IFIP-UNU ADVANCED COURSE ON NETWORKING AND SECURITY Module II-Wireless Communications Section 2 The IEEE 802.11 Protocol

Learning Objectives Identify the IEEE 802. standards. Understand the MAC and PHY layers of 802.11 Identify which client operating systems are supported. Determine the status of a client card by observing the indicator lights. Install and configure a Cisco Aironet PC Card.

Overview This chapter will cover the IEEE 802.11 WLAN (WLAN) standards in detail, including data link and physical layer specifications. Throughout this module and this course, the terms IEEE and 802 are used often. This module provides a short overview of IEEE and the 802 committee. The MAC and physical layer services that have been standardized will be discussed. Finally, client adapters, driver types, and client support will also be discussed.

Key terms IEEE MAC PHY NIC STA MSDU PLCP PMD BSS

802.11 Standards

IEEE 802.11 Standards Activities 802.11a: 5GHz, 54Mbps 802.11b: 2.4GHz, 11Mbps 802.11d: Multiple regulatory domains 802.11e: Quality of Service (QoS) 802.11f: Inter-Access Point Protocol (IAPP) 802.11g: 2.4GHz, 54Mbps 802.11h: Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) 802.11i: Security 802.11j: Japan 5GHz Channels (4.9-5.1 GHz) 802.11k: Measurement 802.11m: Maintenance 802.11n: High-Speed

802.11a / 5 GHz Band Data rates supported: 54, 48, 36, 24, 12, and 6 Mbps Client will automatically “downshift” to lower data rate when it gets further from AP 23 Countries have approved the use of 802.11a products: U.S. Australia Austria Denmark France Sweden New Zealand Ireland Japan Singapore Taiwan Argentina U.K. Germany Norway Portugal Canada Belgium Netherlands Finland Poland Switzerland Mexico 802.11h will ultimately permit worldwide usage of WLANs @ 5 GHz Transmit Power Control (TPC) Dynamic Frequency Selection (DFS) 5.470-5.725 GHz band being opened up (11 more channels) This new 5.47-5.725 GHz band, plus 5.25-5.35 GHz UNII-2 band, will require DFS Current UNII-2 products in the market will likely be grandfathered (i.e. no DFS) 5 GHz band has more channels than 2.4 GHz band UNII-1 + UNII-2 = 8 channels (plus 11 future channels) vs. 3 channels for 2.4 GHz However, depending on distance between AP’s, you may only be able to use half of the 5 GHz channels due to adjacent channel interference 5 GHz band subject to less interference than 2.4 GHz band However, 2.4 GHz interference not a major problem in most business environments

Three Wireless Technologies 802.11b 802.11a 802.11g Frequency Band 2.4 GHz 5 GHz 2.4 GHz Availability Worldwide US/AP Worldwide Maximum Data rate 11 Mbps 54 Mbps 54 Mbps Cordless Phones Microwave Ovens Wireless Video Bluetooth Devices Cordless Phones Microwave Ovens Wireless Video Bluetooth Devices Other Services (Interference) HyperLAN Devices The Laws of Radio Dynamics: Higher Data Rates = Shorter Transmission Range Higher Power Output = Increased Range, but Lower Battery Life Higher Frequency Radios = Higher Data Rates Shorter Ranges

IEEE 802.11 Standard IEEE 802.11 became a standard in July 1997 2.4 GHz at 2 Mbps Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS) IEEE 802.11a and 802.11b became standards in September 1999 802.11a – 5 GHz at 54 Mbps OFDM 802.11b – 2.4 GHz at 11 Mbps DSSS IEEE 802.11g is scheduled to be ratified in 2003 802.11g – 2.4 GHz at 54 Mbps OFDM 802.11 promises “true” vendor interoperability

Standards and Organizations

WLAN Speeds & Frequencies 802.11g 2.4 GHz – OFDM/CCK 54 Mbps 802.11a 5 GHz – OFDM 54 Mbps 802.11b 2.4 GHz – CCK 11 Mbps Proprietary IEEE 802.11a/b Ratified Jan’99 Jan’00 Jan’01 Jan’02 Jan’03 Jan’04

