Whats New in Wireless

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Whats New in Wireless

• Brad Noblet
• 10/3/2002

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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)

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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

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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

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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

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Access Point

• Essentially a repeater for clients
• Bridges clients between themselves and the APs
  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

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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

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802.11 Wireless Appliances

• Wireless VOIP phones
• Symbol
• SpectraLink
• Personal communicators
• Vocera

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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

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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)

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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

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802.11a

• Orthogonal Frequency Division Multiplexing (OFDM)
• 8 channels, 20 MHz wide available in the US
• 4 channels _at_ 5150 MHz to 5350 Mhz
• 4 channels _at_ 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

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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

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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 thats not encrypted
• AP spoofing
• WEP can degrade AP and client performance

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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

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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

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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

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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

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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/TR20
  02-423/

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Emerging Systems Technology
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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

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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

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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

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Two-Way Systems

• ICOM D-Star
• Motorola APCO25
• Digital Wireless

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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

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Wireless is Back!

• We are a mobile society
• Wireless (RF) is the only viable technology that
  allows total mobility regardless of location

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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

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References

• OReilly
• http//safari.oreilly.com
• Special thanks to Mike Loukides and OReilly 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/TR20
  02-423/