COMP2221COMP2221

Networks in OrganisationsNetworks in Organisations

Richard HensonRichard Henson

April 2013April 2013http://www.edimax.com/en/produce_detail.php?pd_id=8&pl1_id=1&pl2_id=44

Week 11 – Wireless LANs and Week 11 – Wireless LANs and WANsWANs

• Objectives:Objectives:Identify different ways of transferring data Identify different ways of transferring data

without a physical mediumwithout a physical mediumExplain each IEEE standard relating to Explain each IEEE standard relating to

Wireless digital communicationsWireless digital communicationsIdentify protocols and security used with Identify protocols and security used with

IEEE 802.11 and broadband standardsIEEE 802.11 and broadband standardsCritically compare Wireless and cable-Critically compare Wireless and cable-

based WAN systems based WAN systems

IEEE 802 StandardsIEEE 802 Standards

• IEEE802 only possible because of OSI modelIEEE802 only possible because of OSI model• IEEE 802.x standards provide software spec for layers 1 and 2IEEE 802.x standards provide software spec for layers 1 and 2

• resulted from IEEE Feb 80 meetingresulted from IEEE Feb 80 meeting

• Software implementation of relevant standard Software implementation of relevant standard built into network interface card ROMbuilt into network interface card ROM

separate specifications:separate specifications:• OSI layer 1 = PHYOSI layer 1 = PHY• OSI layer 2 = MACOSI layer 2 = MAC

• Wireless standards arrived laterWireless standards arrived later started with 802.11 – now known as WiFistarted with 802.11 – now known as WiFi

Wireless LANs and WANs Wireless LANs and WANs (IEEE 802.11 onwards)(IEEE 802.11 onwards)

• Point-Point connectionsPoint-Point connections one computer with aerial as sender; other one computer with aerial as sender; other

computer with aerial receivescomputer with aerial receives line of sight between aerialsline of sight between aerials anyone else with receiver can pick up the signal….anyone else with receiver can pick up the signal….

Device A

Device B

Man in the middle

easy interception

LAN-based Wireless:LAN-based Wireless:

• One aerial connected to a Server or One aerial connected to a Server or hub, second aerial connected to the PChub, second aerial connected to the PC

• media connection by high frequency media connection by high frequency radio wavesradio waves

Aerial Connected to LAN

e/m waves

ComputerWith wirelessNetwork card

WAN (or MAN) WAN (or MAN) based Wirelessbased Wireless

• Transmission over longer distances Transmission over longer distances between serversbetween servershigh bandwidth & short distances using high bandwidth & short distances using

microwavesmicrowavesmedium bandwidth & longer distances medium bandwidth & longer distances

using radio wavesusing radio waves

Wireless Transmission Wireless Transmission Hardware & SoftwareHardware & Software

• Wireless network cards have a small Wireless network cards have a small aerial for network connection instead of aerial for network connection instead of a RJ45/BNC socketa RJ45/BNC socket

• Hubs can connect to more powerful Hubs can connect to more powerful aerial “hotspots” (WAPs)aerial “hotspots” (WAPs)each can connect to a number of device-each can connect to a number of device-

based wireless cardsbased wireless cards

IEEE 802 Wireless StandardsIEEE 802 Wireless Standards

• Main wireless software standards:Main wireless software standards:IEEE 802.11 – Wi-FiIEEE 802.11 – Wi-FiIEEE 802.15 – Wireless Personal Area IEEE 802.15 – Wireless Personal Area

NetworksNetworksIEEE 802.16 – Broadband Wireless IEEE 802.16 – Broadband Wireless

(WiMAX)(WiMAX)IEEE 802.20 – Mobile Broadband WirelessIEEE 802.20 – Mobile Broadband WirelessIEEE 802.22 - Wireless Regional Area IEEE 802.22 - Wireless Regional Area

NetworksNetworks

IEEE 802.11 Wireless LANsIEEE 802.11 Wireless LANs

• Many sub-standards in use e.g.Many sub-standards in use e.g. 802.11a 6-54 Mb/s data @5GHz802.11a 6-54 Mb/s data @5GHz 802.11b 5.5-11 Mb/s data @2.4GHz802.11b 5.5-11 Mb/s data @2.4GHz 802.11g 24-54Mb/s data @2.4GHz802.11g 24-54Mb/s data @2.4GHz 802.11i 54Mps @2.4GHz with security 802.11i 54Mps @2.4GHz with security

enhancementsenhancements others e.g. 802.11d had flaws in implementationothers e.g. 802.11d had flaws in implementation

