• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Chapter 1: A First Look at Windows 2000 Professional
 

Chapter 1: A First Look at Windows 2000 Professional

on

  • 1,075 views

 

Statistics

Views

Total Views
1,075
Views on SlideShare
1,074
Embed Views
1

Actions

Likes
0
Downloads
51
Comments
0

1 Embed 1

http://www.slideshare.net 1

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Chapter 1: A First Look at Windows 2000 Professional Chapter 1: A First Look at Windows 2000 Professional Presentation Transcript

    • Guide to Wireless Communications
    • Objectives
      • Explain how the major wireless technologies are used today - WiFi
      • Describe the applications used in wireless technology
      • List and explain the advantages of wireless technology
      • List and explain the disadvantages of wireless technology
    • Wireless – the hype?
      • Wireless communications is the next major event in the history of technology
      • Wireless communications will revolutionize how we live
      • Users will be able to access digital resources no matter where they find themselves
    • How Wireless Technology Is Used
      • Wireless refers to any device that does not use wires
      • Wireless communications refers to the transmission of user data without wires
    • Wireless Applications
      • Wireless applications are found anywhere employees need mobility, including in the following industries :
        • Education
        • Military
        • Business
        • Entertainment
        • Travel
        • Construction
        • Warehouse management
        • Health care
    • Wireless Communications in Industries
      • Education—classrooms, presentations, libraries, access anywhere on campus
      • Military—Universal Handset, a 1.5 lb. device allows full motion video, cellular and satellite communications, and Internet access
      • Business—office space where traditional infrastructure does not exist, such as conference room or hotel room
    • Wireless Communications in Industries
      • Entertainment—barcodes on tickets validated by handheld readers; fans accessing game statistics, watching replays, ordering concessions through notebook computers or PDAs
      • Travel—global positioning systems (GPS) providing emergency roadside assistance; airline passengers using wireless notebooks or PDAs
    • Wireless Communications in Industries
      • Construction—scheduling construction phases and employee travel, completing payroll, diagnosing equipment
      • Warehouse Management—inventory, shipping, reading bar-coded pallet labels
      • Health Care—tracking dispensed medicine, verifying patients’ bar-coded armbands, accessing patient records
    • Current Wireless Systems
      • Fixed Wireless Access (last mile)
      • Wide Area Wireless Data Services (WWANs)
      • Cellular Systems
      • Satellite Systems & Paging Systems
      • HomeRF (SWAP) (now dead?)
      • Bluetooth
      • Wireless LANs (WiFi)
      • WiFi5
    • SWAP
      • Shared Wireless Access Protocol (SWAP) defines wireless computer networks
        • Allows wireless data and voice communication from distances up to 150 feet at speeds up to 10 million bits per second (megabits or Mbps)
        • Established by HomeRF Working Group, comprised of over 50 different companies
        • Uses wireless home networking adapter that sends data over radio waves throughout the home, as seen in Figure 1-1
    • Home Wireless Network
    • HomeRF
      • Shared Wireless Access Protocol (SWAP), Home RF is an open industry specification that allows wireless devices to share information around home
        • Operates in license-free 2.4 GHz frequency and uses frequency-hopping spread spectrum (FHSS)
        • Provides quality-of-service (QoS) that prioritizes time-sensitive transmissions
        • Version 1.0, introduced in 2000, transmits at 1.6 Mbps, but version 2.0, released in 2001, transmits at 10 Mbps
    •  
    • Bluetooth
      • Uses devices with small radio transceivers, called radio modules, built onto microprocessor chips
      • Special software, called a link manager, identifies other Bluetooth devices, creates links with them, and sends and receives data
      • Transmits at up to 1 Mbps over a distance of 33 feet and is not impeded by physical barriers
      • Bluetooth products created by over 1500 computer, telephone, and peripheral vendors
    • Bluetooth Headset
      • The Bluetooth headset automatically establishes a connection with the telephone
    • Piconet
      • Two or more Bluetooth devices that send and receive data make up a personal area network (PAN), also called a piconet
      • Figure 1-3 shows a Bluetooth network
      Bluetooth was named after the 10 th century Danish King Harold Bluetooth, who was responsible for unifying Scandinavia
    • Bluetooth Network
    • Network Topology
      • Two types of Bluetooth network topologies
        • Piconet
        • Scatternet (collection of piconets)
      • Two Bluetooth devices within range automatically connect
        • One device is the master, controlling all wireless traffic
        • The other is the slave, taking commands from the master.
