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EC301 : Computer Network Fundamental
Noted prepared by:Pn. Wan Fazlini Idayu binti Wan
Fakari
Chapter 5: Wireless Technologies
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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)
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5.1 Wireless Technologies
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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
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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
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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
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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
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WPAN Applications
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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
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WBAN/WPAN/WLAN Applications
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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
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WMAN Applications
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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.
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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
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– 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
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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
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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
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Types of wireless networks and their boundaries
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Wireless networks boundaries
Types of wireless networks and their boundaries
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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:-
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5.2 Wireless LANs
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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
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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.
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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
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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
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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
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Wireless Channels
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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
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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
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CSMA/CA
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5.3 Security on a Wireless LANs
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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
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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
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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
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