1

EC301 : Computer Network Fundamental

Noted prepared by:Pn. Wan Fazlini Idayu binti Wan

Fakari

Chapter 5: Wireless Technologies

2

CLO 3: you should be able to you should be able to select addressing scheme of TCP/IP in Local Area Network (LAN) properly using network configuration tool. (C4) CLO 4: you should be able to create a simple network connection using Wireless Local Area Network (WLAN) in accordance to IEEE 802.11 protocols. (P7)note: C4 = analysis, P7=origination

• Chapter5 will appear in:-– Lab (4)– Quiz (4)

3

5.1 Wireless Technologies

4

Wireless Technologies Wireless technologies use electromagnetic waves to carry information between

devices. An electromagnetic wave is the same medium that carries radio signals through the air.

The electromagnetic spectrum includes such things as radio and television broadcast bands, visible light, x-rays and gamma-rays. Each of these has a specific range of wavelengths and associated energies as shown in the diagram.

Some types of electromagnetic waves are not suitable for carrying data. Other parts of the spectrum are regulated by governments and licensed to various organizations for specific applications. Certain areas of the spectrum have been set aside to allow public use without the restriction of having to apply for special permits.

The most common wavelengths used for public wireless communications include the Infrared and part of the Radio Frequency (RF) band.

• Wavelength for each electromagnetic wave

Wireless Technologies

5

6

Wireless Technologies

Infrared Band (IR)– Low energy and unable to penetrate walls (line of sight)– Used for PDAs, PCs, wireless mice, keyboards and remote

controls– IrDA (Infrared Direct Access) port used for 1 to 1

connectionsRadio Frequency (RF)– Goes through walls and other obstructions, better range– Different frequencies assigned to different types of

unlicensed devices

Comparison: infrared vs. radio transmission•Infrared

– uses IR diodes, diffuse light, multiple reflections (walls, furniture etc.)

•Advantages– simple, cheap, available in many

mobile devices– no licenses needed– simple shielding possible

•Disadvantages– interference by sunlight, heat

sources etc.– many things shield or absorb IR

light – low bandwidth

•Example– IrDA (Infrared Data Association)

interface available everywhere

•Radio– typically using the license free ISM

band at 2.4 GHz •Advantages

– experience from wireless WAN and mobile phones can be used

– coverage of larger areas possible (radio can penetrate walls, furniture etc.)

•Disadvantages– very limited license free frequency

bands – shielding more difficult,

interference with other electrical devices

•Example– WaveLAN, HIPERLAN, Bluetooth

8

WWAN802.16e-802.20

WMAN802.16/HIPERMAN

WLAN802.11/HIPERLAN

Wireless Technologies• Wireless Body Area Networks• Wireless Personal Area Networks• Wireless Local Area Network• Wireless Metropolitan Area Network• Wireless Wide Area Network

• Varies in terms of transmission range – Up to 1m– from 1m to 10m– From 10 to 500m– From 500 to 20-50 km– Beyond 50km

WPAN802.15

802.21

Wireless Technologies

9

10

WBAN and WPAN

• A WBAN provides the connectivity among various devices of wearable computers whose components are distributed on the body– E.g. microphones, earphones, etc.

• A WPAN connects one-person’s BAN with the environment around it (devices around the person) – Bluetooth is an example of a wireless PAN that allows

devices within close proximity to join together in an ad hoc fashion to exchange information

– Many cell phones have two radio interfaces: one for the cellular network and one for PAN connections

11

WPAN Applications

12

WLAN• A WLAN provides a wider range of connectivity with higher

data rate than that of WPAN and WBAN – Infrastructure mode: requires an AP and provide access to Internet

backbone– Ad hoc mode: peer-to-peer communication

• Typical applications: hot spots, buildings • Requirements of a WLAN

– High capacity– Full connectivity among the attached nodes– Broadcasting capability

• In terms of standardization– In US: IEEE 802.11 and IEEE 802.15 (Bluetooth)– In Europe: HiperLAN II

13

WBAN/WPAN/WLAN Applications

14

WMAN• WMAN provides a broadband and fast access (higher data rate) with even

wider range than that of WLAN• Standards:

– In US: IEEE 802.16– In Europe: HiperACCESS (>11GHz) and HiperMAN (<11 GHz)

• IEEE802.16:– Support multiple services simultaneously with QoS

• IPv4, IPv6, ATM, ETHERNET– Support multiple frequency allocation (2-66GHz) – Point-to-multipoint topology with mesh extension

• BS is connected to public networks• BS serves subscriber stations (building, residence)

– Link adaptation (adaptive coding and modulation)– Support for advanced antenna systems

• WiMAX Forum (Worldwide Interoperability for Microwave Access) – Promotes deployment of BWA (Broad Band Wireless Access) by using a global

standard and certifying interoperability of products and technologies– Support IEEE802.16

15

WMAN Applications

16

WWAN• Wireless wide area networks are wireless networks

that typically cover large areas, such as between neighboring towns and cities, or city and suburb.

