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IT 210 The Internet & World Wide Web introduction.

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1 IT 210 The Internet & World Wide Web introduction

2 What is the Internet? The Internet is a network of networks, that is an Inter-Network, that connects different networks from all over the world that use the same communication protocols (e.g., IP/TCP). The Internet is spelled with uppercase “I”. There’s only one! It is the infrastructure upon which the World Wide Web (and other things like e-mail) resides.


4 What is the World Wide Web? It is not the Internet. It is not any computer network It is a set of documents and other resources (e.g., images) linked together by hyperlinks, made available by web servers, and “read” by client web browsers WWW documents are requested and sent using the HTTP protocol.


6 Network and the OSI Model

7 Key Internet/Web Challenge Problem: How can we get so many different devices to interact well together on the Internet? How can we request so many different types of content on the Web? Answer: Get hardware/software creators to use standard protocols & languages E.g., IP/TCP for Internet communication E.g., HTTP for Web communication E.g., HTML, CSS, Javascript, PHP for web content

8 Your Key Challenge The Protocols and Languages are constantly changing!

9 A day in the life of a webpage BIRTH: A website is born when a creator opens a text editor and adds some content using HTML (or other web standard-based language) Let’s give it a try… Open a text editor & create main.html

10 HTML Markup language (NOT programming language) Defines structure and content HTML 4, XHTML 1 & 2, HTML 5 (different related standards). Know your audience and what browsers they’re using and use appropriate one.

11 Viewing a Webpage Browsers are applications designed to render HTML and other web content Browsers do many other things such as cache data locally, run Javascript code in webpages, help avert malicious code… (See 20thingsilearned) 20thingsilearned Browsers render differently & have different features and bugs!

12 Posting to the Web You’ll need… A Web Server (software that accepts HTTP requests from browsers and “serves up” the requested files stored on the server) A registered domain name and its associated IP address (e.g., A live connection to the Internet for your server


14 Accessing a Webpage Use your browser to specify a web resource’s URL Your Browser contacts a DNS Server to translate the domain name of the URL into an IP address of the Web Server The IP address is used to route messages from the browser (on the client) to the Web Server by using the IP protocol Your browser will use the TCP & HTTP protocols to request and send the resource from the server (assuming it has it)

15 Simple Universal Resource Locator (URL) Example

16 Detailed URL Example

17 More on URLs Other Protocols: HTTPS: secure HTTP FTP:File Transfer Protocol Also: Gopher:, mailto:, telnet:, news: etc. Many companies allow you to register domain names (e.g., ICANN is ultimately responsible.

18 What’s a resource? HTML document XML document Anything a server can present as either of the above. Anything a browser can present using the services of the client (MS Word doc, PDF doc, etc.)

19 Domain Name Service (DNS) Goal of DNS Server: “domain name resolution” – map a domain name (e.g., to an IP address ( No single DNS Server includes all of the billions of IP addresses. Instead, they store what they need (and cache recently used pairs for a limited time – TimeToLive) and request from other DNS servers what they need.

20 DNS Server Network

21 How http works Play demo

22 URL Reference Scenario Browser User computer Network Stack Web Server Server Computer Network Stack Network Cloud- The Internet DNS Server Server Computer Network Stack URL Request Name Resolution IP Address TCP Open on port 80 TCP Session ACK HTTP file request HTTP file data TCP Terminate Session TCP Terminate ACK File Read File Data

23 Web Server Server Computer Network Stack URL Reference Scenario with Query Browser User computer Network Stack Network Cloud- The Internet DNS Server Server Computer Network Stack URL Request Name Resolution IP Address TCP Open on port 80 TCP Session ACK HTTP file request ? Other data Dynamic HTML TCP Terminate Session TCP Terminate ACK Web server calculates and does actions, manufactures dynamic HTML page File Read File Data

24 Virtual Machines Setup for 210

25 Lab server accounts: Remote Server Inside the lab address 192.168.201.XXX Outside the lab addresses  SSH access –  HTML access – Network Attached Storage (NAS) IP address is  Inside lab only You will use it to backup your data More Details in Labs 1 & 2

26 WEB Architecture: How one links together documents. How one presents document relationships. How one interfaces to dynamic content. How one keeps context in the network of documents.

27 WEB SYSTEM Architecture How one organizes the network of services to present the WEB architecture. How one allocates tasks between the browser, the web server, and other support servers to implement the network of services of the WEB Architecture.

28 Course: WEB SYSTEM Development Overview of WEB Architectures and Design Principles Study of WEB SYSTEM Architectures to implement various WEB Architectures. Design and Implementation of WEB based systems.

29 Questions: What is a protocol and why is it important to web systems? How are the Internet and WWW different? How are they related? Describe the process through which a website is accessed. What are HTTP, DNS servers, IP/TCP, IP addresses, URLs? Name the parts of a URL.

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