What Is WLAN RF Technology? This section discusses theories and processes of using Spred Spectrum technology to send data over an RF signal. What Is WLAN RF Technology? Data sent over the air waves Two-way radio communications (half duplex) Same radio frequency for sending & receiving (transceiver) No licensing required for Cisco Aironet Wireless products (in most countries) Spread Spectrum is a type of emission designed to be somewhat immune to interference, difficult to detect, and hard to intercept. Actress Hedy Lamarr and music composer George Antheil patented the concept of Spread Spectrum in 1942. The idea was a method for guiding a torpedo without interference from a jamming signal. In 1986, the FCC agreed to allow the use of Spread Spectrum in the commercial market under the ISM bands. Just as the radio in your car has AM (Amplitude Modulation) and FM (Frequency Modulation) bands, other radios use different bands and types of modulation.

IEEE 802. Standards

802.11 Architecture

802.11 Physical (PHY) Layer Modulations

Stations (STA)

PHY Protocols

Basic Service Set (BSS)

Independent Basic Service Set (IBSS)

Extended Service Set (ESS) and Distributed System (DS)

MAC Layer

MAC Services

MAC Architecture

CSMA

Interframe Spaces

PHY Layer

PHY Functions

802.11b

Europe, Middle East and Asia 2.4 GHz Channel Sets Regulatory Domain Channel Identifier Center Frequency Americas Europe, Middle East and Asia Japan Israel X X 1 2 3 4 5 6 7 8 9 10 11 12 13 14 2412 MHz 2417 MHz 2422 MHz 2427 MHz 2432 MHz 2437 MHz 2442 MHz 2447 MHz 2452 MHz 2457 MHz 2462 MHz 2467 MHz 2472 MHz 2484 MHz X X

Channels- 2.4 GHz DSSS 11 Channels – each channel 22 MHz wide 1 set of 3 non-overlapping channels 14 Channels – each channel 22 MHz wide 4 sets of 3 non-overlapping channels, only one set used at a time 11 “chips per bit” means each bit sent redundantly 11 Mbps data rate 3 access points can occupy same area

802.11b Access Point Coverage 1 Mbps DSSS 2 Mbps DSSS 5.5 Mbps DSSS 11 Mbps DSSS

802.11b Scalability Total Theoretical Bandwidth = 33 Mbps Blue = 11 Mbps Green = 11 Mbps Red = 11 Mbps

Comparing the Technologies 802.11a Data Rates Data Rate Per Subchannel (Kbps) Modulation with Sub Channels Total Data Rate (Mbps) BPSK 125 6 BPSK 187.5 9 QPSK 250 12 QPSK 375 18 16QAM 500 24 16QAM 750 36 64QAM 1000 48 64QAM 1125 54

802.11a Channel Sets Americas include: Argentina Australia Austria Americas (-A) Japan (-J) Singapore (-S) Taiwan (-T) 34 5170 x 36 5180 38 5190 40 5200 42 5210 44 5220 46 5230 48 5240 52 5260 56 5280 60 5300 64 5320 20 Channel Set Cisco Maximum Peak Power (mW)* Channel ID Frequency (MHz) Americas include: Argentina Australia Austria Brazil Canada Chile Columbia Denmark France Mexico New Zealand Panama Peru Sweden United Kingdom United States Venezuela Assuming a 6 dBi antenna (The radiated power is): UNII-1 – 50 mW in the US/Japan, 200mW in Europe, 4 Channels (5.15-5.25), Indoor Access- Fixed Antenna UNII-2 – 250 mW in US, 4 Channels (5.25-5.35)- Indoor/Outdoor Use – Flexible Antenna UNII-3 – 1 W in the US, 4 Channels (5.725-5.825) – Outdoor Bridging only HiperLAN – 200 mW in Europe, 8 Channels (5.25-5.35) – Indoor Use only HiperLAN– 1W in Europe, 11 channels (5.470-5.725) – Indoor/Outdoor Use –Flexible Antenna

