Chapter 1: Introduction to Computer Networks and Data Communications Data Communications and Computer Networks: A Business User’s Approach Third Edition.

Chapter 1:

Introduction to Computer Networks

and Data Communications

Data Communications andComputer Networks: A Business User’s ApproachThird Edition

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Objectives

After reading this chapter, you should be able to:

• Define the basic terminology of computer networks

• Recognize the individual components of the big picture of computer networks

• Outline the basic network configurations

• Cite the reasons for using a network model and explain how they apply to current network systems

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Objectives (continued)

• List the layers of the OSI model and describe the duties of each layer

• List the layers of the TCP/IP protocol suite and describe the duties of each layer

• Compare the OSI model and TCP/IP protocol suite and list their differences and similarities

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• Who today has not used a computer network?

• Mass transit, interstate highways, 24-hour bankers, grocery stores, cable television, cellular telephones, most businesses and schools, and other retail outlets can support some form of computer networks

Introduction

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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 distances

• Local area network - networks that are small in geographic size spanning a room, building, or campus

• Metropolitan area network - networks that serve an area of 3 to 30 miles - approximately the area of a typical city

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The Language of Computer Networks

•Wide area network - a large network that encompasses parts of states, multiple states, countries, and the world

•Data communications - the transfer of digital or analog data using digital or analog signals

•Voice network - a network that transmits telephone signals

•Data network - a network that transmits computer data

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The Language of Computer Networks (continued)

•Telecommunications - the study of telephones and the systems that transmit telephone signals

•Network management - the design, installation, and support of a network and its hardware and software

•Personal area network – a network of a few meters, between wireless devices such as PDAs, laptops, and similar devices

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The Big Picture of Networks

•Networks are composed of many devices, including:

• Workstations (computers and telephones)

• Servers

• Network hubs and switches (bridges)

• Routers (LAN-WAN and WAN-WAN)

• Telephone switching gear

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The Big Picture of Networks (continued)

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Computer Networks - Basic Configurations

• Computer terminal/microcomputer to mainframe computer

• Microcomputer to local area network

• Microcomputer to Internet

• Local area network to local area network

• Personal area network to workstation

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Computer Networks – Basic Configurations(continued)

•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

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Terminal/microcomputer-to-mainframe Computer Configurations

• 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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Terminal/microcomputer-to- mainframe Computer Configurations (continued)

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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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Microcomputer-to-local Network Configurations (continued)

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Microcomputer-to-Internet Configurations

• 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 and cable modems are replacing modems

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Microcomputer-to-Internet Configurations (continued)

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Local Area Network-to-Local Area Network Configurations (continued)

• Found in businesses and schools 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

• Bridge-like device can filter frames

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Local Area Network-to-Local Area Network Configurations (continued)

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Personal Area Network-to-Workstation Configurations

• Interconnects wireless devices such as PDAs, laptops, and music playback devices

• Used over a short distance such as a few meters

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Personal Area Network-to-Workstation Configurations (continued)

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Local Area Network-to-MetropolitanArea Network Configurations

• Used to interconnect companies (usually their local area networks) to networks that encompass a metropolitan city

• High speed networks with redundant circuits

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Local Area Network-to-Metropolitan Area Network Configurations (continued)

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Local Area Network-to-Wide Area Network Configurations

• One of the most common ways to interconnect a user on a LAN workstation to the Internet (a wide area network)

• Router

• Typical device that performs LAN to WAN connections

• More complex devices than bridges/switches

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Local Area Network-to-Wide Area NetworkConfigurations (continued)

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Wide Area Network-to-Wide Area Network Network Configurations

• 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

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Sensor-to-Local Area Network Configurations

• 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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Sensor-to-Local Area Network Configurations (continued)

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Satellite and Microwave Configurations

• 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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Satellite and Microwave Configurations (continued)

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Wireless Telephone Configurations

• Constantly expanding market across the U.S. and world

• Second generation PCS services available in most areas and under many types of plans

• Next generation services beginning to replace PCS phones

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Wireless Telephone Configurations (continued)

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Wireless Telephone Configurations (continued)

• An additional basic configuration is telephone to network

• Telephone systems are ubiquitous and can now carry more data than voice

• Common configuration – telephone connected to POTS

• Newer configuration – telephone to LAN via gateway (VoIP)

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Network Architectures

• 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 the likelihood that different components from different manufacturers will converse

• Two architectures are required learning: The OSI Model, and the TCP/IP protocol suite

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The Open Systems Interconnection (OSI) model

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The Open Systems Interconnection (OSI) model (continued)

•Application layer - where the application using the network resides

•Common network applications include remote login, file transfer, e-mail, and web page browsing

•Presentation layer - performs series of miscellaneous functions necessary for presenting the data package properly to the sender or receiver

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The Open Systems Interconnection (OSI) model (continued)

Session layer - responsible for establishing sessions between users

•Transport layer - provides end-to-end error-free network connection

•Makes sure data arrives at 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

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The Open Systems Interconnection (OSI) model (continued)

•Data link layer - responsible for taking data and transforming it into a frame with header, control and address information, as well as 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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The Open Systems Interconnection (OSI) model (continued)

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The TCP/IP Protocol Suite

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The TCP/IP Protocol Suite (continued)

•Application layer - equivalent to the OSI’s presentation and application layers

•Transport layer - performs same function as OSI transport layer

•Network (Internet or internetwork) layer - roughly equivalent to the OSI’s network layer

•Network access (data link/physical) layer - equivalent to the OSI’s physical and data link layers

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Logical and Physical Connections

•Logical connection – exists only in the software

•Physical connection – exists in the hardware

• In a network architecture

•Only lowest layer contains physical connection

•All higher layers contain logical connections

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Logical and Physical Connections (continued)

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Logical and Physical Connections (continued)

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Network Configurations in Action

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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

• Depends on whether data is leaving or arriving at a workstation

• Encapsulation - adding information over pre-existing information

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The TCP/IP Protocol Suite in Action (continued)

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Summary

• Basic terminology of computer networks

• Individual components of computer networks

• Basic network configurations

• Network models and how they apply to current network systems

• Layers of the OSI model and the TCP/IP protocol suite