• Future?Future? 802.11n uncertain frequency, data transfer could 802.11n uncertain frequency, data transfer could

reach 700 Mb/secreach 700 Mb/sec

Security and IEEE 802.11Security and IEEE 802.11

• IEEE 802 standards specify OSI levels 1 & 2IEEE 802 standards specify OSI levels 1 & 2 naming based on MAC address (easily spoofed)naming based on MAC address (easily spoofed)

• IEEE 802.11 originalIEEE 802.11 original WEP (Wired Equivalent Privacy)WEP (Wired Equivalent Privacy)

security model built-in security model built-in

• encryption key of 10 or 26 hexadecimal digitsencryption key of 10 or 26 hexadecimal digits

• key can be variable but if fixed, easily hacked…key can be variable but if fixed, easily hacked…

• Enhancement to WEP in 802.11i upgradeEnhancement to WEP in 802.11i upgrade invokes higher OSI layers…invokes higher OSI layers…

WPA protocolWPA protocol• Wi-Fi Protected Access (WPA)Wi-Fi Protected Access (WPA)

““quick fix” of WEP weaknessesquick fix” of WEP weaknesses

• Improved data Improved data encryptionencryption through the through the temporal key integrity protocol (TKIP)temporal key integrity protocol (TKIP) scrambles keys using a hashing algorithmscrambles keys using a hashing algorithm adds an integrity-checking feature to ensure adds an integrity-checking feature to ensure

that keys haven't been tampered withthat keys haven't been tampered with

• User User authenticationauthentication through extensible through extensible authentication protocol (EAP) RFC #3748authentication protocol (EAP) RFC #3748 uses more secure public-key encryption systemuses more secure public-key encryption system ensures that only ensures that only authorizedauthorized network users network users

can access the networkcan access the network

Stronger Security from WPA2Stronger Security from WPA2

• WPA comprehensively hacked in 2008WPA comprehensively hacked in 2008http://hothardware.com/News/WiFi-WPA-Encryptio

n-Protocol-Cracked

many networks still use WPA… (!)many networks still use WPA… (!)

• WPA2 introduced using stronger WPA2 introduced using stronger authenticationauthentication CCMP encryption protocol replaces AESCCMP encryption protocol replaces AES can still be hacked if implemented using can still be hacked if implemented using Wi-Fi Wi-Fi

Protected Setup (an alternative authentication Protected Setup (an alternative authentication method)method)

IEEE 802.11 in practiceIEEE 802.11 in practice

• Nodes on an existing cabled-based networkNodes on an existing cabled-based network well tried and tested by IEEE:well tried and tested by IEEE:

• wireless card replaces Ethernet card wireless card replaces Ethernet card • ““wireless access point” plugs into a port on the main hub wireless access point” plugs into a port on the main hub

or a network serveror a network server• linked by high frequency radio waves (2.4/5 GHz)linked by high frequency radio waves (2.4/5 GHz)• bandwidth theoretically up to 55 Mb/sbandwidth theoretically up to 55 Mb/s

• Limitations:Limitations: transmission distancetransmission distance affected by environmental conditionsaffected by environmental conditions cannot penetrate brick walls very easilycannot penetrate brick walls very easily security – many hubs still using WEPsecurity – many hubs still using WEP

Configuration of IEEE 802.11 Configuration of IEEE 802.11 Wireless CardsWireless Cards

• Theory good; practice can be messyTheory good; practice can be messy

• cabled network cards can communicate with other cabled network cards can communicate with other cabled network cardscabled network cardswireless network cards CAN communicate with wireless network cards CAN communicate with

“other” nearby networks“other” nearby networksknown as an “ad hoc” wireless networksknown as an “ad hoc” wireless networks

• Widely accepted method:Widely accepted method:use only WAPs to communicate with wireless use only WAPs to communicate with wireless

adapters/cardsadapters/cards

Connectivity and Connectivity and Wireless Access PointsWireless Access Points

• PC with a wireless card likely also to PC with a wireless card likely also to have a cabled network card! have a cabled network card! link to wired network via UTP cablelink to wired network via UTP cable

• If the network is small, ALL devices If the network is small, ALL devices (including each network adapter) can (including each network adapter) can have an IP address in the same subnethave an IP address in the same subnet

IP address allocation issues addressed via IP address allocation issues addressed via DHCPDHCP

Configuration of IEEE 802.11 Configuration of IEEE 802.11 Wireless Access PointsWireless Access Points

• Provide network connectivity to a number of Provide network connectivity to a number of wireless network cards (up to 254 in theory)wireless network cards (up to 254 in theory) correct configuration therefore crucial!correct configuration therefore crucial!

