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This was written by Reed Gregory
and given on Thu Jun 20 2002.
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Table of Contents
What is Wireless? Wireless Ethernet is ethernet usually transfered over
radio ways at certain frequencies. It provides a wireless high speed
ethernet connection. It can be very useful for people who have laptops or
other mobile devices that need an internet connection. There are currently
many different Wireless devices with many standards. Some of the standards
include 802.11, 802.11-DS, 802.11-b, 802.11-a, HiperLan, HiperLan II,
OpenAir, HomeRF / SWAP, and BlueTooth. We will focus on 802.11-b, 802.11-a,
and a little BlueTooth. Based on the 802.11 standard which was finalized in September of 1997,
this standard operates at the 2.4 Gigahertz Frequency at speeds of 1, 2,
5.5 and 11 Mb/s. The later 2 speeds were introduced with the 802.11-b
standard. There were only slight changes in the DS physical layer from
802.11. It is by far the most common standard in use today. The GT LAWN
runs on 802.11b. 802.11-a was standardized before 802.11-b as the name implies. It is
just now starting to hit the market however. It is sometimes referred to
as 802.11 at 5 GHz. It offers speeds of 6, 12, and 24 Mb/s and optional
speeds of 9, 18, 36, 48, and 54 Mb/s. BlueTooth is not Wireless LAN. It is a cable replacement technology
mostly developed and promoted by Ericsson with the help of Intel, offering
point to point links and no native support for IP. It is much like a
Wireless USB idea. I only mention it here because of the confusion that
BlueTooth is some kind of Wireless LAN. - ESSID The ESSID is used to
identify cells which are part of the same virtual
network.
As opposed to the NWID which defines a single cell,
the ESSID defines a group of cell connected via
repeaters or infrastructure, where the user may
roam. With some card, you may disable the ESSID
checking (ESSID promiscuous) with off or any (and
on to reenable it).
- NWID As all adjacent wireless networks share the same medium, this parameter is used
to differenciate them (create logical colocated
networks) and identify nodes belonguing to the same
cell. With some card, you may disable the Network
ID checking (NWID promiscuous) with off (and on to
reenable it).
- MODE The mode can be
- Ad-hoc (network composed of only one cell and without
Access Point)
- Managed (network composed of many
cells, with roaming or with an Access Point)
- Master (the node is the synchronisation master or act as an Access Point)
- Repeater (the node forward
packets on the air)
- Secondary (the node act as a
backup master/repeater)
- Auto
- Access Point An access point is just a device that acts as a path from your wireless device to a wired network. Many Access points can be attached together to act as repeaters or even bridged together. But on down the line, an Access Point is in charge of trasferring the wireless signal to a wired network. It acts just like a hub.
- Bandwidth Rate The rate is just a measure of the speed of the connection. In 802.11-b these range from 1 to 11 Mb/s. The nice thing about these is that if your signal is not strong enough for one, it will drop down to the next highest signal. This will auto-negociate to the best rate possible and keep checking at some interval.
The encryption in the 802.11 specification is a RC 4 Algorithm. Much has
been said about the the WEP or Wired Equivalent Privacy key having some
serious security flaws. The key is easily cracked but only after long
periods of time when data can be recieved and then analyzed. The idea
of WEP, however was just to provide a privy equivalent to wired ethernet.
Wired ethernet has privacy because someone would need to get into a
building or get to a wired port. The wireless web is just supposed to
provide a deterent. A better solution to having people not access you
wireless network is to have you AP only talk to specified MAC addresses or
unique wireless cards of authorized users. 802.11-b supports both 64bit and 128bit encryption keys. The GT LAWN
uses ta 64 bit setup. Sometimes you may hear about 40bit or 104bit
encryption. These are the same as 64/128 but that some people refer to 24
of the bits as a different part. First you need pcmcia support to use the PCCard devices. Most people
would only run wireless on laptops because the speed of wired ports is
much better for desktops. I will not go over how to get pcmcia support
in Linux. That is beyond the scope of this document. Most people would
say to use the kernel pcmcia support and use the scripts from the
pcmcia-cs project. The wireless card drivers are either found in the kernel or in a
seperate package. There are a few packages available including pcmcia-cs
and wg-lan. The file that takes care of assigning which driver to which
card is /etc/pcmcia/config . Once you have everything setup you can try to insert the Wirless card and
look at your logs specifically /var/log/messages for information on your
wireless setup. If you do not see anything in those logs, you might want
to make sure pcmcia service is started. The following is a portion of my
logs pertaining to my wireless card. Jun 18 15:40:09 silver-bullet cardmgr[1005]: socket 2: Lucent Technologies WaveLAN/IEEE Adapter
Jun 18 15:40:09 silver-bullet cardmgr[1005]: executing: 'modprobe orinoco_cs'
Jun 18 15:40:09 silver-bullet cardmgr[1005]: executing: './network start eth1'
Jun 18 15:40:10 silver-bullet /etc/hotplug/net.agent: invoke ifup eth1 The Wireless Tools is a set of tools allowing to manipulate the Wireless
Extensions. They use a textual interface and are rather crude, but aim to
support the full Wireless Extension.
