INTRODUCTION TO NETWORKS

INTRODUCTION:
Now a days practically every business, no matter how small uses Computers to handle
various transactions and as business grows they often need several people to input and
process data simultaneously and in order to achieve this it is necessary that all the
computers are networked. Computer networks are simply a group of Computers
connected by cables or other media such that they can share data and resources

The basic components of networks. Here you will learn about the different types of
Networks, Network topology, Network protocols, Network Architecture, Network
medium and the basic hardware components that are required in setting up of a Computer
Network

COMPUTER NETWORK

A Computer network is a group of two or more computer systems linked together such
that they can share information and resources. There are many types of computer
networks, including:

TYPES OF COMPUTER NETWORKS:

LAN : LAN is a computer network that spans a relatively small area. Most LANs are
confined to a single building or group of buildings.
However, one LAN can be connected to other LANs over
any distance via telephone lines and radio waves. A system
of LANs connected in this way is called a wide-area
network (WAN).

Most LANs connect workstations and personal computers.

Each node (individual computer ) in a LAN has its own
CPU with which it executes programs, but it is also able to
access data and devices anywhere on the LAN. This means
that many users can share expensive devices, such as laser printers, as well as data. Users
can also use the LAN to communicate with each other, by sending e-mail or engaging in
chat sessions. There are many different types of LANs Ethernets being the most common
for PCs.

LANs are capable of transmitting data at very fast rates, much faster than data can be
transmitted over a telephone line; but the distances are limited, and there is also a limit on
the number of computers that can be attached to a single LAN.

MAN : MAN stands for Metropolitan Area Network, it is a

data network designed for a town or city. In terms of
geographic breadth, MANs are larger than local-area networks
(LANs), but smaller than wide-area networks (WANs). MANs
are usually characterized by very high-speed connections
using fiber optical cable or other digital media.

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WAN :

WAN is a computer network that spans a relatively

large geographical area. Typically, a WAN consists
of two or more local-area networks (LANs).

Computers connected to a wide-area network are often

connected through public networks, such as the telephone
system. They can also be connected through leased lines or
satellites. The largest WAN in existence is the Internet.

In addition to these types, the following characteristics are also used to categorize
different types of networks:

NETWORK ARCHITECTURE

Depending on the Architecture used Networks can be classified as Client/Server or Peer-

to- Peer

Client/server Architecture:

NT/Server Architecture is
one in which the client
(personal computer or
workstation) is the
requesting machine and
the server is the supplying
machine, both of which
are connected via a local
area network (LAN) or wide area network (WAN). Since the early 1990s, client/server
has been the buzzword for building applications on LANs in contrast to centralized minis
and mainframes with dedicated terminals.

The client contains the user interface and may perform some or all of the application
processing. Servers can be high-speed microcomputers, minicomputers or even
mainframes. A database server maintains the databases and processes requests from the
client to extract data from or update the database. An application server provides
additional business processing for the clients.

The term client/server is sometimes used to contrast a peer-to-peer network, in which any
client can also act as a server. In that case, client/server means nothing more than having
a dedicated server.

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However, client/server architecture means more than dedicated servers. Simply
downloading files from or sharing programs and databases on a server is not true
client/server either. True client/server implies that the application was originally designed
to run on a network and that the network infrastructure provides the same quality of
service as traditional mini and mainframe information systems.

NON-CLIENT/SERVER
In non-client/server architecture, the server is nothing more than a remote disk drive. The
user's machine does all the processing. If many users routinely perform lengthy searches,
this can bog down the network, because each client has to pass the entire database over
the net. At 1,000 bytes per record, a 10,000 record database requires 10MB of data be
transmitted.

Peer – to – Peer Architecture

A type of network in which each
workstation has equivalent
capabilities and responsibilities.
Here each work station acts as
both a client and a server. There
is no central repository for
information and there is no
central server to maintain. Data
and resources are distributed
throughout the network, and each
user is responsible for sharing
data and resources connected to
their system. This differs from
client/server architectures, in
which some computers are dedicated to serving the others. Peer-to-peer networks are
generally simpler and less expensive, but they usually do not offer the same performance
under heavy loads.

