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INTERNET-DRAFT Charles H. Lindsey
Usenet Format Working Group University of Manchester
February 2003
News Article Format
<draft-ietf-usefor-article-09.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This Draft is intended as a standards track document, obsoleting
RFC 1036, which itself dates from 1987.
This Standard defines the format of Netnews articles and specifies
the requirements to be met by software which originates, distributes,
stores and displays them.
Since the 1980s, Usenet has grown explosively, and many Internet and
non-Internet sites now participate. In addition, the Netnews
technology is now in widespread use for other purposes.
Backward compatibility has been a major goal of this endeavour, but
where this standard and earlier documents or practices conflict, this
standard should be followed. In most such cases, current practice is
already compatible with these changes.
[The use of the words "this standard" within this document when
referring to itself does not imply that this draft yet has pretensions
to be a standard, but rather indicates what will become the case if and
when it is accepted as an RFC with the status of a proposed or draft
standard.]
C. H. Lindsey [Page 1]
News Article Format February 2003
[Remarks enclosed in square brackets and aligned with the left margin,
such as this one, are not part of this draft, but are editorial notes to
explain matters amongst ourselves, or to point out alternatives, or to
assist the RFC Editor.]
[In this draft, references to [NNTP] are to be replaced by [RFC 977], or
else by references to the RFC arising from the series of drafts draft-
ietf-nntpext-base-*.txt, in the event that such RFC has been accepted at
the time this document is published. Likewise, if may be possible to
replace references to [RFC 2279] by references to [RFC 2279bis].]
[Please note that this Draft is subject to change as regards the extent
to which the charset UTF-8 is to be used in headers, or even whether it
is used at all. It is published at this time to give a snapshot of the
current state of the project.
It is also intended to split it into two documents, one the standard
proper and the other an informational document setting out best current
practice.]
Table of Contents
1. Introduction .................................................. 6
1.1. Basic Concepts ............................................ 6
1.2. Objectives ................................................ 7
1.3. Historical Outline ........................................ 7
1.4. Transport ................................................. 7
2. Definitions, Notations and Conventions ........................ 8
2.1. Definitions ............................................... 8
2.2. Textual Notations ......................................... 9
2.3. Relation To Email and MIME ................................ 11
2.4. Syntax .................................................... 11
2.4.1. Syntax Notation ....................................... 11
2.4.2. Syntax adapted from Email and MIME .................... 11
2.4.3. Syntax copied from other standards .................... 13
2.5. Language .................................................. 14
3. Changes to the existing protocols ............................. 15
3.1. Principal Changes ......................................... 15
3.2. Transitional Arrangements ................................. 15
4. Basic Format .................................................. 17
4.1. Syntax of News Articles ................................... 17
4.2. Headers ................................................... 18
4.2.1. Naming of Headers ..................................... 18
4.2.2. MIME-style Parameters ................................. 19
4.2.3. White Space and Continuations ......................... 20
4.2.4. Comments .............................................. 21
4.2.5. Header Properties ..................................... 22
4.2.5.1. Experimental Headers .............................. 22
4.2.5.2. Inheritable Headers ............................... 22
4.2.5.3. Variant Headers ................................... 23
4.2.6. Undesirable Headers ................................... 23
4.3. Body ...................................................... 23
4.3.1. Body Format Issues .................................... 23
4.3.2. Body Conventions ...................................... 24
C. H. Lindsey [Page 2]
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4.4. Characters and Character Sets ............................. 26
4.4.1. Character Sets within Article Headers ................. 26
4.4.2. Character Sets within Article Bodies .................. 29
4.4.3. The NEWS-8BIT-HEADERS IMAP Extension .................. 29
4.5. Size Limits ............................................... 30
4.6. Example ................................................... 31
5. Mandatory Headers ............................................. 32
5.1. Date ...................................................... 32
5.1.1. Examples .............................................. 33
5.2. From ...................................................... 33
5.2.1. Examples: ............................................ 34
5.3. Message-ID ................................................ 34
5.4. Subject ................................................... 35
5.4.1. Examples .............................................. 36
5.5. Newsgroups ................................................ 36
5.5.1. Forbidden newsgroup-names ............................. 41
5.5.2. Encoded newsgroup-names ............................... 41
5.6. Path ...................................................... 42
5.6.1. Format ................................................ 42
5.6.2. Adding a path-identity to the Path-header ............. 43
5.6.3. The tail-entry ........................................ 44
5.6.4. Path-Delimiter Summary ................................ 45
5.6.5. Suggested Verification Methods ........................ 46
5.6.6. Example ............................................... 46
6. Optional Headers .............................................. 47
6.1. Reply-To .................................................. 47
6.1.1. Examples .............................................. 47
6.2. Sender .................................................... 48
6.3. Organization .............................................. 48
6.4. Keywords .................................................. 48
6.5. Summary ................................................... 48
6.6. Distribution .............................................. 49
6.7. Followup-To ............................................... 50
6.8. Mail-Copies-To ............................................ 50
6.9. Posted-And-Mailed ......................................... 52
6.10. References ............................................... 52
6.10.1. Examples ............................................. 53
6.11. Expires .................................................. 53
6.12. Archive .................................................. 53
6.13. Control .................................................. 54
6.14. Approved ................................................. 55
6.15. Supersedes ............................................... 55
6.16. Xref ..................................................... 56
6.17. Lines .................................................... 57
6.18. User-Agent ............................................... 57
6.18.1. Examples ............................................. 58
6.19. Injector-Info ............................................ 58
6.19.1. Usage of Injector-Info-parameters .................... 60
6.19.1.1. The posting-host-parameter ....................... 61
6.19.1.2. The posting-account-parameter .................... 61
6.19.1.3. The posting-sender-parameter ..................... 61
6.19.1.4. The posting-logging-parameter .................... 61
6.19.1.5. The posting-date-parameter ....................... 62
6.19.2. Example .............................................. 62
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6.20. Complaints-To ............................................ 62
6.21. MIME headers ............................................. 62
6.21.1. Syntax ............................................... 62
6.21.2. Content-Type ......................................... 63
6.21.2.1. Message/partial .................................. 64
6.21.2.2. Message/rfc822 ................................... 64
6.21.2.3. Message/external-body ............................ 65
6.21.2.4. Multipart types .................................. 65
6.21.3. Content-Transfer-Encoding ............................ 65
6.21.4. Character Sets ....................................... 67
6.21.5. Content Disposition .................................. 67
6.21.6. Definition of some new Content-Types ................. 67
6.21.6.1. Application/news-transmission .................... 67
6.21.6.2. Message/news obsoleted ........................... 68
6.22. Obsolete Headers ......................................... 69
7. Control Messages .............................................. 69
7.1. Digital Signature of Headers .............................. 69
7.2. Group Control Messages .................................... 70
7.2.1. The 'newgroup' Control Message ........................ 70
7.2.1.1. The Body of the 'newgroup' Control Message ........ 71
7.2.1.2. Application/news-groupinfo ........................ 71
7.2.1.3. Initial Articles .................................. 73
7.2.1.4. Example ........................................... 73
7.2.2. The 'rmgroup' Control Message ......................... 74
7.2.2.1. Example ........................................... 74
7.2.3. The 'mvgroup' Control Message ......................... 75
7.2.3.1. Example ........................................... 76
7.2.4. The 'checkgroups' Control Message ..................... 77
7.2.4.1. Application/news-checkgroups ...................... 78
7.3. Cancel .................................................... 79
7.4. Ihave, sendme ............................................. 80
7.5. Obsolete control messages. ............................... 81
8. Duties of Various Agents ...................................... 81
8.1. General principles to be followed ......................... 81
8.2. Duties of an Injecting Agent .............................. 82
8.2.1. Proto-articles ........................................ 82
8.2.2. Procedure to be followed by Injecting Agents .......... 83
8.3. Duties of a Relaying Agent ................................ 85
8.4. Duties of a Serving Agent ................................. 86
8.5. Duties of a Posting Agent ................................. 87
8.6. Duties of a Followup Agent ................................ 87
8.7. Duties of a Moderator ..................................... 88
8.8. Duties of a Gateway ....................................... 90
8.8.1. Duties of an Outgoing Gateway ......................... 91
8.8.1.1. Gatewaying into email ............................. 91
8.8.2. Duties of an Incoming Gateway ......................... 93
8.8.3. Example ............................................... 95
9. Security and Related Considerations ........................... 96
9.1. Leakage ................................................... 96
9.2. Attacks ................................................... 96
9.2.1. Denial of Service ..................................... 96
9.2.2. Compromise of System Integrity ........................ 97
9.3. Liability ................................................. 99
10. IANA Considerations .......................................... 99
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11. References ................................................... 99
12. Acknowledgements ............................................. 102
13. Contact Address .............................................. 103
Appendix A.1 - A-News Article Format .............................. 103
Appendix A.2 - Early B-News Article Format ........................ 104
Appendix A.3 - Obsolete Headers ................................... 105
Appendix A.4 - Obsolete Control Messages .......................... 105
Appendix B - Collected Syntax ..................................... 106
Appendix B.1 - Characters, Atoms and Folding ...................... 106
Appendix B.2 - Basic Forms ........................................ 108
Appendix B.3 - Headers ............................................ 109
Appendix B.3.1 - Header outlines .................................. 109
Appendix B.3.2 - Control-message outlines ......................... 111
Appendix B.3.3 - Other header rules ............................... 112
Appendix C - Notices .............................................. 114
C. H. Lindsey [Page 5]
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1. Introduction
1.1. Basic Concepts
"Netnews" is a set of protocols for generating, storing and
retrieving news "articles" (which resemble email messages) and for
exchanging them amongst a readership which is potentially widely
distributed. It is organized around "newsgroups", with the
expectation that each reader will be able to see all articles posted
to each newsgroup in which he participates. These protocols most
commonly use a flooding algorithm which propagates copies throughout
a network of participating servers. Typically, only one copy is
stored per server, and each server makes it available on demand to
readers able to access that server.
An important characteristic of Netnews is the lack of any requirement
for a central administration or for the establishment of any
controlling host to manage the network. A network which limits
participation to some restricted set of hosts (within some company,
for example) is a "closed" network; otherwise it is an "open"
network. A set of hosts within a network which, by mutual
arrangement, operates some variant (whether more or less restrictive)
of the Netnews protocols is a "cooperating subnet".
"Usenet" is a particular worldwide open network based upon the
Netnews protocols, with the newsgroups being organized into
recognized "hierarchies". Anybody can join (it is simply necessary
to negotiate an exchange of articles with one or more other
participating hosts). Usenet "belongs" to those who administer the
hosts of which it is comprised. There is no Cabal with overall
authority to direct what is to be be allowed. Nevertheless, there do
exist agencies within Usenet that have authority to establish
policies and to perform administrative functions, but such authority
derives solely from the consent of those sites which choose to
recognize it (and who can decline to exchange articles with sites
which choose not to recognize it). Usually, the authority of such an
agency is restricted to a particular hierarchy, or group of
hierarchies.
A "policy" is a rule intended to facilitate the smooth operation of a
network by establishing parameters which restrict behaviour that,
whilst technically unexceptionable, would nevertheless contravene
some accepted standard of "Good Netkeeping". Since the ultimate
beneficiaries of a network are its human readers, who will be less
tolerant of poorly designed interfaces than mere computers, articles
in breach of established policy can cause considerable annoyance to
their recipients.
Policies may well vary from network to network, from hierarchy to
hierarchy within one network, and even between individual newsgroups
within one hierarchy. It is assumed, for the purposes of this
standard, that agencies with varying degrees of authority to
establish such policies will exist, and that where they do not,
policy will be established by mutual agreement. For the benefit of
C. H. Lindsey [Page 6]
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networks and hierarchies without such established agencies, and to
provide a basis upon which all agencies can build, this present
standard often provides default policy parameters, usually
introducing them by a phrase such as "As a matter of policy ...".
1.2. Objectives
The purpose of this present standard is to define the format of
articles and the protocols to be used for Netnews in general, and for
Usenet in particular, and to set standards to be followed by software
that implements those protocols.
It is NOT the purpose of this standard to define how the authority of
various agencies to exercise control or oversight of the various
parts of Usenet is established (that is itself a matter of policy).
Nevertheless, it is assumed that such authorities will exist, and
tools are provided within the protocols for their use.
1.3. Historical Outline
Network news originated as the medium of communication for Usenet,
circa 1980. Since then, Usenet has grown explosively, and many
Internet and non-Internet sites participate in it. In addition, the
news technology is now in widespread use for other purposes, on the
Internet and elsewhere.
The earliest news interchange used the so-called "A News" article
format. Shortly thereafter, an article format vaguely resembling
Internet Mail was devised and used briefly. Both of those formats
are completely obsolete; they are documented in Appendix A.1 and
Appendix A.2 for historical reasons only. With publication of [RFC
850] in 1983, news articles came to closely resemble Internet Mail
messages, with some restrictions and some additional headers. [RFC
1036] in 1987 updated [RFC 850] without making major changes.
A Draft popularly referred to as "Son of 1036" [Son-of-1036] was
written in 1994 by Henry Spencer. That document formed the original
basis for this standard, and its author has endorsed this standard as
its successor. Much is taken directly from Son of 1036, and it is
hoped that we have followed its spirit and intentions. It is
anticipated that [Son-of-1036] will be published as an Historic RFC,
in a suitably relabelled form, following the publication of this
standard.
1.4. Transport
As in this standard's predecessors, the exact means used to transmit
articles from one host to another is not specified. NNTP [NNTP] is
the most common transmission method on the Internet, but much
transmission takes place entirely independent of the Internet. Other
methods in use include the UUCP protocol [RFC 976] extensively used
in the early days of Usenet, FTP, downloading via satellite, tape
archives, and physically delivered magnetic and optical media.
C. H. Lindsey [Page 7]
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2. Definitions, Notations and Conventions
2.1. Definitions
An "article" is the unit of news, analogous to an [RFC 2822]
"message". A "proto-article" is one that has not yet been injected
into the news system.
A "message identifier" (5.3) is a unique identifier for an article,
usually supplied by the "posting agent" which posted it or, failing
that, by the "injecting agent". It distinguishes the article from
every other article ever posted anywhere. Articles with the same
message identifier are treated as if they are the same article
regardless of any differences in the body or headers.
A "newsgroup" is a single news forum, a logical bulletin board,
having a name and nominally intended for articles on a specific
topic. An article is "posted to" a single newsgroup or several
newsgroups. When an article is posted to more than one newsgroup, it
is said to be "crossposted"; note that this differs from posting the
same text as part of each of several articles, one per newsgroup.
A newsgroup may be "moderated", in which case submissions are not
posted directly, but mailed to a "moderator" for consideration and
possible posting. Moderators are typically human but may be
implemented partially or entirely in software.
A "hierarchy" is the set of all newsgroups whose names share a first
component (as defined in 5.5). The term "sub-hierarchy" is also used
where several initial components are shared.
A "poster" is the person or software that composes and submits a
possibly compliant article to a "posting agent". The poster is
analogous to [RFC 2822]'s author(s).
A "posting agent" is the software that assists posters to prepare
proto-articles, in compliance with this standard. The proto-article
is then passed on to an "injecting agent" for final checking and
injection into the news stream. If the article is not compliant, or
is rejected by the injecting agent, then the posting agent informs
the poster with an explanation of the error.
A "reader" is the person or software reading news articles.
A "reading agent" is software which presents articles to a reader.
A "followup" is an article containing a response to the contents of
an earlier article (the followup's "precursor").
A "followup agent" is a combination of reading agent and posting
agent that aids in the preparation and posting of a followup.
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An (email) "address" is the mailbox [RFC 2822] (or more particularly
the addr-spec within that mailbox) which directs the delivery of an
email to its intended recipient, who is said to "own" that address.
An article's "reply address" is the address to which mailed replies
should be sent. This is the address specified in the article's From-
header (5.2), unless it also has a Reply-To-header (6.1).
A "sender" is the person or software (usually, but not always, the
same as the poster) responsible for the operation of the posting
agent or, which amounts to the same thing, for passing the article to
the injecting agent. The sender is analogous to [RFC 2822]'s sender.
An "injecting agent" takes the finished article from the posting
agent (often via the NNTP "post" command) performs some final checks
and passes it on to a relaying agent for general distribution.
A "relaying agent" is software which receives allegedly compliant
articles from injecting agents and/or other relaying agents, and
possibly passes copies on to other relaying agents and serving
agents.
A "news database" is the set of articles and related structural
information stored by a serving agent and made available for access
by reading agents.
A "serving agent" receives an article from a relaying agent and files
it in a news database. It also provides an interface for reading
agents to access the news database.
A "control message" is an article which is marked as containing
control information; a relaying or serving agent receiving such an
article may (subject to the policies observed at that site) take
actions beyond just filing and passing on the article.
A "gateway" is software which receives news articles and converts
them to messages of some other kind (e.g. mail to a mailing list), or
vice versa; in essence it is a translating relaying agent that
straddles boundaries between different methods of message exchange.
The most common type of gateway connects newsgroup(s) to mailing
list(s), either unidirectionally or bidirectionally, but there are
also gateways between news networks using this standard's news format
and those using other formats.
2.2. Textual Notations
This standard contains explanatory NOTEs using the following format.
These may be skipped by persons interested solely in the content of
the specification. The purpose of the notes is to explain why choices
were made, to place them in context, or to suggest possible
implementation techniques.
C. H. Lindsey [Page 9]
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NOTE: While such explanatory notes may seem superfluous in
principle, they often help the less-than-omniscient reader grasp
the purpose of the specification and the constraints involved.
Given the limitations of natural language for descriptive
purposes, this improves the probability that implementors and
users will understand the true intent of the specification in
cases where the wording is not entirely clear.
"US-ASCII" is short for "the ANSI X3.4 character set" [ANSI X3.4].
While "ASCII" is often misused to refer to various character sets
somewhat similar to X3.4, in this standard "US-ASCII" is used to mean
X3.4 and only X3.4. US-ASCII is a 7 bit character set. Please note
that this standard requires that all agents be 8 bit clean; that is,
they must accept and transmit data without changing or omitting the
8th bit.
Certain words, when capitalized, are used to define the significance
of individual requirements. The key words "MUST", "REQUIRED",
"SHOULD", "RECOMMENDED", "MAY" and "OPTIONAL", and any of those words
associated with the word "NOT", are to be interpreted as described in
[RFC 2119].
In addition, the word "Ought", when applied to a poster, or to
actions of posting and similar agents which a poster may easily
override, indicates a recommendation whose violation would do no more
than breach established policy, or accepted best practice.
NOTE: The use of "MUST" or "SHOULD" implies a requirement that
would or could lead to interoperability problems if not
followed. Although not following an "Ought" recommendation might
do no worse than cause extreme irritation to other readers,
particularly in the case of the publicly distributed Usenet,
that is no reason not to take it seriously. The essential
distinction is that enforcement of a "MUST" or "SHOULD" is a
matter of ensuring correct implementation, whereas enforcement
of an "Ought" is more a matter of sensible design or of social
pressure (whose effectiveness should not be underestimated, even
though it cannot be prescribed by this standard).
NOTE: A requirement imposed on a relaying or serving agent
regarding some particular article should be understood as
applying only if that article is actually accepted for
processing (since any agent may always reject any article
entirely, for reasons of site policy).
Wherever the context permits, use of the masculine includes the
feminine and use of the singular includes the plural, and vice versa.
Throughout this standard we will give examples of various
definitions, headers and other specifications. It needs to be
remembered that these samples are for the aid of the reader only and
do NOT define any specification themselves. In order to prevent
possible conflict with "Real World" entities and people the top level
domain ".example" is used in all sample domains and addresses. The
C. H. Lindsey [Page 10]
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hierarchy "example.*" is also used as a sample hierarchy.
Information on the ".example" top level domain is in [RFC 2606].
2.3. Relation To Email and MIME
The primary intent of this standard is to describe the news article
format. Insofar as news articles are a subset of the email message
format augmented by some new headers, this standard incorporates many
(though not all) of the provisions of [RFC 2822], with the aim of
enabling news articles to pass through email systems and vice versa,
provided only that they contain the minimum headers required for the
mode of transport being used. Unfortunately, the match is not
perfect, but it is the intention of this standard that gateways
between Email and Netnews should be able to operate with the minimum
of tinkering.
Likewise, this standard incorporates many (though not all) of the
provisions of the MIME standards [RFC 2045] et seq which, though
designed with Email in mind, are mostly applicable to Netnews.
2.4. Syntax
The complete syntax defined in this standard is repeated, for
convenience, in Appendix B.
2.4.1. Syntax Notation
This standard uses the Augmented Backus Naur Form described in [RFC
2234].
In particular, it makes significant use of the "incremental
alternative" feature of that notation. For example, the two rules
header = other-header
header =/ Date-header
are equivalent to the single rule
header = other-header / Date-header
2.4.2. Syntax adapted from Email and MIME
Much of the syntax of Netnews Articles is based on the corresponding
syntax defined in [RFC 2822] or in the MIME specifications [RFC 2045]
et seq, which are deemed to have been incorporated into this standard
as required. However, there are some important differences arising
from the fact that [RFC 2822] does not recognize anything beyond US-
ASCII characters, that it does not recognize the MIME headers [RFC
2045], and that it includes much syntax described as "obsolete"
(which is excluded from this standard, as detailed below).
NOTE: Netnews parsers historically have been much less
permissive than Email parsers, and this is reflected in the
modifications referred to, and in some further specific rules.
C. H. Lindsey [Page 11]
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The following syntactic rules therefore supersede the corresponding
rules given in [RFC 2822] and [RFC 2045], thus allowing UTF-8
characters [RFC 2279] to appear in certain contexts (the five rules
beginning with "strict-" reflect the corresponding original rules
from [RFC 2822]).
UTF8-2 = %xC2-DF UTF8-tail
UTF8-3 = %xE0 %xA0-BF UTF8-tail / %xE1-EC 2(UTF8-tail) /
%xED %x80-9F UTF8-tail / %xEE-EF 2(UTF8-tail)
UTF8-4 = %xF0 %x90-BF 2(UTF8-tail) / %xF1-F7 3(UTF8-tail)
UTF8-5 = %xF8 %x88-BF 3(UTF8-tail) / %xF9-FB 4(UTF8-tail)
UTF8-6 = %xFC %x84-BF 4(UTF8-tail) / %xFD 5(UTF8-tail)
UTF8-tail = %x80-BF
UTF8-xtra-char = UTF8-2 / UTF8-3 / UTF8-4 / UTF8-5 / UTF8-6
text = %d1-9 / ; all UTF-8 characters except
%d11-12 / ; US-ASCII NUL, CR and LF
%d14-127 /
UTF8-xtra-char
ctext = NO-WS-CTL / ; all of <text> except
%d33-39 / ; SP, HTAB, "(", ")"
%d42-91 / ; "\" and DEL
%d93-126 /
UTF8-xtra-char
qtext = NO-WS-CTL / ; all of <text> except
%d33 / ; SP, HTAB, "\" DQUOTE
%d35-91 / ; and DEL
%d93-126 /
UTF8-xtra-char
utext = NO-WS-CTL / ; Non white space controls
%d33-126 / ; The rest of UTF-8
UTF8-xtra-char
strict-text = %d1-9 / ; text restricted to
%d11-12 / ; US-ASCII
%d14-127
strict-qtext = NO-WS-CTL / ; qtext restricted to
%d33 / ; US-ASCII
%d35-91 /
%d93-126
strict-quoted-pair
= "\" strict-text
strict-qcontent = strict-qtext / strict-quoted-pair
strict-quoted-string
= [CFWS] DQUOTE
*( [FWS] strict-qcontent ) [FWS]
DQUOTE [CFWS]
unstructured = 1*( [FWS] utext ) [FWS]
The syntax for UTF8-xtra-char excludes those redundant sequences of
octets which cannot occur in UTF-8, as defined by [RFC 2279], either
because they would not be the shortest possible encodings of some UCS
character [ISO/IEC 10646], or they would represent one of the
characters D800 through DFFF, disallowed in UCS because of their
surrogate use in the UTF-16 encoding. These sequences MUST NOT be
generated by posting agents. Where they occur inadvertently, they
C. H. Lindsey [Page 12]
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SHOULD be passed on untouched by other agents, but attempts to
interpret them as malformed UTF-8 MUST NOT be made. However, if there
is reason to suppose they are representations of some other character
set they MAY, as suggested in section 4.4.1, be interpreted as such.
The syntax also includes, for completeness, the cases UTF8-5 and
UTF8-6 which cannot, in fact, arise in [UNICODE 3.2] (though they
might conceivably arise in some future extension).
Observe, in contradistinction to [RFC 2822], that an unstructured
header MUST contain at least one non-whitespace character (see also
remarks about empty headers in 4.2.6).
Wherever in this standard the syntax is stated to be taken from [RFC
2822], it is to be understood as the syntax defined by [RFC 2822]
after making the above changes, but NOT including any syntax defined
in section 4 ("Obsolete syntax") of [RFC 2822]. Software compliant
with this standard MUST NOT generate any of the syntactic forms
defined in that Obsolete Syntax, although it MAY accept such
syntactic forms. Certain syntax from the MIME specifications [RFC
2045] et seq is also considered a part of this standard (see 6.21).
2.4.3. Syntax copied from other standards
The following syntactic forms, taken from [RFC 2234] or from [RFC
2822], are repeated here for convenience only:
ALPHA = %x41-5A / ; A-Z
%x61-7A ; a-z
CR = %x0D ; carriage return
CRLF = CR LF
DIGIT = %x30-39 ; 0-9
HTAB = %x09 ; horizontal tab
LF = %x0A ; line feed
SP = %x20 ; space
NO-WS-CTL = %d1-8 / ; US-ASCII control characters
%d11 / ; which do not include the
%d12 / ; carriage return, line feed,
%d14-31 / ; and whitespace characters
%d127
specials = "(" / ")" / ; Special characters used in
"<" / ">" / ; other parts of the syntax
"[" / "]" /
":" / ";" /
"@" / "\" /
"," / "." /
DQUOTE
WSP = SP / HTAB ; whitespace characters
FWS = ([*WSP CRLF] 1*WSP); folding whitespace
ccontent = ctext / quoted-pair / comment
comment = "(" *([FWS] ccontent) [FWS] ")"
CFWS = *([FWS] comment) ( ([FWS] comment) / FWS )
DQUOTE = %d34 ; quote mark
quoted-pair = "\" text
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atext = ALPHA / DIGIT /
"!" / "#" / ; Any US-ASCII character except
"$" / "%" / ; controls, SP, and specials.
"&" / "'" / ; Used for atoms
"*" / "+" /
"-" / "/" /
"=" / "?" /
"^" / "_" /
"`" / "{" /
"|" / "}" /
"~"
atom = [CFWS] 1*atext [CFWS]
dot-atom = [CFWS] dot-atom-text [CFWS]
dot-atom-text = 1*atext *( "." 1*atext )
qcontent = qtext / quoted-pair
quoted-string = [CFWS] DQUOTE
*( [FWS] qcontent ) [FWS]
DQUOTE [CFWS]
word = atom / quoted-string
phrase = 1*word
NOTE: Following [RFC 2234], literal text included in the syntax
is to be regarded as case-insensitive. However, in
contradistinction to [RFC 2822], the Netnews protocols are
sensitive to case in some instances (as in newsgroup-names, some
header parameters, etc.). Care has been taken to indicate this
explicitly where required.
As in [RFC 2822], where any quoted-pair appears it is to be
interpreted as its text character alone. That is to say, the "\"
character that appears as part of a quoted-pair is semantically
"invisible".
Again, as in [RFC 2822], strings of characters that include
characters not syntactically allowed in some particular context may
be incorporated into a quoted-string by "encapsulating" them between
quote (DQUOTE, US-ASCII 34) characters, prefixing every quote and
backslash character (and possibly other characters too) with a "\" so
as to form a quoted-pair, and possibly introducing folding by
prefixing some WSP with CRLF.
The semantic value of a quoted-string (i.e. the result of reversing
the encapsulation) is a string of characters which includes neither
the optional CFWS outside of the quote characters, nor the quote
characters themselves, nor any CRLF contained within any FWS between
the two quote characters, nor the "\" which introduces any quoted-
pair.
2.5. Language
Various constant strings in this standard, such as header names and
month names, are derived from English words. Despite their
derivation, these words do NOT change when the poster or reader
employing them is interacting in a language other than English.
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Posting and reading agents MAY translate as appropriate in their
interaction with the poster or reader, but the forms that actually
appear in articles as transmitted MUST be the English-derived ones
defined in this standard.
3. Changes to the existing protocols
This standard prescribes many changes, clarifications and new
features since the protocols described in [RFC 1036] and [Son-of-
1036]. 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 section summarizes the main
changes, and comments on some features of the transition.
