microwave link.

This connection to a second tower (often referred to as a backhaul), along with the ability of a

single tower to cover up to 3,000 square miles, is what allows WiMAX to provide coverage to

remote rural areas. WiMax antennae would be connected to a service provider's "head end" via

either a light fiber optics cable or a directional microwave link.Through the stronger line-of-

sight antennas, the WiMAX transmitting station would send data to WiMAX-enabled computers

or routers set up within the transmitter's 30-mile radius. This is what allows WiMAX to achieve

its maximum range.

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ADVANTAGES OF WI-MAX:

1. It aims to provide connectivity to network endpoints without direct line of sight in some

circumstances.

2. The technology also provides shared data rates up to 70 Mbit/s, which, according to

WiMAX proponents, is enough bandwidth to simultaneously support more than 60

businesses and well over a thousand homes at 1Mbit/s DSL-level connectivity.

3. The fastest Wi-Fi connection can transmit up to 54 megabits per second under optimal

conditions.

4. It provides increased bandwidth and stronger encryption

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