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V 2.2 Copyright SystemExperts 2001,2002,2003
13
802.11b
n Physical Layer
n Physical Medium
Dependent (PMD) –
wireless encoding
n Physical Layer
Convergence Protocol
(PLCP) – common
interface
n long preamble for all
802.11b systems
n short preamble for
special case: e.g.,
streaming video, Voice-
over IP
n MAC Layer
n Inter Frame Space (IFS)
n Physical Carrier Sense
n Virtual Carrier Sense
n e.g., hidden-node
n Frame Control
n Power Management
n Fragmentation
V 2.2 Copyright SystemExperts 2001,2002,2003
14
802.11 A Little Less Plain & Simple
Logical Link Control
Point Coordination Function (pcf)
Distributed Coordination Function (pcf)
2.2 GHz
FHSS
2.4 GHz
DSSS
Infrared 2.4GHz
DSSS
5.5 and
11 Mbps
5GHz
OFDM
6,9,12,
18,24,36
,48,54
Mbps
MAC
PHY
Connection-less Service
Connection Service
Data Rates
1Mbps and 2 Mbps
IEEE 802.11
802.11b
802.11a
- Practical Wireless IP: 1
- Course Contents 2
- Course Objectives 2
- What is Wireless 3
- Wireless Component Overview 4
- Wireless Devices 4
- General Purpose Devices 5
- FH, DS, IR, CCK(b), OFDM(a) 6
- Physical Layer 7
- 802.11b Frame Control 8
- 802.11b IBSS 8
- 802.11b BSS 9
- 802.11b ESS 9
- Exposures 10
- Technology Problems 10
- Theft of hardware 11
- Registry Permissions 12
- Masquerading 13
- Eavesdropping 14
- MAC Layer 14
- MAC address configuration 15
- Where are We? 17
- Section Contents 17
- Key Factors in Technology 18
- Cellular Basics 18
- Major Cellular Systems 19
- GSM Security 20
- Today’s Data Systems 20
- CDPD Security 21
- Other Popular Systems 22
- What is 3G? 22
- In a box … 23
- Observations 23
- Mobile Data Services 24
- Uses a micro-browser 25
- Popular delivery standards 25
- Web Clipping 26
- WAP Protocol Layers 28
- The Gap in WAP 28
- Gap in WAP 29
- What Really Matters? 30
- Wireless LAN Technologies 32
- Upcoming WLAN 32
- 802.11 Local Area Wireless 33
- 802.11b Components 33
- Current 802.11 Security 34
- More on WEP Keys 35
- Access Points and WEP 35
- WEP Encryption Steps 36
- WEP Encryption 36
- WEP Decryption Steps 37
- WEP Decryption 37
- 128-bit Version (WEP2) 38
- WEP Key Management 38
- The Major WEP Problems 39
- Problem: Keystream Reuse 40
- -- as key length increases 41
- Current Status of WEP 42
- Current Status of WEP (cont) 43
- Current 802.11 Authorization 44
- Wireless EAP: Cisco’s Version 45
- Let’s take a look…J 47
- Access Points 101 49
- Frequency Overlap 50
- Access Point Usage 50
- Extension Point 51
- Access Point Placement 51
- Placement (cont.) 52
- Placement, 3 Dimensional 53
- Capacity and Bandwidth 53
- Bandwidth Aggregation 54
- Anatomy of 802.11b 55
- Anatomy of 802.11b: the bits 55
- Anatomy of 802.11b: the wave 56
- Congestion (cont.) 57
- Hidden Node Problem 58
- Finding those Hidden Nodes 59
- Surprising Results 60
- What Does This Mean? 60
- Anatomy of 802.11b: Roaming 61
- Roaming (cont.) 61
- Roaming Activities 62
- IEEE IAPP 63
- Wi-FI Roaming (cont.) 64
- Configuring an Access Point 65
- Access Point Medicine 65
- Wireless at Home 67
- Wireless at a Conference 68
- Industry Setup: Ariba 68
- CyberCafe 69
- Architectural Considerations 69
- Linux Wireless RF Sniffer 71
- Linux Sniffer: How-To 72
- How-To (cont.) 72
- Sniffer Observations 73
- AirSnort 73
- Home Spun Access Point 74
- Building your own AP 74
- My Problems 75
- My Observations 76
- How Does it Work? 77
- IEEE 802.11a 79
- 1W5.725-5.825 80
- 802.11a Coverage 81
- 802.11a Coverage Graphic 81
- 802.11a Problems 82
- 802.11 Thoughts 82
- Antennas: The Skinny 84
- Antennas: Basics 85
- Antennas: Basics (cont.) 85
- Antennas: Dipole 86
- Dipole Radiation 86
- Antennas: Directional 87
- Directional Radiation: Biquad 87
- Antennas: PCMCIA Cards 88
- Typical PCMCIA Radiation 88
- Antennas: More Facts 89
- Antennas: More Facts (cont.) 89
- Thanks to … 92
- References 93
- References (cont.) 93
- Wireless Stuff 95
- Mailing Lists 95
- Glossary 96
- Glossary (cont.) 96
- Glossary(cont.) 97
- End Matter 98
- Apple Airport 99
- Building your own AP (cont.) 100
- Directions (cont.) 101
- Floppy based Wireless Gateway 103
- WFG Internals 103
- WFG Internals (cont.) 104
- Consultant 106
- Brad C. Johnson 106
- Vice President 106
- Philip Cox 106
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