Introduction to Wireless LANs

1
Introduction to Wireless LANs
Outline History Business Case Technical
Issues Security
By Gregory Lemmon, BVICS Member
2
The History

• Wireless technologies like most other
  technologies had its birth and development in the
  military. The military needed a simple, cheap and
  secure way of communicating.

3
The History

• Like most other technologies in use today as the
  cost of implementing such decline the quality and
  widespread use increases. Wireless use has
  increased at a frenetic pace over the last ten
  years and more so over the last four years.
  Businesses and Universities are finding it more
  cost effective to implement Wireless Local Area
  Networks (WLAN) to connect buildings rather than
  laying expensive copper or fiber optic cabling.

4
The History

• The Wireless LAN adoption was and continues to
  be driven by SOHO (Small Office Home Office) and
  home users who wanted to share internet
  connection among several computers without the
  hassle of running cables.

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The Business Case

• WLANs main offering to businesses is mobility
  particular in large corporations with several
  buildings and many users moving around with
  Laptops computers. The predecessor to WLANs was
  cellular technology but it was expensive and very
  slow, with WLANs those disadvantages are
  eliminated.

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The Business Case

• Apart from mobility WLANs also provide away to
  extend the network for some corporations without
  the expense of running copper or the even more
  expensive fiber optic cable.

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The Business Case

• It must be noted though that for all the
  advantages it offers WLANs cannot be considered
  as a replacement at this stage in the
  technologys life as a replacement to wired LANs
  (Ethernet) in terms of data rates compare
  100BaseTx at 100Mbps to IEEE 802.11a at 54Mbps.

8
The Technical Issues

• The Basics
• Wireless devices operate under one of the
  several standards set by the IEEE (Institute of
  Electrical and Electronics Engineers). The IEEE
  is the body responsible for making/setting
  standards for information technology in the
  United States and their standards are always
  created within the framework of laws created by
  the FCC.

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The Technical Issues

• There are several standards that
• govern wireless devices, they are
• 802.11
• 802.11b
• 802.11a
• 802.11g
• 802.11i

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The Technical Issues

• IEEE 802.11
• The first standard describing the operations of
  WLANs, it contained all of the available
  transmission technologies such asa DSSS, FHSS and
  infrared.

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The Technical Issues

• IEEE 802.11
• DSSS (Direct Sequence Spread Spectrum) is
  described under the IEEE 802.11 standards as
  systems that operate at 1 and 2 Mbps speeds only,
  though systems that also operate at 11Mbps can be
  considered as a DSSS device as well.

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The Technical Issues

• IEEE 802.11
• FHSS (Frequency Hopping Spread Spectrum) also
  operate at 1 and 2Mbps and similarly systems
  operating outside the 1 and 2Mbps range are not
  considered 802.11 compliant systems and may or
  may not communicate with 802.11 devices/systems.

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The Technical Issues

• IEEE 802.11
• The 2.4GHz ISM (Industrial, Scientific and
  Medical) band which is license free is the
  operating frequency for 802.11 devices.

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The Technical Issues

• IEEE 802.11b
• As is the case with all other areas of
  technology development the 802.11 standards soon
  became obsolete as devices began to exchange
  data at rates of 11Mbps. The problem was that
  different vendors had their own implementation of
  this which led to incompatibilities without a
  standard to follow.

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The Technical Issues

• IEEE 802.11b
• Fortunately though the manufacturers sorted out
  the incompatibilities, which led to the IEEE
  establishing the 802.11b standard.

16
The Technical Issues

• IEEE 802.11b
• IEEE 802.11b was referred to as Wi-Fi and
  specified data rates of 1, 2, 5.5 and 11Mbps
  under the DSSS operations. FHSS devices are not
  covered under 802.11b, and 802.11b devices are
  backward compatible with 802.11 devices.

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The Technical Issues

• IEEE 802.11a
• The IEEE 802.11a standard governs devices
  operating in the 5GHz UNII (Unlicensed National
  Information Infrastructure) bands.

