THE INTERNET, INTRANETS, AND EXTRANETS

An Overview of Telecommunications and Networks Telecommunications: the electronic

transmission of signals for communications

Telecommunications medium: anything that carries an electronic signal and interfaces between a sending device and a receiving device

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An Overview of Telecommunications and Networks (continued)

Elements of a Telecommunications System

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Transmission Media

Transmission Media Types

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Transmission Media (continued)

Transmission Media Types (continued)

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Telecommunications Devices

Common Telecommunications Devices

Networks Computer network: the

communications media, devices, and software needed to connect two or more computer systems or devices

Network nodes: the computers and devices on the networks

Basic Processing Strategies Centralized processing: all processing

occurs in a single location or facility Decentralized processing: processing

devices are placed at various remote locations

Distributed processing: computers are placed at remote locations but connected to each other via a network

Terminal-to-Host, File Server, and Client/Server Systems Connecting computers in distributed

information processing: Terminal-to-host: the application and database

reside on one host computer, and the user interacts with the application and data using a “dumb” terminal

File server: the application and database reside on the one host computer, called the file server

Client/server: multiple computer platforms are dedicated to special functions, such as database management, printing, communications, and program execution

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Terminal-to-Host, File Server, and Client/Server Systems (continued)

Client/Server Connection

Network Types Personal area network (PAN) Local area network (LAN) Metropolitan area network (MAN) Wide area network (WAN) International network

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Network Types (continued)

A Typical LAN

Network Types (continued)

A Wide Area Network

Communications Software and Protocols Communications software: software

that provides a number of important functions in a network, such as error checking and data security

Network operating system (NOS) Network management software Communications protocol: a standard

set of rules that controls a telecommunications connection

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Communications Software and Protocols (continued)

Common Communications Protocols

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Communications Software and Protocols (continued)

Common Communications Protocols (continued)

Use and Functioning of the Internet Internet: a collection of interconnected

networks, all freely exchanging information ARPANET

The ancestor of the Internet A project started by the U.S. Department of

Defense (DoD) in 1969 Internet Protocol (IP): communication

standard that enables traffic to be routed from one network to another as needed

How the Internet Works The Internet transmits data from one

computer (called a host) to another If the receiving computer is on a network to

which the first computer is directly connected, it can send the message directly

If the receiving computer is not on a network to which the sending computer is connected, the sending computer relays the message to another computer that can forward it

The Internet The internet

A network of networks The internet transmits data from one

computer (called a host) to another Internet networks

Linked networks that work much the same way -- they pass data around in packets, each of which carries the addresses of its sender and receiver

Internet

Unlike online services, which are centrally controlled, the Internet is decentralized by design. Each Internet computer, called a host, is independent. Its operators can choose which Internet services to use and which local services to make available to the global

Internet community. Remarkably, this anarchy by design works exceedingly

There are a variety of ways to access the Internet. It is also possible to

gain access through a commercial Internet Service Provider (ISP).

How the Internet WorksTransport control protocol (TCP)

A protocol that operates at the transport layer and is used in combination with IP by most Internet applications

Backbone An Internet high-speed, long distance

communications links (like a bus; wire that connects nodes)

Uniform resource locator (URL) An assigned address on the Internet for each

computer E.g., http://www.yorku.ca/

Domain AffiliationsDomain

Affiliations

arts cultural and entertainment activitiescom business organizationsedu educational sitesfirm businesses and firmsgov government sitesinfo information service providersmil military sitesnom individuals net networking organizationsorg organizationsrec recreational activitiesstore businesses offering goods for purchaseweb entities related to World Wide Web

activitiesnet networking organizations

Access to the Internet LAN servers

Local servers can provide access to the Internet through normal connections (e.g., Ethernet)

Serial line internet protocol (SLIP) and Point-to-point protocol (PPP)

Communications protocol software that transmits packets over telephone lines, allowing dial-up access to the Internet

Connection via an on-line service Examples are America Online and Microsoft Network.

