Chapter 06

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					Business Data Communications,
        Fourth Edition
       Chapter 6: Protocols
                       Learning Objectives
     • Describe the role of software in a data
       communications network
     • Define a protocol and how it is used in a
       network
     • Explain the Open Systems Interconnection
       (OSI) model
     • List the types of protocols
     • Differentiate between wide area and local
       area network protocols

Chapter 6: Protocols                          2
                       Learning Objectives
     • List and explain Internet protocols
     • Describe the difference among character-
       oriented, byte-count-oriented, and bit-
       oriented protocols, H.323, and X.25
       protocols
     • Describe the protocols and standards
       used in wireless networks
     • Describe the protocols used for Apple
       Macintosh networks

Chapter 6: Protocols                          3
                       Introduction
     • Early networks consisted of equipment
       from one manufacturer
     • Modern networks are made up of different
       equipment from different manufacturers
     • Rules are needed to allow the equipment
       to communicate over a network




Chapter 6: Protocols                          4
               The Role of Software in a
                       Network
     • Software is made up of programs that
       control data transmission
     • All devices run some type of software
     • Computers (servers), controllers, clients
       (including terminals) all use software in a
       WAN
     • Servers and clients use software in a LAN


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                            Protocols
     • Set of rules that defines how devices
       communicate
           – Translates codes within the devices
     • Three key elements of protocols
           – Syntax – format of data, transmission coding
             schemes
           – Semantics – control information
           – Timing – controlling flow of data on network, match
             device speeds on the network, provides sequencing
             for data
     • Early protocols were proprietary
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                              Protocols
     • Open Systems Interconnection (OSI) Model
       – A standard for communications systems
       – Composed of seven layers
                • Application layer – allows user access to the
                  network
                • Presentation layer – defines format of the data
                • Session layer – establishes and maintains network
                  connection
                • Transport layer – maintains connections between
                  networks


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                                   Protocols
     • Open Systems Interconnection Model
           – 7 Layers (cont.)
                • Network layer – creates packets, adds address
                  and routing information
                       – Route is the path data takes
                       – Adaptive versus dynamic routing
                       – Routing tables
                • Data link layer – establishes and controls physical
                  path, creates frames
                • Physical layer – concerned with hardware, makes
                  the physical connection


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                       Types of Protocols
     • Introduction
           – Different types for mainframe computers,
             personal computers, wireless networks
           – No standard set of protocol for all devices
           – Communications developed in an atmosphere
             of competition
           – Data link protocols – rules for implementing
             the data link layer


Chapter 6: Protocols                                   13
          Wide Area Network Protocols
     • Mainframe Computer Protocols
           – Character-Oriented Protocols
                •   Binary Synchronous Communications (BSC)
                •   Data sent as blocks of characters (synchronous)
                •   Used only for half-duplex transmission
                •   Uses special characters for control
           – Byte-Count-Oriented Protocols
                • Adds the number of characters instead of special control
                  characters
                • Digital Data Communication Message Protocol (DDCMP)




Chapter 6: Protocols                                                         14
                  Figure 6-6. BSC data with control characters.




                 Figure 6-7. Format for byte-count-oriented protocol.




Chapter 6: Protocols                                                    15
          Wide Area Network Protocols
     • Mainframe Computer Protocols
           – Bit-Oriented Protocols
                •   Data and control information put in frames
                •   Different protocols created by many companies
                •   SDLC – IBM
                •   HDLC – ISO Standard




                            Figure 6-8. HDLC, SDLC frame format.


Chapter 6: Protocols                                                16
          Wide Area Network Protocols
     • Mainframe Computer Protocols
           – Systems Network Architecture (SNA)
                • Originally used on IBM mainframe networks
                • Now used in other networks as well
                • Uses a layered model
                       – Old model – 5 layers
                       – Modern model – 7 layers
                       – More compatible with OSI model




Chapter 6: Protocols                                          17
      Figure 6-9. Comparison among old SNA, new SNA, and OSI layered Model.




Chapter 6: Protocols                                                      18
          Wide Area Network Protocols
     • Mainframe Computer Protocols
           – H.323 Protocol
                • Real-time audio, video, and data
                  communications on packet-switched
                  networks
                • Multimedia presentation over a network




Chapter 6: Protocols                                       19
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          Wide Area Network Protocols
           – Mainframe Computer Protocols
                • X.25 Protocol
                       – Packet switching protocol
                       – Uses only the bottom 3 layers of the OSI
                         model




Chapter 6: Protocols                                                21
                       Internet Protocols
     • Transmission Control Protocol/Internet
       Protocol (TCP/IP)
           – Developed in 1973 for ARPANET
           – The first Wide Area Network protocol
           – Five layer model
           – Data broken up in to packets
                • TCP segment
                • IP datagram



