Linux.Wireless.pdf

< Linux Wireless LAN Howto >

Linux Wireless LAN Howto

Jean Tourrilhes

14 November 01

Linux & Wireless LANs : Un*x, with no string attached...

1 Introduction

This document will explore the magical world of Wireless LANs and Linux .

Wireless LAN is not a very widespread and well known technology, even in the

Linux world, so we will try to gather here most of the available information.

Despite the fact that it is very similar to common networking technologies, it is

significantly different to justify this specific document covering the subject.

1.1 What is a Wireless LAN ?

It’s a networking technology allowing the connection of computers without

any wires and cables (apart from the mains), mostly using radio technology (and

sometime infrared ). It’s called LAN (Local Area Network) because the range

targeted is small (within an office, a building, a store, a small campus, a house...).

This technology is slowly growing (I should say maturing), and despite a general

lack of interest, Linux is able to take advantage of some of the wireless networks

available.

1.2 Content of this document

My first task is to talk a bit about the different Wireless LANs options under

Linux. What the products on the market are, their compatibility with Linux and

where to find the necessary bits and pieces to make them work. This should help

you to make your mind on the product of your dreams.

Once you’ve picked a Wireless LAN, you will have to live with it. The next

chapter go through the main differences of Wireless LAN compared to other

networking technologies. This includes the main steps of the installation and usage

considerations.

Then, we will have a nice overview of the Wireless Extensions . The Wireless

Extensions is a new standard interface to configure Wireless LAN devices and get

wireless specific statistics from them. Of course, this is a Linux exclusivity !

At this point, you will find a long and dense section, talking mostly of the

different technologies used in Wireless LANs and other boring related stuff. It is

quite safe to skip that one.

1.3 Target and Assumptions

The main goal of this document is to reduce the traffic of unanswered

questions related to wireless in the Linux newsgroups and mailing lists (and in my

< Linux Wireless LAN Howto >

mailbox). After that, you should have no more arguments for asking foolish

questions around.

I hope that this document will help people to make the most of their Wireless

LAN under a competent operating system and understand what is in the box. If I

could convince people to give it a try, it would make me happy.

This document act mostly as a complement to the exhaustive documentation

existing for Linux. Because of that, I might not explain every details of everything

and target already quite knowledgeable people. Don’t worry, there is a section on

how to improve your culture at the beginning of the section 3 .

1.4 Legal stuff

Strange world where everybody has to protect himself from sharks, lawyers

and crazy people :

Any information in this document is purely fictious and any resemblance to

real hardware, software or driver is purely coincidental...

I mean, if because you read this document your hardware burn, you get fired

from your job or anything else bad happen, I’m not responsible, it can’t be my fault,

so please use your own brain. Writing this kind of documents is not part of my job

at HP, so I don’t expect them to claim any responsibility for its content.

Any brand mentioned in this document is trademark of its respective owner.

For example Linux is a trademark of Linus Torvalds.

Then, this is my document, written by me (Jean Tourrilhes), therefore I own

its copyright. So don’t remove my name (and copyright notice) and pretend that you

wrote it yourself. In matter of copy, distribution and modification, you should ask

me politely and use common sense.

Having said that, this document is also licensed under the terms of the Linux

Documentation Project Copying License .

1.5 This document

This document is only available in the format that are convenient to me

(acrobat/pdf, html). It might be updated in the future (if I feel like it and if I have

some time). I guess that it is pretty safe to assume that it will still be available for

the time to come at these web addresses :

http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wireless.html

http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wavelan.html

I may be reached at the following e-mail address :

jt@hpl.hp.com

Constructive comments and interesting information are welcomed. I hope

that you will help me to keep this document up to date and improve its content.

Comments about my english and my style will be answered in french. Flames

and spam will be processed through a Rayleig Fading channel with a -120 dB

attenuation in order to reduce the noise :-)

< Linux Wireless LAN Howto >

2 The devices, the drivers

This section describes the most common Wireless LAN products available on

the market and their compatibility with Linux. I will make a short description of

each product and will mainly focus on the drivers.

Except in a few case, you need a driver to interface you wireless network

device to the Linux kernel. The availability of a driver is as usual your main

concern, especially with wireless devices because few people are using such

hardware, so few of them are willing to develop, debug and maintain such a piece

of code.

For each driver, I will list its status (stable, buggy...), the maintainer , the

version , how to get it and the main features . If you hear about something new or if

you have developed yourself a driver, please notify me.

