1 Chapter One Introduction to Computer Networks and Data Communications.

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Chapter One

Introduction to Computer Networks and Data Communications

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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 ComputerNetworks And Data Communications

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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 areas

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

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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

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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

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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

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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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

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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Basic Connections – Personal Area Network to Workstation

• Interconnects wireless devices such as PDAs (personal

digital assistant ), laptops and notebooks, and music playback devices.

• Used over short distances such as a few meters

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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)

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Chapter One - Introduction to ComputerNetworks And Data Communications

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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

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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

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Network Architectures• The OSI model’s seven layers:

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Network Architectures• The TCP/IP protocol suite (DoD protocol suite, Internet

model):

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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

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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

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Chapter One - Introduction to ComputerNetworks And Data Communications

• Logical and physical connections

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Chapter One - Introduction to ComputerNetworks And Data Communications

• Example of data flow through layers

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Chapter One - Introduction to ComputerNetworks And Data Communications

• Network connections in action