    • Piconets
      • A piconet is one master and at least one slave using the same channel
      • An active slave is sending transmissions
      • A passive slave is not actually participating
    • Bluetooth Issues
      • Many challenges face Bluetooth
        • Cost
        • Limited support
        • Shortcomings in protocol itself
        • Positioning in marketplace
        • Conflicts with other devices in radio spectrum
    • Cost
      • Chips have decreased in price to about $15 from a high of over $75
        • Not advantageous to replace a $7 cable with a $15 chip
        • Many think cost must come down to about $5 before Bluetooth reaches competitive advantage
    • Limited Support
      • Bluetooth is caught in “chicken or egg” scenario
        • Because of low market penetration, Bluetooth is not fully supported by hardware and software vendors
        • Users reluctant to purchase technology that is not fully supported
      • Microsoft is “straddling the fence”
        • Provides Bluetooth support for Pocket PC 2002
        • Does not support Bluetooth in Windows XP
    • Protocol Limitations
      • Major limitation is no hand-off between piconets
        • Unlike cell phone switching, Bluetooth connection is broken and must be restored with new master when device moves from one piconet area to another
      • Bluetooth provides less than optimal security by authenticating devices instead of users
      • Devices cannot determine how function of other devices can be used in cooperating setting
    • Market Position
      • Current position is between IEEE 802.11x WLANs and cell phones
        • WLAN is preferred technology for connecting wireless devices to form network
        • WLAN is mature, robust, flexible, popular technology
        • Trend today is fewer devices instead of more, and cell phones have integrated capabilities that Bluetooth lacks
    • Spectrum Conflict
      • The 2.4 GHz band that Bluetooth uses conflicts with IEEE 802.11b WLANs
        • WLAN may drop connection when detects another device sharing its frequency
        • Most obvious fix is moving Bluetooth device away from WLAN
        • Many vendors offer products that let Bluetooth and 802.11b WLANs share spectrum
        • New 802.11a WLAN standard uses a different frequency, eliminating the conflict
    • Wireless Local Area Network (WLAN)
      • Based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11b networking standard
      • WLAN computers transmit up to 11 Mbps at distances of 375 feet
      • IEEE 802.11a standard increases bandwidth to 54 Mbps
      • Figure 1-8 shows a WLAN warehouse network
      • 802.11 often called wireless ethernet
    • WLAN Warehouse Network
    • WLAN Applications
      • Almost nonexistent until 2000, WLANs have experienced astonishing growth, with sales expected to top $34 billion by 2004
      • WLANs have broad range of uses including colleges and schools, businesses, airports, warehouses, shopping malls, and stadiums
      • WLANs have taken the world by storm and the list of users grows daily
    • How WLANs Operate
      • Although a variety of radio frequency WLANs exist, different products share similarities and operate similarly
      • Only two components are required for a wireless network
        • Wireless network interface (NIC) cards
        • Access points (AP)
    • Wireless NIC and Access Point (AP)
      • Each computer on WLAN uses wireless network interface card (NIC) with built-in antenna
      • Wireless NIC sends signals through radio waves to a fixed access point (AP)
        • AP point may be attached to a wired LAN
        • Figure 1-9 shows an AP and wireless NIC
      • WLANs also used in office environments, as shown in Figure 1-10
    • Access Point and Wireless NIC
    • Office WLAN
    • Wireless Network Interface Card
      • NIC connects computer to network so it can send and receive data
      • On wired network, NIC has a port for a cable connector, as seen in Figure 6-1
      • On wireless network, the NIC has an antenna to send and receive RF signals
        • NIC changes internal data from parallel to serial, divides data into packets with sending and receiving addresses, determines when to send packet, and transmits packet
    • Integrated Wireless NICs
      • Some vendors plan integrating components of wireless NIC onto single chip on motherboard
      • Some notebook manufacturers will integrate wireless NIC into top of notebook behind LCD display
        • This will keep RF waves away from motherboard
    • Software for Wireless NICs
      • Software may be part of operating system itself
        • Windows XP has software integrated while previous versions of Windows do not
      • Software may be separate program loaded into the computer
        • All operating systems before Windows XP, including Linux, require loading software
        • Operating systems for PDAs may soon integrate software to recognize a wireless NIC
    • Access Point
      • An access point (AP) has three main parts
        • An antenna and a radio transmitter/receiver
        • An RJ-45 wired network interface to connect to a wired network
