CWNA Guide to Wireless LANs, Second Edition Chapter Ten Managing a Wireless LAN.
Chapter 11: Wireless LANs
description
Transcript of Chapter 11: Wireless LANs
![Page 1: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/1.jpg)
Chapter 11: Wireless LANs
Business Data Communications, 5e
![Page 2: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/2.jpg)
Business Data Communications, 5e
2
Wireless LAN Applications
• LAN extension
• Cross-building interconnect
• Nomadic access
• Ad hoc networks
![Page 3: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/3.jpg)
Business Data Communications, 5e
3
LAN extension
• Originally targeted to reduce cost of wiring, but new buildings now have sufficient wiring in place
• Still useful in buildings where wiring is problematic– buildings with large open areas, – historical buildings with insufficient twisted pair – small offices wired LANs are not economical
• Typically, a wireless LAN will be linked into a wired LAN on the same premises
![Page 4: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/4.jpg)
Business Data Communications, 5e
4
Single-Cell Wireless LAN
![Page 5: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/5.jpg)
Business Data Communications, 5e
5
Cross-building interconnect
• Connect LANs in nearby buildings, be they wired or wireless LANs
• Point-to-point wireless link is used between two buildings (e.g. two microwave or infrared transmitter/receiver units can be placed on the rooftops of two buildings within the line of sight of each other)
• Devices are typically bridges or routers.
![Page 6: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/6.jpg)
Business Data Communications, 5e
6
Nomadic Access
• Provides a wireless link between a LAN hub and a mobile data terminal (e.g. laptop computer)
• Examples– Enable an employee returning from a trip to transfer
data from a personal portable computer to a server in the office.
– Access in an extended environment such as a campus or a business operating out of a cluster of buildings.
– In both of these cases, users may wish access to the servers on a wired LAN from various locations
![Page 7: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/7.jpg)
Business Data Communications, 5e
7
Ad hoc networks
• A peer-to-peer network (no centralized server) set up temporarily to meet some immediate need
• For example, a group of employees, each with a laptop or palmtop computer, may convene in a conference room for a business or classroom meeting. The employees link their computers in a temporary network just for the duration of the meeting
![Page 8: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/8.jpg)
Business Data Communications, 5e
8
Wireless LAN Requirements
• Efficient throughput• Support for multiple nodes• Connection to backbone LAN• Broad service area (~ 100-300m)• Allows for reduced power consumption while not using the
network (e.g. sleep mode)• Transmission robustness and security• Co-located network operation• License-free operation• Handoff/roaming• Dynamic and automated addition, deletion, and relocation
![Page 9: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/9.jpg)
Business Data Communications, 5e
9
Wireless LAN Technology
• Infrared (IR) LANs– Individual cells are limited to a single room, because
infrared light does not penetrate opaque walls
• Spread spectrum LANs– In most cases, these LANs operate in the ISM
(Industrial, Scientific, and Medical) bands so that no FCC licensing is required for their use in the U.S.
• Narrowband microwave– Do not use spread spectrum. Some of these products
operate at frequencies that require FCC licensing, while others use one of the unlicensed ISM bands
![Page 10: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/10.jpg)
Business Data Communications, 5e
10
IEEE 802.11 Architecture
![Page 11: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/11.jpg)
Business Data Communications, 5e
11
IEEE 802.11 Services
• Association
• Reassociation
• Disassociation
• Authentication
• Privacy
![Page 12: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/12.jpg)
Business Data Communications, 5e
12
IEEE 802.11Medium Access Control
• Reliable Data Delivery– Basic data transfer mechanism involves an
exchange of two or four frames (data, ACK, and optional CTS/RTS)
• Access Control– DFWMAC (distributed foundation wireless
MAC)
![Page 13: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/13.jpg)
Business Data Communications, 5e
13
IEEE 802.11Protocol Architecture
![Page 14: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/14.jpg)
Business Data Communications, 5e
14
IEEE 802.11 Physical Layer
• 802.11 (1997)– MAC layer and three physical layer specifications;
two 2.4-GHz band, one infrared, all operating at 1 and 2 Mbps
• IEEE 802.11a (1999)– operates in the 5-GHz band at up to 54 Mbps
• IEEE 802.11b (1999)– operates in the 2.4-GHz band at 5.5 and 11 Mbps.
