The Structure of Data table

A Database framework organizes raw data into a hierarchy of relationships.  At the lowest level of this hierarchy, the data is broken down into fundamental building blocks, called fields.  A field defines an aspect of that data that is common to all instances of it; for example, a Last Name field would contain persons' last names and a firs name field would contain their first names.

Fields are combined into record.  A very simple record might consist of first and last name fields and each record would then contain the full name of a person.

A set of such records is called a table (or in some systems, a data file or file).  A phone book is real world example of a table.  For each listing in the phone book, there are three fields: one for names, another for addresses and another for phone number-forms a records.  The records are alphabetized into a list and bound together to make up the table/phone book.

By breaking up data in to fields and records, a DBMS can access and sort the data very quickly.  For example, a DBMS can sort a mailing list alphabetically using the Last Name and First Name fields and sort it ZIP code other by using a ZIP code field.

What is database

There are a large number of networked database products on the market, but they all have the same fundamental purpose: to provide a centralized repository data, allowing multiple users to access it, update it and produce meaningful information based on it, all the while protecting it  from accidental corruption and enforcing your business rules for keeping it accurate and reliable.  That's a large job for a software program and many programs require the ongoing support of a skilled database manager.

The integrity of the database is vital to the survival of many large and small businesses today.  A Database Management System (DBMS) is an application that organizes data into the framework and uses that framework to provide access to the data and vehicle for processing modifying) it.

What is Shell Account

Usint dialup access to the HOST computer.  By connecting to the host computer, the users to be able to use all Intenet services.  In this mode,the users would be using a simple terminal emulation from their PCs and will require any special software on their machine.

TCP/IP account

Leased line

This is for those who want the connection to be provided to them on 24-hour basis.  In this case you are provided with a leased line which is fast and permanent.  Depending on your bandwidth requirements, you can get a leased line ranging from 24 kbps to 2 mbps.

Dial-up and Terminal Emulation

At best it is the simplest method of connecting to the net. You just need a PC with modem and an account from ISP.  In this case the computer uses terminal emulation software and not TCP/IP to talk to the Internet host computer.  The host computer in turn uses TCP/IP connect to the Internet. 

Client Server Architecture

A design model for applications running on a network, in which the bulk of the back-end processing, such as performing a physical search of a databased, takes place on a server.  The front-end processing, which involves communication with the user, is handled by smaller programs distributed to the client workstations. The client/server processing concept is an extension of shared device processing.  A number of operation systems support TCP/IP protocol.  These include Netware Windows NT and Windows 2000.

Netware Client Server-

In this model, both application and data reside on the file server.  When a network user needs access to the application and  the data both are loaded over the network onto that user's workstation.  In fact, the client program running on a workstation or PC is responsible for all interaction with the user.

Windows NT-

With the features like built-in remote access, administrative wizards, network management, support for Netware directory Services an Internet server, this has become a very useful tool for network administration.  The wizards in it would guide you to various common asks, such as adding a user or printer, or sharing your PCs resources.

What is Search Engine

A special software that enable to systematically search the Web .  All you need is to provide a few key words (called 'query') about the desired  topic and the Search Engine will provide you a Web Page listing on the topic.  Some of the popular search engines are Alta Vista ; India Times; Google; Yahoo; and Info seek etc.

Hyper Text Transfer Protocol (HTTP)

It is used at the communication protocol to transport hypertext documents over the internet.  It tells the server what to send to the client, so the client can view webpages.  FTP site or other areas on the Net. The HTTP is a method used on Internet to access information.  It work in combination with the World Wide Web (WWW), Which is responsible for accessing hyper text document.

Uniform resource locator(URL)

A URL describes the location and a method of accessing a resource on  the internet.  For example, the URL "http://www.adobe.com" may lead you to the home page of the company called Adobe Corporation, makers of various publishing software like page Maker, etc.  Each URL is unique .  It identifies a particular point on the Internet.  It consists of a string that supplies the Internet address of a resource on the WWW along with the protocol by which the resource is accessed.  The most common URL types are 'gopher' which gives the Internet address of a Gopher directory, and 'FTP' which gives the address of a FTP resource.  All Web sites have URLs.  One could say a URL is what a telephone number is to a telephone or a street address is to a house.

What is e-mail address

As mentioned above the e-mail address of the publishing company is abc@nda.vsnl.net.in.  In this case abc is the user name.  The @ t the rate) symbol in the middle is a must.  Then after that you have the various codes, as mentioned above.  In spoken terms this would the mentioned as'abc @nda dot vsnl dot net dot in'.

What is Web Address

An Web address uniquely identifies a node on the Internet.  Web address may also refer to the name or IP of a Web site (URL).

What is domain name

Domain names are used to identify one or more IP addresses.  For example, the domain name microsoft.com represents about a dozen IP addresses.  Domain names are used in URLs to identify particular Web pages.  For example, in the URLhttp://wwwpcwebopedia.com/index.html, the domain name is pcwebopedia.com.

