Introduction to Computer Networks

1
Data Communications and Computer Networks A
Business Users Approach Third Edition

• Chapter 1
• Introduction to Computer Networks
• and Data Communications

2
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

3
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

4
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

5
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

6
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

7
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

8
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)


10
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 (co
ntinued)

• 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

12
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

13
Terminal/microcomputer-to-
mainframe Computer Configurations
(continued)

14
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

15
Microcomputer-to-local Network
Configurations (continued)

16
Microcomputer-to-Internet Configurations

• Very popular with home users and some small
  businesses
• Typically, a dial-up modem is used to connect
  users microcomputer to an Internet service
  provider
• Newer technologies such as DSL and cable modems
  are replacing modems

17
Microcomputer-to-Internet
Configurations
(continued)

18
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

19
Local Area Network-to-Local Area Network
Configurations (continued)

20
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

21
Personal Area Network-to-Workstation
Configurations (continued)

22
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

23
Local Area Network-to-Metropolitan Area
Network Configurations (continued)


24
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

25
Local Area Network-to-Wide Area
Network Configurations (continued)


26
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

27
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

28
Sensor-to-Local Area Network
Configurations (continued)

29
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

30
Satellite and Microwave Configurations
(continued)

31
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

32
Wireless Telephone Configurations
(continued)

33
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)

34
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

35
The Open Systems Interconnection
(OSI) model

36
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

37
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

38
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

39
The Open Systems Interconnection (OSI)
model (continued)

40
The TCP/IP Protocol Suite

41
The TCP/IP Protocol Suite (continued)

• Application layer - equivalent to the OSIs
  presentation and application layers
• Transport layer - performs same function as OSI
  transport layer
• Network (Internet or internetwork) layer -
  roughly equivalent to the OSIs network layer
• Network access (data link/physical) layer -
  equivalent to the OSIs physical and data link
  layers

42
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

43
Logical and Physical Connections
(continued)

44
Logical and Physical Connections
(continued)

45
Network Configurations in Action

46
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

47
The TCP/IP Protocol Suite in Action
(continued)

48
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