Jaimin chp-1 - introduction - 2011 batch


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GTU-MCA-SEM IV - Fundamentals of Networking

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Jaimin chp-1 - introduction - 2011 batch

  1. 1. Computer Networks, Fourth Edition by Andrew S. Tanenbaum
  2. 2. Chapter 1
  3. 3. <ul><li>Physical layer (e.g., copper, fiber, wireless, satellites, and Internet over cable) </li></ul><ul><li>Data link layer (e.g., protocol principles, protocol verification, HDLC, and PPP) </li></ul><ul><li>MAC Sublayer (e.g., gigabit Ethernet, 802.11, broadband wireless, and switching) </li></ul><ul><li>Network layer (e.g., routing algorithms, congestion control, QoS, IPv4, and IPv6) </li></ul><ul><li>Transport layer (e.g., socket programming, UDP, TCP, RTP, and network performance) </li></ul><ul><li>Application layer (e.g., e-mail, the Web, PHP, wireless Web, MP3, and streaming audio) </li></ul><ul><li>Network security (e.g., AES, RSA, quantum cryptography, IPsec, and Web security) </li></ul>
  4. 4. <ul><li>Section 1.1.  Uses of Computer Networks       </li></ul><ul><li>Section 1.2.  Network Hardware       </li></ul><ul><li>Section 1.3.  Network Software       </li></ul><ul><li>Section 1.4.  Reference Models       </li></ul><ul><li>Section 1.5.  Example Networks       </li></ul><ul><li>Section 1.6.  Network Standardization       </li></ul><ul><li>Section 1.7.  Metric Units       </li></ul>
  5. 5. <ul><li>Business Applications </li></ul><ul><ul><li>online buying </li></ul></ul><ul><li>Home Applications </li></ul><ul><ul><li>mail, chat </li></ul></ul><ul><li>Mobile Users </li></ul><ul><ul><li>wireless: laptops, PDA, mobile, in plane </li></ul></ul><ul><li>Social Issues </li></ul>
  6. 6. <ul><li>A network with two clients and one server. </li></ul><ul><ul><li>Check bank account </li></ul></ul><ul><ul><li>Pay bills </li></ul></ul><ul><ul><li>Reserve ticket </li></ul></ul><ul><ul><li>Big companies have offices </li></ul></ul><ul><ul><li>@ various sites leads CS model </li></ul></ul><ul><li>The client-server model involves requests and replies. </li></ul>
  7. 7. <ul><li>Resource (inf0,data,device) sharing </li></ul><ul><li>Communication – email </li></ul><ul><li>Videoconferencing </li></ul><ul><li>e-Commerece </li></ul>
  8. 8. <ul><li>Access to remote information </li></ul><ul><ul><li>Leaning online, downloading(P2P – torrent) ,digital libraries, Newspapers and blogs </li></ul></ul><ul><li>Person-to-person communication </li></ul><ul><ul><li>chat (Yahoo-AIM-MSN), phone (VoIP- Video Chat) </li></ul></ul><ul><li>Interactive entertainment </li></ul><ul><ul><li>games, movies, … </li></ul></ul><ul><li>Electronic commerce </li></ul>
  9. 9. <ul><li>Peer-to-peer (P2P) </li></ul><ul><ul><li>Kazaa, Emule, </li></ul></ul><ul><li>E-commerce </li></ul>
  10. 10. <ul><li>Combinations of wireless networks and mobile computing. </li></ul><ul><ul><li>Wireless parking meters </li></ul></ul><ul><ul><li>Rental cars on busy airports </li></ul></ul><ul><ul><li>Food, drink, and other vending machines </li></ul></ul><ul><ul><li>PDA – replacement of plastic currency </li></ul></ul><ul><li>fixed wireless ≠ mobile wireless </li></ul>
  11. 11. <ul><li>Discussions about </li></ul><ul><ul><li>politics, </li></ul></ul><ul><ul><li>religion, </li></ul></ul><ul><ul><li>… </li></ul></ul><ul><li>Hack and robbery </li></ul><ul><li>Political issues: Google in China </li></ul><ul><li>Changing habits of “Netizens” </li></ul>
  12. 12. <ul><li>Transmission hardware </li></ul><ul><li>Special-purpose hardware devices </li></ul><ul><ul><li>interconnect transmission media </li></ul></ul><ul><ul><li>control transmission </li></ul></ul><ul><ul><li>run protocol software </li></ul></ul><ul><li>Protocol software </li></ul><ul><ul><li>encodes and formats data </li></ul></ul><ul><ul><li>detects and corrects problems </li></ul></ul>
