Transcript Introduction

Data Communications and
Computer Networks: A
Business User’s Approach
Third Edition
Chapter 1:
Introduction to Computer Networks
and Data Communications
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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Introduction
• 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
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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-tomainframe 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-Metropolitan
Area 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 Network
Configurations (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
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