A Network by Any Other Name...

Wireless networking is a hot industry segment. Several wireless technologies have been targeted primarily for data transmission. Bluetooth is a standard used to build small networks between peripherals: a form of "wireless wires," if you will. Most people in the industry are familiar with the hype surrounding Bluetooth, though it seems to have died down as real devices have been brought to market. In the first edition, I wrote that I have not met many people who have used Bluetooth devices, but it is much more common these days. (I use a Bluetooth headset on a regular basis.)

Post-second-generation (2.5G) and third-generation (3G) mobile telephony networks are also a familiar wireless technology. They promise data rates of megabits per cell, as well as the "always on" connections that have proven to be quite valuable to DSL and cable modem customers. After many years of hype and press from 3G equipment vendors, the rollout of commercial 3G services is finally underway. 2.5G services like GPRS, EDGE, and 1xRTT are now widely available, and third-generation networks based on UMTS or EV-DO are quickly being built. (I recently subscribed to an unlimited GPRS service to get connected during my train trips between my office and my home.) Many articles quote peak speeds for these technologies in the hundreds of kilobits per second or even megabits, but this capacity must be shared between all users in a cell. Real-world downstream speeds are roughly comparable to dial-up modem connections and cannot touch an 802.11 hot spot.

This is a book about 802.11 networks. 802.11 goes by a variety of names, depending on who is talking about it. Some people call 802.11 wireless Ethernet, to emphasize its shared lineage with the traditional wired Ethernet (802.3). A second name which has grown dramatically in popularity since the first edition of this book is Wi-Fi, from the interoperability certification program run by the Wi-Fi Alliance, the major trade assocation of 802.11 equipment vendors. The Wi-Fi Alliance, formerly known as the Wireless Ethernet Compatibility Alliance (WECA), will test member products for compatibility with 802.11 standards.[*] Other organizations will perform compatibility testing as well; the University of New Hampshire's InterOperability Lab (IOL) recently launched a wireless test consortium.

[*] More details on the Wi-Fi Alliance and its certification program can be found at http://www.wi-fi.org/.

The Wonderful Thing About Standards...

Several standards groups are involved in 802.11-related standardization efforts because 802.11 cuts across many formerly distinct boundaries in networking. Most of the effort remains concentrated in the IEEE, but important contributions to wireless LAN standards have come from several major locations.

The first is the Institute of Electronics and Electrical Engineers (IEEE). In addition to its activities as a professional society, the IEEE works on standardizing electrical equipment, including several types of communication technology. IEEE standardization efforts are organized by projects, each of which is assigned a number. By far the most famous IEEE project is the IEEE 802 project to develop LAN standards. Within a project, individual working groups develop standards to address a particular facet of the problem. Working groups are also given a number, which is written after the decimal point for the corresponding projects. Ethernet, the most widely used IEEE LAN technology, was standardized by the third working group, 802.3. Wireless LANs were the eleventh working group formed, hence the name 802.11.

Within a working group, task groups form to revise particular aspects of the standard or add on to the general area of functionality. Task groups are assigned a letter beneath the working group, and the document produced by a task group combines the project and working group number, followed by the letter from the task group. (Some letters that are subject to easy confusion with letters, such as the lowercase "l," are not used.) In wireless networking, the first task group to gain wide recognition was Task Group B (TGb), which produced the 802.11b specification. Table 1-3 is a basic listing of the different 802.11 standards.

Interestingly enough, the case of the letter in a standards revision encodes information. Lowercase letters indicate dependent standards that cannot stand alone from their parent, while uppercase letters indicate full-fledged standalone specifications.

802.11b adds a new clause to 802.11, but cannot stand alone, so the "b" is written in lowercase. In constrast, standards like 802.1Q and 802.1X are standalone specifications that are completely self-contained in one document, and therefore use uppercase letters.

At periodic intervals, the additions from dependent task groups will be "rolled up" into the main parent specification. The initial revision of 802.11 came out in 1997. Minor changes to the text were released as 802.11-1999, which was the baseline standard for quite some time. The most recent rollup is 802.11-2003.

Table 1-3. standards

IEEE standard

Notes

802.11

First standard (1997). Specified the MAC and the original slower frequency-hopping and direct-sequence modulation techniques.

