Thu. Sep 23rd, 2021
Web server - Wikipedia

Laptop software program that distributes net pages

A number of net servers could also be used for a excessive site visitors web site; right here, Dell servers are put in collectively getting used for the Wikimedia Basis.

A net server is desktop software program and underlying {hardware} that accepts requests by way of HTTP, the community protocol created to distribute net pages,[1] or its safe variant HTTPS. A consumer agent, generally an online browser or net crawler, initiates communication by making a request for a particular useful resource utilizing HTTP, and the server responds with the content material of that useful resource or an error message. The server may settle for and retailer assets despatched from the consumer agent if configured to take action.

A server could be a single desktop, and even an embedded system corresponding to a router with a built-in configuration interface, however high-traffic web sites usually run net servers on fleets of computer systems designed to deal with giant numbers of requests for paperwork, multimedia information and interactive scripts. A useful resource despatched from an online server could be a preexisting file out there to the server, or it may be generated on the time of the request by one other program that communicates with the server program. The previous is usually sooner and extra simply cached for repeated requests, whereas the latter helps a broader vary of functions. Web sites that serve generated content material often incorporate saved information each time attainable.

Applied sciences corresponding to REST and SOAP, which use HTTP as a foundation for common computer-to-computer communication, have prolonged the appliance of net servers effectively past their authentic objective of serving human-readable pages.

Historical past[edit]

The world’s first net server, a NeXT Laptop workstation with Ethernet, 1990. The case label reads: “This machine is a server. DO NOT POWER IT DOWN!!”

In March 1989 Sir Tim Berners-Lee proposed a brand new mission to his employer CERN, with the purpose of easing the alternate of data between scientists by utilizing a hypertext system.[2][3] The mission resulted in Berners-Lee writing two packages in 1990:

Between 1991 and 1994, the simplicity and effectiveness of early applied sciences used to surf and alternate information by means of the World Vast Internet helped to port them to many alternative working techniques and unfold their use amongst scientific organizations and universities, and subsequently to the trade.

In 1994 Berners-Lee determined to represent the World Vast Internet Consortium (W3C) to control the additional growth of the various applied sciences concerned (HTTP, HTML, and many others.) by means of a standardization course of.

Fundamental frequent options[edit]

Though net server packages differ in how they’re applied, most of them provide the next fundamental frequent options.

  • HTTP: assist for a number of variations of HTTP protocol in an effort to ship variations of HTTP responses appropriate with variations of shopper HTTP requests, e.g. HTTP/1.0, HTTP/1.1 plus, if out there, HTTP/2, HTTP/3;
  • Logging: often net servers have additionally the potential of logging some info, about shopper requests and server responses, to log information for safety and statistical functions.

A couple of different in style options (solely a really quick choice) are:

Path translation[edit]

Internet servers are in a position to map the trail element of a Uniform Useful resource Locator (URL) into:

  • An area file system useful resource (for static requests)
  • An inner or exterior program identify (for dynamic requests)

For a static request the URL path specified by the shopper is relative to the goal web site’s root listing.[4]

Contemplate the next URL as it might be requested by a shopper over HTTP:

The shopper’s consumer agent will translate it right into a connection to with the next HTTP/1.1 request:

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GET /path/file.html HTTP/1.1

The online server on will append the given path to the trail of the (Host) web site root listing. On an Apache server, that is generally /house/www/web site (on Unix machines, often /var/www/web site). The result’s the native file system useful resource:


The online server then reads the file, if it exists, and sends a response to the shopper’s net browser. The response will describe the content material of the file and include the file itself or an error message will return saying that the file doesn’t exist or is unavailable.

Kernel-mode and user-mode net servers[edit]

An internet server software program could be both integrated into the OS kernel, or in consumer house (like different common functions).

Internet servers that run in kernel mode can have direct entry to kernel assets and to allow them to be, in concept, sooner than these operating in consumer mode; anyway there are disadvantages in operating an online server in kernel mode, e.g.: difficulties in growing (debugging) software program whereas run-time essential errors might result in critical issues in OS kernel.

Internet servers that run in user-mode must ask the system for permission to make use of extra reminiscence or extra CPU assets. Not solely do these requests to the kernel take time, however they don’t seem to be all the time glad as a result of the system reserves assets for its personal utilization and has the duty to share {hardware} assets with all the opposite operating functions. Executing in consumer mode may imply ineffective buffer copies that are one other limitation for user-mode net servers.

These days nearly all net server software program is executed in consumer mode (as a result of lots of above small disadvantages have been overcome by sooner {hardware}, new OS variations and new net server software program). See additionally comparability of net server software program to find which ones run in kernel mode or in consumer mode (additionally referred as kernel house or consumer house).


