Chapter 9

Chapter 9Chapter 9

Wireless networkWireless network

Wireless NetworkWireless Network

In wireless network, data are carried by In wireless network, data are carried by electrical waveelectrical wave (e.g., (e.g., radio waveradio wave) from ) from one node to another. one node to another.

There is There is no physical cable/wireno physical cable/wire connecting one computer to anotherconnecting one computer to another

Wired (Cabled) Network versus Wireless Wired (Cabled) Network versus Wireless NetworkNetwork

Advantages Advantages of Wireless Network over Wired (Cabled) of Wireless Network over Wired (Cabled) NetworkNetwork– Mobility:Mobility: Users can roam around the network without being Users can roam around the network without being

disconnecteddisconnected– Installation speed and cost:Installation speed and cost: Building wireless medium to large Building wireless medium to large

network is usually faster and cheaper than building wired (cabled) network is usually faster and cheaper than building wired (cabled) medium to large network because medium to large network because there is no need to pull cable there is no need to pull cable through walls and ceilingsthrough walls and ceilings

– Reach of network:Reach of network: Wireless network can be extended to places Wireless network can be extended to places where wire/cable cannot reachwhere wire/cable cannot reach

– Flexibility/scalability:Flexibility/scalability: New computers can be added easily without New computers can be added easily without having to pull cable into the computers having to pull cable into the computers

Disadvantages Disadvantages of Wireless Network compared to Wired of Wireless Network compared to Wired NetworkNetwork– SpeedSpeed: In general, wireless network technology is slower than : In general, wireless network technology is slower than

wired network technologywired network technology– SecuritySecurity: In general, wireless network is less secured than wired : In general, wireless network is less secured than wired

networknetwork

Basic Components of Wireless NetworkBasic Components of Wireless Network

Wireless Network HardwareWireless Network Hardware

Wireless NICWireless NIC (e.g., wireless Ethernet NIC or (e.g., wireless Ethernet NIC or Bluetooth NIC) must be installed in each Bluetooth NIC) must be installed in each computercomputer

Major functions of wireless NIC:Major functions of wireless NIC:– Sender NIC: Sender NIC:

Take data from Layer 3 (Network Layer)Take data from Layer 3 (Network Layer) Encapsulate the data into frameEncapsulate the data into frame Load the frame to electrical waveLoad the frame to electrical wave Transmit the electrical waveTransmit the electrical wave

– Receiver NIC performs the reverse activitiesReceiver NIC performs the reverse activities

Wireless NIC comes in various forms (e.g., Wireless NIC comes in various forms (e.g., expansion board, PCMCIA, USB, built-in)expansion board, PCMCIA, USB, built-in)

Wireless Network HardwareWireless Network Hardware

Wireless Access PointWireless Access Point (WAP/Access (WAP/Access Point/AP/Universal Access Point/UAP)Point/AP/Universal Access Point/UAP)

– Central “wiring” device Central “wiring” device to connect wireless to connect wireless nodes to wireless/wired networknodes to wireless/wired network

– If a network uses WAP, all computers must If a network uses WAP, all computers must communicate via the WAPcommunicate via the WAP

Wireless Network ModeWireless Network Mode

Ad-HocAd-Hoc Mode (Peer-to-Peer Mode) Mode (Peer-to-Peer Mode)– Each wireless node can communicate Each wireless node can communicate directlydirectly with each of the other with each of the other

nodes in the network (nodes in the network (without Wireless Access Pointwithout Wireless Access Point))– MeshMesh network topology network topology– IBSS (Independent Basic Service Set)IBSS (Independent Basic Service Set): a group of nodes : a group of nodes

communicating in ad-hoc modecommunicating in ad-hoc mode

InfrastructureInfrastructure Mode Mode– All wireless node communicate to one another All wireless node communicate to one another via Wireless Access via Wireless Access

