Transcript Wireless Networking - Clarkson University

Wireless Networking
By: Todd Deshane
And
Ashwin Venkatraman
Introduction

What is a wireless network?
 A technology
that enables two or more entities to
communicate without network cabling
Different Wireless Networks
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IrDA (Infrared Data Association)
 Uses
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beams in the infrared light spectrum
Bluetooth
 Uses
2.45 gigahertz radio waves, but emits weak
signals
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Limits distance to 10 feet, but travels through walls
HomeRF (SWAP) – developed by businesses
6
voice channels and 1 data channel
 Slow, and limited range, but cheap
Wireless Fidelity (Wi-Fi)
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Essentially, this technology is a variation of the
IEEE 802.11 specification known as 802.11b
Focuses on Direct-Sequence Spread Spectrum
(DSSS)
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High data rate (max of 11 Mbps)
In the case of interference, speed drops in halves (11 Mbps
to 5.5 Mbps to 2 Mbps to 1 Mbps)
Wi-Fi
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Advantages:
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Fast (11 Mbps)
Reliable
Long Range (up to 1000 ft outdoors, 400 ft indoors)
Easy integration to wired networks
Compatible with original 802.11 DSSS standard
Disadvantages:
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Speed may fluctuate
802.11a vs. 802.11b
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Frequency
802.11b transfers at 2.4 gigahertz
 802.11a transfers at 5 gigahertz
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Coverage Distance
802.11b goes about 400 feet indoors
 802.11a goes about 60 feet indoors
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
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Need more access points to cover a location
Compatible to each other?
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Not yet.
ITL Wireless Equipment
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2 Wireless Access Point Routers (with built
in 4 port switch)
 Wired
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Equivalent Privacy (WEP) available
8 Wireless PCMCIA Cards
4
ORiNOCO Gold 11 Mbps PC Cards
 4 3Com 11 Mbps PC Cards
Wireless Access Point
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LINKSYS
 Model
No. BEFW11S4 ver. 2
 Supports
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IEEE 802.3 (10BaseT)
IEEE 802.3u (100BaseTX)
IEEE 802.11b (Wireless)
 Built-in

router capability
Obtains a Clarkson IP and uses DHCP
 Built-in
4 port switch
 Fully-configurable through simple web interface
Wireless Cards
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11Mbs
802.11b compatible
4 3Com Cards
 Model
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No. 3CRWE62092A
4 ORiNOCO (Lucent) Cards
 Model
No. 012352/G
Performance
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Inside Range
 anywhere
except in bathrooms
 Usually 11 Mbps connection
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Outside Range
 To
the SC lecture wing door (closest to ERC)
 Covers faculty lot next to ERC
 Half way to Rowley
 Connection slows as move away from access point
Summer Research
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Protocol
 Method
of Communication
Spoken Language
 Networked Programs (AIM)
 HTTP, Telnet, FTP
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Two Main Protocols (Internet)
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UDP (User Datagram Protocol)
 Fast,
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bare-bones, not reliable or friendly
Can lose data at any time
TCP (Transmission Control Protocol)
 Slower,
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many features, very reliable
All data will get to the other side
PCAttcp
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Measuring tool for TCP and UDP
 Speed,
Throughput, Time
 Amount of Data Sent vs. Amount Received
Our PCAttcp Controller
Enhanced UDP transfers
 Automated the entire process
 Created an easy way to compile results
and graphs using a spreadsheet for output
 Ran tests on various types of connections
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The End!
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Thoughts or
questions?
References
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http://www.howstuffworks.com/wirelessnetwork.htm
http://www.80211planet.com/columns/article/0,4000,1781_96118
1,00.html
http://www.80211planet.com/columns/article/0,4000,1781_9476
61,00.html
http://www.pcausa.com
Different PCATTCP Trials
Same LAN
(inside Clarkson)
Same Host
(same computer)
Same Switch
(same lab)
LAN to Internet (Clarkson
to a Roadrunner service)
LAN to
LAN
(Clarkson
to SUNY
Potsdam)
Note: LAN stands for “Local Area Network”
Bluetooth (cont)
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spread-spectrum frequency hopping – a
device will use 79 individual, randomly
chosen frequencies within a designated
range, changing from one to another on a
regular basis
When two Bluetooth devices come in contact
with each other, they automatically conversate
and form a personal-area network (PAN)
Spread spectrum
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Spread-spectrum – data is sent in small
pieces over a number of discrete
frequencies available for use at any
time
in the specified range
Frequency-hopping spread
spectrum
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send a short burst of data, shift frequencies
(hop) and then send another short burst
Since the FHSS devices that are communicating
agree on which frequencies to hop to, and use
each frequency for a brief period of time (less
than 400 milliseconds) before moving on,
several independent FHSS networks can exist in
the same physical area without interfering with
each other
Direct-sequence spread
spectrum
splitting each byte of data into several
parts and sending them concurrently on
different frequencies
 DSSS uses a lot of the available
bandwidth, about 22 megahertz (MHz).
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The Basics
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4 different types of wireless networks
 IrDA (Infrared
Data Association)
 Bluetooth
 HomeRF
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(SWAP)
“Shared Wireless Access Protocol”
 WECA (Wi-Fi)
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“Wireless Ethernet Compatibility Alliance”
IrDA (Infrared Data Association)
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Uses beams of light in the infrared
spectrum
 Remote
controls
Fairly reliable and low-cost
 Drawback: It is a “line-of-sight” technology

 less

interference
Drawback: “one-to-one” technology
 You
can send data only between two things at
once (but increased security?)
Bluetooth
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The magic number: 2.45 gigahertz
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Radio-frequency also used by baby monitors,
garage door openers, and cordless phones
How do you avoid interference?
 Bluetooth
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Powerful cell phones use 3 watts
 Bluetooth
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sends weak signals of 1 milliwatt
devices limited to 10 meters
But they can go through walls better than others
HomeRF (SWAP)
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Shared Wireless Access Protocol (SWAP)
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6
voice channels and one data channel
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Developed by an alliance of businesses
The data channel is the 802.11 wireless-Ethernet
specification by the IEEE
One drawback: SWAP can only be used
with computers
 Printers
and such need to be attached to a
computer and used as a resource
HomeRF (SWAP)
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Advantages:
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Cheap, easy-to-install
Allows multiple-networks in the same location
Can encrypt data
Drawbacks:
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Not very fast (typically limited to 1 Mbps)
Limited Range (75 to 125 ft)
Physical obstructions (walls, large metal objects) cause huge
interference issues
Difficult to integrate into existing wired networks