[ietf-nntp] :bytes metadata

[Clive D.W. Feather]

Russ Allbery said:
>> It seems to me that the most likely use for :bytes is to reserve space
>> to hold a copy of the article. For that, it's more important not to have
>> too small a number than too big a one.
> The only thing that it's used for in practice so far as I know is
> killfiling and rough size estimates.  Do you have any reason to believe
> that it's used for anything more important than that?

You don't think it's used for space allocation, as I suggested?

> I think we're putting too much effort into something that clients don't
> actually care about.

Perhaps. It feels wrong to me to have these under-specified features, given
that we've made changes from historical practice (calling it ":bytes", for
example). But it looks like I'm alone on this.

If you don't mind, I'll add a few words about what existing implementations
do, then call it a day:

   Note to client implementers: some existing servers return a value
   different to that above. The commonest reasons for this are:
   
   o  counting a CRLF pair as one octet;
   
   o  including the "." character used for byte-stuffing in the number;
   
   o  including the terminating "." CRLF in the number;
   
   o  using one copy of an article for counting the octets but then
      returning another one that differs in some (permitted) manner.
   
   Implementations should be prepared for such variation (for example,
   if allocating space to store a copy of the article).
   
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