PointPoint– StarStar network topology network topology– BSS (Basic Service Set)BSS (Basic Service Set): a group of nodes communicating in : a group of nodes communicating in

infrastructure mode. infrastructure mode. An BSS has one wireless access pointAn BSS has one wireless access point

– EBSS (Extended Basic Service Set)EBSS (Extended Basic Service Set): two or more BSS that can : two or more BSS that can communicate to one anothercommunicate to one another An EBSS contains two or more wireless access pointsAn EBSS contains two or more wireless access points

Ad-Hoc versus Infrastructure Ad-Hoc versus Infrastructure ModeMode

Ad-Hoc Mode (IBSS)

Infrastructure Mode (BSS)

Infrastructure Mode: BSS versus Infrastructure Mode: BSS versus EBSSEBSS

BSS EBSS

Wireless Network SecurityWireless Network Security

Three basic wireless network security Three basic wireless network security methods: methods:

– SSIDSSID (Service Set IDentification)(Service Set IDentification)

– MACMAC Address FilteringAddress Filtering

– EncryptionEncryption

Wireless Network SecurityWireless Network Security

SSID SSID (Service Set IDentifier)(Service Set IDentifier) ( (Network NameNetwork Name): ):

– A A 32-alphanumeric character 32-alphanumeric character given to a networkgiven to a network Valid SSID: USER, 1234, ThisIsAValidSSIDValid SSID: USER, 1234, ThisIsAValidSSID Invalid SSID: ThisIsAnInvalidSSIDDoYouKnowTheReasonInvalid SSID: ThisIsAnInvalidSSIDDoYouKnowTheReason

– All nodes and the Wireless Access PoAll nodes and the Wireless Access Pointint must must have have the same SSIDthe same SSID to be able to communicate in to be able to communicate in infrastructure modeinfrastructure mode

– SSID is defined by usingSSID is defined by using Configuration utilityConfiguration utility software software for the for the Wireless Access PointWireless Access Point and the and the NICNIC

Wireless Network SecurityWireless Network Security SSID (Service Set IDentifier)SSID (Service Set IDentifier) ( (Network NameNetwork Name): ):

– SSID Broadcast/BeaconingSSID Broadcast/Beaconing: : WAP can be configured to continuously broadcast its SSID. WAP can be configured to continuously broadcast its SSID.

As a result, every wireless device that come within the range As a result, every wireless device that come within the range of the WAP (of the WAP (hotspothotspot) can connect to the WAP) can connect to the WAP

To improve security, turn off the SSID broadcast/beaconTo improve security, turn off the SSID broadcast/beacon

– Problem with SSID:Problem with SSID: Even if you turn off the “SSID Even if you turn off the “SSID

broadcast/beacon” of the WAP, SSID can be broadcast/beacon” of the WAP, SSID can be easily “sniffed” easily “sniffed” (i.e., by using a wireless “packet (i.e., by using a wireless “packet sniffer” a cracker is able to listen in on network traffic and sniffer” a cracker is able to listen in on network traffic and identify the SSID)identify the SSID)

Wireless Network SecurityWireless Network Security

MAC Address FilteringMAC Address Filtering::– To To allowallow ( (preventprevent) certain computers to access a ) certain computers to access a

wireless networkwireless network

– Wireless Access Point can be configured to:Wireless Access Point can be configured to: AllowAllow communication with certain MAC Addresses communication with certain MAC Addresses ONLYONLY DenyDeny communication with certain MAC Addresses communication with certain MAC Addresses

– MAC Address Filtering is set by usingMAC Address Filtering is set by using Configuration Configuration utilityutility software for the software for the Wireless Access PointWireless Access Point

– Problem with MAC address filtering:Problem with MAC address filtering: MAC address can be easily “sniffed” MAC address can be easily “sniffed” (i.e., by using a (i.e., by using a

wireless “packet sniffer” a cracker is able to listen in on wireless “packet sniffer” a cracker is able to listen in on network traffic and identify the MAC addresses of computers network traffic and identify the MAC addresses of computers connected to the network)connected to the network)

