Data Communications & Computer Networks, Second Edition 1 Chapter 1 The Big Picture Introduction to Computer Networks and Data Communications

Data Communications & Computer Networks, Second Edition2 Who today has not used a computer network? Examples? Introduction

Data Communications & Computer Networks, Second Edition3 The Language of Computer Networks Computer network Local area network Metropolitan area network

Data Communications & Computer Networks, Second Edition4 The Language of Computer Networks Wide area network Personal area network Data communications

Data Communications & Computer Networks, Second Edition5 The Language of Computer Networks Voice network Data network Telecommunications Network management

Data Communications & Computer Networks, Second Edition6 The Big Picture of Networks Networks are composed of many devices, including:  workstations (computers and telephones)  network servers  network hubs and switches (bridges)  routers (LAN-WAN and WAN-WAN)  telephone switching gear

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8 Computer Networks - Basic Configurations Computer terminal-to-mainframe computer Microcomputer-to-mainframe computer Microcomputer-to-local area network Microcomputer-to-Internet Local area network-to-local area network Local area network-to-metropolitan area network Personal area network-to-workstation Local area network-to-wide area network Sensor-to-local area network Satellite and microwave Wireless telephone and wired telephone-to-network

Data Communications & Computer Networks, Second Edition9 Computer terminal to mainframe computer Predominant form in 60s and 70s. Still used in many types of businesses for data entry and data retrieval. Usually involves a low-speed connection.

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Data Communications & Computer Networks, Second Edition11 Microcomputer-to-Local Area Network Highly common throughout business and academic environments, and now even homes Typically a medium- to high-speed connection Microcomputer requires a NIC (network interface card) NIC connects to a hub-like device

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Data Communications & Computer Networks, Second Edition13 Microcomputer-to-Internet Very popular with home users and some small businesses Typically a dial-up modem is used to connect user’s microcomputer to an Internet service provider. Newer technologies such as DSL (digital subscriber line) and cable modems are replacing dial-up modems.

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Data Communications & Computer Networks, Second Edition15 Local Area Network-to-Local Area Network Found in businesses and schools that have two or more LANs and a need for them to intercommunicate. A bridge-like device is typically used to interconnect LANs. Bridge-like device can filter traffic

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Data Communications & Computer Networks, Second Edition17 Personal Area Network-to- Workstation Interconnects devices such as PDAs, laptops, and music playback devices using wired or wireless transmission Used over a short distance such as a few meters

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Data Communications & Computer Networks, Second Edition19 Local Area Network-to-Metropolitan Area Network Used to interconnect companies (usually local area networks) to networks that encompass a metropolitan city High speed networks with redundant circuits

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Data Communications & Computer Networks, Second Edition21 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 bridges/switches

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Data Communications & Computer Networks, Second Edition23 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.

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Data Communications & Computer Networks, Second Edition25 Satellite and Microwave 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.

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Data Communications & Computer Networks, Second Edition28 Network Architecture Models A reference model that describes the layers of hardware and software necessary to transmit data between two points. Reference models are necessary to increase the likelihood that different components from different manufacturers will converge. There are two models that are required learning: The OSI Model, and the Internet Model.

Data Communications & Computer Networks, Second Edition29 OSI Model Seven layers

Data Communications & Computer Networks, Second Edition30 OSI Seven Layers Application layer where the application using the network resides. Common network applications include remote login, file transfer, , and web page browsing. Presentation layer performs a series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver. 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.

Data Communications & Computer Networks, Second Edition31 OSI Seven Layers Network layer responsible for creating, maintaining and ending network connections. Transfers a data packet from node to node within the network 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.

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Data Communications & Computer Networks, Second Edition33 The Internet Model (TCP/IP Model)

Data Communications & Computer Networks, Second Edition34 OSI Model vs. Internet Model Application layer - equivalent to the OSI’s presentation and application layers Transport layer - performs same function as OSI transport layer Network layer - roughly equivalent to the OSI’s network layer Interface layer - equivalent to the OSI’s physical and data link layers

Data Communications & Computer Networks, Second Edition35 Logical and physical connections Logical and physical connections. Note that in a network architecture model, only the lowest layer contains a physical connection, while all higher layers contain logical connections

Data Communications & Computer Networks, Second Edition36 Network Models in Action

Data Communications & Computer Networks, Second Edition37 The Internet Model in Action See Figure 1-19 on pp. 25 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 Adding information over pre-existing information is termed encapsulation

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