2010 Cwna - Pp 5 - Ieee 802.11 Standards

CWNA®: Certified Wireless Network Administrator Official, Study Guide, David D. Coleman & David A. Westcott, Sybex

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IEEE 802.11 Standards

Chapter 05

Customized by: Brierley


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What Will I Learn?• We will cover the original 802.11 standard as well as its many

ratified enhancements, which have been incorporated in the current 802.11-2007 standard. Possible future enhancements. We will cover the following:

• All the defined PHY and MAC layer requirements of the original 802.11 Prime standard – All the approved enhancements to the 802.11 standard in the form of

ratified amendments, including higher data rates, different spread spectrum technologies, quality of service, and security

– Future capabilities and improvements as proposed in the 802.11 draft documents, including increased throughput, mesh networking, client management, and more



3

What Will I Learn?• Although many proprietary Wi-Fi solutions exist and will continue to exist

in the foreseeable future, standardization brings stability to the marketplace. The 802.11-2007 standard and all the future enhanced supplements provide a much needed foundation for vendors, network administrators, and end users.

• The CWNA exam will test your knowledge of the original 802.11-2007 standard and all the related technologies. Technologies discussed in the 802.11n draft amendment are also covered in the CWNA exam. Your primary focus should be on the 802.11-2007 standard.

• However, please understand that when 802.11 draft amendments become approved, they will be weighted heavier in future versions of the CWNA exam.



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Key Terms 802.11-2007 standard 802.1X Advanced Encryption Standard (AES) authentication autonomous access points Barker code Complementary Code Keying (CCK) Counter Mode with Cipher Block Chaining Message Authentication Code Protocol

(CCMP) data privacy data rate Direct sequence spread spectrum (DSSS) Distributed Coordination Function (DCF) distribution system distribution system DSSS-OFDM dynamic frequency selection (DFS) Enhanced Distributed Channel Access (EDCA) ERP-PBCC Extended Rate Physical (ERP) Extended Rate Physical DSSS (ERP-DSSS/CCK) Extended Rate Physical OFDM (ERP-OFDM) Extensible Authentication Protocol (EAP) fast basic service set transition (FT) fast secure roaming frequency hopping spread spectrum (FHSS) High Throughput (HT) High-Rate DSSS (HR-DSSS) Hybrid Coordination Function (HCF) Hybrid Coordination Function Controlled Channel Access (HCCA) Hybrid Wireless Mesh Protocol (HWMP) Industrial, Scientific, and Medical (ISM) band

Infrared (IR) Inter-Access Point Protocol (IAPP) lightweight access points mesh access point (MAP) mesh networking mesh point (MP) mesh point portal (MPP) mixed mode multiple-input multiple-output (MIMO) Open System authentication Orthogonal Frequency Division Multiplexing (OFDM) Packet Binary Convolutional Code (PBCC) Point Coordination Function (PCF) preshared keys (PSKs) protection mechanism quality of service (QoS) roaming robust security network (RSN) Shared Key authentication task groups Temporal Key Integrity Protocol (TKIP) transmit power control (TPC) Unlicensed National Information Infrastructure (UNII) Voice over IP (VoIP) Voice over Wi-Fi (VoWiFi) Wi-Fi Multimedia (WMM) Wi-Fi Protected Access 2 (WPA2) Wired Equivalent Privacy (WEP) wireless distribution system (WDS) WLAN controller



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Key Topics

• 5.1. Overview of the IEEE 802.11 Standard• 5.2. IEEE 802.11 Ratified Amendments• 5.3. IEEE 802.11 Draft Amendments



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Discussion TopicsIEEE 802.11 standardIEEE 802.11 ratified amendments

802.11b 802.11a802.11g802.11d802.11F802.11h802.11i802.11j802.11e802.11k802.11r

IEEE 802.11 draft amendments802.11m802.11n802.11p802.11s802.11T802.11u802.11v802.11w802.11y802.11z802.11aa



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Overview of the IEEE 802.11 Standard

The IEEE specifically defines 802.11 technologies at the Physical layer and the MAC sublayer of the Data-Link layer. The 802.11 standard does not address the upper layers of the OSI model, the exception being quality of service (QoS). The PHY Task Group worked in conjunction with the MAC Task Group to define the original 802.11 standard



