Lecture 8 - Communications

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Introduction to Introduction to Communications’Communications’Technology & Technology & the Internetthe Internet

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ObjectivesObjectivesThe objectives of this session are to:The objectives of this session are to: Introduce the basic concepts in data Introduce the basic concepts in data

communicationscommunications;; Describe the different types of network;Describe the different types of network; Show the importance of data communications Show the importance of data communications

in modern business;in modern business; Describe the Internet Protocols;Describe the Internet Protocols; Define and contrast the Internet with Intranets Define and contrast the Internet with Intranets

and Extranets;and Extranets; Describe the various communications media Describe the various communications media

and their characteristics;and their characteristics;

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Reduces cost compared to traditional communications.Reduces cost compared to traditional communications. Reduces time for information transfer. Reduces time for information transfer. Enables sharing and dissemination of company Enables sharing and dissemination of company

information. information. Enables sharing of hardware resources such as printers, Enables sharing of hardware resources such as printers,

backup and processing power.backup and processing power. Promotes new ways of working. Promotes new ways of working. Operate geographically separate businesses as oneOperate geographically separate businesses as one. . Restructures relationships with partners. Restructures relationships with partners.

Benefits of Networks to Benefits of Networks to BusinessBusiness

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Setup and maintenance costs.Setup and maintenance costs. Implementation difficulties.Implementation difficulties. Reliance on network.Reliance on network. Security. Security.

Disadvantages of Networks to Disadvantages of Networks to BusinessBusiness

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OrganisationInformation

System

SystemUsersSite 1

SystemUsersSite 2

Organisation Boundary

LAN

Customer IS

Collaborator/Supplier IS

Online services

WAN and Internet

Role of Communications in Role of Communications in BusinessBusiness

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Company A

Company B

Supplier

1. Specify Product

3. Purchase Order

5. Payment (to bank)

2. Confirm Availability

4. Delivery and Invoice

Electronic Data InterchangeElectronic Data Interchange

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Computer NetworkComputer Network• Communication system Communication system • Links two or more computers and peripheral devices Links two or more computers and peripheral devices • Enables transfer of data between the components.Enables transfer of data between the components.

Types of Communication NetworksTypes of Communication Networks• Local area networks (LANS)Local area networks (LANS)• Wide area networks (WANS)Wide area networks (WANS)• Value added networksValue added networks• InternetInternet• Ad hoc networksAd hoc networks• Personal Area networksPersonal Area networks• ……

Computer NetworksComputer Networks

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Local Area Network (LAN)Local Area Network (LAN)

LAN

PC

PC

PC

Portable

Server (Network OS)

Printer

NetworkGateway

OtherNetwork

Mac

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Diverse Hardware & SoftwareDiverse Hardware & Software LAN is limited in extentLAN is limited in extent One or several segments connectedOne or several segments connected GatewayGateway

Local Area Network (LAN)Local Area Network (LAN)

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Peer-to-Peer NetworkingPeer-to-Peer Networking• Simple LANSimple LAN• Any PC on network can share files and Any PC on network can share files and

peripheralsperipherals• Small workgroupsSmall workgroups• Data will be distributedData will be distributed

Local Area Network (LAN)Local Area Network (LAN)

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Wide Area Network (WAN)Wide Area Network (WAN)

Wide Area NetworkWide Area Network• Span broad geographic distances;Span broad geographic distances;• Remote serversRemote servers• Global networkGlobal network• Enterprise-wide networkEnterprise-wide network• Best known example is the InternetBest known example is the Internet• CommunicationCommunication

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Value Added Networks (VANs)Value Added Networks (VANs)• Commercial network servicesCommercial network services• Cheaper than dedicated line WANSCheaper than dedicated line WANS• Less SecureLess Secure• Virtual Private Networks (VPNs)Virtual Private Networks (VPNs)

Value Added Network (VAN)Value Added Network (VAN)

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InternetInternet The largest computer network in the world.The largest computer network in the world.

Actually a network of networks – a collection of Actually a network of networks – a collection of more than 200,000 individual computer networks more than 200,000 individual computer networks owned by governments, universities, non-profit owned by governments, universities, non-profit groups, and companies.groups, and companies.