3.1. Principal Changes
o The [RFC 2822] conventions for parenthesis-enclosed comments in
headers are supported.
o Whitespace is permitted in Newsgroups-headers, permitting folding
of such headers. Indeed, all 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 and all headers
are deemed to be in the UTF-8 character set (thus permitting, in
particular, the use of non-ASCII newsgroup-names).
o Large parts of MIME are recognized as an integral part of
Netnews.
o There is a new Control message 'mvgroup' to facilitate moving a
group to a different place (name) in a hierarchy.
o There are several new headers defined, notably Archive,
Complaints-To, Injector-Info, Mail-Copies-To, Posted-And-Mailed
and User-Agent, leading to increased functionality.
o Provision has been made for almost all headers to have MIME-style
parameters (to be ignored if not recognized), thus facilitating
extension of those headers in future standards.
o Certain headers and Control messages (Appendix A.3 and Appendix
A.4) have been made obsolete.
o Distributions are expected to be checked at the receiving end, as
well as the sending end, of a relaying link.
o There are numerous other small changes, clarifications and
enhancements.
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 standard 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
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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 [RFC 2822] style comments in headers do not affect serving and
relaying agents (note that the Message-ID-, Newsgroups-,
Distribution- and Path-headers do not contain them). They are
unlikely to hinder their proper display in existing reading
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 Newsgroups-headers SHOULD
NOT be used until it has been widely deployed amongst relaying
agents. User agents are unaffected.
o The new style of Path-header is already consistent with the
previous standards. However, the intention is that relaying
agents should eventually reject articles in the old style, and so
this possibility should be offered as a configurable option in
relaying agents. User agents are unaffected.
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 ISO-8859-1. Users expecting to read articles
using other 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 that complies with the previous standards, since
US-ASCII is a strict subset of UTF-8. Insofar as newsgroup-names
containing non-ASCII characters can now be expected to arise,
some support from serving and relaying agents will be desirable,
although it has been established that most current serving agents
can already cope with such names without modification (although
perhaps not in an ideal manner). 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
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using, for example, the visible subset of US-ASCII.
o Users expecting to read headers containing non-ASCII characters
expressed in UTF-8 will need to acquire suitable reading agents
(it is not anticipated that current reading agents will fail to
display such articles, but those non-ASCII characters will likely
appear in some illegible form). The same will be true for users
reading such headers in email on the far side of a news-to-email
gateway; in that case, it will be necessary for the gateway to be
upgraded (see 8.8.1.1).
o The new Control: mvgroup command will need to be implemented in
serving agents. For the benefit of older serving agents it is
therefore RECOMMENDED that it be followed shortly by a
corresponding newgroup command and it MUST always be followed by
a rmgroup command for the old group after a reasonable overlap
period. An implementation of the mvgroup command as an alias for
the newgroup command would thus be minimally conforming. User
agents are unaffected.
o All the headers newly introduced by this standard can safely be
ignored by existing software, albeit with loss of the new
functionality.
4. Basic Format
4.1. Syntax of News Articles
The overall syntax of a news article is:
article = 1*( header CRLF ) separator body
header = other-header
other-header = header-name ":" 1*SP other-content
header-name = 1*name-character *( "-" 1*name-character )
name-character = ALPHA / DIGIT
other-content = <the content of a header defined by some
other standard>
separator = CRLF
body = *( *998text CRLF )
However, the rule given above for header is incomplete. Further
alternatives will be added incrementally as the various Netnews
headers are introduced in this standard (or in future extensions),
using the "=/" notation defined in [RFC 2234]. For example, a
typical USENET-header would be defined as follows:
header =/ USENET-header
USENET-header = "USENET" ":" SP USENET-content
*( ";" ( USENET-parameter /
extension-parameter ) )
USENET-content = <syntax specific to that USENET-header>
USENET-parameter = <a parameter specific to that USENET-header>
where the USENET-parameter, which MUST always be of the same
syntactic form as an extension-parameter (see below), is not provided
in all headers, and even the extension-parameter is omitted in some
cases cases (see 4.2.2). Observe that "USENET" is (and MUST be) of
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the syntactic form of a header-name.
extension-parameter= <a parameter not defined by this standard>
parameter = attribute "=" value
attribute = [CFWS] token [CFWS]
x-token = "x-" token
token = 1*<any (US-ASCII) CHAR except SP, CTLs,
or tspecials>
tspecials = "(" / ")" / "<" / ">" / "@" /
"," / ";" / ":" / "\" / DQUOTE /
"/" / "[" / "]" / "?" / "="
value = [CFWS] token [CFWS] / quoted-string
An article consists of some headers followed by a body. An empty line
separates the two. The headers contain structured information about
the article and its transmission. A header begins with a header-name
identifying it, and can be continued onto subsequent lines as
described in section 4.2.3. The body is largely unstructured text
significant only to the poster and the readers.
NOTE: Terminology here follows the current custom in the news
community, rather than the [RFC 2822] convention of referring to
what is here called a "header" as a "header-field" or "field".
Note that the separator line MUST be truly empty, not just a line
containing white space. Further empty lines following it are part of
the body, as are empty lines at the end of the article.
NOTE: The syntax above defines the canonical form of a news
article as a sequence of lines each terminated by CRLF. This
does not prevent serving agents or transport agents from storing
or handling the article in other formats (e.g. using a single LF
in place of CRLF) so long as the overall effects achieved are as
defined by this standard when operating on the canonical form.
4.2. Headers
The order of headers in an article is not significant. However,
posting agents are encouraged to put mandatory headers (section 5)
first, followed by optional headers (section 6), followed by
experimental headers and headers not defined in this standard or its
extensions. Relaying agents MUST NOT change the order of the headers
in an article.
4.2.1. Naming of Headers
Despite the restrictions on header-name syntax imposed by the
grammar, relaying and reading agents SHOULD tolerate header-names
containing any US-ASCII printable character other than colon (":",
US-ASCII 58).
Whilst relaying agents MUST accept, and pass on unaltered, any non-
variant header whose header-name is syntactically correct, and
reading agents MUST enable them to be displayed, at least optionally,
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posting and injecting agents SHOULD NOT generate headers other than
o headers established by this standard or any extension to it;
o those recognized by other IETF-established standards, notably the
Email standard [RFC 2822] and its extensions, excluding any
explicitly deprecated for Netnews (e.g. see section 9.2.1 for the
deprecated Disposition-Notification-To-header); or,
alternatively, those listed in some future IANA registry of
recognized headers;
o experimental headers beginning with "X-" (as defined in 4.2.5.1);
o on a provisional basis only, headers related to new protocols
under development which are the subject of (or intended to be the
subject of) some IETF-approved RFC (whether Informational,
Experimental or Standards-Track).
However, software SHOULD NOT attempt to interpret headers not
specifically intended to be meaningful in the Netnews environment.
Header-names are case-insensitive. There is a preferred case
convention, which posters and posting agents Ought to use: each
hyphen-separated "word" has its initial letter (if any) in uppercase
and the rest in lowercase, except that some abbreviations have all
letters uppercase (e.g. "Message-ID" and "MIME-Version"). The forms
given in the various rules defining headers in this standard are the
preferred forms for them. Relaying and reading agents MUST, however,
tolerate articles not obeying this convention.
4.2.2. MIME-style Parameters
A few header-specific MIME-style parameters are defined in this
standard, but there is also provision for generic extension-
parameters to appear in most headers for the purpose of allowing
future extensions to those headers. Observe that such parameters do
not, in general, occur in headers defined in other standards, except
for the MIME standards [RFC 2045] et seq. and their extensions.
Extension-parameters, other than those using x-tokens, MUST NOT be
used unless they have first been defined in an IETF-approved RFC
(whether Informational, Experimental or Standards-Track) or, on a
provisional basis only, in relation to new protocols under
development which are the subject of (or intended to be the subject
of) some such IETF-approved RFC. They MUST ONLY be defined for use in
those headers where the syntax of this standard so allows. They
SHOULD NOT, at present, be defined for use in headers in widespread
use prior to the introduction of this standard (this restriction is
likely to be removed in a future version of this standard).
Nevertheless, compliant software MUST accept such parameters wherever
syntactically allowed in this standard (ignoring them if their
meaning is unknown) and SHOULD accept (and ignore) them in all
structured headers wherever defined.
[We could go further, and establish an IANA registry for these
parameters, preloaded with the ones already defined in this standard. A
good model for setting up such a registry is to be found in RFC 2183
(Content-Disposition).]
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NOTE: The syntax does not permit extension-parameters in
unstructured headers (where they are unnecessary) or in certain
headers (notably the Date-, From-, Message-ID-, Reply-To-,
Sender-, Keywords-, Mail-Copies-To-, References-, Supersedes-
and Complaints-To-headers) which are the same (or similar to)
headers already existing in the Email standards.
Each header-specific MIME-style parameter introduced in this standard
is described by specifying
(a) the token to be used in its attribute, and
(b) the syntax rule(s) defining the object(s) permitted in its
value.
If a value object is not of the syntactic form of a token, it MUST
(and otherwise MAY) be encapsulated in a quoted-string (see 2.4.3).
Observe that the syntax of a parameter also allows additional WSP,
folding and comments.
The semantics of a parameter is always to associate the token in its
attribute with the object represented by the token, or the semantic
value (2.4.3) of the quoted-string, contained in its value.
For example, the posting-sender-parameter (6.19) is defined to be
<a parameter with attribute "sender" and value some sender-value>
where
sender-value = mailbox / "verified"
A valid posting-sender-parameter would be
sender = "\"Joe D. Bloggs\" <jdbloggs@bloggs.example>" (authinfo)
The comment (syntactically part of the quoted-string) is irrelevant.
The actual mailbox (to be used, for example, if email is to be sent
to the sender) is
"Joe D. Bloggs" <jdbloggs@bloggs.example>
4.2.3. White Space and Continuations
Each header is logically a single line of characters comprising the
header-name, the colon with its following SP, the content, and any
parameters. For convenience, however, the content and parameters can
be "folded" into a multiple line representation by inserting a CRLF
before any WSP contained within any FWS or CFWS (but not any other SP
or HTAB) allowed by this standard. For example, the header:
Approved: modname@modsite.example (Moderator of example.foo.bar)
can be represented as:
Approved: modname@modsite.example
(Moderator of example.foo.bar)
FWS occurs at many places in the syntax (usually within a CFWS) in
order to allow the inclusion of comments, whitespace and folding. The
syntax is in fact ambiguous insofar as it sometimes allows two
consecutive instantiations of FWS (as least one of which is always
optional), or of an optional FWS followed by an explicit CRLF.
However, all such cases MUST be treated as if the optional
instantiation (or one of them) had not been allowed. It is thus
precluded that any line of a header should be made up of whitespace
characters and nothing else (for such a line might otherwise have
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been interpreted by a non-compliant agent as the separator between
the headers and the body of the article).
NOTE: This does not lead to semantic ambiguity because, unless
specifically stated otherwise, the presence or absence of
folding, a comment or additional WSP has no semantic meaning
and, in particular, it is a matter of indifference whether it
forms a part of the syntactic construct preceding it or the one
following it.
NOTE: It may be observed that the content part of every header
begins and ends with an optional CFWS (or FWS in the case of a
few headers). Moreover, every parameter also begins and ends
with an optional CFWS.
NOTE: Although contents are defined in such a way that folding
can take place between many of the lexical tokens (and even
within some of them), folding should be limited to placing the
CRLF at higher-level syntactic breaks, and should also avoid
leaving trailing WSP on the preceding line. For instance, if a
header-content is defined as comma-separated values, it is
recommended that folding occur after the comma separating the
values, even if it is allowed elsewhere.
In accordance with the syntax, the header-name on the first line MUST
be followed by a SP (even if the rest of the header is empty, but see
4.2.6). Even though the syntax allows otherwise, at least some of
the content MUST appear on that first line (to avoid the possibility
of harm by any non-compliant agent that might eliminate a trailing
WSP). Although posting agents are REQUIRED to enforce these
restrictions, relaying and serving agents SHOULD accept articles that
violate them.
NOTE: This standard differs from [RFC 2822] in requiring that SP
following the colon (it was also an [RFC 1036] requirement).
Posters and posting agents SHOULD use SP, not HTAB, where white space
is desired in headers (some existing software expects this). Relaying
and serving agents SHOULD accept HTAB in all such cases, however.
4.2.4. Comments
Strings of characters which are treated as comments may be included
in headers wherever the syntactic element CFWS occurs. They consist
of characters enclosed in parentheses. Comments may be nested.
NOTE: Although CFWS occurs wherever whitespace is allowed in
almost all headers, there are exceptions where only FWS is
permitted (hence folding but no comments). Notably, this happens
in the case of the Message-ID-, Newsgroups-, Distribution-,
Path- and Followup-To-headers, and within the Date-header except
right at the end.
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A comment is normally used to provide some human readable
informational text, except at the end of a mailbox which contains no
phrase, as in
fred@foo.bar.example (Fred Bloggs)
as opposed to
"Fred Bloggs" <fred@foo.bar.example> .
The former is a deprecated, but commonly encountered, usage and
reading agents SHOULD take special note of such comments as
indicating the name of the person whose mailbox it is. In all other
situations a comment is semantically interpreted as a single SP.
Since a comment is allowed to contain FWS, folding is permitted
within it as well as immediately preceding and immediately following
it. Also note that, since quoted-pair is allowed in a comment, the
parenthesis and backslash characters may appear in a comment so long
as they appear as a quoted-pair. Semantically, the enclosing
parentheses are not part of the content of the comment; the content
is what is contained between the two parentheses.
Since comments have not hitherto been permitted in news articles,
except in a few specified places, posters and posting-agents SHOULD
NOT insert them except in those places, namely following addresses in
From and similar headers, and to indicate the name of the timezone in
Date-headers. However, compliant software MUST accept them in all
places where they are syntactically allowed.
4.2.5. Header Properties
There are three special properties that may apply to particular
headers, namely: "experimental", "inheritable", and "variant". When a
header is defined, in this (or any future) standard, as having one
(or possibly more) of these properties, it is subject to special
treatment, as indicated below.
4.2.5.1. Experimental Headers
Experimental headers are those whose header-names begin with "X-".
They are to be used for experimental Netnews features, or for
enabling additional material to be propagated with an article. They
are not (and will not be) defined by this, or any, standard.
NOTE: Experimental headers are suitable for situations where
they need only to be human readable. They are not intended to be
recognized by widely deployed Netnews software and, should such
a requirement be envisaged, it is preferable to use a normal
header on the provisional basis set out in section 4.2.1.
4.2.5.2. Inheritable Headers
Subject only to the overriding ability of the poster to determine the
contents of the headers in a proto-article, headers with the
inheritable property MUST be copied by followup agents (perhaps with
some modification) into the followup article, and headers without
that property MUST NOT be so copied. Examples include:
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o Newsgroups (5.5) - copied from the precursor, subject to any
Followup-To-header.
o Subject (5.4) - modified by prefixing with "Re: ", but otherwise
copied from the precursor.
o References (6.10) - copied from the precursor, with the addition
of the precursor's Message-ID.
o Distribution (6.6) - copied from the precursor.
NOTE: The Keywords-header is not inheritable, though some older
newsreaders treated it as such.
4.2.5.3. Variant Headers
Headers with the variant property may differ between (or even be
completely absent from) copies of the same article as stored or
relayed throughout a Netnews system. The manner of the difference (or
absence) MUST be as specified in this (or any future) standard.
Typically, these headers are modified as articles are propagated, or
they reflect the status of the article on a particular serving agent,
or cooperating group of such agents. The variant header MAY be placed
anywhere within the headers (though placing it first is recommended).
The principal examples are:
o Path (5.6) - augmented at each relaying agent that an article
passes through.
o Xref (6.16) - used to keep track of the article locators of
crossposted articles so that newsreaders serviced by a particular
serving agent can mark such articles as read.
4.2.6. Undesirable Headers
A header whose content is empty is said to be an empty header (in
fact, no such headers are defined by this standard). Relaying and
reading agents SHOULD NOT consider presence or absence of an empty
header to alter the semantics of an article (although syntactic
rules, such as requirements that certain header-names appear at most
once, MUST still be satisfied). Posting and injecting agents SHOULD
delete empty headers from articles before posting them; relaying
agents MUST pass them untouched.
Headers that merely state defaults explicitly (e.g., a Followup-To-
header with the same content as the Newsgroups-header, or a MIME
Content-Type-header with contents "text/plain; charset=us-ascii") or
state information that reading agents can typically determine easily
themselves (e.g. the length of the body in octets) are redundant and
posters and posting agents Ought Not to include them.
4.3. Body
4.3.1. Body Format Issues
The body of an article SHOULD NOT be empty. A posting or injecting
agent which does not reject such an article entirely SHOULD at least
issue a warning message to the poster and supply a non-empty body.
Note that the separator line MUST be present even if the body is
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empty.
NOTE: Some existing news software is known to react badly to
body-less articles, hence the request for posting and injecting
agents to insert a body in such cases. The sentence "This
article was probably generated by a buggy news reader" has
traditionally been used in this situation.
Note that an article body is a sequence of lines terminated by CRLFs,
not arbitrary binary data, and in particular it MUST end with a CRLF.
However, relaying and serving agents SHOULD treat the body of an
article as an uninterpreted sequence of octets (except as mandated by
changes of CRLF representation and by control message processing, as
in 7.2.4) and SHOULD avoid imposing constraints on it. See also
section 4.5.
Posters SHOULD avoid using control characters and escape sequences
except for tab (US-ASCII 9), formfeed (US-ASCII 12) and, possibly,
backspace (US-ASCII 8). Tab signifies sufficient horizontal white
space to reach the next of a set of fixed positions; posters are
warned that there is no standard set of positions, so tabs should be
avoided if precise spacing is essential. Formfeed (which is sometimes
referred to as the "spoiler character") signifies a point at which a
reading agent Ought to pause and await reader interaction before
displaying further text.
NOTE: Passing other control characters or escape sequences
unaltered to a display or printing device is likely to have
unpredictable results, except in the case of a device adapted to
the special needs of some particular character set.
NOTE: Backspace was historically used for underlining, done by
an underscore (US-ASCII 95), a backspace, and a character,
repeated for each character that should be underlined. Posters
are warned that underlining is not available on all output
devices or supported by all reading agents and is best not
relied on for essential meaning.
4.3.2. Body Conventions
A body is by default an uninterpreted sequence of octets for most of
the purposes of this standard. However, a MIME Content-Type-header
may impose some structure or intended interpretation upon it, and may
also specify the character set in accordance with which the octets
are to be interpreted.
The following conventions for quotations, attributions and
signatures, although not mandated by this standard, describe widely
used practices. They are documented here in order to establish their
correct usage, and the use of the words "MUST", "SHOULD", etc. is to
be understood in that context.
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It is conventional for followup agents to enable the incorporation of
the followed-up article (the "precursor") as a quotation. This SHOULD
be done by prefacing each line of the quoted text (even if it is
empty) with the character ">" (or perhaps with "> " in the case of a
previously unquoted line). This will result in multiple levels of ">"
when quoted content itself contains quoted content, and it will also
facilitate the automatic analysis of articles.
NOTE: Posters should edit quoted context to trim it down to the
minimum necessary. However, followup agents Ought Not to attempt
to enforce this beyond issuing a warning (past attempts to do so
have been found to be notably counter-productive).
The followup agent SHOULD also precede the quoted content by an
"attribution line" (however, readers are warned not to assume that
they are accurate, especially within multiply nested quotations). The
following convention for such lines is intended to facilitate their
automatic recognition and processing by sophisticated reading agents.
The attribution SHOULD contain the name and/or the email address of
the precursor's poster, as in
Joe D. Bloggs <jdbloggs@foo.example> wrote:
or
Helmut Schmidt <helmut@bar.example> schrieb:
The attribution MAY contain also a single newsgroup-name (the one
from which the followup is being made), the precursor's Message-ID
and/or the precursor's Date and Time. Any of these that are present,
SHOULD precede the name and/or email address. However, the inclusion
or not of such fields Ought always to be under the control of the
poster.
To enable this line, and the Message-ID and the email address within
it, to be recognized (for example to enable suitable reading agents
to retrieve the precursor or email its poster by clicking on them),
the following conventions SHOULD be observed:
o The precursor's Message-ID SHOULD be enclosed within <...> or
<news:...>
o The precursor's poster's email address SHOULD be enclosed within
<...>
o The various fields may be separated by arbitrary text and they
may be folded in the same way as headers, but attributions SHOULD
always be terminated by a ":" followed by CRLF.
Further examples:
On comp.foo in <1234@bar.example> on 24 Dec 2001 16:40:20 +0000,
Joe D. Bloggs <jdbloggs@bar.example> wrote:
Am 24. Dez 2001 schrieb Helmut Schmidt <helmut@bar.example>:
A "personal signature" is a short closing text automatically added to
the end of articles by posting agents, identifying the poster and
giving his network addresses, etc. Whenever a poster or posting agent
appends such a signature to an article, it MUST be preceded with a
C. H. Lindsey [Page 25]
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delimiter line containing (only) two hyphens (US-ASCII 45) followed
by one SP (US-ASCII 32). The signature is considered to extend from
the last occurrence of that delimiter up to the end of the article
(or up to the end of the part in the case of a multipart MIME body).
Followup agents, when incorporating quoted text from a precursor,
Ought Not to include the signature in the quotation. Posting agents
Ought to discourage (at least with a warning) signatures of excessive
length (4 lines is a commonly accepted limit).
4.4. Characters and Character Sets
Transmission paths for news articles MUST treat news articles as
uninterpreted sequences of octets, excluding the values 0 (US-ASCII
NUL) and 13 and 10 (US-ASCII CR and LF, which MUST ONLY appear in the
combination CRLF which denotes a line separator).
NOTE: this corresponds to the range of octets permitted for MIME
"8bit data" [RFC 2045]. Thus raw binary data cannot be
transmitted in an article body except by the use of a Content-
Transfer-Encoding such as base64.
[Tentative paragraph to deal with IMAP]
This requirement includes the transmissiom paths between posting
agents, injecting agents, relaying agents, serving agents and reading
agents, but it does NOT include paths traversed by Netnews articles
that have been converted to Email (8.8.1.1). It SHOULD extend to
IMAP4 servers which provide access to Netnews (see the extension
described in section 4.4.3).
Character data is represented by octets in accordance with some
encoding scheme (UTF-8 for headers, and determined by the Content-
Type- and Content-Transfer-Encoding-headers for bodies).
If it comes to a relaying agent's attention that it is being asked to
pass an article using the Content-Transfer-Encoding "8bit" to a
relaying agent that does not support it, it SHOULD report this error
to its administrator. It MUST refuse to pass the article and MUST NOT
re-encode it with different MIME encodings.
NOTE: This strategy will do little harm. The target relaying
agent is unlikely to be able to make use of the article on its
own servers, and the usual flooding algorithm will likely find
some alternative route to get the article to destinations where
it is needed.
4.4.1. Character Sets within Article Headers
Within article headers, characters are represented as octets
according to the UTF-8 encoding scheme [RFC 2279] or [ISO/IEC 10646],
and hence all the characters in Unicode [UNICODE 3.2] or in the
Universal Multiple-Octet Coded Character Set (UCS) [ISO/IEC 10646]
(which is essentially identical to Unicode and expected to remain so)
are potentially available. Although it will usually be unnecessary
C. H. Lindsey [Page 26]
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to use language tagging within headers, the tagging facilities
provided in [UNICODE 3.2] (code points U+E0000 through U+E007F) MAY
be used for that purpose.
NOTE: UTF-8 is an encoding for the [ISO/IEC 10646] character set
(in both its 16 and 32 bit forms) with the property that any
octet less than 128 immediately represents the corresponding
US-ASCII character, thus ensuring upwards compatibility with
previous practice. Non-ASCII characters from Unicode are
represented by sequences of octets satisfying the syntax of a
UTF8-xtra-char (2.4.2), which excludes certain octet sequences
not explicitly permitted by [RFC 2279]. Unicode includes all
characters from the ISO-8859 series of characters sets [ISO
8859] (which includes all Cyrillic, Greek and Arabic characters)
together with the more elaborate characters used in Asian
countries. See the NOTEs in the following section for the
appropriate treatment of Unicode characters by reading agents.
[The sentence mentioning [RFC 2279] could be simplified if [RFC 2279bis]
has been accepted by the time this standard is published.]
Notwithstanding the great flexibility permitted by UTF-8, there is
need for restraint in its use in order that the essential components
of headers may be discerned using reading agents that cannot present
the full Unicode range. In particular, header-names and tokens MUST
be in US-ASCII, and certain other components of headers, as defined
elsewhere in this standard - notably msg-ids, date-times, dot-atoms,
domains and path-identities - MUST be in US-ASCII. Comments, phrases
(as in mailboxes) and unstructured headers (such as the Subject-,
Organization- and Summary-headers) MAY use the full range of UTF-8
characters, but SHOULD nevertheless be invariant under Unicode
normalization NFC [UNICODE 3.2].
NOTE: Unicode allows for composite characters made up of a
starter character - which can be a letter, number, punctuation
mark, or symbol - plus zero or more combining marks (such as
accents, diacritics, and similar). The requirement that a
composite be invariant under normalization NFC means that, where
it could be written in more than one way, only one particular
one of those ways is allowed (for example, the single character
E-acute is preferred over E followed by a non-spacing acute
accent, and A-ring is preferred over the Angstrom symbol). At
least for the main European languages, for which all the needed
composites are already available as single characters, it is
unlikely that posting agents will need to take any special steps
to ensure normalization.
In the particular case of newsgroup-names (see 5.5) there are more
stringent requirements regarding the normalization and other usages
of Unicode.
Where the use of non-ASCII characters is permitted as above, they MAY
be encoded in UTF-8 or they MAY be encoded using the MIME mechanisms
defined in [RFC 2047] and [RFC 2231]. For this purpose, all headers
defined in this standard are to be considered as "extension message
C. H. Lindsey [Page 27]
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header fields" for the purpose of section 5 of [RFC 2047] (insofar as
they are not already covered under the existing Email standards). The
effect of this is to permit the use of [RFC 2047] encodings within
any unstructured header, or within any comment or phrase permitted
within any structured header. Additionally, [RFC 2047] is
considered to incorporate the extension to allow language tags within
encoded-words described in [RFC 2231]. Likewise, the syntax for
parameter (see 4.1 above) is to be considered as replaced by the
revised syntax given in [RFC 2231], the effect of which is to allow
the use of parameter value continuations, character sets and language
information within the MIME-style parameters introduced in this
standard (4.2.2).
[We could go further and include that syntax explicitly in this
document.]
Exceptionally, where some other protocol, for example the
authentication protocol based on OpenPGP defined in [RFC 3156],
restricts some header to 7-bit data, the [RFC 2047] and [RFC 2231]
encodings MUST be used in preference to UTF-8 (see also the similar
restriction in 6.21.3).
[This presupposes that the extension to permit UTF-8 in body part
headers in 6.21.1 survives.]
Examples:
Organization: Technische =?iso-8859-1?Q?Universit=E4t_M=FCnchen?=
Approved: =?iso-8859-1?Q?Fran=E7ois_Faur=E9?= <ff@modsite.example>
(=?iso-8859-1?Q*fr?Mod=E9rateur_autoris=E9?=)
Archive: yes; filename*=iso-8859-1'es'ma=F1ana.txt
Reading agents MUST support the use of UTF-8, [RFC 2047] and [RFC
2231] in all those headers defined in this standard and in the Email
standards, at least to the extent of their ability to display the
characters presented to them. Moreover, since Netnews articles are
regularly emailed as well as posted, and the current Email standards
do not currently admit the use of full UTF-8 in headers, posting
agents MUST ensure that [RFC 2047] and [RFC 2231] are used in
preference to UTF-8 in those cases, at least within the emailed
version (see also 6.9 and 8.8.1.1).
Encoding by other means is not compliant with this standard.
Nevertheless, encoding using other character sets (with no indication
of which one beyond the user's ability to guess based upon other
clues in the article, or custom within the newsgroup) has been in use
in some hierarchies, and such usage may be expected to continue for
some period after the introduction of this standard. Reading agents
MAY, when such usage is detected, attempt to interpet the header
according to whatever other character set can be deduced, or has been
configued as a default by the reader.
NOTE: It is possible to determine, with a high degree of
accuracy, when a given text containing octets with the 8th bit
set was not encoded using UTF-8, and using this test to recover
such non-compliant texts is therefore commended where no other
harm could arise.
C. H. Lindsey [Page 28]
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The [RFC 2047] encoding is not available within headers which contain
a newsgroup-name, notably Newsgroups-headers and Followup-To-headers,
because a newsgroup-name is neither a phrase nor a comment. Moreover
such headers MUST in any case use UTF-8 in order to ensure that
newsgroup-names appear in their canonical form. A special encoding
for newsgroup-names is provided in section 5.5.2 for use when mailing
to moderators and other gatewaying applications (8.7 and 8.8.1.1).
