Introduction to Internet PDF

21/01/2022 Topics Introduction to Internet  Define the internet and some standards related to it ...

21/01/2022 Topics Introduction to Internet  Define the internet and some standards related to it  Identify methods to connect to the Internet  Describe internet services  Describe the web and its terminologies Nilani De Silva  Searching Information Department of Computer Science Computer Network Main types of Network Basically there are two types of computer  A network is a collection of computers, Networks servers, mainframes, network devices,  LAN – Local Area Network peripherals, or other devices connected to allow sharing information and resources  WAN – Wide Area Network 1  21/01/2022 LAN WAN  A LAN is a group of computers connected  A Wide Area Network is a network that to each other in a small area such as extends over a large geographical area building, office, computer lab. such as states or countries.  It spans over a large geographical area through a telephone line, fiber optic cable or satellite links.  The internet is one of the biggest WAN in the world. What is the Internet?  The internet is a global system of interconnected networks that use the standard internet protocol suite (TCP/IP)  The system facilitate worldwide communication and access to data resources through a vast collection of private, public, business, academic and government networks 2  21/01/2022 How the internet works Internet Protocol  Protocol is a set of rules governing the exchange or transmission of data between devices  Important concepts of the Internet  TCP/IP is a family of protocols for communicating between computer devices  Internet Protocols  TCP/IP stands for Transmission Control Protocol /  Internet Addressing Internet Protocol  Client Server Architecture  It defines how electronic devices should be connected over the Internet, and how data should be transmitted between them Internet Addressing Internet Addressing  Each host is assigned at least one unique Internet address (IP address) on a TCP/IP network  IP v4 version - IP address is a 32-bit number  For easily maintain number is converted to decimal dotted notation (numbers separated by periods) 3  21/01/2022 Internet Addressing Ex: Ipconfig /all  IP V6 – 128 bit address Host Name  A unique identification that specifies a 192.348.48.3 - ip address of ruhuna main particular computer on the Internet web server For example alpha.ruh.ac.lk - ip name alpha.ruh.ac.lk matisse.csc.villanova.edu condor.develocorp.com 15-15 4  21/01/2022 Server Computer Ex  File server  Installed FTP server programs and configured  A Server (Server Computer) is a more powerful computing device that provides  Serves or delivers files to the client computer services  File server uses FTP/TFTP protocol  Servers normally have fast processing  Web server power, more memory, large storage  Installed web server programs and configured capacity..  Web pages are stored on web servers  Serves web pages to the requesting client  Web Server uses HTTP/HTTPS protocol 15-18 Client Computer Client Server Architecture  Client Computers (desktop, Laptop, Smart phone,  Computers on internet use client server architecture Tablet etc.) connected to the server computers  Client server architecture works when the client and request resources computer process request to the server over the  Need to install client programs for requesting network connection. resources  When the client computer sends a request to the Ex: for accessing web pages, need to install web server, server accepts the request and reply to the browser software (web client) client 5  21/01/2022 Domain Name System  The Domain Name System (DNS) is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet  DNS server stores a database which keep track of computer’s names and their corresponding IP Address 15-22 DNS Top Level Domain name for Universities ac.lk LEARN SubLevel Domain ruh.ac.lk Ruhuna University Sub level Domain sci.ruh.ac.lk Science Faculty 6  21/01/2022 Histrory of the Internet Histrory of the Internet  1969  1983 -TCP/IP established  The Internet was born in 1969  1984 – DNS established  It was first known as the ARPANet  1989 – Tim berners-lee developed WWW  1998 – Google arrived  1979  2003 – Skype released  Usenet ( a huge network of discussion groups ) Started  2004 – Facebook launched  2005 – Youtube launched DCS@RUH 25 DCS@RUH 26 Internet Usage Internet user distribution  As of January 2021 there were 4.66 billion active internet users worldwide  It is about 59.5 percent of the global population  Of this total, 92.6 percent (4.32 billion) accessed the internet via mobile devices. (source: https://www.statista.com/) 7  21/01/2022 Ways of Connecting to the ISP Internet  Internet Service Provider (ISP) is actually the Ex: company that provides Internet connections to the users.  