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Re: ID: Proxy autoconfig

From: nemo/Joel N. Weber II <devnull@gnu.ai.mit.edu>
Date: Fri, 28 Mar 1997 17:55:26 -0500 (EST)
Message-Id: <199703282255.RAA16274@duality.gnu.ai.mit.edu>
To: skwan@microsoft.com
Cc: http-wg@cuckoo.hpl.hp.com, josh@netscape.com
   From: Stuart Kwan <skwan@microsoft.com>
   Date: Fri, 28 Mar 1997 14:05:38 -0800

   1)  It is true that DHCP lease times can be "long-lived", i.e. on the
   order of weeks in some practical cases.  However this is only important
   if the URL that is delivered in the DHCP option changes, not the proxy
   information.  The proxy information is buried in the file referenced by
   the URL, and the client can reload the file at an arbitrary interval.
   As long as the server that is distributing the URL doesn't change often,
   you are ok.

Yes, and as I understand it, if you need to change that URL often,
you can use 1 hour lease times.

   2)  Using DNS will not work for mobile clients.  For example, consider a
   laptop named SKWAN01.INTRA.MICROSOFT.COM.  While plugged into the
   Microsoft corporate net, it queries for and receives the TXT RR:

	   w3-ns-pac.intra.microsoft.com. IN TXT
   "service:yp-http://proxy1.intra.microsoft.com:8080/proxy.ins"

   I unplug my laptop and take it on a visit to Netscape.  When I plug into
   the Netscape corporate network, I query for the TXT RR per above and the
   query fails.  At this point, I have no way of finding the proxy servers
   for that network, and automatic configuration fails.

I don't really follow this logic.

When you visit Netscape, I assume you'll get a different IP address.
I also assume that means you'll have a different hostname--maybe
visitor01.intra.netscape.com

   3)  It is true that DHCP is not necessarily widely available today, but
   if anything SRVLOC is less available.  The DHCP method at least gives
   you something you can use now.

It should be noted that albert.gnu.ai.mit.edu (the mail server that
processes all my incoming mail) had a version of named which couldn't
handle TXT records up until about a month ago.  So even that solution
is not really completely compatible with existing sites.

However, if you want to go the name server route, I wonder why you
couldn't make the URL something hardcoded like http://www-ns-pac/proxy.ins
That would mean that you have to use port 80 with a standardized path,
but that's less strange than the TXT or SRVRLOC records.
Received on Friday, 28 March 1997 14:57:10 EST

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