Lecture Intro to Networks

7/27/2019 Lecture Intro to Networks

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P G D M T R I M E S T E R I

Computer Networks



Learning Objectives

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Define the basic terminology of computer networks

Recognize the individual components of the bigpicture of computer networks

Outline the basic network connections Define the term “convergence” and describe how it

applies to computer networks

Communication software and protocols

Network topology



Introduction

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Who today has not used a computer network?

Mass transit, interstate highways, 24-hour bankers,grocery stores, cable television, cell phones,

businesses and schools, and retail outlets supportsome form of computer network

Computer network – an interconnection of computers andcomputing equipment using either wires or radio waves

over small or large geographic areas



The Language of Computer Networks

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Types:

Personal area network – a network spanning an area of afew meters around an individual. Include devices such asPDAs, laptops, and wireless connections.

Local area network – networks that are small in geographicsize spanning a room, floor, building, or campus

Metropolitan area network – networks that serve an area ofupto 30 miles, approximately the size of a typical city

Wide area network – a large network that encompasses partsof states, multiple states, countries, and the world



The Language of Computer Networks (cont.)

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Voice network – a network that transmits telephonesignals

Data network – a network that transmits computerdata

The merging of voice and data networks is termedconvergence.



The Language of Computer Networks (cont.)

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Data communications – the transfer of digital oranalog data using digital or analog signals

Issues:

Data and Signal Multiplexing

Compression

Error detection and control

Network management – the design, installation, andsupport of a network, including its hardware andsoftware



The Big Picture of Networks

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The Big Picture of Networks

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Networks are composed of many devices, including:

Workstations (computers, telephones)

Servers (store network software and shared or private userfiles)

Network hubs and switches (bridges)

Routers (LAN to WAN and WAN to WAN)

Telephone switching gear

High speed transmission lines



Communications Networks – Basic Connections

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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

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



Terminal/Microcomputer-to-Mainframe ComputerConnections

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Predominant form inthe 1960s and 1970s

Still used in many

types of businessesfor data entry anddata retrieval

Usually involves a

low-speed connection



Microcomputer-to-Local Area NetworkConnections

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Highly common throughout business and academicenvironments, and now homes

Objective: Resource sharing

Typically a medium- to high-speed connection Computer (device) requires a NIC (network interface

card)

NIC connects to a hub-like device

Other issues:

Client/server system

Wireless LAN



Microcomputer-to-Local Area NetworkConnections

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Microcomputer-to-Internet Connections

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Popular with home users and small businesses

Often a dial-up modem is used to connect user’s microcomputer to anInternet service provider (ISP)

Technologies such as DSL and cable modems are replacing modems forhigher speeds.



LAN to LAN Connections

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Found in systems that have two or more LANs and aneed for them to intercommunicate

A bridge-like device (such as a switch) is typically

used to interconnect LANs Switch can filter out traffic.



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LAN to LAN Connections



PAN -to-Workstation Connections

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Interconnects wireless devices such as PDAs, laptopsand notebooks, and music playback devices

Used over short distances such as a few meters



LAN-to-MAN Connections

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Used to interconnect companies (usually their local area networks) tonetworks that encompass a city

High-speed networks using fiber-optic links

They can transfer data at fast, LAN speeds but over larger geographicregions than typically associated with a LAN.



LAN-to-WAN Connections

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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



WAN-to-WAN Connections

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High-speed routers and switches are used to connectone wide area network to another

Internet: Collection of thousands of networks.

Issues: Addressing



Sensor-to-Local Area Network Connections

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Often found in industrial and laboratory environments

Assembly lines and robotic controls depend heavily onsensor-based local area networks



Satellite and Microwave Connections

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Typically long distance wireless connections

Many types of applications including long distancetelephone, 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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Satellite and Microwave Connections

(continued)



Wireless Telephone Connections

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Constantly expanding market across the U.S. and world

Third generation services available in many areas

and under many types of plans



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Wireless Telephone Connections (continued)



CORPORATE NETWORK INFRASTRUCTURE

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Today’s corporatenetwork infrastructureis a collection of manydifferent networksfrom the public

switched telephonenetwork, to theInternet, to corporatelocal area networkslinking workgroups,

departments, or officefloors.



Convergence

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As a process of coming together toward single point. Voice transmission systems converging with data

transmission systems. – telephone-to-network Telephone systems are now carry more data than voice

Common configuration – telephone connected to POTSNewer configuration (VoIP) – telephone-to-LAN via gateway or

telephone to gateway via DSL/cable

Cell phones can act as Web phones

Television sets connect to Internet Wireless technologies combined in same device

enhance functionality



Packet switching

Method of slicing digital messages into parcels (packets), sendingpackets along different communication paths as they becomeavailable, and then reassembling packets at destination

Circuit-switched networks: requires complete point-to-point circuit as intelephone system.

Packet switched: More efficient use of network’s communicationscapacity

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Communications Software and Protocols

Communications protocol: set of rules that governs theexchange of information over a communications channel

The principal functions of protocols in a network are

Line access concerns how the sending device gains access to the

network to send a message. Collision avoidance refers to managing message transmission so that

two messages do not collide with each other on the network.

Other functions of protocols are

to identify each device in the communication path,

to verify correct receipt of the transmitted message,

to verify that a message requires retransmission because it cannot becorrectly interpreted, and

to perform recovery when errors occur.

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TCP/IP

The Transmission ControlProtocol/Internet Protocol(TCP/IP) is a protocol forsending information acrosssometimes-unreliable networks

with the assurance that it willarrive in uncorrupted form.

TCP/IP allows efficient andreasonably error freetransmission between differentsystems and is the standardprotocol of the Internet andintranets.

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TCP/IP

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Communications Software and Protocols

Common Telecommunications Protocols

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Communications Software

Network operating system (NOS): systems software that

controls computer systems and devices on a network and allows themto communicate with each other

Network-management software : It performs functions

that decrease the human resources needed to manage the network. These functions reduce time spent on routine tasks, such as remote,

electronic installation of new software on many devices across anetwork.

They also provide faster response to network problems, greater

control over the network, and remote diagnosing of problems indevices connected to the network.

Scans for viruses and Ensures compliance with software licenses

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Network Topology

The topology of a network is the physical layout andconnectivity of a network. Specific protocols, areoften used on specific topologies.

There are several basic network topologies: star,

bus,

ring,

mesh, and

hierarchical.

Networks that combine more than one type (such as a ringsegment connected to a star segment) are consideredhybrid topologies

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Network Topology

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Topology

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Lecture Intro to Networks

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