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COMP2221 Networks in Organisations

COMP2221 Networks in Organisations. Richard Henson April 2014 http:// www.edimax.com/en/produce_detail.php?pd_id=425&pl1_id=28&pl2_id=138. Week 10 – Wireless LANs and WANs. Objectives: Identify different ways of transferring data without a physical medium

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COMP2221 Networks in Organisations

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  1. COMP2221Networks in Organisations Richard Henson April 2014 http://www.edimax.com/en/produce_detail.php?pd_id=425&pl1_id=28&pl2_id=138

  2. Week 10 – Wireless LANs and WANs • Objectives: • Identify different ways of transferring data without a physical medium • Explain each IEEE standard relating to Wireless digital communications • Identify protocols and security used with IEEE 802.11 and broadband standards • Critically compare Wireless and cable-based WAN systems

  3. IEEE 802 Standards • IEEE802.x happened because of the OSI model • provide software/engineering spec for layers 1 and 2 • resulted from IEEE Feb 80 meeting • Software implementation of relevant standard built into network interface card ROM • separate specifications: • OSI layer 1 = PHY • OSI layer 2 = MAC • Wireless standards arrived later • started with 802.11 – now known as WiFi

  4. Wireless LANs and WANs (IEEE 802.11 onwards) • Point-Point connections • one computer with aerial as sender; other computer with aerial receives • line of sight between aerials • anyone else with receiver can pick up the signal…. Device A Device B easy interception Man in the middle (MOTM)

  5. LAN-based Wireless: • One aerial connected to a Server or hub, second aerial connected to the PC • media connection by high frequency radio waves e/m waves Aerial Connected to LAN Computer With wireless Network card

  6. WAN (or MAN) based Wireless • Transmission over longer distances between servers • high bandwidth & short distances using microwaves • medium bandwidth & longer distances using radio waves

  7. Wireless Transmission Hardware & Software • Wireless network cards have a small aerial for network connection instead of a RJ45/BNC socket • Hubs can connect to more powerful aerial “hotspots” (WAPs) • each can connect to a number of device-based wireless cards

  8. IEEE 802 Wireless Standards • Main wireless software standards: • IEEE 802.11 – Wi-Fi • IEEE 802.15 – Wireless Personal Area Networks • IEEE 802.16 – Broadband Wireless (WiMAX) • IEEE 802.20 – Mobile Broadband Wireless • IEEE 802.22 - Wireless Regional Area Networks

  9. IEEE 802.11 Wireless LANs • Many sub-standards in use e.g. • 802.11a 6-54 Mb/s data @5GHz • 802.11b 5.5-11 Mb/s data @2.4GHz • 802.11g 24-54Mb/s data @2.4GHz • 802.11i 54Mb/s @2.4GHz with security enhancements • 802.11n 54-600Mb/s @2.4/5 MHz & WPA2 security • others e.g. 802.11d had flaws in implementation • Future? • 802.11ac “uncertain” frequency, data transfer could reach a Gigabit/s…

  10. Security and IEEE 802.11 • IEEE 802 standards specify OSI levels 1 & 2 • naming based on MAC address (easily spoofed) • IEEE 802.11 original • WEP (Wired Equivalent Privacy) • security model built-in • encryption key: 10 or 26 hexadecimal digits • key can be variable but if fixed, easily hacked… • Enhancement to WEP in 802.11i upgrade • invokes higher OSI layers…

  11. WPA protocol • Wi-Fi Protected Access (WPA) • “quick fix” of WEP weaknesses • improved data encryption through the temporal key integrity protocol (TKIP) • scrambles keys using a hashing algorithm • adds an integrity-checking feature to ensure that keys haven't been tampered with • user authentication through extensible authentication protocol (EAP) RFC #3748 • uses more secure public-key encryption system • ensures that only authorized network users can access the network

  12. Stronger Security from WPA2 • WPA comprehensively hacked in 2008 • http://hothardware.com/News/WiFi-WPA-Encryption-Protocol-Cracked • many networks still use WPA… (!) • WPA2 introduced using stronger authentication • CCMP encryption protocol replaces AES • can still be hacked if implemented using Wi-Fi Protected Setup (an alternative authentication method)

