The document provides an introduction to how the web works, including a brief history of the internet and protocols like IP and TCP. It describes the client-server model with browsers as clients and web servers as servers. It discusses how host name resolution works, with computers querying root servers and top-level domain servers to find the IP address for a given domain name. The document then introduces some common web technologies like HTML, CSS, JavaScript, PHP and others. It provides an overview of HTML fundamentals including tags, attributes, elements and comments.

1. Web Training
Jayant Mukherjee
February 13, 2013 1

2. Part01: Introduction
How web works…
Part 01 - Introduction February 13, 2013 2

3. Part01 : Topics
• Brief History of Internet
o Evolution of Internet
o Internet Protocol
• Client-Server Architecture
o Client: Browser (Request)
o Server: Web Server (Response)
• Communication
o Background
• URL parsing
o Protocols
• Host Resolution
Part 01 - Introduction February 13, 2013 3

4. Part01 : Brief History of Internet
• Evolution of Internet!
o In 1969, Project Arpanet funded by
U.S. Military, initiated by DARPA in
1962.
o Renaming of Arpanet happened.
Arpanet  MILNET  Internet
o LAN  WAN  Internet
o Growth of Internet Hosts & Users were
exponential… and soon became
global phenomena…
Part 01 - Introduction February 13, 2013 4

5. Part01 : Brief History of Internet
• Protocol for Internet
o Internet Protocol (IP) is the method or
protocol by which data is sent from
one computer to another on the
Internet.
o Data is sent in chunks (packets)
consisting of source & destination IP
address and travels as relay.
o Internet Protocol delivers the packets.
Transmission Control Protocol puts
them back in right order
o Identification via Internet protocol
address IPv4/IPv6
• IPv4:n.n.n.n [232 addresses]
where n is 0-255
(4 bytes)
• IPv6:x.x.x.x.x.x [2128 addresses]
where x is 0000-FFFF
(16 bytes)
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6. Part01 : Client-Server Architecture
• Client (Browser)
o Client can be any application running locally on user‟s workstation which
can make connection and send web request to server.
o Browsers : IE, Firefox, Chrome
• Server (Webserver)
o Server or Webserver application is an application which listens to the
request and sends response to the request.
o Webservers : Apache, IIS
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7. Part01 : Communication
• Background
o URL (FQDN)
• URL Format: protocol://address:port/path/(page)
• Address Format: www.domainname.[tld/cctld]
o Protocols
• http, https, ftp, gopher, telnet, irc…
Part 01 - Introduction February 13, 2013 7

8. Part01 : Host Resolution
Part 01 - Introduction February 13, 2013 8

9. Part01 : Host Resolution
• e.g. Customer need to connect to (FQDN)
www.mybank.com
• IP address of the host is controlled by the company
MyBank and is stored within a DNS server under that
organisations control
• Customer‟s web browser software must first discover the
IP address to connect to www.mybank.com
• Customer‟s computer doesn‟t know the IP address of the
DNS server & to find it out it needs to query other servers
Part 01 - Introduction February 13, 2013 9

10. Part01 : Host Resolution
• Computer uses DNS resolver to connect to a known
root server and obtain TLD(„.com‟) Server‟s address.
• DNS resolver then queries TLD Server for authoritative
(„.mybank.com‟) DNS Server‟s address.
• Finally, DNS resolver queries the organisations
authoritative DNS server for the IP address of the
„www‟ host.
• Client uses this resolved IP address to fetch data
from host.
Part 01 - Introduction February 13, 2013 10

11. Part01 : Host Resolution
• Root Servers
o There are 13 number of strategically placed Root Servers underpinning the
entire Internet – referenced by 13 distinct names – each is assigned a letter
ranging from A to M, with the full name containing ROOT-SERVERS.NET.
o DNS resolvers use hard-coded IP lookup tables for these servers.
o Only 13 root servers are typically referenced, due to data limitations
requiring all root server names to fit within a single UDP packet given the
current naming scheme.
Part 01 - Introduction February 13, 2013 11

12. Part01 : Host Resolution
• Top Level Domain Servers
o Top Level Domain server‟s role is to point DNS resolvers to an Authoritative
Domain server.
o TLD layer is divided into two distinct classes – Generic TLDs (gTLD) and
Country-code TLDs (ccTLD) – with the ccTLD‟s also having a range of
subdomain servers.
o Until mid-2000, the root servers also handled all requests for the gTLDs. This
responsibility was later removed from the root servers and led to the
creation of dedicated TLD servers.
o gTLD‟s provide resolver information for the common
.com, .net, .org, .gov, .mil and .gov domain groupings.
o ccTLD‟s provide resolver information for country specific domain groupings
– such as .uk, .be, .in, .nl, etc.
Part 01 - Introduction February 13, 2013 12