Wireless Network SecurityWireless Network Security

EncryptionEncryption::– Two major encryption technologies for wireless Two major encryption technologies for wireless

network:network: WEP (Wired Equivalent Privacy): WEP (Wired Equivalent Privacy): older, older,

less safe (less safe (a single key for all users and a single key for all users and sessionssessions))

WPA (Wireless Protected Access): WPA (Wireless Protected Access): newer, newer, more safe (more safe (different key for different users different key for different users and sessionsand sessions))

– Encryption technology is defined by usingEncryption technology is defined by using Configuration utilityConfiguration utility software for the software for the Wireless Access PointWireless Access Point and the and the NICNIC

Web-basedWeb-based WAP Configuration WAP Configuration UtilityUtility

Wireless network SecurityWireless network Security

Configuring a Wireless NIC:Configuring a Wireless NIC:– http://www.usr.com/support/5450/54xx-ug/http://www.usr.com/support/5450/54xx-ug/

four.htmlfour.html

Wi-Fi Protected SetupWi-Fi Protected Setup ( (WPSWPS) ) – A standard for easy and secure establishment of a A standard for easy and secure establishment of a

wireless home network, created by the Wi-Fi Alliance wireless home network, created by the Wi-Fi Alliance and officially launched on January 8, 2007.and officially launched on January 8, 2007.

– The goal of the WPS protocol is to simplify the The goal of the WPS protocol is to simplify the process of configuring security on wireless networks, process of configuring security on wireless networks, and so it was first named ‘Wi-Fi Simple Config’.and so it was first named ‘Wi-Fi Simple Config’.

– http://kb.netgear.com/app/answers/detail/a_id/96http://kb.netgear.com/app/answers/detail/a_id/96

– http://www.youtube.com/watch?v=XDxHXuhttp://www.youtube.com/watch?v=XDxHXu5jxWQ5jxWQ

Wireless network SpeedWireless network Speed

Wireless network Wireless network speedspeed depends on:depends on:

– The wireless network technology The wireless network technology standardstandard

– The The distancedistance between sender and receiver, or between sender and receiver, or between a node and a Wireless Access Point between a node and a Wireless Access Point

– InterferenceInterference from other wireless devices or from other wireless devices or electronic devices (e.g., wireless phone)electronic devices (e.g., wireless phone)

– The The presence of solid objectpresence of solid object (especially metal (especially metal object, electronic appliance) between the sender and object, electronic appliance) between the sender and receiver, or between a node and a Wireless Access receiver, or between a node and a Wireless Access PointPoint

Wireless Network Range Wireless Network Range (i.e., maximum distance between sender and (i.e., maximum distance between sender and

receiver, or a node and a Wireless Access Point )receiver, or a node and a Wireless Access Point ) Wireless network Wireless network rangerange depends on:depends on:

– The wireless network technology The wireless network technology standardstandard– InterferenceInterference from other wireless devices or electronic from other wireless devices or electronic

devicesdevices– The The presence of solid objectpresence of solid object (especially metal object, (especially metal object,

electronic appliance) between the sender and receiver, or electronic appliance) between the sender and receiver, or between a node and a Wireless Access Pointbetween a node and a Wireless Access Point

To increase the wireless network range:To increase the wireless network range:– Using Using “signal booster”“signal booster”– Using Using Wireless Access Point Wireless Access Point (i.e., instead of using ad-hoc (i.e., instead of using ad-hoc

mode, use infrastructure mode)mode, use infrastructure mode)– Using Using MULTIPLEMULTIPLE Wireless Access Points Wireless Access Points (What is (What is Power Power

over Ethernet (PoE)over Ethernet (PoE)?)?)