  13. 13. <ul><li>Transmission technology (2 types) </li></ul><ul><ul><li>Broadcast links - Unicast - Multicast </li></ul></ul><ul><ul><li>Point-to-point links </li></ul></ul><ul><ul><ul><li>point-to-point networks consist of many connections between individual pairs of machines </li></ul></ul></ul><ul><ul><ul><ul><li>Ex: DSL,ISDN,T1 </li></ul></ul></ul></ul><ul><li>Scale </li></ul><ul><ul><li>Local Area Networks (LAN) </li></ul></ul><ul><ul><li>Metropolitan Area Networks (MAN) </li></ul></ul><ul><ul><li>Wide Area Networks (WAN) </li></ul></ul><ul><ul><li>Wireless Networks </li></ul></ul><ul><ul><li>Home Networks </li></ul></ul><ul><ul><li>Internetworks </li></ul></ul><ul><li>Media </li></ul><ul><ul><li>Wired </li></ul></ul><ul><ul><li>Wireless </li></ul></ul>
  14. 14. <ul><li>Types of transmission technology </li></ul><ul><li>Broadcast links </li></ul><ul><li>Point-to-point links </li></ul>
  15. 15. <ul><li>There are A single communication link for all systems in network = Broadcasting </li></ul><ul><ul><li>TV programs: IRI B (Islamic Republic of Iran Broadcast ), … </li></ul></ul><ul><li>Messages ( Packets ) contain destination address </li></ul><ul><li>Multicasting : A subset of systems can get the message </li></ul><ul><li>Usually used in small networks like LANs </li></ul>
  16. 16. <ul><li>Individual connections between pairs of machines. </li></ul><ul><li>There are many paths from one machine to another </li></ul><ul><ul><li>Need efficient routing algorithms </li></ul></ul><ul><li>Usually used in large scale networks like WAN </li></ul>
  17. 17. <ul><li>Packets </li></ul><ul><ul><li>Messages - the &quot;chunk&quot; of data transmitted from one machine to the next. </li></ul></ul><ul><li>Addressing </li></ul><ul><ul><li>One to one: Packet contains specific target address. </li></ul></ul><ul><ul><li>Broadcasting: All machines on the network receive and process the packet. </li></ul></ul><ul><ul><li>Multicasting: A subset of machines receive and process the packet </li></ul></ul>
  18. 18. <ul><li>Classification of interconnected processors by scale. </li></ul>
  19. 19. <ul><li>Privately owned. Can be up to several kilometers long; Ex. in a building </li></ul><ul><li>Separated by their: </li></ul><ul><ul><li> Size: Restricted so worst case transmission time can be contained. </li></ul></ul><ul><ul><li> Transmission technology: Single channel with multiple machines connected to it. Run at speeds of 10, 100, or more Mbps. </li></ul></ul><ul><ul><li> Topology: two popular broadcast networks: </li></ul></ul><ul><ul><ul><li>Bus </li></ul></ul></ul><ul><ul><ul><li>Ring </li></ul></ul></ul>
  20. 32. <ul><li>Topology … </li></ul><ul><ul><li>Bus </li></ul></ul><ul><ul><ul><li>Ethernet ( IEEE 802.3): </li></ul></ul></ul><ul><ul><ul><ul><li>Bus based broadcast network with decentralized control at 10 or 100 Mbps. </li></ul></ul></ul></ul><ul><ul><li>Ring </li></ul></ul><ul><ul><ul><li>Token Ring (IEEE 802.5): </li></ul></ul></ul><ul><ul><ul><ul><li>Ring based broadcast network with token arbitration at 4 or 16 Mbps. </li></ul></ul></ul></ul><ul><ul><li> Low delay. High reliability. </li></ul></ul><ul><ul><li> Requires collision arbitration </li></ul></ul>
  21. 33. <ul><li>Larger version of LAN (&quot;city&quot; wide). </li></ul><ul><ul><li>Public or private / data or voice. </li></ul></ul><ul><ul><li>Broadcast - no switches. </li></ul></ul><ul><ul><li>Can be distinguished from LANs based on wiring mechanism. </li></ul></ul><ul><ul><ul><li>DQDB (Distributed Queue Dual Bus), IEEE 802.6 </li></ul></ul></ul><ul><li>Ex. A metropolitan area network based on cable TV </li></ul>
  22. 34. <ul><li>Networks spanning large distances. </li></ul><ul><li>Ex. Relation between hosts on LANs and the subnet. </li></ul><ul><li>Hosts or End Systems: </li></ul><ul><ul><li>Machines running user applications. </li></ul></ul>
  23. 35. <ul><li>(Communication) Subnet : </li></ul><ul><ul><li>Connections between hosts - transmission lines + switches. </li></ul></ul><ul><ul><li>A &quot;locality&quot; understanding each other's addresses. </li></ul></ul><ul><li>Circuits (Channels, Trunks): </li></ul><ul><ul><li>Transmission lines move the bits. </li></ul></ul><ul><li>Packet switching nodes ( Router , Intermediate systems): </li></ul><ul><ul><li>Specialized computers moving data between several inputs </li></ul></ul><ul><ul><li>to several outputs. </li></ul></ul><ul><li>Point-to-point/Store-and-forward/Packet-switched - </li></ul><ul><ul><li>Moving through a series of routers, packets are received at a router, stored there, then forwarded to the next router. </li></ul></ul>