• Both ends of the connection must use the Both ends of the connection must use the same wireless protocol:same wireless protocol: could be 802.11a, b, g or hcould be 802.11a, b, g or h

• Both ends of the connection must have IP Both ends of the connection must have IP addresses in the same subnet rangeaddresses in the same subnet range

Setting up an Access PointSetting up an Access Point

• Use the RJ45 connection to connect the Use the RJ45 connection to connect the access point to a hub or computer on the access point to a hub or computer on the networknetwork

• Run the setup software supplied Run the setup software supplied option to change IP address to match local subnetoption to change IP address to match local subnet choice of mode for the device:choice of mode for the device:

• EITHER “range extender”: existing wireless networkEITHER “range extender”: existing wireless network• OR “access point”OR “access point”• choose the latter and set up should be completechoose the latter and set up should be complete

• Or… the wireless card may be plug-and-playOr… the wireless card may be plug-and-play

IEEE 802.11 IEEE 802.11 & Wireless Routers& Wireless Routers

• The most popular purpose of a router is to The most popular purpose of a router is to connect two networks togetherconnect two networks together

• A wireless router contains a network access A wireless router contains a network access point, but…point, but… external focus is NOT the local networkexternal focus is NOT the local network instead, refers to a public or other external instead, refers to a public or other external

network of some sortnetwork of some sort

• Wireless routers therefore useful for Wireless routers therefore useful for connecting home networks to the Internetconnecting home networks to the Internet

IEEE 802.16 Wireless IEEE 802.16 Wireless Broadband NetworksBroadband Networks

• Providing high bandwidth network or Internet access directly via antenna and high frequency radio waves:802.16.1 Telecommunications and Information

Exchange Between Systems - LAN/MAN Specific Requirements - Air Interface for Fixed Broadband Wireless Access Systems

802.16.2 IEEE Recommended Practice for Coexistence of Fixed Broadband Wireless Access Systems

MobileMobile Phone Networks Phone Networks

• Nationwide, but not InternationalNationwide, but not InternationalUK system quite different from USUK system quite different from USNational networks have interconnectivityNational networks have interconnectivity

• Access Technology: GSM (Global Access Technology: GSM (Global System for Mobile Communications)System for Mobile Communications)mostly used for voice and SMS messagingmostly used for voice and SMS messagingdata users “on the move” tend to use larger data users “on the move” tend to use larger

devicesdevices• PDAs, laptops, smartphonesPDAs, laptops, smartphones

The “cell” systemThe “cell” system• Receivers need to be <35 km from base Receivers need to be <35 km from base

(transmitting) station(transmitting) station

• In practice, network is arranged in In practice, network is arranged in “cells”“cells”signals degrade somewhat at beyond 10 signals degrade somewhat at beyond 10

kmkmdiffering frequencies for adjacent cells to differing frequencies for adjacent cells to

stop interferencestop interference• http://www.cellular.co.za/howagsm.htm • http://kbs.cs.tu-berlin.de/~jutta/gsm/js-intro.html

More about GSM (or 2G)More about GSM (or 2G)

• Uses circuit switching Uses circuit switching

• Two connection technologiesTwo connection technologiesfrequency either 900 MHz or 1800 MHzfrequency either 900 MHz or 1800 MHz

• Slow, 9K!Slow, 9K!

• SIM (subscriber identity model) card SIM (subscriber identity model) card implements personal mobility implements personal mobility

Broadband & Broadband & Mobile Phone NetworksMobile Phone Networks

• GPRS (General Packet Radio Service)GPRS (General Packet Radio Service) part of a worldwide strategy to move towards 3G part of a worldwide strategy to move towards 3G

networks and servicesnetworks and services known as “2.5G” known as “2.5G”

• infrastructure not ready for 3Ginfrastructure not ready for 3G• uses slotted ALOHA access methoduses slotted ALOHA access method• interim solution whilst SIM evolves to IPv4 (then IPv6)interim solution whilst SIM evolves to IPv4 (then IPv6)

reality…reality…• IP connectivity and "always on" service access for the IP connectivity and "always on" service access for the

user quite a step forward…user quite a step forward… but a potential security hazard!but a potential security hazard!

