ietf-nntp Section 8

[Clive D.W. Feather]

The present section 8 is formatted in a completely different way from other
commands. Instead of having an introduction, a description of responses,
and then some examples, each response gets its own section.

I proposed previously that this section be rewritten in the standard
format. I would like to re-iterate this proposal, and I attach new words
(which will also go on to my web site).

The present definition also says that if there are no extensions the server
MUST return 402 rather than an empty list. Is there any reason why the
latter should not be allowed (even if we still say SHOULD return 402) ?
I've adjusted the wording to permit this.

I've also made a couple of other minor edits.


  8. The CAPABILITIES DISCOVERY Step

  An NNTP client that wishes to use extensions to NNTP can query
  the server to determine which extensions are available. This
  is done with the LIST EXTENSIONS command.

  If a particular extension is unavailable, the client can
  attempt to work around it or it may wish to terminate the
  session.

  See section 12 for further discussion of extensions.


  8.1 LIST EXTENSIONS

  The LIST EXTENSIONS command allows a client to determine which
  extensions are supported by the server.

! An NNTP client supporting NNTP service extensions SHOULD query
! the server early in the session for extensions information by
! issuing the LIST EXTENSIONS command.

  This command MAY be issued at anytime during a session.  It is
  not required that the client issues this command before
  attempting to make use of any extension. The response
  generated by this command MAY change during a session because
! of other state information. However, an NNTP client MUST NOT
  cache (for use in another session) any information returned if
! the LIST EXTENSIONS command succeeds. That is, an NNTP client
  is only able to get the current and correct information
  concerning available extensions during a session by issuing a
  LIST EXTENSIONS command during that session and processing
  that response.
!
  A successful response starts with a 202 code and is followed
! by a list of extensions, one per line. Each line MUST
  begin with exactly one space followed by an extension-label
  and optionally one or more parameters (separated by single
  spaces). The extension-label and the meaning of the parameters
  are specified as part of the definition of the extension. The
  extension-label MUST be in uppercase.

  The server MUST NOT list the same extension twice in the
  response, and MUST list all supported extensions. The order in
  which the extensions are listed is not significant. The server
  need not even consistently return the same order.
!
! If the server does not support any extensions, it SHOULD return a 402
! failure response but MAY return an empty list instead.
!
!
! 8.1.1  Responses
!
! 202        extension list follows (multiline)
! 400        service about to terminate
! 402        no extensions available
! 502        [no meaning given]
! 503        unable to list extensions
!
! Following a 503 response an extension might still be available, and
! the client MAY attempt to use it.
!
! The LIST EXTENSIONS command is optional, and a server MAY issue a 500
! (unknown command) or 501 (syntax error) response to it.
!
!
! 8.1.2  LIST EXTENSION examples
!
! Example of a successful response:

          [C] LIST EXTENSIONS
          [S] 202 Extensions supported:
          [S]  OVER
          [S]  PAT
          [S]  LISTGROUP
          [S] .

  The particular extensions shown here are simply examples of
  what might be defined in other places, and no particular meaning
! should be attributed to them.

+ Example where no extensions are available, using preferred format:
+
+         [C] LIST EXTENSIONS
+         [S] 402 Server has no extensions
+
+ Example where no extensions are available, using an empty list:
+
+         [C] LIST EXTENSIONS
+         [S] 202 Extensions supported:
+         [S] .

-- 
Clive D.W. Feather  | Work:  <clive at demon.net>   | Tel:  +44 20 8371 1138
Internet Expert     | Home:  <clive at davros.org>  | Fax:  +44 20 8371 1037
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