INTERNET AND THE WWW Learning Objectives At the end of this topic a student should be able to: • Explain Internet Technologies • Explain components of WWW • Explain and discuss WEB 2.0 • Discuss DNS Definitions: Network • Connection of two or more devices, to share resources or to send messages • Devices may include everyday things such as PCs, laptops, TV, Mobile (Think IoT), Servers, Printers, Routers etc. • Data is sent over communication media, such as wireless, cabled network Definitions: Internet • Interconnection of computers • Comes from the word INTERconnected NETworks • Interconnection of connected networks Definitions: WWW • Stands for World Wide Web • An information Sharing model built on top of the Internet • Uses HTTP protocol and browsers (give examples) to access content • Content is in form of web pages formatted in HTML and linked via hyperlinks Uses of the Internet • Email • WWW, hypertext, browsers • FTP, P2P file distribution • Mobile Internet • IM, Skype, Duo • Blogging, Microblogging • Learning – eg. Massively Open Online Courses (MOOCs) – Edx, Udemy… • Remote Backup – Cloud Computing • Software over the internet (cloud services eg Office 365), IaaS, PaaS • Streaming content – video and audio How to Access Webpages • In order to access webpages, we require special types of software • These software are called Browsers • A browser is an application that provides a way of looking at and interacting with the information on the world wide web • Browsers are used to retrieve, present and traverse information resources • These resources include web pages, images, video etc Web Browser vs Web Server • Web Browser requests and parses documents from web servers • • • • ¨Mozilla Firefox ¨Microsoft Internet Explorer (IE) ¨Apple Safari ¨Google Chrome • ¨… • Web Server listens for web page requests • ¨Apache • ¨Microsoft Internet Information Server • (IIS) • ¨… DNS • DNS Stands for Domain Name System/Server/Service • Every web server has a specific IP Address attached to it • IP is a logical address • However, given that the IP has four parts, it would be hard to remember all of them • Exercise: Can you identify which this address the IP belongs to? 198.57.179.99 DNS • Computers do not understand text, but understand binary • IP Address are binary in nature • We have two versions, IPv4 and IPv6 • How do computers understand the web address typed in by the user? DNS • IPv4 uses 32bits • IPv6 uses 128bits • The text typed in the browser needs to be translated to a format that the computer can understand • The text is converted by use of DNS DNS • Earlier example, the IP 198.57.179.99 can be found by typing in Strathmore.edu • DNS converts the name to the IP and seeks the resource based on the IP • Aids in memory of the various webpage • How would you remember Facebook, Twitter, Gmail, Reddit, Strathmore, Etc via IP? URL • Stands for Uniform Resource Locator • Used to address a document on the Web • The name used corresponds to an IP, and is listed on the DNS • Example is : http://www.mit.edu/sloan/index.html • Nowadays, https has been used in place of http, why? • URL follows the general syntax • the format is: scheme://host.domain.countrycode:port/path/file name Structure of a web address • Hosts and Domain Names: domain name as the name of the network you’re trying to connect to and think of the host as the computer you’re looking for on that network. • Path Name and File Name: the path maps to a folder location where the file is stored on the server; the file is the name of the file you’re looking for. THE INTERNET HISTORY Internet: Brief History • Began as a US Department of Defense network called ARPANET( Advanced Research Projects Agency Network) (1960s-70s) • Packet switching (in the 60s) • E-mail is born on 1971 • TCP/IP beginning on 1974 (Vinton Cerf). Various computer networks did not have a standard way to communicate with each other. A new communications protocol was established called Transfer Control Protocol/Internetwork Protocol . • By 1987: Internet includes nearly 30,000 hosts Brief History • WWW created in 1989-91 by Tim Berners-Lee • Popular web browsers released: – Netscape 1994 – IE 1995 • Amazon.com opens in 1995 • Google January 1996 • Wikipedia launched in 2001 • MySpace opens in 2003 • Facebook February 2004 Read more.. • https://www.freecodecamp.org/news/brie f-history-of-the-internet/ • https://webfoundation.org/about/vision/h istory-of-the-web/ Key Aspects of the internet • Computers can dynamically join and leave the network • Built on open standards • Lack of centralized control (mostly) • Everyone can use it with simple, commonly available software People and Organizations • Internet Engineering Task Force (IETF): internet protocol standards • Internet Corporation for Assigned Names and Numbers (ICANN): decides top-level domain names • World Wide Web Consortium (W3C): web standards Internet Protocols • A protocol is a set of rules governing the exchange or transmission of data between devices. • Computer communication protocol: is the detailed specification of how communication between two computers will be carried out in order to serve a specific purpose • Common Protocols are HTTP, FTP, SMTP Internet Protocols • E.g. https, or hypertext transfer protocol secure , is widely used to protect the transfer of sensitive information. • FTP , or file transfer protocol, is used for file transfer • The server that holds your e mail uses SMTP , or simple mail transfer protocol, to exchange mail with other e mail servers throughout the world. • Devices and computers connected to the Internet use a protocol suite called TCP/IP to communicate with each other. Functions of protocols Note: Not all protocols perform all functions This is because, we need to reduce the duplication of effort • Encapsulation – hiding information • Fragmentation and reassembly • Compressing data • Ordered Delivery • Flow Control – handling data to ensure that data transfer is efficient • Error Control TCP/IP Is a combination of two protocols; the IP (Internet Protocol) and the TCP (Transmission Control Protocol) TCP ensures that all the necessary packets are present, and puts them together in the correct order i.e. performs reassembly of the packets IP is used to move the chunks of data (packets) from one place to another. These places are specified