Chapter One

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Chapter One

• Introduction to Computer Networks and Data
  Communications

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Introduction
Chapter One - Introduction to Computer Networks
And Data Communications

• 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

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The Language of Computer Networks
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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Computer Networks Basic Connections
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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Basic Connections Microcomputer to Local Area
Network
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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Basic Connections Microcomputer to Internet
Chapter One - Introduction to Computer Networks
And Data Communications

• Popular with home users and small businesses
• Often a dial-up modem is used to connect users
  microcomputer to an Internet service provider
• Technologies such as DSL and cable modems are
  replacing modems

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Chapter One - Introduction to Computer Networks
And Data Communications
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Basic Connections Local Area Network to Local
Area Network
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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Basic Connections Personal Area Network to
Workstation
Chapter One - Introduction to Computer Networks
And Data Communications

• Interconnects wireless devices such as PDAs,
  laptops and notebooks, and music playback devices
• Used over short distances such as a few meters

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Chapter One - Introduction to Computer Networks
And Data Communications
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Basic Connections Local Area Network to
Metropolitan Area Network
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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Basic Connections Local Area Network to Wide
Area Network
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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Basic Connections Wide Area Network to Wide
Area Network
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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Basic Connections Satellite and Microwave
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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Basic Connections Wireless or Cellular
Telephones
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications
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An Additional Basic Connection Telephone to
Network
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
Chapter One - Introduction to Computer Networks
And Data Communications

• The OSI models seven layers

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Network Architectures - OSI
Chapter One - Introduction to Computer Networks
And Data Communications

• Application layer where the application using
  the network resides. Common network applications
  include web browsing, e-mail, file transfers, and
  remote logins
• Presentation layer performs a series of
  miscellaneous functions necessary for presenting
  the data package properly to the sender or
  receiver

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Network Architectures - OSI
Chapter One - Introduction to Computer Networks
And Data Communications

• 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.
• 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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Network Architectures - OSI
Chapter One - Introduction to Computer Networks
And Data Communications

• 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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Chapter One - Introduction to Computer Networks
And Data Communications
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Network Architectures
Chapter One - Introduction to Computer Networks
And Data Communications

• The TCP/IP protocol suite (DoD protocol suite,
  Internet model)

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Network Architectures TCP/IP
Chapter One - Introduction to Computer Networks
And Data Communications

• Application layer equivalent to OSIs
  application and presentation layers
• Transport layer equivalent to OSIs transport
  layer
• Network (Internet or internetwork) layer
  equivalent to OSIs network layer
• Network access (data link/physical) layer
  equivalent to OSIs data link and physical layers

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Network Architectures
Chapter One - Introduction to Computer Networks
And Data Communications

• 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 Computer Networks
And Data Communications

• Logical and physical connections

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Chapter One - Introduction to Computer Networks
And Data Communications

• Example of data flow through layers

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Chapter One - Introduction to Computer Networks
And Data Communications

• Network connections in action

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The TCP/IP protocol suite in action
Chapter One - Introduction to Computer Networks
And Data Communications

• 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
• The adding of information over pre-existing
  information is termed encapsulation

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Chapter One - Introduction to Computer Networks
And Data Communications