presentation

1. In addition to the wired network, various
technologies exist that allow the transmission of
information between hosts without cables.
These are known as wireless technologies.
Wireless technologies use electromagnetic waves
to carry information between devices.
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2.  infrared (IR) is relatively low energy and cannot
penetrate through walls or other obstacles.
 A specialized communication port known as
an Infrared Direct Access (IrDA) port uses IR to
exchange information between devices.
 IR only allows a one-to-one type of
connection.
 It is generally used for short-range, line-of-
sight, communications.
 IR is also used for remote control devices,
wireless mice, and wireless keyboards.
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3.  RF waves can penetrate through walls and
other obstacles, allowing a much greater range
than IR.
Bluetooth
 Bluetooth is a technology that makes use of
the 2.4 GHz band.
 It is limited to low-speed, short-range
communications, but has the advantage of
communicating with many devices at the same
time.
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4.  It use 2.4 GHz and 5GHz
 It have various IEEE(Institution of Electrical
and Electronics Engineers) 802.11 standards
 They transmit at a much higher power level,
which gives them a greater range.
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5.  A number of standards have been developed
to ensure that wireless devices can
communicate.
 They specify the RF spectrum used, data
rates, how the information is transmitted.
 The main organization responsible for the
creation of wireless technical standards is the
IEEE.
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6.  There are four amendments to the IEEE 802.11
standard that describe different characteristics
for wireless communications.
 Currently available amendments are 802.11a,
802.11b, 802.11g and 802.11n. (802.11n is not
ratified)
 Collectively these technologies are referred to
as Wi-Fi, Wireless Fidelity.
 The Wi-Fi logo on a device means that this
equipment meets standards and should
interoperate with other devices of the same
standard.
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7. 802.11a:
 Uses 5 GHz RF spectrum
 Not compatible with 2.4 GHz spectrum, i.e.
802.11b/g/n devices
 Range is approximately 33% that of the 802.11 b/g
 Relatively expensive to implement compared to
other technologies.
802.11b:
 First of the 2.4 GHz technologies
 Maximum data-rate of 11 Mbps
 Range of approximately 46 m (150 ft) indoors/96
m (300 ft.) outdoors
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8.  802.11g:
 2.4 GHz technologies
 Maximum data-rate increase to 54 Mbps
 Same range as the 802.11b
 Backwards compatible with 802.11b
802.11n:
 2.4 GHz technologies (draft standard specifies
support for 5 GHz)
 Extends the range
 Backwards compatible with existing 802.11g
and 802.11b equipment (draft standard
specifies 802.11a support)
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9.  WPAN
– Wireless Personal Area Network
– used for:
• mice
• keyboards
• PDAs
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10.  WLAN
– Wireless LAN
– uses RF standards
– conform to 802.11 standards
– connects through
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11.  WWAN
– Wireless WAN
– coverage over large areas
– cell phone network
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12.  Access Point
 Controls access between a wired and a
wireless network. I.E. allows wireless clients
to gain access to a wired network and vice
versa.
 Acts as a media converter accepting the
Ethernet frames from the wired network and
converting them to 802.11 compliant frames
before transmitting them on the WLAN.
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13.  Wireless bridge
 Used to connect two wired network through a
wireless network.
 Allows long rage point to point connection between
networks.
– connects two wired networks through a wireless
link
– offers long range connectivity
• 25 miles
– Uses unlicensed RF frequencies
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14.  Antennas:
 Used on APs and Wireless bridges
 Increases the output signal strength from a wireless
device
 Receives wireless signals from other devices such
as STAs
 Directional antennas concentrate the signal
strength into one direction.
 Omni-directional antennas are designed to release
equally in all directions.
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15.  Service Set Identifier (SSID)
 The SSID is a case-sensitive, alpha-numeric
string that is up to 32-characters.
 The SSID is used to tell wireless devices which
WLAN they belong to and with which other
devices they can communicate.
 All wireless devices in a WLAN must be
configured with the same SSID in order to
communicate.
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16.  The simplest form of a wireless network is
created by connecting two or more wireless
clients together in a peer-to-peer network.
 A wireless network established in this manner
is known as an ad-hoc network and does not
include an AP.
 All clients within an ad-hoc network are equal.
The area covered by this network is known as
an Independent Basic Service Set (IBSS).
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17.  Although an ad-hoc arrangement may be good
for small networks, larger networks require a
single device that controls communications in
the wireless cell.
 The AP controls all communications and
ensures that all STAs have equal access to the
medium.