  24. 36. <ul><li>Ex. A stream of packets from sender to receiver. </li></ul>
  25. 37. <ul><li>Categories of wireless networks: </li></ul><ul><li>System interconnection </li></ul><ul><li>Wireless LANs </li></ul><ul><li>Wireless WANs </li></ul>
  26. 38. <ul><li>Used where computer is mobile or far away from wires. </li></ul><ul><ul><li>Only 1 - 2 Mbps, </li></ul></ul><ul><ul><li>higher error rates, </li></ul></ul><ul><ul><li>interference </li></ul></ul><ul><li>Use </li></ul><ul><ul><li>Sound </li></ul></ul><ul><ul><li>Light and mirrors </li></ul></ul><ul><ul><li>Infrared </li></ul></ul><ul><ul><li>RF </li></ul></ul><ul><ul><li>Microwave </li></ul></ul>
  27. 39. <ul><li>(a) Bluetooth configuration </li></ul><ul><li>(b) Wireless LAN </li></ul>
  28. 40. <ul><li>(a) Individual mobile computers </li></ul><ul><li>(b) A flying LAN </li></ul>
  29. 41. <ul><li>Protocol Hierarchies </li></ul><ul><li>Design Issues for the Layers </li></ul><ul><li>Connection-Oriented and Connectionless Services </li></ul><ul><li>Service Primitives </li></ul><ul><li>The Relationship of Services to Protocols </li></ul>
  30. 42. <ul><li>Primary networks more depend on hardware </li></ul><ul><li>It talks about the philosophy of connecting together two entities. </li></ul><ul><li>“ Layering” is the key word </li></ul><ul><ul><li>Protocol Hierarchies </li></ul></ul><ul><ul><li>Design Issues for the Layers </li></ul></ul><ul><ul><li>The Relationship of Services to Protocols </li></ul></ul>
  31. 43. <ul><li>Layers : </li></ul><ul><ul><li>The concept that network software is organized functionally into levels. A level on one host talks to the same level on another host (its peer). </li></ul></ul><ul><li>Protocol : </li></ul><ul><ul><li>The protocol is the convention or standard that a layer uses to talk to the other layer. An agreement or standard on the conversation . </li></ul></ul>
  32. 44. <ul><ul><li>Layers, </li></ul></ul><ul><ul><ul><li>Important that each </li></ul></ul></ul><ul><ul><ul><li>layer perform specific </li></ul></ul></ul><ul><ul><ul><li>actions. </li></ul></ul></ul><ul><ul><li>protocols, </li></ul></ul><ul><ul><li>Interfaces </li></ul></ul><ul><ul><ul><li>Defines the services </li></ul></ul></ul><ul><ul><ul><li>That one layer offers </li></ul></ul></ul><ul><ul><ul><li>another (either up </li></ul></ul></ul><ul><ul><ul><li>or down.) </li></ul></ul></ul>
  33. 45. <ul><li>Ex. Protocol of philosopher-translator-secretary architecture. </li></ul>
  34. 46. <ul><li>Ex. Protocol Hierarchies </li></ul><ul><ul><li>information flow supporting virtual communication in layer 5 </li></ul></ul>
  35. 47. <ul><li>Physical Medium: </li></ul><ul><ul><li>Underneath the layers is the wire or fiber or whatever. </li></ul></ul><ul><li>Network architecture: </li></ul><ul><ul><li>A set of layers and protocols. It contains details on what happens in the layer and what the layers says to its peer. </li></ul></ul><ul><ul><li>Functional interfaces and implementation details are not part of the spec, since that's not visible outside the machine. </li></ul></ul><ul><li>Protocol stack: </li></ul><ul><ul><li>A list of protocols used by a system, one protocol per layer . </li></ul></ul><ul><li>Information flow: </li></ul><ul><ul><li>&quot;Send_to_peer&quot; rather than &quot;call_next_layer_down&quot;. </li></ul></ul>
  36. 48. <ul><li>Addressing </li></ul><ul><li>Error control. (garbled or missing.) </li></ul><ul><li>Preservation of message ordering. </li></ul><ul><li>Flow control. </li></ul><ul><li>Breaking up messages into a smaller chunks (and reassembly.) </li></ul><ul><li>Multiplexing messages on same connection. </li></ul><ul><li>Routing - how to get from one host to another. </li></ul>Connection Both Directions Simultaneous Simplex No No Half duplex Yes No Full duplex Yes Yes
