[ietf-nntp] :bytes metadata

[Clive D.W. Feather]

Russ Allbery said:
> One option is to not say that the :bytes metadata MUST be anything at all.
> In other words, we could just leave it at a SHOULD, with the implication
> that it's going to be somewhat unreliable in practice.
> 
> Unless we can reach consensus on a firm number, I think that's probably
> the best approach, and it's the one that most accurately reflects the
> current situation in deployed software.

What bothers me is, firstly that this makes the value almost useless to
clients, because they don't know what they can and can't assume about it,
and secondly that it's probably looser than current implementations
actually need. If we can't solve the first, what's the point?

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.

What I've currently got, *knowing* that it's insufficient, is:

    The :bytes metadata item for an article is a decimal integer.  It
    SHOULD equal the number of octets in the entire article - headers,
    body, and separating empty line (counting a CRLF pair as two octets,
    and not including either the "." CRLF terminating the response nor
    any "." added for "byte-stuffing" purposes).

Clients can allow for dot-stuffing by adding the value of :lines. They
can't allow for someone who counts CRLF as one octet, or for variations
between copies in a cluster, other than by guesswork.

How about:

    It MUST NOT vary from that figure by more than 999 plus the value
    of the :lines metadata item.

?

The parenthetical comment above shows some reasons for variation, and this
provides some reasonable room for servers without making it useless for
clients. In particular, counting CRLF as one octet, or including all the
stuffed dots, will fit within that limit, provided that the variation in
headers plus the number of header lines is no more than 999.

If any server can't keep within that limit, I suggest they need to rethink
their strategy.

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Clive D.W. Feather  | Work:  <clive at demon.net>   | Tel:    +44 20 8495 6138
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