NETWORK TOPOLOGY
A network topology describes the configuration of a network (how the network
components are connected together). There are FOUR main topology's.

Star : The star topology uses a central hub

through which all components are
connected. In a computer network, the
central hub is the host computer, and at the
end of each connection is a terminal.

A star network uses a significant amount of cable (each terminal is wired back to the
central hub, even if two terminals are side by side several hundred meters away from the
host). All routing decisions are made by the central hub, and all other workstations can be
simple.

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An advantage of the star topology is failure in one of the terminals does not affect any
other terminal, how-ever, failure of the central hub affects all terminals.

This type of topology is frequently used to connect terminals to a large time-sharing host
computer.

Ring : The ring topology connects workstations in a closed loop. Each terminal is
connected to TWO other terminals (the next and the previous), with the last terminal
being connected to the first. Data is transmitted around the ring in one direction only,
each station passing on the data to the next station till it
reaches its destination.
Faulty workstations can be isolated from the ring.
When the workstation is powered on, it connects itself
into the ring. When power is off, it disconnects itself
from the ring and allows the information to bypass the
workstation.
Information travels around the ring from one workstation to the next. Each packet of data
sent on the ring is prefixed by the address of the station to which it is being sent to. When
a packet of data arrives, the workstation checks to see if the packet address is the same as
its own. If it is, it grabs the data in the packet. If the packet does not belong to it, it sends
the packet to the next workstation in the ring.

The common implementation of this topology is token ring. A break in the ring causes the
entire network to fail. Individual workstations can be isolated from the ring.

Bus : The bus topology connects workstations using a single cable. Each workstation is
connected to the next workstation in a point to point fashion. All workstations connect to
the same cable.
If one workstation goes faulty, all
workstations are affected.
Workstations share the same cable
for the sending and receiving of
information. The cabling costs of
bus systems are the least of all the
different topologies. Each end of
the cable is terminated using a
special terminator.
The common implementation of this topology is Ethernet. A message transmitted by one
workstation is heard by all the other workstations.

Mesh : The mesh topology connects all computers to each

other. The cable requirements are high, but there are
redundant paths built in. Any failure of one computer allows
all others to continue, as they have alternative paths to other
computers.

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Mesh topology's are used in critical connection of host computers (typically telephone
exchanges). Alternate paths allow each computer to balance the load to other computer
systems in the network by using more than one of the connection paths available.

NETWORK PROTOCOLS
 Protocols define a common set of rules and signals that computers on the Network
use to communicate.
 The two popular protocols used are Ethernet and Token Ring.

Ethernet
Ethernet is the most widely-used LAN
access method, which is defined by the
IEEE 802.3 standard (Token Ring is the next
most popular). Ethernet is normally a shared
media LAN. All stations on the segment
share the total bandwidth, which is either 10
Mbps (Ethernet), 100 Mbps (Fast Ethernet)
or 1000 Mbps (Gigabit Ethernet). With
switched Ethernet, each sender and receiver
pair have the full bandwidth.

Ethernet was invented by Robert Metcalfe and David Boggs at Xerox PARC in 1973,
which first ran at 2.94 Mbps. Metcalfe later joined Digital where he facilitated a joint
venture between Digital, Intel and Xerox to collaborate further on Ethernet. Version 1
was finalized in 1980, and products shipped in the following year. In 1983, the IEEE
approved the Ethernet 802.3 standard.

Token Ring
Token Ring is a local area network (LAN) developed by IBM (IEEE 802.5). It uses a
token ring access method and connects up to 255 nodes in a star topology at 4 or 16
Mbps. All stations connect to a central wiring hub called the MAU (Multistation Access
Unit) using a twisted wire cable. The central hub makes it easier to troubleshoot failures
than a bus topology.

Token Ring is more deterministic than Ethernet.

It ensures that all users get regular turns at
transmitting their data. With Ethernet, all users
compete to get onto the network.

There are two types of Token Ring networks.

