RFC 2068:Hypertext Transfer Protocol -- HTTP/1.1
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virtual host


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... proxies, caching, the need for persistent connections, and virtual hosts. In addition, the proliferation of incompletely-implemented applications calling themselves "HTTP/1.0" has necessitated a ...


... An origin server that does differentiate resources based on the host requested (sometimes referred to as virtual hosts or vanity hostnames) MUST use the following rules for determining the requested resource on an HTTP/1.1 ...



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