Contents Wireless 101

Transcription

1 Wireless 101 Introduction... xxi Certified Wireless Network Administrator: Official Certification Guide Key Topics...xxi Course Objectives...xxii Course Overview...xxii Unit 1 Introduction to Wireless LANs...1 The Wireless LAN Market...7 History of Wireless LANs...7 Today s Wireless LAN Standards...8 Wireless LAN Specific Standards... 8 Activities Roles of Wireless LANs Access Role...12 Network Extension...14 Building-to-Building Connectivity Last Mile Data Delivery Mobility SO/HO Mobile Offices Activities i

2 Unit 2 RF Fundamentals...29 RF...33 RF Behaviors Gain Loss...35 Reflection...36 Refraction...37 Diffraction Scattering...39 Absorption...40 Activities VSWR...43 VSWR...44 VSWR Measurements...44 Effects of VSWR Solutions to VSWR...45 Activities Principles of Antennas...48 Wireless LAN Antenna Principles...48 LOS...49 Fresnel Zone...50 Obstructions...50 Antenna Gain...51 ii

3 IR...52 EIRP...53 Activities RF Mathematics...57 RF Power Calculations...57 Units of RF Power Measurement...58 Watts Milliwatt...59 Decibels Gain and Loss Measurements...60 dbm Examples...63 dbi Example...64 Accurate Measurements...65 Activities Summary...68 Quiz...69 Unit 3 Spread Spectrum Technology...75 Introducing Spread Spectrum...79 Narrowband Transmission Spread Spectrum Technology...81 Uses of Spread Spectrum...81 Wireless LANs...82 WPANs WMANs FCC Specifications...84 Activities FHSS...87 How FHSS Works...87 Effects of Narrowband Interference Frequency-Hopping Systems...89 Channels Dwell Time...90 Hop Time Dwell Time Limits FCC Rules Governing FHSS Systems...92 Activities iii

4 DSSS...96 How DSSS Works...96 Direct Sequence Systems...97 Channels Effects of Narrowband Interference FCC Rules Affecting DSSS Activities Comparing FHSS and DSSS Determining Factors Driving Spread Spectrum Technology Choices Narrowband Interference Present in the Environment Cost of FHSS and DSSS Systems Co-location for Failover, Load Balancing, and Added Capacity Equipment Compatibility and Availability Data Rate and Throughput Security Standards Support Activities Summary Quiz Unit 4 Wireless LAN Infrastructure Devices Access Points What Is a Wireless Access Point? Access Point Modes Root Mode Bridge Mode Repeater Mode Common Access Point Options Fixed or Detachable Antennas Advanced Filtering Capabilities Removable (Modular) Radio Cards Variable Output Power Varied Types of Wired Connectivity Access Point Configuration and Management Mounting Activities iv

5 Wireless Bridges What Is a Wireless Bridge? Wireless Bridge Modes Root Mode Nonroot Mode Access Point Mode Repeater Mode Common Bridge Options Fixed or Detachable Antennas Advanced Filtering Capabilities Removable (Modular) Radio Cards Variable Output Power Varied Types of Wired Connectivity Configuration and Management Activities Wireless Workgroup Bridges What Is a Wireless Workgroup Bridge? Common Options Configuration and Management Activities Wireless LAN Client Devices Types of Wireless Client Devices PCMCIA and Compact Flash Radio Cards Wireless Ethernet and Serial Converters USB Adapters PCI and ISA Adapters Configuration and Management Driver Installation Manufacturer Utilities Site Survey Tools Spectrum Analyzer Power and Speed Monitoring Tools Profile Configuration Utilities Link Status Monitor with Link Testing Functionality Common Utility Functionality Activities Lesson 5 Wireless Residential Gateways What Is a Wireless Residential Gateway? Common Options Configuration and Management Activities v

6 Lesson 6 Enterprise Wireless Gateways Enterprise Wireless Gateway Features Configuration and Management Activities Summary Quiz Unit 5 Antennas and Accessories RF Antennas RF Antenna Categories Omnidirectional (Dipole) Antennas Usage Semidirectional Antennas Usage Highly Directional Antennas Usage RF Antenna Concepts Polarization Practical Use Gain Beamwidth Free Space Path Loss The 6dB Rule Antenna Installation Placement Mounting Antenna Mounting Options Mounting Aesthetics Appropriate Use Orientation Alignment Safety Follow the Manual Do Not Touch When Power is Applied Use Professional Installers Keep Antennas Away from Metal Obstructions Keep Antenna Towers Away from Power Lines Use Grounding Rods Maintenance Activities vi

7 PoE Devices When to Use PoE Common PoE Options Single-Port DC Voltage Injectors Multiport DC Voltage Injectors Active Ethernet Switches PoE Compatibility Types of Injectors Types of Pickers/Taps Voltage and Pinout Standards Fault Protection Activities Wireless LAN Accessories Wireless LAN Accessory Types RF Amplifiers Common Options Configuration and Management Special Stipulations RF Attenuators Common Options Configuration and Management Lightning Arrestors Common Options Configuration and Maintenance RF Splitters Choosing an RF Splitter RF Connectors Choosing an RF Connector RF Cables RF Pigtail Adapter Cable Frequency Converters Bandwidth Control Units Test Kits Activities Summary Quiz vii

