networking lesson 01

8/9/2019 Networking Lesson 01

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Lesson - 1

Introduction to Computer Networks and

Data Communications


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Introduction Who today has notused 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 someform of 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 sizespanning 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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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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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 networka network of a few meters, between

wireless devices such as PDAs, laptops, and similar devices.


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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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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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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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Basic ConfigurationsComputer 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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Basic ConfigurationsMicrocomputer-to-

Local Area NetworkHighly 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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Basic ConfigurationsMicrocomputer-to-

InternetVery 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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Basic ConfigurationsLocal 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 filterframes


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Basic ConfigurationsPersonal AreaNetwork-to-Workstation

Interconnects wireless devices such as PDAs, laptops, and music

playback devicesUsed over a short distance such as a few meters


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Basic ConfigurationsLocal 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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Basic ConfigurationsLocal AreaNetwork-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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Basic ConfigurationsSensor-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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Basic ConfigurationsSatellite andMicrowave

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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Basic ConfigurationsMobile 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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Network Architecture Models

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 models that are required learning: The OSI Model,

and the Internet Model


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The OSI Models seven layers


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Network Architecture Models 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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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 exactlyas 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 Architecture Models 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 acommunications channel. Includes voltage levels, connectors,

media choice, modulation techniques.


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The Internet Model (DoD Model or TCP/IP Model)


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Application layer - equivalent to the OSIs presentation and

application layers

Transport layer - performs same function as OSI transport layer

Network layer - roughly equivalent to the OSIs network layer

Interface layer - equivalent to the OSIs physical and data link

layers


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Network Models in Action


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The Internet Model 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

Adding information over pre-existing information is termedencapsulation


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