802.11 Wireless Networks: The Definitive Guide. The Definitive Guide. 2nd Edition (e-book) Będzin

As we all know by now, wireless networks offer many advantages over fixed (or wired) networks. Foremost on that list is mobility, since going wireless frees you from the tether of an Ethernet cable at a desk. But that's just the tip of the cable-free iceberg. Wireless networks are also more flexible, faster and easier for you to use, and more affordable to deploy and maintain.The de facto standard for wireless networking is the 802.11 protocol, which includes Wi-Fi (the wireless standard known as 802.11b) and its faster cousin, 802.11g. With easy-to-install 802.11 network hardware available everywhere you turn, the choice seems simple, and many people dive into wireless computing with less thought and planning than they'd give to a wired network. But it's wise to be familiar with both the capabilities and risks associated with the 802.11 protocols. And 802.11 Wireless Networks: The Definitive Guide, 2nd Edition is the perfect place to start.This updated edition covers everything you'll ever need to know about wireless technology. Designed with the system administrator or serious home user in mind, it's a no-nonsense guide for setting up 802.11 on Windows and Linux. Among the wide range of topics covered are discussions on:deployment considerationsnetwork monitoring and performance tuningwireless security issueshow to use and select access pointsnetwork monitoring essentialswireless card configurationsecurity issues unique to wireless networksWith wireless technology, the advantages to its users are indeed plentiful. Companies no longer have to deal with the hassle and expense of wiring buildings, and households with several computers can avoid fights over who's online. And now, with 802.11 Wireless Networks: The Definitive Guide, 2nd Edition, you can integrate wireless technology into your current infrastructure with the utmost confidence. Spis treści: 802.11 Wireless Networks: The Definitive Guide Foreword Preface Prometheus Untethered: The Possibilities of Wireless LANs Audience Overture for Book in Black and White, Opus 2 Major Changes from the First Edition Conventions Used in This Book Using Code Examples Safari Books Online How to Contact Us Acknowledgments 1. Introduction to Wireless Networking Why Wireless? Radio Spectrum: The Key Resource The ISM bands What Makes Wireless Networks Different Lack of Physical Boundary Dynamic Physical Medium Security A Network by Any Other Name... The Wonderful Thing About Standards... 2. Overview of 802.11 Networks IEEE 802 Network Technology Family Tree 802.11 Nomenclature and Design Types of Networks Independent networks Infrastructure networks Extended service areas Multi-BSS environments: virtual APs Robust security networks (RSNs) The Distribution System, Revisited Interaccess point communication as part of the distribution system Wireless bridges and the distribution system Network Boundaries 802.11 Network Operations Network Services Station services Distribution system services Confidentiality and access control Spectrum management services Mobility Support Designing Networks for Mobility Proprietary mobility systems 3. 802.11 MAC Fundamentals Challenges for the MAC RF Link Quality The Hidden Node Problem MAC Access Modes and Timing Carrier-Sensing Functions and the Network Allocation Vector Interframe Spacing Interframe spacing and priority Contention-Based Access Using the DCF Error Recovery with the DCF Using the retry counters Backoff with the DCF Fragmentation and Reassembly Frame Format Frame Control Duration/ID Field Duration: setting the NAV Frames transmitted during contention-free periods PS-Poll frames Address Fields Sequence Control Field Frame Body Frame Check Sequence Encapsulation of Higher-Layer Protocols Within 802.11 Contention-Based Data Service Broadcast and Multicast Data or Management Frames Unicast Frames Basic positive acknowledgment (final fragment) Fragmentation RTS/CTS RTS/CTS with fragmentation Powersaving Sequences Immediate response Deferred response Multirate Support Rate selection and fallback Frame Processing and Bridging Wireless Medium to Wired Medium (802.11 to Ethernet) Wired Medium to Wireless Medium (Ethernet to 802.11) Quality of Service Extensions 4. 