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InternetInternet These interconnected networks can communicate These interconnected networks can communicate

because they all use the same, non-proprietary because they all use the same, non-proprietary standards and protocols.standards and protocols.

They are connected via high-speed long-distance They are connected via high-speed long-distance backbone networks.backbone networks.

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Evolution of the InternetEvolution of the Internet Began as one network – ARPANET.Began as one network – ARPANET.

A 1969 US govt. experiment in packet-switched A 1969 US govt. experiment in packet-switched networking.networking.

ARPA – Department of Defence ARPA – Department of Defence AAdvanced dvanced RResearch esearch PProjects rojects AAgency.gency.

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Evolution of the InternetEvolution of the Internet Originally linked a largely technical audience Originally linked a largely technical audience

composed of the military, government agencies, composed of the military, government agencies, and academic researchers and scientists.and academic researchers and scientists.

Aim – to allow researchers to share computing Aim – to allow researchers to share computing resources and exchange information regardless of resources and exchange information regardless of their locations, and to create a resilient fault-their locations, and to create a resilient fault-tolerant, wide area network for military tolerant, wide area network for military communications.communications.

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Evolution of the InternetEvolution of the Internet ARPANET split into 2 networks in the early 1980s: ARPANET split into 2 networks in the early 1980s:

ARPANET and Milnet (an unclassified military ARPANET and Milnet (an unclassified military network), but connections allowed network), but connections allowed communication to continue.communication to continue.

Cooperative, decentralised networks such as Cooperative, decentralised networks such as UUCP (a worldwide UNIX communications UUCP (a worldwide UNIX communications network) and USENET (User’s Network) originated network) and USENET (User’s Network) originated in the late 70s.in the late 70s.

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Evolution of the InternetEvolution of the Internet These initially served the academic community These initially served the academic community

but later catered for commercial organisations.but later catered for commercial organisations.

In the early 80s more networks such as the In the early 80s more networks such as the Computer Science Network (CSNET) began to Computer Science Network (CSNET) began to provide networking to the academic and research provide networking to the academic and research communities.communities.

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Evolution of the InternetEvolution of the Internet These networks were not part of the Internet, but These networks were not part of the Internet, but

special connections were made to allow the special connections were made to allow the exchange of information between the networks.exchange of information between the networks.

The National Science Foundation Network The National Science Foundation Network (NSFNET) originated in 1986 and linked (NSFNET) originated in 1986 and linked researchers with five supercomputer centres.researchers with five supercomputer centres.

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Evolution of the InternetEvolution of the Internet The seamless internetworking of all these The seamless internetworking of all these

networks gave rise to the Internet we know networks gave rise to the Internet we know today.today.

Where Wizards Stay Up Late: The Origins of the Where Wizards Stay Up Late: The Origins of the InternetInternet by Katie Hafner, Matthew Lyonby Katie Hafner, Matthew LyonTouchstone Books; ISBN: 0684832674; Reprint Touchstone Books; ISBN: 0684832674; Reprint edition (January 1998) edition (January 1998)

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Internet InfrastructureInternet Infrastructure Although the Internet began as a government Although the Internet began as a government

project commercial communications companies project commercial communications companies now largely provide the physical network now largely provide the physical network backbone of the internet.backbone of the internet.

The Internet infrastructure is supplied by network The Internet infrastructure is supplied by network providers, such as UUNET, an MCI WorldCom providers, such as UUNET, an MCI WorldCom company, GTE Internetworking, Sprint and others.company, GTE Internetworking, Sprint and others.

Businesses and individual subscribers connect to Businesses and individual subscribers connect to the Internet through these and other, smaller the Internet through these and other, smaller Internet service providers.Internet service providers.

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Internet InfrastructureInternet Infrastructure

Both backbone and access providers are referred Both backbone and access providers are referred to as to as Internet Service Providers (ISPs).Internet Service Providers (ISPs).

These charge customers for various combinations These charge customers for various combinations of bandwidth, traffic, and access time.of bandwidth, traffic, and access time.

