wifi Format of lecture

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					         Format of lecture
Introduction to Wireless
    Wireless standards
    Hardware devices
    Performance issues
    Security issues

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         Wireless Technology
 Wireless and mobile computing are the keywords
 Very topical/exciting
 This technology not yet mature
 Promises that we can improvise our existing
  networks without having to lay new wires - roving
  staff will just have to insert a wireless card into
  their device and join the network
 Interesting to compare the what the Telco’s are
  doing with 3G and how this rivals WiFi hotspots
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         Wireless Technology
Wireless technology has to compete with
    digital satellite
    phone lines (HomePNA) 10Mbps
    Power line (HomePlug) 14Mbps
Wireless broadband technology (WiMax)
 gives wire-free transmission of two way
    Bandwidth is an issue here

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           Wireless Technology
What is on the market/coming?
Communication cards to allow data from personal
 digital assistants to be synchronised with desktop
Cards to link laptops and PC’s with Global System
 for Mobiles(GSM) based phones and local area
 network devices
All the above enables firms to set up wireless
 networks without having to use Ethernet cable

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         Wireless Protocols
Wireless LAN
SWAP - Shared Wireless Access Protocol
3G - third generation cellular standard

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         Wireless versus Wired networks
Using Radio frequency (2.4GHz and 5GHz)
Easy to setup a small office or home office
Travel through wall
Easy for network reconstruction

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         What is WiFi?
Wireless LAN IEEE 802.11x network
Promulgated by an association called WiFi
WiFi Alliance certifies all wireless LAN
 IEEE802.11x based products for
All IEEE802.11x based products that passed
 the WiFi Alliances are called WiFi
Wireless Fidelity

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         WiFi Standards
IEEE 802.11a
    An IEEE standard for a wireless network that
     operates at 5 GHz with rates up to 54Mbps
IEEE 802.11b
    An IEEE standard for a wireless network that
     operates at 2.4 GHz with rates up to 11Mbps
IEEE 802.11g – referred to as 54g (but don’t
 confuse that with the 54Mbps!)
    An IEEE standard for a wireless network that
     operates at 2.4 GHz with rates up to 54Mbps

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         WiFi Standards
WPA (WiFi protected Access)
    TKIP encryption and protects against unauthorized
     network access through the use of a pre-shared
     key (PSK)
WMM (WiFi MultiMedia)
    packet prioritisation that meet IEEE 802.11e quality
     of service standard.
    Packets containing time-dependent data such as
     audio or video to be sent ahead of data that can
     safely wait a few microseconds

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         WiFi Hardware
Access points (APs)
PCMCIA cards/ PC cards
USB adapters
PCI network cards
Wireless routers

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         WiFi Applications
    News about wifi and also see if you can find out the
     hotspot(s) around the Stoke-on-Trent area

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         WiFi topology
Ad Hoc
    Without use of Access Point
    Peer-to-peer style communication
    Recommended 3 or less users per channel
    Communication each other devices by the use of
     Access Point
    About 10-30 users per access point

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         Ad Hoc vs Infrastructure
Ad Hoc can be setup instantly for temporary
Scalability is limited to Ad Hoc

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         Wireless LAN

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         Security choices
 Network security ensures the communications and
  files are protected
 How important of the security depend on how you
  want to use the network.
     Browsing internet and mp3 streaming may not need a
     Internet shopping or purchasing will use SSL security
 There are several way to protect your data
  confidentiality while transmitting
 In WLAN, you can change your SSID, WEP or WPA
  or latest technology WPA2

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         Wireless surfing
 Common knowledge that some users use someone
  else’s network connection to use the Internet
     Hi-gain antenna example that I use
 How do you know someone is using you?
     If infrastructure – you don’t – would have to look at router logs
     Ad-hoc – shows in connections window
 How do they know you are not using them in return?

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 Wired Equivalent Privacy
 Encrypt data over the radio waves
 Implemented in MAC layer – NIC encrypt the frame
  before transmit
 Using 64bits or 128bits encryption keys
 Shared secret key
 You need to provide 40 bits (10 digit Hex) or 104bits (26
  digit Hex)
 24 bits Initialisation Vector (IV) for generating key

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         Limitation of WEP
Share, static keys
WEP only encrypt frame within wireless
 station but not within wired network
Limited IV numbers and may increase
 collision - IV repeats after sending 26GB.
Recovery attack - the data can be
 manipulated after a few hours by tracking
 repeating IV

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         WPA and WPA v2
WiFi Protected Access
Different key for each user
48 bit IV – defeats recovery attack on WEP
Use Temporal Key Integrity Protocol (TKIP)
 which dynamic change keys on transmission
More information on

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Security is the main issues in wireless
Still in the development to increase the
Next tutorial you will see wireless security in

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