IT 210 The Internet & World Wide Web introduction.
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Transcript of IT 210 The Internet & World Wide Web introduction.
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.