Type 1 Token Ring networks allow up to 255
stations per network and use shielded twisted pair wires with IBM style Type 1
connectors. Type 3 Token Rings allow up to 72 devices per network and use unshielded
twisted pair (Category 3, 4 or 5) with RJ-45 connectors.

Token Ring is a data link protocol (MAC layer protocol) and functions at layers 1 and 2
of the OSI model

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 NETWORK MEDIUM

Once you have the network cards installed and interfaced in your computer, you need a
way to connect them to each other.
The network media used can be:
 wire ( Bounded) or
 wireless (Unbounded).

Bounded Media : Wires or network cables are referred to as bounded media because the
signal travels through a physical media shielded on the outside (bounded) by some
material. Bounded media are very good for LANs because they offer good speed, good
security and low cost.
Examples of bounded media CO-AXIAL,TWISTED PAIR & OPTICAL FIBER.

Twisted Pair Cable

Twisted Pair Cable is the most common form of cable today, it is used to connect
telephone subscribers to exchanges (switching
centres) and wire buildings. Two insulated
wires are twisted around each other, and
combined with others into a cable. Twisted
pair is a favorite choice for interconnecting
PC's on a Local Area Network (LAN). In
general, each twisted pair supports a single
voice channel.

Twisted pair used in Local Area Networks has

several ratings. Category 3 has a speed rating of 10 million bits per second (the speed of
Ethernet), whereas category 5 has a speed rating of 100 million bits per second. UTP
(Unshielded twisted pair) is cable, which has no ground shield. Cables are often provided
with a ground shield, which helps to reduce signal interference from external sources,
thus making the signal traveling down the cable less prone to alteration. Twisted pair
cable is provided in two forms, UTP and STP. The diagram below shows UTP Category 5
cable.

UTP has the advantages of

- a high installed base
- cheap to install
- easy to terminate

Its disadvantages are

- very noisy
- limited in distance
- suffers from interference

Coaxial Cable
Co-axial cable till recently, extensively used to support toll traffic and long distance links.
Today, it is being replaced by micro-wave, satellite or fiber optic links. Coaxial cable is a

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two wire conductor with a larger bandwidth than twisted pair cable. It is used in
television, radio, and Ethernet based LANS. Each coaxial cable supports about 60 speech
channels.

Coaxial cable is used extensively in networking and data communications. It is used for
local area networking, linking PC's together. The networking protocol commonly used
with coaxial cable is ETHERNET, which describes how data is formatted and transmitted
along a shared cable system.

Coaxial cable has the advantages of

Its disadvantages are,
- cheap to install - limited in distance
- conforms to standards - limited in number of connections
- widely used - terminations and connectors must be
done properly
Fibre Optic Cable:

This cable is made from fine strands of silicon

(glass), coated with a plastic sheath. The signals
are converted to light pulses before being sent.
Each fibre optic strand can support thousands of
speech channels and multiple TV channels
simultaneously. It is used mainly for long haul
links and intercontinental links.

A strand of silicon glass fibre (thinner than a human hair), is coated with a refractive
surface. When light (provided by a laser) is show into the strand, it travels along the fibre
strand (the refractive layer prevents it from escaping). It is used for long haul
telecommunications links, high speed data communications links for computers, and
information services to homes (eg, PAY TV).

Fibre optic cable

The advantages are Its disadvantages are,

- high capacity - costly
- immune to interference - difficult to join
- can go long distances

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UNBOUNDED OR WIRELESS MEDIA:
Unbounded media does not use any physical connectors between the two communicating
devices. Usually the transmission is sent through the atmosphere, but sometimes it can be just
across a room. Wireless media is used when a physical obstruction or distance blocks the use of
normal cable media.

The three main types of Wireless Media are radio wave, microwave and infrared.

Microwave
Microwave is a radio system which uses very high frequencies
to send and receive data. Because of the high frequencies
involved, stations are located about 30 kilometers apart and in
line of sight (visible to each other).
Microwave systems have sufficient bandwidth capacity to
support a large number of voice channels and one or two TV
channels.

