Chapter 1
Introduction to Computer
Networks and Data
Communications
Communication
The transmission of a signal by way of a
medium from sender to receiver
Sender
Signal
Receiver
Transmission
medium
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Communication Problems
 Completeness & comprehension
 Attenuation & noises
 Competing resources
 Routing & addressing
 Security
3
Networks
 Computer network
 Voice network
 Data network
 Local area network
 Metropolitan area network
 Wide area network
 Personal area network
 Network management
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Data Communications
 Data Communications:
 The movement of computer information (data)
from one point to another by means of electrical
or optical transmission systems
 Is a sub-field of telecommunications
 Telecommunications:
 Includes the transmission of voice and video as
well as data
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Network Configurations
 Microcomputer-to-local area network
 Microcomputer-to-Internet
 Local area network-to-local area network
 Personal area network-to-workstation
 Local area network-to-metropolitan area network
 Local area network-to-wide area network
 Wide area network-to-wide area network
 Sensor-to-local area network
 Satellite and microwave
 Cell phones
 Terminal/microcomputer-to-mainframe computer
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Convergence
 An Additional Basic Connection – telephone-
to-network



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 Components
 Hardware
 Computer
 Network Interface Card (NIC)
 Hub
 Switch
 Bridge
 Router
 Software
 Network protocols
8
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
likelihood that different components from different
manufacturers will converse
 Two models to learn: OSI model and TCP/IP
protocol suite
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The OSI Model
Application
(7) User input to host
Presentation
(6) Data coding, formatting
Session
(5) Begin, frames, end, rules
Transport
(4) End-to-end delivery
Network
(3) Message routing
Datalink
(2) Frame formatting, error
Physical
(1) Physical connections
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OSI vs. The Internet
Application
Application
Application
Transport
Transport
Transport
Network
Network
Network
Presentation
Session
Datalink
Physical
Interface
Network Access
Physical
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Logical vs. Physical Connection
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Datalink
Datalink
Physical
Physical
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