IT 210

The Internet & World Wide Web introduction

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.

What is the World Wide Web?

It is not the Internet.It is not any computer networkIt 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 browsersWWW documents are requested and sent using the HTTP protocol.

Network and the OSI Model

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

Your Key Challenge

The Protocols and Languages are constantly changing!

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

HTML

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

Viewing a Webpage

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

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., byu.edu)

A live connection to the Internet for your server

Accessing a Webpage

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

Simple Universal Resource Locator (URL) Example

Detailed URL Example

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., http://www.register.com/). ICANN is ultimately responsible.

What’s a resource?

HTML documentXML documentAnything 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.)

Domain Name Service (DNS)

Goal of DNS Server: “domain name resolution” – map a domain name (e.g., www.byu.edu) to an IP address (128.187.16.242)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.

DNS Server Network

How http works

Play demo

URL Reference Scenario

Browser

User computer

NetworkStack

WebServer

Server Computer

NetworkStack

Network

Cloud-

The Intern

et

DNSServer

Server Computer

NetworkStack

URL R

eque

st

Name

Reso

lutio

n

IP A

ddre

ss

TCP Open on port 80

TCP Session ACK HTTP file request

HTTP file data TCP Terminate Session

TCP Terminate ACK

File

Read

File

Data

WebServer

Server Computer

NetworkStack

URL Reference Scenario with Query

Browser

User computer

NetworkStack

Network

Cloud-

The Internet

DNSServer

Server Computer

NetworkStack

URL R

eque

st

Name

Reso

lutio

n

IP A

ddre

ss

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

Virtual Machines Setup for 210

` `

Ethernet

Browser

Client System Server System(Linux)

Apache

Tomcat

Browser

VMware Server(Windows XP)

IIS Browser

Lab server accounts:Remote Server Inside the lab address

192.168.201.XXX Outside the lab addresses

SSH access – it.et.byu.edu:51XXX HTML access – it.et.byu.edu:41XXX

Network Attached Storage (NAS) IP address is 192.168.0.83

Inside lab only You will use it to backup your data

More Details in Labs 1 & 2

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.

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.

Course: WEB SYSTEM Development

Overview of WEB Architectures and Design PrinciplesStudy of WEB SYSTEM Architectures to implement various WEB Architectures.Design and Implementation of WEB based systems.

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.