802.11a Access Point Coverage OFDM 54 Mbps 48 Mbps 36 Mbps 24 Mbps 18 Mbps 12 Mbps 09 Mbps 06 Mbps

802.11a Scalability (Indoor UNII-1 and 2) Total Theoretical Bandwidth = 432 Mbps 8 non-overlapping channels 54 Mbps 54 Mbps 54 Mbps 54 Mbps 54 Mbps 54 Mbps 54 Mbps 54 Mbps

Client Adapters

Cisco Aironet 802.11b Client Adapters 2.4 GHz 802.11b 11 Mbps Include PC Card PCI Card LMC Card Mini PCI

802.11b PC Card 2.4 GHz/802.11b Rate Shifting Fixed data rates 11 Mbps Rate Shifting 1, 2, 5.5, and 11Mbps Fixed data rates User configurable option Integrated Antenna PCMCIA interface Transmit power settings: 100 mW, 50 mW, 30 mW, 20 mW, 10 mW, 5 mW, and 1 mW

802.11b LMC Card 2.4 GHz/802.11b Rate Shifting Fixed data rates 11 Mbps Rate Shifting 1, 2, 5.5, and 11Mbps Fixed data rates User configurable option PCMCIA interface Transmit power settings: 100 mW, 50 mW, 30 mW, 20 mW, 10 mW, 5 mW, and 1 mW

802.11b PCI Card 2.4 GHz/802.11b Rate Shifting Fixed data rates 11 Mbps Rate Shifting 1, 2, 5.5, and 11Mbps Fixed data rates User configurable option RP-TNC Connector PCMCIA interface Transmit power settings: 100 mW, 50 mW, 30 mW, 20 mW, 10 mW, 5 mW, and 1 mW

802.11b Mini PCI Adapter 2.4 GHz/802.11b embedded wireless for notebooks 100 mW transmit power Must order through PC manufactures (not orderable directly through Cisco)

802.11a CardBus2 Client Adapter 5 GHz/802.11a 54 Mbps Rate Shifting 6, 9, 12, 18, 24, 36, 48, or 54 Fixed data rates User configurable option 5 dBi Patch Antenna CardBus interface Transmit power settings: 20 mW, 10 mW, and 5 mW

PC Card LEDs Dual LED helps identify the card status Green LED is the Status LED Orange LED is the RF traffic LED

LED Status

Windows Drivers

Linux and Macintosh Drivers

Downloading Drivers and Software

Ad-Hoc

Infrastructure

Aironet Client Utility (ACU)

Aironet Client Utility: Main Screen

Aironet Client Utility: Loading Firmware

Aironet Client Utility: Profile Manager

Aironet Client Utility: Adding a Profile

Profile: System Parameters

Profile: RF Network

Profile: RF Network

Profile: Advanced (Infrastructure)

Profile: Advanced (Ad Hoc)

Profile: Network Security

Aironet Client Utility: Status

Aironet Client Utility: Statistics

Aironet Client Utility: Link Test

Aironet Client Utility: Site Survey The Site Survey utility allows a user to perform a site survey to determine the best placement of the access points in order to provide the desired coverage. The Site Survey can run in either Passive or Active mode. The Active mode is used to perform site surveys. The Site Survey utility can be set to display results as percentages, or as actual values (for example, as dBm, or decibels per milliwatt). Complete the following steps to switch from percentage to dBm. 1. Click on the Preferences icon on the main page. 2. Select the dBm radio button under Signal Strength Display Units . Now your ACU Site Survey will show signal to noise ratio.

Link Status Meter

Labs

Labs of Section 2 Lab 2.4.3 Install a WLAN Adapter Card Lab 2.5.2 Install Aironet Client Utility (ACU) Lab 2.5.5 Configure Auto Profiles Lab 2.6.5.1 ACU Utilities Lab 2.6.5.2 Creating an Adhoc Network