Internet Basics

Books

• TEXT BOOKS:• Web Enabled Commercial Application Development

Using HTML, DHTML, JavaScript, By: Bayros BPB publications

• OTHER READINGS:• Teach Yourself HTML 4 With XML, DHTML and Java

Script - Stephine Cottrell Bryant• H.Deitel, P.Deitel, A.Goldberg, Internet and World

Wide Web, How to Program.III Edition, Pearson Education, Inc, 2004.

• HTML Black Book: Galgotia Publications • Teach Yourself ASP in 21 Days: Sams publishing

Definition

• The Internet is a worldwide network of networks. It can be defined as a global network of over million of smaller heterogeneous computer networks.

• The internet is the common language whereby dissimilar computers with various operating systems, are able to communicate with each other, using a standard set of protocols.

• A protocol is a set of rules, which the computers use to communicate with each other across network.

History

1. First generation:a. Limited to government , research and

educational institutes.

b. 30 years back, network ARPANET established in 1969 which connect major computers of University of California.

c. 1957- Advanced Research Project Agency(ARPA)

d. E-mail

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2. Second generation:

a.) early 90’s with www

b.) email , newsgroup

c.) Tim Berners-Lee and others developed www in 1991

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3. Present generation

a.) news reporting, multimedia content

b.) e-commerce

Internet Addresses• Every machine on the Internet has a unique

identifying number, called an IP Address. • Internet addresses are in the form

nnn.nnn.nnn.nnn where nnn must be a number from 0 - 255. This address is known as an IP address.

• The four numbers in an IP address are called octets

• the IP address 0.0.0.0 is reserved for the default network and the address 255.255.255.255 is used for broadcasts.

• The octets serve a purpose other than simply separating the numbers. They are used to create classes of IP addresses that can be assigned to a particular business, government or other entity based on size and need. The octets are split into two sections: Net and Host. The Net section always contains the first octet. It is used to identify the network that a computer belongs to. Host (sometimes referred to as Node) identifies the actual computer on the network. The Host section always contains the last octet. There are five IP classes plus certain special addresses.

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• Default Network - The IP address of 0.0.0.0 is used for the default network.

• Loopback - The IP address 127.0.0.1 is used as the loopback address.

• Broadcast - Messages that are intended for all computers on a network are sent as broadcasts. These messages always use the IP address 255.255.255.255.

• Class A - This class is for very large networks, such as a major international company might have.

• Network host

• 0xxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx

• IP addresses with a first octet from 1 to 126 are part of this class.

Class B - Class B is used for medium-sized networks. A good example is a large college campus. IP addresses with a first octet from 128 to 191 are part of this class.

• Net Host or Node

• 145.24. 53.107

• 10xxxxxx.xxxxxxxx xxxxxxxx.xxxxxxxx

• Class C - Class C addresses are commonly used for small to mid-size businesses.

• 110xxxxx.xxxxxxx xxxxxxxx.xxxxxxxx

• Class D - Used for multicasts.

• 1110xxxx.

• Class E - Class E is used for experimental purposes only.

Protocol Layer

Application Protocols LayerProtocols specific to applications such as WWW, e-mail, FTP, etc.

Transmission Control Protocol LayerTCP directs packets to a specific application on a computer using a port number. TCP is responsible for routing application protocols to the correct application on the destination computer

Internet Protocol LayerIP directs packets to a specific computer using an IP address.

Hardware Layer Converts binary packet data to network signals and back.(E.g. ethernet network card, modem for phone lines, etc.)

Networking Infrastructure

• A router is usually connected between networks to route packets between them. Each router knows about it's sub-networks and which IP addresses they use.

Internet Infrastructure

• Network Service Providers or NSPs

• Network Access Points or NAPs.

• Metropolitan Area Exchanges or MAEs. MAEs serve the same purpose as the NAPs but are privately owned.

Domain Names and Address Resolution

• Domain Name Service or DNS. The DNS is a distributed database which keeps track of computer's names and their corresponding IP addresses on the Internet.

• The application protocol that makes the web work is Hypertext Transfer Protocol or HTTP. HTTP is the protocol that web browsers and web servers use to communicate with each other over the Internet.

• E-mail uses an application level protocol called Simple Mail Transfer Protocol or SMTP. SMTP is also a text based protocol, but unlike HTTP, SMTP is connection oriented. SMTP is also more complicated than HTTP.

• FTP 20/21

• Telnet 23

• SMTP 25

• HTTP 80

Use of internet

• Online commerce

• Customer Service

• Organization support

• Information

Services by Internet

• Communication services:

E-mail, chat, discussion list

• Information Retrieval services:

www, ftp, telnet, http

Some Terms

1. www: the Web is one of the services that runs on the Internet. It is a collection of interconnected documents and other resources, linked by hyperlinks and URLs. In short, the Web is an application running on the Internet

2. FTP :File Transfer Protocol (FTP) is a standard network protocol used to exchange and manipulate files over an Internet Protocol computer network, such as the Internet. FTP is built on a client-server architecture

A host that provides an FTP service may additionally provide anonymous FTP access. Users typically login to the service with an 'anonymous' account when prompted for user name.

3. Telnet: Telnet (teletype network) is a network protocol used on the Internet or local area networks to provide a bidirectional interactive communications facility. Typically, telnet provides access to a command-line interface on a remote host via a virtual terminal connection which consists of an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP).

4.HTTP:Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, hypermedia information systems.Its use for retrieving inter-linked resources led to the establishment of the World Wide Web.

5. TCP/IP: The Internet Protocol Suite (commonly known as TCP/IP) is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two networking protocols defined in this standard.

6. SMTP: Simple Mail Transfer Protocol (SMTP) is an Internet standard for electronic mail (e-mail) transmission across Internet Protocol (IP) networks.

7. POP3:the Post Office Protocol (POP) is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. POP and IMAP (Internet Message Access Protocol) are the two most prevalent Internet standard protocols for e-mail retrieval.

8. GOPHER: Gopher is a distributed document search and retrieval network protocol designed for the Internet. It was released in 1991 by Paul Lindner and Mark McCahill of the University of Minnesota.