802.11 Framing in Detail Data Frames Frame Control Duration Addressing and DS Bits Variations on the Data Frame Theme Applied Data Framing IBSS frames Frames from the AP Frames to the AP Frames in a WDS Encrypted frames Control Frames Common Frame Control Field Request to Send (RTS) Clear to Send (CTS) Acknowledgment (ACK) Power-Save Poll (PS-Poll) Management Frames The Structure of Management Frames Address fields Duration calculations Frame body Fixed-Length Management Frame Components Authentication Algorithm Number Authentication Transaction Sequence Number Beacon interval Capability Information Current AP Address Listen interval Association ID Timestamp Reason Code Status Code Management Frame Information Elements Service Set Identity (SSID) Supported Rates FH Parameter Set DS Parameter Set Traffic Indication Map (TIM) CF Parameter Set IBSS Parameter Set Country Hopping Pattern Parameters and Hopping Pattern Table Request Challenge Text Power Constraint Power Capability TPC Request TPC Report Supported Channels Channel Switch Announcement Measurement Request and Measurement Report Quiet IBSS DFS ERP Information Robust Security Network Extended Supported Rates Wi-Fi Protected Access (WPA) Types of Management Frames Beacon Probe Request Probe Response IBSS announcement traffic indication map (ATIM) Disassociation and Deauthentication Association Request Reassociation Request Association Response and Reassociation Response Authentication Action frame Frame Transmission and Association and Authentication States Frame Classes Class 1 frames Class 2 frames Class 3 frames 5. Wired Equivalent Privacy (WEP) Cryptographic Background to WEP Stream Cipher Security Cryptographic Politics WEP Cryptographic Operations WEP Data Processing WEP data transmission WEP key length Types of WEP keys Manual (static) versus automatic (dynamic) WEP WEP key numbering and storage WEP Encapsulation Problems with WEP Cryptographic Properties of RC4 Design Flaws of the WEP System Key Recovery Attacks Against WEP Key recovery defenses Dynamic WEP 6. User Authentication with 802.1X The Extensible Authentication Protocol EAP Packet Format EAP Requests and Responses Type code 1: Identity Type code 2: Notification Type code 3: NAK EAP Authentication Methods EAP Success and Failure A Sample EAP Exchange EAP Methods Cryptographic Methods LEAP Code 13: EAP-TLS Code 21: EAP-TTLS and Code 25: EAP-PEAP Noncryptographic EAP Methods Code 4: MD-5 Challenge Code 6: Generic Token Card Code 29: EAP-MSCHAP-V2 Code 18: EAP-SIM and Code 23: EAP-AKA Other Inner Authentication Methods Password Authentication Protocol (PAP) Challenge Handshake Authentication Protocol (CHAP) MS-CHAP, version 1 802.1X: Network Port Authentication 802.1X Architecture and Nomenclature 802.1X frame filtering EAPOL Encapsulation Addressing 802.1X on Wireless LANs Sample 802.1X Exchange on 802.11 Dynamic keying 7. 802.11i: Robust Security Networks, TKIP, and CCMP The Temporal Key Integrity Protocol (TKIP) TKIP Differences from WEP TKIP initialization vector use and key mixing TKIP sequence counter and replay protection The Michael integrity check and countermeasures TKIP Data Processing and Operation TKIP key mixing and key construction TKI P data transmission TKIP reception The Michael Integrity Check Michael data processing Michael countermeasures Counter Mode with CBC-MAC (CCMP) CCMP Data Processing CCMP data transmission CCMP reception Robust Security Network (RSN) Operations 802.11i Key Hierarchy Pairwise key hierarchy Group key hierarchy 802.11i Key Derivation and Distribution Updating pairwise keys: the four-way handshake Updating group keys: the group key handshake Mixing Encryption Types Key Caching 8. Management Operations Management Architecture Scanning Passive Scanning Active Scanning Scan Report Joining Authentication 802.11 Authentication Open-system authentication The legacy of shared-key authentication Defeating shared-key authentication Preauthentication 802.11 Preauthentication 802.11i Preauthentication and Key Caching Association Association Procedure