1 Chapter One Introduction to Computer Networks and Data Communications

2 Introduction Who today has not used a computer network? Mass transit, interstate highways, 24-hour bankers, grocery stores, cable television, cellphones, businesses and schools, and retail outlets support some form of computer network Chapter One - Introduction to Computer Networks And Data Communications

3 The Language of Computer Networks Computer network – an interconnection of computers and computing equipment using either wires or radio waves over small or large geographic areas Local area network – networks that are small in geographic size spanning a room, floor, building, or campus Chapter One - Introduction to Computer Networks And Data Communications

4 The Language of Computer Networks Metropolitan area network – networks that serve an area of 1 to 30 miles, approximately the size of a typical city Wide area network – a large network that encompasses parts of states, multiple states, countries, and the world Chapter One - Introduction to Computer Networks And Data Communications

5 The Language of Computer Networks Personal area network – a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices Voice network – a network that transmits telephone signals Data network – a network that transmits computer data Chapter One - Introduction to Computer Networks And Data Communications

6 The Language of Computer Networks Data communications – the transfer of digital or analog data using digital or analog signals Telecommunications – the study of telephones and the systems that transmit telephone signals Network management – the design, installation, and support of a network, including its hardware and software Chapter One - Introduction to Computer Networks And Data Communications

7 The Big Picture Networks are composed of many devices, including: –Workstations (computers, telephones) –Servers –Network hubs and switches (bridges) –Routers (LAN to WAN and WAN to WAN) –Telephone switching gear Chapter One - Introduction to Computer Networks And Data Communications

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9 Computer Networks – Basic Connections Computer terminal / microcomputer to mainframe Microcomputer to local area network Microcomputer to Internet Local area network to local area network Personal area network to workstation Chapter One - Introduction to Computer Networks And Data Communications

10 Computer Networks – Basic Connections Local area network to metropolitan area network Local area network to wide area network Sensor to local area network Satellite and microwave Wireless telephone and wired telephone to network Chapter One - Introduction to Computer Networks And Data Communications

11 Basic Connections – Computer Terminal / Microcomputer to Mainframe Computer Predominant form in the 1960s and 1970s Still used in many types of businesses for data entry and data retrieval Usually involves a low-speed connection Chapter One - Introduction to Computer Networks And Data Communications

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13 Basic Connections – Microcomputer to Local Area Network Highly common throughout business and academic environments, and now homes Typically a medium- to high-speed connection Computer (device) requires a NIC (network interface card) NIC connects to a hub-like device Chapter One - Introduction to Computer Networks And Data Communications

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15 Basic Connections – Microcomputer to Internet Popular with home users and small businesses Often a dial-up modem is used to connect user’s microcomputer to an Internet service provider Technologies such as DSL and cable modems are replacing modems Chapter One - Introduction to Computer Networks And Data Communications

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17 Basic Connections – Local Area Network to Local Area Network Found in systems that have two or more LANs and a need for them to intercommunicate A bridge-like device (such as a switch) is typically used to interconnect LANs Switch can filter frames Chapter One - Introduction to Computer Networks And Data Communications

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19 Basic Connections – Personal Area Network to Workstation Interconnects wireless devices such as PDAs, laptops and notebooks, and music playback devices Used over short distances such as a few meters Chapter One - Introduction to Computer Networks And Data Communications

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21 Basic Connections – Local Area Network to Metropolitan Area Network Used to interconnect companies (usually their local area networks) to networks that encompass a city High-speed networks with redundant circuits Metro Ethernet is latest form of metropolitan LAN Chapter One - Introduction to Computer Networks And Data Communications

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23 Basic Connections – Local Area Network to Wide Area Network One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network) A router is the typical device that performs LAN to WAN connections Routers are more complex devices than switches Chapter One - Introduction to Computer Networks And Data Communications