• These networks can be used to connect branch offices of business or as a public internet access system.

• The wireless connections between access points are usually point to point microwave links using parabolic dishes on the 2.4 GHz band, rather than omnidirectional antennas used with smaller networks.

• When combined with renewable energy systems such as photo-voltaic solar panels or wind systems they can be stand alone systems.

• In addition, WAN’s also refer to Mobile Data Communications, such as GSM, GPRS and 3G.

17

18

Advantages– Mobility Allows for easy connection of both stationary and

mobile clients.– Flexibility Ability to provide anytime, anywhere

connectivity– Cost Wireless technology is fairly easy and inexpensive to

install. – Scalability Enables networks to be easily expanded,

without the limitations of cabled connections.

Advantages and limitations of the wireless technology

19

– Reduced installation time Installation of a single piece of equipment can provide connectivity for a large number of people.

Advantages and limitations of the wireless technology

20

Limitations– Interference Wireless technology is susceptible to

interference from other devices that produce electromagnetic energies. (Interferensi teknologi Wireless terdedah terhadap gangguan dari peranti lain yang menghasilkan tenaga elektromagnet)

– Wireless provides ease of access. It does this by broadcasting data in a manner that allows anyone the ability to access it.

– Wireless LAN technology does not currently provide the speed or reliability of wired LAN's.

Advantages and limitations of the wireless technology

21

Type of wireless networks– Wireless Personal Area networks (WPAN) This is the

smallest wireless network used to connect various peripheral devices such as mice, keyboards and PDAs to a computer.

– Wireless Local Area networks (WLAN) WLAN is typically used to extend the boundaries of the local wired network (LAN). An Access Point provides a connection between wireless hosts and hosts on an Ethernet wired network.

– Wireless Wide Area networks (WWAN) WWAN networks provide coverage over extremely large areas.

Types of wireless networks and their boundaries

22

Types of wireless networks and their boundaries

23

Wireless networks boundaries

Types of wireless networks and their boundaries

24

SCENARIO

1. Charlene uses the IrDA port to connect her PDA to her laptop to upload files.

2. Natasha calls her friend Carlos on her cell phone.3. Trisha uses her laptop computer at a wireless HotSpot to check

her email. 4. Burt uses a wireless Blue tooth headset to listen to music from his

MP3 player. 5. Jim connects to the wireless network at his school to do research

on a new technology. 6. Ragu uses his cell phone to view a web page on the Internet.

Activity

WPAN WLAN WWANSelect answer for question 1 to 6:-

25

5.2 Wireless LANs

26

Wireless LANs Standards Protocols

IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands.

They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802).

Figure : Wireless Network Devise (WiFi)

• Many different standards have been adopted for wireless networks– IEEE 802.11n is latest standard adopted (except for 802.11y)– Wi-Fi Alliance tests devices from various manufacturers to make sure they operate

together.

Protocol Release Date

RF Freq.

Throughput

Data Rate (Max)

Max Range

Notes & Comments

802.11 1997 2.4 GHz 0.9 Mbps 2 Mbps Undefined Legacy802.11a 1999 5 GHz 23 Mbps 54 Mbps 50m Not compatible with b, g, n

Expensive802.11b 1999 2.4 GHz 4.3 Mbps 11 Mbps 100m First 2.4 GHz Technology

802.11g 2003 2.4 GHz 19 Mbps 54 Mbps 100m Backward compatible with bShares range with b

802.11n 2009* 2.4 & 5 GHz

74 Mbps 248 Mbps 250m Newest Standard

802.11y 2008* 3.7 GHz 23 Mbps 54 Mbps 5000m Newest Standard

Wireless LANs Standards Protocols

28

wireless LANs devices/components

A wireless local area network (WLAN) links two or more devices using some wireless distribution method and usually providing a connection through an access point to the wider internet.

This gives users the mobility to move around within a local coverage area and still be connected to the network.

Most modern WLANs are based on IEEE 802.11 standards, marketed under the Wi-Fi brand name.

