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T101 Networks

T101 Networks. 4 – Wireless Networks. Exam. The first exam for T101 is on Thursday 19 th August at 2:30pm Rooms 6-1-14 and 1-1-25 short-answer questions Ethernet media, Ethernet operation, hubs, switches and wireless worth 30% towards the final mark. Lesson Objectives.

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T101 Networks

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  1. T101 Networks 4 – Wireless Networks

  2. Exam • The first exam for T101 is on Thursday 19th August at 2:30pm • Rooms 6-1-14 and 1-1-25 • short-answer questions • Ethernet media, Ethernet operation, hubs, switches and wireless • worth 30% towards the final mark

  3. Lesson Objectives • to describe Bluetooth (IEEE 802.15) • to describe IEEE 802.11 (WiFi) • to describe WiMedia • to describe IEEE 802.16 (WiMAX)

  4. Warning! • when looking at wireless networks there is an almost inexhaustible supply of terminology and TLAs • WAP, WEP, WPA2, DCF, RTS/CTS, 802.11g, DSSS, CCK, OFDM, RC4, AES, WPS, TKIP, CCMP, MBWA, WDS, GPRS, CDMA, association, adaptive rate selection etc…

  5. Wireless Technologies • Wireless is a growth industry • Wireless USB, Wibree, 802.15, ZigBee, Bluetooth, WiMedia, UWB…

  6. WLAN – IEEE and WiFi • Ethernet is IEEE 802.3 • 802.3i is 10Base-T • 802.3u is 100Base-TX and 100Base-FX • 802.3ab is 1000Base-T • 802.3an is 10GBase-T • 802.3 is the standard and the letters are amendments (updates) to the standard • 802.11 is the Wireless LAN standard

  7. Properties of Radio • according to the IEEE, radio devices have • neither an absolute nor readily observable boundary outside of which stations are known to be unable to receive network frames • no protection from outside signals • dynamic topologies • no guarantee of full connectivity so some stations may not be able to hear other stations – the “hidden-node” problem [see the lesson notes] • time-varying and asymmetric properties

  8. Radio Propagation • the dark red object is a metal desk • there is a door in this room

  9. WiFi • IEEE 802.11 is the wireless LAN standard • just like Ethernet, it is undergoing almost constant amendment • 802.11b is an early 5.5 and 11Mbps standard • 802.11g is a 54Mbps standard that is compatible with 802.11b • 802.11n was published in October 2009 and offers > 74Mbps • currently available consumer devices are typically IEEE 802.11g with some more expensive 802.11n available • IEEE decided to call 802.11 “WiFi” • 802.11 uses CSMA/CA as the medium access method • because of the hidden-node problem, CSMA/CD won’t work • CSMA/CA has a bigger overhead than CSMA/CD, so the data throughput is reduced

  10. Security • the really big problem with wireless networking is security • unlike wired LANs, anyone with a wireless NIC who is in range of a wireless access point can join the network… • …unless some form of security is used to prevent unauthorised access • WEP is the first attempt at 802.11 security

  11. WEP • Wired Equivalent Privacy was intended to provide privacy equivalent to a wired LAN • in the words of the IEEE… • it is reasonably strong • it is efficient, meaning that it is not CPU intensive • it may be exportable from the US • at the time of writing WEP this effectively meant that it was a very weak encryption system and the IEEE were very aware of this • it is optional

  12. WEP • but perhaps the worst thing about WEP from a company perspective is that there is no key (or password) management • all stations typically have the same key which has to be entered manually in each station by the administrator • what happens when an employee leaves a company? • vulnerable to a nosey colleague snooping your traffic

  13. WEP • the IEEE knew that WEP was a weak encryption system but wireless has to have some form of security • WEP is easy to break and offers no practical security; it is not suitable for use by the home user or by a company – something else is needed • fortunately the IEEE designed 802.11 to be able to use other security systems without too much modification • they also started work on amendment 802.11i which would provide strong security when the political climate changed

  14. WPA and WPA2 • IEEE 802.11i (June 2004) is the amendment that provides strong security • Wi-Fi Protected Access is the security system to replace WEP • WPA provides partial compliance with 802.11i • WPA was based on an early draft of 802.11i which implements TKIP; the urgent need for an improvement to WEP forced WPA onto the market early • WPA2 provides full compliance with 802.11i, uses AES • WPA2 is a must if you are thinking of buying a wireless device for company use • WPA2 is considered to be secure provided it is setup correctly • WPA2 includes a key management architecture

  15. WPAN – Bluetooth • invented in Sweden • Ericsson is a Swedish company • used primarily to connect small devices over a very short distance • mobile phones, video game controllers, laptops, cameras

  16. Bluetooth uses a very small amount of power so it can be used in very small devices (with small batteries) • its range is limited because of the small power • its data transfer rate is between 700kbit/s and about 2Mbit/s • range is usually about 10m

  17. WiMedia • WiMedia could be the next big thing… • likely to become the standard WPAN

  18. UWB and WiMedia • Ultra-wideband is a newer technology used for small devices over a short range • the UWB standard is called WiMedia • WiMedia will eventually replace Bluetooth, although the Bluetooth name may remain for marketing reasons

  19. UWB

  20. WiMedia + 802.11

  21. Range, Bandwidth and Capacity

  22. WWAN and WiMAX • IEEE 802.16 is the emerging long range wireless standard • its use is probably going to be confined to network providers • used for point-to-point connections but also designed to cater for broadband last-mile access to the Internet • can deliver up to 70Mbps up to a distance of 48km, but not at the same time • as with all wireless standards, throughput decreases with range

  23. WiMAX Competitors

  24. Summary • Bluetooth is a wireless PAN for small, low power devices • Wi-Fi (IEEE 802.11) is the current wireless LAN standard • Wi-Fi needs to be secured and… • WEP is easily broken • WPA is a minimum requirement for home use • WPA2 is better for organisations • WiMAX could be the next solution to the last-mile problem

  25. Further Reading • 802.11b and 802.11g inter-operation and why you do not get 54Mbps • http://www.proxim.com/learn/library/whitepapers/maximizing_80211g_investment.pdf • 802.11 in general • http://en.wikipedia.org/wiki/802.11 • Problems with WEP • http://en.wikipedia.org/wiki/Wired_Equivalent_Privacy • Problems with exporting cryptography • http://en.wikipedia.org/wiki/Export_of_cryptography • this article also explains why WEP has only 40 bit keys

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