A web hosting service is a type of Internet hosting service that allows individuals and organizations to provide their own website accessible via the World Wide Web. Web hosts are companies that provide space on a server they own for use by their clients as well as providing Internet connectivity, typically in a data center. Web hosts can also provide data center space and connectivity to the Internet for servers they do not own to be located in their data center, called colocation.
Service scope

The scopes of hosting services vary widely. The most basic is webpage and small-scale file hosting, where files can be uploaded via File Transfer Protocol (FTP) or a Web interface. The files are usually delivered to the Web "as is" or with little processing. Many Internet service providers (ISPs) offer this service free to their subscribers. People can also obtain Web page hosting from other, alternative service providers. Personal web site hosting is typically free, advertisement-sponsored, or cheap. Business web site hosting often has a higher expense.

Single page hosting is generally sufficient only for personal web pages. A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. PHP, Java, Ruby on Rails, and ASP.NET). These facilities allow the customers to write or install scripts for applications like forums and content management. For e-commerce, SSL is also required.

The host may also provide an interface or control panel for managing the Web server and installing scripts as well as other services like e-mail. Some hosts specialize in certain software or services (e.g. e-commerce). They are commonly used by larger companies to outsource network infrastructure to a hosting company. To find a web hosting company, there are searchable directories that can be used. One must be extremely careful when searching for a new company because many of the people promoting service providers are actually affiliates and the reviews are biased.

Hosting reliability and uptime

A common claim from the popular hosting providers is '99% or 99.9% server uptime' but this often refers only to a server being powered on and doesn't account for network downtime. Real downtime can potentially be larger than the percentage guaranteed by the provider. Many providers tie uptime, and accessibility, into their own service level agreement (SLA). SLAs may or may not include refunds, or reduced costs if performance goals are not met.

Types of hosting

Hosting services limited to the Web:

• Free web hosting service: is free, (sometimes) advertisement-supported web hosting, and is often limited when compared to paid hosting.
• Shared web hosting service: one's Web site is placed on the same server as many other sites, ranging from a few to hundreds or thousands. Typically, all domains may share a common pool of server resources, such as RAM and the CPU. A shared website may be hosted with a reseller.
• Reseller web hosting: allows clients to become web hosts themselves. Resellers could function, for individual domains, under any combination of these listed types of hosting, depending on who they are affiliated with as a provider. Resellers' accounts may vary tremendously in size: they may have their own virtual dedicated server to a colocated server.
• Virtual Dedicated Server: dividing a server into virtual servers, where each user feels like they're on their own dedicated server, but they're actually sharing a server with many other users. The users may have root access to their own virtual space. This is also known as a virtual private server or VPS.
• Dedicated hosting service: the user gets his or her own Web server and gains full control over it (root access for Linux/administrator access for Windows); however, the user typically does not own the server. Another type of Dedicated hosting is Self-Managed or Unmanaged. This is usually the least expensive for Dedicated plans. The user has full administrative access to the box, which means the client is responsible for the security and maintenance of his own dedicated box.
• Managed hosting service: the user gets his or her own Web server but is not allowed full control over it (root access for Linux/administrator access for Windows); however, they are allowed to manage their data via FTP or other remote management tools. The user is disallowed full control so that the provider can guarantee quality of service by not allowing the user to modify the server or potentially create configuration problems. The user typically does not own the server. The server is leased to the client.
• Colocation web hosting service: similar to the dedicated web hosting service, but the user owns the colo server; the hosting company provides physical space that the server takes up and takes care of the server. This is the most powerful and expensive type of the web hosting service. In most cases, the colocation provider may provide little to no support directly for their client's machine, providing only the electrical, Internet access, and storage facilities for the server. In most cases for colo, the client would have his own administrator visit the data center on site to do any hardware upgrades or changes.
• Clustered hosting: having multiple servers hosting the same content for better resource utilization. Clustered Servers are a perfect solution for high-availability dedicated hosting, or creating a scalable web hosting solution.
• Grid hosting : this form of distributed hosting is when a server cluster acts like a grid and is composed of multiple nodes.
• Home server: usually a single machine placed in a private residence can be used to host one or more websites from a usually consumer-grade broadband connection. These can be purpose-built machines or more commonly old PC's.