Dial –Up Connections  The ISP provides the particular settings (wifi  Broadband Connections key,user name and password, ….)which needs to  Wireless Connections configure the Internet connection on your computer.  Ex: SLT Mobitel, Dialog,…….. Dial-up connection Dial -up  Allows connectivity to the internet through a standard telephone line  Like a phone call, a dial-up modem will connect you to the Internet by dialing a number, and it will disconnect when you are done surfing the Web.  Cannot use the land line and the internet at the same time  Slowest type of internet connection 8  21/01/2022 Dial-up Modem Broadband Connections  A device that converts digital computer  Broadband is the transmission of wide bandwidth data over a high speed internet connection information to analogue signals (Band width: maximum rate of data transfer across a given  Modems can be installed inside your path) computer (internal) or connected to your computer’s (external) serial port  It provides high speed internet access via multiple type of technologies:  Fiber optic  Cable Connection  DSL (Digital Subscriber Line)  Satellite DSL DSL  Connect to the Internet via a phone line  Unlike dial-up, it will always be on once it's set up  Able to use the Internet and your phone line simultaneously.  Much faster than dial-up 9  21/01/2022 Cable connection  Cable modem is a device that connect a computer system to the internet via the cable television network.  Provide by local cable TV provider  Internet connection speed varies with the number of users (subscribers) on the service at a specific point in time Fiber optic Connection  It transfers data via fiber optic cables  It is much faster and more reliable than cable internet or DSL 10  21/01/2022 Satellite  Satellite internet is a type of connection that uses a satellite to get an internet signal from your internet service provider (ISP) to you.  Satellite Internet is a form of high-speed Internet service  Connection may be affected by weather patterns ( rain or snow) Wireless Connection  A wireless Internet connection is a kind of connection that does not requires any wires for communication or transferring information or data  Use radio waves to connect devices 11  21/01/2022 University fiber backbone Network Layout-Lab  ISP is LEARN  Leased line , Wellamadama badwidth – 500Mbps Laboratory Classes Major Services  FTP Service  Electronic mail  World Wide Web  News groups  Internet Relay Chat  Etc …. 12  21/01/2022 File Transfer Protocol  File Transfer Protocol, is an Internet  Connect to ftp server utility software used to upload and  With user name and password download files.  Without user name and password (Anonymous)  It gives access to directories or folders on remote computers and allows software, data and text files to be transferred between different kinds of computers. File Transfer Protocol (FTP) FTP Server E-mail Your Computer DOWNLOAD  E-mail or Electronic mail is a paperless UPLOAD method of sending messages, notes or letters from one person to another or  Transferring files from an FTP site to the client is known even many people at the same time via as downloading. the Internet.  Transferring files from the client to an FTP site is known  E-mail is very fast compared to the as uploading. normal post  Clients may store files on an FTP site’s server. Slide 51 13  21/01/2022 Components of an E-mail Telnet (Remote Computing) Address  User id  Telnet (Remote Computing) Telnet or  Domain Name remote computing is telecommunication Ex: [email protected] utility software, which uses available telecommunication facility and allows you to become a user on a remote computer World Wide Web Internet Vs Web  Web is an information system on the  The Internet is the global system of Internet interconnected computer networks that uses the Internet protocol suite to communicate between  Information in web are interlinked by networks and devices hypertext links, and can be accessed via the internet  Web is an information system on the Internet  Web, is a collection of websites or web pages stored in web servers  The World Wide Web was invented by a British scientist, Tim Berners-Lee in 1989 14  21/01/2022 Web Server URL  URL: Uniform Resource Locator  Address of a resource on the Internet and a mechanism  A Web server is a system that delivers content or for retrieving it services to end users over the Internet.  A URL consists of a protocol, domain name, and path  A Web server consists of a physical server, server (which includes the specific subfolder structure where a operating system (OS) and software used to facilitate page is located) HTTP communication.  