Introduction to Computer Networks and Data Communications

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Data Communications and Computer Networks A
Business Users Approach

• Chapter 1
• Introduction to Computer Networks and Data
  Communications

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Data Communications and Computer Networks
Chapter 1

• Introduction
• Who today has not used a computer network?
• Mass transit, interstate highways, 24-hour
  bankers, grocery stores, cable television,
  pagers, mobile telephones, most businesses and
  schools, and other retail outlets can support
  some form of computer networks.

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Data Communications and 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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Data Communications and Computer Networks
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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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Data Communications and Computer Networks
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• The Language of Computer Networks
• 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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Data Communications and Computer Networks
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• The Big Picture of Networks
• Networks are composed of many devices,
  including
• workstations (computers and telephones)
• network servers
• network hubs and switches (bridges)
• routers (LAN-WAN and WAN-WAN)
• telephone switching gear

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Data Communications and Computer Networks
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Data Communications and Computer Networks
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• Computer Networks - Basic Configurations
• Computer terminal to mainframe computer
• Microcomputer to mainframe computer
• Microcomputer to local area network
• Microcomputer to Internet
• Local area network to local area network

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Data Communications and Computer Networks
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• Computer Networks - Basic Configurations
• Local area network to metropolitan area network
• Personal area network to workstation
• 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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Data Communications and Computer Networks
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Basic Configurations Computer terminal to
mainframe computer 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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Configurations 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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Configurations Microcomputer to
Internet 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.
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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Configurations Local Area Network to
Local Area Network Found in businesses and
schools that have two or more LANs and a need for
them to intercommunicate. A bridge-like device is
typically used to interconnect LANs. Bridge-like
device can filter frames
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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Configurations Personal Area Network to
Workstation 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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Configurations Local Area Network to
Metropolitan Area Network Used to interconnect
companies (usually local area networks) to
networks that encompass a metropolitan city High
speed networks with redundant circuits
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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Configurations 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 bridges/switches
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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Configurations 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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Configurations Satellite and
Microwave 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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Data Communications and Computer Networks
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Basic Configurations Mobile Telephones Quickly
expanding market across the U.S. and world. First
generation analog services and second generation
PCS services available in most areas and under
many types of plans. Third generation services
beginning to appear in Europe and Asia.
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Data Communications and Computer Networks
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Basic Configurations 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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Data Communications and Computer Networks
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• Network Architectures
• A reference model that describes the layers of
  hardware and software necessary to transmit data
  between two points
• Reference models are necessary to increase the
  likelihood that different components from
  different manufacturers will converse
• There are two architectures that are required
  learning The OSI Model, and the TCP/IP protocol
  suite

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Data Communications and Computer Networks
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• Network Architectures
• The OSI Models seven layers

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Data Communications and Computer Networks
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• Network Architectures
• 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 a series of
  miscellaneous functions necessary for presenting
  the data package properly to the sender or
  receiver

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Data Communications and Computer Networks
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• Network Architectures
• 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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Data Communications and Computer Networks
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• Network Architectures
• 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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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• Network Architectures
• The TCP/IP protocol suite (DoD protocol suite)

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Data Communications and Computer Networks
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• Network Architectures
• 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

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Data Communications and Computer Networks
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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 a physical connection,
  while all higher layers contain logical
  connections.

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Data Communications and Computer Networks
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• Network Architectures
• Logical and physical connections

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Data Communications and Computer Networks
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Network Configurations in Action
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Data Communications and Computer Networks
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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, 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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Data Communications and Computer Networks
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• Review Questions
• A user is sitting at work using a laptop
  computer with a wireless connection into the
  corporate LAN. The user is sending email. What
  basic configurations are being used?
• List the seven OSI layers with a quick
  description of each layer.
• List the TCP/IP layers with a quick description
  of each layer.
• What is the difference between a logical and a
  physical interface / connection?