2.1 Lucent Wavelan & DEC RoamAbout DS

Driver status : stable

Driver name : ISA : wavelan.o

Pcmcia : wavelan_cs.o

Version : v19 (20/4/99), v20 (29/7/99) or v23 (10/10/00)

Where : ISA : Linux kernel (2.0.37, 2.2.11 & 2.3.15)

Pcmcia : Pcmcia package (3.0.11)

Creators : Bruce Janson (ISA) and Anthony D. Joseph (Pcmcia)

Maintainer : Jean Tourrilhes <jt@hpl.hp.com>

Web page : http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wavelan.html

Mailing list : http://lists.samba.org/pipermail/wireless/

Documentation : man pages, headers

Configuration : Wireless Extensions

Statistics : Wireless Extensions

Multi-devices : isa : up to 4

pcmcia : yes

Interoperability : proprietary protocol, interoperate with Windows

Other features : module, hardware multicast, Wireless Extensions, SMP

Non implemented : roaming

Bugs : see release notes on web page :-(

License : GPL & OpenSource

Vendor web pages : http://www.wavelan.com/

http://www.networks.digital.com/dr/wireless/

http://www.cabletron.com/dnpg/dr/npg/lanfm-mn.html

< Linux Wireless LAN Howto >

2.1.1 The device

The Wavelan has been around for quite a while now, and this product is now

discontinued . The Wavelan is a radio LAN, using the 900 MHz or 2.4 GHz ISM

band (Direct Sequence). It is built by Lucent, formerly AT&T, formerly NCR, and

there is a few OEM version (for example the DEC RoamAbout DS). The Wavelan

comes in two flavours, an ISA card and a PCMCIA card (plus the access point).

The Wavelan appears to the PC as a standard network card and interfaces

naturally with the networking stack. The configuration includes setting the

frequency (10 different channels), Network ID (16 bits). Hardware encryption is

optional (DES or AES - 64 bits key).

This product is built around a standard Ethernet controller (that may be

found in some 3Com and Intel Ethernet cards), and the Ethernet physical layer is

replaced by a radio modem. The ISA and Pcmcia cards share the same basic

architecture, have the same modem, but have different Ethernet Controllers and

bus interfaces (the pcmcia has only one transmit buffer). Because the Wavelan

doesn’t use a specific radio MAC (no MAC level retransmissions for example), it

uses very efficiently the bandwidth, but is more sensitive to packet loss and

collisions.

There is two versions of the modem, a 900 MHz and a 2.4 GHz version.

Revision 2 of the 2.4 GHz modem allows the user to set the frequency (from a set

of predefined channels - the availability of each channel depend on the regulation).

The Wavelan is Direct Sequence Spread Spectrum (11 chips encoding), using a

2 Mb/s signalling rate (using effectively 22 MHz of bandwidth) and diversity

antennas.

2.1.2 The driver

The ISA driver has also been around for quite a while now in the kernel and

is pretty stable. The last set of modifications were to solve a few remaining small

problems and add Wireless Extensions and some other features, so the driver is

fairly complete now. The only things remaining to do is the implementation of the

roaming protocol (but it might come, if I’m not too lazy...).

The Pcmcia driver has caught up with the ISA one to offer the same level of

functionality and reliability. The only difference are the pcmcia specific functions

(auto loading, auto unloading, crude power saving).

The latest releases of both drivers (v23) adds SMP support.

The drivers use the card EEprom to save the configuration changes for

subsequent reboots. Wireless Extensions let you configure the NWID, the

frequency, the sensitivity and the encryption key (optional). Statistics include the

signal quality, signal level, noise level and the count of packet received with an

invalid NWID (see Wavelan documentation). Private Wireless Extensions include

the setting of the quality threshold.

2.2 Lucent Wavelan IEEE, Orinoco, Enterasys RoamAbout 802,

Elsa AirLancer 11 and Melco/Buffalo 802.11b

Driver status :

stable (but no longer maintained - see section 2.3 )

< Linux Wireless LAN Howto >

Driver name : wvlan_cs.o

Version : v1.0.7

Where : Pcmcia package (3.1.25)

Maintainers : Anton Blanchard <anton@samba.org>

Andreas Neuhaus <andy@fasta.fh-dortmund.de>

Harald Roelle <harald@roelle.com>

Web pages : http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wavelan-IEEE.html

http://www.fasta.fh-dortmund.de/users/andy/wvlan/

http://www.roelle.com/wvlanPPC/index.html

Mailing list : http://lists.samba.org/pipermail/wireless/

Documentation : man page, headers

Configuration : Wireless Extensions & module parameters

Statistics : Wireless Extensions

Multi-devices : Yes

Interoperability : 802.11-DS and 802.11-b, interoperate with Windows

Other features : MTU selection, multicast, promiscuous mode, power

management, WEP hardware encryption, SMP, multi-

firmware and PPC support.

Non implemented : Some optimisations...

Bugs : May have some performance issues

License : GPL

Vendor web page : http://www.wavelan.com/

http://www.enterasys.com/wireless/

http://www.elsa.com/

http://www.hp.com/notebooks/us/eng/products/wireless/

http://www.buffalotech.com/

http://www.1stwave.de/

http://www.artem.de/

2.2.1 The device

Even if it uses the same name, the Wavelan IEEE product is completely

different from the old Wavelan, and totally incompatible in term of protocol and

hardware interface. It is still built by Lucent, and it still operate in the 2.4 GHz

ISM band (Direct Sequence), but the new hardware fully support the IEEE 802.11

protocol (and 802.11-b for the more recent versions) and is no longer based on a

Ethernet MAC chip. There is only a Pcmcia version (the ISA version uses a ISA to

Pcmcia bridge) and the different access points. Recently, Lucent has added a USB

adapter and mini PCI version of the card for laptop (this one is based on a PCI-

Pcmcia bridge).

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