Backbone providers are connected to one another Backbone providers are connected to one another and to access providers over and to access providers over backbone backbone networksnetworks..

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Internet InfrastructureInternet Infrastructure The various backbone networks that make up the The various backbone networks that make up the

Internet transmit information to one another on a Internet transmit information to one another on a reciprocal basis – i.e. each carrier agrees to reciprocal basis – i.e. each carrier agrees to transport traffic originating on another carrier’s transport traffic originating on another carrier’s network.network.

Historically this has been done without charge – Historically this has been done without charge – although this is now changing due to growing although this is now changing due to growing demands.demands.

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The Operation of the InternetThe Operation of the Internet

Packet Switching: Packet Switching: Breaks up blocks of text Breaks up blocks of text into small, fixed bundles of data called packets.into small, fixed bundles of data called packets.

Each packet travels independently through the Each packet travels independently through the network.network.

Packets of data originating at one source can be Packets of data originating at one source can be routed through different paths in the network, routed through different paths in the network, and then reassembled into the original message and then reassembled into the original message when they reach their destination.when they reach their destination.

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Packet SwitchingPacket SwitchingMessage disassembled

PacketsTransmitted

Message re-assembled

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TCP/IP:TCP/IP: The set of rules used to send and The set of rules used to send and receive packets from one machine to another receive packets from one machine to another over the Internet.over the Internet.

TCP (Transmission Control Protocol)TCP (Transmission Control Protocol): : Converts messages to packets at source and Converts messages to packets at source and reassembles them at destination.reassembles them at destination.

IP: Internet Protocol: IP: Internet Protocol: Handles the addressing, Handles the addressing, ensures packets can be switched across ensures packets can be switched across multiple nodes.multiple nodes.

The Operation of the InternetThe Operation of the Internet

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Addresses on the InternetAddresses on the Internet Each computer on the Internet has an assigned Each computer on the Internet has an assigned

address know as address know as an an IP(Internet Protocol) IP(Internet Protocol) NumberNumber - a set of 4 numbers in the range 0 - - a set of 4 numbers in the range 0 - 255: xxx.xxx.xxx.xxx 255: xxx.xxx.xxx.xxx (e.g. 135.62.128.91)(e.g. 135.62.128.91)

Most computers also have names (easier to Most computers also have names (easier to remember). These are derived from the remember). These are derived from the domain domain name system (DNS).name system (DNS).

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Addresses on the InternetAddresses on the Internet DNS is a collection of servers on a TCP/IP network.DNS is a collection of servers on a TCP/IP network.

Resolves the text names used with the numbers Resolves the text names used with the numbers that computers use.that computers use.

Arranged as a hierarchical database, with Arranged as a hierarchical database, with authority for naming handed from root servers authority for naming handed from root servers responsible for top level domains down to lower responsible for top level domains down to lower sub-domains.sub-domains.

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Addresses on the InternetAddresses on the Internet All Internet destinations that can be found by All Internet destinations that can be found by

name require an entry on a DNS server.name require an entry on a DNS server.

This process is the foundation for message This process is the foundation for message delivery and navigation on the Internet.delivery and navigation on the Internet.

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The World Wide WebThe World Wide Web NotNot the same as the Internet. The Internet the same as the Internet. The Internet

functions as the transport mechanism, and the functions as the transport mechanism, and the World Wide Web (the Web, WWW, or W3) is an World Wide Web (the Web, WWW, or W3) is an application that uses those transport functions.application that uses those transport functions.

A system with universally accepted standards for A system with universally accepted standards for storing, retrieving, formatting, and displaying storing, retrieving, formatting, and displaying information via a client/server architecture.information via a client/server architecture.

Handles all types of digital information: text, Handles all types of digital information: text, graphics, sound, etc.graphics, sound, etc.

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The World Wide WebThe World Wide Web Uses a graphical user interface – v.easy to use.Uses a graphical user interface – v.easy to use.

Based on a standard hypertext language called Based on a standard hypertext language called Hypertext Markup Language (HTML)Hypertext Markup Language (HTML) which which formats documents and incorporates hypertext formats documents and incorporates hypertext links to other documents stored on the same or links to other documents stored on the same or different computers.different computers.