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                       Internet Protocols
     • Internet Protocol Version 6 (IPv6)
           – AKA Internet Protocol next generation (IPng)
           – Address length increased to 128 bits
           – Allows the addition of more Internet Web sites
           – Allows for growth for the Internet




Chapter 6: Protocols                                     25
                       Internet Protocols
     • Other Internet Protocols
           – File transfer protocol (ftp)
           – Hypertext transfer protocol (http)
           – Electronic Mail Protocols
                • X.400 (e-mail standard)
                • X.500 (public e-mail directory standard)
                • Post Office Protocol 3 (POP3) – e-mail downloaded to user’s
                  computer
                • Internet Message Access Protocol (IMAP) – e-mail stored on
                  server, even after it is read
                • Simple Mail Transfer Protocol (SMTP) – used for sending
                  only



Chapter 6: Protocols                                                       26
         Local Area Network Protocols
     • Local Area Network
           – Limited area
     • X.PC
           – Converts asynchronous data for transmission on a packet
             switching network
     • Ethernet
           – Contention access method
           – Carrier Sense Multiple Access with Collision Detection
             (CSMA/CD)
           – Fast Ethernet (100 Mbps)
           – Gigabit Ethernet (1 Gbps)
           – 10-Gigabit Ethernet (10 Gbps)



Chapter 6: Protocols                                                   27
         Local Area Network Protocols
     • Token Passing
           – Token
           – Token ring
           – 4Mbps or 16Mbps
           – Uses Multistation Access Unit (MAU)
           – Fast token ring (high-speed ring) (100 Mbps)
           – Fiber Distributed Data Interface (FDDI)



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Chapter 6: Protocols   30
         Local Area Network Protocols
     • Internetwork Packet Exchange/Sequenced
       Packet Exchange (IPX/SPX)
           – Used on Novell LANs
           – Incorporates features of discontinued Xerox
             Network System (XNS)
           – Uses lower 3 layers of OSI model
           – Data link layer divided
                • Logical Link Control (LLC)
                • Media Access Control (MAC)


Chapter 6: Protocols                                       31
Chapter 6: Protocols   32
       Wireless Protocols and Standards
     • Cellular Digital Packet Data (CDPD)
           – AKA Wireless IP protocol
           – Used on wireless packet switched networks
           – Uses radio frequencies, up to 19.2 Kbps
           – Allows multicast messages
           – Connects to the wired network as well




Chapter 6: Protocols                                     33
Chapter 6: Protocols   34
                       Wireless Protocols
     • Wireless Application Protocol (WAP)
           – Allows wireless devices to have Internet
             access
           – Browser exists on hand-held device
           – Server software is at the wireless service
             provider
           – Devices that adhere to the protocol are called
             “WAP-enabled”


Chapter 6: Protocols                                      35
                       Wireless Protocols
     • Infrared Data Association (IrDA)
           – Provides point-to-point link
           – PDAs, keyboards, mouse
           – Limitations on length of signal
           – Line of sight transmission




Chapter 6: Protocols                           36
                       Wireless Protocols
     • Third Generation (3G) of Mobile
       Communications
           – Technology for future wireless applications
           – Proposes standards
           – Voice and data communications technologies
             of the future
           – Propose to put W-CDMA on an IP network



Chapter 6: Protocols                                   37
                       Wireless Protocols
     • Bluetooth
           – Short-range radio links
           – Printers, mouse, keyboard connected to PC
             without wires
           – Bluetooth networks
                • Piconet – point-to-point between two devices
                • Scatternet – Two or more piconets communicating




Chapter 6: Protocols                                           38
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                       Wireless Protocols
     • Enhanced Data Rates for Global Evolution
       (EDGE)
           – Standard for GSM and TDMA networks
           – Transmission up to 384 Kbps
           – Part of the evolution to 3G




Chapter 6: Protocols                              41
                       Wireless Protocols
     • SyncML
           – Common language for synchronizing data on
             mobile devices
           – XML protocol
           – Mobile devices need to communicate with
             networks so synchronization is needed
           – Over 300 companies involved in developing
             SyncML


Chapter 6: Protocols                                 42
                       AppleTalk Protocol
     •   Used with Macintosh computers
     •   Uses CSMA/CA
     •   Uses a 7-layer model
     •   Interfaces with other LANs




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                       Summary
     • Networks made up of hardware and
       software
     • Software exists on every network device
     • Protocols are rules for communications
     • OSI is a model for protocol standards
     • Mainframe computer protocols differ from
       personal computer protocols


Chapter 6: Protocols                              45
                       Summary
     • Multimedia networks use the H.323 protocol
     • X.25 used on packet switching networks
     • Internet protocols include TCP/IP, IPv6, and
       several e-mail protocols
     • Local area network protocols include X.PC,
       Ethernet, and token ring
     • Wireless networks include CDPD and WAP
     • Macintosh networks use AppleTalk


Chapter 6: Protocols                                  46
Chapter 6 Complete

				
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