        • Special bridging software
    • Access Point
    • Functions of an Access Point
      • Access point has two basic functions
        • Acts as base station for wireless network
        • Acts as bridge between wireless and wired network
        • Bridges are LAN connectors at MAC level
      • See Figure 6-7
    • Access Point as a Bridge
    • Characteristics of an Access Point
      • Range approximately 375 feet (115 meters)
      • Generally supports over 100 users
        • One access point for each 50 users with light email and basic Internet access
        • One access point per 20 users for heavy network access and large file transfer
      • APs typically mounted on ceiling, but AC power may be a problem
        • Power over Ethernet feature delivers DC power through standard unshielded twisted pair (UTP) Ethernet cable
    • Ad Hoc Mode
      • Ad Hoc Mode or peer-to-peer mode lets wireless clients communicate among themselves without an access point
        • Officially called Independent Basic Services Set (IBSS), this mode is easy to set up, but it does not have access to a wired network
        • See Figure 6-8
    • Ad Hoc Mode
    • Infrastructure Mode
      • Infrastructure Mode, also called Basic Service Set (BSS), has wireless clients and an access point
      • More access points can be added to create an Extended Service Set (ESS)
        • See Figure 6-9
    • Extended Service Set (ESS)
    • Features of Access Points
      • Coverage area should overlap when using multiple access points
        • Wireless clients survey radio frequencies to find an AP that provides better service
        • A seamless handoff occurs when client associates with new AP
    • ESS and Subdivided Networks
      • Drawback of ESS WLANs is that all wireless clients and APs must be part of same network to allow roaming
      • Network managers like to subdivide networks into subnets, but this prevents clients from roaming freely
        • Alternative may be software that tricks network into seeing subnets as one network
    • Wireless Gateway
      • Devices that follow 802.11 standard are becoming less expensive and more popular
      • Wireless Gateway has made future of HomeRF very shaky
      • Wireless gateway has wireless access point, Network Address Translator (NAT) router, firewall, connections for DSL and cable modems, and other features
    • IEEE 802.11
      • Introduced in 1990
      • Defines cable-free local area network with either fixed or mobile locations that transmit at either 1 or 2 Mbps
      • Uses OSI model with functions of PHY and MAC layer performing WLAN features
        • See Figure 6-10
      • Slow bandwidth insufficient for most network applications
    • WLAN features in PHY and MAC layers
    • IEEE 802.11b
      • 1999 amendment to 802.11 standard
      • Added two higher speeds: 5.5 and 11 Mbps
      • Called Wi-Fi
      • Quickly became standard for WLANs
    • Wireless changes to layers
      • Physical
      • Data Link
    • Physical Layer
      • Physical layer that sends and receives signals from network is divided into two parts
        • See Figure 6-11
      • Physical Medium Dependent (PMD) sublayer defines how data is transmitted and received through the medium
      • Physical Layer Convergence Procedure (PLCP) performs two basic functions, as seen in Figure 6-12
        • Reformats data into frame PMD sublayer can transmit
        • Listens to determine when data can be sent
    • PHY Sublayers
    • PLCP Sublayer
    • Physical Layer Convergence Procedure Standards
      • Based on direct sequence spread spectrum (DSSS)
      • Reformats data from MAC layer into frame that PMD sublayer can transmit
        • See Figure 6-13
      • Frame has three parts
        • Preamble and Header transmit at 1 Mbps
        • Data portion, containing from 1 to 16,384 bits, may be sent at faster rate
    • PLCP Frame
    • Physical Medium Dependent Standards
      • Frame created by PLCP passes to PMD sublayer where binary 1’s and 0’s are translated into radio signals for transmission
      • 802.11b standard uses Industrial, Scientific, and Medical (ISM) band for transmissions
        • May use 14 frequencies, beginning at 2.412 GHz and incrementing in .005 GHz steps
        • See Table 6-1
    • 802.11b ISM Channels
    • Medium Access Control Layer Changes
      • 802.11 Data Link layer has two sublayers
        • Logical Link Control (LLC), used in 802.11b wireless networks with no change from wired network functions
        • Media Access control (MAC) contains all changes necessary for 802.11b WLANs
    • Two Kinds of Coordination
      • Coordination necessary among devices sharing same RF spectrum
      • Two kinds of coordination
        • Distributed coordination function is 802.11b standard
        • Point coordination function is optional
    • Distributed Coordination Function
      • Channel access methods refer to different ways of sharing
      • Contention
        • Computers compete for use of network
        • May cause collisions that result in scrambled messages, as seen in Figure 6-14
        • Must first listen to be sure no other device is transmitting
