SERVERS AND WEBSERVERS….
Server :
(ser´ver) (n.) A computer or device on a network that manages network resources. For example, a file server is a computer and storage device dedicated to storing files. Any user on the network can store files on the server.
A print server is a computer that manages one or more printers, and a network server is a computer that manages network traffic. A database server is a computer system that processes database queries.
Definition of server :
A server is an application running on a computer that delivers a service. For example, a web server will deliver web pages when requested by a browser (called client in this context). The way a server and a client dialogs is called a protocol. For instance, HTTP is the protocol used between a browser an a web server.
Among the many services provided by the Internet servers are:
* World Wide Web
* the domain name system
* FTP file transfer
* chat and instant messaging
* voice communication
* streaming audio and video
* online gaming
Virtually every action taken by an ordinary Internet user requires one or more interactions with one or more servers.
Servers in daily life :
A server is any combination of hardware or software designed to provide services to clients.
A server is a computer that handles requests for data, email, file transfers, and other network services from other computers (ie, clients).
A computer that stores application and data files for all workstations on a network; also referred to as a file server.
A server is the computer program (housed in a computer) that serves requested HTML pages or files by the client.
A server is a computer that stores information, and "serves" that information to viewers who request to see it. Everything that you see on the Internet is stored somewhere on a server.
A computer or application, that provides a service to client software on other computers. Servers are used for web hosting and other web applications.
Types of server :
- Application server.
- Communication server.
- Datebase server.
- Fax server.
- File server.
- Game server.
- Home server.
- Name server.
- Print server.
- Proxy server.
- Sound server.
- Standalone server.
- Web server.
- Web feed server.
- Client server.
- Catalog server.
Web Server :
(1) A computer program that serves the requested files which form web pages to the client's browser.
(2) A web server can also refer to the computer that runs the server software and holds the files for one or more websites.
Historical notes :
In 1989 Tim Berners-Lee proposed to his employer CERN (European Organization for Nuclear Research) a new project, which had the goal of easing the exchange of information between scientists by using a hypertext system. As a result of the implementation of this project, in 1990 Berners-Lee wrote two programs:
* a browser called WorldWideWeb;
* the world's first web server, later known as CERN HTTPd, which ran on NeXTSTEP.
The world's first web server
Between 1991 and 1994 the simplicity and effectiveness of early technologies used to surf and exchange data through the World Wide Web helped to port them to many different operating systems and spread their use among lots of different social groups of people, first in scientific organizations, then in universities and finally in industry.
Common features :
1. Virtual hosting to serve many web sites using one IP address.
2. Large file support to be able to serve files whose size is greater than 2 GB on 32 bit OS.
3. Bandwidth throttling to limit the speed of responses in order to not saturate the network and to be able to serve more clients.
A home web server
Load limits
A web server (program) has defined load limits, because it can handle only a limited number of concurrent client connections (usually between 2 and 80,000, by default between 500 and 1,000) per IP address (and TCP port) and it can serve only a certain maximum number of requests per second depending on:
* its own settings;
* the HTTP request type;
* content origin (static or dynamic);
* the fact that the served content is or is not cached;
* the hardware and software limits of the OS where it is working.
When a web server is near to or over its limits, it becomes overloaded and thus unresponsive.
Kernel-mode and user-mode web servers :
A web server can be either implemented into the OS kernel, or in user space (like other regular applications).
An in-kernel web server (like TUX on Linux or Microsoft IIS on Windows) will usually work faster because, as part of the system, it can directly use all the hardware resources it needs, such as:
* non-paged memory;
* CPU time-slices;
* network adapters buffers.
Web servers that run in user-mode have to ask the system the permission to use more memory or more CPU resources. Not only these requests to the kernel take time, but they are not always satisfied because the system reserves resources for its own usage and has the responsibility to share hardware resources with all the other running applications.
Also applications cannot access the system internal buffers, which is causing useless buffer copies that create another handicap for user-mode web servers.
Overload causes :
At any time web servers can be overloaded because of:
* Too much legitimate web traffic (i.e. thousands or even millions of clients hitting the web site in a short interval of time. e.g. Slashdot effect);
* DDoS (Distributed Denial of Service) attacks;
* Computer worms that sometimes cause abnormal traffic because of millions of infected computers (not coordinated among them);
* XSS viruses can cause high traffic because of millions of infected browsers and/or web servers;
* Internet web robots traffic not filtered/limited on large web sites with very few resources (bandwidth, etc.);
* Internet (network) slowdowns, so that client requests are served more slowly and the number of connections increases so much that server limits are reached;
Market structure
Given below is a list of top Web server software vendors published in a Netcraft survey in January 2009.
Market share of major web servers
Vendor | Product | Web Sites Hosted | Percent |
96,531,033 | 52.05% | ||
61,023,474 | 32.90% | ||
9,864,303 | 5.32% | ||
3,462,551 | 1.87% | ||
2,989,416 | 1.61% | ||
Oversee | Oversee | 1,847,039 | 1.00% |
Others | - | 9,756,650 | 5.26% |
Total | - | 185,474,466 | 100.00% |
Application :
* Your local website behaves more like the live one. For example, you can configure directory security, test your custom error pages etc before commiting them to the production environment.
* You can use server-side scripting languages such as PHP and ColdFusion.
* Allows you to standardize your coding. For example, you can use root-relative paths for your image references and hyperlinks (i.e. "/directory/image.gif"). In other words, your paths can represent the website structure, rather than the directory structure of your computer.
* Knowledge. The knowledge you gain from using your own web server will help you understand how it works in the live environment. This will most certainly help you when you need to communicate with your hosting provider - you'll be able to use terminology that makes it easier for them to understand your request/issue.
Advantages and Disadvantages :
Advantages :
Cheap : Cost and Affordable Price:Available at Most Affordable Cost. Today thousands of Companies Offering at Very Cheap Prices.Most Common Option In the Industry. Its Market Share is Also High as Compared to Other Host Options.
No Maintenance Cost:It Comes with All Inclusive Price.You would like Not Bother About Server Maintenance and Setup
Fast Setup : In Case of Shared Host Your Site Could Be Live With in 24 Hours of Purchase.Unlike Dedicated Host it Could Setup Instantly.No need to be a Technically Sound Person.
Good For Small Sites : and :It is the Best Option For Beginners and Small Websites.
Disadvantages :
Security issues :Security is one Of Main Disadvantage.
Backup Process is Very Hard Task As the thousands of Websites Hosted on Same Web Server.Security is one of chief disadvantage of Shared Hosting. Backup Process is exceptionally hard task as the thousands of Web sites Hosted on same Web Server.
Limited Resources:
Thousands Of Web Sites Using Same Resources.That's Why If One User Site consumes More Resources of web Server Other Sites Might Slow Down.In Other Way One Problematic Website May Cause Crash of All Other Sites in the Same Server.
Dynamic IP:
Many Providers Does not Give Static ip For Shared Website Hosting. Dynamic ip is outstandingly risk when You Going for E-commerce Transactions On Your WebSite.This
Disadvantage Could Overcome By Choosing Static iP.Some Companies Gives a Option to Choose Static or Dynamic IP. They Will Charge You Small Amount for Static IP.
Not good For Large Data Base E-Commerce Sites:
Large Websites Need Plenty of Server Resources.So They are not Suitable of it. Final Word: No Doubt It Has Major Share in Industry. But Before You Going to Buy a Shared host Plan, You Must Know Your Requirements.Then Proceed. Best of Luck..
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