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Transcript

  • 1. What’s New in Wireless Brad Noblet 10/3/2002
  • 2. Where are we today?
    • 802.11 - A standard for propagating packet based communication over a wireless medium between clients (computers, network appliances, etc.)
      • Founds its roots in Ethernet (802.3)
      • Replaces the physical and link layers with a more “airworthy” equivalent
      • Allows the network (IP) and above layers to remain
      • Also known as Wi-Fi, coined by WECA
    • Uses ISM bands (2.4GHz/5GHz)
      • No primary allocation
      • Power & modulation defined
      • Limited power (100mw)
  • 3. What is 802.11?
    • Data rates started at 1Mbps and have evolved to support up to 54Mbps
    • Delivered by four main standards
        • 802.11
        • 802.11a
        • 802.11b
        • 802.11g (not yet final)
    • Supports seamless device roaming
      • Maintains client connections while mobile
        • Dependent on network topology
  • 4. Basic System Architecture
    • Ad Hoc
      • Peer to peer communications between wireless clients
      • Clients must be within range of one another
      • Limited number of clients
        • No external network connections
    • Infrastructure
      • Clients “associate” with an Access Point or repeater to propagate the signal to other wireless and wired clients and define service
      • Access Points (AP) also participate in handing off connections between themselves as clients roam between APs providing seamless connectivity
      • Many logical networks can share common physical channels
        • Service Set Identifier
  • 5. Basic System Architecture
    • Employs a signal sense/collision avoidance & enforcement scheme
      • Listen before talk
      • Random back-off before talk
      • Listen & enforce to neighbors
    • Range varies from 300’ to 2000’ depending on geography
      • Supports wireless bridging up to 10 miles
  • 6. Access Point
    • Essentially a repeater for clients
      • Bridges clients between themselves and the AP’s wired backbone
    • Keeps track of clients
      • Hands off nodes to other APs during roaming
    • Provides a wired connection to the backbone
    • Provides security access/control mechanisms to determine client connectivity boundaries
    • Provides antenna diversity to help with multi-path
    • Some allow AP power via Ethernet port
      • Allows optimal mounting reducing cable loss to antenna
  • 7. Client adapter
    • Includes the radio, antenna and associated link layer access components to allow connection to an 802.11 network
    • Packaged in many formats
      • PCMCIA (or Mini PC) adapters
      • ISA/PCI adapters
      • External USB and Ethernet converters
    • Software drivers required to link the adapter to the OS logical I/O
      • 802.2 model
  • 8. 802.11 Wireless Appliances
    • Wireless VOIP phones
      • Symbol
      • SpectraLink
    • Personal communicators
      • Vocera
  • 9. Bridges & Gateways
    • Wirelessly link wired or wireless network segments
      • Wireless linking up to 10 miles
    • Provide another means for connecting wired networks to a wireless infrastructure
    • Provide a translation mechanism to other mediums/networks
  • 10. Antennas
    • ERP limited by the standard
    • Client antennas
      • Typically omni (patches & verticals)
    • AP antennas
      • Omni or sectored
    • Bridges/Gateways
      • Yagi or parabolic
    • Reverse polarity connectors
      • TNC & SMA
    • Bi-directional amplifiers
      • Restore cable loss (about 0.5 watts)
  • 11. 802.11b
    • Direct Sequence SS (HR/DSSS)
    • 14 channels worldwide, 11 allocated in US
      • Roughly 2400 MHz to 2450 MHz
    • 11Mbps data rate
      • Rate degrades as conditions deteriorate
      • Actual throughput varies between manufacturer implementations
        • Cisco & OriNOCO (Lucent) the best at better than 4Mbps
  • 12. 802.11a
    • Orthogonal Frequency Division Multiplexing (OFDM)
    • 8 channels, 20 MHz wide available in the US
      • 4 channels @ 5150 MHz to 5350 Mhz
      • 4 channels @ 5725 MHz to 5825 MHz
    • Data rates from 6 to 54 Mbps
    • Not well suited for portable/mobile use
      • Increased power consumption
      • Antenna considerations
      • Better suited for linking
  • 13. 802.11g
    • Orthogonal Frequency Division Multiplexing (OFDM)
    • Operates in the same spectrum as 802.11b
      • Slated to co-exist with 802.11b
    • Data rates up to 54 Mbps
    • Standard not finalized
  • 14. WEP
    • Wired Equivalent Privacy
      • Wireless Eliminates Privacy!