    • Collision
    • CSMA/CD
      • 802.3 Ethernet standard uses contention with “listening” as channel access method
        • Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
        • After a collision, each computer waits a random amount of time, called backoff interval, before attempting to resend
        • See Figure 6-15
    • CSMA/CD
    • Distributed Coordination Function (DCF)
      • 802.11b wireless networks cannot use CSMA/CD because radio signals drown out ability to detect collisions
      • 802.11b uses Distributed Coordination Function (DCF) with modified procedure known as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
        • Following collision, clients wait random amount of slot time after medium is clear
        • This technique helps reduce collisions
    • Packet Acknowledgement (ACK)
      • CSMA/CA also reduces collisions by using explicit packet acknowledgement (ACK)
        • Receiving client must send back to sending client an acknowledgement packet showing that packet arrived intact
        • If ACK frame is not received by sending client, data packet is transmitted again after random waiting time
        • Figure 6-16 illustrates CSMA/CA
    • CSMA/CA
    • Point Coordination Function
      • Polling, an orderly channel access method, prevents collisions by requiring device to get permission before transmitting
        • Each computer is asked in sequence if it wants to transmit, as shown in Figure 6-18
      • 802.11b uses an optional polling function known as Point Coordination Function (PCF)
        • Beacon frame indicates how long PCF will be used
        • If client has nothing to transmit, it returns a null data frame
    • Polling
    • Association and Reassociation
      • MAC layer uses association and reassociation to make sure client joins WLAN and stays connected
        • Uses either active or passive scanning process
          • Passive scanning has client listen for signal containing AP’s Service Set Identifier (SSID
          • Active scanning has client send out probe frame and wait for probe response frame from AP
        • After locating AP, client sends associate request frame and may join network after receiving frame with status code and client ID number
    • Reassociation
      • Reassociation involves dropping connection with one access point and establishing connection with another AP
        • Allows mobile clients to roam beyond coverage area of single AP
        • Allows client to find new AP if original one becomes weak or has interference
      • Client scans to find new AP and sends reassociation request frame
        • New AP then sends disassociation frame to old AP as shown in Figure 6-19
    • Reassociation Process
    • MAC Frame Formats
      • 802.11b specifies three different MAC frame formats
        • Management frames—set up initial communication between client and AP, as seen in Figure 6-21
        • Control frames—provide assistance in delivering frame that contains data, as seen in Figure 6-22
        • Data frames—carry information to be transmitted to destination client, as seen in Figure 6-23
    • Management Frame
    • Control Frame
    • Data Frame
    • High Speed WLANs
      • Three standards for high-speed WLANs that transmit at speeds over 15 Mbps
        • IEEE 802.11a
        • IEEE 802.11g
        • HiperLAN/2
      • All WLANs are concerned with security
        • How to prevent unauthorized access
    • IEEE 802.11a
      • Approved in 1999, 802.11a transmits at speeds of 5.5 Mbps and 11 Mbps
      • Great demand for 802.11a WLANS, also called Wi-Fi5, with maximum speed of 54 Mbps
        • Devices use gallium arsenide (GaAs) or silicon germanium (SiGe) rather than CMOS semiconductors
        • Increased speed achieved by higher frequency, more transmission channels, multiplexing techniques, and more efficient error-correction
    • Summary
      • Radio Frequency (RF) wireless local area networks (WLANs) have wide range of uses
      • Wireless NIC performs same functions as wired NIC, but it uses antenna to send and receive signals
      • Wireless NIC may be PCI (Peripheral Component Interface) expansion card for desktop PC, Type II PC Card for notebook computer, or Compact Flash (CF) Card for smaller device like PDA
    • Summary
      • Access point (AP) contains three major parts
        • Antenna
        • Radio transmitter/receiver
        • RJ-45 interface to connect by cable to standard wired network by using special bridging software
      • AP has two basic functions
        • Acts as base station for wireless network
        • Acts as bridge between wireless and wired networks
    • Summary
      • RF WLAN sends and receives data in two different modes
        • Ad hoc mode lets wireless clients communicate among themselves without an access point
        • Basic Service Set (BSS) infrastructure mode consists of wireless clients and at least one access point
      • Can add more access points to increase coverage area and create Extended Basic Service Set (ESS), consisting of two or more BSS wireless networks
    • Summary