NOTE: The choice between UTF-8 and [RFC 2047] when posting
depends on various factors. Some reading agents do not recogize
[RFC 2047], and some are incapable of decoding UTF-8 (though
there in an increasing tendency for modern reading agents to
understand, or to be configurable to understand, both). Since
headers encoded in UTF-8 are currently prohibited in Email,
special consideration needs to be given to articles that are
both posted and mailed (6.9) or which are mailed to moderators
(see 8.2.2). Posters and implementors of posting agents need to
take account of all these factors when deciding which method to
use.
4.4.2. Character Sets within Article Bodies
Within article bodies, characters are represented as octets according
to the encoding scheme implied by any Content-Transfer-Encoding- and
Content-Type-headers [RFC 2045]. In the absence of such headers,
reading agents cannot be relied upon to display correctly more than
the US-ASCII characters, though they MUST display at least those.
NOTE: The use of non-ASCII characters in the absence of an
appropriate Content-Type-header is not compliant with this
standard. Nevertheless such usage has been seen in some
hierarchies, and it would be reasonable for reading agents to
make an informed "guess" when confronted with that situation,
and in particular it would be wise at least to test whether they
were in the form of valid UTF-8 (see also the suggestion for
such a test in 4.4.1).
NOTE: It is not expected that reading agents will necessarily be
able to present characters in all possible character sets. For
example, a reading agent might be able to present only the ISO-
8859-1 (Latin 1) characters [ISO 8859], in which case it Ought
to present undisplayable characters using some distinctive
glyph, or by exhibiting a suitable warning.
Followup agents MUST be careful to apply appropriate encodings to the
outbound followup. A followup to an article containing non-ASCII
material is very likely to contain non-ASCII material itself.
4.4.3. The NEWS-8BIT-HEADERS IMAP Extension
[This section is highly tentative, and serves as a placeholder to
indicate that an IMAP extension will be needed in order to ensure
consistency with the present form of this draft. It shows the minimum
extension that seems to be necessary, and would require significant
C. H. Lindsey [Page 29]
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further work for any final version.]
The current IMAP4 protocol [RFC 2060] forbids 8-bit characters in
headers (so as to conform with the previous Netnews standard [RFC
1036] amd with the current Email standards).
[That reference to RFC 2060 should be changed to refer to [RFC 2060bis]
if that has been accepted by the time this standard is published.]
Implementations of IMAP4 conforming to this extension MUST
1. In the case of Netnews messages only, accept 8-bit octets in
headers (part specifiers HEADER or MIME, or the header portion of
a MESSAGE/RFC822 part) and pass them on to the client unchanged in
any FETCH response;
2. Interpret all octets in such headers as being in the UTF-8
charset;
3. Include the capability NEWS-8BIT-HEADERS in any CAPABILITY
response.
NOTE: It is the responsibility of the client to interpret such
headers. Users who require to see them displayed correctly will
need to acquire clients with the necessary UTF-8 facilities.
The new capability NEWS-8BIT-HEADERS is to be registered with IANA.
[Memo: remember to update the IANA Considerations section.]
4.5. Size Limits
Posting agents SHOULD endeavour to keep all header lines, so far as
is possible, within 79 characters by folding them at suitable places
(see 4.2.3). However, posting agents MUST permit the poster to
include longer headers if he so insists, and compliant software MUST
support headers of at least 998 octets. Likewise, injecting agents
SHOULD fold any headers generated automatically by themselves.
Relaying agents MUST NOT fold headers (i.e. they must pass on the
folding as received).
NOTE: There is NO restriction on the number of lines into which
a header may be split, and hence there is NO restriction on the
total length of a header (in particular it may, by suitable
folding, be made to exceed the 998 octets restriction pertaining
to a single header line).
The syntax provides for the lines of a body to be up to 998 octets in
length, not including the CRLF. All software compliant with this
standard MUST support lines of at least that length, both in headers
and in bodies, and all such software SHOULD support lines of
arbitrary length. In particular, relaying agents MUST transmit lines
of arbitrary length without truncation or any other modification.
C. H. Lindsey [Page 30]
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NOTE: The limit of 998 octets is consistent with the
corresponding limit in [RFC 2822].
In plain-text messages (those with no MIME headers, or those with a
MIME Content-Type of text/plain) posting agents Ought to endeavour to
keep the length of body lines within some reasonable limit. The size
of this limit is a matter of policy, the default being to keep within
79 characters at most, and preferably within 72 characters (to allow
room for quoting in followups). Exceptionally, posting agents Ought
Not to adjust the length of quoted lines in followups unless they are
able to reformat them in a consistent manner. Moreover, posting
agents MUST permit the poster to include longer lines if he so
insists.
NOTE: Plain-text messages are intended to be displayed "as-is"
without any special action (such as automatic line splitting) on
the part of the recipient. The policy limit (e.g. 72 or 79)
should be expressed as a number of characters (as they will be
displayed by a reading agent) rather than as the number of
octets used to encode them.
NOTE: This standard provides no upper bound on the overall size
of a single article, but neither does it forbid relaying agents
from dropping articles of excessive length. It is, however,
suggested that any limits thought appropriate by particular
agents would be more appropriately expressed in megabytes than
in kilobytes.
4.6. Example
Here is a sample article:
Path: server.example/unknown.site2.example@site2.example/
relay.site.example/site.example/injector.site.example%jsmith
Newsgroups: example.announce,example.chat
Message-ID: <9urrt98y53@site1.example>
From: Ann Example <a.example@site1.example>
Subject: Announcing a new sample article.
Date: Wed, 27 Mar 2002 12:12:50 +0300
Approved: example.announce moderator <jsmith@site.example>
Followup-To: example.chat
Reply-To: Ann Example <a.example+replies@site1.example>
Expires: Mon, 22 Apr 2002 12:12:50 +0300
Organization: Site1, The Number one site for examples.
User-Agent: ExampleNews/3.14 (Unix)
Keywords: example, announcement, standards, RFC 1036, Usefor
Summary: The URL for the next standard.
Injector-Info: injector.site.example; posting-host=du003.site.example
Complaints-To: abuse@site.example
Just a quick announcement that a new standard example article has
been released; it is in the new USEFOR standard obtainable from
ftp.ietf.org.
C. H. Lindsey [Page 31]
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Ann.
--
Ann Example <a.example@site1.example> Sample Poster to the Stars
"The opinions in this article are bloody good ones" - J. Clarke.
[The RFC Editor is invited to change the above Date and Expires headers
to match the actual publication dates and to insert its correct URL.]
5. Mandatory Headers
An article MUST have one, and only one, of each of the following
headers: Date, From, Message-ID, Subject, Newsgroups, Path.
Note also that there are situations, discussed in the relevant parts
of section 6, where References-, Sender-, or Approved-headers are
mandatory. In control messages, specific values are required for
certain headers.
A proto-article (see 8.2.1) may lack some of these mandatory headers,
but they MUST then be supplied by the injecting agent.
5.1. Date
The Date-header contains the date and time that the article was
prepared by the poster ready for transmission and SHOULD express the
poster's local time. The content syntax makes use of syntax defined
in [RFC 2822], subject to the following revised definition of zone.
header =/ Date-header
Date-header = "Date" ":" SP Date-content
Date-content = date-time
zone = (( "+" / "-" ) 4DIGIT) / "UT" / "GMT"
The forms "UT" and "GMT" (indicating universal time) are to be
regarded as obsolete synonyms for "+0000". They MUST be accepted, and
passed on unchanged, by all agents, but they MUST NOT be generated as
part of new articles by posting and injecting agents. The date-time
MUST be semantically valid as required by [RFC 2822]. Although
folding white space is permitted throughout the date-time syntax, it
is RECOMMENDED that a single space be used in each place that FWS
appears (whether it is required or optional).
NOTE: A convention that is sometimes followed is to add a
comment, after the date-time, containing the time zone in
human-readable form, but many of the abbreviations commonly used
for this purpose are ambiguous. The value given by the <zone> is
the only definitive form.
In order to prevent the reinjection of expired articles into the news
stream, relaying and serving agents MUST refuse "stale" articles
whose Date-header predates the earliest articles of which they
normally keep record, or which is more than 24 hours into the future
(though they MAY use a margin less than that 24 hours). Relaying
agents MUST NOT modify the Date-header in transit.
C. H. Lindsey [Page 32]
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5.1.1. Examples
Date: Sat, 26 May 2001 11:13:00 -0500 (EST)
Date: 26 May 2001 16:13 +0000
Date: 26 May 2001 16:13 GMT (Obsolete)
5.2. From
The From-header contains the email address(es), possibly including
the full name(s), of the article's poster(s). The content syntax
makes use of syntax defined in [RFC 2822], subject to the following
revised definition of local-part.
header =/ From-header
From-header = "From" ":" SP From-content
From-content = mailbox-list
addr-spec = local-part "@" domain
local-part = dot-atom / strict-quoted-string
NOTE: This syntax ensures that the local-part of an addr-spec is
restricted to pure US-ASCII (and is thus in strict compliance
with [RFC 2822]), whilst allowing any UTF-8 character to be used
in a preceding quoted-string containing the poster's full name.
If some future extension to the Email protocols should relax
this restriction, one would expect the Netnews protocols to
follow.
Observe that there is no provision for parameters in this
header, or in other headers containing addresses likely to be
used for sending email (see 4.2.2).
Each mailbox in the From-content SHOULD be a valid address, belonging
to the poster(s) of the article, or person or agent on whose behalf
the post is being sent (see the Sender-header, 6.2). When, for
whatever reason, the poster does not wish to include such an address,
the From-content SHOULD then be an address which ends in the top
level domain of ".invalid" [RFC 2606].
NOTE: Since such addresses ending in ".invalid" are
undeliverable, user agents Ought to warn any user attempting to
reply to them and Ought Not, in any case, to attempt to deliver
to them (since that would be pointless anyway). Whether or not
a valid address can subsequently be extracted from such an
address falls outside the scope of this standard (obviously,
posters wishing to disguise their address need to do more than
just add ".invalid" to it).
Be warned, however, that some injecting agents which are unable
to detect that the address belongs to the poster may choose to
insert a Sender-header (but see 8.2.2) or some entry in an
Injector-Info-header (6.19) which discloses some valid address
for the poster.
C. H. Lindsey [Page 33]
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5.2.1. Examples:
From: John Smith <jsmith@site.example>
From: "John Smith" <jsmith@site.example>, dave@isp.example
From: "John D. Smith" <jsmith@site.example>, andrew@isp.example,
fred@site2.example
From: Jan Jones <jan@please_setup_your_system_correctly.invalid>
From: Jan Jones <joe@guess-where.invalid>
From: dave@isp.example (Dave Smith)
NOTE: the last example shows a now deprecated convention of
putting a poster's full name in a comment following the mailbox,
rather than in a phrase at the start of it. Observe also the use
of the quoted-string "John D. Smith" which is required on
account of presence of the '.' character, and which would also
have been required had any UTF8-xtra-char been present.
5.3. Message-ID
The Message-ID-header contains the article's message identifier, a
unique identifier distinguishing the article from every other
article. The content syntax makes use of syntax defined in [RFC
2822], subject to the following revised definitions of msg-id, no-
fold-quote and no-fold-literal.
header =/ Message-ID-header
Message-ID-header = "Message-ID" ":" SP Message-ID-content
Message-ID-content = [FWS] msg-id [FWS]
msg-id = "<" id-left "@" id-right ">"
id-left = dot-atom-text / no-fold-quote
id-right = dot-atom-text / no-fold-literal
no-fold-quote = DQUOTE
*( strict-qtext / "\\" / "\" DQUOTE )
qspecial
*( strict-qtext / "\\" / "\" DQUOTE )
DQUOTE
qspecial = "(" / ")" / ; same as specials except
"<" / ">" / ; "\" and DQUOTE quoted
"[" / "]" /
":" / ";" /
"@" / "\\" /
"," / "." /
"\" DQUOTE
no-fold-literal = "[" *( dtext / "\[" / "\]" / "\\" ) "]"
The msg-id MUST NOT be more than 250 octets in length.
NOTE: Observe that, in contrast to the corresponding header in
[RFC 2822], the syntax does not allow comments within the
Message-ID-header; this is to simplify processing by relaying
and serving agents and to ensure interoperability with existing
implementations.
C. H. Lindsey [Page 34]
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The restriction to strict-qtext ensures that no UTF8-xtra-char
can appear. Msg-ids as defined here are a "normalized" subset of
those defined by [RFC 2822], ensuring that no string of
characters is quoted unless strictly necessary (it must contain
at least one qspecial) and no single character is prefixed by a
"\" in the form of a quoted-pair unless strictly necessary, and
moreover there is no possibility for WSP to occur, whether
quoted or not. The length restriction ensures that systems which
accept message identifiers as a parameter when retrieving an
article (e.g. [NNTP]) can rely on a bounded length. Observe that
msg-id includes the '<' and '>'.
An agent generating an article's message identifier MUST ensure that
it is unique (as also required in [RFC 2822]) and that it is chosen
in such a way that it will NEVER be applied to any other Netnews
article or Email message. However, an article emailed (without
encapsulation) to a moderator (8.2.2 and 8.7) or gatewayed into some
other medium (8.8.1) SHOULD retain the same message identifier
throughout its travels so long as it remains recognizably the same
article.
Even though commonly derived from the domain name of the originating
site (and domain names are case-insensitive), a message identifier
MUST NOT be altered in any way during transport, or when copied (as
into a References-header), and thus a simple (case-sensitive)
comparison of octets will always suffice to recognize that same
message identifier wherever it subsequently reappears.
NOTE: These requirements are to be contrasted with those of the
un-normalized msg-ids defined by [RFC 2822], which may perfectly
legitimately become normalized (or vice versa) during transport
or copying in email systems.
NOTE: Some old software may treat message identifiers that
differ only in case within their id-right part as equivalent,
and implementors of agents that generate message identifiers
should be aware of this.
5.4. Subject
The Subject-header contains a short string identifying the topic of
the message. This is an inheritable header (4.2.5.2) to be copied
into the Subject-header of any followup, in which case the new
Subject-content SHOULD then default to the string "Re: " (a "back
reference") followed by the contents of the pure-subject of the
precursor. Any leading "Re: " in that pure-subject MUST be stripped.
header =/ Subject-header
Subject-header = "Subject" ":" SP Subject-content
Subject-content = [ [FWS] back-reference ] pure-subject
pure-subject = unstructured
back-reference = %x52.65.3A.20
; which is a case-sensitive "Re: "
C. H. Lindsey [Page 35]
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The pure-subject MUST NOT begin with "Re: ".
NOTE: The syntax of unstructured differs from that prescribed in
[RFC 2822], so ensuring that the Subject-content is not
permitted to be completely empty, or to consist of WSP only (see
remarks in 4.2.6 concerning undesirable headers).
Followup agents MAY remove strings that are known to be used
erroneously as back-reference (such as "Re(2): ", "Re:", "RE: ", or
"Sv: ") from the Subject-content when composing the subject of a
followup, and add a correct back-reference in front of the result.
NOTE: that would be "SHOULD remove instances" except that we
cannot find a sufficiently robust and simple algorithm to do the
necessary natural language processing.
Followup agents MUST NOT use any other string except "Re: " as a back
reference. Specifically, a translation of "Re: " into a local
language or usage MUST NOT be used.
NOTE: "Re" is an abbreviation for the Latin "In re", meaning "in
the matter of", and not an abbreviation of "Reference" as is
sometimes erroneously supposed.
Agents SHOULD NOT depend on nor enforce the use of back references by
followup agents.
For compatibility with legacy news software, the Subject-content of a
control message (i.e. an article that also contains a Control-header)
MAY start with the string "cmsg ", and non-control messages MUST NOT
start with the string "cmsg ". See also section 6.13.
5.4.1. Examples
In the following examples, please note that only "Re: " is mandated
by this standard. "was: " is a convention used by many English-
speaking posters to signal a change in subject matter. Software can
always recognize such changes from the References-header.
Subject: Film at 11
Subject: Re: Film at 11
Subject: Godwin's law considered harmful (was: Film at 11)
Subject: Godwin's law (was: Film at 11)
Subject: Re: Godwin's law (was: Film at 11)
Subject: Re: Godwin's law
5.5. Newsgroups
The Newsgroups-header's content specifies the newsgroup(s) in which
the article is intended to appear. It is an inheritable header
(4.2.5.2) which then becomes the default Newsgroups-header of any
followup, unless a Followup-To-header is present to prescribe
otherwise. Articles MUST NOT be passed between relaying agents or to
serving agents unless the sending agent has been configured to supply
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and the receiving agent to receive at least one of the newsgroup-
names in the Newsgroups-header.
In order to allow newsgroup-names containing Non-ASCII characters,
this section relies heavily on the provisions of the Unicode
Standard. All references to "Unicode" mean [UNICODE 3.2] or any
standard that supersedes it. That document contains guarantees of
strict future upwards compatibility (e.g. no character will be
removed or change classification). Implementors should be aware that
currently unassigned code points (Unicode category Cn) may become
valid characters in future versions of Unicode. Since the poster of
an article might have access to a newer version of that standard,
relaying and serving agents MUST accept such characters, but posting
agents (and indeed all agents) MUST NOT generate them (though they
might well follow up to newsgroup-names containing them).
header =/ Newsgroups-header
Newsgroups-header = "Newsgroups" ":" SP Newsgroups-content
*( ";" extension-parameter )
Newsgroups-content = [FWS] newsgroup-name
*( [FWS] ng-delim [FWS] newsgroup-name )
[FWS]
newsgroup-name = component *( "." component )
component = 1*component-grapheme
ng-delim = ","
component-grapheme = combiner-base *combiner-mark
combiner-base = combiner-ASCII / combiner-extended
combiner-ASCII = DIGIT / ALPHA / "+" / "-" / "_"
combiner-extended = <any character with a Unicode code value
of 0080 or greater but excluding any
character in Unicode categories
Cc, Cf, Cs, M* and Z*>
combiner-mark = <any character with a Unicode code value of
0080 or greater and in Unicode category M*>
NOTE: the excluded characters in a combiner-extended are control
characters (Cc), format control characters (Cf), surrogates
(Cs), marks (M*) and separators (Z*). In particular, this
excludes all whitespace characters. To all intents and
purposes, a component-grapheme is what a user might regard as a
single "character" as displayed on his screen, though it might
be transmitted as several actual characters (e.g. q-circumflex
is two characters). Note also that, in some writing schemes,
several component-graphemes will merge into one visible object
of variable size.
Each component MUST be invariant under Unicode normalization NFKC
(cf. the weaker normalization requirement for other headers in
section 4.4.1 which specified no more than normalization NFC, and see
also the explanatory NOTE in that section).
NOTE: As a result of of this restriction, a name has only one
valid form. Implementations can assume that a straight (case
sensitive) comparison of characters or octets is sufficient to
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compare two newsgroup-names.
The requirement that names be invariant under NFKC, rather than
NFC, means that all characters with a "compatibility
decomposition" are forbidden (Unicode provides the property
"NFKC_NO" to make this test easier). The effect is to exclude
variant forms of characters, such as superscripts and
subscripts, wide and narrow forms, font variants, encircled
forms, ligatures, and so on, as their use could cause confusion.
There is insufficient experience in this area to determine
whether this is the right long-term solution. Implementors
should therefore be aware that a future version of this standard
might reduce the requirement in the direction of NFC as opposed
to NFKC.
NOTE: An implementation is not required to apply NFKC, or any
other normalization, to newsgroup-names. Only agencies that
create new groups need to be careful to obey this restriction
(7.2.1). However, if a posting agent neglects to normalize a
newsgroup-name entered manually, this may lead to the user
posting to a non-existent group without understanding why.
Newsgroup-names containing non-ASCII characters MUST be encoded in
UTF-8. The use of [RFC 2047] encoding is inappropriate for reasons
explained in section 4.4.1.
Components beginning with underline ("_") are reserved for use by
future versions of this standard and MUST NOT occur in newsgroup-
names (whether in Newsgroups-headers or in newgroup control messages
(7.2.1)). However, such names MUST be accepted.
Components beginning with "+" or "-" are reserved for use by
implementations and MUST NOT occur in newsgroup-names (whether in
Newsgroups-headers or in newgroup control messages). Implementors may
assume that this rule will not change in any future version of this
standard.
NOTE: For example, implementors may safely use leading "+" and
"-" to "escape" other entities within something that looks like
a newsgroup-name.
Agencies responsible for the administration of particular hierarchies
Ought to place additional restrictions on the characters they allow
in newsgroup-names within those hierarchies (such as to accord with
the languages commonly used within those hierarchies, or to avoid
perceived ambiguities pertinent to those languages). Where there is
no such specific policy, the following restrictions SHOULD be applied
to newsgroup-names.
NOTE: These restrictions are intended to reflect existing
practice, with some additions to accommodate foreseeable
enhancements, and are intended both to avoid certain technical
difficulties and to avoid unnecessary confusion. It may well be
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that experience will allow future extensions to this standard to
relax some or all of these restrictions.
The specific restrictions (to be applied in the absence of
established policies to the contrary) are:
1. The following characters are forbidden, subject to the comments
and notes at the end of the list:
characters in category Cn (Other, Not assigned) [1]
characters in category Co (Other, Private Use) [2]
characters in category Lt (Letter, Titlecase) [3]
characters in category Lu (Letter, Uppercase) [3]
characters in category Me (Mark, Enclosing) [4]
characters in category Pd (Punctuation, Dash) [4][5]
characters in category Pe (Punctuation, Close) [4]
characters in category Pf (Punctuation, Final quote) [4]
characters in category Pi (Punctuation, Initial quote) [4]
characters in category Po (Punctuation, Other) [4]
characters in category Ps (Punctuation, Open) [4]
characters in category Sc (Symbol, Currency) [4]
characters in category Sk (Symbol, Modifier) [4]
characters in category Sm (Symbol, Math) [4][5]
characters in category So (Symbol, Other) [4]
[1] As new characters are added to Unicode, the code point moves
from category Cn to some other category. As stated above,
implementors should be prepared for this.
[2] Specific private use characters can be used within a hierarchy
or co-operating subnet that has agreed meanings for them.
[3] Traditionally, newsgroup-names have been written in lowercase.
Posting agents Ought Not to convert uppercase or titlecase
characters to the corresponding lowercase forms except under
the explicit instructions of the poster.
[4] Traditionally newsgroup-names have only used letters, digits,
and the three special characters "+", "-" and "_". These
categories correspond to characters outside that set.
[5] Although the characters "+" and "-" are within categories Pd
and Sm, they are not forbidden.
2. A component name is forbidden to consist entirely of digits.
NOTE: This requirement was in [RFC 1036] but nevertheless
several such groups have appeared in practice and implementors
should be prepared for them. A common implementation technique
uses each component as the name of a directory and uses numeric
filenames for each article within a group. Such an
implementation needs to be careful when this could cause a clash
(e.g. between article 123 of group xxx.yyy and the directory for
group xxx.yyy.123).
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3. A component is limited to 30 component-graphemes and a newsgroup-
name to 71 component-graphemes (counting also the '.'s separating
the components). Whilst there is no longer any technical reason to
limit the length of a component (formerly, it was limited to 14
octets) nor of a newsgroup-name, it should be noted that these
names are also used in the newsgroups-line (7.2.1.2) where an
overall policy limit applies and, moreover, excessively long names
can be exceedingly inconvenient in practical use.
Serving and relaying agents MUST accept any newsgroup-name that meets
the above requirements, even if they violate one or more of the
policy restrictions. Posting and injecting agents MAY reject articles
containing newsgroup-names that do not meet these restrictions, and
posting agents MAY attempt to correct them (but only with the
explicit agreement of the poster for anything more than NFC or NFKC
normalization). However, because of the large and changing tables
required to do these checks and corrections throughout the whole of
Unicode, this standard does not require them to do so. Rather, the
onus is placed on those who create new newsgroups (7.2.1) to check
the mandatory requirements, to consider the effects of relaxing the
other restrictions, and to consider how all this may affect
propagation of the group.
Since future extensions to this standard and the Unicode standard,
including a possible relaxation of the NFKC normalization, plus any
relaxations of the default restrictions introduced by specific
hierarchies might invalidate some such checks, warnings, and
adjustments, implementations MUST incorporate means to disable them.
NOTE: The newsgroup-name as encoded in UTF-8 should be regarded as
the canonical form. Reading agents may convert it to whatever
character set they are able to display and serving agents may
possibly need to convert it to some form more suitable as a
filename. Simple algorithms for both kinds of conversion are
readily available. Observe that the syntax does not allow
comments within the Newsgroups-header; this is to simplify
processing by relaying and serving agents which have a requirement
to process this header extremely rapidly.
The inclusion of folding white space within a Newsgroups-content is a
newly introduced feature in this standard. It MUST be accepted by all
conforming implementations (relaying agents, serving agents and
reading agents). Posting agents should be aware that such postings
may be rejected by overly-critical old-style relaying agents. When a
sufficient number of relaying agents are in conformance, posting
agents SHOULD generate such whitespace in the form of <CRLF WSP> so
as to keep the length of lines in the relevant headers (notably
Newsgroups and Followup-To) to no more than than 79 characters (or
other agreed policy limit - see 4.5). Before such critical mass
occurs, injecting agents MAY reformat such headers by removing
whitespace inserted by the posting agent, but relaying agents MUST
NOT do so.
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Posters SHOULD use only the names of existing newsgroups in the
Newsgroups-header. However, it is legitimate to cross-post to
newsgroups which do not exist on the posting agent's host, provided
that at least one of the newsgroups DOES exist there, and followup
agents SHOULD accept this (posting agents MAY accept it, but Ought at
least to alert the poster to the situation and request confirmation).
Relaying agents MUST NOT rewrite Newsgroups-headers in any way, even
if some or all of the newsgroups do not exist on the relaying agent's
host. Serving agents MUST NOT create new newsgroups simply because an
unrecognized newsgroup-name occurs in a Newsgroups-header (see 7.2.1
for the correct method of newsgroup creation).
The Newsgroups-header is intended for use in Netnews articles rather
than in email messages. It MAY be used in an email message to
indicate that it is a copy also posted to the listed newsgroups, in
which case the inclusion of a Posted-And-Mailed header (6.9) would
also be appropriate. However, it SHOULD NOT be used in an email-only
reply to a Netnews article (thus the "inheritable" property of this
header applies only to followups to a newsgroup, and not to followups
to the poster). Moreover, if a newsgroup-name contains any non-ASCII
character, it may need to be encoded using the mechanism defined in
section 5.5.2. See also the further discussion in section 8.8.1.1.
5.5.1. Forbidden newsgroup-names
The following forms of newsgroup-name MUST NOT be used except for the
specific purposes indicated:
o Newsgroup-names having only one component. These are reserved for
newsgroups whose propagation is restricted to a single host or
local network, and for pseudo-newsgroups such as "poster" (which
has special meaning in the Followup-To-header - see section 6.7),
"junk" (often used by serving agents), and "control" (likewise);
o Any newsgroup-name beginning with "control." (used as pseudo-
newsgroups by many serving agents);
o Any newsgroup-name containing the component "ctl" (likewise);
o "to" or any newsgroup-name beginning with "to." (reserved for the
ihave/sendme protocol described in section 7.4, and for test
messages sent on an essentially point-to-point basis);
o Any newsgroup-name beginning with "example." (reserved for
examples in this and other standards);
o Any newsgroup-name containing the component "all" (because this
is used as a wildcard in some implementations).
A newsgroup-name SHOULD NOT appear more than once in the Newsgroups-
header. The order of newsgroup-names in the Newsgroups-header is not
significant, except for determining which moderator to send the
article to if more than one of the groups is moderated (see 8.2).
5.5.2. Encoded newsgroup-names
Where it is required to transport an article across some medium that
cannot reliably convey the full 8 bits of each octet, such as when
gatewaying it into Email (8.8.1.1), or when emailing it to a
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moderator or constructing the submission address of the moderator
(8.2.2), it will be necessary under the current email standards to
encode any newsgroup-name that contains some non-ASCII character
(such as one occurring within a Newsgroups- or Followup-To-header).
For that purpose, the following algorithm is provided:
1. Initially, the newsgroup-name is in the form of a sequence of
octets representing that name in the UTF-8 character set.
2. Each octet in the name in the range 0x80-FF is replaced by an "="
character (US-ASCII 61), followed by two characters representing
that octet in hexadecimal, in which the hexadecimal digits "A"
through "F" MUST be in uppercase.
