controller-based lan fundamentals - gbv
TRANSCRIPT
Controller-Based LAN Fundamentals
Jeff Smith, Jake Woodhams, Robert Marg
Cisco Press 800 East 96th Street
Indianapolis, IN 46240
vii
Contents Introduction xvi
Chapter 1 The Need for Controller-Based Wireless Networks 1
Why Wireless LAN Controllers Were Created 4
Why You Need to Use a Wireless LAN Controller 5
Controller-Based WLAN Functional and Elemental Architecture 6
Autonomous AP Issues and the WLC Remedy 9
Problem: WLAN APs Are Difficult to Deploy 9
Problem: WLANs Are Not Secure 10
Problem: Infrastructure Device Configuration and Scaling 10
Problem: Autonomous AP Costs for Configuring Each AP 11
Problem: Autonomous AP Costs for Keeping Each AP's Software Up to Date 11
Problem: RF Expertise and Configuration Challenges 12
Mobility Applications Enabled by Controller-Based WLANs 12
WLANs Do Not Provide the Performance and Robustness Needed
for Use as a Primary Access Network 13
Summary 13
Chapter 2 Wireless LAN Protocols 15
Understanding the Relevant Standards 15
Wi-Fi Alliance 16
Cisco Compatible Extensions 18
IETF 18
The Physical Layer 19
Physical Layer Concepts 19
CAPWAP 21
CAPWAP Versus LWAPP 22
CAPWAP Protocol Fundamentals 23
CAPWAP Terminology 23
CAPWAP Control Messages 24
CAPWAP Data Messages 24
CAPWAP State Machine 24
CUWN Implementation of the CAPWAP Discovery 26
CAPWAP Transport 28
CAPWAP MAC Modes 29
Split MAC Mode 29
Local MAC Mode 30
viii Controller-Based Wireless LAN Fundamentals
Summary of CAPWAP 31 Packet Flow in the Cisco Unified Wireless Network 32
CAPWAP Control 32 CAPWAP Data Path: Centrally Bridged Traffic 32 CAPWAP Data Path: Locally Bridged Traffic 33 Summary of Packet Flow 34
Summary 34 References 34
Chapter 3 802.11n 37
IEEE 802.1 In Standard 38 802.1 In MAC 39 Other 802.11 Standards Used with 802.11n 41 Frequency Bands Supported by 802.1 In 42
Antenna Arrays 42 Transmit Beam Forming (TxBF) 43 Beam Steering 44 Spatial Multiplexing 45 Transmit Diversity 47
Multiple Input, Multiple Output (MIMO) 48 Multipath 48 MIMO Nomenclature 49 Receiver Diversity 51 Branch Selection Diversity 52
Branch-Combining Diversity 53
Diversity Antenna Array, Type, Orientation, and Spacing 55
Transmit Beam-Forming Types 56
Legacy Beam Forming 57
Implicit Beam Forming 57
Explicit Beam Forming 57
MIMO Antenna Array Coverage and Placement 58 Coding 58
Binary Convolutional Coding (BCC) 59 Low-Density Parity Checking (LDPC) 59
HT PHY and Operation 60 HT Mixed 61 HT-Greenfield Format 61
Channel Bonding/40-MHz-Wide Channels 63 Protection 64
Power Management 66
ix
Packet Aggregation 67 Bursting/Block ACK (BACK) 69 Short Guard Interval (Gl) 69 Reduced Inter-Frame Spacing (RIFS) 69
Reverse Direction Protocol (RDP) 71 Modulation and Coding Schemes (MCS) 71 Configuration Requirements to Obtain HT Rates 73 Predicting 802.11 Link Performance 76 Summary 77
Chapter 4 Cisco Unified Wireless LAN Security Fundamentals 79
Understanding WLAN Security Challenges 80 Vulnerabilities Inherent to the Radio Transmission Medium 80 Physical Containment Problem 81
Unlicensed Radio Spectrum Problem 81
Vulnerabilities Inherent to the Standards Definitions 82
Authentication and Encryption Weaknesses 82
Unauthenticated Management Frames 83
Vulnerabilities Inherent to Mobility 84 Misconfigured Wireless Devices and Clients 85 Rogue Access Points and Devices 85 Readily Available Profiling and Attack Tools 86
Addressing the WLAN Security Challenges 86 Background on Strong Authentication and Privacy 87
How WEP Encryption Works 87
How WEP Is Broken 90
802.11 Authentication 90
Addressing the Strong Authentication and Privacy Challenges 92
Authentication Framework 94
Authentication Algorithm 96
Data Privacy and Integrity 102
Alternative Approaches to Authentication and Data Privacy 113 Rogue Access Point Detection and Wireless Intrusion Prevention 114 Secure Management and Security Policies 118
