From: Charles Lindsey (chl@clw.cs.man.ac.uk)
Date: Tue May 04 1999 - 13:26:35 CDT
I think Section 2 is now relatively stable, except for a couple of
outstanding matters, so time for the next section, methinks.
This section deals with changes introduced by this document. BUT Please,
PLEASE do not let us discuss what changes there are to be at this stage.
That will happen as we go through the rest of the document, and then we
can come back and update this section. All we are looking at here is the
STYLE we shall use to introduce these changes.
3. Changes to the existing protocols
This document prescribes many changes, clarifications and new
features since the protocols described in [RFC 1036] and [RFC
1036BIS]. It is the intention that they can be assimilated into
Usenet as it presently operates without major interruption to the
service, though some of the new features may not begin to show
benefit until they become widely implemented. This sections
summarizes the main changes, and comments on some features of the
transition.
3.1. Principal Changes
o The [MESSFOR] conventions for parenthesis-enclosed comments in
headers are supported.
o Whitespace is permitted in Newsgroups headers, permitting
folding of such headers. Indeed, all news headers can now be
folded.
o An enhanced syntax for the Path header enables the injection
point of and the route taken by an article to be determined
with certainty.
o Netnews is firmly established as an 8bit medium.
o Large parts of MIME are recognised an an integral part of
Netnews.
o The charset for headers is always UTF-8. This will, inter alia,
permit newsgroup-names with non-ASCII characters.
o There is a new Control command 'mvgroup' to facilitate group
renaming.
o There are several new headers defined, such as Replaces and
Author-Ids, leading to increased functionality.
o There are numerous other small changes, clarifications and
enhancements.
[Doubtless many other changes should be listed, but there is little
point in doing so until our text is nearing completion. The above
gives the flavour of what should be said.]
3.2. Transitional Arrangements
An important distinction must be made between serving and relaying
agents which are responsible for the distribution and storage of
news articles, and user agents which are responsible for
interactions with users. It is important that the former should be
upgraded to conform to this document as soon as possible to provide
the benefit of the enhanced facilities. Fortunately, the number of
distinct implementations of such agents is rather small, at least
so far as the main "backbone" of Usenet is concerned, and many of
the new features are already supported. Contrariwise, there are a
great number of implementations of user agents, installed on a
vastly greater number of small sites. Therefore, the new
functionality has been designed so that existing agents may
continue to be used, although the full benefits may not be realised
until a substantial proportion of them have been upgraded.
In the list which follows, care has been taken to distinguish the
implications for both kinds of agent.
o [MESSFOR] style comments in headers do not affect serving and
relaying agents (note that the Newsgroups and Path headers do
not contain them). They are unlikely to hinder their proper
display in existing user agents except in the case of the
References header in agents which thread articles. Therefore,
it is provided that they SHOULD NOT be generated except where
permitted by the previous standards.
o Because of its importance to all serving agents, the extension
permitting whitespace and folding in Newsgroup headers SHOULD
NOT be used unless the user is willing to take the risk of
misprocessed articles. It is believed most existing
implementations handle it correctly, but this is not certain.
User agents are unaffected.
[That is Dan's replacement for my original 'Year 2000' text, after we
had a discussion about "flag days". It seems now a bit vague to me, so
maybe we need to discuss it further.]
o The new style of Path header is already consistent with the
previous standards. However, the intention is that relaying
agents should henceforth reject articles in the old style, and
so this should be offered as a configurable option for relaying
agents. User agents are unaffected.
[Should that "should" be a "SHOULD" or a "MAY". It is another ex-2000
case.]
o The vast majority of serving, relaying and transport agents are
believed to be already 8bit clean (in the slightly restricted
sense in which that term is used in the MIME standards). User
agents that do not implement MIME may be disadvantaged, but no
more so than at present when faced with 8bit characters (which
currently abound in spite of the previous standards).
o The introduction of MIME reflects a practice that is already
widespread. Articles in strict compliance with the previous
standards (using strict US-ASCII) will be unaffected. Many user
agents already support it, at least to the extent of widely
used charsets such as ISO8859-1. Users expecting to read
articles using the more exotic charsets will need to acquire
suitable reading agents. It is not intended, in general, that
any single user agent will be able to display every charset
known to IANA, but all such agents MUST support US-ASCII.
Serving and relaying agents are not affected.
o The use of the UTF-8 charset for headers will not affect any
existing usage, since US-ASCII is a strict subset of UTF-8.
Insofar as newsgroup names containing non-ASCII characters can
now be expected to arise, support from serving and relaying
agents will be necessary. It is believed that the customary
storage structure used by serving agents can already cope
(perhaps not ideally) with such names. Note that it is not
necessary for serving and relaying agents to understand all the
characters available in UTF-8, though it is desirable for them
to be displayable for diagnostic purposes via some escape
mechanism using, for example, the visible subset of US-ASCII.
For users expecting to use the more exotic charsets available
under UTF-8, the remarks already made in connection with MIME
will apply.
o The new Control: mvgroup command will need to be implemented in
serving agents. It SHOULD be used in conjunction with pairs of
matching rmgroup and newgroup commands (injected shortly after
the mvgroup) until such time as mvgroup is widely implemented.
The new Replaces header is also effectively a Control command,
and transitional arrangements are provided which should be used
in the meantime. User agents are unaffected.
o The headers newly introduced by this document can safely be
ignored by existing software, albeit with loss of the new
functionality.
[RFC 1036] M. Horton and R. Adams, "Standard for Interchange of
USENET Messages", RFC 1036, December 1987.
[MESSFOR] P. Resnick, "Internet Message Format Standard", draft-
ietf-drums-msg-fmt-07.txt, March 1998.
[RFC 1036BIS] Henry Spencer, "News article format and
transmission", [URL needed], June 1994.
-- Charles H. Lindsey ---------At Home, doing my own thing------------------------ Email: chl@clw.cs.man.ac.uk Web: http://www.cs.man.ac.uk/~chl Voice/Fax: +44 161 437 4506 Snail: 5 Clerewood Ave, CHEADLE, SK8 3JU, U.K. PGP: 2C15F1A9 Fingerprint: 73 6D C2 51 93 A0 01 E7 65 E8 64 7E 14 A4 AB A5