Extending Wireless NetworkExtending Wireless Network

BSS EBSS

Wireless Network Access Method Wireless Network Access Method (CSMA/C(CSMA/CAA))

CSMA/CACSMA/CA (Carrier Sense Media Access (Carrier Sense Media Access with Collision Avoidance):with Collision Avoidance):

– Using a stricter network access method to Using a stricter network access method to avoid collision (minimize the probability avoid collision (minimize the probability of collision as much as possible) of collision as much as possible)

Wireless Network StandardsWireless Network Standards

Two major wireless network technology Two major wireless network technology standards:standards:

– IEEE 802.11IEEE 802.11 Wireless Fidelity (Wi-Fi)Wireless Fidelity (Wi-Fi)

– IEEE 802.15IEEE 802.15 BluetoothBluetooth

Wireless Network StandardsWireless Network Standards

IEEE 802.11IEEE 802.11

– Wi-FiWi-Fi

Most popularMost popular

All Wi-Fi standards (802.11, a, b, g) have All Wi-Fi standards (802.11, a, b, g) have the following features:the following features:

– Communication mode: supporting Communication mode: supporting Ad-hoc and Ad-hoc and InfrastructureInfrastructure

– SSIDSSID– Supporting Supporting WEPWEP and/or and/or WPAWPA

Wireless Network StandardsWireless Network Standards Wi-Fi:Wi-Fi:

– Includes:Includes:

802.11802.11– The oldestThe oldest– Maximum throughput: Maximum throughput: 2 Mbps2 Mbps– More interference from other electronic devices (Why? More interference from other electronic devices (Why?

2.4 GHz frequency range 2.4 GHz frequency range is used by a lot of other is used by a lot of other electronic devices)electronic devices)

– Maximum distance between sender and receiver (node Maximum distance between sender and receiver (node and WAP): and WAP): 150 feet150 feet

802.11 b802.11 b– Maximum throughput: Maximum throughput: 11 Mbps11 Mbps– More interference from other electronic devices (Why? More interference from other electronic devices (Why?

2.4 GHz frequency range 2.4 GHz frequency range is used by a lot of other is used by a lot of other electronic devices)electronic devices)

– Maximum distance between sender and receiver (node Maximum distance between sender and receiver (node and WAP): and WAP): 300 feet300 feet

Wireless Network StandardsWireless Network Standards

Wi-Fi:Wi-Fi: 802.11 a802.11 a

– Developed Developed after (newer than)after (newer than) 802.11 b 802.11 b– Maximum throughput: Maximum throughput: 54 Mbps54 Mbps– Less interference from other electronic devices (Why? Less interference from other electronic devices (Why? 5 GHz 5 GHz

frequency frequency range is range is NOTNOT used by many electronic devices) used by many electronic devices) Problem: NOT compatible with the “popular” 802.11 bProblem: NOT compatible with the “popular” 802.11 b

– Maximum distance between sender and receiver (node and Maximum distance between sender and receiver (node and WAP): WAP): 150 feet150 feet

802.11 g802.11 g– Maximum throughput: Maximum throughput: 54 Mbps54 Mbps– More interference from other electronic devices (Why? More interference from other electronic devices (Why? 2.4 2.4

GHz frequency rangeGHz frequency range is used by a lot of other electronic is used by a lot of other electronic devices)devices)

– Maximum distance between sender and receiver (node and Maximum distance between sender and receiver (node and WAP): WAP): 300 feet300 feet

Wireless Network Standards: BluetoothWireless Network Standards: Bluetooth

Bluetooth:Bluetooth:– Major application: Major application: short-range network short-range network (e.g., (e.g.,

connecting a PDA device to a computer)/small connecting a PDA device to a computer)/small network (network (PAN: Personal Area Network = Pico/PiconetPAN: Personal Area Network = Pico/Piconet))

– Maximum throughput: Maximum throughput: 4 Mbps4 Mbps

– Maximum distance between sender and receiver: Maximum distance between sender and receiver: 33 33 feet (10 meters)feet (10 meters)

– Supporting proprietary 128-bit encryption algorithmSupporting proprietary 128-bit encryption algorithm

– 2.4 GHz2.4 GHz

Assignment 3Assignment 3Due on Monday, October 5, 2009Due on Monday, October 5, 2009

Problem 1: Search the WWW about:Problem 1: Search the WWW about:– 802.11 N802.11 N

What frequency does this technology use?What frequency does this technology use? What is its maximum data transmission speed?What is its maximum data transmission speed? What is its maximum range?What is its maximum range?