Summary 119 References 119
Chapter 5 Design Considerations 123
100 Percent Wireless Access Layer 123 Client Device Power 124 RF Vulnerability 124 Volume of Network Traffic 125
x Controller-Based Wireless LAN Fundamentals
Increased and Difficult WLAN Coverage Requirements 125 Elevators 126
External Bleed-Through 126
Elevator Shaft Coverage 127
Access Point Installed in Elevator Car 127
Continuous Availability and Outage Planning 128
Power Loss 129
Equipment Failures: APs, WLCs, and Backhaul Network 129
RF Interference 131
Denial of Service Attacks 131
Business Operation Continuity in the WLAN Era 132
Power Conservation 132 Flexibility 133 WLAN Capacity 133 Summary 134
Chapter 6 Cisco Unified Wireless LAN Architectures 135 Cisco Unified Wireless LAN Architecture Review 135 Architectural Flexibility, Scalability, and Resiliency 137
Architectural Flexibility 137 Architectural Resiliency 139 N.1WLC Redundancy 141
N:N WLC Redundancy 141
N:N:1WLC Redundancy 142
Architectural Scalability 143
Mobility 143
Mobility Domains 147
Campus Architectures 149 Enterprise Wiring Closet Deployment 149 Enterprise Distribution Layer Deployment 150 Data Center or Services Block Deployments 151 Campus HREAP 152
Branch Architectures 153 Distributed Branch Controller Placement 153 Centralized Controller Placement with HREAP 154 Office Extend AP (OEAP) 155
Summary 155
Chapter 7 Troubleshooting 157 Tools for Troubleshooting 802.11 Wireless Networks 158
Wireless LAN Controller Command-Line Interface 159 Wireless Control System (WCS) 160 Wireless Protocol Analyzer 160 Spectrum Analyzers 162
Isolating Issues on the Cisco Unified Wireless Network 163 Protocol/Network Issues 164 LWAPP/CAPWAP Discovery Process 165 Troubleshooting the LWAPP CAPWAP Discovery Process 167 Network Considerations 170 Client Troubleshooting 170 Troubleshooting Client Issues Using the WLC СЫ 171 Troubleshooting Client Issues Using WCS 172 Common Client Problems and Solutions 176
The Wireless Medium: Troubleshooting Performance-Related Issues 180 Coverage and Interference Issues 180 Detecting, Isolating, and Solving Coverage Issues 181 Detecting, Isolating, and Solving Interference Issues 183
Troubleshooting Advanced Wireless LAN Services 186 Voice over WLAN 186 Voice over WLAN Challenges 187 Troubleshooting VoWLAN 188 Location Troubleshooting 191 Troubleshooting Location Accuracy 192
Summary 194 Chapter 8 Introduction to WCS 195
Designing Wireless Networks with WCS 196 WCS Requirements 197 WCS Interface 197 WCS Monitoring 199 Maps 199 Controllers and AP Monitor 204 Client Monitoring 206 WCS Reporting 209 WCS Configuration 210 Controller Configuration Templates 212 WCS Configuration and Template Auditing 216 AP Configuration Templates 220
xii Controller-Based Wireless LAN Fundamentals
WCS Services 223 WCS Administration 224
Role-Based Access Control (RBAC) 225
WCS Virtual Domains 228
WCS License Center 235
Additional Benefits of WCS: Planning and Calibration Tools 236 WCS Planning 236 WCS Calibration 238
Summary 241
Chapter 9 Next-Generation Advanced Topics: Multicast 243
Multicast 244 Multicast Definition 245 Multicast Addressing 246
Multicast Forwarding 249
Multicast Distribution Trees 249
Protocol Independent Multicasting (PIM) 250
IGMP 253
Multicast Configuration in the CUWN 256 Access Point-to-Client Delivery 256 Client-to-Access Point Delivery 256 Enabling Multicast on a Cisco WLAN Controller 259 MGIDs 262 Multicast Mobility Messaging 264 Enabling Multicast on a Cisco Router or Layer 3 Switch 265
VideoStream 267 Principles of VideoStream 268 Multicast Reliability 268
QoS 269
Configuring VideoStream on the WLC 272 Additional Design Recommendations 275
Wireless Multicast Roaming 275 Wireless CAPWAP Fragmentation 277 All WLCs Have the Same CAPWAP Multicast Group Address 278 WLC Placement 279
Summary 280
Index 281