Some ISP's actively attempt to block these servers by disallowing incoming requests to TCP port 80 of the user's connection and by refusing to provide static IP addresses. A common way to attain a static IP is by creating an account with a dynamic DNS service. A dynamic DNS service will automatically change the IP address that a URL points to when it changes.

  Some specific types of hosting provided by web host service providers:

• File hosting service: hosts not web pages but files
• Image hosting service
• Video hosting service
• Blog hosting service
• One-click hosting
• Shopping cart software

Obtaining hosting

Web hosting is often provided as part of a general Internet access plan; there are many free and paid providers offering these services.

A customer needs to evaluate the requirements of the application to choose what kind of hosting to use. Such considerations include database server software, scripting software, and operating system. Most hosting providers provide Linux-based web hosting which offers a wide range of different software. A typical configuration for a Linux server is the LAMP platform: Linux, Apache, MySQL, and PHP/Perl/Python. The webhosting client may want to have other services, such as email for their business domain, databases or multi-media services for streaming media. A customer may also choose Windows for its hosting platform. The customer still can choose from PHP, Perl, and Python but may also use ASP .Net or Classic ASP.

Web hosting packages often include a Web Content Management System, so the end-user doesn't have to worry about the more technical aspects. These Web Content Management systems are great for the average user, but for those who want more control over their website design, this feature can sometimes be a nuisance rather than a feature.

One may also search the Internet to find active webhosting message boards that may provide feedback on what type of webhosting company may suit his/her needs.

A shared web hosting service or virtual hosting service refers to a web hosting service where many websites reside on one web server connected to the Internet. Each site "sits" on its own partition, or section/place on the server to keep it separate from other sites. This is generally the most economical option for hosting as many people share the overall cost of server maintenance.
Description

The hosting service must include system administration since it is shared by many users; this is a benefit for users who do not want to deal with it, but a hindrance to power users who want more control. In general shared hosting will be inappropriate for users who require extensive software development outside what the hosting provider supports. But on the other hand, shared hosting is cheaper than other types of hosting such as dedicated server hosting.

Shared hosting typically uses a web-based control panel system, such as cPanel, DirectAdmin, Plesk, InterWorx, Helm, H-sphere, Ensim, Sphera or one of many other control panel products. Most of the large hosting companies use their own custom developed control panel. Control panels and web interfaces have been causing some controversy lately as Web.com claims that it holds patent rights to the hosting technology with its 19 patents. Hostopia, a large wholesale host, recently purchased a license to use that technology from web.com for 10% of retail revenues. Web.com recently sued abtinfo.net as well for similar patent infringement.

In shared hosting, the provider is generally responsible for managing servers, installing server software, security updates, technical support, and other aspects of the service. Most servers are based on the Linux operating system and LAMP (software bundle), which is driven by the low cost of open source software. But some providers offer Microsoft Windows-based or FreeBSD-based solutions. For example, the Plesk and Ensim control panels are both available for two operating systems, Linux and Windows. Versions for either OS have very similar interfaces and functionality, with the exception of OS-specific differences (for example, ASP.NET or Microsoft SQL Server support under Windows, and typically greater security and stability under Linux).

There are thousands of shared hosting providers in the United States alone. They range from mom-and-pop shops and small design firms to multi-million-dollar providers with hundreds of thousands of customers. A large portion of the shared web hosting market is driven through pay per click (PPC) advertising or Affiliate programs.

Shared web hosting can also be done privately by sharing the cost of running a server in a colocation centre; this is called cooperative hosting.

Implementation

Shared web hosting can be accomplished in two ways: name-based and IP-based, although some control panels allow a mix of name-based and IP-based on the one server.

Name-based

In name-based virtual hosting, also called shared IP hosting, the virtual hosts serve multiple hostnames on a single machine with a single IP address.

When a web browser requests a resource from a web server using HTTP/1.1 it includes the requested hostname as part of the request. The server uses this information to determine which web site to show the user.

IP-based

In IP-based virtual hosting, also called dedicated IP hosting, each virtual host has a different IP address. The web server is configured with multiple physical network interfaces, or virtual network interfaces on the same physical interface. The web server software uses the IP address the client connects to in order to determine which web site to show the user. The primary reason for a site to use a dedicated IP is to be able to use its own SSL certificate rather than a shared certificate.

