1 / 35

Unit – II Wireless LAN’s (IEEE 802.11x)

Unit – II Wireless LAN’s (IEEE 802.11x). Introduction to IEEE 802.11x Technologies Evolution of Wireless LAN’s IEEE 802.11 Design Issues IEEE 802.11 Services – Overview IEEE 802.11 MAC Layer Operations IEEE 802.11a/b/g – Higher-Rate Standards IEEE 802.11 – Wireless LAN Security

carmengoodman
Télécharger la présentation

Unit – II Wireless LAN’s (IEEE 802.11x)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Unit – II Wireless LAN’s (IEEE 802.11x)

  2. Introduction to IEEE 802.11x Technologies • Evolution of Wireless LAN’s • IEEE 802.11 Design Issues • IEEE 802.11 Services – Overview • IEEE 802.11 MAC Layer Operations • IEEE 802.11a/b/g – Higher-Rate Standards • IEEE 802.11 – Wireless LAN Security • Competing Wireless Technologies

  3. Introduction to IEEE 802.11x Technologies • IEEE 802.11x (high perf. wireless comm. networks) • - over-the –air protocols for wireless LAN • - extension of wired LAN • Goals – seamless roaming / message forwarding / • greatest range of operations / large number of users • Initial standard • - ISM band – Operating Frequency(2.4 Ghz) • speed- 1,2 mbps (FHSS, DSSS, IR) • Applications: Wi-Fi hot spots deployment

  4. Evolution of Wireless LAN’s • Due to the development of wired computer network ,the expansion and increased use of the Internet & large no. of network computers to the network , introduce wireless LANs • The Beginning – ALOHA Net • - 1971 – Network & radio Technology brought together for the1st time during implementation of research project called ALOHA-Net (Hawaii Islands) • This system allows computers at seven campuses out over four islands to communicate with a central computer without using expensive & sometimes unreliable telephone lines. • This system uses Star topology between the central computer and the remote stations.

  5. Extensions to 802.11 • - 802.11 – 2 mbps (wired 10/100 mbps) • - 1999 – 802.11b – 11 mbps(2.4 GHz band)  DSSS • – 802.11a – 54 mbps (5 GHz band) Orthogonal FDMA • - 802.11d – Operation in Other countries • - 802.11e – enhance MAC & PHY (voice, video, audio) • - 802.11f – Multi-vendor AP interoperability • - 802.11h – MAC & PHY (energy management – measurement, reporting, power control) • - 802.11i – Security & Authentication

  6. Extensions to 802.11 • - 802.11j – Operation in Japan (4.9 & 5.0 GHz) • - 802.11k – Radio Resource measurement & Mobility mgmt. • - 802.11ma – Editorial & Technical corrections • - 802.11n – data rates (100 mbps) • - 802.11p – Mobility (200 km/h upto 1000m – 5.8,5.9 GHz) • - 802.11r – enhance BSS & ESS • - 802.11s – Auto-configuration & Multi-hop technologies • - 802.11u – Internetwork with external networks • - 802.11v – Wireless Network mgmt.

  7. Layer 1 : Overview • - WLAN radio cards • - WLAN access points • - Ad hoc or peer-to-peer connection • - WLAN radio link

  8. IEEE 802.11 Design Issues • Wired vs Wireless • - Wired (reliable, predictable transmission) • - Wireless (unreliable, changing topologies, interference) • (multipath propagation, mobility, • battery powered devices, portability) • Services Set’s • Independent Basic Service Set Networks • Distributed System Concepts • Extended Service Set Networks • Integration of Wired & Wireless LAN’s

  9. Independent Basic Service Set Networks • - Fundamental structure of IEEE 802.11x • - peer-to-peer OR ad-hoc • - IBSS = 2 or more wireless stations

  10. Distributed System Concepts • - station-station distance – RF power + propagation condition • - DS – mobility support • – multiple BSS • - Access Point

  11. Extended Service Set Networks (ESS) • - ESS = multiple BSS + multiple DS • - Mobile stations move from 1 BSS to other BSS in same ESS

  12. Integration of Wired & Wireless LAN’s • - Portal (AP) – integration wired LAN + wireless LAN

  13. IEEE 802.11 Services – Overview • Overview of Services – Distribution • Association, Reassociation, Disassociation • Access & Security Control Services • Relationship between Services

  14. Overview of Services – Distribution • - IEEE 802.11 – 9 services • (6 – support MSDU + 3 – control WLAN Access) • - MAC messages – control, data, management • - Distribution Service (STA in Same BSS & Different BSS) • - Integration Service (wired to wireless data delivery) • - Mobility of User • No Transition, BSS Transition & ESS Transition

  15. Association, Re-association, Disassociation • - Association (One to Many & Many to One) • STA associate with AP • many to one mapping of many STA to one AP • No transition mobility • - Re-association • BSS transition mobility within ESS • Initiated by WLAN station • - Disassociation • Termination of Association

  16. Access & Security Control Services • - Authentication between 2 STA • - IEEE 802.11 – open system & shared key • - De-authentication • termination of authentication • - Privacy – encryption of message contents • - WEP (Wired Equivalent Privacy) Algorithm • data frames & authentication msgs.

