Re: No apologies if you receive this multiple times (was CFP: IEEE IC3N'2000)

Carnegie Mellon's legacy e-mail system has been eliminating duplicates
based on message-id alone (well, with recepient envelope address) for
many years (circa 1985?), and our new system, the Cyrus IMAP server,
also does it.  We never get any user complaints except when it doesn't
work.

The denial-of-service attack is interesting, and text should probably
be added to the relevant document that message-ids should be
reasonably unpredictable if it's not there already.

Larry

   From: Keith Moore <moore@cs.utk.edu>
   Date: Tue, 02 May 2000 12:33:52 -0400

   [end2endinterest removed...not on topic for that discussion]

   in general you don't want to do duplicate suppression based on
   message-id alone, because sometimes the same message-id really
   is used for significantly different messages  (sometimes due
   to software bugs, but if duplicate supression were widespread
   it would probably be a target of malice ... to keep someone from
   seeing a message, send them a different message using the same
   message-id).  some lists significantly modify messages without 
   modifying the message-id.  (and you probably don't want them
   to modify the message-id - it's what lets you trace a message 
   back to its source)

   you can use message-id to find potential duplicates, and then
   compare the messages themselves and use heuristics to determine
   whether they really are more-or-less the same.  or a user agent
   could remove extraneous information (e.g. received headers) from 
   every message it received, hash the result, and compare the hashes
   for duplicates.   I don't know of any user agent that does either 
   of these, and unless one gets lots of duplicate mail, it might
   not be worth the bother.

   mail delivery systems should probably not try to eliminate duplicates
   on behalf of their users. sometimes you actually want to know that
   you got a copy of the message that was sent through a list even if
   you already received a copy by other means.  so the user agent would
   need to do the duplicate suppression if it is to be done at all.

   I don't think we need to find a technical solution to every 
   social problem that exists with email.  the problem exists in other
   fields as well - people sometimes get more than one copy of the
   same mail-order catalog, for instance - and we don't lose too much
   sleep over it.  

   in general, the purpose of apologies are to avoid getting compliants
   from people who are naive enough to think that this is the sender's
   problem rather than the recipient's.

   Keith

Received on Tuesday, 2 May 2000 14:26:04 UTC