Reassociation Procedure Power Conservation Power Management in Infrastructure Networks Unicast frame buffering and delivery using the Traffic Indication Map (TIM) Delivering multicast and broadcast frames: the Delivery TIM (DTIM) IBSS Power Management Timer Synchronization Infrastructure Timing Synchronization IBSS Timing Synchronization Spectrum Management Transmit Power Control (TPC) Basic operation of transmit power control Changes to the association process Changing the transmission power Dynamic Frequency Selection (DFS) Basic operation of DFS Quieting the channel Measuring Radar scan IBSS operation Action Frames Measurement Request frame Measurement Report TPC Request and Report Channel Switch Announcement 9. Contention-Free Service with the PCF Contention-Free Access Using the PCF PCF Operation Reserving the medium during the contention-free period The polling list Transmissions from the Access Point Contention-Free Period Duration Detailed PCF Framing Contention-Free End (CF-End) CF-End+CF-Ack CF Parameter Set Power Management and the PCF 10. Physical Layer Overview Physical-Layer Architecture The Radio Link Licensing and Regulation Frequency allocation and unlicensed frequency bands Other unlicensed bands Spread Spectrum Types of spread spectrum RF Propagation with 802.11 Signal Reception and Performance The Shannon limit Path Loss, Range, and Throughput Multipath Interference Inter-Symbol Interference (ISI) RF Engineering for 802.11 RF Components Antennas Amplifiers 11. The Frequency-Hopping (FH) PHY Frequency-Hopping Transmission 802.11 FH Details 802.11 Hop Sequences Joining an 802.11 Frequency-Hopping Network ISM Emission Rules and Maximum Throughput Effect of Interference Gaussian Frequency Shift Keying (GFSK) 2-Level GFSK 4-Level GFSK FH PHY Convergence Procedure (PLCP) Framing and Whitening Frequency-Hopping PMD Sublayer PMD for 1.0-Mbps FH PHY PMD for 2.0-Mbps FH PHY Carrier sense/clear channel assessment (CS/CCA) Characteristics of the FH PHY 12. The Direct Sequence PHYs: DSSS and HR/DSSS (802.11b) Direct Sequence Transmission Encoding in 802.11 Direct Sequence Networks Radio Spectrum Usage in 802.11 Direct Sequence Networks Channel energy spread Adjacent channel rejection and channel separation Maximum theoretical throughput Interference response Differential Phase Shift Keying (DPSK) Differential Binary Phase Shift Keying (DBPSK) Differential Quadrature Phase Shift Keying (DQPSK) The Original Direct Sequence PHY PLCP Framing and Processing DS Physical Medium Dependent Sublayer Transmission at 1.0 Mbps Transmission at 2.0 Mbps CS/CCA for the DS PHY Characteristics of the DS PHY Complementary Code Keying High Rate Direct Sequence PHY PLCP Framing and Scrambling HR/DSSS PMD Transmission at 1.0 Mbps or 2.0 Mbps Transmission at 5.5 Mbps with CCK Transmission at 11 Mbps with CCK Clear channel assessment Optional Features of the 802.11b PHY Characteristics of the HR/DSSS PHY 13. 802.11a and 802.11j: 5-GHz OFDM PHY Orthogonal Frequency Division Multiplexing (OFDM) Carrier Multiplexing Orthogonality Explained (Without Calculus) Guard Time Cyclic Extensions (Cyclic Prefixes) Windowing OFDM as Applied by 802.11a OFDM Parameter Choice for 802.11a Structure of an Operating Channel Subchannel modulation techniques Forward error correction with convolutional coding Subchannel interleaving Operating Channels OFDM PLCP Framing Preamble Header Data Trailer OFDM PMD Encoding and Modulation Radio Performance: Sensitivity and Channel Rejection Clear Channel Assessment Transmission and Reception Acknowledgment An example of OFDM encoding Characteristics of the OFDM PHY 14. 