  13. IEEE 802.11 use in practice • Nodes on an existing cabled-based network • well tried and tested by IEEE: • wireless card replaces Ethernet card • “wireless access point” plugs into a port on the main hub or a network server • linked by high frequency radio waves (2.4/5 GHz) • bandwidth theoretically up to 55 Mb/s • Limitations: • transmission distance • affected by environmental conditions • cannot penetrate brick walls very easily • security – many hubs still using WEP, or WPA

  14. Configuration of IEEE 802.11 Wireless Cards • Cabled network cards can communicate only with other cabled network cards • wireless network cards can in theory communicate with any “other” nearby networks • participating in an “ad hoc” wireless network • Widely accepted method: • use only WAPs to communicate with wireless adapters/cards

  15. Connectivity and Wireless Access Points • PC with wireless card likely also to have a cabled network card! • link to wired network via UTP cable • If the network is small, ALL devices (including each network adapter) can have an IP address in the same subnet • IP address allocation issues addressed via DHCP

  16. Configuration of IEEE 802.11 Wireless Access Points • Provide network connectivity to a number of wireless network cards (up to 254 in theory) • correct configuration therefore crucial! • Both ends of the connection must use the same wireless protocol: • could be 802.11a, b, g or h • Both ends of the connection must have IP addresses in the same subnet range

  17. Setting up an Access Point • Use an RJ45 connection to connect the access point to a hub or computer on the network • Configure using setup software supplied • option to change IP address to match local subnet • choice of mode for the device: • EITHER “range extender”: existing wireless network • OR “access point” • choose the latter and set up should be complete • Or… the wireless card may be plug-and-play

  18. IEEE 802.11 & Wireless Routers • The most popular purpose of a router is to connect two networks together • A wireless router contains a network access point, but… • external focus is NOT the local network • instead, refers to a public or other external network of some sort • Wireless routers therefore useful for connecting home networks to the Internet

  19. IEEE 802.16 Wireless Broadband 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

  20. Mobile Phone Networks • Nationwide, but not International • UK system quite different from US • National networks have interconnectivity • Access Technology: GSM (Global System for Mobile Communications) • mostly used for voice and SMS messaging • connect data users “on the move”: • PDAs, laptops, tablets, smartphones

  21. The “cell”(phone) system • Receivers need to be <35 km from base (transmitting) station • In practice, network is arranged in “cells” • signals degrade somewhat at beyond 10 km • differing frequencies for adjacent cells to stop interference • http://www.cellular.co.za/howagsm.htm • http://kbs.cs.tu-berlin.de/~jutta/gsm/js-intro.html

  22. More about GSM (or 2G) • Uses circuit switching • Two connection technologies • frequency either 900 MHz or 1800 MHz • Slow, 9K! • SIM (subscriber identity model) card implements personal mobility

  23. Broadband & Mobile Phone Networks • GPRS (General Packet Radio Service) • part of a worldwide strategy to move towards 3G networks and services • infrastructure not ready for 3G • uses slotted ALOHA access method • interim solution whilst SIM evolved to IPv4 (then IPv6?) • reality… • IP connectivity and "always on" service access for the user quite a step forward… • but a potential security hazard! • customers billed according to data sent, not time online

  24. More about GPRS • Moderate speed data transfer • unused channels in the GSM system • Other mobile standards converted to use the GSM standard • GSM therefore the only kind of network where GPRS is in use

  25. Mobile Evolution to 3G • UMTS (Universal Mobile Telecommunications System) popular with mobile network providers • 2.2 GHz waveband • 1.9 GHz upload • 2.1 GHz download • up to 14 Mb/s theoretical bandwidth • provision for video as well as sound • Initial slow take up by consumers • network coverage initially poor… now much better

  26. Types of 3G Access? • Six 3G radio access technologies approved by ITU (remember them?): • W-CDMA (2100) became (by far) the most popular • also marketed as 3GSM • very large share of the digital wireless market… • Others: CDMA2000, TD-SCDMA/TD-CDMA, EDGE, DECT, WiMAX,