To enhance consumer expertise, Internet servers ought to reply shortly (as quickly as attainable) to shopper requests; until content material response is throttled (by configuration) for some kind of information (e.g. massive information, and many others.), additionally returned information content material must be despatched as quickly as attainable (excessive switch velocity).

For Internet server software program, predominant key efficiency statistics (measured beneath a various load of purchasers and requests per shopper) are:

  • variety of most requests per second (RPS, just like QPS, relying on HTTP model and configuration, kind of HTTP requests, and many others.);
  • community latency response time (often in milliseconds) for every new shopper request;
  • throughput in bytes per second (relying on file measurement, cached or not cached content material, out there community bandwidth, kind of HTTP protocol used, and many others.).

Above three efficiency quantity might fluctuate noticeably relying on the variety of energetic TCP connections, so a fourth statistic quantity is the concurrency degree supported by an online server beneath a particular Internet server configuration, OS kind and out there {hardware} assets.

Final however not least, the precise server mannequin used to implement an online server program can bias the efficiency and scalability degree that may be reached beneath heavy load or when utilizing excessive conclusion {hardware} (many CPUs, disks, and many others.).

Performances of an online server are usually benchmarked by utilizing a number of of the out there
automated load testing instruments.

Load limits[edit]

An internet server (program set up) often has pre-defined load limits, as a result of it might probably deal with solely a restricted variety of concurrent shopper connections (often between 1 and a number of other tens of 1000’s for every energetic net server course of, see additionally the C10k downside and C10M downside) and it might probably serve solely a sure most variety of requests per second relying on:

  • its personal settings,
  • the typical HTTP request kind,
  • whether or not the requested content material is static or dynamic,
  • whether or not the content material is cached, or compressed,
  • the typical community velocity between purchasers and net server,
  • the variety of energetic TCP connections,
  • the {hardware} and software program limitations or settings of the OS of the pc(s) on which the net server runs.

When an online server is close to to or over its limits, it will get overloaded and so it might change into unresponsive.

Causes of overload[edit]

At any time net servers could be overloaded as a consequence of:

  • Extra authentic net site visitors. Hundreds and even tens of millions of purchasers connecting to the web site in a brief interval, e.g., Slashdot impact;
  • Distributed Denial of Service assaults. A denial-of-service assault (DoS assault) or distributed denial-of-service assault (DDoS assault) is an try to make a pc or community useful resource unavailable to its meant customers;
  • Laptop worms that typically trigger irregular site visitors due to tens of millions of contaminated computer systems (not coordinated amongst them)
  • XSS worms may cause excessive site visitors due to tens of millions of contaminated browsers or net servers;
  • Web bots Site visitors not filtered/restricted on giant web sites with only a few assets (bandwidth, and many others.);
  • Web (community) slowdowns (as a consequence of packet losses, and many others.) in order that shopper requests are served extra slowly and the variety of connections will increase a lot that server limits are reached;
  • Internet servers (computer systems) partial unavailability. This will occur due to required or pressing upkeep or improve, {hardware} or software program failures, back-end (e.g., database) failures, and many others.; in these circumstances the remaining net servers might get an excessive amount of site visitors and change into overloaded.

Signs of overload[edit]

The signs of an overloaded net server are:

  • Requests are served with (presumably lengthy) delays (from 1 second to some hundred seconds).
  • The online server returns an HTTP error code, corresponding to 500, 502,[5][6] 503,[7] 504, [8] 408, and even an intermittent 404.
  • The online server refuses or resets (interrupts) TCP connections earlier than it returns any content material.
  • In very uncommon circumstances, the webserver returns solely part of the requested content material. This habits could be thought-about a bug, even when it often arises as a symptom of overload.

Anti-overload methods[edit]

To partially overcome above common load limits and to forestall overload, hottest web sites use frequent methods like:

  • Managing community site visitors, by utilizing:
    • Firewalls to dam undesirable site visitors coming from dangerous IP sources or having dangerous patterns;
    • HTTP site visitors managers to drop, redirect or rewrite requests having dangerous HTTP patterns;
    • Bandwidth administration and site visitors shaping, in an effort to easy down peaks in community utilization;
  • Deploying net cache methods.
  • Utilizing totally different domains or IP addresses to serve totally different (static and dynamic) content material by separate net servers, e.g.:
  • Utilizing totally different domains or computer systems to separate massive information from small and medium-sized information; the concept is to have the ability to totally cache small and medium-sized information and to effectively serve massive or big (over 10 – 1000 MB) information by utilizing totally different settings.
  • Utilizing many net servers (packages) per desktop, each certain to its personal community card and IP tackle.
  • Utilizing many net servers (computer systems) which might be grouped collectively behind a load balancer in order that they act or are seen as one massive net server.
  • Including extra {hardware} assets (i.e. RAM, disks) to every desktop.
  • Tuning OS parameters for {hardware} capabilities and utilization.
  • Utilizing extra environment friendly desktop packages for net servers, and many others.
  • Utilizing different programming workarounds, particularly if dynamic content material is concerned.
  • Utilizing newest environment friendly variations of HTTP (e.g. past utilizing frequent HTTP/1.1 additionally by enabling HTTP/2 and possibly, in close to future, HTTP/3 too each time out there net server software program has dependable assist for the latter two protocols) in an effort to scale back so much the variety of TCP/IP connections began by every shopper and the dimensions of knowledge exchanged (due to extra compact HTTP headers illustration, information compression, and many others.); anyway even when newer HTTP protocols often require much less OS assets typically they might require extra RAM and CPU assets utilized by net server software program (due to encrypted information, information compression on the fly and different implementation particulars).