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The PHY Task Group defined three original Physical layer specifications:

– Infrared (IR) – Frequency hopping spread spectrum (FHSS) – Direct sequence spread spectrum (DSSS)

Infrared (IR)

Infrared (IR) technology uses a light-based medium. Although it was indeed defined in the original 802.11 standard, the implementation is obsolete. More information website, at www.irda.org. Infrared devices are known as clause 16 devices.


http://www.irda.org/


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Frequency hopping spread spectrum (FHSS)

Radio frequency signals can be defined as narrowband signals or as spread spectrum signals. An RF signal is considered spread spectrum when the bandwidth is wider than what is required to carry the data. Frequency hopping spread spectrum (FHSS) is a spread spectrum technology that was first patented during World War II. Frequency hopping 802.11 radio cards is often called clause 14



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Direct sequence spread spectrum (DSSS) Direct sequence spread spectrum (DSSS) is another spread spectrum technology that is frequently used and easiest to implement. DSSS 802.11 radio cards are often known as clause 15 devices. As defined by 802.11 Prime, the frequency space in which either FHSS or DSSS radio cards can transmit is the license-free 2.4 GHz Industrial, Scientifc, and Medical (ISM) band.

The industrial, scientific and medical (ISM) radio bands



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DSSS 802.11 radio cards can transmit in channels subdivided from the entire 2.4 GHz to 2.4835 GHz ISM band. The IEEE is more restrictive for FHSS radio cards, which are permitted to transmit on 1 MHz subcarriers in the 2.402 GHz to 2.480 GHz range of the 2.4 GHz ISM band. It is important to understand that an 802.11 DSSS (clause 15) radio cannot communicate with an 802.11 (clause 14) FHSS radio.



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What about the speeds? Data rates defined by the original 802.11 standard were 1 Mbps and 2 Mbps regardless of which spread spectrum technology was used. A data rate is the number of bits per second the Physical layer carries during a single-frame transmission, millions of bits per second (Mbps). Data rate is the speed and not actual throughput. Because of medium access methods, aggregate throughput is typically one-half or less of the available data rate speed.



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IEEE 802.11 Ratified Amendments

At the time your book was written, 11 amendments to the standard had been ratified and published. In 2007, the IEEE consolidated the majority of the ratified amendments with the original standard, creating a single document that is now published as the 802.11-2007 standard. The Wi-Fi Alliance and most WLAN professionals still refer to the ratified amendments by name.



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802.11bThe Physical layer medium that is defined by 802.11b is High-Rate DSSS (HR-DSSS). The frequency space in which 802.11b radio cards can operate is the unlicensed 2.4 GHz to 2.4835 GHz ISM band. 802.11b radio cards are known as clause 18 devices. The 802.11b amendment specifies the use of only a DSSS-type physical medium and does not specify FHSS. Because a good portion of the legacy 802.11 deployments used FHSS, 802.11b radio cards are not backward compatible with those systems and cannot be used. However, 802.11b clause 18 radio cards are backward compatible with DSSS clause 15 devices.

Many of the legacy devices did not undergo any compatibility testing such as that provided by the Wi-Fi Alliance.



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802.11a

The engineers in the Task Group a (TGa) set out to define how 802.11 technologies would operate in newly allocated Unlicensed National Information Infrastructure (UNII) frequency bands. 802.11a radio cards can transmit in three different 100 MHz unlicensed frequency bands in the 5 GHz range. A total of 12 channels are available in the three UNII bands. All aspects of the 802.11a ratified amendment can now be found in clause 17 of the 802.11-2007 standard. These devices are required to support data rates of 6, 12, and 24 Mbps with a maximum of 54 Mbps. Customized by: Brierley


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802.11a

With the use of a spread spectrum technology called Orthogonal Frequency Division Multiplexing (OFDM), data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps are supported

in most manufacturers’ radio cards.

Note: 802.11a radio cards cannot communicate with 802.11 legacy, 802.11b, or 802.11g radio cards for two reasons:

• First, 802.11a radio cards use a different spread spectrum technology than 802.11 legacy or 802.11b devices.

