Subject: RE: Issues relating to managing a mailing list...

From: John C Klensin <[email-masked]>
Date: Thu, 15 Mar 2012 14:15:41 -0400

--On Thursday, March 15, 2012 08:16 -0700 Ned Freed
<[email-masked]> wrote:

>...
>> > It might be okay for really large attachments, as long as
>> > only a few messages are affected.
> 
>> Borrowing a bit from Randy, the solution to really large
>> attachments is to ban them.  Personally, I'd find it perfectly
>> reasonable to have any message in the megabyte range or above
>> (or probably even an order of magnitude smaller) rejected
>> with a message that amounted to "if you have that much to
>> say, write an I-D, post it, and point to it".  That is much
>> more plausible today, when the mean time between I-D
>> submission and posting is measured in minutes (except during
>> blackout periods) than when it was in days.  During blackout
>> periods, the last thing the community needs is people adding
>> to already-overloaded lists by posting long documents in
>> email.
>...
> You begin by talking about "banning large attachments". You
> then segue into a discussion where you talk about a maximum
> size that includes the primary message content, not
> attachments, then you throw in disclaimers, which may or may
> not be attachments.
> 
> Other have followed up by supporting the limit on attachment
> size, others still have talked about banning attachments
> regardless of size.
> 
> Do you see the problem here? The minute you start focusing on
> specifics of message content, you're in a rathole. What counts
> as an attachment? (And yes, we have a precise definition for
> what constitutes an attachement, but following that definition
> gives people the ability to route around it.)

Ok, that is fair.  At best, I skipped being explicit about
several steps in my thinking. I personally see the attachment
issue as almost irrelevant, in part because of the "what
constitutes an attachment" issue you identify above.  In partial
defense, I was distracted a bit by comments from others about
"the first N bytes of a message" and "text and attachment"
models (which, as you know better than almost anyone, is a user
construct about how messages might be assembled but one that
doesn't necessarily map directly and usefully back from MIME
body parts).  

I think the issue is almost entirely about 

	(i) size, independent of how a message is structured, and
	
	(ii) what, in IMAP terms, is automatic synchronization
	into offline or disconnected mode.  More generally, it
	is ability to read and work with IETF mailing lists at a
	time when one has little or no connectivity.

>From that point of view, Russ's original question is about
something that is not only a bad idea but an ill-formed
proposition... at least unless we could agree on and enforce a
particular model of IETF participants assemble messages and send
them -- a goal that I believe is so hopeless as to not be worth
discussing.

> It follows that any limit needs to be on overall message size.
> (Even this is a little perilous because message sizes can
> change due to MIME downgrading or upgrading, both of which
> happen regularly.)

Exactly.   And that also identifies the other distraction I was
trying to get at.  In addition to MIME downgrading and
upgrading, the size of a message can be distorted by such things
as addition (possibly by submission servers or list exploders
and out of user control) of lengthy explanatory headers
(including some called for by IETF standards like DKIM), body
text (including the notorious "unless you agree to this
conditions, please un-read the message" announcements but all
list-added footers), or duplicate content (e.g., sending both
text/plain and text/html with multipart/alternative).  If we
were to start trying to split hairs on how to count message
sizes, I think we would rapidly go down a slightly different rat
hole.

>  I would not be opposed to imposing such a
> limit, although it's going to need to be higher than some
> people would probably like - it's surprising how easily you
> can approach 1Mb with a single part, plain text message
> containing nothing remotely resembling an "attachment".

Yes.  But an entirely anecdotal survey of recent postings to the
IETF list and comparison with Thomas Narten's statistics
indicates that a posting to that list of 50K in aggregate size
is well out on the upper tail.  Most messages of twice that size
and larger are either duplicate content or inclusion of a great
deal of content from multiple previous messages. I'd be happy
discouraging both of those patterns for other reasons so
wouldn't be upset if a size rule had the accidental side-effect
of pushing back on them.  I can well imagine the averages for
some WG lists being much larger, especially if editors are
including blocks of existing and proposed text for comment.
But, as a notorious author of long messages and someone who
often prefers consolidated responses to a lot of small messages,
I'd struggle to believe that messages over even a half-megabyte
are frequent or that, when they do occur, we wouldn't be better
off if they were broken into multiple messages (and probably
threads).  But all of that is about how we would discuss setting
a size, not whether limits on, or special handling of, messages
of a particular size or "attachment" structure is desirable.

     john

---

From: [email-masked]
Date: Thu, 15 Mar 2012 11:38:04 -0700 (PDT)

John, I agree completely with everything you say here.

				Ned