8 Unit 6 Wireless LAN Organizations and Standards FCC ISM and UNII Bands Advantages and Disadvantages of License-Free Bands ISM Bands MHz ISM Band GHz ISM Band GHz ISM Band UNII Bands Lower Band Middle Band Upper Band Power Output Rules PtMP PtP Activities IEEE IEEE Wireless LAN Standards IEEE IEEE b IEEE a IEEE g Activities Major Organizations WECA ETSI WLANA Activities Competing Technologies HomeRF Bluetooth IrDA Infrared Security Stability WLIF Activities Summary Quiz viii

9 Unit 7 The Network Architecture Locating a Wireless LAN Service Set Identifier Beacons Time Synchronization FH or DS Parameter Sets SSID Information TIM Supported Rates Passive Scanning Active Scanning Activities Authentication and Association Authentication Association States of Authentication and Association Unauthenticated and Unassociated Authenticated and Unassociated Authenticated and Associated Authentication Methods Open System Authentication Open System Authentication Process Shared Key Authentication Shared Key Authentication Process Authentication Security Shared Secrets and Certificates Emerging Wireless Security Solutions x and EAP VPN Solutions Activities Service Sets BSS ESS IBSS Roaming Standards Connectivity Reassociation VPN Use Layer 2 and Layer 3 Boundaries Load Balancing Activities ix

10 Power Management Features Power Management Modes CAM PSP Mode PSP Mode in a BSS PSP in an IBSS Activities Summary Quiz Unit 8 Physical Layers How Wireless LANs Communicate Wireless LAN Frames vs. Ethernet Frames Collision Handling Fragmentation DRS DCF PCF The PCF Process Activities Interframe Spacing Three Types of Spacing SIFS PIFS DIFS Slot Times The Communications Process Activities RTS/CTS Use of RTS/CTS on a Wireless Network Configuring RTS/CTS Activities Modulation Modulation and Spreading Code Types Activities Summary Quiz x

11 Unit 9 Troubleshooting Wireless LAN Installations Multipath Causes of Multipath Effects of Multipath Decreased Signal Amplitude Corruption Nulling Increased Signal Amplitude Troubleshooting Multipath Solutions for Multipath Activities Hidden Node Causes of Hidden Node Troubleshooting Hidden Node Solutions for Hidden Node Use RTS/CTS Increase Power to the Nodes Remove Obstacles Move the Node Activities Near/Far Causes of Near/Far Troubleshooting Near/Far Solutions for Near/Far Activities System Throughput Sources of Overhead Distance Hardware Spread Spectrum Technology User Count PCF Mode Other Factors Co-location Throughput (Theory vs. Reality) Theory: What Should Happen Reality: What Does Happen xi

12 Solutions for Co-location Throughput Problems Use Two Access Points Use a Equipment Issues with a Equipment Summary Activities Lesson 5 Types of Interference RF Interference Sources Narrowband All-Band Interference Weather Wind Stratification Lightning Adjacent Channel and Co-channel Interference Adjacent Channel Interference Co-channel Interference Activities Lesson 6 Range Considerations Issues that Affect RF Signal Range Transmission Power Antenna Type Environment Activities Summary Quiz Unit 10 Wireless LAN Security WEP What Is WEP? Why WEP Was Chosen WEP Keys Static WEP Keys Centralized Encryption Key Servers WEP Usage AES Filtering SSID Filtering MAC Address Filtering Circumventing MAC Filters xii

13 Protocol Filtering Activities Attacks on Wireless LANs Attack Methods Passive Attacks Active Attacks Jamming Man-in-the-Middle Attacks Activities Emerging Security Solutions Vendor Solutions WEP Key Management Wireless VPNs TKIP AES-Based Solutions Wireless Gateways x and EAP Activities Corporate Security Policy Components of a Corporate Security Policy Keep Sensitive Information Private Physical Security Wireless LAN Equipment Inventory and Security Audits Using Advanced Security Solutions Public Wireless Networks Limited and Tracked Access Activities Lesson 5 Security Recommendations WEP Cell Sizing User Authentication Security Needs Use Additional Security Tools Monitoring for Rogue Hardware Switches, Not Hubs Wireless DMZ Firmware and Software Updates Activities Summary Quiz xiii

14 Unit 11 Site Survey Fundamentals RF Site Surveys What Is a Site Survey? Activities Preparing for a Site Survey Presurvey Questions Facility Analysis Existing Networks Analysis Area Usage and Towers Analysis Purpose and Business Requirements Analysis Bandwidth and Roaming Requirements Analysis Available Resources Security Requirements Preparation Exercises Preparation Checklist Activities Site Survey Equipment Types of Site Survey Equipment Access Point PC Card and Utilities Laptops and PDAs Paper Outdoor Surveys Spectrum Analyzer Network Analyzer ( Sniffer ) Site Survey Kit Checklist Activities Conducting a Site Survey Indoor Surveys Outdoor Surveys Before You Begin RF Information Gathering Range and Coverage Patterns Data Rate Boundaries Documentation Throughput Tests and Capacity Planning Interference Sources Obstacle-Induced Signal Loss xiv

15 Wired Data Connectivity and AC Power Requirements Outdoor Antenna Placement Spot Checks Activities Lesson 5 Site Survey Reporting Preparing the Report Report Format Purpose and Business Requirements Methodology RF Coverage Areas Throughput Interference Problem Areas Drawings Hardware Placement and Configuration Information Additional Reporting Activities Summary Quiz Course Quiz Glossary Index Notes xv