29

Wireless LANs Devices

• Wireless Components– Wireless Clients or STAs

(Wireless STAtion)– APs (Access Points) – Wireless Bridges

• Types of Antennas– Omni send all

directions• Used in APs

– Directional send in one direction• Used for longer links

to bridge distances

Wireless LANs Devices/ Components

31

WLANs Form And Service Set Identifier (SSID)

There are Two forms of WLAN Installations: 1. Ad-hoc (IBSS) Equal Peer-to-peer & No AP2. Infrastructure (BSS) STAs communicate through

APs

32

Channels are created by giving each a part of the RF spectrum– Each one can carry on a separate conversation (Think of a

TV)– Can be set manually or automatically

Channels will often overlap frequencies, but conversations cannot overlap

Newer technologies combine channels into a wider one for better bandwidth

Wireless Channels

33

Wireless Channels

34

A WLAN technology designed to make collisions impossible (teknologi WLAN direka untuk mengelakkan pertembungan.)

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA).– Reserves a channel for use by a conversation– No other devices can transmit on that channel

CSMA/CA

35

CSMA/CA Reservation Process– For a Device to use a channel, it asks the AP by using a

Request To Send (RTS) message.– If channel is not in use, AP will send Clear To Send (CTS)

message to all devices in the BSS so they know the channel is being used.

– Data is sent from STA– After conversation is done, an Acknowledgement (ACK) is

transmitted.

CSMA/CA

36

CSMA/CA

37

5.3 Security on a Wireless LANs

38

How To Avoid WLAN Attack

1. Limited access to a WLAN 2. Authentication on a WLAN 3. Encryption on a WLAN 4. Traffic filtering on a WLAN

Bersambung pada 17/9/2012….

Authentication = pengesahan / ketulenanEncryption = penyulitan

39

MAC Address Filtering– MAC address filtering uses the MAC address to identify

which devices are allowed to connect to the wireless network.

– Only devices whose MAC addresses have been prerecorded in the router's database will be allowed to connect.

Wireless LAN Security - Limiting Access

MAC=Media Access Control

• Controls exactly which devices have access to the LAN

• Uses MAC addresses to ID clients authorized to access WLAN.

• Limitations:– MAC addresses for authorized

clients must be input manually.– This makes adding new clients

difficult– MAC Address cloning or

spoofing can allow an unauthorized user to get into the WLAN.

Wireless LAN Security - Limiting Access

• This process requires a client to present credentials in order to use the network.

• Most common is a username and password, but for a wireless network, this is handled differently.

• Because the transaction is wireless and can be “heard” by anyone, the authentication is done before connecting.

• Three Types of Authentication:– Open

• Used for Public Networks• Networks where another method

of authentication is used.– PSK– EAP

Wireless LAN Security - Authentication

• PSK (Pre-Shared Key)– Both client and AP are configured

with a shared key– Password is encrypted by client

using shared key, then sent to AP, where it is decrypted using the same key.

– Doesn’t authenticate AP or User, only one way

• EAP (Extensible Authentication Protocol)– Authentication is 2-way– Client communicates through AP

to (usually) a RADIUS server which has list of authorized users and clients.

– Both user and client must authenticate.

Wireless LAN Security - Authentication

• Use of Wireless Authentication– Authentication can prevent unauthorized users

from accessing WLAN, but data is still transmitted to anyone with a receiver.

– Encryptions methods were developed to encrypt wireless communications to prevent snooping by outsiders.

• Two main encryption methods:– WEP (Wired Equivalency Protocol)– WPA (Wi-FI Protected Access)

Wireless LAN Security – Data Encryption

44

WEP (Wired Equivalency Protocol)– Uses pre-configured 64, 128, or 256 bit keys to encrypt data

before transmission.– WEP keys are just a string of letters or numbers and can also be

automatically generated using a passphrase.– WEP is not a secure protocol and can easily be cracked by a

knowledgeable wireless hacker. WPA (Wi-Fi Protected Access)– Also uses a 64 to 256 encryption key.– WPA doesn’t always use the same key, but generates new,

dynamic keys each time a client connects.– WPA is considered the current standard of encryption for

wireless networks.

Wireless LAN Security – Data Encryption

• Allows control of traffic types sent across WLAN

• Blocks undesirable traffic from entering or leaving network

• Filtered using – MAC Addresses– IP Addresses– Port Numbers

Wireless LAN Security – Traffic filtering

WLAN Security Measures

• Security should be planned and configured before installing into network or ISP

• Basic measures:– Change Defaults for SSID, usernames, and Psswrds– Disable SSID broadcast– MAC Address Filtering

• Advanced Measures– WPA or WEP Encryption– Authentication– Traffic Filtering