  37. 49. <ul><li>Connection oriented service: </li></ul><ul><ul><li>Like the phone system. The system establishes a connection, uses it, and closes it. Acts like a tube. Data comes out the other end in the same order as it goes in. </li></ul></ul><ul><ul><ul><ul><ul><li>Connection Setup </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Data Transfer </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Connection Termination </li></ul></ul></ul></ul></ul><ul><li>Connectionless service: </li></ul><ul><ul><li>Like the post office. Each message has the entire address on it. Each message may follow a different route to its destination. Ordering not maintained. </li></ul></ul><ul><ul><ul><ul><ul><li>Data Transfer </li></ul></ul></ul></ul></ul>
  38. 50. <ul><li>Quality of service (QoS): </li></ul><ul><ul><li>Will the message arrive? </li></ul></ul><ul><ul><ul><li>A reliable connection-oriented service guarantees success. </li></ul></ul></ul><ul><ul><ul><ul><li>Message sequence - message boundaries and order are maintained. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Byte streams - messages are broken up or combined; flow is bytes. Can pair mechanism with upper-layer requirements. </li></ul></ul></ul></ul><ul><li>Datagram Service: </li></ul><ul><ul><li>Like junk mail. It's not worth the cost to determine if it actually arrived. Needs a high probability of arrival, but 100% not required. Connectionless, no acknowledgment. </li></ul></ul><ul><li>Acknowledged datagram service: </li></ul><ul><ul><li>As above, but improved reliability via acknowledgment. </li></ul></ul><ul><li>Request-reply service: </li></ul><ul><ul><li>Acknowledgment is in the form of a reply. </li></ul></ul>
  39. 51. <ul><li>Summary of six different types of service. </li></ul>
  40. 52. <ul><li>Service Primitives for connection-oriented service </li></ul><ul><ul><li>Example </li></ul></ul>Connect.indication Connect.request Connect.confirm Data.indication Data.request Data.request Data.indication Disconnect.indication Disconnect.request Disconnect.confirm
  41. 53. <ul><li>Example: Connection-Oriented </li></ul>
  42. 54. <ul><li>Computers (desktop PC, PDA, shared peripherals </li></ul><ul><li>Entertainment (TV, DVD, VCR, camera, stereo, MP3) </li></ul><ul><li>Telecomm (telephone, cell phone, intercom, fax) </li></ul><ul><li>Appliances (microwave, fridge, clock, furnace, airco) </li></ul><ul><li>Telemetry (utility meter, burglar alarm, babycam). </li></ul>
  43. 55. <ul><li>Services are primitives that a layer provides for the layer above it. </li></ul><ul><li>Protocols are rules governing the meaning of frames/packets/messages exchanged with the peer entity. </li></ul>
  44. 57. <ul><li>Headers, Data, and Trailers </li></ul><ul><li>Encapsulation </li></ul>
  45. 58. <ul><li>The OSI Reference Model </li></ul><ul><li>The TCP/IP Reference Model </li></ul><ul><li>A Comparison of OSI and TCP/IP </li></ul><ul><li>A Critique of the OSI Model and Protocols </li></ul><ul><li>A Critique of the TCP/IP Reference Model </li></ul>
  46. 59. <ul><li>Comparison of OSI and TCP/IP </li></ul>
  47. 60. <ul><li>There are two competing models for how the software is layered. These are the OSI and the TCP models. </li></ul><ul><li>OSI (Open Systems Interconnection) </li></ul><ul><ul><li>Developed by ISO (International Standards Organization) </li></ul></ul><ul><ul><li>7 layers </li></ul></ul><ul><li>TCP (Transfer Control Protocol) </li></ul><ul><ul><li>Used in the Arpanet and in the Internet . Common mechanism that is surpassing the OSI Model. </li></ul></ul><ul><ul><li>5 layers </li></ul></ul>
  48. 61. <ul><li>Principles used to develop OSI Layering: </li></ul><ul><ul><li>1. Need a layer for each different level of abstraction. </li></ul></ul><ul><ul><li>2. Each layer performs a well defined function. </li></ul></ul><ul><ul><li>3. Each layer should be standardizable. </li></ul></ul><ul><ul><li>4. Layer boundaries should minimize data flow across those boundaries. </li></ul></ul><ul><ul><li>5. The right number of layers - don't put too many functions together, but not too many layers either. </li></ul></ul>
  49. 62. The OSI reference model.
