Lec04-Introduction to Internet and Email.pdf

ICT101/141(LE04): Introduction to Internet & Email (Lec04) Department of Comp0uter Science B. Gopolang: 247-275 Lecture Outline  The internet  Its penetration  Its owner  Intranet vs extranet  Internet services...

ICT101/141(LE04): Introduction to Internet & Email (Lec04) Department of Comp0uter Science B. Gopolang: 247-275 Lecture Outline  The internet  Its penetration  Its owner  Intranet vs extranet  Internet services 2  1. The Internet  A global network connecting millions of computers.  A global system of interconnected computer networks that use the standard Internet Protocol suite (TCP/IP) to link several billion devices worldwide.  An international network of networks consisting of millions of private, public, academic, business, and government networks, linked by a broad array of electronic, wireless, and optical networking technologies.  AKA The Net, Info. Superhighway, Cyberspace. 3 Internet penetration 4  Who owns the Internet?  No one, and no single person or organization controls the Internet in its entirety  It is more of a concept than an actual tangible entity  It relies on a physical infrastructure that connect networks to other networks  History of the Internet begins with the development of electronic computers in the 1950s (wikipedia) 5  Intranet vs. Extranet  Intranet: Computer network that uses IP technology within an organization to share information, operational systems, or computing services  Extranet: Same as above except that it is a network between organizations. 6 2. Internet services  Lots of internet services  Common ones are ◦ World Wide Web (WWW) ◦ E-Mail ◦ Chatting ◦ Discussion Forums 7  3. World Wide Web (WWW)  Defn: ◦ An information-sharing model built on top of the Internet.  A system of interlinked hypertext documents that are accessed via the Internet  www ≠ internet 8  a) Web Browser  Commonly referred to as a Browser  A software application for retrieving, presenting and traversing information resources on the World Wide Web. (surfing)  Information resource on the WWW is identified by a Uniform Resource Locator (URL) ◦ E.g: web page, image, video or other piece of content. 9  Uses a client-server model ◦ Browser: client running on a computer that contacts the Web server and requests for information, ◦ Web server: sits somewhere on the internet  sends the requested information back to the Web browser which displays the results on the computer or another Internet-enabled device that supports a browser. 10  Some examples of web browsers Most common browsers  Most commonly used to access information on the web  BUT can also be used to access information hosted on Web servers in private networks such as intranets. 11 Web browser features  Retrieves information and displays it  Bookmarks/Favourites  History file  Start/home/default page  b) URL  URL: A global address of documents and otherWWW resources  Consist of 3 parts ◦ Network protocol (protocol identifier: protocol to use)  URL protocols include http://, ftp://, and mailto:// ◦ Host name or address (domain name: resource location) ◦ File or resource location (www resource)  3 parts are separated by special characters as follows:13  Examples  http://www.ietf.org/rfc/rfc2396.txt  ftp://www.somecompany.com/whitepapers/widgets.ps 14 Another example http:// www.cnn.com /a/first.htm Protocol Domain Pathname to Name file 15 c) Website  Collection of one or more web pages grouped under the same domain name. ◦ web site address. E.g. www.ub.bw  Accessed by entering a Uniform Resource Locator (URL) 16  UB website ◦ Home page  Other pages, ◦ e.g. Library webpage  d) Webpage  A document that is accessible through the Internet or other network using a browser.  Commonly written in HyperText Markup Language (HTML)  Could be static or dynamic 18 Static webpages  Delivered exactly as stored  Displays the same info for all users, at all times  Easily created ◦ no programming skills required  Cacheable  No need for web server .html files  E.g. a student’s personal profile page 19 Dynamic webpages  Prepared with fresh content or layout for each view  Changes with time, user, user interaction, context  Client-Side scripting ◦ e.g. JavaScript (presentation)  Server-Side scripting ◦ e.g. ASP (Active Server Pages), PHP (PHP HyperText Processor)  E.g. online store: different prices, reviews, user information 20 e) Useful concepts  Hypertext: text displayed on a monitor or with references (hyperlinks) to other text which the reader can immediately access  Hyperlink: a reference to data that the reader can directly follow either by clicking or by hovering mouse  Hypertext Markup Language (HTML): An authoring language used to create documents on the World Wide Web. 21  Hypertext Transfer Protocol (HTTP): An application protocol for distributed, collaborative, hypermedia information systems. ◦ The foundation of data communication for WWW.  