Every domain name has a suffix that indicates which top level domain (TLD) it belongs to. There are only a limited number of such domains. For example:

gov - Government agencies

edu - Educational institutions

org - Organizations (nonprofit)

mil - Military

com - commercial business

net - Network organizations

ca - Canada

th - Thailand

Because the Internet is based on IP addresses, not domain names, every Web server requires a Domain Name System (DNS) server to translate domain names into IP addresses.

What is Internet Addressing System

Internet address is made up of a code or series or letters, numbers and /or symbols by which  the Internet identifies you or a location where information is stored.  Through the use of this addresses, people can send you e-mail look at your Web site and send or receive files and documents.

what is Packet Switching

In this scheme, no dedicated path is reserved between source and destination.  The data to be sent is 'wrapped up' in a packet and launched into the network.  Circuit is switching is extensively  used in the public telephone networks, with each conversation between users traveling over a dedicated path from one telephone through the central switch to the other party.

Hardware requirement of LAN

There are mainly 4 hardware devices which are required to establish linkage between geographically separated computers.  These are:

• Bridges
• Routers
• Gateways
• x.25 Standard Interface

Bridge-  These are used to connect two LANs that use the indentical protocols over a wide area.  The bridge acts as an address filters which picks up packets from one LAN that are intended for a destination on another LAN and passes these packets on the network. The amount of processing required at the bridge is minimal because all the devices use the same protocols.  In case the distance between two LANs is very large then the user is required to employ two identical bridges at either end of the communication link.

Routers-  It is special type of device that can be used to connect networks that may not be similar.  Such type of device provide connectivity between two LANs and two WANs over large geographical distances.  These device operate at the Network Layer of the OSI model.  These devices participate in a routing protocol to access the network topology, and on the basis  of this information routers compute the best route from a sender to the receiver.

Gateways-  These are used dsto connect two dissimilar LANs.  The terms Gateways and Routers are used interchangeably, though there is discriminating difference between the two.  A router  operates at the networklayer whereas a gateway operates on the application layer of the OSI model.  

x.25 Standard Interface-  X.25 is a protocol  for interfacing to a Public Packet Switched Network.  It is not a protocol used for immplementing a network.  Two systems that support X.25 can't necessarily be connected back-to-back.  They can only be connected through a DCE in a Public Packet Switched Inernational Telegraph and Telephone Consultative committee (ITTCC) developed X.25 as the standard interface between the Data Terminal Equipment (DTE)and Data Circuit Terminating Equipment (DCTE).  This recommendation has been widely accepted as the industry standard for public packet switched networks.

Server and Workstations

One of the major benefits of implementation of LAN is sharing expensive resources such as storage devices, printers, etc. This is achieved through providing servers on  the LAN.  It is dedicated computer that controls one or more resources.  This contains both hardware and software interface  for LAN.  Three major categories of services used in LANs are.

• File Server
• Printer Server
• Modem Server

In networking file server is used to share storage for files.  Besides providing storage space for files in a LAN environment, it is used for taking periodical backup, and also to provide gateway to other servers with and between LANs.  Similarly printer server is used to handle printing works of all workstation connected in the network or simply to use a telephone.  A modem server is used to share this expensive resource by all connected workstations in a network ring.

 

Hardware for LAN

The following are the major hardware components/devices for establishing LAN:

• Transmission Channel
• Network Interface Unit or NIU
• Servers
• Workstations

Asynchronous Transfer Mode (ATM)

It is new in term of modes available for networking.  It can carry both voice and data. It is also based on packet data technology. On an ATM network, every station transmits continuously.  ATM is a circuit based network, in that a virtual circuit is set up between two devices to communicate over the network.

what is FDDI

It is high performance fiber optic token ring network.  It is used with high bandwidth.  FDDI is implemented without hubs, although you can use devices called concentrate to perform a similar function.

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

In local area networks a method used by computer's access to the communication channel. With CSMA/CD, each component of the network (called a node) has an equal  right to access the communication channel.  If two computers try to access the network at the same time, the network uses a random number to decide which computer gets to use the network first.

This channel access method works well with relatively small to medium sized networks (two or three dozen nodes). Large networks use alternative channel access methods, such as polling and token passing to prevent overloading or locking up the  system.

What is Ethernet

A networking hardware communication, and cabling standard, originally developed by xerox corporation that can link  up to 1,024 node in a bus network.  A high-speed standard using a baseband (single channel) communication technique.  Ethernet provides for a raw data transfer rate of 10 megabits per second (mbps), with actual throughout in  the range of 2 to 3 megabits per second. Ethernet uses carrier sense multiple access with collision detection (CSMA/CD) techniques to prevent network failures when two devices try to access the network at the same time.

What is server

A term server refers to any device that offers a service to network users.  A server can be hardware, software or both.  Server can be PCs doing double duty, or they can be specific purpose devices,  The most common ones are file servers, print servers and gateways(also known communications server).

.What is work station

A workstation is a computer used as a node on a network primarily used to run application programs.  In the IBM Token Ring Network, any IBM PC compatible computer can be used as a workstation.