3. Each octet in the name in the range 0x00-7F remains unaltered (and
thus MUST NOT be replaced by its hexadecimal equivalent).
NOTE: Observe that this algorithm provides a unique encoding for
each newsgroup-name. Observe also that within the unaltered
range 0x00-7F, only the octets 0x2B, 0x2D-2E, 0x30-39, 0x41-5A,
0x5F, and 0x61-7A can appear in a newsgroup-name.
This standard provides no authority for the use of this algorithm
other than in the context of newsgroup-names occurring within headers
being conveyed by email. In particular, it MUST NOT be used within
any article conveyed by the Netnews protocols and thus, if an email
using it is subsequently returned to the Netnews environment, it MUST
be decoded back into UTF-8.
5.6. Path
The Path-header shows the route taken by a message since its entry
into the Netnews system. It is a variant header (4.2.5.3), each agent
that processes an article being required to add one (or more) entries
to it. This is primarily to enable relaying agents to avoid sending
articles to sites already known to have them, in particular the site
they came from, and additionally to permit tracing the route articles
take in moving over the network, and for gathering Usenet statistics.
Finally the presence of a '%' path-delimiter in the Path-header can
be used to identify an article injected in conformance with this
standard.
5.6.1. Format
header =/ Path-header
Path-header = "Path" ":" SP Path-content
*( ";" extension-parameter )
Path-content = [FWS]
*( path-identity [FWS] path-delimiter [FWS] )
tail-entry [FWS]
path-identity = ( ALPHA / DIGIT )
*( ALPHA / DIGIT / "-" / "." / ":" / "_" )
path-delimiter = "/" / "?" / "%" / "," / "!"
tail-entry = path-identity
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NOTE: A Path-content will inevitably contain at least one path-
identity, except possibly in the case of a proto-article that
has not yet been injected onto the network.
NOTE: Observe that the syntax does not allow comments within the
Path-header; this is to simplify processing by relaying and
injecting agents which have a requirement to process this header
extremely rapidly.
A relaying agent SHOULD NOT pass an article to another relaying agent
whose path-identity (or some known alias thereof) already appears in
the Path-content. Since the comparison may be either case sensitive
or case insensitive, relaying agents SHOULD NOT generate a name which
differs from that of another site only in terms of case.
A relaying agent MAY decline to accept an article if its own path-
identity is already present in the Path-content or if the Path-
content contains some path-identity whose articles the relaying agent
does not want, as a matter of local policy.
NOTE: This last facility is sometimes used to detect and decline
control messages (notably cancel messages) which have been
deliberately seeded with a path-identity to be "aliased out" by
sites not wishing to act upon them.
5.6.2. Adding a path-identity to the Path-header
When an injecting, relaying or serving agent receives an article, it
MUST prepend its own path-identity followed by a path-delimiter to
the beginning of the Path-content. In addition, it SHOULD then add
CRLF and WSP if it would otherwise result in a line longer than 79
characters.
The path-identity added MUST be unique to that agent. To this end it
SHOULD be one of:
1. A fully qualified domain name (FQDN) associated (by the Internet
DNS service [RFC 1034]) with an A record, which SHOULD identify
the actual machine prepending this path-identity. Ideally, this
FQDN should also be "mailable" (see below).
2. A fully qualified domain name (FQDN) associated (by the Internet
DNS service) with an MX record, which MUST be "mailable".
3. An arbitrary name believed to be unique and registered at least
with all sites immediately downstream from the given site.
4. An encoding of an IP address - <IPv4address> or <IPv6address> [RFC
2373] (the requirement to be able to use an <IPv6address> is the
reason for including ':' as an allowed character within a path-
identity).
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The FQDN of an agent is "mailable" if the administrators of that
agent can be reached by email using both of the forms "usenet@<FQDN>"
and "news@<FQDN>", in conformity with [RFC 2142].
Of the above options, nos. 1 to 3 are much to be preferred, unless
there are strong technical reasons dictating otherwise. In
particular, the injecting agent's path-identity MUST, as a special
case, be an FQDN as in option 1 or option 2, and MUST be mailable.
Additionally, in the case of an injecting agent offering its services
to the general public, its administrators MUST also be reachable
using the form "abuse@<FQDN>" UNLESS a more specific complaints
address has been specified in a Complaints-To-header (6.20).
The injecting agent's path-identity MUST be followed by the special
path-delimiter '%' which serves to separate the pre-injection and
post-injection regions of the Path-content (see 5.6.3).
In the case of a relaying or serving agent, the path-delimiter is
chosen as follows. When such an agent receives an article, it MUST
establish the identity of the source and compare it with the leftmost
path-identity of the Path-content. If it matches, a '/' should be
used as the path-delimiter when prepending the agent's own path-
identity. If it does not match then the agent should prepend two
entries to the Path-content; firstly the true established path-
identity of the source followed by a '?' path-delimiter, and then,
to the left of that, the agent's own path-identity followed by a '/'
path-delimiter as usual. This prepending of two entries SHOULD NOT
be done if the provided and established identities match.
Any method of establishing the identity of the source may be used
(but see 5.6.5 below), with the consideration that, in the event of
problems, the agent concerned may be called upon to justify it.
NOTE: The use of the '%' path-delimiter marks the position of
the injecting agent in the chain. In normal circumstances there
should therefore be only one '%' path-delimiter present, and
injecting agents MAY choose to reject proto-articles with a '%'
already in them. If, for whatever reason, more than one '%' is
found, then the path-identity in front of the leftmost '%' is to
be regarded as the true injecting agent.
5.6.3. The tail-entry
For historical reasons, the tail-entry (i.e. the rightmost entry in
the Path-content) is regarded as a "user name", and therefore MUST
NOT be interpreted as a site through which the article has already
passed. Moreover, the Path-content as a whole is not an email address
and MUST NOT be used to contact the poster. Posting and/or injecting
agents MAY place any string here. When it is not an actual user
name, the string "not-for-mail" is often used, but in fact a simple
"x" would be sufficient.
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Often this field will be the only entry in the region (known as the
pre-injection region) after the '%', although there may be entries
corresponding to machines traversed between the posting agent and the
injecting agent proper. In particular, injecting agents that receive
articles from many sources MAY include information to establish the
circumstances of the injection such as the identity of the source
machine (especially if an Injector-Info-header (6.19) is not being
provided). Any such inclusion SHOULD NOT conflict with any genuine
site identifier. The '!' path-delimiter may be used freely within
the pre-injection region, although '/' and '?' are also appropriate
if used correctly.
5.6.4. Path-Delimiter Summary
A summary of the various path-delimiters. The name immediately to the
left of the path-delimiter is always that of the machine which added
the path-delimiter.
'/' The name immediately to the right is known to be the identity of
the machine from which the article was received (either because
the entry was made by that machine and we have verified it, or
because we have added it ourselves).
'?' The name immediately to the right is the claimed identity of the
machine from which the article was received, but we were unable
to verify it (and have prepended our own view of where it came
from, and then a '/').
'%' Everything to the right is the pre-injection region followed by
the tail-entry. The name on the left is the FQDN of the
injecting agent. The presence of two '%'s in a path indicates a
double-injection (see 8.2.2).
'!' The name immediately to the right is unverified. The presence of
a '!' to the left of the '%' indicates that the identity to the
left is that of an old-style system not conformant with this
standard.
',' Reserved for future use, treat as '/'.
Other
Old software may possibly use other path-delimiters, which should
be treated as '!'. But note in particular that ':', '-' and '_'
are components of names, not path-delimiters, and FWS on its own
MUST NOT be used as the sole path-delimiter.
NOTE: Old Netnews relaying and injecting agents almost all
delimit Path entries with a '!', and these entries are not
verified. The presence of '%' indicates that the article was
injected by software conforming to this standard, and the
presence of '!' to the left of a '%' indicates that the message
passed through systems developed prior to this standard. It is
anticipated that relaying agents will reject articles in the old
style once this new standard has been widely adopted.
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5.6.5. Suggested Verification Methods
It is preferable to verify the claimed path-identity against the
source than to make routine use of the '?' path-delimiter, with
consequential wasteful double-entry Path additions.
If the incoming article arrives through some TCP/IP protocol such as
NNTP, the IP address of the source will be known, and will likely
already have been checked against a list of known FQDNs, IP
addresses, or other registered aliases that the receiving site has
agreed to peer with.
Since the source host may have several IP addresses, checking the
claimed FQDN or IP address against the source IP, or finding a
suitable FQDN to report with a '?' path-delimiter, may involve
several DNS lookups, following CNAME chains as required. Note that
any reverse DNS lookup that is involved needs to be confirmed by a
forward one.
If the incoming article arrives through some other protocol, such as
UUCP, that protocol MUST include a means of verifying the source
site. In UUCP implementations, commonly each incoming connection has
a unique login name and password, and that login name (or some alias
registered for it) would be expected as the path-identity.
5.6.6. Example
Path: foo.isp.example/
foo-server/bar.isp.example?10.123.12.2/old.site.example!
barbaz/baz.isp.example%dialup123.baz.isp.example!x
NOTE: That article was injected into the news stream by
baz.isp.example (complaints may be addressed to
abuse@baz.isp.example). The injector has taken care to record
that it got it from dialup123.baz.isp.example. "x" is a dummy
tail-entry, though sometimes a real userid is put there.
The article was relayed, perhaps by UUCP, to the machine known,
at least to its downstream, as "barbaz".
Barbaz relayed it to old.site.example, which does not yet
conform to this standard (hence the '!' path-delimiter). So one
cannot be sure that it really came from barbaz.
Old.site.example relayed it to a site claiming to have the IP
address [10.123.12.2], and claiming (by using the '/' path-
delimiter) to have verified that it came from old.site.example.
[10.123.12.2] relayed it to "foo-server" which, not being
convinced that it truly came from [10.123.12.2], did a reverse
lookup on the actual source and concluded it was known as
bar.isp.example (that is not to say that [10.123.12.2] was not a
correct IP address for bar.isp.example, but simply that that
connection could not be substantiated by foo-server). Observe
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that foo-server has now added two entries to the Path.
"foo-server" is a locally significant name within the complex
site of many machines run by foo.isp.example, so the latter
should have no problem recognizing foo-server and using a '/'
path-delimiter. Presumably foo.isp.example then delivered the
article to its direct clients.
It appears that foo.isp.example and old.site.example decided to
fold the line, on the grounds that it seemed to be getting a
little too long.
6. Optional Headers
None of the headers appearing in this section is required to appear
in every article but some of them are required in certain types of
article, such as followups. Any header defined in this (or any other)
standard MUST NOT appear more than once in an article unless
specifically stated otherwise. Experimental headers (4.2.5.1) and
headers defined by cooperating subnets are exempt from this
requirement. See section 8 "Duties of Various Agents" for the full
picture.
6.1. Reply-To
The Reply-To-header specifies a reply address(es) to be used for
personal replies for the poster(s) of the article when this is
different from the poster's address(es) given in the From-header. The
content syntax makes use of syntax defined in [RFC 2822], but subject
to the revised definition of local-part given in section 5.2.
header =/ Reply-To-header
Reply-To-header = "Reply-To" ":" SP Reply-To-content
Reply-To-content = address-list
In the absence of Reply-To, the reply address(es) is the address(es)
in the From-header. For this reason a Reply-To SHOULD NOT be included
if it just duplicates the From-header.
NOTE: Use of a Reply-To-header is preferable to including a
similar request in the article body, because replying agents can
take account of Reply-To automatically.
6.1.1. Examples
Reply-To: John Smith <jsmith@site.example>
Reply-To: John Smith <jsmith@site.example>, dave@isp.example
Reply-To: John Smith <jsmith@site.example>,andrew@isp.example,
fred@site2.example
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6.2. Sender
The Sender-header specifies the mailbox of the person or entity which
caused this article to be posted (and hence injected), if that person
or entity is different from that given in the From-header or if more
than one mailbox appears in the From-header. This header SHOULD NOT
appear in an article unless the sender is different from the poster.
This header is appropriate for use by automatic article posters. The
content syntax makes use of syntax defined in [RFC 2822], subject to
the revised definition of local-part given in section 5.2.
header =/ Sender-header
Sender-header = "Sender" ":" SP Sender-content
Sender-content = mailbox
6.3. Organization
The Organization-header is a short phrase identifying the poster's
organization.
header =/ Organization-header
Organization-header = "Organization" ":" SP Organization-content
Organization-content= unstructured
NOTE: Posting and injecting agents are discouraged from
providing a default value for this header unless it is
acceptable to all posters using those agents. Unless this header
contains useful information (including some indication of the
posters physical location) posters are discouraged from
including it.
6.4. Keywords
The Keywords field contains a comma separated list of important words
and phrases intended to describe some aspect of the content of the
article. The content syntax makes use of syntax defined in [RFC
2822].
header =/ Keywords-header
Keywords-header = "Keywords" ":" SP Keywords-content
Keywords-content = phrase *( "," phrase )
NOTE: The list is comma separated, NOT space separated.
NOTE: Contrary to the usage defined in [RFC 2822], this standard
does not permit multiple occurrences of this header.
6.5. Summary
The Summary-header is a short phrase summarizing the article's
content.
header =/ Summary-header
Summary-header = "Summary" ":" SP Summary-content
C. H. Lindsey [Page 48]
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Summary-content = unstructured
The summary should be terse. Authors Ought to avoid trying to cram
their entire article into the headers; even the simplest query
usually benefits from a sentence or two of elaboration and context,
and not all reading agents display all headers. On the other hand the
summary should give more detail than the Subject.
6.6. Distribution
The Distribution-header is an inheritable header (see 4.2.5.2) which
specifies geographical or organizational limits to an article's
propagation.
header =/ Distribution-header
Distribution-header = "Distribution" ":" SP Distribution-content
*( ";" extension-parameter )
Distribution-content= distribution *( dist-delim distribution )
dist-delim = ","
distribution = [FWS] distribution-name [FWS]
distribution-name = ALPHA 1*distribution-rest
distribution-rest = ALPHA / "+" / "-" / "_"
NOTE: The use of ALPHA in the syntax ensures that distribution
names are always in US-ASCII.
Articles MUST NOT be passed between relaying agents or to serving
agents unless the sending agent has been configured to supply and the
receiving agent to receive at least one of the distributions in the
Distribution-header. Additionally, reading agents MAY also be
configured so that unwanted distributions do not get displayed.
NOTE: Although it would seem redundant to filter out unwanted
distributions at both ends of a relaying link (and it is clearly
more efficient to do so at the sending end), many sending sites
have been reluctant, historically speaking, to apply such
filters (except to ensure that distributions local to their own
site or cooperating subnet did not escape); moreover they tended
to configure their filters on an "all but those listed" basis,
so that new and hitherto unheard of distributions would not be
caught. Indeed many "hub" sites actually wanted to receive all
possible distributions so that they could feed on to their
clients in all possible geographical (or organizational)
regions.
Therefore, it is desirable to provide facilities for rejecting
unwanted distributions at the receiving end. Indeed, it may be
simpler to do so locally than to inform each sending site of
what is required, especially in the case of specialized
distributions (for example for control messages, such as cancels
from certain issuers) which might need to be added at short
notice. The possibility for reading agents to filter
distributions has been provided for the same reason.
C. H. Lindsey [Page 49]
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Exceptionally, ALL relaying agents are deemed willing to supply or
accept the distribution "world", and NO relaying agent should supply
or accept the distribution "local". However, "world" SHOULD NEVER be
mentioned explicitly since it is the default when the Distribution-
header is absent entirely. "All" MUST NOT be used as a
distribution-name. Distribution-names SHOULD contain at least three
characters, except when they are two-letter country names as in [ISO
3166]. Distribution-names are case-insensitive (i.e. "US", "Us" and
"us" all specify the same distribution).
Posting agents Ought Not to provide a default Distribution-header
without giving the poster an opportunity to override it. Followup
agents SHOULD initially supply the same Distribution-header as found
in the precursor.
6.7. Followup-To
The Followup-To-header specifies which newsgroup(s) followups should
be posted to.
header =/ Followup-To-header
Followup-To-header = "Followup-To" ":" SP Followup-To-content
*( ";" extension-parameter )
Followup-To-content = Newsgroups-content /
[FWS] %x70.6F.73.74.65.72 [FWS]
; which is a case-sensitive "poster"
The syntax is the same as that of the Newsgroups-content, with the
addition that the keyword "poster" is allowed. In the absence of a
Followup-To-header, the default newsgroup(s) for a followup are those
in the Newsgroups-header, and for this reason the Followup-To-header
SHOULD NOT be included if it just duplicates the Newsgroups-header.
A Followup-To-header consisting of the keyword "poster" indicates
that the poster requests no followups to be sent in response to this
article, only personal replies to the article's reply address.
Although the keyword "poster" is case-sensitive, followup agents MAY
choose to regognize case insensitive forms such as "Poster".
NOTE: A poster who wishes both a personal reply and a followup
post should include an appropriate Mail-Copies-To-header (6.8).
6.8. Mail-Copies-To
The Mail-Copies-To-header indicates whether or not the poster wishes
to have followups to an article emailed in addition to being posted
to Netnews and, if so, establishes the address to which they should
be sent.
The content syntax makes use of syntax defined in [RFC 2822], but
subject to the revised definition of local-part given in section 5.2.
header =/ Mail-Copies-To-header
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Mail-Copies-To-header
= "Mail-Copies-To" ":" SP Mail-Copies-To-content
Mail-Copies-To-content
= copy-addr / [CFWS] ( "nobody" / "poster" ) [CFWS]
copy-addr = address-list
The keyword "nobody" indicates that the poster does not wish copies
of any followup postings to be emailed. This indication is widely
seen as a very strong wish, and is to be taken as the default when
this header is absent.
The keyword "poster" indicates that the poster wishes a copy of any
followup postings to be emailed to him.
Otherwise, this header contains a copy-addr to which the poster
wishes a copy of any followup postings to be sent.
NOTE: Some existing practice uses the keyword "never" in place
of "nobody" and "always" in place of "poster". These usages are
deprecated, but followup agents MAY observe them.
The automatic actions of a followup agent in the various cases
(subject to manual override by the user) are as follows:
nobody (or when the header is absent)
The followup agent SHOULD NOT, by default, email such a copy and
Ought, especially when there is an explicit "nobody", to issue a
warning and ask for confirmation if the user attempts to do so.
poster
The followup agent Ought, by default, to email a copy, which MUST
then be sent to the address(es) in the Reply-To-header, and in the
absence of that to the address(es) in the From-header.
copy-addr
The followup agent Ought, by default, to email a copy, which MUST
then be sent to the copy-addr.
NOTE: This header is only relevant when posting followups to
Netnews articles, and is to be ignored when sending pure email
replies to the poster, which are handled as prescribed under the
Reply-To-header (6.1). Whether or not this header will also
find similar usage for replies to messages sent to mailing lists
falls outside the scope of this standard.
When emailing a copy, the followup agent SHOULD also include a
"Posted-And-Mailed: yes" header (6.9).
NOTE: In addition to the Posted-And-Mailed-header, some followup
agents also include within the body a mention that the article
is both posted and mailed, for the benefit of reading agents
that do not normally show that header.
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6.9. Posted-And-Mailed
header =/ Posted-And-Mailed-header
Posted-And-Mailed-header
= "Posted-And-Mailed" ":" SP Posted-And-Mailed-content
*( ";" extension-parameter )
Posted-And-Mailed-content
= [CFWS] ( "yes" / "no" ) [CFWS]
This header, when used with the "yes" keyword, indicates that the
article has been both posted to the specified newsgroups and emailed.
It SHOULD be used when replying to the poster of an article to which
this one is a followup (see the Mail-Copies-To-header in section 6.8)
and it MAY be used when any article is also mailed to a recipient(s)
identified in a To- and/or Cc-header that is also present. The "no"
keyword is included for the sake of completeness; it MAY be used to
indicate the opposite state, but is redundant insofar as it only
describes the default state when this header is absent.
This header, if present, MUST be included in both the posted and
emailed versions of the article. The Newsgroups-header of the posted
article SHOULD be included in the email version as recommended in
section 5.5. All other headers defined in this standard (excluding
variant headers) MUST be identical in both the posted and mailed
versions of the article, except that where they contain UTF8-xtra-
chars, which in the mailed version MUST, to comply with section
8.8.1.1, be encoded according to [RFC 2047] or [RFC 2231], or (in the
case of headers containing a newsgroup-name) to section 5.5.2, they
MAY, in the posted version, remain in UTF-8. The bodies MUST be
identical in both, apart from a possible change of Content-Transfer-
Encoding.
NOTE: This leaves open the question of whether a To- or a Cc-
header should appear in the posted version. Naturally, a Bcc-
header should not appear, except in a form which indicates that
there are additional unspecified recipients.
6.10. References
The References-header lists CFWS-separated message identifiers of
precursors. The content syntax makes use of syntax defined in [RFC
2822], subject to the same revisions as in section 5.3.
header =/ References-header
References-header = "References" ":" SP References-content
References-content = [CFWS] msg-id *( CFWS msg-id ) [CFWS]
NOTE: This differs from the syntax of [RFC 2822] by requiring at
least one CFWS between the msg-ids (a SP at this point was an
[RFC 1036] requirement).
A followup MUST have a References-header, and an article that is not
a followup MUST NOT have a References-header. In a followup, if the
precursor did not have a References-header, the followup's
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References-content MUST be formed by the message identifier of the
precursor. A followup to an article which had a References-header
MUST have a References-header containing the precursor's References-
content (subject to trimming as described below) plus the precursor's
message identifier appended to the end of the list (separated from it
by CFWS).
Followup agents SHOULD NOT trim message identifiers out of a
References-header unless the number of message identifiers exceeds
21, at which time trimming SHOULD be done by removing sufficient
identifiers starting with the second so as to bring the total down to
21 (but the first message identifier MUST NOT be trimmed). However,
it would be wrong to assume that References-headers containing more
than 21 message identifiers will not occur.
6.10.1. Examples
References: <i4g587y@site1.example>
References: <i4g587y@site1.example> <kgb2231+ee@site2.example>
References: <i4g587y@site1.example> <kgb2231+ee@site2.example>
<222@site1.example> <87tfbyv@site7.example>
<67jimf@site666.example>
References: <i4g587y@site1.example> <kgb2231+ee@site2.example>
<tisjits@smeghead.example>
6.11. Expires
The Expires-header specifies a date and time when the article is
deemed to be no longer relevant and could usefully be removed
("expired"). The content syntax makes use of syntax defined in [RFC
2822].
header =/ Expires-header
Expires-header = "Expires" ":" SP Expires-content
*( ";" extension-parameter )
Expires-content = date-time
An Expires-header should only be used in an article if the requested
expiry time is earlier or later than the time typically to be
expected for such articles. Local policy for each serving agent will
dictate whether and when this header is obeyed and posters SHOULD NOT
depend on it being completely followed.
6.12. Archive
This optional header provides an indication of the poster's intent
regarding preservation of the article in publicly accessible long-
term or permanent storage.
header =/ Archive-header
Archive-header = "Archive" ":" SP Archive-content
*( ";" ( Archive-parameter /
extension-parameter ) )
Archive-content = [CFWS] ("no" / "yes" ) [CFWS]
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Archive-parameter = <a parameter with attribute "filename"
and any value>
The presence of an "Archive: no" header in an article indicates that
the poster does not permit redistribution from publicly accessible
long-term or permanent archives. The absence of this header, or an
explicit "Archive: yes", indicates that the poster is willing for
such redistribution to take place. The optional "filename" parameter
can then be used to suggest a filename under which the article should
be stored. Further extensions to this standard may provide additional
parameters for administration of the archiving process.
NOTE: This standard does not attempt to define the length of
"long-term", since it is dependent on many factors, including
the retention policies of individual sites, and the customs or
policies established for particular newsgroups or hierarchies.
NOTE: Posters are cautioned that some sites may not implement
the "no" option of the Archive-header correctly. In some
jurisdictions non-compliance with this header may constitute a
breach of copyright or of other legal provisions. Moreover,
even if this header prevents the poster's words from being
archived publicly, it does nothing to prevent the archiving of a
followup in which those words are quoted.
6.13. Control
The Control-header marks the article as a control message, and
specifies the desired actions (additional to the usual ones of
storing and/or relaying the article).
header =/ Control-header
Control-header = "Control" ":" SP Control-content
*( ";" extension-parameter )
Control-content = [CFWS] control-message [CFWS]
control-message = <empty>
However, the rule given above for control-message is incomplete.
Further alternatives will be added incrementally as the various
control-messages are introduced in section 7, or in extensions to
this standard, using the "=/" notation defined in [RFC 2234]. For
example, a typical CONTROL-message would be defined as follows:
control-message =/ CONTROL-message
CONTROL-message = "CONTROL" CONTROL-arguments
CONTROL-arguments = <the argument(s) specific to that
CONTROL-message>
where "CONTROL" is a "verb" which is (and MUST be) of the syntactic
form of a token and CONTROL-arguments MUST be of the syntactic form
of a CFWS-separated list of values (which may require the use of
quoted-strings if any tspecials or non-ASCII characters are
involved).
C. H. Lindsey [Page 54]
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The verb indicates what action should be taken, and the argument(s)
(if any) supply details. In some cases, the body of the article may
also contain details.
An article with a Control-header MUST NOT also have a Supersedes-
header.
NOTE: The presence of a Subject-header starting with the string
"cmsg " and followed by a Control-message MUST NOT be construed,
in the absence of a proper Control-header, as a request to
perform that control action (as may have occurred in some legacy
software). See also section 5.4.
6.14. Approved
The Approved-header indicates the mailing addresses (possibly
including the full names) of the persons or entities approving the
article for posting.
header =/ Approved-header
Approved-header = "Approved" ":" SP Approved-content
*( ";" extension-parameter )
Approved-content = From-content ; see 5.2
Each mailbox contained in the Approved-content MUST be that of one of
the person(s) or entity(ies) in question, and one of those mailboxes
MUST be that of the actual injector of the article.
An Approved-header is required in all postings to moderated
newsgroups. If this header is not present in such postings, then
serving agents MUST (and relaying agents MAY) reject the article.
Please see section 8.2.2 for how injecting agents should treat
postings to moderated groups that do not contain this header.
An Approved-header is also required in certain control messages, to
reduce the risks of accidental or unauthorized posting of same.
NOTE: The presence of an Approved-header indicates that the
person or entity identified claims to have the necessary
authority to post the article in question, thus enabling sites
that dispute that authority to refuse to accept or to act upon
it. However, the mere presence of the header is insufficient to
provide assurance that it indeed originated from that person or
entity, and it is therefore desirable that it be included within
some digital signature scheme (see 7.1), especially in the case
of control messages (section 7).
6.15. Supersedes
The Supersedes-header contains a message identifier specifying an
article to be superseded upon the arrival of this one. The specified
article MUST be treated as though a "cancel" control message had
arrived for the article (but observe that a site MAY choose not to
honour a "cancel" message, especially if its authenticity is in
C. H. Lindsey [Page 55]
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doubt). The content syntax makes use of syntax defined in [RFC 2822],
subject to the same revisions as in 5.3.
header =/ Supersedes-header
Supersedes-header = "Supersedes" ":" SP Supersedes-content
Supersedes-content = [CFWS] msg-id [CFWS]
NOTE: There is no "c" in "Supersedes".
NOTE: The Supersedes-header defined here has no connection with
the Supersedes-header that sometimes appears in Email messages
converted from X.400 according to [RFC 2156]; in particular, the
syntax here permits only one msg-id in contrast to the multiple
msg-ids in that Email version.
Thus when an article contains a Supersedes-header, the old article
mentioned SHOULD be withdrawn from circulation or access, as in a
cancel message (7.3), and the new article inserted into the system as
any other new article would have been.
Whatever security or authentication checks are normally applied to a
Control cancel message (or may be prescribed for such messages by
some extension to this standard - see the remarks in 7.1 and 7.3)
MUST also be applied to an article with a Supersedes-header. In the
event of the failure of such checks, the article SHOULD be discarded,
or at most stored as an ordinary article.
6.16. Xref
The Xref-header is a variant header (4.2.5.3) which indicates where
an article was filed by the last serving agent to process it.
header =/ Xref-header
Xref-header = "Xref" ":" SP Xref-content
*( ";" extension-parameter )
Xref-content = [CFWS] server-name 1*( CFWS location ) [CFWS]
server-name = path-identity ; see 5.6.1
location = newsgroup-name ":" article-locator
article-locator = 1*( %x21-27 / %x29-3A / %x3C-7E )
; US-ASCII printable characters
; except '(' and ';'
The server-name is included so that software can determine which
serving agent generated the header. The locations specify what
newsgroups the article was filed under (which may differ from those
in the Newsgroups-header) and where it was filed under them. The
exact form of an article-locator is implementation-specific.