File Transfer Protocol (FTP): A network protocol used to transfer computer files from one host to another host over a TCP-based network, such as the Internet. ◦ FTP is built on a client-server architecture 22 f) Search engines  Systems designed to search for information on theWWW  Many search engines out there … 23 Search engine market share –2020 Source: https://celadormedia.com/blog/google-vs-yahoo-vs-bing/ g) Search results 25 h) Internet Security Protocols  HTTPS: a web security policy mechanism whereby a web server declares that complying web browsers are to interact with it using only a secure connection  Secure socket layer (SSL): a standard security protocol for establishing an encrypted link between a server and a client. ◦ Sensitive data such as credit card numbers, social security numbers, and login credentials can be transmitted securely  Advanced Encryption Standard (AES): an encryption algorithm for securing sensitive data over the internet 26  Firewall: A system designed to prevent unauthorized access to or from a private network. ◦ Frequently used to prevent unauthorized Internet users from accessing private networks connected to the Internet e.g. intranets.  All messages entering or leaving the intranet pass through the firewall for examining  It blocks all messages that do not meet the specified network security criteria 27  i) Mobile browsers  AKA microbrowsers  Designed for web access through mobile devices  Mobile browsers are ◦ "stripped down" versions of everyday browsers ◦ Have fewer features to run well on mobile devices. ◦ Optimized to display web content on  smaller mobile device screens  with far less computing power  and memory compared to desktop or laptop. ◦ Egs: Chrome, Firefox, Opera Mini, Safari, Links. 28 Search Engine Tips  Questions you should ask when using a web page (especially for school work) ◦ Who is the author or sponsor? ◦ What authority/expertise do they have? ◦ What is the purpose/scope of the page? ◦ Is it current? When was it last updated? ◦ How complete and accurate is the information? (Any bias?) 29  You can search WWW using ◦ Exact words and phrases  How can you narrow your search? ◦ Use a set of words or symbols  E.g. put phrases in quotation marks  “University of Botswana”  Will include pages with the same words in the same order as the ones within the quotes ◦ Wildcards: Add an asterisk as a placeholder for any unknown characters or terms.  E.g.: train*  train, trains, trained, training, trainer, trainline, … 30  ◦ Use Search operators- words or symbols that can be added to searches to help narrow down the search  AND : for finding two words together. E.g. climate AND change  OR : climate change OR global warming will find pages that have either “climate change” or “global warming”  - sign: exclude words. e.g. University -Botswana  + sign: include words. e.g. broom + stick  See Blackboard links for more information on these  Also check http://www.techrepublic.com/blog/10- things/10-tips-for-smarter-more-efficient-internet- searching/ 31  4. Email services  Short form for electronic mail  Most commonly referred to as email or e-mail  First email sent in 1971 by Ray Tomlinson to himself ◦ Test messages were entirely forgettable....  Requires an account on a mail server and supporting software on you PC  Basic email Features ◦ Send, Compose, Reply and Forward 32  Places to get an email account  School/workplace (e.g. UB)  Internet Service Providers (e.g. Orange)  Free online email services, egs: 33  Basic email structure: composing an email  Addressing part ◦ To: email addresses of recipients ◦ Carbon Copy (CC): Email addresses to copy the message to.  Can see original recipients and are visible to intended recipients ◦ Blind Carbon Copy (BCC): Email addresses to send a blind copy of the email  Cannot see other recipients and are also not visible to intended recipients  Subject: Message title/headline 34  Main Body ◦ Message text  Signature ◦ Information about sender that is automatically added to outgoing message e.g. name and phone number  Attachments ◦ Files e.g. pictures, sounds, text files, etc. Email parts - Example 36  5. Chatting  Chat goes on in real-time  Content could be a combination of text, audio, video & images 37  6. Discussion Forum  Web-based collection of messages generated by people with common interests. 38