Transcript Data Communications and Computer Networks Chapter 1

Data Communications and
Computer Networks: A
Business User’s 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, cellular 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
Chapter 1
The Language of Computer Networks
• Wide area network - a large network that encompasses parts
of states, multiple states, countries, and the world
•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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Data Communications and Computer Networks
Chapter 1
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 and its hardware and software
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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)
• 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
Connections
• 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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Data Communications and Computer Networks
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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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Data Communications and Computer Networks
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Basic Connections – Computer
Terminal/Microcomputer 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 Connections – 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 Connections – Microcomputer to
Internet
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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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Basic Connections – 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 (such as a switch) 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 Connections – 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 Connections – Local Area
Network to Metropolitan Area Network
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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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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 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 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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Data Communications and Computer Networks
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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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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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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Data Communications and Computer Networks
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Data Communications and Computer Networks
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An Additional Basic Connection –
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 or for
multiple devices / applications to interoperate
• 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 Model’s 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 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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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 Architectures
• Example of data flow through layers
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Data Communications and Computer Networks
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Network Connections 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 connections 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?
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