NOTE: The traditional form of an article-locator is a decimal
number, with articles in each newsgroup numbered consecutively
starting from 1. NNTP demands that such a model be provided, and
much other software expects it, but it seems desirable to permit
flexibility for unorthodox implementations.
C. H. Lindsey [Page 56]
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An agent inserting an Xref-header into an article MUST delete any
previous Xref-header(s). A relaying agent MAY delete it before
relaying, but otherwise it SHOULD be ignored by any relaying or
serving agent receiving it.
It is convenient, though not required, for a serving agent to use the
same server-name in Xref-headers as the path-identity it uses in
Path-headers (just so long as reading agents can distinguish it from
other serving agents known to them).
6.17. Lines
The Lines-header indicates the number of lines in the body of the
article.
header =/ Lines-header
Lines-header = "Lines" ":" SP Lines-content
*( ";" extension-parameter )
Lines-content = [CFWS] 1*DIGIT [CFWS]
The line count includes all body lines, including the signature if
any, including empty lines (if any) at the beginning or end of the
body, and including the whole of all MIME message and multipart parts
contained in the body (the single empty separator line between the
headers and the body is not part of the body). The "body" here is the
body as found in the posted article as transmitted by the posting
agent.
This header is to be regarded as obsolete, and it will likely be
removed entirely in a future version of this standard. In the
meantime, its use is deprecated.
6.18. User-Agent
The User-Agent-header contains information about the user agent
(typically a newsreader) generating the article, for statistical
purposes and tracing of standards violations to specific software
needing correction. Although not one of the mandatory headers,
posting agents SHOULD normally include it. It is also intended that
this header be suitable for use in Email.
header =/ User-Agent-header
User-Agent-header = "User-Agent" ":" SP User-Agent-content
*( ";" extension-parameter )
User-Agent-content = product *( CFWS product )
product = [CFWS] token [CFWS] [ "/" product-version ]
product-version = [CFWS] token [CFWS]
This header MAY contain multiple product-tokens identifying the agent
and any subproducts which form a significant part of the posting
agent, listed in order of their significance for identifying the
application. Product-tokens should be short and to the point - they
MUST NOT be used for information beyond the canonical name of the
product and its version. Injecting agents MAY include product
C. H. Lindsey [Page 57]
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information for themselves (such as "INN/1.7.2"), but relaying and
serving agents MUST NOT generate or modify this header to list
themselves.
NOTE: A product, being composed of a token, can contain only
US-ASCII characters. Where the full name of an agent is
expressed in a language requiring non-ASCII characters, it is
suggested that an arbitrary (but easily recognizable) US_ASCII
token be provided, followed by the full name in the form of a
comment.
NOTE: Minor variations from [RFC 2616] which describes a similar
facility for the HTTP protocol:
1. "{" and "}" are allowed in a token (product and product-
version) in Netnews,
2. Comments are permitted wherever whitespace is allowed.
NOTE: Comments should be restricted to information regarding the
product named to their left, such as its full name or platform
information, and should be concise. Use as an advertising medium
(in the mundane sense) is discouraged.
6.18.1. Examples
User-Agent: tin/1.2-PL2
User-Agent: tin/1.3-950621beta-PL0 (Unix)
User-Agent: tin/unoff-1.3-BETA-970813 (UNIX) (Linux/2.0.30 (i486))
User-Agent: tin/pre-1.4-971106 (UNIX) (Linux/2.0.30 (i486))
User-Agent: Mozilla/4.02b7 (X11; I; en; HP-UX B.10.20 9000/712)
User-Agent: Microsoft-Internet-News/4.70.1161
User-Agent: Gnus/5.4.64 XEmacs/20.3beta17 ("Bucharest")
User-Agent: Pluto/1.05h (RISC-OS/3.1) NewsHound/1.30
User-Agent: inn/1.7.2
User-Agent: telnet
NOTE: This header supersedes the role performed redundantly by
experimental headers such as X-Newsreader, X-Mailer, X-Posting-
Agent, X-Http-User-Agent, and other headers previously used on
Usenet and in Email for this purpose. Use of these experimental
headers SHOULD be discontinued in favor of the single, standard
User-Agent-header.
6.19. Injector-Info
The Injector-Info-header SHOULD be added to each article by the
injecting agent in order to provide information as to how that
article entered the Netnews system and to assist in tracing its true
origin.
header =/ Injector-Info-header
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Injector-Info-header
= "Injector-Info" ":" SP Injector-Info-content
*( ";" ( Injector-Info-parameter /
extension-parameter ) )
Injector-Info-content
= [CFWS] path-identity [CFWS]
Injector-Info-parameter
= posting-host-parameter /
posting-account-parameter /
posting-sender-parameter /
posting-logging-parameter /
posting-date-parameter
; for {USENET}-parameters see 4.1
posting-host-parameter
= <a parameter with attribute "posting-host"
and value some host-value>
host-value = dot-atom /
[ dot-atom ":" ]
( IPv4address / IPv6address ); see [RFC 2373]
posting-account-parameter
= <a parameter with attribute "posting-account"
and any value>
posting-sender-parameter
= <a parameter with attribute "sender"
and value some sender-value>
sender-value = mailbox / "verified"
posting-logging-parameter
= <a parameter with attribute "logging-data"
and any value>
posting-date-parameter
= <a parameter with attribute "posting-date"
and value some date-time>
An Injector-Info-header MUST NOT be added to an article by any agent
other than an injecting agent. Any Injector-Info-header present when
an article arrives at an injecting agent MUST be removed. In
particular if, for some exceptional reason (8.2.2), an article gets
injected twice, the Injector-Info-header will always relate to the
second injection.
The path-identity MUST be the same as the path-identity prepended to
the Path-header by that same injecting agent which, following section
5.6.2, MUST therefore be a fully qualified domain name (FQDN)
mailable address.
Although comments and folding of white space are permitted throughout
the Injector-Info-content specification, it is RECOMMENDED that
folding is not used within any parameter (but only before or after
the ";" separating those parameters), and that comments are only used
following the last parameter. It is also RECOMMENDED that such
parameters as are present are included in the order in which they
have been defined in the syntax above. An injecting agent SHOULD use
a consistent form of this header for all articles emanating from the
same or similar origins.
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NOTE: The effect of those recommendations is to facilitate the
recognition of articles arising from certain designated origins
(as in the so-called "killfiles" which are available in some
reading agents). Observe that the order within the syntax has
been chosen to place last those parameters which are most likely
to change between successive articles posted from the same
origin.
NOTE: To comply with the overall "attribute = value" syntax of
parameters, any value containing an IPv6address, a date-time, a
mailbox, any UTF8-xtra-char, or any CFWS MUST be quoted using
<DQUOTE>s (the quoting is optional in other cases).
NOTE: This header is intended to replace various currently-used
but nowhere-documented headers such as "NNTP-Posting-Host",
"NNTP-Posting-Date" and "X-Trace". These headers are now
deprecated, and any of them present when an article arrives at
an injecting agent SHOULD also be removed as above.
6.19.1. Usage of Injector-Info-parameters
The purpose of these parameters is to enable the injecting agent to
make assertions about the origin of the article, in fulfilment of its
responsibilities towards the rest of the network as set out in
section 8.2. These assertions can then be utilized as follows:
1. To enable the administrator of the injecting agent to respond to
complaints and queries concerning the article. For this purpose,
the parameters included SHOULD be sufficient to enable the
administrator to identify its true origin (which parameters are
best suited to this purpose will vary with the nature of the
injecting site and of its relationship to the posters who use it -
there is no benefit in including parameters which contribute
nothing to this aim). An administrator MAY, with those parameters
where the syntax so allows, use cryptic notations interpretable
only by himself if he considers it appropriate to protect the
privacy of that origin.
2. To enable relaying, serving and reading agents to recognize
articles from origins which they might wish to reject, divert, or
otherwise handle specially, for reasons of site policy.
3. To enable the timely identification of spews of articles arising
from a common origin.
An injecting agent MUST NOT include any Injector-Info-parameter
unless it has positive evidence of its correctness. An injecting
agent MAY include extension-parameters with x-token attributes which
will assist in identifying the origin of the article.
NOTE: Administrators of injecting agents can choose which
selection of the following parameters best enables them to fulfil
their responsibilities. Some of these parameters identify the
source of the article explicitly whereas others do so indirectly,
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thus affording more privacy to posters who value their anonymity,
but also making harder the tracking of malicious disruption of the
network, especially so if the administrators choose not to
cooperate. There is thus a balance to be struck between the needs
of privacy on the one hand and the good order of Usenet on the
other, and administrators need to be aware of this when
formulating their policies.
6.19.1.1. The posting-host-parameter
If a dot-atom is present, it MUST be a FQDN identifying the specific
host from which the injecting agent received the article.
Alternatively, an IP address (IPv4address or IPv6address) identifies
that host. If both forms are present, then they MUST identify the
same host, or at least have done so at the time the article was
injected.
NOTE: It is commonly the case that this parameter identifies a
dial-up point-of-presence, in which case a posting-account or
logging-data may need to be consulted to find the true origin of
the article.
6.19.1.2. The posting-account-parameter
This parameter identifies the source from which the injecting agent
received the article. It SHOULD be in a cryptic notation
understandable only by the administrator of the injecting agent, but
it MUST be such that a given source gives rise to the same posting-
account, at least in the short term. If the injecting agent is unable
to meet that obligation, then it should use a posting-logging-
parameter instead.
6.19.1.3. The posting-sender-parameter
This parameter identifies the mailbox of the verified sender of the
article (alternatively, it uses the token "verified" to indicate that
at least any addr-spec in the Sender-header of the article, or in the
From-header if the Sender-header is absent, is correct).
NOTE: An injecting agent is unlikely to be able to make use of
this parameter except in cases where it is running on a machine
which is aware of the user-space in which the posting agent is
operating. This parameter should be used in preference to a
posting-account-parameter in such situations.
6.19.1.4. The posting-logging-parameter
This parameter contains information (typically a session number or
other non-persistent means of identifying a posting account) which
will enable the true origin of the article to be determined by
reference to logging information kept by the injecting agent.
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6.19.1.5. The posting-date-parameter
This parameter identifies the time at which the article was injected
(as distinct from the Date-header, which indicates when it was
written).
6.19.2. Example
Injector-Info: news2.isp.net; posting-host=modem-15.pop.isp.net;
posting-account=client0002623; logging-data=2427;
posting-date="Wed, 2 Aug 2000 20:05:33 -0100 (BST)"
6.20. Complaints-To
The Complaints-To-header is added to an article by an injecting agent
in order to indicate the mailbox to which complaints concerning the
poster of the article may be sent.
header =/ Complaints-To-header
Complaints-To-header
= "Complaints-To" ":" SP Complaints-To-content
Complaints-To-content
= address-list
A Complaints-To-header MUST NOT be added to an article by any agent
other than an injecting agent. Any Complaints-To-header present when
an article arrives at an injecting agent MUST be removed. In
particular if, for some exceptional reason (8.2.2), an article gets
injected twice, the Complaints-To-header will always relate to the
second injection.
The specified mailbox is for sending complaints concerning the
behaviour of the poster of the article; it SHOULD NOT be used for
matters concerning propagation, protocol problems, etc. which should
be addressed to "usenet@" or "news@" the path-identity which was
prepended to the Path-header by the injecting agent, in accordance
with section 5.6.2. In the absence of this header, complaints
concerning a poster's behaviour MAY be addressed to "abuse@" that
path-identity (although section 5.6.2 provides no obligation for that
address to be mailable at an injecting agent that is not provided for
the use of the general public).
6.21. MIME headers
6.21.1. Syntax
The following headers may be used within articles conforming to this
standard.
MIME-Version: [RFC 2045]
Content-Type: [RFC 2045],[RFC 2046]
Content-Transfer-Encoding: [RFC 2045]
Content-ID: [RFC 2045]
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Content-Description: [RFC 2045]
Content-Disposition: [RFC 2183]
Content-Location: [RFC 2557]
Content-Language: [RFC 3282]
Content-MD5: [RFC 1864]
The RFCs listed are deemed to be incorporated into this standard to
the extent necessary to facilitate their usage within Netnews,
subject to the revised syntax of parameter given in this standard
(which permits UTF-xtra-chars to appear within quoted-strings used as
values), and subject to curtailment of that usage as described in the
following sections. Moreover, extensions to those standards
registered in accordance with [RFC 2048] are also available for use
within Netnews, as indeed is any other header in the Content-* series
which has a sensible interpretation within Netnews.
Insofar as the syntax for these headers, as given in those RFCs does
not specify precisely where whitespace and comments may occur
(whether in the form of WSP, FWS or CFWS), the usage defined in this
standard, and failing that in [RFC 2822], and failing that in [RFC
822] MUST be followed. In particular, there MUST NOT be any WSP
between a header-name and the following colon and there MUST be a SP
following that colon.
6.21.2. Content-Type
If the contents of an article is something other than plain text in
the US-ASCII charset (these being the default assumptions), an
appropriate Content-Type-header MUST be included.
When the Content-Type is "text/plain", the recommendations and limits
on line lengths set out in section 4.5 Ought to be observed.
The acceptability of other subtypes of Content-Type: "text" (such as
"text/html") is a matter of policy (see 1.1), and posters Ought Not
to use them unless established policy or custom in the particular
hierarchies or groups involved so allows. Moreover, even in those
cases, for the benefit of readers who see it only in its transmitted
form, the material SHOULD be "pretty-printed" (for example by
restricting its line length as above and by keeping sequences which
control its layout or style separate from the meaningful text).
In the same way, Content-Types requiring special processing for their
display, such as "application", "image", "audio", "video" and
"multipart/related" are discouraged except in groups specifically
intended (by policy or custom) to include them. Exceptionally, those
application types defined in [RFC 1847] and [RFC 3156] for use within
"multipart/signed" articles, and the type "application/pgp-keys" (or
other similar types containing digital certificates) may be used
freely.
Reading agents SHOULD NOT, unless explicitly configured otherwise,
act automatically on Application types which could change the state
of that agent (e.g. by writing or modifying files), except in the
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case of those prescribed for use in control messages (7.2.1.2 and
7.2.4.1).
6.21.2.1. Message/partial
The Content-Type "message/partial" MAY be used to split a long news
article into several smaller ones.
NOTE: This Content-Type is not recommended for textual articles
because the Content-Type, and in particular the charset, of the
complete article cannot be determined by examination of the
second and subsequent parts, and hence it is not possible to
read them as separate articles (except when they are written in
pure US-ASCII). Moreover, for full compliance with [RFC 2046] it
would be necessary to use the "quoted-printable" encoding to
ensure the material was 7bit-safe. In any case, breaking such
long texts into several parts is usually unnecessary, since
modern transport agents should have no difficulty in handling
articles of arbitrary length.
On the other hand, "message/partial" may be useful for binaries
of excessive length, since reading of the individual parts on
their own is not required and they would likely be encoded in a
manner that was 7bit-safe.
IF this Content-Type is used, then the "id" parameter SHOULD be in
the form of a unique message identifier (but different from that in
the Message-ID-header of any of the parts). The second and subsequent
parts SHOULD contain References-headers referring to all the previous
parts, thus enabling reading agents with threading capabilities to
present them in the correct order. Reading agents MAY then provide a
facility to recombine the parts into a single article (but this
standard does not require them to do so).
6.21.2.2. Message/rfc822
The Content-Type "message/rfc822" should be used for the
encapsulation (whether as part of another news article or, more
usually, as part of an email message) of complete news articles which
have already been posted to Netnews and which are for the information
of the recipient, and do not constitute a request to repost them
(refer to 6.21.6.2 for the now obsolete "message/news" formerly
intended for this purpose).
In the case where such an encapsulated news article is to be
transported by email and it has Content-Transfer-Encoding "8bit", the
Content-Transfer-Encoding may need to be changed, although there
should be no problems if the email transport supports 8BITMIME [RFC
2821]. If, however, its headers contain any UTF8-xtra-chars (2.4.2),
the requirements on transformations given in section 8.8.1.1 MUST be
followed. It may be necessary to reverse these changes at the far end
if certain forms of digital signature have been employed in the
article.
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6.21.2.3. Message/external-body
The Content-Type "message/external-body" could be appropriate for
texts which it would be uneconomic (in view of the likely readership)
to distribute to the entire network.
6.21.2.4. Multipart types
The Content-Types "multipart/mixed", "multipart/parallel" and
"multipart/signed" may be used freely in news articles. However,
except where policy or custom so allows, the Content-Type:
"multipart/alternative" SHOULD NOT be used, on account of the extra
bandwidth consumed and the difficulty of quoting in followups, but
reading agents MUST accept it.
The Content-Type: "multipart/digest" is commended for any article
composed of multiple messages more conveniently viewed as separate
entities, thus enabling reading agents to move rapidly between them.
The "boundary" should be composed of 28 hyphens (US-ASCII 45) (which
makes each boundary delimiter 30 hyphens, or 32 for the final one) so
as to enable reading agents which currently support the digest usage
described in [RFC 1153] to continue to operate correctly.
NOTE: The various recommendations given above regarding the
usage of particular Content-Types apply also to the individual
parts of these multiparts.
6.21.3. Content-Transfer-Encoding
"Content-Transfer-Encoding: 7bit" is sufficient for article bodies
(or parts of multiparts) written in pure US-ASCII (or most other
material representable in 7 bits). Posting agents SHOULD specify
"Content-Transfer-Encoding: 8bit" for all other cases unless there
are pressing reasons to do otherwise. They MAY use "8bit" encoding
even when "7bit" encoding would have sufficed. Examples of such
pressing reasons are the following:
1. The content type implies that the content is (or may be) "8bit-
unsafe"; i.e. it may contain octets equivalent to the US-ASCII
characters CR or LF (other than in the combination CRLF) or NUL.
In that case one of the Content-Transfer-Encodings "base64" or
"quoted-printable" MUST be used, and reading agents MUST be able
to handle both of them. Encoding "binary" MUST NOT be used (except
in cooperating subnets with alternative transport arrangements)
because this standard does not mandate a transport mechanism that
could support it.
NOTE: If a future extension to the MIME standards were to
provide a more compact encoding of binary suited to transport
over an 8bit channel, it could be considered as an alternative
to base64 once it had gained widespread acceptance.
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2. It is often the case that "application" Content-Types are textual
in nature, and intelligible to humans as well as to machines, and
where this state can be recognized by the posting agent (either
through knowledge of the particular application type or by
testing) the material SHOULD NOT be treated as 8bit-unsafe; this
has the added benefit, where the posting agent uses other than
CRLF for line endings internally, of automatically ensuring that
line endings are processed correctly during transport.
If, on the other hand, the posting agent recognizes that the
material is not textual, or cannot reasonably determine it to be
so, then the material MUST be encoded as for 8bit-unsafe (however,
in that case, it is the responsibility of the agent generating the
material to ensure that lines endings, if any, are represented
correctly).
NOTE: All the application types defined by this standard, namely
"application/news-transmission", "application/news-groupinfo"
and "application/news-checkgroups" are textual, and indeed
designed for human reading.
3. Although the "text" Content-Types should normally be encoded as
8bit (or 7bit), if the character set specified by the "charset="
parameter can include the 3 disallowed octets, then the material
MUST be encoded as for 8bit-unsafe. This is most likely to arise
in the case of 16-bit character sets such as UTF-16 ([UNICODE 3.2]
or [ISO/IEC 10646]). In addition, where it is known that the
material is subsequently to be gatewayed from Netnews to Email
(8.8), the encoding "quoted-printable" MAY be used (otherwise the
gateway might have to re-encode it itself).
4. Some protocols REQUIRE the use of a particular Content-Transfer-
Encoding. In particular, the authentication protocol based on
OpenPGP defined in [RFC 3156] mandates the use of one of the
encodings "quoted-printable" or "base64". Whilst posters might be
tempted to risk the use of "8bit" or "7bit" encodings (and indeed
the referenced standard recommends that signed messages using
those encodings be accepted and interpreted), they should be
warned that differences in the treatment of trailing whitespace
between OpenPGP [RFC 2440] and earlier versions of PGP may render
signatures written with the one unverifiable by the other; and,
moreover, Usenet articles are very likely to include trailing
whitespace in the form of a personal signature (4.3.2).
5. The Content-Type message/partial [RFC 2046] is required to use
encoding "7bit" (the encapsulated complete message may itself use
encoding "quoted-printable" or "base64", but that information is
only conveyed along with the first of the partial parts).
NOTE: Although there would actually be no problem using encoding
"8bit" in a pure Netnews (as opposed to Email) environment, this
standard discourages (see 6.21.2.1) the use of "message/partial"
except for binary material, which will likely be encoded to pass
through "7bit" in any case.
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Injecting and relaying agents MUST NOT change the encoding of
articles passed to them. Gateways SHOULD NOT change the encoding
unless absolutely necessary.
6.21.4. Character Sets
In principle, any character set may be specified in the "charset="
parameter of a content type. However, only those character sets (and
the corresponding parts of UTF-8) should be used which are
appropriate for the customary language(s) of the hierarchy or
newsgroup concerned (whose readers could be expected to possess
agents capable of displaying them).
6.21.5. Content Disposition
Reading agents Ought to honour any Content-Disposition-header that is
provided (in particular, they Ought to display any part of a
multipart for which the disposition is "inline", possibly
distinguished from adjacent parts by some suitable separator). In the
absence of such a header, the body of an article or any part of a
multipart with Content-Type "text" Ought to be displayed inline.
Followup agents which quote parts of a precursor (see 4.3.2) Ought
initially to include all parts of the precursor that were displayed
inline, as if they were a single part.
6.21.6. Definition of some new Content-Types
This standard defines (or redefines) several new Content-Types, which
require to be registered with IANA as provided for in [RFC 2048].
For "application/news-groupinfo" see 7.2.1.2, for "application/news-
checkgroups" see 7.2.4.1, and for "application/news-transmission" see
the following section.
6.21.6.1. Application/news-transmission
The Content-Type "application/news-transmission" is intended for the
encapsulation of complete news articles where the intention is that
the recipient should then inject them into Netnews. This Application
type provides one of the methods for mailing articles to moderators
(see 8.2.2) and it is also the preferred method when sending to an
email-to-news gateway (see 8.8.2).
NOTE: The benefit of such encapsulation is that it removes
possible conflict between news and email headers and it provides
a convenient way of "tunnelling" a news article through a
transport medium that does not support 8bit characters.
The MIME content type definition of "application/news-transmission"
is:
MIME type name: application
MIME subtype name: news-transmission
Required parameters: none
Optional parameters: usage=moderate
C. H. Lindsey [Page 67]
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usage=inject
usage=relay
Encoding considerations: A transfer-encoding (such as Quoted-
Printable or Base64) different from that of
the article transmitted MAY be supplied
(perhaps en route) to ensure correct
transmission over some 7bit transport
medium.
Security considerations: A news article may be a "control message",
which could have effects on the recipient
host's system beyond just storage of the
article. However, such control messages
also occur in normal news flow, so most
hosts will already be suitably defended
against undesired effects.
Published specification: [USEFOR]
Body part: A complete article or proto-article, ready
for injection into Netnews, or a batch of
such articles.
NOTE: It is likely that the recipient of an "application/news-
transmission" will be a specialized gateway (e.g. a moderator's
submission address) able to accept articles with only one of the
three usage parameters "moderate", "inject" and "relay", hence
the reason why they are optional, being redundant in most
situations. Nevertheless, they MAY be used to signify the
originator's intention with regard to the transmission, so
removing any possible doubt.
When the parameter "relay" is used, or implied, the body part MAY be
a batch of articles to be transmitted together, in which case the
following syntax MUST be used.
batch = 1*( batch-header article )
batch-header = "#!" SP rnews SP article-size CRLF
rnews = %x72.6E.65.77.73 ; case sensitive "rnews"
article-size = 1*DIGIT
Thus a batch is a sequence of articles, each prefixed by a header
line that includes its size. The article-size is a decimal count of
the octets in the article, counting each CRLF as one octet regardless
of how it is actually represented.
NOTE: Despite the similarity of this format to an executable
UNIX script, it is EXTREMELY unwise to feed such a batch into a
command interpreter in anticipation of it running a command
named "rnews"; the security implications of so doing would be
disastrous.
6.21.6.2. Message/news obsoleted
The Content-Type "message/news", as previously registered with IANA,
is hereby declared obsolete. It was never widely implemented, and its
default treatment as "application/octet-stream" by agents that did
C. H. Lindsey [Page 68]
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not recognize it was counter productive. The Content-Type
"message/rfc822" SHOULD be used in its place, as already described
above.
6.22. Obsolete Headers
Persons writing new agents SHOULD ignore any former meanings of the
following headers:
Also-Control
See-Also
Article-Names
Article-Updates
7. Control Messages
The following sections document the control messages. "Message" is
used herein as a synonym for "article" unless context indicates
otherwise.
The Newsgroups-header of each control message SHOULD include the
newsgroup-name(s) for the group(s) affected (i.e. groups to be
created, modified or removed, or containing articles to be canceled).
This is to ensure that the message propagates to all sites which
receive (or would receive) that group(s). It MAY include other
newsgroup-names so as to improve propagation (but this practice may
cause the control message to propagate also to places where it is
unwanted, or even cause it not to propagate where it should, so it
should not be used without good reason).
The descriptions below set out REQUIREMENTS to be followed by sites
that receive control messages and choose to honour them. However,
nothing in these descriptions should be taken as overriding the right
of any such site, in accordance with its local policy, to deny any
particular control message, or to refer it to an administrator for
approval (either as a class or on a case-by-case basis). In
particular, sites Ought to deny messages not issued by the
appropriate administrative agencies, and therefore SHOULD take such
steps as are reasonably practicable to validate their authenticity
(see, for example, section 7.1 below).
Relaying Agents MUST propagate even control messages that they do not
recognize.
In the following sections, each type of control message is defined
syntactically by defining its verb, its arguments, and possibly its
body.
7.1. Digital Signature of Headers
It is most desirable that group control messages (7.2) in particular
be authenticated by incorporating them within some digital signature
scheme that encompasses other headers closely associated with them
(including at least the Approved-, Message-ID- and Date-headers). At
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the time of writing, this is usually done by means of a protocol
known as "PGPverify" ([PGPVERIFY]), and continued usage of this is
encouraged at least as an interim measure.
However, PGPverify is not considered suitable for standardization in
its present form, for various technical reasons. It is therefore
expected that an early extension to this standard will provide a
robust and general purpose digital authentication mechanism with
applicability to all situations requiring protection against
malicious use of, or interference with, headers. That extension
would also address other Netnews security issues.
7.2. Group Control Messages
"Group control messages" are the sub-class of control messages that
request some update to the configuration of the groups known to a
serving agent, namely "newgroup". "rmgroup", "mvgroup" and
"checkgroups", plus any others created by extensions to this
standard.
All of the group control messages MUST have an Approved-header
(6.14). Moreover, in those hierarchies where appropriate
administrative agencies exist (see 1.1), group control messages Ought
Not to be issued except as authorized by those agencies.
7.2.1. The 'newgroup' Control Message
control-message =/ Newgroup-message
Newgroup-message = "newgroup" Newgroup-arguments
Newgroup-arguments = CFWS newsgroup-name [ CFWS newgroup-flag ]
newgroup-flag = "moderated"
The "newgroup" control message requests that the specified group be
created or changed. If the request is honoured, or if the group
already exists on the serving agent, and if the newgroup-flag
"moderated" is present, then the group MUST be marked as moderated,
and vice versa. "Moderated" is the only such flag defined by this
standard; other flags MAY be defined for use in cooperating subnets,
but newgroup messages containing them MUST NOT be acted on outside of
those subnets.
NOTE: Specifically, some alternative flags such as "y" and "m",
which are sent and recognized by some current software, are NOT
part of this standard. Moreover, some existing implementations
treat any flag other than "moderated" as indicating an
unmoderated newsgroup. Both of these usages are contrary to this
standard and control messages with such non-standard flags
should be ignored.
The message body comprises or includes an "application/news-
groupinfo" (7.2.1.2) part containing machine- and human-readable
information about the group.
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It is REQUIRED that the newsgroup-name conforms to all requirements
set out in section 5.5. This includes the restrictions as to the
permitted characters, and the requirement that they be invariant
under NFKC normalization. It is essential that those who issue
newgroup messages are aware of their responsibility to enforce this
requirement, since some of those conditions are hard to enforce
mechanically.
Additionally, the newsgroup-name Ought to conform to whatever
policies have been established by the administrative agency, if any,
for that hierarchy. Serving agents SHOULD, insofar as they are
conveniently able to detect them, reject all newgroup messages not
meeting those requirements.
The newgroup command is also used to update the newsgroups-line or
the moderation status of a group.
