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									IT 210
The Internet & World Wide Web
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 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.
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
  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
 Markup language (NOT programming
 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.
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
 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.,
     A live connection to the Internet for your
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)
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., ICANN is
 ultimately responsible.
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.)
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
DNS Server Network
How http works

Play demo
URL Reference Scenario
                             Server Computer


                                                                File Data
                                 Server        Network   Server Computer

                                                                            File Read


 User computer
                              Cloud-                         Web
                         TCP Open on port 80                Server                      Network
                            HTTP file request                                            Stack
   Browser Network         InternetSession ACK
                           TCP Terminate Session
                                      HTTP file data
                                     TCP Terminate ACK
URL Reference Scenario with Query
                                 Server Computer


                                                                       File Data
                                     Server        Network   Server Computer

                                                                                   File Read
                                                               Web server calculates
                                                               and does actions,
                                   Network                     manufactures dynamic

  User computer                     Cloud-                       Web
                                                               HTML page

                            TCP Open on port 80                 Server                         Network
                                      The Session ACK
                          HTTP file request ? Other data                                        Stack
    Browser Network            TCP Terminate Session
                                      Dynamic HTML
                  Stack          InternetTerminate ACK
Virtual Machines Setup for 210
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
WEB Architecture:
  How one links together documents.
  How one presents document
  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
  How one allocates tasks between the
  browser, the web server, and other
  support servers to implement the
  network of services of the WEB
Course: WEB SYSTEM Development

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