• Second, 802.11a devices transmit in the 5 GHz UNII bands, while the 802.11/802.11b/802.11g devices operate in the 2.4 GHz ISM band.

Many enterprise wireless deployments run both 802.11a and 802.11b/g networks simultaneously



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802.11gThe IEEE defines 802.11g cards as clause 19 devices, which transmit in the 2.4 GHz to 2.4835 GHz ISM frequency band. Clause 19 defines a technology called Extended Rate Physical (ERP). All aspects of the 802.11g ratified amendment can now be found in clause 19 of the 802.11-2007 standard.



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What Is the Difference between ERP-DSSS/CCK, DSSS, and HR-DSSS?

From a technical viewpoint, there is no difference between ERP-SSS/CCK and DSSS and HR-DSSS. A key point of the 802.11g amendment was to maintain backward compatibility with older 802.11 (DSSS only) and 802.11b radios while at the same time achieving higher data rates. 802.11g devices (clause 19 radios) use ERP-OFDM for the higher data rates. ERP-DSSS/CCK is effectively the same technology as the DSSS that is used by legacy 802.11 devices (clause 15 radios), and HR-DSSS that is used by 802.11b devices (clause 18 radios).



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802.11dThe original 802.11 standard was written for compliance with the regulatory domains of the United States, Japan, Canada, and Europe.

Regulations in other countries might define different limits on allowed frequencies and transmit power. The 802.11d amendment, which was published as IEEE Std. 802.11d-2001, added requirements and definitions necessary to allow 802.11 WLAN equipment to operate in areas not served by the original standard. Country code information is delivered in fields inside two wireless frames called beacons and probe responses. This information is then used by 802.11d-compliant devices to ensure that they are abiding by a particular country’s frequency and power rules.



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802.11FThe original published 802.11 standard mandated that vendor access points support roaming. The use of an uppercase letter designation for an IEEE task group, such as that in IEEE Task Group F, indicates that this amendment (F) is considered a recommended practice and not part of the 802.11-2007 standard. The amendment was never ratified and was withdrawn in February 2006.



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802.11hPublished as IEEE Std. 802.11h-2003, this amendment defines Mechanisms for dynamic frequency selection (DFS) and transmit power control (TPC). It was originally proposed to satisfy regulatory requirements for operation in the 5 GHz band in Europe and to detect and avoid Interference with 5 GHz satellite and radar systems. In the United States and Europe, radar detection and avoidance is required in both the UNII-2 and UNII-2 Extended bands. The 802.11h amendment effectively introduced two major enhancements: more frequency space with the introduction of the UNII-2 Extended band, and radar avoidance and detection technologies. All aspects of the 802.11h ratified amendment can now be found in clauses 11.8 and 11.9 of the 802.11-2007 standard.



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802.11iTwo key components of any wireless security solution are data privacy (encryption) and authentication (identity verifcation). For seven years (1997 to 2004), the only defined method of encryption in an 802.11 network was the use of 64-bit static encryption called Wired Equivalent Privacy (WEP). WEP encryption has long been cracked and is not considered an acceptable means of providing data privacy. Stronger encryption method called Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP), which uses the Advanced Encryption Standard (AES) algorithm. 802.11i defines two methods of authentication using either:

– IEEE 802.1X authorization framework or – preshared keys (PSKs)

The Wi-Fi Alliance also has a certification known as Wi-Fi Protected Access 2 (WPA2), which is a mirror of the IEEE 802.11i security amendment it is fully compliant with 802.11i. All aspects of the 802.11i ratified security amendment can now be found in clause 8 of the 802.11-2007 standard. Customized by: Brierley


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802.11jThe main goal set out by the IEEE Task Group j (TGj) was to obtain Japanese regulatory approval by enhancing the 802.11 MAC and 802.11a PHY to additionally operate in Japanese 4.9 GHz and 5 GHz bands.

The 802.11j amendment was approved and published as IEEE Std. 802.11j-2004.



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802.11eSince the adoption of the original 802.11 standard, there have not been any adequate quality of service (QoS) procedures defined for the use of time-sensitive applications such as Voice over IP (VoIP).