Microwave sys have the advantage of

- medium capacity
- medium cost
- can go long distances

Its disadvantages are,

- noise interference
- geographical problems due to line of sight requirements
- becoming outdated

HARDWARE USED IN NETWORKING

Network Interface Card

It is also known as Network adapter. It is a printed

circuit board that plugs into both the clients
(personal computers or workstations) and servers
and controls the exchange of data between them.
The network adapter provides services at the data
link level of the network, which is also known as
the access method (OSI layers 1 and 2).

The most common network adapters are Ethernet and Token Ring. Sometimes, the Ethernet
adapter is built into the motherboard. LocalTalk, which provides the data link services of Apple's
AppleTalk network, is built into all Macintoshes.

A transmission medium, such as twisted pair, coax or fiber optic, interconnects all the adapters
in the network. A network adapter is also called a NIC, or network interface card.

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Repeater
Repeater is a communications device that
amplifies or regenerates the data
signal in order to extend the
transmission distance. Available for both
analog and digital signals, it is used
extensively in long distance transmission. It is also used to tie two LANs of the same type
together. Repeaters work at layer 1 of the OSI model. The term may also refer to a multiport
repeater, which is a hub in a 10BaseT network.

Bridges
A Bridge is an electrical device which connects and passes packets between two network
segments. In general, a bridge will forward or discard an incoming frame based on the MAC
address of that frame.
Unlike routers, bridges are protocol - independent.
They simply forward packets without
analyzing and re- routing messages.

Hubs
Hub's major function is to replicate data it
receives from one device attached to it to all
others.
Characteristics :
Hubs come in many flavors. They differ in the amount of devices that can connect to them, the
length of wire that can transmit on, and the type of media they support.

Switch

With respect to Computer Networks switch is a device that filters and forwards packets between
LAN segments. Switches operate at the data link layer (layer 2) of the OSI Reference Model and
therefore support any packet protocol. LANs that use switches to join segments are called
switched LANs or, in the case of Ethernet networks, switched Ethernet LANs.

Routers

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device that forwards data packets from one local area network (LAN) or wide area network
(WAN) to another. Based on routing tables and routing protocols, routers read the network
address in each transmitted frame and make a decision on how to send it based on the most
expedient route (traffic load, line costs, speed, bad lines, etc.).

Gateways

Gateway is a computer that

performs protocol conversion
between different types of
networks or applications. For
example, a gateway can convert a TCP/IP packet to a NetWare IPX packet and vice versa, or
from AppleTalk to DECnet, from SNA to AppleTalk and so on.

They perform complete conversions from one protocol to another rather than simply support one
protocol from within another, such as IP tunneling. Sometimes routers can implement gateway
functions. An electronic mail, or messaging, gateway converts messages between two different
messaging protocols.

INTERNET
Internet Basics :
What is the Internet?
 A loosely configured global wide-area network.
 Millions of people visit and contribute to the Internet, through e-mail and the World Wide Web.
 Began as a Department of Defence project.

Early history of the Internet

 In the 1950s the U.S. Department of Defence became concerned that a nuclear attack could
Disable its computing (and thus planning and coordinating) capabilities.
 By 1969 the Advanced Research Projects Agency Network (ARPANet) had been constructed.
 The first computers to be connected were ones at the University of California at Los Angeles, SRI
International, the University of California at Santa Barbara, and the University of Utah.

TYPE OF INTERNET CONNECTION

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1. Dial-up Access
2. Direct or Dedicated Access

1. Dial-up Access
In this type of connection a modem and regular telephone lines are required to connect to internet.
Advantages
i. Less expensive
ii. Better option for individuals
iii. Requires simple hardware and software recourses.
Disadvantages
i. Slow speed
ii. Low reliability i.e. connection to internet is break with little disturbance

Types of Dial-Up access

a. Shell account
Also called as Host/Terminal connection .In this account type your computer acts as if it were
a terminal directly connected to some internet host. One can view only text-based information
on the terminal. You cannot view graphics and hear sounds. Shell accounts are not very user
friendly.

b. Individual computer TCP/IP link

In this type of connection your computer functions as an internet host. It provide graphical
interface hence user friendly.