Disadvantages

Name-based virtual hosts have some disadvantages:

• They will not work with browsers that do not send the hostname as part of requests. This is true for older HTTP/1.0 browsers that have not retrofitted the host field feature from the HTTP/1.1 protocol. (The "Host" header that distinguishes between various DNS names sharing a single IP address was optional in HTTP/1.0; it is mandatory in HTTP/1.1, issued in 1999 as RFC 2616.)
• They do not properly support secure websites (HTTPS). All name-based virtual hosts using the same IP address must share the same digital certificate. This is because the SSL/TLS handshake takes place before the hostname is sent to the server. Thus the server doesn't know which encryption key to use when the connection is made. An extension to the TLS protocol, part of RFC 3546 - Transport Layer Security (TLS) Extensions, specifies a way for the client to provide the requested host name as part of the handshake, but it is not yet widely implemented. Some of the shared hosting providers require their customers to get Unique IP in order to properly set up HTTPS.
• If the Domain Name System is malfunctioning, it is harder to use a name-based virtually-hosted website. Ordinarily, in this case, the user could fall back to using the IP address to contact the system, as in http://127.0.0.1/ (invalid IP for example only). However, the web browser doesn't know what hostname to send to the server, but a name-based virtual host requires it. In this case, the default web host is sent back to the browser for that IP address.

A virtual private server (VPS, also referred to as Virtual Dedicated Server or VDS) is a method of partitioning a physical server computer into multiple servers such that each has the appearance and capabilities of running on its own dedicated machine. Each virtual server can run its own full-fledged operating system, and each server can be independently rebooted.

The practice of partitioning a single server so that it appears as multiple servers has long been common practice in mainframe computers, but has seen a resurgence lately with the development of virtualization software and technologies for other architectures.

Overview

There are two kinds of virtualizations: software based and hardware based. In a software based virtualization environment, the virtual machines share the same kernel and actually require the main node's resources. This kind of virtualization normally has many benefits in a web hosting environment because of quota incrementing and decrementing in real time with no need to restart the node. The main examples are Virtuozzo, HyperVM, Vserver, and OpenVZ which is the core kernel of both Virtuozzo and HyperVM.

In a hardware based virtualization, the virtualization mechanism partitions the real hardware resources. In typical implementations, no burst and/or realtime quota modification is possible; the limits are hard and can only be modified by restarting a virtual machine instance. This kind of environment is potentially more secure in the sense that it is less subject to "Quality of Service crosstalk" between VM instanceson the other hand, its security is typically dependent on the correctness of a larger and more complicated Trusted Computing Base. It is more commonly used in enterprise/commercial deployments^,Examples include Microsoft Virtual Server, VMware ESX Server, and Xen.

Uses

Virtual private servers bridge the gap between shared web hosting services and dedicated hosting services, giving independence from other customers of the VPS service in software terms but at less cost than a physical dedicated server. As a VPS runs its own copy of its operating system, customers have superuser-level access to that operating system instance, and can install almost any software that runs on the OS. Certain software does not run well in a virtualized environment, including firewalls, anti-virus clients, and indeed virtualizers themselves; some VPS providers place further restrictions, but they are generally lax compared to those in shared hosting environments. Due to the number of virtualization clients typically run on a single machine, a VPS generally has limited processor time, RAM, and disk space.

Due to their isolated nature, VPSes have become common sandboxes for possibly-insecure public services or update testing. For example, a single physical server might have two virtual private servers running: one hosting the production-level (live) website, and a second which houses a copy of it. When updates to crucial parts of software need to be made, they can be tested in the second VPS, allowing for detailed testing to be conducted without requiring several physical servers.

Virtual private servers are also sometimes employed as honeypots, allowing a machine to deliberately run software with known security flaws without endangering the rest of the server. Multiple honeypots can be quickly set up via VPSes in this fashion.

Virtual private server hosting

A growing number of companies offer virtual private server hosting, or virtual dedicated server hosting as an extension for Web hosting services. Some web hosting companies call a Virtual Private Server a Virtual Dedicated Server/Dynamic Dedicated Server or the other way around.

Managed Hosting

Tools are provided to monitor and control the virtual machine.

Unmanaged Hosting

Typically only minimal services are provided, such as ssh console and reboot. Unmanaged VPS hosting is generally less expensive than managed VPS hosting.

Unmetered Hosting

Similar to unmanaged hosting but a fixed bitrate is offered so that it is not possibile to exceed a monthly budget.

Virtualization software

For some of the software packages commonly used to provide virtualization, see comparison of virtual machines.