      • HomeRF, also known as Shared Wireless Access Protocol (SWAP) defines how wireless devices such as computers and cordless phones can share and communicate around the home
        • Home RF version 1.0 products, introduced in 2000, transmit at 1.6 Mbps
        • Version 2.0, released in 2001, transmits at 10 Mbps
    • Summary
      • IEEE 802.11 standard defines wireless network, either mobile or fixed, that transmits up to 2 Mbps
        • Much too slow for most network applications
      • IEEE 802.11b standard quickly became standard for wireless networks when it added two higher speeds: 5.5 Mbps and 11 Mbps
      • Physical Layer Convergence Procedure Standard (PLCP) for 802.11b uses direct sequence spread spectrum (DSSS)
    • Summary
      • The PLCP reformats data from MAC layer into frame that PMD sublayer can transmit.
      • Frame has three parts: preamble, header, and data
      • 802.11b uses Industrial, Scientific, and Medical (ISM) band for transmission at 11, 5.5, 2, or 1 Mbps
    • Summary
      • 802.11b uses Distributed Coordination Function (DCF) access method that specifies a modified Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) procedure
        • CDMA/CA makes all clients wait random amount of time following collision
        • Reduces collisions by using explicit packet acknowledgements (ACK)
    • Summary
      • MAC layer of 802.11b standard uses association and reassociation to allow client to join WLAN and stay connected
        • Association uses either passive or active scanning to determines whether wireless client or access point should be accepted as part of network
        • Reassociation means client drops connection with one access point and reestablishes connection with another AP
    • Summary
      • 802.11b defines power management to conserve battery power without missing data transmissions
      • 802.11b specifies three different types of MAC frame formats
        • Management frames set up communications between client and access point
        • Control frames assist in delivering data frames
        • Data frames carry information being transmitted
    • Summary
      • 802.11 standard defines three different interframe spaces (PFS) or time gaps
        • Rather than being “dead space,” these standard spacing intervals or time gaps between transmission of data frames are used for special types of transmissions
    • The Wireless Landscape
      • Wireless communication is standard means of communication for people in many occupations and circumstances
      • Table 1-1 summarizes wireless technologies, transmission distance, and speed
      • Figure 1-14 shows a wireless landscape
      • Job market to support wireless technology is already exploding
    • Wireless Technologies
    • The Wireless Landscape
    • Wireless Advantages and Disadvantages
      • Advantages
        • Mobility
        • Easier and less expensive installation
        • Increased reliability
        • Disaster recovery
      • Disadvantages
        • Health risks ?
        • Radio signal Interference
        • Security
    • Wireless Advantages
      • Mobility—employees have contact with network; work in teams for better productivity
      • Easier and less expensive installation—no need to install cables or modify historical property; easy to remodel office without concern for network access
      • Increased reliability—no outages caused by cable failure
      • Disaster recovery—easy to relocate office quickly using WLANs and laptop computers
    • Wireless Disadvantages
      • Health risks?—devices emit small levels of RF
        • FDA—inconclusive about safety of wireless devices
        • FCC, FDA, and EPA set exposure guidelines for wireless phones in 1996; Specific Absorption Rate (SAR) of no more than 1.6 watts per kilogram
      • Radio signal interference--other devices interfere
      • Security—some wireless technologies add security such as encryption or coded numbers for authorization to gain access to the network
    • Wireless Performance Gap WIDE AREA CIRCUIT SWITCHING User Bit-Rate (kbps) 14.4 digital cellular 28.8 modem ISDN ATM 9.6 modem 2.4 modem 2.4 cellular 32 kbps PCS 9.6 cellular wired- wireless bit-rate "gap" 1970 2000 1990 1980 YEAR LOCAL AREA PACKET SWITCHING User Bit-Rate (kbps) Ethernet FDDI ATM 100 M Ethernet Polling Packet Radio 1st gen WLAN 2nd gen WLAN wired- wireless bit-rate "gap" 1970 2000 1990 1980 .01 .1 1 10 100 1000 10,000 100,000 YEAR .01 .1 1 10 100 1000 10,000 100,000
    • Summary
      • Wireless communications, including Internet connections and networks, are becoming standard in business world
      • SWAP connects different devices for home users
        • Quickly becoming obselete
      • Bluetooth connects some devices over short distances
      • WLANs – WiFi 802.11 family
    • Summary
      • WLANS are fixture of business networks
      • WLAN applications found in wide variety of industries and organizations
      • Primary advantage of WLAN is mobility or freedom to move without being connected by a cable
      • Other advantages include easier and less expensive installation, increased network reliability, and support for disaster recovery