2. Direct or Dedicated Access

In this type of connection a dedicated leased phone line is used between your PC or network and
ISP(Internet Service Provider).It is very expensive and difficult to setup and so organizations use
this method.
Advantages
i. Fast speed.
ii. Better reliability.
Disadvantage
i. Very expensive
ii. Difficult to setup(install).

Most popular Internet protocols used in internet :

The most popular Internet protocols include:
• TCP/IP
• HTTP (Hypertext transfer protocol)
• FTP (File transfer protocol)
Each protocol is used for a different purpose, but all of them are important.

TCP/IP

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  Every computer and network on the Internet uses the same protocols (rules and
procedures) to control timing and data format.
 The protocol used by the Internet is the Transmission Control Protocol/Internet Protocol,
or TCP/IP.
 No matter what type of computer system you connect to the Internet, if it uses TCP/IP, it
can exchange data with any other type of computer.
 The protocols that underlie the basic operation of the Internet are TCP (transmission
control
protocol) and IP (Internet protocol).
 Developed by Internet pioneers Vinton Cerf and and Robert Kahn, these protocols
establish
rules about how data are moved across networks and how network connections are established
and broken.

HTTP :
Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed,
collaborative, hypermedia information systems. Its use for retrieving inter-linked resources led to
the establishment of the World Wide Web
HTTP is a request/response standard of a client and a server. A client is the end-user, the server
is the web site. The client making an HTTP request—using a web browser, spider, or other end-
user tool—is referred to as the user agent. The responding server—which stores or creates
resources such as HTML files and images—is called the origin server. In between the user agent
and origin server may be several intermediaries, such as proxies, gateways, and tunnels. HTTP is
not constrained to using TCP/IP and its supporting layers, although this is its most popular
application on the Internet. Indeed HTTP can be "implemented on top of any other protocol on
the Internet, or on other networks." HTTP only presumes a reliable transport; any protocol that
provides such guarantees can be used

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 and utilizes separate control and data connections between the client and
server applications. FTP is also often used as an application component to automatically transfer
files for program internal functions. FTP can be used with user-based password authentication or
with anonymous user access.

Uniform Resource Locator

• People on the Web use a naming convention called the uniform resource locator (URL).
• A URL consists of at least two and as many as four parts.

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 • A simple two part URL contains the protocol used to access the resource followed by the
location of the resource. Example: http://www.cs.depaul.edu/
• A more complex URL may have a file name and a path where the file can be found.

COMPONENTS OF URL

http://facweb.cs.depaul.edu/asettle/ect250/section602/hw

hypertext path that indicates

transfer domain docum
the location of the nam
protocol document in the
host’s file system
Telnet
 Telnet is a specialized service that lets you use one computer to access the contents of
another computer – a Telnet host.
 A Telnet program creates a "window" into the host so you can access files, issue
commands, and exchange data.
 Telnet is widely used by libraries, to allow visitors to look up information, find articles,
and so on.

E-Mail
• In its simplest form, e-mail is an electronic message sent from one computer to another. You
can send or receive personal and business-related messages with attachments, such as
pictures or formatted documents. You can even send computer programs.

HOME PAGE :
The homepage (often written as home page) is the URL or local file that automatically loads
when a web browser starts or when the browser's "home" button is pressed. One can turn this
feature off and on, as well as specify a URL for the page to be loaded.

The term is also used to refer to the front page, webserver directory index, or main web page of a
website of a group, company, organization, or individual. In some countries, such as Germany,

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Japan, and South Korea, and formerly in the US, the term "homepage" commonly refers to a
complete website (of a company or other organization) rather than to a single web page. By the
late 1990s this usage had died out in the US, replaced by the more comprehensive term "web
site".

SEARCH ENGINE
A Web search engine is a tool designed to search for information on the World Wide Web. The
search results are usually presented in a list and are commonly called hits. The information may
consist of web pages, images, information and other types of files. Some search engines also
mine data available in databases or open directories. Unlike Web directories, which are
maintained by human editors, search engines operate algorithmically or are a mixture of
algorithmic and human input.

