Subject: [dhcwg] Option code...252...WPAD?

From: "David W. Hankins" <[email-masked]>
Date: Thu, 24 Feb 2005 10:28:47 -0800

This may be old news.

Myself and our users have noticed that Windows XP SP2 has started to send
INFORMs at seemingly random intervals, with an options-request-list
including option #249 and option #252 amongst the usual standards-track
options.

There's no real problem here except that it retries several times,
incrementing the 'secs' field, indicating that it didn't get what it was
looking for.  This is more of a sysadmin irritation, and after the recent
WG activity regarding site-local option space, an area I've developed a
curiosity for.

Meanwhile regular REQUEST's contain an options-request-list that is the
same, minus option 252.  So it seems clear the INFORMs are actually for
252 specifically.  User experimentation (configuring an option 252)
confirms this - the Windows machines stop retransmitting INFORMs.

The madness revealed is draft-ietf-wrec-wpad-01.txt (now long since expired),
which claims in its section 4.4.1:

   The DHCP option code for WPAD is 252 by agreement of the DHC working 
   group chair.  This option is of type STRING.  This string contains a 
   URL which points to an appropriate config file.  The STRING is of 
   arbitrary size. 
   An example STRING value would be: 
   "http://server.domain/proxyconfig.pac" 

WPAD for those that don't know is Web Proxy Auto Discovery.

Which follows with the random intervals of the INFORMs - these could
be whenever Explorer is started (this could be an Explorer upgrade
rather than SP2).

I thought there might be something the WG should do about this...either
in documenting the option along the same lines as the rfc3942 work, or
else...?

-- 
David W. Hankins		"If you don't do it right the first time,
Software Engineer			you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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