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The World Wide WebThe World Wide Web

Hypertext Transport Protocol (HTTP):Hypertext Transport Protocol (HTTP): the the communications standard used to transfer pages communications standard used to transfer pages across the WWW portion of the Internet.across the WWW portion of the Internet.

It defines how messages are formatted and It defines how messages are formatted and transmitted and what actions web servers and transmitted and what actions web servers and browsers should take in response to various browsers should take in response to various commands.commands.

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IntranetsIntranets Privately accessible network.Privately accessible network. Constructed using Internet technology and tools.Constructed using Internet technology and tools. Businesses are using intranets for the internal Businesses are using intranets for the internal

display of:display of:• Company manuals;Company manuals;• Internal news and information;Internal news and information;• Company catalogues;Company catalogues;• Project notice boards/bulletin boards.Project notice boards/bulletin boards.

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ExtranetsExtranets Access to Intranet extended outside organisation.Access to Intranet extended outside organisation. AccessAccess

• Leased line;Leased line;• VPN;VPN;• Internet.Internet.

Employee accessEmployee access Strategic partner accessStrategic partner access Support EDISupport EDI

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Ad Hoc NetworksAd Hoc Networks A collection of wireless mobile nodes that A collection of wireless mobile nodes that

dynamically form a temporary network on an as dynamically form a temporary network on an as needed basis without the use of any existing needed basis without the use of any existing network infrastructure.network infrastructure.

All nodes of the network act as routers and All nodes of the network act as routers and forward received packets to nodes within radio forward received packets to nodes within radio range.range.

The network can grow, reduce in size or fragment The network can grow, reduce in size or fragment in real time without referencing any central in real time without referencing any central authority.authority.

The nodes may be stationary or moving.The nodes may be stationary or moving.

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Personal Area NetworksPersonal Area Networks Used for communication among computer Used for communication among computer

devices (including telephones and personal digital devices (including telephones and personal digital assistants) close to one person. assistants) close to one person.

The reach of a PAN is typically a few metres. The reach of a PAN is typically a few metres.

PANs can be used for communication among the PANs can be used for communication among the personal devices themselves (intrapersonal personal devices themselves (intrapersonal communication), or for connecting to a higher communication), or for connecting to a higher level network and the Internet. level network and the Internet.

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Transmission MediaTransmission Media Medium over which signals are transmittedMedium over which signals are transmitted Guided mediaGuided media::

• Twisted Pair;Twisted Pair;• Co-axial;Co-axial;• Fibre-optic;Fibre-optic;

Unguided or wireless media:Unguided or wireless media:• Wireless infra-red transmission;Wireless infra-red transmission;• Wireless transmission;Wireless transmission;• Microwave transmission;Microwave transmission;• Satellite transmission.Satellite transmission.

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Transmission MediaTransmission Media Key characteristics of any medium are:Key characteristics of any medium are:

• Capacity in terms of volume and distance Capacity in terms of volume and distance carried;carried;

• Cost;Cost;• Robustness under different conditions.Robustness under different conditions.

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Characteristic Twisted Pair(Cat 5)

Co-axial Fibre-optic

Microwave Satellite

Maximum data transfer rate

100 Mbit/Sec

140 Mbit/Sec

10,000 Mbit/sec

100 Mbit/sec

100 Mbit/sec

Installation Easy Moderate Difficult Difficult Difficult

Cost Low Moderate High High High

Maintenance Moderate Low Low Low -

Characteristics of Different Characteristics of Different Transmission MediaTransmission Media

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SummarySummary We have covered the basics of data communication:We have covered the basics of data communication:

• Types of Networks;Types of Networks;• Local area networks;Local area networks;• Wide area networks;Wide area networks;• Looked at some of the technologies behind the Internet;Looked at some of the technologies behind the Internet;• Transmission Methods;Transmission Methods;• Transmission Media;Transmission Media;• Intranets and extranets.Intranets and extranets.

Data communications technology is becoming as Data communications technology is becoming as fundamental as to business today as computing already is.fundamental as to business today as computing already is.