Virtual web hosting FAQ

How does APNIC evaluate assignments for virtual web hosting?

APNIC strongly encourages name-based web hosting. If you don't plan to provide name-based hosting, you must provide technical justification.

If you assign more than a /22 for IP-based web hosting, then the next time you request address space from APNIC, you will be required to list each of the IP addresses assigned for web hosting and their corresponding URLs.

The decision to encourage name-based web hosting and strongly discourage IP-based hosting is the result of a discussion paper and vote held during APRICOT 2000 in Seoul, Korea.

Top of page
What is virtual web hosting?

Virtual web hosting refers to the process of running multiple "virtual" web servers on a single physical host computer. Using this technique, a single computer can host thousands of independent web sites. Commercial web hosting service providers often use this technique to allow better manageability, efficiency and scalability of their service infrastructure.

Most virtual web hosting applications rely on virtual DNS resolution, so that a specific domain name (such as a customer's own registered domain name) may be associated with each independent virtual web server. This can be achieved through either name-based or IP-based virtual web hosting. These techniques are explained below.

Top of page
What is name-based web hosting?

Name-based web hosting is a technique that can be used when providing virtual web hosting services. Each web site that is hosted on a single machine shares a single public IP address. All HTTP GET requests received by this web server are answered according to the domain name supplied by the requesting client, enabling the web server to differentiate between multiple virtual sites on the one IP address.

Top of page
What is IP-based web hosting?

IP-based hosting is a technique that can be used when providing virtual web hosting services. Each web site that is hosted on a single machine is given its own separate public IP address. The HTTP GET requests are resolved by using the IP address instead of the name.

Operating system limitations may also limit the maximum number of IP addresses that can be assigned to a single machine, especially if separate log files are used.

Top of page
What is the 'Host:' header field?

The definition of a Host: header is taken from section 14.23 of RFC 2616

The Host request-header field specifies the Internet host and port number of the resource being requested, as obtained from the original URI given by the user or referring resource (generally an HTTP URL, as described in section 3.2.2). The Host field value MUST represent the naming authority of the origin server or gateway given by the original URL. This allows the origin server or gateway to differentiate between internally ambiguous URLs, such as the root "/" URL of a server for multiple host names on a single IP address).

Top of page
Under what circumstances is name-based web hosting possible?

Name-based web hosting is generally possible for web sites that do not have any special security requirements. For example, name-based hosting would be appropriate for personal web sites or servers that need to be accessible via more than one domain name.

Top of page
Under what circumstances is name-based web hosting not possible?

There are a few technical limitations to name-based hosting. The most common one is some websites requirements of using SSL (Secure Sockets Layer) for e-commerce services, particularly if a separate certificate is used for each virtual domain, and for anonymous login functionality with virtual FTP services.

Top of page
Can browsers that are only HTTP/1.0 compliant view websites that are hosted by a name-based virtual hosting system?

Browsers that are HTTP/1.0 compliant can view websites that are hosted by name if their version of the browser issues requests with an additional Host: header field. (This is a required header in HTTP/1.1, but all current HTTP/1.0 browsers also issue this header)

The justification of browsers not being HTTP1.0 compliant is not sufficient to warrant large scale IP-based hosting. Statistics collected by APNIC over a four month period show that almost all browsers visiting www.apnic.net provide the Host: header field (98.9% of HTTP1.0 and 99.8% HTTP1.1).