802.11a

Second physical layer standard (1999), but products not released until late 2000.

802.11b

Third physical layer standard (1999), but second wave of products. The most common 802.11 equipment as the first book was written.

TGc

Task group that produced a correction to the example encoding in 802.11a. Since the only product was a correction, there is no 802.11c.

802.11d

Extends frequency-hopping PHY for use across multiple regulatory domains

TGe (future 802.11e)

Task group producing quality-of-service (QoS) extensions for the MAC. An interim snapshot called Wi-Fi Multi-Media (WMM) is likely to be implemented before the standard is complete.

802.11F

Inter-access point protocol to improve roaming between directly attached access points

802.11g

Most recently standardized (2003) PHY for networks in the ISM band.

802.11h

Standard to make 802.11a compatible with European radio emissions regulations. Other regulators have adopted its mechanisms for different purposes.

802.11i

Improvements to security at the link layer.

802.11j

Enhancements to 802.11a to conform to Japanese radio emission regulations.

TGk (future 802.11k)

Task group to enhance communication between clients and network to better manage scarce radio use.

TGm

Task group to incorporate changes made by 802.11a, 802.11b, and 802.11d, as well as changes made by TGc into the main 802.11 specification. (Think "m" for maintenance.)

TGn (future 802.11n)

Task group founded to create a high-throughput standard. The design goal is throughput in excess of 100 Mbps, and the resulting standard will be called 802.11n.

TGp (future 802.11p)

Task group adopting 802.11 for use in automobiles. The initial use is likely to be a standard protocol used to collect tolls.

TGr (future 802.11r)

Enhancements to roaming performance.

TGs (future 802.11s)

Task group enhancing 802.11 for use as mesh networking technology.

TGT (future 802.11T)

Task group designing test and measurement specification for 802.11. Its result will be standalone, hence the uppercase letter.

TGu (future 802.11u)

Task group modifying 802.11 to assist in interworking with other network technologies.

When it became clear that authentication on wireless networks was fundamentally broken, the IEEE adopted several authentication standards originally developed by the Internet Engineering Task Force (IETF). Wireless LAN authentication depends heavily on protocols defined by the IETF.

The Wi-Fi Alliance is a combination of a trade association, testing organization, and standardization organization. Most of the Wi-Fi Alliance's emphasis is on acting as a trade association for its members, though it also well-known for the Wi-Fi certification program. Products are tested for interoperability with a testbed consisting of products from major vendors, and products that pass the test suite are awarded the right to use the Wi-Fi mark.

The Wi-Fi Alliance's standardization efforts are done in support of the IEEE. When the security of wireless networks was called into question, the Wi-Fi Alliance produced an interim security specification called Wi-Fi Protected Access (WPA). WPA was essentially a snapshot of the work done by the IEEE security task group. It is more of a marketing standard than a technical standard, since the technology was developed by the IEEE. However, it serves a role in accelerating the development of secure wireless LAN solutions.

Introduction to Wireless Networking

Overview of 802.11 Networks

11 MAC Fundamentals

11 Framing in Detail

Wired Equivalent Privacy (WEP)

User Authentication with 802.1X

11i: Robust Security Networks, TKIP, and CCMP

Management Operations

Contention-Free Service with the PCF

Physical Layer Overview

The Frequency-Hopping (FH) PHY

The Direct Sequence PHYs: DSSS and HR/DSSS (802.11b)

11a and 802.11j: 5-GHz OFDM PHY

11g: The Extended-Rate PHY (ERP)

A Peek Ahead at 802.11n: MIMO-OFDM

11 Hardware

Using 802.11 on Windows

11 on the Macintosh

Using 802.11 on Linux

Using 802.11 Access Points

Logical Wireless Network Architecture

Security Architecture

Site Planning and Project Management

11 Network Analysis

11 Performance Tuning

Conclusions and Predictions





802.11 Wireless Networks The Definitive Guide
802.11 Wireless Networks: The Definitive Guide, Second Edition
ISBN: 0596100523
EAN: 2147483647
Year: 2003
Pages: 179
Authors: Matthew Gast
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