7.2.1.1. The Body of the 'newgroup' Control Message
The body of the newgroup message contains the following subparts,
preferably in the order shown:
1. An "application/news-groupinfo" part (7.2.1.2) containing the name
and newsgroups-line of the group(s). This part MUST be present.
2. Other parts containing useful information about the background of
the newgroup message (typically of type "text/plain").
3. Parts containing initial articles for the newsgroup. See section
7.2.1.3 for details.
In the event that there is only the single (i.e. application/news-
groupinfo) subpart present, it will suffice to include a "Content-
Type: application/news-groupinfo" amongst the headers of the control
message. Otherwise, a "Content-Type: multipart/mixed" header will be
needed, and each separate part will then need its own Content-Type-
header.
7.2.1.2. Application/news-groupinfo
The "application/news-groupinfo" body part contains brief information
about a newsgroup, i.e. the group's name, it's newsgroup-description
and the moderation-flag.
NOTE: The presence of the newsgroups-tag "For your newsgroups
file:" is intended to make the whole newgroup message compatible
with current practice as described in [Son-of-1036].
The MIME content type definition of "application/news-groupinfo" is:
MIME type name: application
MIME subtype name: news-groupinfo
Required parameters: none
Disposition: by default, inline
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Encoding considerations: "7bit" or "8bit" is sufficient and MUST be
used to maintain compatibility.
Security considerations: this type MUST NOT be used except as part
of a control message for the creation or
modification of a Netnews newsgroup
Published specification: [USEFOR]
The content of the "application/news-groupinfo" body part is defined
as:
groupinfo-body = [ newsgroups-tag CRLF ]
newsgroups-line CRLF
newsgroups-tag = %x46.6F.72 SP %x79.6F.75.72 SP
%x6E.65.77.73.67.72.6F.75.70.73 SP
%x66.69.6C.65.3A
; case sensitive
; "For your newsgroups file:"
newsgroups-line = newsgroup-name
[ 1*HTAB newsgroup-description ]
[ 1*WSP moderation-flag ]
newsgroup-description
= utext *( *WSP utext )
moderation-flag = %x28.4D.6F.64.65.72.61.74.65.64.29
; case sensitive "(Moderated)"
The newsgroup-description MUST NOT contain any occurrence of the
string "(Moderated)" within it. The whole groupinfo-body is intended
to be interpreted as a text written in the UTF-8 character set.
The "application/news-groupinfo" is used in conjunction with the
"newgroup" (7.2.1) and "mvgroup" (7.2.3) control messages. The
newsgroup-name in the newsgroups-line MUST agree with the newsgroup-
name in the "newgroup" or "mvgroup" control message. The Content-
Type "application/news-groupinfo" MUST NOT be used except as a part
of such control messages. Although optional, the newsgroups-tag
SHOULD be included until such time as this standard has been widely
adopted, to ensure compatibility with present practice.
Moderated newsgroups MUST be marked by appending the case sensitive
text " (Moderated)" at the end. It is NOT recommended that the
moderator's email address be included in the newsgroup-description as
has sometimes been done.
Although, in accordance with [RFC 2822] and section 4.5 of this
standard, a newsgroups-line could have a maximum length of 998
octets, as a matter of policy a far lower limit, expressed in
characters, Ought to be set. The current convention is to limit its
length so that the newsgroup-name, the HTAB(s) (interpreted as 8-
character tabs that takes one at least to column 24) and the
newsgroup-description (excluding any moderation-flag) fit into 79
characters. However, this standard does not seek to enforce any such
rule, and reading agents SHOULD therefore enable a newsgroups-line of
any length to be displayed, e.g. by wrapping it as required.
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NOTE: The newsgroups-line is intended to provide a brief
description of the newsgroup, written in the UTF-8 character
set. Since newsgroup-names are required to be expressed in
UTF-8 when they appear in headers, and since [NNTP] requires the
use of UTF-8 when such a description is transmitted by the LIST
NEWSGROUPS command, it would also be convenient for serving
agents that keep a "newsgroups" file to store them in that form,
so as to avoid unnecessary conversions.
[If, at the time of publication of this standard, [NNTP] is still [RFC
977], that NOTE will need to be changed to indicate that "it is expected
that a future extension of [RFC 977] will require ...".]
7.2.1.3. Initial Articles
Some subparts of a "newgroup" or "mvgroup" control message MAY
contain an initial set of articles to be posted to the affected
newsgroup(s) as soon as it has been created or modified. These parts
are identified by having the Content-Type "application/news-
transmission", possibly with the parameter "usage=inject". The body
of each such part should be a complete proto-article, ready for
posting. This feature is intended for the posting of charters,
initial FAQs and the like to the newly formed group(s).
The Newsgroups-header of the proto-article MUST include the
newsgroup-name of the newly created or modified group. It MAY include
other newsgroup-names. If the proto-article includes a Message-ID-
header, the message identifier in it MUST be different from that of
any existing article and from that of the control message as a whole.
Alternatively such a message identifier MAY be derived by the
injecting agent when the proto-article is posted. The proto-article
SHOULD include the header "Distribution: local".
The proto-article SHOULD be injected at the serving agent that
processes the control message AFTER the newsgroup in question has
been created or modified. It MUST NOT be injected if the newsgroup
is not, in fact, created (for whatever reason). It MUST NOT be
submitted to any relaying agent for transmission beyond the serving
agent(s) upon which the newsgroup creation has just been effected (in
other words, it is to be treated as having a "Distribution: local"
header, whether such a header is actually present or not).
NOTE: It is not precluded that the proto-article is itself a
control message or other type of special article, to be
activated only upon creation of the new newsgroup. However,
except as might arise from that possibility, any
"application/news-transmission" within some nested "multipart/*"
structure within the proto-article is not to be activated.
7.2.1.4. Example
A "newgroup" with its charter:
From: "example.all Administrator" <admin@noc.example>
Newsgroups: example.admin.info,example.admin.announce
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Date: 27 Feb 2002 12:50:22 +0200
Subject: cmsg newgroup example.admin.info moderated
Approved: admin@noc.example
Control: newgroup example.admin.info moderated
Message-ID: <ng-example.admin.info-20020227@noc.example>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="nxtprt"
Content-Transfer-Encoding: 8bit
This is a MIME control message.
--nxtprt
Content-Type: application/news-groupinfo
For your newsgroups file:
example.admin.info About the example.* groups (Moderated)
--nxtprt
Content-Type: application/news-transmission
Newsgroups: example.admin.info
From: "example.all Administrator" <admin@noc.example>
Subject: Charter for example.admin.info
Message-ID: <charter-example.admin.info-20020227@noc.example>
Distribution: local
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
The group example.admin.info contains regularly posted
information on the example.* hierarchy.
--nxtprt--
7.2.2. The 'rmgroup' Control Message
control-message =/ Rmgroup-message
Rmgroup-message = "rmgroup" Rmgroup-arguments
Rmgroup-arguments = CFWS newsgroup-name
The "rmgroup" control message requests that the specified group be
removed from the list of valid groups. The Content-Type of the body
is unspecified; it MAY contain anything, usually an explanatory text.
NOTE: It is entirely proper for a serving agent to retain the
group until all the articles in it have expired, provided that
it ceases to accept new articles.
7.2.2.1. Example
Plain "rmgroup":
From: "example.all Administrator" <admin@noc.example>
Newsgroups: example.admin.obsolete, example.admin.announce
Date: 4 Apr 2002 22:04 -0900 (PST)
Subject: cmsg rmgroup example.admin.obsolete
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Message-ID: <rm-example.admin.obsolete-20020404@noc.example>
Approved: admin@noc.example
Control: rmgroup example.admin.obsolete
The group example.admin.obsolete is obsolete. Please remove it
from your system.
7.2.3. The 'mvgroup' Control Message
control-message =/ Mvgroup-message
Mvgroup-message = "mvgroup" Mvgroup-arguments
Mvgroup-arguments = CFWS newsgroup-name CFWS newsgroup-name
[ CFWS newgroup-flag ]
The "mvgroup" control message requests that the group specified by
the first (old-)newsgroup-name be moved to that specified by the
second (new-)newsgroup-name. Thus it is broadly equivalent to a
"newgroup" control message for the second group followed by a
"rmgroup" control message for the first group.
The second (new-)newsgroup-name MUST conform to all requirements
prescribed for the newsgroup-name of a "newgroup" control message
(7.2.1) and Ought, similarly, to conform to any established policies
of the hierarchy. The message body contains an "application/news-
groupinfo" part (7.2.1.2) containing machine- and human-readable
information about the new group, and possibly other subparts as for a
"newgroup" control message. The information conveyed in the
"application/news-groupinfo" body part, notably its newsgroups-line
(7.2.1.2), is applied to the new group.
When this message is received, the new group is created (if it does
not exist already) as for a "newgroup" control message, and MUST in
any case be made moderated if a newgroup-flag "moderated" is present,
and vice versa. At the same time, arrangements SHOULD be made to
remove the old group (as with a "rmgroup" control message), but only
after a suitable overlap period to allow the network to adjust to the
new arrangement.
At the same time as a serving agent acts upon this message, all
injecting agents associated with that serving agent SHOULD inhibit
the posting of new articles to the old group (preferably with some
indication to the poster that the new group should have been used).
Relaying agents, however, MUST continue to propagate such articles
during the overlap period.
NOTE: It is to be expected that different serving agents will
act on this message at different points of time, users of the
old group will have to become accustomed to the new arrangement,
and followups to already established threads will likely
continue under the old group. Therefore, there needs to be an
overlap period during which articles may continue to be accepted
by relaying and serving agents in either group. This standard
does not specify any standard period of overlap (though it would
be expected to be expressed in days rather than in months). The
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inhibition of injection of new articles to the old group may
seem draconian, but it is the surest way to prevent the
changeover from dragging on indefinitely.
Since the "mvgroup" control message is newly introduced in this
standard and may not be widely implemented initially, it SHOULD be
followed shortly afterwards by a corresponding "newgroup" control
message; and again, after a reasonable overlap period, it MUST be
followed by a "rmgroup" control message for the old group.
In order to facilitate a smooth changeover, serving agents MAY
arrange to service requests for access to the old group by providing
access to the new group, which would then contain, or appear to
contain, all articles posted to either group (including, ideally, the
pre-changeover articles from the old one). Nevertheless, if this
feature is implemented, the articles themselves, as supplied to
reading agents, MUST NOT be altered in any way (and, in particular,
their Newsgroups-headers MUST contain exactly those newsgroups
present when they were injected). On the other hand, the Xref-header
MAY contain entries for either group (or even both).
NOTE: Some serving agents that use an "active" file permit an
entry of the form "oldgroup xxx yyy =newgroup", which enables
any articles arriving for oldgroup to be diverted to newgroup,
thus providing a simple implementation of this feature. However,
it is known that not all current serving agents will find
implementation so easy (especially in the short term) which is
why it is not mandated by this standard. Nevertheless, its
eventual implementation in all serving agents is to be
considered highly desirable.
On the other hand, it is recognized that this feature would
likely not be implementable if the new group was already in
existence with existing articles in it. This situation should
not normally arise except when there is already some confusion
as to which groups are, or are not, supposed to exist in that
hierarchy. Note that the "mvgroup" control message is not really
intended to be used for merging two existing groups.
7.2.3.1. Example
From: "example.all Administrator" <admin@noc.example>
Newsgroups: example.oldgroup,example.newgroup,example.admin.announce
Date: 30 Apr 2002 22:04 -0500 (EST)
Subject: cmsg mvgroup example.oldgroup example.newgroup moderated
Message-ID: <mvgroup-example.oldgroup-20020430@noc.example>
Approved: admin@noc.example
Control: mvgroup example.oldgroup example.newgroup moderated
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MIME-Version: 1.0
Content-Type: multipart/mixed; boundary=nxt
--nxt
Content-Type: application/news-groupinfo
For your newsgroups file:
example.newgroup The new replacement group (Moderated)
--nxt
The moderated group example.oldgroup is replaced by
example.newgroup. Please update your configuration, and please,
if possible, arrange to file articles arriving for
example.oldgroup as if they were in example.newgroup.
--nxt--
7.2.4. The 'checkgroups' Control Message
The "checkgroups" control message contains a list of all the valid
groups in a complete hierarchy.
control-message =/ Checkgroup-message
Checkgroup-message = "checkgroups" Checkgroup-arguments
Checkgroup-arguments= [ chkscope ] [ chksernr ]
chkscope = 1*( CFWS ["!"] newsgroup-name )
chksernr = CFWS "#" 1*DIGIT
A "checkgroups" message applies to any (sub-)hierarchy with a prefix
listed in the chkscope parameter, provided that the rightmost
matching newsgroup-name in the list is not immediately preceded by a
"!". If no chkscope parameter is given, it applies to all
hierarchies for which group statements appear in the message.
NOTE: Some existing software does not support the "chkscope"
parameter. Thus a "checkgroups" message SHOULD also contain the
groups of other subhierarchies the sender is not responsible
for. "New" software MUST ignore groups which do not fall within
the chkscope parameter of the "checkgroups" message.
The chksernr parameter is a serial number, which can be any positive
integer (e.g. just numbered or the date in YYYYMMDD). It SHOULD
increase by an arbitrary value with every change to the group list
and MUST NOT ever decrease.
NOTE: This was added to circumvent security problems in
situations where the Date-header cannot be authenticated.
Example:
Control: checkgroups de !de.alt #248
which includes the whole of the 'de.*' hierarchy, with the exception
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of its 'de.alt.*' sub-hierarchy.
The body of the message has the Content-Type "application/news-
checkgroups". It asserts that the newsgroups it lists are the only
newsgroups in the specified hierarchies.
NOTE: The checkgroups message is intended to synchronize the
list of newsgroups stored by a serving agent, and their
newsgroup-descriptions, with the lists stored by other serving
agents throughout the network. However, it might be inadvisable
for the serving agent actually to create or delete any
newsgroups without first obtaining the approval of its
administrators for such proposed actions.
7.2.4.1. Application/news-checkgroups
The "application/news-checkgroups" body part contains a complete list
of all the newsgroups in a hierarchy, their newsgroup-descriptions
and their moderation status.
The MIME content type definition of "application/news-checkgroups"
is:
MIME type name: application
MIME subtype name: news-checkgroups
Required parameters: none
Disposition: by default, inline
Encoding considerations: "7bit" or "8bit" is sufficient and MUST be
used to maintain compatibility.
Security considerations: this type MUST NOT be used except as part
of a checkgroups control message
The content of the "application/news-checkgroups" body part is
defined as:
checkgroups-body = *( valid-group CRLF )
valid-group = newsgroups-line ; see 7.2.1.2
The whole checkgroups-body is intended to be interpreted as a text
written in the UTF-8 character set.
The "application/news-checkgroups" content type is used in
conjunction with the "checkgroups" control message (7.2.4).
NOTE: The possibility of removing a complete hierarchy by means
of an "invalidation" line beginning with a '!' is no longer
provided by this standard. The intent of the feature was widely
misunderstood and it was misused more often than it was used
correctly. The same effect, if required, can now be obtained by
the use of an appropriate chkscope argument in conjunction with
an empty checkgroups-body.
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7.3. Cancel
The cancel message requests that a target article be "canceled" i.e.
be withdrawn from circulation or access. A cancel message may be
issued in the following circumstances.
1. The poster of an article (or, more specifically, any entity
mentioned in the From-header or the Sender-header, whether or not
that entity was the actual poster) is always entitled to issue a
cancel message for that article, and serving agents SHOULD honour
such requests. Posting agents SHOULD facilitate the issuing of
cancel messages by posters fulfilling these criteria.
2. The agent which injected the article onto the network (more
specifically, the entity identified by the path-identity in front
of the leftmost '%' delimiter in the Path-header (5.6) or in the
Injector-Info-header (6.19) and, where appropriate, the moderator
(more specifically, any entity mentioned in the Approved-header)
is always entitled to issue a cancel message for that article, and
serving agents SHOULD honour such requests.
3. Other entities MAY be entitled to issue a cancel message for that
article, in circumstances where established policy for any
hierarchy or group in the Newsgroup-header, or established custom
within Usenet, so allows (such policies and customs are not
defined by this standard). Such cancel messages MUST include an
Approved-header identifying the responsible entity. Serving agents
MAY honour such requests, but SHOULD first take steps to verify
their appropriateness.
control-message =/ Cancel-message
Cancel-message = "cancel" Cancel-arguments
Cancel-arguments = CFWS msg-id [CFWS]
The argument identifies the article to be cancelled by its message
identifier. The body SHOULD contain an indication of why the
cancellation was requested. The cancel message SHOULD be posted to
the same newsgroup, with the same distribution, as the article it is
attempting to cancel.
A serving agent that elects to honour a cancel message SHOULD make
the article unavailable for relaying or serving (perhaps by deleting
it completely). If the target article is unavailable, and the
acceptability of the cancel message cannot be established without it,
activation of the cancel message SHOULD be delayed until the target
article has been seen. See also sections 8.3 and 8.4.
NOTE: It is expected that the security extension envisaged in
section 7.1 will make more detailed provisions for establishing
whether honouring a particular cancel message is in order. In
particular, it is likely that there will be provision for the
digital signature of 3rd party cancels.
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NOTE: A cancel submitted by the poster for an article in a
moderated group will be forwarded to the moderator of that
group, and it is up to that moderator to act upon it (8.7).
NOTE: The former requirement [RFC 1036] that the From and/or
Sender-headers of the cancel message should match those of the
original article has been removed from this standard, since it
only encouraged cancel issuers to conceal their true identity,
and it was not usually checked or enforced by canceling
software. Therefore, both the From and/or Sender-headers and
any Approved-header should now relate to the entity responsible
for issuing the cancel message.
7.4. Ihave, sendme
The "ihave" and "sendme" control messages implement a crude batched
predecessor of the NNTP [NNTP] protocol. They are largely obsolete on
the Internet, but still see use in conjunction with some transport
protocols such as UUCP, especially for backup feeds that normally are
active only when a primary feed path has failed. There is no
requirement for relaying agents that do not support such transport
protocols to implement them.
NOTE: The ihave and sendme messages defined here have ABSOLUTELY
NOTHING TO DO WITH NNTP, despite similarities of terminology.
The two messages share the same syntax:
control-message =/ Ihave-message
Ihave-message = "ihave" Ihave-arguments
Ihave-arguments = relayer-name
control-message =/ Sendme-message
Sendme-message = "sendme" Sendme-arguments
Sendme-arguments = Ihave-arguments
relayer-name = path-identity ; see 5.6.1
ihave-body = *( msg-id CRLF )
sendme-body = ihave-body
The body of the message consists of a list of msg-ids, one per line.
[RFC 1036] also permitted the list of msg-ids to appear in the Ihave-
or Sendme-arguments with the syntax
Ihave-arguments = [FWS] *( msg-id FWS ) [relayer-name]
but this form SHOULD NOT now be used, though relaying agents MAY
recognize and process it for backward compatibility.
The ihave message states that the named relaying agent has received
articles with the specified message identifiers, which may be of
interest to the relaying agents receiving the ihave message. The
sendme message requests that the agent receiving it send the articles
having the specified message identifiers to the named relaying agent.
These control messages are normally sent essentially as point-to-
point messages, by using newsgroup-names in the Newsgroups-header of
the form "to." followed by one (or possibly more) components in the
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form of a relayer-name (see section 5.5.1 which forbids "to" as the
first component of a newsgroup-name). The control message SHOULD then
be delivered ONLY to the relaying agent(s) identified by that
relayer-name, and any relaying agent receiving such a message which
includes its own relayer-name MUST NOT propagate it further. Each
pair of relaying agent(s) sending and receiving these messages MUST
be immediate neighbors, exchanging news directly with each other.
Each relaying agent advertises its new arrivals to the other using
ihave messages, and each uses sendme messages to request the articles
it lacks.
To reduce overhead, ihave and sendme messages SHOULD be sent
relatively infrequently and SHOULD contain reasonable numbers of
message IDs. If ihave and sendme are being used to implement a backup
feed, it may be desirable to insert a delay between reception of an
ihave and generation of a sendme, so that a slightly slow primary
feed will not cause large numbers of articles to be requested
unnecessarily via sendme.
7.5. Obsolete control messages.
The following control messages are declared obsolete by this
standard:
sendsys
version
whogets
senduuname
8. Duties of Various Agents
The following section sets out the duties of various agents involved
in the creation, relaying and serving of Usenet articles. Insofar as
these duties are described as sequences of steps to be followed, it
should be understood that it is the effect of these sequences that is
important, and implementations may use any method that gives rise to
that same effect.
In this section, the word "trusted", as applied to the source of some
article, means that an agent processing that article has verified, by
some means, the identity of that source (which may be another agent
or a poster).
NOTE: In many implementations, a single agent may perform
various combinations of the injecting, relaying and serving
functions. Its duties are then the union of the various duties
concerned.
8.1. General principles to be followed
There are two important principles that news implementors (and
administrators) need to keep in mind. The first is the well-known
Internet Robustness Principle:
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Be liberal in what you accept, and conservative in what you
send.
However, in the case of news there is an even more important
principle, derived from a much older code of practice, the
Hippocratic Oath (we may thus call this the Hippocratic Principle):
First, do no harm.
It is VITAL to realize that decisions which might be merely
suboptimal in a smaller context can become devastating mistakes when
amplified by the actions of thousands of hosts within a few minutes.
In the case of gateways, the primary corollary to this is:
Cause no loops.
8.2. Duties of an Injecting Agent
An Injecting Agent is responsible for taking a proto-article from a
posting agent and either forwarding it to a moderator or injecting it
into the relaying system for access by readers.
As such, an injecting agent is considered responsible for ensuring
that any article it injects conforms with the rules of this standard
and the policies of any newsgroups or hierarchies that the article is
posted to. It is also expected to bear some responsibility towards
the rest of the network for the behaviour of its posters (and
provision is therefore made for it to be easily contactable by
email).
To this end injecting agents MAY cancel articles which they have
previously injected (see 7.3).
8.2.1. Proto-articles
A proto-article is one that has been created by a posting agent and
has not yet been injected into the news system by an injecting agent.
It SHOULD NOT be propagated in that form to other than injecting
agents. A proto-article has the same format as a normal article
except that some of the following mandatory headers MAY be omitted:
Message-Id-header, Date-header, Path-header (and even From-header if
the particular injecting agent can derive that information from other
sources). These headers MUST NOT contain invalid values; they MUST
either be correct or not present at all.
A proto-article SHOULD NOT contain the '%' path-delimiter in any
Path-header, except in the rare cases where an article gets injected
twice. It MAY contain path-identities with other path-delimiters in
the pre-injection portion of the Path-header (5.6.3).
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8.2.2. Procedure to be followed by Injecting Agents
A injecting agent receives proto-articles from posting and followup
agents. It verifies them, adds headers where required and then either
forwards them to a moderator or injects them by passing them to
serving or relaying agents.
If an injecting agent receives an otherwise valid article that has
already been injected it SHOULD either act as if it is a relaying
agent or else pass the article on to a relaying agent completely
unaltered. Exceptionally, it MAY reinject the article, perhaps as a
part of some complex gatewaying process (in which case it will add a
second '%' path-delimiter to the Path-header). It MUST NOT forward
an already injected article to a moderator.
An injecting agent processes articles as follows:
1. It MUST remove any Injector-Info- or Complaints-To-header already
present (though it might be useful to copy them to suitable X-
headers). It SHOULD likewise remove any NNTP-Posting-Host or other
undocumented tracing header.
2. It SHOULD verify that the article is from a trusted source.
However, it MAY allow articles in which headers contain "forged"
email addresses, that is, addresses which are not valid for the
known and trusted source, especially if they end in ".invalid".
3. It MUST reject any article whose Date-header is more than 24 hours
into the past or into the future (cf. 5.1).
4. It MUST reject any article that does not have the correct
mandatory headers for a proto-article (5 and 8.2.1) present, or
which contains any header that does not have syntactically legal
contents. In particular, it MUST either reject any article whose
Newsgroups-header or Followup-To-header contains an encoded
newsgroup-name (5.5.2) or, alternatively, decode those newsgroup-
names and continue (this being a useful service for moderators
using that injecting agent, see 8.7). It SHOULD reject any
article which contains any header deprecated for Netnews (4.2.1).
5. If the article is rejected (for reasons given above, or for other
formatting errors or matters of site policy) the posting agent
SHOULD be informed (such as via an NNTP 44x response code) that
posting has failed and the article MUST NOT then be processed
further.
6. The Message-ID and Date-headers (and their contents) MUST be added
when not already present.
7. A Path-header with a tail-entry (5.6.3) MUST be correctly added if
not already present (except that it SHOULD NOT be added if the
article is to be forwarded to a moderator).
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8. The path-identity of the injecting agent with a '%' path-delimiter
(5.6.2) MUST be prepended to the Path-header; moreover, that
path-identity MUST be an FQDN mailable address (5.6.2).
9. An Injector-Info-header (6.19) SHOULD be added, identifying the
trusted source of the article, and a suitable Complaints-To-header
(6.20) MAY be added (except that these two headers MUST NOT be
added if the article is to be forwarded to a moderator).
10.The injecting agent MUST NOT alter the body of the article in any
way. It MAY add other headers not already provided by the poster,
but SHOULD NOT alter, delete, or reorder any existing header, with
the specific exception of "tracing" headers such as Injector-Info
and Complaints-To, which are to be removed as already mentioned.
NOTE: The addition of non-mandatory headers by the injecting
agent may alter the posting agent's preferred presentation of
information. In particular, adding a Sender-header that exposes
a sender's mailbox has privacy implications; where the main or
only purpose for doing so is as tracing information, it is
preferable to use instead one of the options provided for the
Injector-Info header (6.19.1).
11.If the Newsgroups-header contains no moderated groups, or if it
contains an Approved-header, the injecting agent forwards the
article to one or more relaying or serving agents.
12.Otherwise, when the Newsgroups-header contains one or more
moderated groups and the article does NOT contain an Approved-
header, the injecting agent MUST forward it to the moderator of
the first (leftmost) moderated group listed in the Newsgroups-
header via email. There are two possibilities for doing this:
(a) The complete article is encapsulated (headers and all) within
the email, preferably using the Content-Type
"application/news-transmission" (6.21.6.1) with any usage
parameter set to "moderate". Moreover, there SHOULD NOT be
more than one encapsulated article within the one email.
This method has the advantage of removing any possible
conflict between Netnews and Email headers, or of changes to
those headers during transport through email (and in
particular, it ensures that any UTF8-xtra-chars within those
headers will pass safely through any email transport even if
it is 8bit-unsafe).
(b) The article is sent as an email as it stands, with the
addition of such extra headers (e.g. a To-header) as are
necessary for an email. Since the article is, in effect,
being gatewayed into Email, if the headers contain any UTF8-
xtra-chars the transformations described in section 8.8.1.1
MUST be applied.
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Although both of these methods have seen use in the past, the
preponderance of current usage on Usenet has been for method (b)
and many moderators are ill-prepared to deal with method (a).
Therefore, method (a) SHOULD NOT be used until such time as the
majority of moderators are able to accept it.
13.This standard does not prescribe how the email address of the
moderator is to be determined, that being a matter of policy to be
arranged by the agency responsible for the oversight of each
hierarchy. Nevertheless, there do exist various agents worldwide
which provide the service of forwarding to moderators, and the
address to use with them is obtained as follows:
(a) Each '.' in the newsgroup-name is replaced with a '-'.
(b) If the newsgroup-name contains any UTF8-xtra-char, it is
encoded as described in section 5.5.2.
(c) The result of these operations is used as the local-part of
the mailbox of the agent. For example, articles intended for
"news.announce.important" would be emailed to "news-
announce-important@forwardingagent.example".
8.3. Duties of a Relaying Agent
A Relaying Agent accepts injected articles from injecting and other
relaying agents and passes them on to relaying or serving agents
according to mutually agreed policy. Relaying agents SHOULD accept
articles ONLY from trusted agents.
A relaying agent processes articles as follows:
1. It MUST verify the leftmost entry in the Path-header and then
prepend its own path-identity with a '/' path-delimiter, and
possibly also the verified path-identity of its source with a '?'
path-delimiter (5.6.2).
2. It MUST reject any article whose Date-header is stale (see 5.1).
3. It MUST reject any article that does not have the correct
mandatory headers (section 5) present with legal contents.
4. It SHOULD reject any article whose optional headers (section 6) do
not have legal contents.
5. It SHOULD reject any article that has already been sent to it (a
database of message identifiers of recent messages is usually kept
and matched against).
6. It SHOULD reject any article that matches an already received
cancel message (or an equivalent Supersedes-header) issued by its
poster or by some other trusted entity.
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7. It MAY reject any article without an Approved-header posted to
newsgroups known to be moderated (this practice is strongly
recommended, but the information necessary to do it may not be
available to all agents).