Market share[edit]

Market share of all websites of main net servers 2005–2018

February 2021[edit]

Beneath are the most recent statistics of the market share of all websites of the highest net servers on the Web by Netcraft
February 2021 Internet Server Survey.

All different net servers are utilized by lower than 5% of the web sites.

February 2020[edit]

Beneath are the most recent statistics of the market share of all websites of the highest net servers on the Web by Netcraft
February 2020 Internet Server Survey.

All different net servers are utilized by lower than 3% of the web sites.

February 2019[edit]

Beneath are the most recent statistics of the market share of all websites of the highest net servers on the Web by Netcraft
February 2019 Internet Server Survey.

All different net servers are utilized by lower than 1% of the web sites.

July 2018[edit]

Beneath are the most recent statistics of the market share of all websites of the highest net servers on the Web by Netcraft
February 2018 Internet Server Survey.

All different net servers are utilized by lower than 1% of the web sites.

February 2017[edit]

Beneath are the most recent statistics of the market share of all websites of the highest net servers on the Web by Netcraft
February 2017 Internet Server Survey.

Product Vendor January 2017 P.c February 2017 P.c Change Chart shade
IIS Microsoft 821,905,283 45.66% 773,552,454 43.16% −2.50 pink
Apache Apache 387,211,503 21.51% 374,297,080 20.89% −0.63 black
nginx NGINX, Inc. 317,398,317 17.63% 348,025,788 19.42% 1.79 inexperienced
GWS Google 17,933,762 1.00% 18,438,702 1.03% 0.03 blue

February 2016[edit]

Beneath are the most recent statistics of the market share of all websites of the highest net servers on the Web by Netcraft
February 2016 Internet Server Survey.

Product Vendor January 2016 P.c February 2016 P.c Change Chart shade
Apache Apache 304,271,061 33.56% 306,292,557 32.80% 0.76 black
IIS Microsoft 262,471,886 28.95% 278,593,041 29.83% 0.88 pink
nginx NGINX, Inc. 141,443,630 15.60% 137,459,391 16.61% −0.88 inexperienced
GWS Google 20,799,087 2.29% 20,640,058 2.21% −0.08 blue

Apache, IIS and Nginx are essentially the most used net servers on the World Vast Internet.[9][10]

See additionally[edit]


  1. ^ Nancy J. Yeager; Robert E. McGrath (1996). Internet Server Expertise. ISBN 1-55860-376-X. Retrieved 22 January 2021.
  2. ^ Zolfagharifard, Ellie (24 November 2018). “Father of the web’ Sir Tim Berners-Lee on his plan to fight fake news”. The Telegraph. ISSN 0307-1235. Retrieved 1 February 2019.
  3. ^ “History of Computers and Computing, Internet, Birth, The World Wide Web of Tim Berners-Lee”. Retrieved 1 February 2019.
  4. ^ a b Macaulay, Tom. “What are the best open source web servers?”. ComputerworldUK. Retrieved 1 February 2019.
  5. ^ Fisher, Tim; Lifewire. “Getting a 502 Bad Gateway Error? Here’s What to Do”. Lifewire. Retrieved 1 February 2019.
  6. ^ “What is a 502 bad gateway and how do you fix it?”. IT PRO. Retrieved 1 February 2019.
  7. ^ Fisher, Tim; Lifewire. “Getting a 503 Service Unavailable Error? Here’s What to Do”. Lifewire. Retrieved 1 February 2019.
  8. ^ Fisher, Tim; Lifewire. “Getting a 504 Gateway Timeout Error? Here’s What to Do”. Lifewire. Retrieved 1 February 2019.
  9. ^ Vaughan-Nichols, Steven J. “Apache and IIS’ Web server rival NGINX is growing fast”. ZDNet. Retrieved 1 February 2019.
  10. ^ Hadi, Nahari (2011). Internet commerce safety: design and growth. Krutz, Ronald L. Indianapolis: Wiley Pub. ISBN 9781118098899. OCLC 757394142.

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