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Re: Rev81: COMMENT: 5.2 The Resource Identified by a Request

From: Roy T. Fielding <fielding@liege.ICS.UCI.EDU>
Date: Mon, 03 Jun 1996 02:42:49 -0700
To: jg@w3.org
Cc: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
Message-Id: <9606030242.aa07606@paris.ics.uci.edu>
> 19.5.1 Changes to Simplify Multi-homed Web Servers and Conserve IP Addresses
> 
> The requirements that clients and servers support the Host
> request-header, report an error if the Host request-header (section
> 14.23) is missing from an HTTP/1.1 request, and accept absolute URIs
> (section 5.1.2) are among the most important changes from HTTP/1.0.
> 
> In HTTP/1.0 there is a one-to-one relationship of IP addresses and
> servers. There is no other way to distinguish the intended server of a
> request than the IP address to which that request is directed. The
> HTTP/1.1 change will allow the Internet, once HTTP/1.0 clients and
> servers are no longer common, to support multiple Web sites from a
> single IP address, greatly simplifying large operational Web servers,
> where allocation of many IP addresses to a single host has created
> serious problems. The Internet will also be able to recover the IP
> addresses that have been used for the sole purpose of allowing
> root-level domain names to be used in HTTP URLs. Given the rate of
> growth of the Web, and the number of servers already deployed, it is
> extremely important that implementations of HTTP/1.1 correctly
> implement these requirements:

But this is wrong -- there is nothing in HTTP/1.0 that prevents the
solution from being implemented immediately, and we must not
discourage implementors from doing so.  We have already succeeded in
getting Host on at least 55% of requests (probably more like 65% now).
I intend to upgrade the old perl4 libwww-perl to support Host and a
few other things, but it won't be HTTP/1.1 (that part will be left for
the new libwww-perl-5.00).

I would like to rephrase these two paragraphs as follows:

  The requirements that clients and servers support the Host
  request-header, report an error if the Host request-header (section
  14.23) is missing from an HTTP/1.1 request, and accept absolute URIs
  (section 5.1.2) are among the most important changes defined by
  this specification.
 
  Older HTTP/1.0 clients assumed a one-to-one relationship of IP
  addresses and servers; there was no other established mechanism for
  distinguishing the intended server of a request than the IP address
  to which that request was directed. The changes outlined above will
  allow the Internet, once older HTTP clients are no longer common,
  to support multiple Web sites from a single IP address, greatly
  simplifying large operational Web servers, where allocation of many
  IP addresses to a single host has created serious problems.
  The Internet will also be able to recover the IP addresses that have
  been allocated for the sole purpose of allowing special-purpose domain names
  to be used in root-level HTTP URLs. Given the rate of growth of the Web,
  and the number of servers already deployed, it is extremely important
  that all implementations of HTTP (including updates to existing HTTP/1.0
  applications) correctly implement these requirements:


 ...Roy T. Fielding
    Department of Information & Computer Science    (fielding@ics.uci.edu)
    University of California, Irvine, CA 92717-3425    fax:+1(714)824-4056
    http://www.ics.uci.edu/~fielding/
Received on Monday, 3 June 1996 02:55:51 EDT

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