  50. 63. Flow of data through the OSI Model
  51. 64. <ul><li> Physical Layer: </li></ul><ul><ul><li>Purpose: Transmits raw bits across a medium. </li></ul></ul><ul><ul><li>Electrical: Concerns are voltage, timing, duplexing, connectors, etc. </li></ul></ul><ul><li> Data Link Layer: </li></ul><ul><ul><li>Framing : Breaks apart messages into frames . Reassembles frames into messages. </li></ul></ul><ul><ul><li>Error handling : solves damaged, lost, and duplicate frames. </li></ul></ul><ul><ul><li>Flow control : keeps a fast transmitter from flooding a slow receiver. </li></ul></ul><ul><ul><li>Gaining Access : if many hosts have usage of the medium, how is access arbitrated. </li></ul></ul>
  52. 65. <ul><li> Network Layer: </li></ul><ul><ul><li>Routing : What path is followed by packets from source to destination. Can be based on a static table, when the connection is created, or when each packet is sent. </li></ul></ul><ul><ul><li>Congestion : Controls the number packets in the subnet. </li></ul></ul><ul><ul><li>Accounting : Counts packets/bytes for billing purposes. </li></ul></ul>
  53. 66. <ul><li> Transport Layer: </li></ul><ul><ul><li>Reliability : Ensures that packets arrive at their destination. Reassembles out of order messages. </li></ul></ul><ul><ul><li>Hides network : Allows details of the network to be hidden from higher level layers. </li></ul></ul><ul><ul><li>Service Decisions : What type of service to provide; error-free point to point, datagram, etc. </li></ul></ul><ul><ul><li>Mapping : Determines which messages belong to which connections. </li></ul></ul><ul><ul><li>Naming : &quot;Send to node ZZZ&quot; must be translated into an internal address and route. </li></ul></ul><ul><ul><li>Flow control : keeps a fast transmitter from flooding a slow receiver. </li></ul></ul><ul><ul><li>TCP (Transmission Control Protocol): provides a reliable connection oriented protocol that delivers a byte stream from one node to another. Guarantees delivery and provides flow control. </li></ul></ul><ul><ul><li>UDP (User Datagram Protocol) provides an unreliable connection-less protocol for applications that provide their own. </li></ul></ul>
  54. 67. <ul><li> Session Layer: </li></ul><ul><ul><li>Sessions : Provides services that span a particular message. For instance, a login session could be logged. </li></ul></ul><ul><ul><li>Synchronization : Provide way to subdivide a long mechanism for reliability. </li></ul></ul><ul><li> Presentation Layer: </li></ul><ul><ul><li>Prettiness : Syntax and Jamul Miss. body is.of information transmitted. Understands the nature of the data being transmitted. Converts ASCII/EBCDIC, big endian/little endian </li></ul></ul><ul><li> </li></ul><ul><ul><li>Interfacing : Terminal type translation. </li></ul></ul><ul><ul><li>File transfer : Programs able to understand directory structures and naming conventions and map them onto various systems. </li></ul></ul>
  55. 68. <ul><li>Data Transmission in the OSI Model </li></ul>
  56. 69. <ul><li> Internet Layer </li></ul><ul><ul><li>Connector : Provides packet switched connectionless service. </li></ul></ul><ul><ul><li>Routing : The IP (Internet Protocol) does delivery and congestion control. </li></ul></ul><ul><li> Transport Layer </li></ul><ul><ul><li>TCP (Transmission Control Protocol): provides a reliable connection oriented protocol that delivers a byte stream from one node to another. Guarantees delivery and provides flow control. </li></ul></ul><ul><ul><li>UDP (User Datagram Protocol) provides an unreliable connection-less protocol for applications that provide their own. </li></ul></ul>