• IEEE 802.g (2002)– extends IEEE 802.11b to higher data rates
![Page 15: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/15.jpg)
Business Data Communications, 5e
15
Original 802.11Physical Media Definitions
• Direct-sequence spread spectrum (DSSS) operating in the 2.4 GHz ISM band, at data rates of 1 Mbps and 2 Mbps
• Frequency-hopping spread spectrum (FHSS) operating in the 2.4 GHz ISM band, at data rates of 1 Mbps and 2 Mbps
• Infrared at 1 Mbps and 2 Mbps operating at a wavelength between 850 and 950 nm
• All of the original 802.11 products were of limited utility because of the low data rates
![Page 16: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/16.jpg)
Business Data Communications, 5e
16
IEEE 802.11b
• Extension of the IEEE 802.11 DSSS scheme, providing data rates of 5.5 and 11 Mbps (higher data rate is achieved with more complex modulation)
• Apple Computer was first, with AirPort wireless networking, followed by other vendors
• Wireless Ethernet Compatibility Alliance created to certify interoperability for 802.11b products
![Page 17: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/17.jpg)
Business Data Communications, 5e
17
Problems with 802.11 and 802.11b
• Original 802.11 and 802.11b may interfere with other systems that operate in the 2.4-GHz band– Bluetooth– HomeRF– other devices--including baby monitors and
garage door openers
• Limited data rate results in limited appeal
![Page 18: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/18.jpg)
Business Data Communications, 5e
18
Higher-Speed 802.11 Options
• 802.11a– Uses 5-GHz band. – Uses orthogonal frequency division multiplexing
(OFDM) rather than spread spectrum – Possible data rates are 6, 9, 12, 18, 24, 36, 48, and 54
Mbps
• 802.11g– Higher-speed extension to IEEE 802.11b. – Combines physical layer encoding techniques used in
802.11a and 802.11b to provide service at a variety of data rates
![Page 19: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/19.jpg)
Business Data Communications, 5e
19
Bluetooth
• Always-on, short-range radio hookup that resides on a microchip
• Low-power short-range wireless standard for a wide range of devices
• Uses 2.4-GHz band (available globally for unlicensed low-power uses)
• Two Bluetooth devices within 10 m of each other can share up to 720 kbps of capacity
![Page 20: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/20.jpg)
Business Data Communications, 5e
20
Examples of Bluetooth Capability
• Make calls from a wireless headset connected remotely to a cell phone
• Eliminate cables linking computers to printers, keyboards, and the mouse
• Hook up MP3 players wirelessly to other machines to download music
• Set up home networks to remotely monitor air conditioning, appliances, and Internet surfing
• Call home from a remote location to turn appliances on and off, set the alarm, and monitor activity.
![Page 21: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/21.jpg)
Business Data Communications, 5e
21
Bluetooth Applications
• Up to eight devices can communicate in a small network called a piconet; ten of these can coexist in the same coverage range of the Bluetooth radio
• Three general application areas– Data and voice access points– Cable replacement– Ad hoc networking
![Page 22: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/22.jpg)
Business Data Communications, 5e
22
Bluetooth Standards
• Core Specifications– Describes layers of the protocol architecture, from radio
interface to link control
• Profile Specifications– Discusses the use of the technology defined in the core
specifications to implement a particular usage model– General access profile specifies how the baseband
architecture should be used between devices that implement one or multiple profiles
– Other profiles fall into one of two categories: cable replacement or wireless audio
![Page 23: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/23.jpg)
Business Data Communications, 5e
23
Bluetooth Protocol Architecture
• Core Protocols• Cable Replacement Protocol (RFCOMM)
– presents a virtual serial port that is designed to make replacement of cable technologies as transparent as possible
• Telephony Control Protocol (TCS BIN)– a bit-oriented protocol that defines the call control
signaling for the establishment of speech and data calls between Bluetooth devices
• Adopted Protocols
![Page 24: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/24.jpg)
Business Data Communications, 5e
24
Bluetooth Core Protocols
• Radio
• Baseband
• Link manager protocol (LMP)
• Logical link control and adaptation protocol (L2CAP)
• Service discovery protocol (SDP)
![Page 25: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/25.jpg)
Business Data Communications, 5e
25
Bluetooth Adopted Protocols
• PPP
• TCP/UDP/IP
• OBEX
• WAE/WAP
![Page 26: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/26.jpg)
Business Data Communications, 5e
26
Bluetooth High-Priority Usage Models
• File Transfer
• Internet Bridge
• LAN Access
• Synchronization
• Three-in-one Phone
• Headset
![Page 27: Chapter 11: Wireless LANs](https://reader033.fdocuments.in/reader033/viewer/2022061508/56813ae1550346895da33457/html5/thumbnails/27.jpg)
Business Data Communications, 5e
27
Piconets and Scatternets