Shared web hosting service
From Wikipedia, the free encyclopedia
| Types of Internet hosting service |
|---|
|
A shared web hosting service or virtual hosting service is a form of web hosting service where more than one instance of the same web service is hosted on a single physical server. This is generally the most economical option for hosting as many people share the overall cost of server maintenance.
Contents |
[edit] Description
The hosting service must include system administration since it is shared by many users; this is a benefit for users that do not want to deal with it, but a hindrance to power users that want more control.
Shared hosting typically uses a web-based control panel system, such as cPanel, DirectAdmin, Plesk, Helm, H-sphere, Ensim, Sphera or one of many other control panel products. 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[1]. Web.com recently sued Godaddy as well for similar patent infringement [2].
In shared hosting, the provider is generally responsible for management of servers, installation of server software, security updates and other aspects of the service. Servers are often based on the Linux operating systems because more Control Panel products (see above) are made for Linux. However, some providers offer Microsoft Windows or FreeBSD based solutions. The Plesk control panel, for instance, has two versions - for Linux and Windows, both with very similar interfaces and functionality, with the exception of OS-specific differences (for example, supporting ASP.NET, or Microsoft SQL Server on Windows).
There are thousands of shared hosting providers in the United States alone. They range from mom-and-pop shops, to 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 advertising (PPC) 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.
[edit] Implementation
Shared web hosting can be accomplished in two ways: name-based and IP-based.
[edit] 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.
[edit] 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.
[edit] 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.
- 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.
- 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.