Voice over Wireless IP (VoWIP) is also known as Voice over Wireless LAN (VoWLAN) and as Voice over Wi-Fi (VoWiFi).

The terminology used by most vendors and the CWNP program is Voice over Wi-Fi (VoWiFi).



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802.11k

The goal of the 802.11 Task Group k (TGk) is to provide a means of radio resource measurement (RRM). This amendment calls for measurable client statistical information in the form of requests and reports for the Physical layer 1 and the MAC sublayer of the Data-Link layer 2. 802.11k defines mechanisms in which client station resource data is gathered and processed by an access point or WLAN controller (WLAN controllers. The 802.11k amendment is not part of the 802.11-2007 standard but it was ratified in June of 2008 and is published as IEEE 802.11k-2008.



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802.11rThe 802.11r amendment is known as the fast basic service set transition (FT) amendment. The technology is more often referred to as fast secure roaming because it defines faster handoffs when roaming occurs between cells in a WLAN using the strong security defined by a robust secure network (RSN). The 802.11r amendment is not part of the 802.11-2007 standard. However, it was ratified in July of 2008 and is published as IEEE 802.11r-2008. Tactical enterprise deployments of this technology will be extremely important for providing more-secure communications for VoWiFi. The details of this technology will soon be a heavily tested topic on the CWSP exam.



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IEEE 802.11 Draft AmendmentsWhat does the future hold in store for us with 802.11 wireless networking?

The draft amendments are a looking glass into the enhancements and capabilities that might be available in the near future for 802.11 wireless networking devices:

– Greater throughput, – client control, – improved roaming, – mesh networking, and – more await us on the wireless horizon.

The CWNA exam (PW0-104) currently covers all of the technologies defined in the ratified amendments that are now part of the 802.11-2007 standard. You will not be tested on the draft amendments except for 802.11n, because most enterprise vendors are already implementing 802.11n technology, and the Wi-Fi Alliance is certifying the technology.



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Access Point Dual Radio Cards



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Glimpse into the future of more-advanced Wi-Fi products



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802.11m

Often referred to as 802.11 housekeeping because of its mission of clarifying and correcting the 802.11 standard.

Unless you are a member of TGm, this amendment is of little significance.



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802.11n

The objective of the 802.11n amendment is to increase the throughput in both the:

– 2.4 GHz and – 5 GHz frequency bands.

The 802.11n amendment defines a new operation known as HighThroughput (HT), which provides PHY and MAC enhancements to support throughput of 100 Mbps or greater.



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802.11pThe mission of the 802.11 Task Group p (TGp) is to define enhancements to the 802.11 standard to support Intelligent Transportation Systems (ITS) applications.

Data exchanges between high-speed vehicles will be possible in the licensed ITS band of 5.9 GHz. Additionally, communications between vehicles and roadside infrastructure will be supported in the 5 GHz bands, specifcally the 5.850 GHz to 5.925 GHz band within North America



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802.11s

The 802.11s amendment proposes the use of a protocol for adaptive, autoconfguring systems that support broadcast, multicast, and unicast traffc over a multihop mesh WDS.

A mesh point portal (MPP) is a device that acts as a gateway to one or more external networks

such as an 802.3 wired backbone.



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802.11TThe 802.11T draft is also called Wireless Performance Prediction (WPP).

Its final objective is consistent and universally accepted WLAN measurement practices.

These 802.11 performance benchmarks and methods could be used by independent test labs, manufacturers, and even end users.



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802.11uThe 802.11T draft is also called Wireless Performance Prediction (WPP). Its final objective is consistent and universally accepted WLAN measurement practices.

These 802.11 performance benchmarks and methods could be used by independent test labs, manufacturers, and even end users.



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802.11v

While 802.11k defnes methods of retrieving information from client stations, 802.11v will give us the ability to configure client stations wirelessly from a central point of management.

The main goal of the IEEE Task Group v (TGv) is for WLAN infrastructure (access points and wireless switches) to take improved control of wireless client.



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802.11w

Wireless Network

The IEEE Task Group w (TGw) is working on a “protected” management frame amendment with a goal of delivering management frames in a secure manner.

The end result will hopefully prevent some of the layer 2 denial-of-service attacks that currently exist.