These services usually require sign-up procedures

Three Ways to Access the Internet

Internet Service Providers Internet service provider (ISP)

Any company that provides individuals or companies with access to the Internet

Thousands of providers including large communications companies

Need an account with the ISP and software that links with TCP/IP

Internet Services E-mail Telnet FTP Usenet and newsgroups Chat rooms Internet phone Internet videoconferencing Content streaming

Internet Services Internet telephony

Also called voice-over-IP (VOIP) Technology that enables network managers to

route phone calls and fax transmissions over the same network they use for data

What is VOIP ?Internet telephony is a category of hardware and software that enables people to use the Internet as the transmission medium for telephone calls. For users who have free, or fixed-price, Internet access, Internet telephony software essentially provides free telephone calls anywhere in the world. To date, however, Internet telephony does not offer the same quality of telephone service as direct telephone connections.

There are many Internet telephony applications available. Some, like CoolTalk and NetMeeting, come bundled with popular Web browsers. Others are stand-alone products. Internet telephony products are sometimes called IP telephony, Voice over the Internet (VOI) or Voice over IP (VOIP) products.

Content Streaming Content streaming

A method for transferring multimedia files over the Internet so that the data stream of voice and pictures plays continuously, without a break, or very few of them

It also enables users to browse large files in real time

The World Wide Web World Wide Web

A collection of tens of thousands of independently-owned computers that work together as one in an Internet service

WWW Terminology Home page

The cover page for a Web site that has graphics, titles, coloured text, etc.

Hypermedia Tools that connect the data on Web pages,

allowing users to access topics in whatever order they wish

Hypertext markup language (HTML) The standard page description language for

Web pages

WWW Terminology Web browser

Software that creates a unique hypermedia-based menu on your computer screen and provides a graphical interface to the Web

Web page A screen of information sent to a requesting

user and presented through a browser Applet

A small program embedded in Web pages

HTML “The” language of WWW pages

Need we say more!!!

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The World Wide Web The Web, WWW or W3 A menu-based system that uses the

client/server model Organizes Internet resources throughout

the world into a series of menu pages, or screens, that appear on your computer

Hypermedia: tools that connect the data on Web pages, allowing users to access topics in whatever order they want

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The World Wide Web Hypertext Markup Language

(HTML): the standard page description language for Web pages

HTML tags: codes that let the browser know how to format the text on a Web page and whether images, sound, and other elements should be inserted

Search Engines Search engines

A search tool for the Web (like card catalogs in libraries)

E.g., Google.comYahoo.comRediff.com

Java Java

An object-oriented programming language Developed by Sun Microsystems Based on C++ Allows small programs -- applets -- to be

embedded within an HTML document

Applets Applets are small java programs that are

downloaded from the server to the local machine

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Developing Web Content

Products that greatly simplify the creation of a Web page For example: .NET platform

Content management system (CMS) Web services

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Web Services Standards and tools that streamline and

simplify communication among Web sites for business and personal purposes

Can also be used to develop new systems to send and receive secure messages between healthcare facilities, doctors, and patients, while maintaining patient privacy

Push Technology Push technology

Technology that enables users to automatically receive information over the Internet rather than searching for it using a browser

Also called Webcasting E.g.,

PointCast InterMind

Webcasting ‘Discussion’

Using the Internet, and the World Wide Web in particular, to

broadcast information. Unlike typical surfing, which relies on a pull

method of transferring Web pages, webcasting uses push

technologies.

What is Push ?

In client/server applications, to send data to a client without the client requesting it. The World Wide Web is based on a pull technology where the client browser must request a Web page before it is sent. Broadcast media, on the other hand, are push technologies because they send information out regardless of whether anyone is tuned in.

Increasingly, companies are using the Internet to deliver information push-style. One of the most successful examples of this is PointCast, which delivers customized news to users' desktops.

Push Mail

Probably the oldest and most widely used push technology is e-mail.

This is a push technology because you receive mail whether you ask

for it or not -- that is, the sender pushes the message to the

receiver.