8. It then passes articles which match mutually agreed criteria on to
neighbouring relaying and serving agents. However, it SHOULD NOT
forward articles to sites whose path-identity is already in the
Path-header.
NOTE: It is usual for relaying and serving agents to restrict
the Newsgroups, Distributions, age and size of articles that
they wish to receive.
If the article is rejected as being invalid, unwanted or unacceptable
due to site policy, the agent that passed the article to the relaying
agent SHOULD be informed (such as via an NNTP 43x response code) that
relaying failed. In order to prevent a large number of error messages
being sent to one location, relaying agents MUST NOT inform any other
external entity that an article was not relayed UNLESS that external
entity has explicitly requested that it be informed of such errors.
NOTE: In order to prevent overloading, relaying agents should
not routinely query an external entity (such as a DNS-server) in
order to verify an article (though a local cache of the required
information might usefully be consulted).
Relaying agents MUST NOT alter, delete or rearrange any part of an
article expect for headers designated as variant (4.2.5.3).
8.4. Duties of a Serving Agent
A Serving Agent takes an article from a relaying or injecting agent
and files it in a "news database". It also provides an interface for
reading agents to access the news database. This database is normally
indexed by newsgroup with articles in each newsgroup identified by an
article-locater (usually in the form of a decimal number - see 6.16).
NOTE: Since control messages are often of interest, but should
not be displayed as normal articles in regular newsgroups, it is
common for serving agents to make them available in a pseudo-
newsgroup named "control" or in a pseudo-newsgroup in a sub-
hierarchy under "control." (e.g. "control.cancel").
A serving agent processes articles as follows:
1. It MUST verify the leftmost entry in the Path-header and then
prepend its own path-identity with a '/' path-delimiter, and
possibly also the verified path-identity of its source with a '?'
path-delimiter (5.6.2).
2. It MUST reject any article whose Date-header is stale (see 5.1).
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3. It MUST reject any article that does not have the correct
mandatory headers (section 5) present, or which contains any
header that does not have legal contents.
4. It SHOULD reject any article that has already been sent to it (a
database of message identifiers of recent messages is usually kept
and matched against).
5. It SHOULD reject any article that matches an already received
cancel message (or an equivalent Supersedes-header) issued by its
poster or by some other trusted entity.
6. It MUST reject any article without an Approved-header posted to
any moderated newsgroup which it is configured to receive, and it
MAY reject such articles for any newsgroup it knows be moderated.
7. It MUST remove any Xref-header (6.16) from each article. It then
MAY (and usually will) generate a fresh Xref-header.
8. Finally, it stores the article in its news database.
8.5. Duties of a Posting Agent
A Posting Agent is used to assist the poster in creating a valid
proto-article and forwarding it to an injecting agent.
Postings agents SHOULD ensure that proto-articles they create are
valid news articles according to this standard and other applicable
policies.
Posting agents meant for use by ordinary posters SHOULD reject any
attempt to post an article which cancels or Supersedes another
article of which the poster is not the author.
8.6. Duties of a Followup Agent
A Followup Agent is a special case of a posting agent and as such is
bound by all the posting agent's requirements plus additional ones.
Followup agents MUST create valid followups, in particular by
providing correctly adjusted forms of those headers described as
inheritable (4.2.5.2), notably the Newsgroups-header (5.5), the
Subject-header (5.4) and the References-header (6.10), and they Ought
to observe appropriate quoting conventions in the body (see 4.3.2).
Followup agents SHOULD initialize the Newsgroups-header from the
precursor's Followup-To-header, if present, when preparing a
followup; however posters MAY then change this before posting if they
wish.
Followup agents MUST NOT attempt to send email to any address ending
in ".invalid". Followup agents SHOULD NOT email copies of the
followup to the poster of the precursor unless this has been
explicitly requested by means of a Mail-Copies-To-header (6.8), but
they SHOULD include a Posted-And-Mailed-header (6.9) whenever a copy
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is so emailed.
8.7. Duties of a Moderator
A Moderator receives news articles by email, decides whether to
accept them and, if so, either injects them into the news stream or
forwards them to further moderators.
Articles will be received by the moderator either encapsulated as an
object of Content-Type application/news-transmission (or possibly
encapsulated but without an explicit Content-Type-header), or else
directly as an email already containing all the headers appropriate
for a Netnews article (see 8.2.2). Moderators SHOULD be prepared to
accept articles in either format.
A moderator processes an article, as submitted to any newsgroup that
he moderates, as follows:
1. He decides, on the basis of whatever moderation policy applies to
his group, whether to accept or reject the article. He MAY do this
manually, or else partially or wholly with the aid of appropriate
software for whose operation he is then responsible. If the
article is a cancel nessage (7.3) issued by the poster of an
earlier article, then he Ought to cancel it (in which case there
is no more to be done). He MAY modify the article if that is in
accordance with the applicable moderation policy (and in
particular he MAY remove redundant headers and add Comments and
other informational headers). He also needs to be aware if any
change he makes to the article will invalidate some authentication
check provided by the poster or by an earlier moderator.
He MAY inform the poster if the article is accepted, and he Ought
to inform the poster if it is rejected. If it is rejected, then
it normally fails for all the newsgroups for which it was
intended. If it is accepted, the moderator proceeds with the
following steps.
2. If the Newsgroups-header contains further moderated newsgroups for
which approval has not already been given, he adds an indication
(identifying both himself and the name of the group) that he
approves the article, and then forwards it to the moderator of the
leftmost unapproved group (which, if this standard has been
followed correctly, will generally be the next moderated group to
the right of his own). There are two ways to do this:
(a) He emails it to the submission address of the next moderator
(see section 8.2.2 for the proper method of doing this), or
(b) he rotates the newsgroup-names in the Newsgroups-header to
the left so that the targeted group is the leftmost moderated
group in that header, and injects it as below (thus causing
the injecting agent to email it to the correct moderator).
However, he MUST first ensure that the article contains no
Approved-header.
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NOTE: This standard does not prescribe how a moderator's
approval is to be indicated (though a future standard may do
so). Possible methods include adding an Approved header (or a
similar but differently named header if method (b) is being
used) listing all the approvals made so far, or adding a
separate header for each individual approval (the header X-Auth
is sometimes used for this purpose). The approval may also be
confirmed with some form of digital signature (7.1).
3. If the Newsgroups-header contains no further unapproved moderated
groups, he adds an Approved-header (6.14) identifying himself and,
insofar as is possible, all the other moderators who have approved
the article. He thus assumes responsibility for having ensured
that the article was acceptable to the moderators of all the
moderated groups involved.
4. A moderator Ought Not (absent any established and widely
promulgated policy to the contrary) to remove any newsgroup-name
from the Newsgroups-header, nor split an article into two versions
with disjoint Newsgroups-headers. These are matters more usually
within the prerogative of the poster; moreover splitting can lead
to fragmentation of threads.
5. The Date-header SHOULD be retained, except that if it is stale
(5.1) for reasons understood by the moderator (e.g. delays in the
moderation process) he MAY substitute the current date (but must
then take responsibility for any loops that ensue). The Message-
ID-header SHOULD also be retained unless it is obviously non-
compliant with this standard.
NOTE: A message identifier created by a conforming posting or
injecting agent, or even by a mail user agent conforming to [RFC
2822], may reasonably be supposed to be conformant (and will, in
any case, be caught by the injecting agent if it is not).
6. Any variant headers (4.2.5.3) MUST be removed, except that a
Path-header MAY be truncated to only its pre-injection region
(5.6.3). Any Injector-Info-header (6.19) or Complaints-To-header
(6.20) MUST be removed.
7. He then causes the article to be injected, having first decoded
any encoded newsgroup-name (5.5.2), unless his injecting agent
offers that service (8.2.2), and having observed all the duties of
a posting agent.
NOTE: This standard does not prescribe how the moderator or
moderation policy for each newsgroup is established; rather it
assumes that whatever agencies are responsible for the relevant
network or hierarchy (1.1) will have made appropriate
arrangements in that regard.
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8.8. Duties of a Gateway
A Gateway transforms an article into the native message format of
another medium, or translates the messages of another medium into
news articles. Encapsulation of a news article into a message of MIME
type application/news-transmission, or the subsequent undoing of that
encapsulation, is not gatewaying, since it involves no transformation
of the article.
There are two basic types of gateway, the Outgoing Gateway that
transforms a news article into a different type of message, and the
Incoming Gateway that transforms a message from another medium into a
news article and injects it into a news system. These are handled
separately below.
The primary dictat for a gateway is:
Above all, prevent loops.
Transformation of an article into another medium stands a very high
chance of discarding or interfering with the protection inherent in
the news system against duplicate articles. The most common problem
caused by gateways is "spews," gateway loops that cause previously
posted articles to be reinjected repeatedly into Usenet. To prevent
this, a gateway MUST take precautions against loops, as detailed
below.
If bidirectional gatewaying (both an incoming and an outgoing
gateway) is being set up between Netnews and some other medium, the
incoming and outgoing gateways SHOULD be coordinated to avoid
reinjection of gated articles. Circular gatewaying (gatewaying a
message into another medium and then back into Netnews) SHOULD NOT be
done; encapsulation of the article SHOULD be used instead where this
is necessary.
A second general principal of gatewaying is that the transformations
applied to the message SHOULD be as minimal as possible while still
accomplishing the gatewaying. Every change made by a gateway
potentially breaks a property of one of the media or loses
information, and therefore only those transformations made necessary
by the differences between the media should be applied.
It is worth noting that safe bidirectional gatewaying between a
mailing list and a newsgroup is far easier if the newsgroup is
moderated. Posts to the moderated group and submissions to the
mailing list can then go through a single point that does the
necessary gatewaying and then sends the message out to both the
newsgroup and the mailing list at the same time, eliminating most of
the possibility of loops. Bidirectional gatewaying between a mailing
list and an unmoderated newsgroup, in contrast, is difficult to do
correctly and is far more fragile.
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Newsgroups intended to be bidirectionally gated to a mailing list
SHOULD therefore be moderated where possible, even if the moderator
is a simple gateway and injecting agent that correctly handles
crossposting to other moderated groups and otherwise passes all
traffic.
8.8.1. Duties of an Outgoing Gateway
From the perspective of Netnews, an outgoing gateway is just a
special type of reading agent. The exact nature of what the outgoing
gateway will need to do to articles depends on the medium to which
the articles are being gated. The operation of the outgoing gateway
is only subject to additional constraints in the presence of one or
more corresponding incoming gateways back from that medium to
Netnews, since this opens the possibility of loops.
Where the format of the news article is incompatible with that of the
target medium, it may be necessary to apply transformations (see
8.8.1.1 for the particular case when the target is Email).
In general, the following practices are recommended for all outgoing
gateways, regardless of whether there is known to be a related
incoming gateway, both as a precautionary measure and as a guideline
to quality of implementation.
1. The message identifier of the news article should be preserved if
at all possible, preferably as or within the corresponding unique
identifier of the other medium, but if not at least as a comment
in the message. This helps greatly with preventing loops.
2. The Date of the news article should also be preserved if possible,
for similar reasons.
3. The message should be tagged in some way so as to prevent its
reinjection into Netnews. This may be impossible to do without
knowledge of potential incoming gateways, but it is better to try
to provide some indication even if not successful; at the least, a
human-readable indication that the article should not be gated
back to Netnews can help locate a human problem.
4. Netnews control messages should not be gated to another medium
unless they would somehow be meaningful in that medium.
8.8.1.1. Gatewaying into email
Although headers containing non-ASCII characters may well be conveyed
intact by many (if not most) current mail transport agents, that
ability is not a requirement of some transport protocols, notably of
SMTP [RFC 2821]. Likewise, although many mail user agents may
currently display (or be configurable to display) such headers
correctly, or at least adequately, messages containing such headers
are not compliant with the current Email standards, notably with [RFC
2822]. Note that non-ASCII body part headers [RFC 2046] (including
non-ASCII headers of a message/rfc822) are equally at variance with
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the current Email standards.
If, at some future time, the Email standards should be updated so as
to allow such headers, it would then become possible to transport
Netnews articles containing them over Email without further ado.
Until such a time, however, if a Netnews article is to be gatewayed
into Email with the intention that it be received and accepted by any
arbitrarily chosen destination, and if it contains any UTF8-xtra-char
in any of its headers or body part headers, then it MUST first be
transformed so as to conform to [RFC 2822] and/or [RFC 2046]. In
particular, articles emailed to moderators (8.2.2) MUST be so
transformed.
NOTE: It is not precluded that a gatewayer who knows, or is able
to control, the capabilities of the particular sites for which
an article is destined and of the transport paths leading to
those sites, may choose to send the article without
transformation, or at least without transformation of any
contained body part headers.
The surest way to transport an article containing non-ASCII headers
through Email is by encapsulation as an application/news-transmission
(6.21.6.1). However this method is not currently available for
sending to moderators for reason explained in section 8.2.2 step 12.
Until this method is considered safe to use, therefore,
transformation of those headers will be necessary. This can be
accomplished in the following steps:
1. If the header is unstructured, or is an experimental header
(4.2.5.1), any word(s) which is delimited by FWS or by the
start/end of the header-content is encoded according to [RFC
2047].
2. If the header is structured, any word(s) which is contained within
a comment and is delimited by FWS or by the "(" or ")" delimiting
that comment is encoded according to [RFC 2047], and likewise any
word(s) which is contained within a phrase and is delimited by FWS
or by the start/end of the header-content.
3. If the header contains a (MIME-style) parameter with a non-ASCII
value, the whole parameter is encoded according to [RFC 2231].
4. If the header is a Newsgroups-header or a Followup-To-header (or
any other header that contains a newsgroup-name), each newsgroup-
name is encoded according to section 5.5.2. Even if it is not
decoded at the far end, it is preferable to display that encoded
form than to display nothing at all. Note, however, that such
encoded newsgroup-names MUST be restored to their canonical form
before reinjection into any Netnews system.
5. Otherwise, if the header is not one defined by this standard or by
any standard known to the gateway (so that it cannot be determined
whether it is unstructured, or otherwise where comments and
phrases occur within it), then it is not possible to encode it
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according to a strict interpretation of [RFC 2047]. In that case,
the suggested treatment is to prepend an "X-" to the header-name,
thus transforming it into an experimental header, and to proceed
as in Step 1. This will ensure that a compliant Email message is
produced and that no information is discarded, but any intended
semantic effect of that header will be lost.
In all cases, there are additional restrictions imposed by [RFC 2047]
regarding the size, placement and contents of encoded-words which
MUST be observed. Moreover, these transformations MUST be applied
both within the header of the article and within any body part
headers (including the headers of any message/rfc822). It is
generally preferable for encodings to use the charset UTF-8, although
it might be wise first to confirm that that is indeed the charset
which had been used (see 4.4.1).
8.8.2. Duties of an Incoming Gateway
The incoming gateway has the serious responsibility of ensuring that
all of the requirements of this standard are met by the articles that
it forms. In addition to its special duties as a gateway, it bears
all of the duties and responsibilities of an injecting agent as well,
and additionally has the same responsibility of a relaying agent to
reject articles that it has already gatewayed.
An incoming gateway MUST NOT gate the same message twice. It may not
be possible to ensure this in the face of mangling or modification of
the message, but at the very least a gateway, when given a copy of a
message it has already gated identical except for trace headers (like
Received in Email or Path in Netnews) MUST NOT gate the message
again. An incoming gateway SHOULD take precautions against having
this rule bypassed by modifications of the message that can be
anticipated.
News articles prepared by gateways MUST be legal news articles. In
particular, they MUST include all of the mandatory headers, MUST
fully conform to the restrictions on said headers, and SHOULD exclude
any deprecated headers (4.2.1). This often requires that a gateway
function not only as a relaying agent, but also partly as a posting
agent, aiding in the synthesis of a conforming article from non-
conforming input.
Incoming gateways MUST NOT pass control messages (articles containing
a Control- or Supersedes-header) without removing or renaming that
header. Gateways MAY, however, generate their own cancel messages,
under the general allowance for injecting agents to cancel their own
messages (7.3). If a gateway receives a message that it can
determine is a valid equivalent of a cancel message in the medium it
is gatewaying, it SHOULD discard that message without gatewaying it,
generate a corresponding cancel message of its own, and inject that
cancel message.
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Incoming gateways MUST NOT inject control messages other than
cancels. Encapsulation SHOULD be used instead of gatewaying, when
direct posting is not possible or desirable.
NOTE: It is not unheard of for mail-to-news gateways to be used
to post control messages, but encapsulation should be used for
these cases instead. Gateways by their very nature are
particularly prone to loops. Spews of normal articles are bad
enough; spews of control messages with special significance to
the news system, possibly resulting in high processing load or
even email sent for every message received, are catastrophic. It
is far preferable to construct a system specifically for posting
control messages that can do appropriate consistency checks and
authentication of the originator of the message.
If there is a message identifier that fills a role similar to that of
the Message-ID-header in news, it SHOULD be used in the formation of
the message identifier of the news article, perhaps with
transformations required to meet the uniqueness requirement of
Netnews and with the removal of any comments so as to comply with the
syntax in section 5.3. Such transformations SHOULD be designed so
that two messages with the same identifier generate the same
Message-ID-header.
NOTE: Message identifiers play a central role in the prevention
of duplicates, and their correct use by gateways will do much to
prevent loops. Netnews does, however, require that message
identifiers be unique, and therefore message identifiers from
other media may not be suitable for use without modification. A
balance must be struck by the gateway between preserving
information used to prevent loops and generating unique message
identifiers.
Exceptionally, if there are multiple incoming gateways for a
particular set of messages, each to a different newsgroup(s), each
one SHOULD generate a message identifier unique to that gateway. Each
incoming gateway nonetheless MUST ensure that it does not gate the
same message twice.
NOTE: Consider the example of two gateways of a given mailing
list into the world-wide Usenet newsgroups, both of which
preserve the email message identifier. Each newsgroup may then
receive a portion of the messages (different sites seeing
different portions). In these cases, where there is no one
"official" gateway, some other method of generating message
identifiers has to be used to avoid collisions. It would
obviously be preferable for there to be only one gateway which
crossposts, but this may not be possible to coordinate.
If no date information is available, the gateway MAY supply a Date-
header with the gateway's current date. If only partial information
is available (e.g. date but not time), this SHOULD be fleshed out to
a full Date-header by adding default values rather than discarding
this information. Only in very exceptional circumstances should Date
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information be discarded, as it plays an important role in preventing
reinjection of old messages.
An incoming gateway MUST add a Sender-header to the news article it
forms containing the mailbox of the administrator of the gateway.
Problems with the gateway may be reported to this mailbox. The
display-name portion of this mailbox SHOULD indicate that the entity
responsible for injection of the message is a gateway. If the
original message already had a Sender-header, it SHOULD be renamed so
that its contents can be preserved.
8.8.3. Example
To illustrate the type of precautions that should be taken against
loops, here is an example of the measures taken by one particular
combination of mail-to-news and news-to-mail gateways at Stanford
University designed to handle bidirectional gatewaying between
mailing lists and unmoderated groups.
1. The news-to-mail gateway preserves the message identifier of the
news article in the generated email message. The mail-to-news
gateway likewise preserves the email message identifier provided
that it is syntactically valid for Netnews. This allows the news
system's built-in suppression of duplicates to serve as the first
line of defense against loops.
2. The news-to-mail gateway adds an X-Gateway-header to all messages
it generates. The mail-to-news gateway discards any incoming
messages containing this header. This is robust against mailing
list managers that replace the message identifier, and against any
number of email hops, provided that the other message headers are
preserved.
3. The mail-to-news gateway inserts the host name from which it
received the email message in the pre-injection region of the Path
(5.6.3). The news-to-mail gateway refuses to gateway any message
that contains the list server name in the pre-injection region of
its Path-header. This is robust against any amount of munging of
the message headers by the mailing list, provided that the email
only goes through one hop.
4. The mail-to-news gateway is designed never to generate bounces to
the envelope sender. Instead, articles that are rejected by the
news server (for reasons not warranting silent discarding of the
message) result in a bounce message sent to an errors address
known not to forward to any mailing lists, so that they can be
handled by the news administrators.
These precautions have proven effective in practice at preventing
loops for this particular application (bidirectional gatewaying
between mailing lists and locally distributed newsgroups where both
gateways can be designed together). General gatewaying to world-wide
newsgroups poses additional difficulties; one must be very wary of
strange configurations, such as a newsgroup gated to a mailing list
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which is in turn gated to a different newsgroup.
9. Security and Related Considerations
There is no security. Don't fool yourself. Usenet is a prime example
of an Internet Adhocratic-Anarchy; that is, an environment in which
trust forms the basis of all agreements. It works.
9.1. Leakage
Articles which are intended to have restricted distribution are
dependent on the goodwill of every site receiving them. The
"Archive: no" header (6.12) is available as a signal to automated
archivers not to file an article, but that cannot be guaranteed.
The Distribution-header makes provision for articles which should not
be propagated beyond a cooperating subnet. The key security word here
is "cooperating". When a machine is not configured properly, it may
become uncooperative and tend to distribute all articles.
The flooding algorithm is extremely good at finding any path by which
articles can leave a subnet with supposedly restrictive boundaries,
and substantial administrative effort is required to avoid this.
Organizations wishing to control such leakage are strongly advised to
designate a small number of official gateways to handle all news
exchange with the outside world (however, making such gateways too
restrictive can also encourage the setting up of unofficial paths
which can be exceedingly hard to track down).
The sendme control message (7.4), insofar as it is still used, can be
used to request articles with a given message identifier, even one
that is not supposed to be supplied to the requestor.
9.2. Attacks
9.2.1. Denial of Service
The proper functioning of individual newsgroups can be disrupted by
the massive posting of "noise" articles, by the repeated posting of
identical or near identical articles, by posting followups unrelated
to their precursors, or which quote their precursors in full with the
addition of minimal extra material (especially if this process is
iterated), and by crossposting to, or setting followups to, totally
unrelated newsgroups.
Many have argued that "spam", massively multiposted (and to a lesser
extent massively crossposted) articles, usually for advertising
purposes, also constitutes a DoS attack in its own regard. This may
be so.
Such articles intended to deny service, or other articles of an
inflammatory nature, may also have their From or Reply-To addresses
set to valid but incorrect email addresses, thus causing large
volumes of email to descend on the true owners of those addresses.
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Similar effects could be caused by any email header which could cause
every reading agent receiving it to take some externally visible
action. For example, the Disposition-Notification-To-header defined
in [RFC 2298] could cause huge numbers of acknowledgements to be
emailed to an unsuspecting third party (for which reason [RFC 2298]
declares that that header SHOULD NOT be used in Netnews).
It is a violation of this standard for a poster to use as his address
a mailbox which he is not entitled to use. Even addresses with an
invalid local-part but a valid domain can cause disruption to the
administrators of such domains. Posters who wish to remain anonymous
or to prevent automated harvesting of their addresses, but who do not
care to take the additional precautions of using more sophisticated
anonymity measures, should avoid that violation by the use of
addresses ending in the ".invalid" top-level-domain (see 5.2).
A malicious poster may also prevent his article being seen at a
particular site by preloading that site into the Path-header (5.6.1)
and may thus prevent the true owner of a forged From or Reply-To
address from ever seeing it.
A malicious complainer may submit a modified copy of an article (e.g.
with an altered Injector-Info-header) to the administrator of an
injecting agent in an attempt to discredit the author of that article
and even to have his posting privileges removed. Administrators
should therefore obtain a genuine copy of the article from their own
serving agent before taking such precipitate action.
Administrative agencies with responsibility for establishing policies
in particular hierarchies can and should set bounds upon the
behaviour that is considered acceptable within those hierarchies (for
example by promulgating charters for individual newsgroups, and other
codes of conduct).
Whilst this standard places an onus upon injecting agents to bear
responsibility for the misdemeanours of their posters (which includes
non-adherence to established policies of the relevant hierarchies as
provided in section 8.2), and to provide assistance to the rest of
the network by making proper use of the Injector-Info- (6.19) and
Complaints-To- (6.20) headers, it makes no provision for enforcement,
which may in consequence be patchy. Nevertheless, injecting sites
which persistently fail to honour their responsibilities or to comply
with generally accepted standards of behaviour are likely to find
themselves blacklisted, with their articles refused propagation and
even subject to cancellation, and other relaying sites would be well
advised to withdraw peering arrangements from them.
9.2.2. Compromise of System Integrity
The posting of unauthorized (as determined by the policies of the
relevant hierarchy) control messages can cause unwanted newsgroups to
be created, or wanted ones removed, from serving agents.
Administrators of such agents SHOULD therefore take steps to verify
the authenticity of such control messages, either by manual
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inspection (particularly of the Approved-header) or by checking any
digital signatures that may be provided (see 7.1). In addition, they
SHOULD periodically compare the newsgroups carried against any
regularly issued checkgroups messages, or against lists maintained by
trusted servers and accessed by out-of-band protocols such as FTP or
HTTP.
Malicious cancel messages (7.3) can cause valid articles to be
removed from serving agents. Administrators of such agents SHOULD
therefore take steps to verify that they originated from the
(apparent) poster, the injector or the moderator of the article, or
that in other cases they came from a place that is trusted to work
within established policies and customs. Such steps SHOULD include
the checking of any digital signatures, or other security devices,
that may be provided (see 7.1). Articles containing Supersedes-
headers (6.15) are effectively cancel messages, and SHOULD be subject
to the same checks. Currently, many sites choose to ignore all
cancel messages on account of the difficulty of conducting such
checks.
Improperly configured serving agents can allow articles posted to
moderated groups onto the net without first being approved by the
moderator. Injecting agents SHOULD verify that moderated articles
were received from one of the entities given in their Approved-
headers and/or check any digital signatures that may be provided (see
7.1).
The filename parameter of the Archive-header (6.12) can be used to
attempt to store archived articles in inappropriate locations.
Archiving sites should be suspicious of absolute filename parameters,
as opposed to those relative to some location of the archiver's
choosing.
There may be weaknesses in particular implementations that are
subject to malicious exploitation. In particular, it has not been
unknown for complete shell scripts to be included within Control-
headers. Implementors need to be aware of this.
Reading agents should be chary of acting automatically upon MIME
objects with an "application" Content-Type that could change the
state of that agent, except in contexts where such applications are
specifically expected (see 6.21). Even the Content-Type "text/html"
could have unexpected side effects on account of embedded objects,
especially embedded executable code or URLs that invoke non-news
protocols such as HTTP [RFC 2616]. It is therefore generally
recommended that reading agents do not enable the execution of such
code (since it is extremely unlikely to have a valid application
within Netnews) and that they only honour URLs referring to other
parts of the same article.
Non-printable characters embedded in article bodies may have
surprising effects on printers or terminals, notably by reconfiguring
them in undesirable ways which may become apparent only after the
reading agent has terminated.
C. H. Lindsey [Page 98]
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9.3. Liability
There is a presumption that a poster who sends an article to Usenet
intends it to be stored on a multitude of serving agents, and has
therefore given permission for it to be copied to that extent.
Nevertheless, Usenet is not exempt from the Copyright laws, and it
should not be assumed that permission has been given for the article
to be copied outside of Usenet, nor for its permanent archiving
contrary to any Archive-header that may be present.
Posters also need to be aware that they are responsible if they
breach Copyright, Libel, Harassment or other restrictions relating to
material that they post, and that they may possibly find themselves
liable for such breaches in jurisdictions far from their own. Serving
agents may also be liable in some jurisdictions, especially if the
breach has been explicitly drawn to their attention.
Users who are concerned about such matters should seek advice from
competent legal authorities.
10. IANA Considerations
IANA is requested to register the following media types, described
elsewhere in this standard for use with the Content-Type-header, in
the IETF tree in accordance with the procedures set out in [RFC
2048].
application/news-transmission (6.21.6.1)
application/news-groupinfo (7.2.1.2)
application/news-checkgroups (7.2.4.1)
IANA is also requested to change the status of the following media
type to "OBSOLETE".
message/news (6.21.6.2)
NOTE: "Application/news-transmission" is an update, with
clarification and additional optional parameters, to an existing
registration. "Message/rfc822" should now be used in place of
the obsoleted "message/news".
11. References
[ANSI X3.4] "American National Standard for Information Systems -
Coded Character Sets - 7-Bit American National Standard Code for
Information Interchange (7-Bit ASCII)", ANSI X3.4, 1986.
[ISO 3166] "Codes for the representation of names of countries and
their subdivisions -- Part 1: Country codes", ISO 3166, 1997.