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802.11yThe objective of the IEEE Task Group y (TGy) is to standardize the mechanisms required to allow high-powered, shared 802.11 operation with other users in the 3650 MHz–3700 MHz band in the United States and possibly other frequencies in other countries.



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802.11zThe purpose of IEEE Task Group z (TGz) is to establish and standardize a Direct Link Setup (DLS) mechanism to allow operation with non-DLS-capable access points.

In most WLAN environments, all frame exchanges between client stations that are associated to the same access point must pass through the access point.

DLS allows client stations to bypass the access point and communicate with direct frame exchanges. Some of the earlier amendments have defined DLS communications.



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802.11aaThe 802.11aa amendment specifies enhancements to the 802.11 Media Access Control (MAC) for robust audio video streaming, while maintaining coexistence with other types of traffic.



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Roaming



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Roaming-distribution System Medium



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Unlicensed National Information Infrastructure



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Mesh Points, Mesh Aps and Mesh Portal



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Key Terms• 802.1X• Advanced Encryption Standard (AES)• authentication• autonomous access points• Barker code• Complementary Code Keying (CCK)• Counter Mode with Cipher Block

Chaining Message Authentication Code Protocol

• (CCMP)• data privacy• data rate• Direct sequence spread spectrum

(DSSS)• Distributed Coordination Function

(DCF)• distribution system• distribution system• DSSS-OFDM• dynamic frequency selection (DFS)• Enhanced Distributed Channel Access • (EDCA)• ERP-PBCC• Extended Rate Physical (ERP)• Extended Rate Physical DSSS

• (ERP-DSSS/CCK)• Extended Rate Physical OFDM • (ERP-OFDM)• Extensible Authentication Protocol

(EAP)• fast basic service set transition (FT)• fast secure roaming• frequency hopping spread spectrum

(FHSS)• High Throughput (HT)• High-Rate DSSS (HR-DSSS) Hybrid

Coordination Function (HCF)• Hybrid Coordination Function

Controlled • Channel Access (HCCA)• Hybrid Wireless Mesh Protocol

(HWMP)• Industrial, Scientific, and Medical • (ISM) band• Infrared (IR)• Inter-Access Point Protocol (IAPP)• lightweight access points• mesh access point (MAP)• mesh networking• mesh point (MP)

• mesh point portal (MPP)• mixed mode• multiple-input multiple-output

(MIMO)• Open System authentication• Orthogonal Frequency Division • Multiplexing (OFDM)• Packet Binary Convolutional Code

(PBCC)• Point Coordination Function (PCF)• preshared keys (PSKs)• protection mechanism• quality of service (QoS)• roaming• robust security network (RSN)• Shared Key authentication• task groups• Temporal Key Integrity Protocol (TKIP)• transmit power control (TPC)• Unlicensed National Information • Infrastructure (UNII)• Voice over IP (VoIP)



46

What Did I Learn?

We covered the original 802.11 standard as well as its many ratified enhancements, which have been incorporated in the current 802.11-2007 standard. Possible future enhancements. We will cover the following:

– All the defined PHY and MAC layer requirements of the original 802.11 Prime standard

– All the approved enhancements to the 802.11 standard in the form of ratified amendments, including higher data rates, different spread spectrum technologies, quality of service, and security

– Future capabilities and improvements as proposed in the 802.11 draft documents, including increased throughput, mesh networking, client management, and more



47

What Did I Learn?• Although many proprietary Wi-Fi solutions exist and will continue to exist

in the foreseeable future, standardization brings stability to the marketplace. The 802.11-2007 standard and all the future enhanced supplements provide a much needed foundation for vendors, network administrators, and end users.

• The CWNA exam will test your knowledge of the original 802.11-2007 standard and all the related technologies. Technologies discussed in the 802.11n draft amendment are also covered in the CWNA exam. Your primary focus should be on the 802.11-2007 standard.

• However, please understand that when 802.11 draft amendments become approved, they will be weighted heavier in future versions of the CWNA exam.



48

END

Ch 05 - IEEE 802.11 StandardsNext

Ch 06 - Wireless Networks & Spread Spectrum Technologies


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2010 Cwna - Pp 5 - Ieee 802.11 Standards

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