Beth Frank: Question about Host

Andy Norman (ange@hplb.hpl.hp.com)
Fri, 29 Sep 1995 20:27:59 +0100 

[ This was meant for the list -- ange ]
------- Forwarded Message

Date:    Fri, 29 Sep 1995 12:02:57 -0500
From:    efrank@ncsa.uiuc.edu (Beth Frank)
To:      http-wg-request@cuckoo.hpl.hp.com
cc:      briand@ncsa.uiuc.edu
Subject: Question about Host

Roy said:
> 
> On the other hand, it seems that the WG has reached rough consensus
> on defining the 
> 
>     Host: fully.qualified.domain.name
> 
> as the method for telling the server what hostname is being accessed
> even when there are multiple hostnames per IP address.  It will be
> a required header on all HTTP/1.1 requests, and I encourage everyone
> to go out and implement it on HTTP/1.0 clients.  There are already
> three implementations that I know of, and I expect it to be in all
> the current browser releases by the end of the year.
> 
> Once a critical mass of clients have implemented Host, servers will
> be able to add the multihome features as well.
> 
> Happy camping,
> 
>  ....Roy T. Fielding  Department of ICS, University of California, Irvine USA
>                       Visiting Scholar, MIT/LCS + World-Wide Web Consortium
>                       (fielding@w3.org)                (fielding@ics.uci.edu)
> 

Support for Host: will be included in the next release of NCSA HTTPd (Release
1.5B6 which is not yet available).  Our current implementation mirrors that of
the virtual server (using multiple IP addresses).  We've talked with the client
people and they are open to supporting but we ran into a problem in the
implementation.

The clients often get URLs without fully quailified domain names.  They
do a DNS lookup and get an IP address.  If they then do an IP to name
lookup, for an IP address with multiple names, it's not clear what
they get back.  So what should they be putting in the Host: field?

	1) the non-fully qualified name (eg. sdg, instead of sdg.ncsa.uiuc.edu)
	2) or the IP address,
	3) or whatever is returned from the DNS name lookup of the IP address?

If we go with 2 or 3, we're no better off than before.
If we go with 1, a non-fully qualified address, that's more overhead for
	the server to recognize a non-fully qualified names.

We (server & client side) prefer 1.  That provides the most information, but
will make server processing harder.

The client people strongly oppose 3, because no additional information is
provided and you're making the client pay the penalty of 2 DNS lookups.

- -- 
		Elizabeth(Beth) Frank
		NCSA Server Development Team
		efrank@ncsa.uiuc.edu

------- End of Forwarded Message