13. Part01 : Host Resolution
• Authoritative Domain Servers (or Name Servers)
o Name Servers manage a Zone and either provide IP address lookup
information themselves, or delegate the lookup of zone/sub-zone
information to other DNS name servers.
o DNS define two classes of name servers:
• Primary Master name server maintains a zone file, stored locally on the
host.
• Secondary Master name servers get their zone info from an authoritative
name server for that zone via a process called “zone transfer”.
o Use whois lookup to get information.
Part 01 - Introduction February 13, 2013 13

14. Part01 : Host Resolution
• DNS Servers
o The DNS server (a generic term for Name Server) for a particular
domain provides forward and reverse resolution services between a
specific host name and its IP address.
o e.g., the DNS server for MyBank Limited may contain entries such as:
• The IP address of “www” is 100.1.2.10 (www.mybank.com)
• The IP address of “ftp” is 100.1.2.11 (ftp.mybank.com)
• The IP address of “mail” is 100.1.2.14 (mail.mybank.com)
• The IP address of “testserver” is 100.1.10.12
(testserver.mybank.com)
• WWW (World Wide Web)
o Its a system of interlinked hypertext documents and other
resources, linked by hyperlinks and URLs, accessed via the
Internet, developed by Sir Timothy John "Tim" Berners-Lee.
o www is one of the services that runs on the Internet.
o Try checking by nslookup.
• nslookup www.domain.com
• nslookup domain.com
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15. Part01 : Host Resolution
• Process of Resolution
Part 01 - Introduction February 13, 2013 15

16. Part01 : Host Resolution
• Resolution of MyBank DNS server from two physical locations
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17. Part01 : Host Resolution
• Multiple corporate DNS servers with internationally
distributed host servers
o e.g. MyBank Limited which has registered three domains
(mybank.com, mybank.co.uk, and mybank.com.au) and manages three
DNS servers strategically placed to handle customer host lookups in their
three key geographic business regions (Europe, Americas, and the Pacific)
Part 01 - Introduction February 13, 2013 17

18. Part01 : Host Resolution
Part 01 - Introduction February 13, 2013 18

19. Part02: Technologies
Introduction of Web Technologies…
Part 02 - Technologies February 13, 2013 19

20. Part02 : Topics
• HTML
• CSS
• Scripting Language
o Client side
• JavaScript
• VBScript
o Server side
• CGI/Perl
• PHP
• ASP
• Python
• Ruby
• CFML
• Java / ASP.Net
Part 02 - Technologies February 13, 2013 20

21. Part02 : <HTML>
• Introduction
• Fundamentals
o Meta Data
• Document type
• Language type
• Content type
o Tags, Attributes, Elements
o Comments
• Structure
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22. Part02 : <HTML> Introduction
• HTML - HyperText Markup Language.
• The first publicly available description of HTML was a
document called HTML Tags, first mentioned on the
Internet by Berners-Lee in late 1991.
• HTML is a markup language that web browsers use
to interpret and compose text, images and other
material into visual or audible web pages.
HTML version Time line
HTML 2.0 November, 1995
HTML 3.2 January, 1997
HTML 4.0 December, 1997
HTML 4.01 December, 1999
HTML 4.01 Strict May, 2000
HTML 5.0 January, 2008
Part 02 - Technologies February 13, 2013 22

23. Part02 : <HTML> Fundamentals
• DOCTYPE
o Validity of HTML is defined by DOCTYPE.
o <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
highlighted portion describes the document behavior.
• Language Type
o Primary language of a document can be set through HTTP header or with
the xml:lang attribute inside the opening html tag. The value is an
abbreviation, such as 'en' (English), 'fr' (French), 'de' (German) or 'mg'
(Malagasy).
o <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">.
• Content Type
o The media type and character set of an HTML document also needs to be
specified via header or meta tag.
o Content-Type: text/html; charset=UTF-8
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />.
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24. Part02 : <HTML> Fundamentals
• Tags
o <tag>…</tag>.
o In general a start tag will have closing tag. e.g. <table>…</table>.
• Attribute
o <tag attrib="prop_value">…</tag>.
o Attributes are properties for a specific tag.
e.g. <table border="1">…</table>.
• Elements
o <tag attrib="prop_value">content</tag>.
o Element consists of full tag with content. e.g.
<table border="1">
<tr>
<th>Month</th>
<th>Savings</th>
</tr>
<tr>
<td>January</td>
<td>$100</td>
</tr>
</table>.
• Comments
o <!-- block comments -->.
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25. Part02 : <HTML> Structure
• Doc declaration
<!DOCTYPE html>
<html>
• HTML block <head>
o Head <title>Shiny Gongs</title>
• Meta </head>
• Title
<body>
o Body
<h1>My First Heading</h1>
• Display elements
o Rich text <p>My first paragraph.</p>
o Table </body>
o Layers </html>
o Forms
o Applets
o Flash
o Animation
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