A search engine operates, in the following order

1. Web crawling
2. Indexing
3. Searching

Web search engines work by storing information about many web pages, which they retrieve
from the WWW itself. These pages are retrieved by a Web crawler (sometimes also known as a
spider) — an automated Web browser which follows every link it sees. The contents of each
page are then analyzed to determine how it should be indexed (for example, words are extracted
from the titles, headings, or special fields called meta tags). Data about web pages are stored in
an index database for use in later queries. Some search engines, such as Google, store all or part
of the source page (referred to as a cache) as well as information about the web pages, whereas
others, such as AltaVista, store every word of every page they find. This cached page always
holds the actual search text since it is the one that was actually indexed, so it can be very useful
when the content of the current page has been updated and the search terms are no longer in it.
This satisfies the principle of least astonishment since the user normally expects the search terms
to be on the returned pages. Increased search relevance makes these cached pages very useful,
even beyond the fact that they may contain data that may no longer be available elsewhere.

META SERCH ENGINE : A meta-search engine is a search tool that sends user requests to
several other search engines and/or databases. Its like a search engines that search other search
engines.
It simply sends the query to several other search engines and returns a summary of the results.
Therefore, the search results you receive are an aggregate result of multiple searches.

While this strategy gives your search a broader scope than searching a single search engine, the
results are not always better. This is because the meta search engine must use its own algorithm
to choose the best results from multiple search engines. Often, the results returned by a Meta
search engine are not as relevant as those returned by a standard search engine.

What is Boolean Search?

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Boolean searches allow you to combine words and phrases using the words AND, OR, NOT and
NEAR (otherwise known as Boolean operators) to limit, widen, or define your search.
Standard Boolean operators (AND, OR, NOT, or NEAR)
For example:
 Boolean Search Operators
 The Boolean search operator AND is equal to the "+" symbol.
 The Boolean search operator NOT is equal to the "-" symbol.
 The Boolean search operator OR is the default setting of any search engine; meaning, all search
engines will return all the words you type in, automatically.

Examples:
 AND OPERATOR
Using AND narrows a search by combining terms; it will retrieve documents that use both the
search terms you specify, as in this example:
Example: BREAD AND JAM
It will retrieve documents that use both the BREAD and JAM

 OR OPERATOR
Using OR broadens a search to include results that contain either of the words you type in.

Example: APPLE OR MANGO

It will retrieve documents that include results that contain either of APPLE or
MANGO

 NOT OPERATOR
Using NOT will narrow a search by excluding certain search terms.

Example: PEN NOT PENCIL

Narrow a search by excluding PENCIL.

Chatting
Online chat can refer to any kind of communication over the Internet, but is primarily
meant to refer to direct one-on-one chat or text-based group chat (formally also known as
synchronous conferencing), using tools such as instant messengers, Internet Relay Chat.
The expression online chat comes from the word chat which means "informal
conversation".

DOMAIN NAME SYSTEM : The DNS translates Internet domain and host names to IP
addresses. DNS automatically converts the names we type in our Web browser address bar to the
IP addresses of Web servers hosting those sites.
The DNS database resides on a hierarchy of special database servers. When clients like Web
browsers issue requests involving Internet host names, a piece of software called the DNS
resolver (usually built into the network operating system) first contacts a DNS server to
determine the server's IP address. If the DNS server does not contain the needed mapping, it will

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in turn forward the request to a different DNS server at the next higher level in the hierarchy.
After potentially several forwarding and delegation messages are sent within the DNS hierarchy,
the IP address for the given host eventually arrives at the resolver, that in turn completes the
request over Internet Protocol.

WWW
The term WWW refers to the World Wide Web or simply the Web. The World Wide Web
consists of all the public Web sites connected to the Internet worldwide, including the client
devices (such as computers and cell phones) that access Web content. The WWW is just one of
many applications of the Internet and computer networks.
A system of Internet servers that support specially formatted documents. The documents are
formatted in a markup language called HTML (HyperText Markup Language) that supports links
to other documents, as well as graphics, audio, and video files. This means you can jump from
one document to another simply by clicking on hot spots. Not all Internet servers are part of the
World Wide Web.
There are several applications called Web browsers that make it easy to access the World Wide
Web; Two of the most popular being Firefox and Microsoft's Internet Explorer.