Basic format: protocol://domain-name.top-level- domain/path.  The main functionalities of web server software is accepting HTTP connections from web client and  The protocol indicates how a browser should retrieve delivering web pages information about a resource.  Web Server Software Apache HTTP Server Internet Information Services (IIS) Ex: Web Site  Ruhuna main web server https://www.ruh.ac.lk  Collection of web pages  Science faculty web server https://www.sci.ruh.ac.lk  Webpages contain text pages, digital images, audios, videos, etc.  FTP server ftp://192.248.48.82  A web page is a document commonly written in HTML  https://www.sci.ruh.ac.lk/botany/academic_staff.php (Hypertext Markup Language)  A home page is the first page that a Web site displays  A Web page has a unique address called a URL or Web address 15  21/01/2022 https://www.ruh.ac.lk https://www.sci.ruh.ac.lk How the web works Web Works  The web server sends out pages when they are requested by a web browser  The web server and Web Browser communicate using an agreed 'language' called HTTP (HyperText Transfer Protocol). 16  21/01/2022 Web Client History of Web Browser  A web client is a program capable of communicating with Web servers, requesting and receiving information from them, and processing it for display or other uses.  “WorldWideWeb” was the first web browser created by Tim Berners Lee in 1990.  A web browser is one kind of Web client.  In 1993, the “Mosaic” web browser was released.  Translates HTML pages and image data into a nicely formatted on-screen display.  In 1994, “Netscape Navigator” web browser released  Web Browser  In 1995, “Internet Explorer” was launched by Microsoft.  In 2002, “Mozilla Firefox” was introduced which was equally as competent as Internet Explorer  Apple too launched a web browser in the year 2003 and named it “Safari”.  In the year 2008, Google released “Chrome”  A "favorite" or "bookmark" is a function of a web browser that can be manually saved a website address Functions of Web Browser for future retrievals  Windows Internet Explorer is the only major Web browser that uses the term "favorites." A URL saved for  The main function is to retrieve information from the World Wide future browsing in Mozilla Firefox, Google Chrome and Web and making it available for users Apple Safari is called a "bookmark."  When a URL is entered in a browser, the web server takes us to that website  To run Java applets and flash content, plugins are available on the web browser  It makes Internet surfing easy as once we reach a website we can easily check the hyperlinks and get more and more useful data online  Browsers use internal cache which gets stored and the user can open the same webpage without losing extra data  Multiple webpages can be opened at the same time on a web browser  Options like back, forward, reload, stop, home, etc. are available on these web browsers, which make using them easy and convenient 17  21/01/2022 Finding information online Web Searching  A Web search engine is a specialized computer server that searches for information on the Web.  The most common way to find information online The search results of a user query are often is using a search engine returned as a list (sometimes called hits).  The hits may consist of web pages, images, and other types of files.  The results of a search engine are usually represented Web Searching in the form of URLs with an abstract.  Google is the most popular search engine  Ex:  Deliver the most relevant and reliable information  Google (https://www.google.com/)  URL: http://www.google.com  Microsoft Bing (https://www.bing.com/)  Ask.com (https://www.ask.com/) 18  21/01/2022 Search on Google Common search techniques  Tips  Exclude words from your search  Weather: Search weather to see the weather in your location or add a city name, like weather galle, to  Put - in front of a word you want to leave out. find weather for a certain place. example: vaccine –covid  Dictionary: Put define in front of any word to see its  Search for an exact match definition.  Put a word or phrase inside quotes.  Calculations: Enter a math equation like 3*9123, or solve using calculator. example: “covid vaccine”  Unit conversions: Enter any conversion, like 3  Combine searches dollars in rupees.  Put "OR" between each search query. Example: dengue OR malaria Search word/s Results Covid vaccine About 6,850,000,000 results (0.66 seconds) “Covid vaccine” About 185,000,000 results (0.70 seconds) vaccine About 4,130,000,000 results (0.59 seconds) Vaccine -covid About 3,360,000,000 results (0.51 seconds) dengue About 139,000,000 results (0.55 seconds) Dengue OR malaria About 450,000,000 results (0.91 seconds) 19