 The area covered by a single AP is known as a
Basic Service Set (BSS) or cell.
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18.  The area of coverage of a single AP is limited.
To expand the coverage area, it is possible to
connect multiple BSSs through a Distribution
System (DS).
 This forms an Extended Service Set (ESS).
 An ESS(Extended service set) uses multiple
APs. Each AP is in a separate BSS.
 In order to allow movement between the cells
without the loss of signal, BSSs must overlap
by approximately 10%.
 This allows the client to connect to the
second AP before disconnecting from the first
AP.
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19.  Channels are created by dividing up the
available RF spectrum.
 Each channel is capable of carrying a different
conversation.
 Normally each wireless conversation makes
use of a separate channel.
 Some of the newer technologies combine the
channels to create a single wide channel,
which provides more bandwidth and
increases the data rate.
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20. CSMA/CA
 Wireless technology uses an access method called Carrier Sense
Multiple Access with Collision Avoidance (CSMA/CA). CSMA/CA
creates a reservation on the channel for use by a specific
conversation.
 Ensures collisions do not occur on a wireless network
 Reserves a channel for communication
– Device requests permission from AP (Request to Send–RTS)
– If available, AP responds with all clear message
• Clear to Send Message (CTS)
– CTS is broadcast to all other devices
• informs everyone the channel is being used
– Upon completion of conversation
• Device that requested channel send ACK to AP
• ACK indicates to AP that channel can be used again
• ACK sent to other devices letting them know the channel can be used
again
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23.  Wireless Mode
 Most home AP devices can support various
modes, mainly 802.11B, 802.11G and
802.11N.
 The type of mode enabled on the AP depends
on the type of host connecting to it.
 If only one type of host connects to the AP
device, set the specific network mode to
support it.
 If multiple types of hosts will connect, select
Mixed mode.
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24.  SSID
 The SSID is used to identify the WLAN.
 All devices that wish to participate in the
WLAN must use the same SSID.
 To allow easy detection of the WLAN by
clients, the SSID is broadcast.
 It is possible to disable the broadcast feature
of the SSID.
 If the SSID is not broadcast; wireless clients
will need to have this value manually
configured.
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25. Wireless Channel
– auto locate
• finds the least congested(blocked)
channel
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26.  Wireless host (STA) – device that contains a
wireless NIC and wireless software
– client configuration must match that of the Access
Point
 Windows XP
– wireless client software
– included as part of the operating system
– can control most configurations
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27.  Using stand-alone software
– supplied with the wireless NIC
– includes enhanced functions
 Not possible to allow both XP and the stand-
alone software at the same time
 Once software is installed, check connectivity
– connection data rate
– connection status
– wireless channel used
– ping
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28.  No physical connection needed
 Attacker can “tune into” your network just like
tuning into a radio station
 Easy access if all settings are set to default,
so . . .
 CHANGE THE SETTINGS
– disable SSID
– change default password
– change default IP
 But . .
– SSID transmitted in clear text
– still possible to learn the SSID
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29.  Another security feature
 Will limit access to your network
 MAC address used to identify which device
can connect to the wireless network
– wireless AP looks up MAC in a list (database)
– only those addresses listed will gain access
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30.  Controls who connects to the network
 Permitted based on set of credentials
 Helps to verify the “trustworthiness” of the
device
– usernames
– passwords
 Occurs before client is connected to WLAN
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31.  On by default
 Any and all clients can access AP
 Should only be used on public wireless
networks
– Schools
– Internet Café
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32.  Both AP and client must have the same secret
key or word
 Here’s how it works:
– AP sends random string of bytes to client
– Client accepts it, encrypts it, and sends it back to
AP
– AP receives encrypted string, decrypts it
– if decrypted string = original string  client is
added
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33.  EAP software must be installed on the client
device
 Client talks with RADIUS Server
– Remote Authentication Dial-in User Services
– server functions separately from the AP
– server keeps a database of valid users
– username and password checked by the server
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34.  Process of transforming data so if intercepted,
will still be unusable
 WEP (Wired Equivalency Protocol)
– advanced security feature
– encrypts network traffic as it travels
– 64 – 128 bits (letters and/or numbers)
– AP and every device on the network must have the
same WEP key
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35.  Controls the type of traffic allowed across a
WLAN
 Able to block traffic based on:
– IP Address
– MAC Address
– Port Numbers
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36.  Basic setup
 Router IP address
 DHCP
 Starting IP address
 Max no computer to connect
 Admin
 Change default password
 Basic wireless setting
 Network mode
 Channel
 SSID
 Wireless security
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