[ISO 8859] International Standard - Information Processing - 8-bit
Single-Byte Coded Graphic Character Sets. Part 1: Latin
alphabet No. 1, ISO 8859-1, 1987. Part 2: Latin alphabet No. 2,
C. H. Lindsey [Page 99]
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ISO 8859-2, 1987. Part 3: Latin alphabet No. 3, ISO 8859-3,
1988. Part 4: Latin alphabet No. 4, ISO 8859-4, 1988. Part 5:
Latin/Cyrillic alphabet, ISO 8859-5, 1988. Part 6: Latin/Arabic
alphabet, ISO 8859-6, 1987. Part 7: Latin/Greek alphabet, ISO
8859-7, 1987. Part 8: Latin/Hebrew alphabet, ISO 8859-8, 1988.
[ISO/IEC 10646] "International Standard - Information technology -
Universal Multiple-Octet Coded Character Set (UCS) - Part 1:
Architecture and Basic Multilingual Plane", ISO/IEC 10646-
1:2000, 2000.
[NNTP] S. Barber, "Network News Transport Protocol", draft-ietf-
nntpext-base-*.txt.
[PGPVERIFY] David Lawrence,
<ftp://ftp.isc.org/pub/pgpcontrol/README.html>.
[RFC 1034] P. Mockapetris, "Domain Names - Concepts and Facilities",
RFC 1034, November 1987.
[RFC 1036] M. Horton and R. Adams, "Standard for Interchange of
USENET Messages", RFC 1036, December 1987.
[RFC 1153] F. Wancho, "Digest Message Format", RFC 1153, April 1990.
[RFC 1847] J. Galvin, S. Murphy, S. Crocker, and N. Freed, "Security
Multiparts for MIME: Multipart/Signed and Multipart/Encrypted",
RFC 1847, October 1995.
[RFC 1864] J. Myers and M. Rose, "The Content-MD5 Header Field", RFC
1864, October 1995.
[RFC 2045] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, November 1996.
[RFC 2046] N. Freed and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, November
1996.
[RFC 2047] K. Moore, "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text", RFC
2047, November 1996.
[RFC 2048] N. Freed, J. Klensin, and J. Postel, "Multipurpose
Internet Mail Extensions (MIME) Part Four: Registration
Procedures", RFC 2048, November 1996.
[RFC 2060] M. Crispin, "Internet Message Access Protocol - Version
4rev1", RFC 2060, December 1996.
[RFC 2060bis] M. Crispin, "Internet Message Access Protocol - Version
4rev1", draft-crispin-imapv-*.txt, October 2002.
C. H. Lindsey [Page 100]
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[RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC 2142] D. Crocker, "Mailbox Names for Common Services, Roles and
Functions", RFC 2142, May 1997.
[RFC 2156] S. Kille, "MIXER (Mime Internet X.400 Enhanced Relay):
Mapping between X.400 and RFC 822/MIME", RFC 2156, January 1998.
[RFC 2183] R. Troost, S. Dorner, and K.Moore, "Communicating
Presentation Information in Internet Messages: The Content-
Disposition Header Field", RFC 2183, August 1997.
[RFC 2231] N. Freed and K. Moore, "MIME Parameter Value and Encoded
Word Extensions: Character Sets, Languages, and Continuations",
RFC 2231, November 1997.
[RFC 2234] D. Crocker and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC 2279] F. Yergeau, "UTF-8, a transformation format of ISO 10646",
RFC 2279, January 1998.
[RFC 2279bis] F. Yergeau, "UTF-8, a transformation format of ISO
10646", draft-yergeau-rfc2279bis-00.txt, April 2002.
[RFC 2298] R. Fajman, "An Extensible Message Format for Message
Disposition Notifications", RFC 2298, March 1998.
[RFC 2373] R. Hinden and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[RFC 2440] J. Callas, L. Donnerhacke, H. Finney, and R. Thayer,
"OpenPGP Message Format", RFC 2440, November 1998.
[RFC 2557] J. Palme, A. Hopmann, and N. Shelness, "MIME Encapsulation
of Aggregate Documents, such as HTML (MHTML)", RFC 2557, March
1999.
[RFC 2606] D. Eastlake and A. Panitz, "Reserved Top Level DNS Names",
RFC 2606, June 1999.
[RFC 2616] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter,
P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.
[RFC 2821] John C. Klensin and Dawn P. Mann, "Simple Mail Transfer
Protocol", RFC 2821, April 2001.
[RFC 2822] P. Resnick, "Internet Message Format", RFC 2822, April
2001.
[RFC 3156] M. Elkins, D. Del Torto, R. Levien, and T. Roessler, "MIME
Security with OpenPGP", RFC 3156, August 2001.
C. H. Lindsey [Page 101]
News Article Format February 2003
[RFC 3282] H. Alvestrand, "Content Language Headers", RFC 3282, May
2002.
[RFC 822] D. Crocker, "Standard for the Format of ARPA Internet Text
Messages.", STD 11, RFC 822, August 1982.
[RFC 850] Mark R. Horton, "Standard for interchange of Usenet
messages", RFC 850, June 1983.
[RFC 976] Mark R. Horton, "UUCP mail interchange format standard",
RFC 976, February 1986.
[Son-of-1036] Henry Spencer, "News article format and transmission",
<ftp://ftp.zoo.toronto.edu/pub/news.txt.Z>, June 1994.
[UNICODE 3.0] The Unicode Consortium, "The Unicode Standard - Version
3.0", Addison-Wesley, 2000.
[UNICODE 3.1] The Unicode Consortium, "The Unicode Standard - Version
3.1, being an amendment to [UNICODE 3.0]", Unicode Standard
Annex #27 <http://www.unicode.org/unicode/reports/tr27>, 2001.
[UNICODE 3.2] The Unicode Consortium, "The Unicode Standard - Version
3.2, being an amendment to [UNICODE 3.1]", Unicode Standard
Annex #28 <http://www.unicode.org/unicode/reports/tr28>, 2002.
[USEFOR] This Standard.
12. Acknowledgements
The editor wishes to thank the following members of the IETF Usenet
Format Working Group who made significant contributions to this
endeavour (however, inclusion in this list does not imply that a
person approves of everything contained herein).
Per Abrahamsen Brian Kelly
Peter Alfredsen Evan Kirshenbaum
Russ Allbery Brad Knowles
Greg Andruk Kent Landfield
Ralph Babel David C. Lawrence
Stan Barber Bruce Lilly
Dave Barr Simon Lyall
Ian Bell Todd Michel McComb
G. James Berigan Denis McKeon
Terje Bless Seymour J. Metz
Seth Breidbart John Moreno
Buddha Buck Chris Newman
Forrest J. Cavalier III Dirk Nimmich
Evan Champion Paul Overell
Maurizio Codogno Jacob Palme
Don Croyle Brian Palmer
Matt Curtin Pete Resnick
Bill Davidsen Jon Ribbens
C. H. Lindsey [Page 102]
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Ian Davis Dan Ritter
Jean-Marc Desperrier Thomas Roessler
Martin J. Duerst Doug Royer
Claus Andre Faerber Frederic Senis
Clive D.W. Feather Erland Sommarskog
David Formosa Henry Spencer
Marty Fouts John Stanley
Benjamin Franz Brad Templeton
Andrew Gierth Florian Weimer
Jonathan Grobe Curt Welch
Thomas Gschwind Curtis Whalen
Kai Henningsen Leonid Yegoshin
Lars Magne Ingebrigtsen Jamie Zawinski
13. Contact Address
Editor
Charles. H. Lindsey
5 Clerewood Avenue
Heald Green
Cheadle
Cheshire SK8 3JU
United Kingdom
Phone: +44 161 436 6131
Email: chl@clw.cs.man.ac.uk
[
Working group chair
Position currently vacant.
]
Comments on this draft should preferably be sent to the mailing list
of the Usenet Format Working Group at
usenet-format@landfield.com.
This draft expires six months after the date of publication (see Page
1) (i.e. in Aug 2003).
Appendix A.1 - A-News Article Format
The obsolete "A News" article format consisted of exactly five lines
of header information, followed by the body. For example:
C. H. Lindsey [Page 103]
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Aeagle.642
news.misc
cbosgd!mhuxj!mhuxt!eagle!jerry
Fri Nov 19 16:14:55 1982
Usenet Etiquette - Please Read
body
body
body
The first line consisted of an "A" followed by an article ID
(analogous to a message ID and used for similar purposes). The
second line was the list of newsgroups. The third line was the path.
The fourth was the date, in the format above (all fields fixed
width), resembling an Internet date but not quite the same. The fifth
was the subject.
This format is documented for archeological purposes only. Articles
MUST NOT be generated in this format.
Appendix A.2 - Early B-News Article Format
The obsolete pseudo-Internet article format, used briefly during the
transition between the A News format and the modern format, followed
the general outline of a MAIL message but with some non-standard
headers. For example:
From: cbosgd!mhuxj!mhuxt!eagle!jerry (Jerry Schwarz)
Newsgroups: news.misc
Title: Usenet Etiquette -- Please Read
Article-I.D.: eagle.642
Posted: Fri Nov 19 16:14:55 1982
Received: Fri Nov 19 16:59:30 1982
Expires: Mon Jan 1 00:00:00 1990
body
body
body
The From-header contained the information now found in the Path-
header, plus possibly the full name now typically found in the From-
header. The Title-header contained what is now the Subject-content.
The Posted-header contained what is now the Date-content. The
Article-I.D.-header contained an article ID, analogous to a message
ID and used for similar purposes. The Newsgroups- and Expires-headers
were approximately as now. The Received-header contained the date
when the latest relaying agent to process the article first saw it.
All dates were in the above format, with all fields fixed width,
resembling an Internet date but not quite the same.
This format is documented for archeological purposes only. Articles
MUST NOT be generated in this format.
C. H. Lindsey [Page 104]
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Appendix A.3 - Obsolete Headers
Early versions of news software following the modern format sometimes
generated headers like the following:
Relay-Version: version B 2.10 2/13/83; site cbosgd.UUCP
Posting-Version: version B 2.10 2/13/83; site eagle.UUCP
Date-Received: Friday, 19-Nov-82 16:59:30 EST
Relay-Version contained version information about the relaying agent
that last processed the article. Posting-Version contained version
information about the posting agent that posted the article. Date-
Received contained the date when the last relaying agent to process
the article first saw it (in a slightly nonstandard format).
In addition, this present standard obsoletes certain headers defined
in [Son-of-1036] (see 6.22):
Also-Control: cancel <9urrt98y53@site.example>
See-Also: <i4g587y@site1.example> <kgb2231+ee@site2.example>
Article-Names: comp.foo:charter
Article-Updates: <i4g587y@site1.example>
Also-Control indicated a control message that was also intended to be
filed as a normal article. See-Also listed related articles, but
without the specific relationship with followups that pertains to the
References-header. Article-Names indicated some special significance
of that article in relation to the indicated newsgroup. Article-
Updates indicated that an earlier article was updated, without at the
same time being superseded.
These headers are documented for archeological purposes only.
Articles containing these headers MUST NOT be generated.
Appendix A.4 - Obsolete Control Messages
This present standard obsoletes certain control messages defined in
[RFC 1036] (see 7.5), all of which had the effect of requesting a
description of a relaying or serving agent's software, or its peering
arrangements with neighbouring sites, to be emailed to the article's
reply address. Whilst of some utility when Usenet was much smaller
than it is now, they had become no more than a tool for the malicious
sending of mailbombs. Moreover, many organizations now consider
information about their internal connectivity to be confidential.
version
sendsys
whogets
senduuname
"Version" requested details of the transport software in use at a
site. "Sendsys" requested the full list of newsgroups taken, and the
peering arrangements. "Who gets" was similar, but restricted to a
named newsgroup. "Senduuname" resembled "sendsys" but restricted to
C. H. Lindsey [Page 105]
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the list of peers connected by UUCP.
Historically, a checkgroups body consisting of one or two lines, the
first of the form "-n newsgroup", caused check-groups to apply to
only that single newsgroup.
Historically, an article posted to a newsgroup whose name had exactly
three components of which the third was "ctl" signified that article
was to be taken as a control message. The Subject-header specified
the actions, in the same way the Control-header does now.
These forms are documented for archeological purposes only; they MUST
NO LONGER be used.
Appendix B - Collected Syntax
Appendix B.1 - Characters, Atoms and Folding
In the following syntactic rules, numbers in the left hand margin
indicate rules taken from other documents, specifically:
2 from [RFC 2822] with the exception of those elements described
therein as "obsolete";
3 from [RFC 2373];
4 from [RFC 2234];
5 from [RFC 2045].
Where the number is followed by an asterisk ('*'), it indicates that
the rule in question has been modified for the purposes of this
standard.
4 ALPHA = %x41-5A / ; A-Z
%x61-7A ; a-z
2 CFWS = *([FWS] comment) ( ([FWS] comment) / FWS )
4 CR = %x0D ; carriage return
4 CRLF = CR LF
4 DIGIT = %x30-39 ; 0-9
4 DQUOTE = %d34 ; quote mark
2 FWS = ([*WSP CRLF] 1*WSP); folding whitespace
4 HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
4 HTAB = %x09 ; horizontal tab
4 LF = %x0A ; line feed
2 NO-WS-CTL = %d1-8 / ; US-ASCII control characters
%d11 / ; which do not include the
%d12 / ; carriage return, line feed,
%d14-31 / ; and whitespace characters
%d127
4 SP = %x20 ; space
4 WSP = SP / HTAB ; whitespace characters
C. H. Lindsey [Page 106]
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UTF8-2 = %xC2-DF UTF8-tail
UTF8-3 = %xE0 %xA0-BF UTF8-tail /
%xE1-EC 2(UTF8-tail) /
%xED %x80-9F UTF8-tail /
%xEE-EF 2(UTF8-tail)
UTF8-4 = %xF0 %x90-BF 2(UTF8-tail) /
%xF1-F7 3(UTF8-tail)
UTF8-5 = %xF8 %x88-BF 3(UTF8-tail) /
%xF9-FB 4(UTF8-tail)
UTF8-6 = %xFC %x84-BF 4(UTF8-tail) /
%xFD 5(UTF8-tail)
UTF8-tail = %x80-BF
UTF8-xtra-char = UTF8-2 / UTF8-3 / UTF8-4 / UTF8-5 / UTF8-6
2 atext = ALPHA / DIGIT /
"!" / "#" / ; Any character except
"$" / "%" / ; controls, SP, and specials.
"&" / "'" / ; Used for atoms
"*" / "+" /
"-" / "/" /
"=" / "?" /
"^" / "_" /
"`" / "{" /
"|" / "}" /
"~"
2 atom = [CFWS] 1*atext [CFWS]
2 ccontent = ctext / quoted-pair / comment
2 comment = "(" *([FWS] ccontent) [FWS] ")"
2* ctext = NO-WS-CTL / ; all of <text> except
%d33-39 / ; SP, HTAB, "(", ")"
%d42-91 / ; and "\"
%d93-126 /
UTF8-xtra-char
2 dcontent = dtext / quoted-pair
2 dot-atom = [CFWS] dot-atom-text [CFWS]
2 dot-atom-text = 1*atext *( "." 1*atext )
2 dtext = NO-WS-CTL / ; Non white space controls
%d33-90 / ; The rest of the US-ASCII
%d94-126 ; characters not including
; "[", "]", or "
2 phrase = 1*word
2 qcontent = qtext / quoted-pair
2* qtext = NO-WS-CTL / ; all of <text> except
%d33 / ; SP, HTAB, "\" and DQUOTE
%d35-91 /
%d93-126 /
UTF8-xtra-char
2 quoted-pair = "\" text
2 quoted-string = [CFWS] DQUOTE
*( [FWS] qcontent ) [FWS]
DQUOTE [CFWS]
C. H. Lindsey [Page 107]
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2 specials = "(" / ")" / ; Special characters used in
"<" / ">" / ; other parts of the syntax
"[" / "]" /
":" / ";" /
"@" / "\" /
"," / "." /
DQUOTE
strict-qcontent = strict-qtext / strict-quoted-pair
strict-quoted-pair = "\" strict-text
strict-quoted-string
= [CFWS] DQUOTE
*( [FWS] strict-qcontent ) [FWS]
DQUOTE [CFWS]
strict-qtext = NO-WS-CTL / ; qtext restricted to
%d33 / ; US-ASCII
%d35-91 /
%d93-126
strict-text = %d1-9 / ; text restricted to
%d11-12 / ; US-ASCII
%d14-127
2* text = %d1-9 / ; all UTF-8 characters except
%d11-12 / ; US-ASCII NUL, CR and LF
%d14-127 /
UTF8-xtra-char
5 tspecials = "(" / ")" / "<" / ">" / "@" /
"," / ";" / ":" / "\" / DQUOTE /
"/" / "[" / "]" / "?" / "="
2* unstructured = 1*( [FWS] utext ) [FWS]
2* utext = NO-WS-CTL / ; Non white space controls
%d33-126 / ; The rest of US-ASCII
UTF8-xtra-char
2 word = atom / quoted-string
Appendix B.2 - Basic Forms
2 addr-spec = local-part "@" domain
2 address = mailbox / group
2 address-list = address *( "," address )
2 angle-addr = [CFWS] "<" addr-spec ">" [CFWS]
article = 1*( header CRLF ) separator body
5* attribute = [CFWS] token [CFWS]
body = *( *998text CRLF )
2 display-name = phrase
2 date = day month year
2 date-time = [ day-of-week "," ] date FWS time [CFWS]
2 day = [FWS] 1*2DIGIT
2 day-name = "Mon" / "Tue" / "Wed" / "Thu" /
"Fri" / "Sat" / "Sun"
2 day-of-week = [FWS] day-name
2 domain = dot-atom / domain-literal
2 domain-literal = [CFWS] "[" *([FWS] dcontent) [FWS] "]" [CFWS]
2 group = display-name ":" [ mailbox-list / CFWS ] ";"
[CFWS]
header-name = 1*name-character *( "-" 1*name-character )
C. H. Lindsey [Page 108]
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2 hour = 2DIGIT
2* local-part = dot-atom / strict-quoted-string
2 mailbox = name-addr / addr-spec
2 mailbox-list = mailbox *( "," mailbox )
2 minute = 2DIGIT
2 month = FWS month-name FWS
2 month-name = "Jan" / "Feb" / "Mar" / "Apr" /
"May" / "Jun" / "Jul" / "Aug" /
"Sep" / "Oct" / "Nov" / "Dec"
2 name-addr = [display-name] angle-addr
name-character = ALPHA / DIGIT
other-header = header-name ":" 1*SP other-content
other-content = <the content of a header defined by some
other standard>
extension-parameter = <a parameter not defined by this standard>
5 parameter = attribute "=" value
2 second = 2DIGIT
separator = CRLF
2 time = time-of-day FWS zone
2 time-of-day = hour ":" minute [ ":" second ]
5 token = 1*<any (US-ASCII) CHAR except SP, CTLs,
or tspecials>
5 value = [CFWS] token [CFWS] / quoted-string
5* x-token = "x-" token
2 year = 4*DIGIT
2* zone = (( "+" / "-" ) 4DIGIT) / "UT" / "GMT"
Appendix B.3 - Headers
Appendix B.3.1 - Header outlines
header = other-header /
Date-header /
From-header /
Message-ID-header /
Subject-header /
Newsgroups-header /
Path-header /
Reply-To-header /
Sender-header /
Organization-header /
Keywords-header /
Summary-header /
Distribution-header /
Followup-To-header /
Mail-Copies-To-header /
Posted-And-Mailed-header /
References-header /
Expires-header /
Archive-header /
Control-header /
Approved-header /
Supersedes-header /
Xref-header /
C. H. Lindsey [Page 109]
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Lines-header /
User-Agent-header /
Injector-Info-header /
Complaints-To-header
Approved-content = From-content
Approved-header = "Approved" ":" SP Approved-content
*( ";" extension-parameter )
Archive-content = [CFWS] ("no" / "yes" ) [CFWS]
Archive-header = "Archive" ":" SP Archive-content
*( ";" ( Archive-parameter /
extension-parameter ) )
Archive-parameter = <a parameter with attribute "filename"
and any value>
Complaints-To-content= address-list
Complaints-To-header = "Complaints-To" ":" SP Complaints-To-content
Control-content = [CFWS] control-message [CFWS]
Control-header = "Control" ":" SP Control-content
*( ";" extension-parameter )
Date-content = date-time
Date-header = "Date" ":" SP Date-content
Distribution-content = distribution *( dist-delim distribution )
Distribution-header = "Distribution" ":" SP Distribution-content
*( ";" extension-parameter )
Expires-content = date-time
Expires-header = "Expires" ":" SP Expires-content
*( ";" extension-parameter )
Followup-To-content = Newsgroups-content /
[FWS] %x70.6F.73.74.65.72 [FWS]
; which is a case-sensitive "poster"
Followup-To-header = "Followup-To" ":" SP Followup-To-content
*( ";" extension-parameter )
From-content = mailbox-list
From-header = "From" ":" SP From-content
Injector-Info-content= [CFWS] path-identity [CFWS]
Injector-Info-header = "Injector-Info" ":" SP Injector-Info-content
*( ";" ( Injector-Info-parameter /
extension-parameter ) )
Injector-Info-parameter
= posting-host-parameter /
posting-account-parameter /
posting-sender-parameter /
posting-logging-parameter /
posting-date-parameter
Keywords-content = phrase *( "," phrase )
Keywords-header = "Keywords" ":" SP Keywords-content
Lines-content = [CFWS] 1*DIGIT [CFWS]
Lines-header = "Lines" ":" SP Lines-content
*( ";" extension-parameter )
Mail-Copies-To-content
= copy-addr / [CFWS] ( "nobody" /
"poster" ) [CFWS]
Mail-Copies-To-header= "Mail-Copies-To" ":" SP Mail-Copies-To-content
Message-ID-content = [FWS] msg-id [FWS]
C. H. Lindsey [Page 110]
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Message-ID-header = "Message-ID" ":" SP Message-ID-content
Newsgroups-content = [FWS] newsgroup-name
*( [FWS] ng-delim [FWS] newsgroup-name )
[FWS]
Newsgroups-header = "Newsgroups" ":" SP Newsgroups-content
*( ";" extension-parameter )
Organization-content = unstructured
Organization-header = "Organization" ":" SP Organization-content
Path-content = [FWS] *( path-identity [FWS]
path-delimiter [FWS]
) tail-entry [FWS]
Path-header = "Path" ":" SP Path-content
*( ";" extension-parameter )
Posted-And-Mailed-content
= [CFWS] ( "yes" / "no" ) [CFWS]
Posted-And-Mailed-header
= "Posted-And-Mailed" ":" SP
Posted-And-Mailed-content
*( ";" extension-parameter )
References-content = [CFWS] msg-id *( CFWS msg-id ) [CFWS]
References-header = "References" ":" SP References-content
Reply-To-content = address-list
Reply-To-header = "Reply-To" ":" SP Reply-To-content
Sender-content = mailbox
Sender-header = "Sender" ":" SP Sender-content
Subject-content = [ [FWS] back-reference ] pure-subject
Subject-header = "Subject" ":" SP Subject-content
Summary-content = unstructured
Summary-header = "Summary" ":" SP Summary-content
Supersedes-content = [CFWS] msg-id [CFWS]
Supersedes-header = "Supersedes" ":" SP Supersedes-content
User-Agent-content = product *( CFWS product )
User-Agent-header = "User-Agent" ":" SP User-Agent-content
*( ";" extension-parameter )
Xref-content = [CFWS] server-name 1*( CFWS location ) [CFWS]
Xref-header = "Xref" ":" SP Xref-content
*( ";" extension-parameter )
Appendix B.3.2 - Control-message outlines
control-message = <empty> /
Newgroup-message /
Rmgroup-message /
Mvgroup-message /
Checkgroup-message /
Cancel-message /
Ihave-message /
Sendme-message
Cancel-arguments = CFWS msg-id [CFWS]
Cancel-message = "cancel" Cancel-arguments
Checkgroup-arguments = [ chkscope ] [ chksernr ]
Checkgroup-message = "checkgroups" Checkgroup-arguments
Ihave-arguments = relayer-name
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Ihave-message = "ihave" Ihave-arguments
Mvgroup-arguments = CFWS newsgroup-name CFWS newsgroup-name
[ CFWS newgroup-flag ]
Mvgroup-message = "mvgroup" Mvgroup-arguments
Newgroup-arguments = CFWS newsgroup-name [ CFWS newgroup-flag ]
Newgroup-message = "newgroup" Newgroup-arguments
Rmgroup-arguments = CFWS newsgroup-name
Rmgroup-message = "rmgroup" Rmgroup-arguments
Sendme-arguments = Ihave-arguments
Sendme-message = "sendme" Sendme-arguments
Appendix B.3.3 - Other header rules
article-locator = 1*( %x21-27 / %x29-3A / %x3C-7E )
; US-ASCII printable characters
; except'(' and ';'
article-size = 1*DIGIT
back-reference = %x52.65.3A.20
; which is a case-sensitive "Re: "
batch = 1*( batch-header article )
batch-header = "#!" SP rnews SP article-size CRLF
checkgroups-body = *( valid-group CRLF )
chkscope = 1*( CFWS ["!"] newsgroup-name )
chksernr = CFWS "#" 1*DIGIT
combiner-ASCII = DIGIT / ALPHA / "+" / "-" / "_"
combiner-base = combiner-ASCII / combiner-extended
combiner-extended = <any character with a Unicode code value of
0080 or greater but excluding any character
in Unicode categories Cc, Cf, Cs, M* and Z*>
combiner-mark = <any character with a Unicode code value of
0080 or greater and in Unicode category M*>
component = 1*component-grapheme
component-grapheme = combiner-base *combiner-mark
copy-addr = address-list
dist-delim = ","
distribution = [FWS] distribution-name [FWS]
distribution-name = ALPHA 1*distribution-rest
distribution-rest = ALPHA / "+" / "-" / "_"
groupinfo-body = [ newsgroups-tag CRLF ]
newsgroups-line CRLF
3 hex4 = 1*4HEXDIG
3 hexpart = hexseq / hexseq "::" [ hexseq ] /
"::" [ hexseq ]
3 hexseq = hex4 *( ":" hex4 )
host-value = dot-atom /
[ dot-atom ":" ]
( IPv4address / IPv6address )
; see [RFC 2373]
2 id-left = dot-atom-text / no-fold-quote
2 id-right = dot-atom-text / no-fold-literal
ihave-body = *( msg-id CRLF )
3 IPv4address = 1*3DIGIT "." 1*3DIGIT "."
1*3DIGIT "." 1*3DIGIT
3 IPv6address = hexpart [ ":" IPv4address ]
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location = newsgroup-name ":" article-locator
moderation-flag = %x28.4D.6F.64.65.72.61.74.65.64.29
; case sensitive "(Moderated)"
2* msg-id = "<" id-left "@" id-right ">"
newgroup-flag = "moderated"
newsgroup-description
= utext *( *WSP utext )
newsgroup-name = component *( "." component )
newsgroups-line = newsgroup-name
[ 1*HTAB newsgroup-description ]
[ 1*WSP moderation-flag ]
newsgroups-tag = %x46.6F.72 SP %x79.6F.75.72 SP
%x6E.65.77.73.67.72.6F.75.70.73 SP
%x66.69.6C.65.3A
; case sensitive
; "For your newsgroups file:"
ng-delim = ","
2* no-fold-literal = "[" *( dtext / "\[" / "\]" / "\\" ) "]"
2* no-fold-quote = DQUOTE
*( strict-qtext / "\\" / "\" DQUOTE )
qspecial
*( strict-qtext / "\\" / "\" DQUOTE )
DQUOTE
path-delimiter = "/" / "?" / "%" / "," / "!"
path-identity = ( ALPHA / DIGIT )
*( ALPHA / DIGIT / "-" / "." / ":" / "_" )
posting-account-parameter
= <a parameter with attribute "posting-account"
and any value>
posting-date-parameter
= <a parameter with attribute "posting-date"
and value some date-time>
posting-host-parameter
= <a parameter with attribute "posting-host"
and value some host-value>
posting-logging-parameter
= <a parameter with attribute "logging-data"
and any value>
posting-sender-parameter
= <a parameter with attribute "sender"
and value some sender-value>
product = [CFWS] token [CFWS] [ "/" product-version ]
product-version = [CFWS] token [CFWS]
pure-subject = unstructured
qspecial = "(" / ")" / ; same as specials except
"<" / ">" / ; "\" and DQUOTE quoted
"[" / "]" /
":" / ";" /
"@" / "\\" /
"," / "." /
"\" DQUOTE
relayer-name = path-identity
rnews = %x72.6E.65.77.73 ; case sensitive "rnews"
sender-value = mailbox / "verified"
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sendme-body = ihave-body
server-name = path-identity
tail-entry = path-identity
valid-group = newsgroups-line
Appendix C - Notices
Intellectual Property
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
C. H. Lindsey [Page 114]
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
C. H. Lindsey [Page 115]
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