  57. 70. <ul><li> Application Layer </li></ul><ul><ul><li>Terminal Telnet </li></ul></ul><ul><ul><li>File transfer FTP </li></ul></ul><ul><ul><li>The Web HTTP </li></ul></ul><ul><ul><li>Mail SMTP </li></ul></ul>
  58. 74. <ul><li>The relationship between a service and a protocol. </li></ul>
  59. 75. <ul><li>Protocols and networks in the TCP/IP model initially. </li></ul>
  60. 76. <ul><li>Why OSI did not take over the world </li></ul><ul><li>Bad timing </li></ul><ul><li>Bad technology </li></ul><ul><li>Bad implementations </li></ul><ul><li>Bad politics </li></ul>
  61. 77. <ul><li>The apocalypse of the two elephants. </li></ul>
  62. 78. <ul><li>Problems: </li></ul><ul><li>Service, interface, and protocol not distinguished </li></ul><ul><li>Not a general model </li></ul><ul><li>Host-to-network “layer” not really a layer </li></ul><ul><li>No mention of physical and data link layers </li></ul><ul><li>Minor protocols deeply entrenched, hard to replace </li></ul>
  63. 79. <ul><li>The hybrid reference model to be used in this book. </li></ul>
  64. 80. <ul><li>The Internet </li></ul><ul><li>Connection-Oriented Networks: X.25, Frame Relay, and ATM </li></ul><ul><li>Ethernet </li></ul><ul><li>Wireless LANs: 802:11 </li></ul>
  65. 81. <ul><li>(a) Structure of the telephone system. </li></ul><ul><li>(b) Baran’s proposed distributed switching system. </li></ul>
  66. 82. <ul><li>The original ARPANET design. </li></ul>
  67. 83. <ul><li>Growth of the ARPANET (a) December 1969. ( b) July 1970. </li></ul><ul><li>(c) March 1971. (d) April 1972. (e) September 1972. </li></ul>
  68. 84. <ul><li>The NSFNET backbone in 1988. </li></ul>
  69. 85. <ul><li>Traditional applications (1970 – 1990) </li></ul><ul><li>E-mail </li></ul><ul><li>News </li></ul><ul><li>Remote login </li></ul><ul><li>File transfer </li></ul>
  70. 86. <ul><li>Overview of the Internet. </li></ul>
  71. 87. <ul><li>A virtual circuit. </li></ul>
  72. 88. <ul><li>An ATM cell. </li></ul>
  73. 89. <ul><li>The ATM reference model. </li></ul>
  74. 90. <ul><li>The ATM layers and sublayers and their functions. </li></ul>
  75. 91. <ul><li>Architecture of the original Ethernet. </li></ul>
  76. 92. <ul><li>(a) Wireless networking with a base station. </li></ul><ul><li>(b) Ad hoc networking. </li></ul>
  77. 93. <ul><li>The range of a single radio may not cover the entire system. </li></ul>
  78. 94. <ul><li>A multicell 802.11 network. </li></ul>
  79. 95. <ul><li>Who’s Who in the Telecommunications World </li></ul><ul><li>Who’s Who in the International Standards World </li></ul><ul><li>Who’s Who in the Internet Standards World </li></ul>
  80. 96. <ul><li>Main sectors </li></ul><ul><ul><li>Radio communications </li></ul></ul><ul><ul><li>Telecommunications Standardization </li></ul></ul><ul><ul><li>Development </li></ul></ul><ul><li>Classes of Members </li></ul><ul><ul><li>National governments </li></ul></ul><ul><ul><li>Sector members </li></ul></ul><ul><ul><li>Associate members </li></ul></ul><ul><ul><li>Regulatory agencies </li></ul></ul>
  81. 97. The 802 working groups. The important ones are marked with *. The ones marked with  are hibernating. The one marked with † gave up.
  82. 98. <ul><li>The principal metric prefixes. </li></ul>