    • Uses RC4 cryptographic cipher
    • WEP systems around RC4 not robust
      • Manual key management open to attack
      • 40 bit keys to short
      • Re-use of key stream
      • Infrequent re-keying
      • Use of a CRC that’s not encrypted
      • AP spoofing
    • WEP can degrade AP and client performance
  • 15. 802.1x
    • Access control
      • Based on Extensible Authentication Protocol (EAP) initially developed for PPP
    • Comprised of challenges and responses between the client and a backend service such as Radius to provide client authentication
    • Not interoperable today between vendors
  • 16. Evolution of 802.11
    • 802.11d
      • Study worldwide regulatory requirements to effect worldwide interoperability
    • 802.11e
      • Quality of Service (QOS) provisions for latency sensitive applications such as streaming audio and video
    • 802.11f
      • Standardize the Inter-Access Point Protocol (IAPP) to allow roaming inside a multi-vendor AP deployed network
  • 17. Evolution of 802.11
    • 802.11h
      • Adds dynamic channel selection and transmit power control for 802.11a
        • A European requirement
    • 802.11i
      • Improved security, not well defined to date
  • 18. Related Services
    • Authentication
      • Bluesocket
        • Class of Service, security across subnets
    • Location dependent services
      • Newbury Networks
        • Position enabled access & push services
    • Total mobility
      • Cisco Mobile Access Router
      • Seamless connectivity while the mobile user roams between infrastructures
  • 19. Tools/Analysis
    • Ethereal
      • Packet Network analyzer
    • Net Stumbler
      • Wireless analyzer
      • Features similar to vendor supplied tools
    • Kismet
      • Passive wireless sniffer
      • Mates well with the Sharp Zaurus PDA
    • AirSnort
      • Wireless sniffer/decryption engine
    • Kotz paper – A live study at Dartmouth
      • Over 500 APs installed, over 2000 users
      • http://www.cs.dartmouth.edu/reports/abstracts/TR2002-423/
  • 20. Emerging Systems & Technology
  • 21. Bluetooth – Personal Area Network
    • Proposed by Ericsson as a replacement for wires to/from cell phones
    • Emerging as a low cost alternative to 802.11
      • Lower speed (1Mbps)
      • 2.4 GHz
    • Slow to gain acceptance
      • Momentum is rising
  • 22. Converged Cellular/PCS Systems
    • 3G systems
      • CDMA 2000
      • GSM/Edge
      • W-CDMA
      • UMTS
    • Share voice bandwidth with data
      • Data rates up to 150Kbps
    • Enabling new services
      • Personal location (Wherify)
      • IM appliances (Hiptop)
    • 4G? – Flarion
      • All IP based
      • 1Mbps+ using only 1.25MHz of spectrum
  • 23. Metropolitan Area Network Canopy
    • TDMA system clocked from GPS
      • Each node given a transmission slot
    • Efficient use of available system bandwidth
    • Roughly 3Mbps end user throughput
    • Micro-cell approach
      • Range of 2-3 miles
    • Wireless backhaul
    • Operates at 5GHz allowing co-location with in-building 802.11b networks
  • 24. Two-Way Systems
    • ICOM D-Star
    • Motorola APCO25
    • Digital Wireless
  • 25. Ultra-Wideband
    • No more wires!
    • Hundreds of MHz wide
    • Many Mbps of bandwidth
    • Utility for the home/office
      • Voice, data, entertainment
    • Fostering a movement towards total spectrum deregulation
  • 26. Wireless is Back!
    • We are a mobile society
    • Wireless (RF) is the only viable technology that allows total mobility regardless of location
  • 27. Manufacturers - Equipment
    • Equipment – APs, bridges/gateways, clients
      • Cisco (Aironet), OriNOCO/Agere (Lucent)
      • Linksys, Netgear, D-Link, Proxim, 3Com, SMC, ICOM, Sony
    • Antennas
      • Pacific wireless
      • Radiall/Larsen
      • Cuschcraft
      • Homebrew – websites abound!
      • Most equipment mfgs offer antennas
    • Bi-directional amps
      • HyperLink Technologies
      • SSB Electronics
      • RF Linx
  • 28. References
    • O’Reilly
      • http://safari.oreilly.com
      • Special thanks to Mike Loukides and O’Reilly for book donations
    • Ethereal – Network analyzer
      • http://www.ethereal.com
    • Net Stumbler – Wireless Analyzer
      • http://www.netstumbler.com
    • Kismet – Passive wireless sniffer
      • http://www.kismetwireless.net
    • AirSnort – Wireless sniffer/decryption engine
      • http://airsnort.shmoo.com
    • Dartmouth study – David Kotz
      • http://www.cs.dartmouth.edu/reports/abstracts/TR2002-423/

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