INTRANET is the generic term for a collection of private computer networks within an
organization. An intranet uses network technologies as a tool to facilitate communication
between people or work groups to improve the data sharing capability and overall knowledge
base of an organization's employees.
Intranets utilize standard network hardware and software technologies like Ethernet, WiFi,
TCP/IP, Web browsers and Web servers. An organization's intranet typically includes Internet
access but is firewalled so that its computers cannot be reached directly from the outside.

EXTRANET
An extranet is a private network that uses Internet technology and the public telecommunication
system to securely share part of a business's information or operations with suppliers, vendors,
partners, customers, or other businesses. An extranet can be viewed as part of a company's
intranet that is extended to users outside the company. It has also been described as a "state of
mind" in which the Internet is perceived as a way to do business with other companies as well as
to sell products to customers.
An extranet requires security and privacy. These can include firewall server management, the
issuance and use of digital certificates or similar means of user authentication, encryption of
messages, and the use of virtual private networks (VPNs) that tunnel through the public network.

WEB CRAWLERS
A Web crawler is a computer program that browses the World Wide Web in a methodical,
automated manner or in an orderly fashion
This process is called Web crawling or spidering. Many sites, in particular search engines, use
spidering as a means of providing up-to-date data. Web crawlers are mainly used to create a copy
of all the visited pages for later processing by a search engine that will index the downloaded
pages to provide fast searches. Crawlers can also be used for automating maintenance tasks on a
Web site, such as checking links or validating HTML code. Also, crawlers can be used to gather

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specific types of information from Web pages, such as harvesting e-mail addresses (usually for
sending spam).
POP : In computing, 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.[1] POP and IMAP (Internet Message Access Protocol) are the two most prevalent
Internet standard protocols for e-mail retrieval. Virtually all modern e-mail clients and servers
support both. The POP protocol has been developed through several versions, with version 3
(POP3) being the current standard. Most webmail service providers such as Hotmail, Gmail and
Yahoo! Mail also provide IMAP and POP3 service.

SMTP : Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers.
Most e-mail systems that send mail over the Internet use SMTP to send messages from one
server to another; the messages can then be retrieved with an e-mail client using either POP or
IMAP. In addition, SMTP is generally used to send messages from a mail client to a mail server.
This is why you need to specify both the POP or IMAP server and the SMTP server when you
configure your e-mail

WEB PAGE: web pages containing images, videos or other digital assets to form a webpage.

WEBSITE :
 A website, also written Web site,[1] web site, or simply site,[2] is a collection of related
web pages containing images, videos or other digital assets. A website is hosted on at
least one web server, accessible via a network such as the Internet or a private local area
network through an Internet address known as a Uniform Resource Locator.
What are static and dynamic websites?
 There are many static websites on the Internet, you won’t be able to tell immediately if it
is static, but the chances are, if the site looks basic and is for a smaller company, and
simply delivers information without any bells and whistles, it could be a static website.
Static websites can only really be updated by someone with a knowledge of website
development. Static websites are the cheapest to develop and host, and many smaller
companies still use these to get a web presence.
 Dynamic sites on the other hand can be more expensive to develop initially, but the
advantages are numerous. At a basic level, a dynamic website can give the website owner
the ability to simply update and add new content to the site. For example, news and
events could be posted to the site through a simple browser interface. Dynamic features
of a site are only limited by imagination. Some examples of dynamic website features
could be: content management system, e-commerce system, bulletin / discussion boards,
intranet or extranet facilities, ability for clients or users to upload documents, ability for
administrators or users to create content or add information to a site (dynamic
publishing).

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BROWSER and their uses.
Web browser is the software by which we can view the webpage and navigate through the World
Wide Web.
Web browser are either freeware (usually free of cost) or shareware (software that are available
for trial for some specific time after which we have to pay for further up gradation).
Most commonly used browser are Netscape navigator and internet explorer. Other browsers are
Mozilla, Mosaic, Win Web, Cello etc.