  27. 3G in Practice (HSDPA and variants) • High-Speed Downlink Packet Access • uses W-CDMA • 7.2 Mb widely available, 14.4 Mb possible! • benefits from all the strengths of global GSM • global roaming • Interoperability • open standards • huge economies of scale • greater variety • HSUPA • faster uplink speed: theoretical max 5.76 Mb

  28. Advantages of 3G? • Some are still use, and happy with 900 & 1800 MHz GPRS • limited multimedia facilities! • but just want to text & talk • In 2007, UK government wanted to use 900/1800 MHz • 900 MHz for casinos & online gambling • 1800 MHz for security services (e.g. RFID tags) • former raises money for latter! • while users stick with GPRS this has not become a reality…

  29. Why the push to 3G (and beyond)? • Need for broadband Internet speeds: • on the move… • where there is no ADSL – still plenty of rural areas more than 4 miles from substation • to provide the extra bandwidth for multimedia person-person communication • Small mobile devices became sufficiently powerful & flexible to justify (and need) broadband content

  30. Mobile v ADSL? • Some mobile networks, in some locations, offer better bandwidth than standard ADSL bandwidth: • cost only slightly greater, but added flexibility of not needing a fixed connection • but bandwidth fluctuates… • BT (at last!) has REAL competition…

  31. 4G • Originated as an ARPAnet project • cellnet taken a stage further… • Use IEEE802.16 technologies such as: • WiMAX • LTE • Very high bandwidth possible: • 5x 3G (!)

  32. Satellites and Communication Networks • 100s of satellites currently in orbit • Diverse range of purposes e.g. : • weather forecasting • television broadcast • amateur radio communications • Internet communications • GPS (Global Positioning System) • Could also be used to fill connectivity gaps in sparsely populated areas…

  33. Wireless WANs via Satellite? • Important features • sender and receiver can be thousands of miles away • satellite thousands of miles up in orbit • acts as a reflector for electromagnetic radiation • powerful transmission equipment is required • very accurate pointing of beam required • satellite dish required at receiver end

  34. Different Types of Satellite Connection • Modern satellites can receive and re-transmit thousands of signals simultaneously: • High bandwidth • high energy microwaves • environmental issues • special receiving equipment • military only • Medium bandwidth • high frequency radio waves • environmentally safe • easy to receive • commercially available

  35. “Cable” Broadband Networks • Once three networks: • BlueYonder/TeleWest/NTL • Taken over by Richard Branston in 2006… • formed VirginMedia(soon part of Sky?) • High Broadband down/upload bandwidths now available: • 20Mb/768Kb and more… • Problem: coverage patchy • only 55% of UK households

  36. ADSL • Asynchronous Digital Subscriber line • higher speed download than upload • BT’s most successful digital network along copper public telephone lines • replaced ISDN which used 144K max • ADSL limited by distance from BT exchange • 4 miles is the limit… • many rural areas can’t get ADSL • dependent on standard line (56K max)

  37. ADSL2+ (BT/Pipex) • Uses computer technology in BT exchanges that can triple bandwidth available • makes up to 24 Mb theoretically possible • Problems: • will take a long time to roll out across the country… • customers at the limits of distance from exchange will still have much less bandwidth • Answer: use fibreoptic cables • (expensive, expensive to lay)

  38. Comparison of ADSL with alternatives • Some exchanges STILL not converted • many households not close enough to exchange to receive full bandwidth • Less technical & much lower “ping” time than satellite • Slower & more expensive than cable • Price comparable with broadband mobile • Much cheaper for connecting a LAN than a dedicated BT line (annual rental £000s)

  39. IEEE 802.15 Wireless Personal Area Networks (WPANs) • Using wireless devices to control devices in the home • now extended to become “Internet of Things”: • 802.15.1 Wireless specifications for “bluetooth” connections • Also, 802.15.2 Recommended Practice for WPANs Operating in Unlicensed Frequency Bands • And 802.15.3 Wireless specifications for High Rate WPANs

  40. More about Bluetooth • Designed to allow laptops, PDAs, cell phones, and other devices to exchange data at close-range • 10 m max. • Quick frequency hopping at 1600 hops per second in the 2.4 GHz band • Data rate of 721 kbps • transmitted power very low: 1 mW • possible replacement for infrared (i/r) and cables

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