Intranets and Extranets Intranet

An internal corporate network built using Internet and World Wide Web standards and products that allows employees of an organization to gain access to corporate information

Extranet A network based on Web technologies that

links selected resources of the intranet of a company with its customers, suppliers, or other business partners

What is Intranet ?

A network based on TCP/IP protocols (an internet) belonging to an organization, usually a corporation, accessible only by the organization's members, employees, or others with authorization. An intranet's Web sites look and act just like any other Web sites, but the firewall surrounding an intranet fends off unauthorized access.

Like the Internet itself, intranets are used to share information. Secure intranets are now the fastest-growing segment of the Internet because they are much less expensive to build and manage than private networks based on proprietary protocols.

What is Extranet ?

A new buzzword that refers to an intranet that is partially accessible to authorized outsiders. Whereas an intranet resides behind a firewall and is accessible only to people who are members of the same company or organization, an extranet provides various levels of accessibility to outsiders. You can access an extranet only if you have a valid username and password, and your identity determines which parts of the extranet you can view.

Extranets are becoming a very popular means for business partners to exchange information.

Virtual Private Network (VPN) Virtual Private Network (VPN)

A secure connection between two points across the Internet

Tunneling The process by which VPNs transfer information

by encapsulating traffic in IP packets and sending the packets over the Internet

VPN

Short for virtual private network, a network that is constructed by using public wires to connect nodes. For example, there are a number of systems that enable you to create networks using the Internet as the medium for transporting data. These systems use encryption and other security mechanisms to ensure that only authorized users can access the network and that the data

cannot be intercepted.

Tunneling

A technology that enables one network to send its data via another network's connections. Tunneling works by encapsulating a network protocol within packets carried by the second network. For example, Microsoft's PPTP technology enables organizations to use the Internet to transmit data across a virtual private network (VPN). It does this by embedding its own network protocol within the TCP/IP packets carried by the Internet. (Note: PPTP = point-to-point

tunneling protocol)

Tunneling is also called encapsulation.

Internet Issues Management issues

No centralized governing body for the Internet

Service bottlenecks Phenomenal growth has left a service void Providers underestimating computing

power needed Reconciling router addresses needed to

transverse the network

Privacy & Security Cryptography

The process of converting a message into a secret code and changing the encoded message back to regular text

Encryption The original conversion of a message into a secret

code Digital Signature

An encryption technique used for online financial transactions

Have anice day…

Have anice day…

Encryption software running on sending computer

Decryption software running on Receiving computer

E%$&:”}{|…

Firewalls Firewalls

A method of preventing unauthorized access between a company’s computers and the Internet (looks at the header of a packet)

Assured pipeline An Internet security method that looks at the

entire request for data and then determines whether the request is valid

Firewall

A system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware

and software, or a combination of both. Firewalls are frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

Firewall

There are several types of firewall techniques: Packet filter: Looks at each packet entering or leaving the network

and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.

Application gateway: Applies security mechanisms to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.

Circuit-level gateway: Applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.

Proxy server: Intercepts all messages entering and leaving the network. The proxy server effectively hides the true network addresses.

Firewall

In practice, many firewalls use two or more of these techniques in

concert.

A firewall is considered a first line of defense in protecting private

information. For greater security, data can be encrypted.

Summary Telecommunications is the electronic

transmission of signals for communications A computer network consists of the

communications media, devices, and software needed to connect two or more computer systems or devices

Ways of connecting computers in distributed information processing: terminal-to-host, file server, and client/server

Summary (continued) Network types: personal area network

(PAN), local area network (LAN), metropolitan area network (MAN), wide area network (WAN), and international network

The Internet is a collection of interconnected networks, all freely exchanging information

Internet Protocol (IP) is a communication standard that enables traffic to be routed from one network to another as needed

Summary (continued) Uniform Resource Locator (URL) is an

assigned address on the Internet for each computer

An intranet is an internal corporate network built using Internet and World Wide Web standards and protocols

An extranet is a network based on Web technologies that links selected resources of a company’s intranet with its customers, suppliers, or other business partners