Intro to Wireless Networking

NET-150

Objectives

• define the features of the 802.11 wireless LAN standard (Also called Wi-Fi)
• understand the components of the wireless LAN
• explore how wireless LANs are configured
• examine how site surveys are done for wireless LANs
• investigate the issues of securing a wireless LAN

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2

Overview

• A typical computer network uses twisted pair and fiber optic cable to interconnect the LANs. Another media competing for use in higher data-rate LANs is wireless, based on the IEEE 802.11 wireless standard.

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• The advantages of wireless include:

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Benefits of Wireless Networks

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• Increased mobility and collaboration
• Easier network expansion
• Installation Speed and Simplicity
• Scalability.
• A cost effective networking media for use in areas that are difficult or too costly to wire.

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4

IEEE 802.11 Standard

• Institute of Electrical and Electronics Engineers 
• http://www.ieee802.org/
• The IEEE 802.11 wireless LAN standard defines the following:
• Physical (PHY) layer
• How the 1’s and 0’s move through the air
• Medium Access Control (MAC) Layer
• Layer 2 addressing and Collision Avoidance

5

Physical Layer Technologies

There are currently four physical layer technologies, techniques used in 802.11 wireless networking:

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• DSSS – Direct Sequence Spread Spectrum
• 802.11 b
• FHSS – Frequency Hopping Spread Spectrum (Not widely Used)
• OFDM – Orthogonal Frequency Division Multiplexing.
• 802.11a/g/n
• Infrared (special cases)

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Wireless Standards

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Wireless Management Protocols

• Authentication-
• Association –
• Data Delivery –
• Privacy -

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• The wireless management protocols and services are:

determining if someone is who they say

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allocating resources to a device

ensure date gets to designation

encryption

Access Points

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• The access point is a transmit/receive unit (transceiver) that interconnects data from the wireless LAN to the wired network.

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9

SSID

Service Set Identifier

• Essentially the “name” of the wireless network
• Think “Student”, “FacStaff”, “ChampStudent”
• SSID’s used to identify what wireless data traffic is allowed to connect to the network.
• The access point uses the SSID to determine if the client is to become a member of the wireless network.
• The term used to describe that a wireless connection has been obtained is called an association.

10

Look Familiar

SSIDs are like

VLANs for

Wireless LANs

Wi-Fi Channels

As more and more entities are adding Wifi capabilities

• the available bandwidth becomes more crowded
• and the importance of finding a clear channel grows

Wi-Fi Interference

Remember:

• Wireless devices are little radio stations

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• When there are too many radio stations in close proximity they can interfere with each other �

WI-FI Channels - 2.4 GHz

Wifi channels operate primarily at the 2.4 GHz frequency of spectrum.

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There are 11 Channels each 20MHz wide and a total bandwidth of 100MHz is available.

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Math does not add up - so channels overlap!

WI-FI Channels 2.4 GHz

To get the 11 Channels to fit:

• Each channel’s center point is spaced 5MHz from the adjacent channels.

Really only

3 useable

channels

1, 6 and 11. �

WI-FI Channel Placement

Site Surveys:

Help Admins

Configure AP

channels

WIFI Site Survey

WI-FI Security

Wi-Fi Protected Access (WPA2):

• Provide Authentication

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and

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• Encryption�

WI-FI Security- Authentication

WPA2 Authentication:

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Pre-Shared Key (PSK): Password set for the SSID

• Think WI-FI in a Cafe with the Password on the board

Or

Enterprise: Integrated with organization directory

• Think Champ-Student with username/password