[ietf-nntp] Initial greeting 400 v 502

[Clive D.W. Feather]

If the server is not going to offer service, it MUST present a 400 or 502
and close the connection. The draft says:

    502 MUST be used  if the client is not permitted under any
    circumstances to interact with the server and 400 otherwise.

The intent was that 502 meant things like "you're not a customer" and 400
meant things like "limit on total simultaneous connections reached". But
what about "limit on connections from this IP address reached". 400 would
be the more sensible code for this.

However, says the poster, what if the limit is being tracked in an
authentication subsystem that is separate from the server and just returns
a yes/no answer? What response should be used then?

My inclination is to adjust the wording so that such a limit fits in 502.
That is, 400 means that a simple sleep-then-retry loop will, in principle,
eventually succeed while 502 means that something external to this link
must happen (either server configuration needs to change, or the client
needs to drive a third party - treating a second client-server link as such
a third party - to do something).

Anyone have a problem with that approach? If not, can anyone think of
better wording?

-- 
Clive D.W. Feather  | Work:  <clive at demon.net>   | Tel:    +44 20 8495 6138
Internet Expert     | Home:  <clive at davros.org>  | *** NOTE CHANGE ***
Demon Internet      | WWW: http://www.davros.org | Fax:    +44 870 051 9937
Thus plc            |                            | Mobile: +44 7973 377646