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The Technical Issues

• IEEE 802.11a
• 802.11a devices by nature are incompatible with
  all other devices complying with the other 802.11
  standards. Devices using the 5GHz range will not
  communicate with 2.4GHz devices and these devices
  (5GHz) operate at data rates of 6, 9, 12, 18, 24,
  36, 48 and 54Mbps.

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The Technical Issues

• IEEE 802.11g
• The most versatile of all the devices, these
  devices operate at both the speeds of 802.11a and
  802.11b devices. This backward compatibility
  makes upgrading WLANs fairly inexpensive.

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The Organisations

• IEEE
• The Institute of Electrical and Electronics
  Engineers as mentioned is the body that is
  responsible for setting/making the standards that
  govern information technology and their website
  is www.ieee.org

21
The Organisations

• Wi-Fi Alliance
• The group promotes and tests for WLAN
  interoperability. Their mission is to certify
  interoperability of Wi-Fi products and to promote
  as the global wireless LAN standard across all
  market segment.
• URL www.wi-fi.com

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The Organisations

• European Telecommunications Standards Institute
• The ETSI the European version of the IEEE. There
  have been talks of IEEE and ETSI unifying on
  wireless standards, given that ESTIs HiperLAN/2
  standards directly compete with IEEEs 802.11a
  standards.
• For further reading see ESTIs website
  www.esti.org

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The Organisations

• Other organizations that are involved in the
  wireless development are
• Wireless LAN Association www.wlana.org
• HomeRF www.homerf.org
• Bluetooth www.bluetooth.com
• Infrared Data Association www.irda.org

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Basic Setup/Location of a WLAN

• The first thing that happens after you setup a
  WLAN client (laptop, PDA or some other device
  that seeks to connect to the network wirelessly)
  is that it listens for a WLAN within range and
  attempts to discover if it can associate with
  this WLAN.

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Basic Setup/Location of a WLAN

• This is called scanning, and it occurs before
  any other process, because this is how the client
  finds the network. The client listens/scans for
  enough packets to detect what is know as the
  Service Set Identifier (SSID).

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Basic Setup/Location of a WLAN

• The SSID is a unique alphanumeric string ranging
  from 2 32 characters long and is essentially
  the WLAN network name. It can be considered the
  most basic form of WLAN security (which is really
  no security at all).

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Authentication and Association

• Authentication for WLAN clients is a basic
  process in most cases of the client and access
  point exchanging some information (data packets).
  The client sends an authentication request to the
  access point, which responds by granting or
  denying the client access to the network based on
  the (security and authentication requirements)
  settings of the access point.

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Authentication and Association

• Association is the point at which the client is
  allowed to pass data through the access point and
  happens after the client is allowed to
  authenticate with the access point.

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Security

• WLANs are inherently insecure, for that very
  reason many Information Professionals have not
  deployed or have stayed away from Wireless
  technologies as far as networks go. We will take
  a brief look at some of the basic things that can
  be done to secure your WLAN.

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Securing your WLAN

• Use WEP
• Filter

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Securing your WLAN

• WEP
• Wired Equivalent Privacy is a method of
  encryption based on a Shared Key authentication
  process. WEP authenticates the users and
  encrypts the data packets over the WLAN. WEP is
  either 40 (64) or 104 bit (128) keys.

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Securing your WLAN

• Filtering
• Filtering is another fairly basic method
• of securing your WLAN and can be
• done at three levels
• SSID
• MAC
• Protocol

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Securing your WLAN

• SSID Filtering is very basic and offers no great
  level of security. Remember that the clients
  authenticates by discovering the SSID which is
  broadcasted in clear text, so it is very easy to
  get this information by just listening to the
  broadcasts of an access point.

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Securing your WLAN

• MAC address filtering is a bit more secure since
  it allows a client to authenticate based on
  pre-defined MAC addresses entered by the System
  Administrator or the operator of the WLAN.

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Securing your WLAN

• Implementing protocol filtering is very similar
  to that of wired LANs.

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Further Reading

• http//www.wi-fiplanet.com/tutorials
• http//www.cerias.purdue.edu/tools_and_resources/h
  otlist/details.php?id26
• http//www.cwne.com/cwna/

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Thank you