802.11g: The Extended-Rate PHY (ERP) 802.11g Components Compatibility Changes Protection ERP Physical Layer Convergence (PLCP) ERP-OFDM Framing Single-Carrier Framing with 802.11g PBCC coding DSSS-OFDM framing ERP Physical Medium Dependent (PMD) Layer Clear Channel Assessment (CCA) Reception Procedure Characteristics of the ERP PHY 15. A Peek Ahead at 802.11n: MIMO-OFDM Common Features Multiple-Input/Multiple-Output (MIMO) Channel Width MAC Efficiency Enhancements WWiSE MAC Enhancements Channels and radio modes Protection Aggregation, bursting, and acknowledgment The WWiSE MIMO PHY Structure of an operating channel Modulation and encoding Interleaver Space-time block coding Modulation rates MIMO and transmission modes WWiSE PLCP The SIGNAL-N field WWiSE PMD Characteristics of the WWiSE PHY TGnSync TGnSync MAC Enhancements Channels, radio modes, and coexistence Aggregation and bursting Protection Powersaving TGnSync PHY Enhancements Structure of a channel Basic MIMO rates Transmit modes Optional coding Optional short guard interval TGnSync Physical Transmission (PLCP and PMD) Legacy header High Throughput header High-Throughput training fields Data, tail, and padding TGnSync PMD Comparison and Conclusions 16. 802.11 Hardware General Structure of an 802.11 Interface Software-Defined Radios: A Digression A Few Words on 802.11 Hardware Implementations Learning more about cards: FCC filings Implementation-Specific Behavior Rebooting Interface Cards Scanning and Roaming Rate Selection Reading the Specification Sheet Sensitivity Comparison Delay Spread 17. Using 802.11 on Windows Windows XP Card Installation Third-party 802.1X stacks and the driver update process Cisco client software Choosing a Network Configuring Security Parameters and 802.1X Configuring EAP Methods EAP-TLS PEAP version 0 Clearing credentials from the registry SecureW2: TTLS with ZeroConfig WPA Configuration and Installation Windows 2000 Dynamic WEP Configuration Windows Computer Authentication How It Works 18. 802.11 on the Macintosh The AirPort Extreme Card Software Installation Configuring and Monitoring an AirPort Interface Basic configuration with the AirPort status icon Configuration with the System Preferences application Monitoring the wireless interface 802.1X on the AirPort Configuring EAP Methods TTLS configuration PEAP configuration The Keychain Adding to the keychain Troubleshooting 19. Using 802.11 on Linux PCMCIA Support on Linux PCMCIA Card Services Overview Interface names in Linux Hotplug system for automatic configuration PCMCIA Card Services Installation Monitoring the Cards The lights are not useful Troubleshooting Resource Conflicts IRQs I/O ports Linux Wireless Extensions and Tools Compiling and Installing Interface Configuration with Wireless Tools and iwconfig Finding networks Setting the network name Setting the network channel Setting the network mode and associating with an access point Setting the data rate Configuring static WEP keys Tuning 802.11 parameters Agere (Lucent) Orinoco Compiling and Installing PCMCIA configuration Doing it yourself Configuring the orinoco_cs Interface Atheros-Based cards and MADwifi Driver Architecture and the Hardware Access Layer (HAL) Requirements Building the Driver Using the Driver 802.1X on Linux with xsupplicant Requirements Compiling and Installing xsupplicant Configuring xsupplicant Pseudorandom number generation Connecting and Authenticating to a Network WPA on Linux 20. Using 802.11 Access Points General Functions of an Access Point Types of Access Points For the home: residential gateways For the office: enterprise access points For the large office: wireless switches Power over Ethernet (PoE) Types of PoE Selecting Access Points Are Access Points Really Necessary? Cisco 1200 Access Point Setting Up the 1200 Configuring Radio Interfaces Internetworking Configuring Security Configuring WPA-PSK Monitoring Troubleshooting Apple AirPort First-Time Setup The Management Interface Configuring the wireless interface Configuration of the LAN interface Access control 21. Logical Wireless Network Architecture Evaluating a Logical Architecture Mobility Defining mobility Security Performance Backbone Engineering Beacons, BSSIDs, and VLAN integration IP addressing Network Services DHCP Operating system login Client Integration Topology Examples Topology 1: The Monolithic Single-Subnet Network Mobility Address assignment through DHCP Security Backbone engineering Performance Client integration Topology 2: E.T. Phone Home or Island Paradise Mobility Security Performance Backbone Client Topology 3: Dynamic VLAN Assignment Mobility Security Performance Backbone Client Topology 4: Virtual Access Points Mobility Security Performance Backbone Client Choosing Your