by IP Addresses TCP/IP (transmission control protocol/Internet protocol). • The essential features of this protocol involve – identifying sending and receiving devices – breaking information into small parts, or packets, for transmission across the Internet. TCP/IP (transmission control protocol/Internet protocol). I. Identification: • Every computer on the Internet has a unique numeric address called an IP address (Internet protocol address). • Similar to the way a postal service uses addresses to deliver mail, the Internet uses IP addresses to deliver e-mail and to locate websites. • Because these numeric addresses are difficult for people to remember and use, a system was developed to automatically convert text-based addresses to numeric IP addresses. This system uses a domain name server (DNS) that converts text-based addresses to IP addresses. For example, whenever you enter a URL, say www.mhhe.com, a DNS converts this to an IP address before a connection can be made. Identification using Domain Name Server TCP/IP (transmission control protocol/Internet protocol). II. Packetization: • Information sent or transmitted across the Internet usually travels through numerous interconnected networks. Before the message is sent, it is reformatted or broken down into small parts called packets. • Each packet is then sent separately over the Internet, possibly traveling different routes to one common destination. • At the receiving end, the packets are reassembled into the correct order. Internet Protocol • Simple protocol for data exchange between computers IP Addresses: • 32-bit for IPv4 • 128-bit for IPv6 Protocol Interactions Web Application Protocol Interactions • HTTP defines the content and formatting of the requests and responses that are exchanged between the client and server. • TCP divides the HTTP messages into smaller pieces, called segments. These segments are sent between the web server and client processes running at the destination host Protocol Interactions • IP - is responsible for taking the formatted segments from TCP, encapsulating them into packets, assigning them the appropriate addresses, and delivering them to the destination host. • Ethernet - is a network access protocol that describes two primary functions: communication over a data link and the physical transmission of data on the network media. Network access protocols are responsible for taking the packets from IP and formatting them to be transmitted over the media. Hypertext Transport Protocol (HTTP) • Set of commands understood by a web server and sent from a browser • ¨ Some HTTP commands (your browser sends these internally): – GET filename: download – POST filename: send a web form response – PUT filename: upload Uniform Resource Locator (URL) • Example URL: – http://www.cs.toronto.edu/~mashiyat/csc309/index.htm • Upon entering this URL into the browser, it would: – Ask the DNS server for the IP address of the URL – Connect to that IP address at port 80 – Request the document from the server by sending – GET mashiyat/csc309/index.htm – Parse and display the resulting page on the screen HTTP Error Codes • When something goes wrong, the web server returns a special "error code" number • Common error codes: Enabling Web Technologies • Hypertext Markup Language (HTML) • Used for writing web pages • Cascading Style Sheets (CSS) • Stylistic info for web pages • JavaScript • Interactive web pages (on the client) • Server side Programming language • (Python, Nodejs,etc.) • Dynamic and data-driven pages (on the web server) Web 2.0 Introduction Web 1.0 • Initially the web consisted of static pages. • The visitors were limited to passive viewing and whose content only the site owners can modify • Web 1.0 was the first generation of the world wide web, also referred to as the read-only web. • Web 1.0 began as an information place for businesses to broadcast their information and only allowed users to search for information and read it. Web 2.0 • Web 2.0 is a term often applied to a perceived ongoing transition of the World Wide Web from a collection of websites to a full-fledged computing platform serving web applications to end users. • Web 2.0 describes the changing trends in the use of WWW technology and Web design that aim to enhance creativity, secure information sharing, increase collaboration, and improve the functionality of the Web as we know it (Web 1.0). • These have led to the development and evolution of Web-based communities and hosted services, such as social-networking sites (i.e. Facebook, MySpace), video sharing sites (i.e. YouTube), wikis, blogs, etc. Introduction • This shift can be characterized as the evolution of Web use from passive consumption of content to more active participation, creation and sharing • Web 2.0 Websites allow users to do more than just retrieve information. • Now users can build on the interactive facilities of Web 1.0 to provide "network as platform" computing, allowing users to run software-applications entirely through a browser • Users are able to co-author the data on a Web 2.0 site and exercise control over it. These sites have an "architecture of participation" that encourages users to add value to the application as they use it Features/ Techniques • Search: the ease of finding information through keyword searching • Links: guides to important pieces of information. The best pages are the most frequently linked to • Authoring: the ability to create constantly updating content that is co-created by users. In wikis, the content is iterative in the sense that the people undo and redo each other’s work. In blogs, it is cumulative in that posts and comments of individuals are accumulated over time • Tags: categorization of content by creating tags that are simple, one-word descriptions to facilitate searching and avoid having to fit into rigid, pre-made categories Web 3.0 • Web 3.0 or Web3 is the third generation of the World Wide Web. • Currently a work in progress, it is a vision of a decentralized and open Web with greater utility for its users. • Features: Artificial intelligence (AI) and machine learning, Decentralization, Trustless and permissionless etc. Reading and Discussion • What are your thoughts on Web 3.0? • Are we already in the era of Web 3.0? • What features/ Characteristics would Web 3.0 have? Thank you! Any Questions?