• customers billed according to data sent, not time onlinecustomers billed according to data sent, not time online

More about GPRSMore about GPRS

• Moderate speed data transfer, using Moderate speed data transfer, using unused channels in the GSM systemunused channels in the GSM system

• Originally thought to extend GPRS to Originally thought to extend GPRS to cover other mobile standardscover other mobile standardsinstead those networks are being instead those networks are being

converted to use the GSM standardconverted to use the GSM standardGSM therefore the only kind of network GSM therefore the only kind of network

where GPRS is in usewhere GPRS is in use

Mobile Evolution to 3GMobile Evolution to 3G

• UMTS (Universal Mobile Telecommunications UMTS (Universal Mobile Telecommunications System) popular with mobile network System) popular with mobile network providersproviders 2.2 GHz waveband2.2 GHz waveband

• 1.9 GHz upload1.9 GHz upload• 2.1 GHz download2.1 GHz download

up to 14 Mb/s theoretical bandwidthup to 14 Mb/s theoretical bandwidth provision for video as well as soundprovision for video as well as sound

• Initial slow take up by consumersInitial slow take up by consumers network coverage initially poor… now much betternetwork coverage initially poor… now much better

Types of 3G Access?Types of 3G Access?

• Six 3G radio access technologies approved in Six 3G radio access technologies approved in total by ITU:total by ITU: W-CDMA (2100) by far the most popularW-CDMA (2100) by far the most popular

• also marketed as 3GSMalso marketed as 3GSM• 82% share of the digital wireless market and growing!82% share of the digital wireless market and growing!

CDMA2000CDMA2000 WiMAXWiMAX TD-SCDMA/TD-CDMATD-SCDMA/TD-CDMA EDGEEDGE DECTDECT

3G in Practice 3G in Practice (HSDPA and variants)(HSDPA and variants)

• High-Speed Downlink Packet AccessHigh-Speed Downlink Packet Access uses W-CDMAuses W-CDMA 7.2 Mb available, 10 Mb coming, 14.4 Mb possible!7.2 Mb available, 10 Mb coming, 14.4 Mb possible! benefits from all the strengths of the global GSM benefits from all the strengths of the global GSM

eco-systemeco-system• global roamingglobal roaming• InteroperabilityInteroperability• open standardsopen standards• huge economies of scalehuge economies of scale• greater varietygreater variety

• HSUPAHSUPA faster uplink speed - theoretical max 5.76 Mbfaster uplink speed - theoretical max 5.76 Mb

Advantages of 3G?Advantages of 3G?

• Some are still happy with 900 & 1800 MHz Some are still happy with 900 & 1800 MHz GPRS with its limited multimedia facilities!GPRS with its limited multimedia facilities! just want to text & talkjust want to text & talk

• In 2007, UK government wanted to use In 2007, UK government wanted to use 900/1800 MHz900/1800 MHz 900 MHz for casinos & online gambling900 MHz for casinos & online gambling 1800 MHz for security services (e.g. RFID tags)1800 MHz for security services (e.g. RFID tags) former raises money for latter!former raises money for latter! while users stick with GPRS this has not become while users stick with GPRS this has not become

a reality…a reality…

Why 3G?Why 3G?

• Broadband Internet:Broadband Internet: on the move – increasing demandon the move – increasing demand where there is no ADSL – still plenty of rural where there is no ADSL – still plenty of rural

areasareas

• To provide the extra bandwidth for To provide the extra bandwidth for multimedia person-person communicationmultimedia person-person communication

• Most small mobile devices now sufficiently Most small mobile devices now sufficiently powerful & flexible to justify broadband powerful & flexible to justify broadband contentcontent

Why 3G?Why 3G?

• Some networks, in some locations, Some networks, in some locations, now exceed standard ADSL now exceed standard ADSL bandwidth:bandwidth:cost only slightly greater, but added cost only slightly greater, but added

flexibility of not needing a fixed flexibility of not needing a fixed connectionconnection• BT (at last!) has REAL competition…BT (at last!) has REAL competition…

4G4G

• Originated as an ARPAnet projectOriginated as an ARPAnet projectcellnet taken even further…cellnet taken even further…

• IEEE802.16 technologies such as:IEEE802.16 technologies such as:WiMAXWiMAXLTELTE

• Very high bandwidth possible:Very high bandwidth possible:5x 3G (!)5x 3G (!)