– Wi-MaxWi-Max Which IEEE sub-committee is responsible in the development and Which IEEE sub-committee is responsible in the development and

promotion of this technology?promotion of this technology? What are the major differences between this technology and the What are the major differences between this technology and the

Wi-Fi?Wi-Fi? What type of network usually uses this technology? LAN, MAN, or What type of network usually uses this technology? LAN, MAN, or

WANWAN– PassphrasePassphrase

WPA uses passphrase. What is passphrase in the context of WPA uses passphrase. What is passphrase in the context of wireless network security? What is the function of passphrase in wireless network security? What is the function of passphrase in the context of wireless network security?the context of wireless network security?

Assignment 3Assignment 3Due on Monday, October 5, 2009Due on Monday, October 5, 2009

Problem 2: Watch these two videos and submit a report:Problem 2: Watch these two videos and submit a report:

– Video 1: http://www.youtube.com/watch?Video 1: http://www.youtube.com/watch?v=yBP9ZOpRLWMv=yBP9ZOpRLWM

– Video 2: http://www.youtube.com/watch?Video 2: http://www.youtube.com/watch?v=9UFh0W_Z3kI&feature=PlayList&p=045B8541438D01v=9UFh0W_Z3kI&feature=PlayList&p=045B8541438D01D0&playnext=1&index=3D0&playnext=1&index=3

– Based on the information provided in those two videos:Based on the information provided in those two videos: What are the basic steps to create a wireless network?What are the basic steps to create a wireless network? What are the basic configurations that must be done to connect a What are the basic configurations that must be done to connect a

computer to a wireless network?computer to a wireless network?

Identify all of the wireless router features that should be used to Identify all of the wireless router features that should be used to make your wireless network more secure, and write a tutorial that make your wireless network more secure, and write a tutorial that specifies all of the steps to set up each of the feature that you specifies all of the steps to set up each of the feature that you mentioned abovementioned above

Assignment 3Assignment 3Due on Monday, October 5, 2009Due on Monday, October 5, 2009

How to submit the assignment?How to submit the assignment?– All answers must be typedAll answers must be typed– Submit the print out in the beginning of the class on Submit the print out in the beginning of the class on

Monday, October 5, 2009Monday, October 5, 2009

How to connect to multiple wireless networks?How to connect to multiple wireless networks?

http://technofriends.in/2009/01/07/how-to-http://technofriends.in/2009/01/07/how-to-simultaneously-connect-to-multiple-wireless-simultaneously-connect-to-multiple-wireless-networks-with-one-wlan-card/networks-with-one-wlan-card/

How to connect to a private network and a public How to connect to a private network and a public network (the Internet) at the same time?network (the Internet) at the same time?

Set the security zones for each network adapter. Set the security zones for each network adapter. The local intranet should be set to Private, and the The local intranet should be set to Private, and the

connection to the internet should be set to public. connection to the internet should be set to public. This link will explain the difference and how to check.This link will explain the difference and how to check.

http://technet.microsoft.com/en-us/library/bb878110.ashttp://technet.microsoft.com/en-us/library/bb878110.aspp

Also make sure that only the wireless internet Also make sure that only the wireless internet connection has a default gateway set and the private connection has a default gateway set and the private wired does not. wired does not.

This could cause you to send packages to the internet This could cause you to send packages to the internet to the wrong gateway. to the wrong gateway.

If you have any networks asides the one attached to If you have any networks asides the one attached to the local network you will need to use routing the local network you will need to use routing statements. statements.