Communication Networks Laboratory Project

1
Communication Networks Laboratory Project

• Wireless 802.11 Network Sniffer
• By Uri Kogan and Idan Arad
• Under supervision of Ilan Hazan
• Technion

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Statement of the Problem

• Is it possible to code wireless network sniffer
  for Intel 2011B Wireless network card?
• During the development problemIs it possible to
  activate existing driver for this card?

3
Project Overview

• Intel Card
• Wirless Networks using 802.11 protocol
• Desktop PC, laptops, PDAs
• Access Points with switching capabilities

4
Project Purpose

• Learning device drivers management in Linux OS
• Creating sniffer
• Getting statistic and parameters of the data
  flowing through access point
• Protocol independent data.

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Research

• Learning 802.11 protocol.
• Compiling Linux driver for specified card.
• Making the driver to work inside the kernel.
• Making driver to work perfectly with the
  hardware.
• Writing actual sniffer application.
• Writing user interface for the sniffer.

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Basics of 802.11 protocol
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802.11 Frame Format

• Preamble 80-bits of alternating zeroes and ones
• PLCP Header transmitted at 1 Mbit/s the header
  we need packet length, rate information, header
  16-bit CRC

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MAC data to extraction
WEP encryption algorithm used in this packet
more fragments of the same upper level frame are
coming after this one
Power management state of transmitting station
after packet transmission
To or from current Service Set
More frames are buffered for this station by AP
Retransmission of previous packet
Management/ control/data
Protocol version
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MAC data to extraction

• Power-Slave Poll Station ID
• NAV calculation

Intermediate Recipient Address if ToDS is set or
end-station address if ToDS is clear
Physical transmitter address (if ToDS is set- AP
address, ToDS clear- transmitting station)
FromDS set- packet original source station, ToDS
set- packets final destination station
Order of different fragments belonging to the
same frame
Transmission between APs, ToDS and FromDS are
set, no original source and final destination
addresses
32-bit CRC
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Materials

• Linux OS
• Kernel 2.4.7
• PCMCIA-cs package for Linux version
  blah-blah-blah
• Device driver v1.03
• Device driver v1.04
• Wireless network card

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Procedure

• Driver v1.03 doesnt support 2011B card, only
  2011.
• Driver v1.04 (received from the developer) may
  support 2011B card.

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Conclusion

• Right now, the driver
• is compiled
• works inside the kernel successfully identifies
  the card
• Transmits
• but ? fails to receive packets

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Works Cited

• Technical Tutorial on the IEEE802.11 protocol,
  BreezeCom Wireless Communications, 1996
• Previous semester projects material