[NNTP] Re: MODE READER

Clive D.W. Feather clive at demon.net
Tue Nov 9 01:37:25 PST 2004


Russ Allbery said:
> Note that most servers have eliminated the need for MODE READER by
> ensuring that one of the following conditions is true:
[...]

Having worked through the MODE READER discussion, here's what I think is
the situation.

There are three classes of commands: "transit", "reader", and "general".
Of the core commands apart from MODE READER:
* IHAVE is transit
* HEAD, STAT, LIST ACTIVE, LIST EXTENSIONS are general
  (that's what the present text implies; I think at least QUIT needs
   to be added to that list)
* everything else is reader.

There are *four* possible types of connection. The connection type depends
on the server, the connecting IP, the connection port, and possibly the
phase of the moon :-)

(1) Full-functional. MODE READER is a no-op. The client can use any command
at any time (I'm ignoring authentication etc. for the moment).

(2) Reader-only. MODE READER is a no-op. The client can *not* use any
transit command (it gets 502), but can use all other commands at any time.

(3) Transit-only. MODE READER is a no-op. The client can *not* use any
reader command (it gets 502), but can use all other commands at any time.

(4) Switching. Initially reader commands cannot be used; they get a 401
response. Once MODE READER has been issued, transit commands cannot be
used; they get a 502 response. MODE READER destroys all server state apart
from the switch and therefore LIST EXTENSIONS output can change in this
one case.

Is this correct, in people's opinion?

If so, then why don't I revamp the description to express it like that?
MODE READER can then be rewritten in these terms, which I expect will be
far less confusing. LIST EXTENSIONS can indicate which of the four cases
applies (I would make (1) the default, with the others being READER_ONLY,
TRANSIT_ONLY, and MODE_READER). We'll need to decide which commands are
"transit" and which are "reader", but that won't hold up the rewrite.

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



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