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25 Basic Connections – Wide Area Network to Wide Area Network High-speed routers and switches are used to connect one wide area network to another Thousands of wide area networks across North America, many interconnected via these routers and switches Chapter One - Introduction to Computer Networks And Data Communications

26 Basic Connections – Sensor to Local Area Network Not all local area networks deal with microcomputer workstations Often found in industrial and laboratory environments Assembly lines and robotic controls depend heavily on sensor-based local area networks Chapter One - Introduction to Computer Networks And Data Communications

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28 Basic Connections – Satellite and Microwave Typically long distance wireless connections Many types of applications including long distance telephone, television, radio, long-haul data transfers, and wireless data services Typically expensive services but many companies offer competitive services and rates Newer shorter-distance services such as Wi-Max Chapter One - Introduction to Computer Networks And Data Communications

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30 Basic Connections – Wireless or Cellular Telephones Constantly expanding market across the U.S. and world Third generation services available in many areas and under many types of plans Newest generation includes higher speed data transfers (100s of kilobits per second) Chapter One - Introduction to Computer Networks And Data Communications

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32 An Additional Basic Connection – Telephone to Network Telephone systems are ubiquitous and now carry more data than voice Common configuration – telephone connected to POTS Newer configuration (VoIP) – telephone to LAN via gateway or telephone to gateway via DSL/cable Chapter One - Introduction to Computer Networks And Data Communications

33 Network Architectures A reference model that describes the layers of hardware and software necessary to transmit data between two points or for multiple devices / applications to interoperate Reference models are necessary to increase likelihood that different components from different manufacturers will converse Two models to learn: OSI model and TCP/IP protocol suite Chapter One - Introduction to Computer Networks And Data Communications

34 Network Architectures The OSI model’s seven layers: Chapter One - Introduction to Computer Networks And Data Communications

35 Network Architectures - OSI Application layer – where the application using the network resides. Common network applications include web browsing, , file transfers, and remote logins Presentation layer – performs a series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver Chapter One - Introduction to Computer Networks And Data Communications

36 Network Architectures - OSI Session layer – responsible for establishing sessions between users Transport layer – provides an end-to-end error-free network connection. Makes sure the data arrives at the destination exactly as it left the source. Network layer – responsible for creating, maintaining and ending network connections. Transfers a data packet from node to node within the network. Chapter One - Introduction to Computer Networks And Data Communications

37 Network Architectures - OSI Data link layer – responsible for taking the data and transforming it into a frame with header, control and address information, and error detection code Physical layer – handles the transmission of bits over a communications channel. Includes voltage levels, connectors, media choice, modulation techniques Chapter One - Introduction to Computer Networks And Data Communications

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39 Network Architectures The TCP/IP protocol suite (DoD protocol suite, Internet model): Chapter One - Introduction to Computer Networks And Data Communications

40 Network Architectures – TCP/IP Application layer – equivalent to OSI’s application and presentation layers Transport layer – equivalent to OSI’s transport layer Network (Internet or internetwork) layer – equivalent to OSI’s network layer Network access (data link/physical) layer – equivalent to OSI’s data link and physical layers Chapter One - Introduction to Computer Networks And Data Communications

41 Network Architectures Logical and physical connections – A logical connection is one that exists only in the software, while a physical connection is one that exists in the hardware Note that in a network architecture, only the lowest layer contains the physical connection, while are higher layers contain logical connections Chapter One - Introduction to Computer Networks And Data Communications

42 Chapter One - Introduction to Computer Networks And Data Communications Logical and physical connections

43 Chapter One - Introduction to Computer Networks And Data Communications Example of data flow through layers

44 Chapter One - Introduction to Computer Networks And Data Communications Network connections in action

45 The TCP/IP protocol suite in action Note the flow of data from user to web browser and back At each layer, information is either added or removed, depending on whether the data is leaving or arriving at a workstation The adding of information over pre-existing information is termed encapsulation Chapter One - Introduction to Computer Networks And Data Communications

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