  17. Relationship between Services • Class 1 Frames (control, management, restricted data frames) • Class 2 Frames (association, re-association, disassociation) • Class 3 Frames (above 3 + restricted data frames)

  18. IEEE 802.11 MAC Layer Operations • MAC Services • LLC/MAC Layer Services Primitives • MAC Basic Frame Structure • MAC Layer Operations – Accessing & Joining Wireless Network

  19. MAC Services • - Accessing the wireless medium, joining a network, authentication & privacy  MAC frames • - MAC frames – control, management, data • - Asynchronous data service • - best effort delivery of MSDU by unicast, multicast, broadcast • - Security – authentication service & WEP encryption • - MSDU – Ordered or Re-orderable multicast

  20. LLC/MAC Layer Services Primitives • - used for comm. between 2 layers • - request, confirm, indication & response • - 3 service primitives • - MA–UNITDATA request • – request transfer of MSDU from local LLC to peer LLC or group of peers • - MA–UNITDATA indication • – transfer MSDU from local MAC to peer LLC • - MA–UNITDATA–STATUS indication • – MAC sublayer to LLC sublayer

  21. MAC Basic Frame Structure • - MAC frame = MAC header + Frame Body + FCS • – header (frame control, duration, address, sequence) • – FCS (32 bit CRC) • - Address (48 bit) – (SA, DA, TA, RA)= BSSID • ~Sequence Field- (16 bit)- 12 bit for sequence no. for each MSDU & 4 bit for MSDU fragment no.

  22. IEEE 802.11a/b/g – Higher-Rate Standards • IEEE 802.11 b • IEEE 802.11 a • IEEE 802.11 g

  23. IEEE 802.11 b • - high speed physical layer extension in 2.4 GHz band • - data rate – 5.5 & 11 mbps • - Modulation – 8 chip CCK (Complementary Code Keying) • - CCK or HR/DSSS

  24. - Modulation – PBCC (Packet Binary Convolutional Coding) - higher data rates - shorter PLCP preamble - limited frequency hopping

  25. IEEE 802.11 a • - high speed physical layer at 5 GHz band using OFDMA • - Data rate – 6, 9, 12, 18, 24, 36, 48, 54 mbps

  26. IEEE 802.11 g • - adopted June 2003 in 2.4 GHz band • - Modulation – PBCC(packet binary convolutional coding) & OFDMA • - Data rate – 6, 9, 12, 18, 24, 36, 48, 54 mbps • - Backward Compliant – 1, 2, 5.5, 6, 11, 12, 24 mbps • - ERP (Extended Rate Physical) Layer • - ERP-DSSS/CCK only mode • - ERP-DSSS/CCK mixed mode • - ERP-DSSS-OFDM & ERP-DSSS/CCK non-ERP mode

  27. IEEE 802.11 – Wireless LAN Security • Types of Wireless LAN Security Problems • Initial IEEE 802.11 Security

  28. Types of Wireless LAN Security Problems • - Eavesdropping • - MAC Spoofing • - Dictionary Attack • - Man-in-Middle Attack • - Theft of Service • - Session Hijacking

  29. Initial IEEE 802.11 Security • - Authentication Details • - IEEE 802.11 User Authentication •  Traffic only from authorized MAC •  Compare MAC address of STA with AP database • or RADIUS Server for authentication • - Drawbacks • - MAC address spoofing • - Authentication tied to h/w instead of user

  30. Initial IEEE 802.11 Security • - WEP Encryption Details

  31. Competing Wireless Technologies • Hiper LAN 1 & Hiper LAN 2 • Home RF & MMAC

  32. Hiper LAN 1 & Hiper LAN 2 • - 1996 – ETSI – BRAN (broadband radio access network) • - 5.2 GHz / 24 mbps / GMSK modulation • - 1998 – HiperLAN2 (25mbps / indoor, local mobility) - high performance, next gen LAN • – HiperAccess (25 mbps / outdoor, fixed operation) • – HiperLink (155 mbps / fixed backbone) • Home RF & MMAC • - Home RF – SWAP (shared wireless access protocol) • - 2.4 GHz, FHSS, 1/2 mbps, disbanded Jan 2003 • - Multimedia Mobile Access Comm. – operation in Japan

More Related