Satellites and Satellites and Communication NetworksCommunication Networks

• 100s of satellites currently in orbit100s of satellites currently in orbit

• Diverse range of purposes e.g. :Diverse range of purposes e.g. : weather forecastingweather forecasting

television broadcasttelevision broadcast

amateur radio communicationsamateur radio communications

Internet communicationsInternet communications

GPS (Global Positioning System)GPS (Global Positioning System)

• Could also be used to fill connectivity gaps in Could also be used to fill connectivity gaps in sparsely populated areas…sparsely populated areas…

Wireless WANs via SatelliteWireless WANs via Satellite

• Important featuresImportant featuressender and receiver can be thousands of sender and receiver can be thousands of

miles awaymiles awaysatellite thousands of miles up in orbitsatellite thousands of miles up in orbit

• acts as a reflector for electromagnetic radiationacts as a reflector for electromagnetic radiationpowerful transmission equipment is powerful transmission equipment is

requiredrequiredveryvery accurate pointing of beam required accurate pointing of beam requiredsatellite dish required at receiver endsatellite dish required at receiver end

Different Types of Different Types of Satellite ConnectionSatellite Connection

• Modern satellites can receive and re-Modern satellites can receive and re-transmit thousands of signals transmit thousands of signals simultaneously:simultaneously: High bandwidthHigh bandwidth

• high energy microwaveshigh energy microwaves environmental issuesenvironmental issues special receiving equipmentspecial receiving equipment military onlymilitary only

Medium bandwidthMedium bandwidth• high frequency radio waveshigh frequency radio waves

environmentally safeenvironmentally safe easy to receiveeasy to receive commercially availablecommercially available

““Cable” Broadband NetworksCable” Broadband Networks

• Once three networks:Once three networks: BlueYonder/TeleWest/NTLBlueYonder/TeleWest/NTL

• Taken over by Richard Branston in 2006…Taken over by Richard Branston in 2006… formed VirginMediaformed VirginMedia

• High Broadband down/upload bandwidths High Broadband down/upload bandwidths now available:now available: 20Mb/768Kb and more…20Mb/768Kb and more…

• Problem: coverage patchy Problem: coverage patchy only 55% of UK householdsonly 55% of UK households

ADSLADSL

• Asynchronous Digital Subscriber lineAsynchronous Digital Subscriber line higher speed download than uploadhigher speed download than upload

• BT’s most successful digital network along BT’s most successful digital network along copper public telephone linescopper public telephone lines replaced ISDN which used 144K maxreplaced ISDN which used 144K max

• ADSL limited by distance from BT exchangeADSL limited by distance from BT exchange 4 miles is the limit…4 miles is the limit… many rural areas can’t get ADSLmany rural areas can’t get ADSL

• dependent on standard line (56K max)dependent on standard line (56K max)

ADSL2+ (BT/Pipex)ADSL2+ (BT/Pipex)

• Uses computer technology in BT exchanges Uses computer technology in BT exchanges that can triple bandwidth availablethat can triple bandwidth available makes up to 24 Mb theoretically possiblemakes up to 24 Mb theoretically possible

• Problems:Problems: will take a long time to roll out across the will take a long time to roll out across the

country…country…

customers at the limits of distance from exchange customers at the limits of distance from exchange will still have much less bandwidthwill still have much less bandwidth

Comparison of ADSL with Comparison of ADSL with alternativesalternatives

• Some exchanges STILL not convertedSome exchanges STILL not converted many households not close enough to exchange to many households not close enough to exchange to

receive full bandwidthreceive full bandwidth

• Less technical & much lower “ping” time than Less technical & much lower “ping” time than satellitesatellite

• Slower & more expensive than cableSlower & more expensive than cable

• Price now comparable with broadband mobilePrice now comparable with broadband mobile

• Much cheaper for connecting a LAN than a Much cheaper for connecting a LAN than a dedicated BT line (annual rental £000s)dedicated BT line (annual rental £000s)

IEEE 802.15 IEEE 802.15 Wireless Personal Area Networks

(WPANs)

• Refers to using wireless devices to control Refers to using wireless devices to control devices in the home:devices in the home: 802.15.1 Wireless specifications for “bluetooth” 802.15.1 Wireless specifications for “bluetooth”

connectionsconnections 802.15.2 Recommended Practice for WPANs 802.15.2 Recommended Practice for WPANs

Operating in Unlicensed Frequency BandsOperating in Unlicensed Frequency Bands 802.15.3 Wireless specifications for High Rate 802.15.3 Wireless specifications for High Rate

WPANsWPANs

More about BluetoothMore about Bluetooth

• Designed to allow laptops, PDAs, cell Designed to allow laptops, PDAs, cell phones, and other devices to exchange phones, and other devices to exchange data at close-rangedata at close-range 10 m max.10 m max.

• Quick frequency hopping at 1600 hops Quick frequency hopping at 1600 hops per second in the 2.4 GHz bandper second in the 2.4 GHz band

• Data rate of 721 kbpsData rate of 721 kbps transmitted power very low: 1 mWtransmitted power very low: 1 mW possible replacement for infrared (i/r) and possible replacement for infrared (i/r) and

cablescables