The Linux Network Administrator's Guide, Third Edition dispenses all the practical advice you need to join a network. Along with some hardware considerations, this highly acclaimed guide takes an in-depth look at all of the essential networking software that comes with the operating system--including basic infrastructure (TCP/IP, wireless networking, firewalling) and the most popular services on Linux systems.
But as the follow-up to a classic, the third edition of the Linux Network Administrator's Guide does more than just spruce up the basics. It also provides the very latest information on the following cutting-edge services:

* Wireless hubs

* OpenLDAP

* FreeS/WAN

* IMAP

* Spam filtering

* OpenSSH

* BIND

* IPv6
Featuring a litany of insider tips and techniques, the Linux Network Administrator's Guide, Third Edition is an invaluable companion for any network administrator interested in integrating Linux into their Windows environment
Authored by Terry Dawson, Tony Bautts, and Olaf Kirch, the Linux Network Administrator's Guide, Third Edition emerged from the Linux Documentation Project (LDP). The LDP's goal is to centralize all of the issues of Linux documentation, ranging from online documentation topics such as installing, using, and running Linux.

The Linux Network Administrator's Guide, Third Edition dispenses all the practical advice you need to join a network. Along with some hardware considerations, this highly acclaimed guide takes an in-depth look at all of the essential networking software that comes with the operating system--including basic infrastructure (TCP/IP, wireless networking, firewalling) and the most popular services on Linux systems. But as the follow-up to a classic, the third edition of the Linux Network Administrator's Guide does more than just spruce up the basics. It also provides the very latest information on the following cutting-edge services:* Wireless hubs * OpenLDAP * FreeS/WAN * IMAP * Spam filtering * OpenSSH * BIND * IPv6 Featuring a litany of insider tips and techniques, the Linux Network Administrator's Guide, Third Edition is an invaluable companion for any network administrator interested in integrating Linux into their Windows environment Authored by Terry Dawson, Tony Bautts, and Olaf Kirch, the Linux Network Administrator's Guide, Third Edition emerged from the Linux Documentation Project (LDP).

The LDP's goal is to centralize all of the issues of Linux documentation, ranging from online documentation topics such as installing, using, and running Linux.

The Linux Network Administrator's Guide, Third Edition updates a classic Linux title from O'Reilly. This refreshed resource takes an in-depth look at everything you need to know to join a network. Topics covered include all of the essential networking software that comes with the Linux operating system, plus information on a host of cutting-edge services including wireless hubs, spam filtering, and more.

Terry Dawson is an amateur radio operator and long time Linux enthusiast. He is the author of a number of network related HOWTO documents for the Linux Documentation Project, co-author the 2nd edition of O'Reilly's Linux Network Administrators Guide and is an active participant in a number of other Linux projects. Terry has 15 years professional experience in telecommunications and is currently engaged in network management research in the Telstra Research Laboratories.

Gregor N. Purdy is engineering manager in the large account services group at Amazon.com. Before joining Amazon.com in 2003, Gregor worked for ten years as a consultant in high-end data warehousing, system integration, and prior art research in software and Internet patents. He has also contributed to a number of open source projects, including Perl core and extension modules, the Perl Shell, and the Parrot virtual machine for Perl 6.

CHAPTER 18 Wireless Networking

Wireless networking is a promising and increasingly popular technology, offering a wide range of benefits compared to traditional wired technology. These advantages range from increased convenience to users and decreased deployment cost to ease of network installation. A new wireless deployment can save substantial amounts of money since there is no need for additional cables, jacks, or network switches. Adding new users to a network can be as easy as plugging in a wireless card and powering up a machine. Wireless networking has also been used to deliver network access to areas where there is little or no traditional network infrastructure.

Perhaps the biggest impact of wireless networking can be seen within its widespread acceptance among consumers. The most obvious example of this popularity can be seen with new laptop systems, where nearly every unit is shipped with integrated 802.11b or g. The practical benefits have consequently insured good sales, allowing manufacturers to lower the equipment costs. At the time of this writing, the price of client wireless cards is comparable to that of traditional Ethernet adapter cards.

These benefits, however, do not come without some disadvantages, the most severe of these being the security issues.

History

Wireless LANs are based on spread spectrum technology, initially developed for military communications by the U.S. Army during World War II. Military technicians considered spread spectrum desirable because it was more resistant to jamming.Other advances at this time allowed an increase in the radio data rate. After 1945, commercial enterprises began to expand on this technology, realizing its potential benefits to consumers.

Spread spectrum technology evolved into the beginnings of the modern wireless LAN in 1971 with a University of Hawaii project called AlohNet. This project allowed seven computers around the various islands to communicate bidirectionally with a central hub on Oahu.

The university research on AlohNet paved the way for the first generation of modern wireless networking gear, which operated at the 901?928 MHz frequency range. Primarily used by the military, this phase of wireless development saw only limited consumer use, due to crowding within this frequency and the relatively low speed.

From this point, the 2.4 GHz frequency was defined for unlicensed use, so wireless technology began to emerge in this range and the 802.11 specification was established. This specification evolved into the widely accepted 802.11b standard, and continues to evolve into faster, more secure implementations of the technology.

The Standards

The standards based around wireless networking for PCs are established by the Institute of Electrical and Electronics Engineers (IEEE). LAN/MAN technology has been broadly assigned number 802, which is then broken down into working groups. Some of the most active wireless working groups include 802.15, designed for wireless personal area networks (Bluetooth), 802.16 which defines support for broadband wireless systems, and finally, 802.11, assigned to wireless LAN technology. Within the 802.11 definition, there are more specific definitions that are assigned letters. Here is a list of the most important 802.11 wireless LAN definitions:

802.11a
This definition provides wireless access on the 5 GHz band. It offers speeds of up to 54 MBps, but has not caught on, perhaps due to relatively higher priced equipment and short range.

802.11b
This is still the standard to which most people refer when talking about wireless networking. It establishes 11 MBps speeds on the 2.4 GHz band, and can have a range extending more than 500 meters.

802.11g
This standard has been established to provide higher data rates within the 2.4 GHz band and provides added security with the introduction of WiFi Protected Access, or WPA. 802.11g devices are now being deployed in place of 802.11b devices and have nearly reached mainstream acceptance.

802.11i
While still in the development phase, this standard seeks to resolve many of the security issues that have plagued 802.11b and provide a more robust system of authentication and encryption. At the time of this writing, the specification has not been finalized.

802.11n
802.11n is being touted as the high-speed answer to current wireless network speed shortcomings. With an operational speed of 100 Mbps, it will roughly double existing wireless transfer speeds, while maintaining backward compatibility with b and g. At the time of this writing, the specification is not complete; however, several vendors have released "pre-n" products, based on the early drafts of the specification