iwconfig - manipulate the basic wireless parameters
iwlist - (formerly part of iwspy) allow to list addresses, frequencies, bit-rates
iwspy - allow to get per node link quality
iwpriv - allow to manipulate the Wireless Extensions specific to a driver (private) The latest wireless tools package can be found at http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html Schemes are nice for when you have multiple wireless networks you connect
to at different times. For instance you could have one for the LAWN and one
for your work/room. This way you can just give easy commands to change
the schemes. You can just use the cardctl command to change schemes. cardctl scheme> scheme-name < For scheme support to work, you need to have support for it in 2 files, networks.opts and wireless.opts which are located in /etc/pcmcia/ . Click here to download network.opts. # Network adapter configuration
#
# The address format is "scheme,socket,instance,hwaddr".
#
# Note: the "network address" here is NOT the same as the IP address.
# See the Networking HOWTO. In short, the network address is the IP
# address masked by the netmask.
#
case "$ADDRESS" in
lawn,*,*,*)
DHCP="y"
;;
room,*,*,*)
DHCP="y"
;;
esac Click here to download wireless.opts. Wireless LAN adapter configuration
#
case "$ADDRESS" in
# Lawn stuff
lawn,*,*,*)
INFO="LAWN"
ESSID="GTwireless"
MODE="Managed"
KEY="xxxxxxxxxx"
;;
#room stuff
room,*,*,*)
INFO="apartment room"
ESSID="ssaw318"
MODE="Ad-Hoc"
KEY="off"
;;
# Generic example (decribe all possible settings)
#*,*,*,*)
# INFO="Fill with your own settings..."
# # ESSID (extended network name) : My Network, any
# ESSID=""
# # NWID/Domain (cell identifier) : 89AB, 100, off
# NWID=""
# # Operation mode : Ad-Hoc, Managed, Master, Repeater, Secondary,
# # auto
# MODE=""
# # Frequency or channel : 1, 2, 3 (channel) ; 2.422G, 2.46G
# # (frequency)
# FREQ=""
# CHANNEL=""
# # Sensitivity (cell size + roaming speed) : 1, 2, 3 ; -70 (dBm)
# SENS=""
# # Bit rate : auto, 1M, 11M
# RATE=""
# # Encryption key : 4567-89AB-CD, s:password
# KEY=""
# # RTS threshold : off, 500
# RTS=""
# # Fragmentation threshold : off, 1000
# FRAG=""
# # Other iwconfig parameters : power off, ap 01:23:45:67:89:AB
# IWCONFIG=""
# # iwspy parameters : + 01:23:45:67:89:AB
# IWSPY=""
# # iwpriv parameters : set_port 2, set_histo 50 60
# IWPRIV=""
# ;;
esac The LAWN is the Georgia Tech Local Area Wireless Network. It is a on
going project to provide wireless (802.11-b now) service in campus
buildings. The equipment is Lucent/ Agere wireless Access Points that
can easily be upgraded to 802.11-a. The LAWN works in the following way.
You need to get the WEP key that OIT uses for the LAWN from OIT. Then
once you have the card setup you need to insert the wireless card and
bring up the interface using dhcp. After that, just open a web browser
and sign-in to the LAWN. Now you are on the LAWN. The most up-to-date information on LAWN coverage can be found in the
OIT FAQ: http://faq.oit.gatech.edu/0256.html | Building | Coverage | | 500 Tech Parkway | Full | | 845 Marietta Street | Full | | A.French Building | Full | | Architecture Building | Full | | Manufacturing Research Center | Full | | Bookstore Mall CyberCafe | Full | | Carnegie Building | Full | | Centennial Research Building | Full | | Coliseum Annex | Full | | College of Computing | Full | | Georgia Center for Advanced Telecom Tech | Full | | Human Resources | Full | | Library | Full | | Rich Computing Center | Full | | Van Leer Building | Full | | Wardlaw Center | Full | | 811 Marietta Street | 2nd floor | | Alumni House | 1st floor | | Baker Building | 2nd floor and SE corner of 1st floor | | Calculator | 2nd floor only | | ESM building | Ground floor | | Instruction Center | 2nd floor only | | King Facilities Building | SW office area | | Lyman Hall | 3rd floor S | | MRDC | Varios Parts of 2nd and 3rd Floors | | Pettit Building (MiRC) | Room 102 | These prices were taken from www.buy.com just for an idea of what devices cost. Orinoco Silver PCCard = $61.35
D-Link DWL-650 PCCard - $61.69
Orinoco Gold PCCard - $72.72 D-Link Wireless Access Point - $94.58
Linksys 11Mbps Wireless Access Point - $129.95
Netgear Wireless Access Point - $132.95 Intel Pro/Wirless 5000 CardBus Adapter - $143.95
Netgear HA501NA 802.11A CardBus Adapter - $121.95
SMC EZ Connect 802.11A CardBus Adapter - $106.95 SMV EZ Connect 802.11A Wireless Access Point - $267.95
D-Link Air Pro Wireless Access Point - $272.95
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Linux and Wireless 