Logical Architecture 22. Security Architecture Security Definition and Analysis Wireless LAN Security Problems Your credentials, please: authentication Secrecy over the air: encryption Secrecy and integrity of the whole network: rogue access points Network integrity: traffic injection Network availability: denial of service Network integrity and availability: rogue clients Network integrity: traffic separation Authentication and Access Control Station Authentication and Association Link-Layer Authentication WPA Personal (preshared key) 802.1X-based EAP authentication Network Layer Authentication Integrating User Authentication Through RADIUS RADIUS authentication and Microsoft Windows databases Ensuring Secrecy Through Encryption Static WEP Dynamic WEP Keying with 802.1X Improved RC4-Based Encryption: TKIP CCMP: Encryption with AES Higher Layer Security Protocols (IPsec, SSL, and SSH) Selecting Security Protocols Applying Security in the Protocol Stack Compound binding vulnerabilities Encryption Security certifications Network support Choose Authentication Choosing an EAP method Authentication architecture Choose Encryption Multiple SSID support Rogue Access Points Detection Physical Location Disabling Rogue APs And now, a word from your lawyers 23. Site Planning and Project Management Project Planning and Requirements Network Requirements Coverage Requirements Coverage and physical installation restrictions Performance Requirements Exploring the coverage/quality trade-off and total area throughput Client limitations Realistic throughput expectations Number of users per access point Mobility Requirements Network Integration Requirements Physical integration Logical integration Physical Layer Selection and Design 2.4 GHz (802.11b/g) Channel Layout Limitations of the 2.4 GHz channel layout 5 GHz (802.11a) Channel Layout Mixed Channel Layouts (802.11a+b/g Networks) Planning Access-Point Placement The Building Constraints on AP placement Buildings in progress The Preliminary Plan The preliminary report Radio Resource Management and Channel Layout Refining and Testing the Plan Validation and test tools RF fingerprint collection Preparing the Final Report Using Antennas to Tailor Coverage Antenna Types Antenna cabling Antenna diversity Amplifiers: bring on the heat 24. 802.11 Network Analysis Network Analyzers 802.11 Network Analyzers Ethereal Compilation and Installation Setting the Wireless Interface for Monitor Mode Cisco Aironet cards Prism cards Orinoco cards Atheros-based cards Running Ethereal Capturing data Data Reduction Capture filters Display filters Using Ethereal for 802.11 Analysis Display filters Understanding the LLC header to isolate a protocol 802.11 Network Analysis Checklist Display Filter Primitives Excluding Beacon frames Isolating traffic from one station Isolating a protocol Common Troubleshooting Tasks Authentication troubleshooting Key distribution troubleshooting Performance troubleshooting Decrypting WEP traffic RADIUS analysis Other Tools Finding, Measuring, and Mapping Networks WEP Key Recovery Key recovery time estimates Authentication 25. 802.11 Performance Tuning 802.11 Performance Calculations Example Calculation Other components to a performance model Block acknowledgments Improving Performance Tunable 802.11 Parameters Radio Management Beacon interval RTS threshold Fragmentation threshold Retry limits Tuning Power Management Listen interval DTIM Period ATIM window Timing Operations Scan timing Timers related to joining the network Dwell time (frequency-hopping networks only) Summary of Tunable Parameters 26. Conclusions and Predictions Standards Work New Standards Task group E: quality of service extensions Task group K: radio resources Task group N: high-throughput (100+ Mbps) MIMO PHY More distant standards Related standards Current Trends in Wireless Networking Security Authentication protocols Admission control Rogue device control Deployment and Management Planning a network Backhaul Mini-"regulators and arbitrators Guest access Applications Location Voice Datacasting Protocol Architecture Federations and mobility Future protocols The End Glossary Index About the Author Colophon Copyright