TABBED BROWSING: Tabbed browsing is a form of Internet navigation that allows a user to
browse multiple pages in a single window. This feature is for users who do want to view multiple
sites, but don't want to have multiple browser windows open. In the image to the right, you can
see that the Mozilla Firefox 1.0.7 window has two tabs open; just above the browser window

Browsers that support tabbed browsing such as Chrome, Firefox, Opera, and Internet Explorer
allow users to open a link in a new tab by clicking it with your middle-button (mouse wheel).

HTML :
HTML is a computer language devised to allow website creation. These websites can then be
viewed by anyone else connected to the Internet. It is relatively easy to learn, with the basics
being accessible to most people in one sitting; and quite powerful in what it allows you to create.
It is constantly undergoing revision and evolution to meet the demands and requirements of the
growing Internet audience. HTML is a Language, as it has code-words and syntax like any other
language

SERVICE THORUGH EBANKING IN INDIA.

 Account Details: View your bank account details, account balance, download statements
and more. Also view your Demat, Loan & Credit Card Account Details all in one place.
 Fund Transfer: Transfer fund to your own accounts, other Axis Bank accounts or Other
Bank account seamlessly.
 Request Services: Give a request for Cheque book, Demand Draft, Stop Cheque
Payment, Debit Card Loyalty Point Redemption etc.
 Investment Services: View your complete Portfolio with the bank, Create Fixed
Deposit, Apply for IPO etc.
 Value Added Services: Pay Utility bills for more than 160 billers, Recharge Mobile,
Create Virtual Cards, Pay any Visa Credit Card bills, Register for E-statement and SMS
banking etc
 Mobile banking: Using mobile phone to access Internet Banking.
 Recharge prepaid mobile/DTH and a lot more
 Instant alert : Transaction alert is sent to the registered mobile number

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  RAILWAY PASS: Indian railway had tied up with ICICI BANK and you can now make
your railway pass for local train online. The pass will be delivered to your door steps byt
this facility is restricted to Mumbai and thane only

EXAMPLE OF MOBILE COMMERCE

THE MOBILE WALLET: THE IDEA IS TO MOVE the entire contents of your wallet to our
mobile phone. Bank cards, credit cards, loyalty cards and identification cards. Leading
example .s include google wallet and Isis (created by AT&T, T-mobile etc).

Mobile ticketing: Ticket for concerts and other events bought online can be “delivered”
directly to your cell phone. The ticket is sent through a text message or in the form of image, if it
is text message it will be a barcode or a numerical code depending on the e phone you have this
message become your virtual ticket for entry for the concert. (Indian railways is another example
of the same)

Mobile voucher and coupons: This is the traditional newspaper or magazine coupon gone
virtual no more scissor necessary. Mobile coupons can be accessed thorough text message (sent
by the service provider) smart phone application, or social networking sites.

Loyalty cards/ programs / App: Your loyalty cards ( e.g the buy 10 get one free punch cards
for your favorite cafes) are also going on mobile , a prime example is Starbucks iPhone app – an
app that has now processed 26 million mobile payments. Some other good example are punched,
the digital mobile loyalty startup that was recently acquired by google, that allows you to store
all your punch cards on our phone.

Mobile banking : more and more people are conducting their financial transaction by mobile
checking balances, payment of the bills , transferring funds and sending remittances
internationally

ABBRIVATION

IVR - INTERACTIVE VOICE RESPONSE

SMS - SHORT MESSAGE SERVICE
WAP - WIRELESS ACCESS PROTOCOL
IDS - INTRUSION DETECTION SYSTEM
POP - POST OFFICE PROTOCOL
MAN - METROPOLITIAN AREA NETWORK
SMTP - SIMPLE MALE TRANSFER PROTOCOL
UTP - UNSHIELDED TWISTED PAIR
ECS - ELECTRONIC CLEARING SERVICE
EDI - ELECTRONIC DATA INTERCHANGE
ISP - INTERNET SERVICE PROVIDER

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VOIP - VOICE OVER INTERNET PROTOCOL
SCM - SUPPLY CHAIN MANAGEMENT

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