INTERNET-DRAFT                               Charles H. Lindsey
Usenet Format Working Group                  University of Manchester
                                             July 2005
                                             January 2006

                News Article Architecture and Protocols
                   <draft-ietf-usefor-usepro-04.txt>
                   <draft-ietf-usefor-usepro-05.txt>

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   This Internet-Draft will expire in January July 2006.

Abstract

   This Draft, together with its companion draft [USEFOR], are
   intended as standards track documents, together obsoleting RFC
   1036, which itself dates from 1987.

   This Standard defines the architecture of Netnews systems and
   specifies the requirements to be met by software which originates,
   distributes, stores and displays Netnews articles.

   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.

   A companion Current Best Current Practice document [USEAGE], addressing
   requirements which are present for Social rather than Normative
   reasons is in preparation.

                News Article Architecture and Protocols        July 2005

[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
                News Article Architecture and Protocols     January 2006

when it is accepted as an RFC with the status of a proposed or draft
standard.]

[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 references to
the RFC arising from the series of drafts draft-ietf-nntpext-base-*.txt,
which has now passed its IETF last call.]

                           Table of Contents

1.  Introduction ..................................................    4
  1.1.  Basic Concepts ............................................    4
  1.2.  Objectives ................................................    5    4
  1.3.  Historical Outline ........................................    5
2.  Definitions, Notations and Conventions ........................    6    5
  2.1.  Definitions ...............................................    6    5
  2.2.  Defining the Architecture .................................    7    6
  2.3.  Identification of news-servers news servers ............................    8    7
  2.4.  Variant Header Fields .....................................    9    8
  2.5.  Textual Notations .........................................    9    8
3.  Changes to the existing protocols .............................   10    9
  3.1.  Principal  Protocol Changes .........................................   10 ..........................................    9
  3.2.  Transitional Arrangements .................................   11   10
4.  Transport .....................................................   12   11
5.  Definition of new Media Types .................................   13   12
  5.1.  Application/news-transmission .............................   13   12
  5.2.  Message/news obsoleted ....................................   14   13
  5.3.  Application/news-groupinfo ................................   14   13
  5.4.  Application/news-checkgroups ..............................   15   14
6.  Control Messages ..............................................   16   15
  6.1.  Digital Signature of Header Fields ........................   17   16
  6.2.  Group Control Messages ....................................   17   16
    6.2.1.  The 'newgroup' Control Message ........................   18   16
      6.2.1.1.  The Body of the 'newgroup' Control Message ........   18   17
      6.2.1.2.  Initial Articles ..................................   18   17
      6.2.1.3.  Example ...........................................   19   18
    6.2.2.  The 'rmgroup' Control Message .........................   20   19
      6.2.2.1.  Example ...........................................   20   19
    6.2.3.  The 'mvgroup' Control Message .........................   20   19
      6.2.3.1.  Example ...........................................   22   21
    6.2.4.  The 'checkgroups' Control Message .....................   23   21
  6.3.  Cancel ....................................................   24   23
  6.4.  Ihave, sendme .............................................   25   23
  6.5.  Obsolete control messages.  ...............................   26   25
7.  Duties of Various Agents ......................................   26   25
  7.1.  General principles to be followed .........................   27

                News Article Architecture and Protocols        July 2005   26
  7.2.  Duties of an Injecting Agent ..............................   27   26
    7.2.1.  Proto-articles ........................................   28   27
    7.2.2.  Procedure to be followed by Injecting Agents ..........   28   27
                News Article Architecture and Protocols     January 2006

    7.2.3.  Procedure for Forwarding to a Moderator ...............   31   29
  7.3.  Duties of a Relaying Agent ................................   31   30
    7.3.1.  Path Header Field Example .............................   34   33
  7.4.  Duties of a Serving Agent .................................   35   34
  7.5.  Duties of a Posting Agent .................................   36   35
  7.6.  Duties of a Followup Agent ................................   37   36
    7.6.1.  Construction of the References header field ...........   37   36
  7.7.  Duties of a Reading Agent .................................   38   37
  7.8.  Duties of a Moderator .....................................   38   37
  7.9.  Duties of a Gateway .......................................   40   39
    7.9.1.  Duties of an Outgoing Gateway .........................   41   40
    7.9.2.  Duties of an Incoming Gateway .........................   42   41
    7.9.3.  Example ...............................................   44   43
8.  Security and Related Considerations ...........................   45   44
  8.1.  Leakage ...................................................   45   44
  8.2.  Attacks ...................................................   45   44
    8.2.1.  Denial of Service .....................................   45   44
    8.2.2.  Compromise of System Integrity ........................   46
  8.3.  Liability .................................................   48   47
9.  IANA Considerations ...........................................   48   47
10.  References ...................................................   48   47
  10.1.  Normative References .....................................   48   47
  10.2.  Informative References ...................................   49   48
11.  Acknowledgements .............................................   50   49
12.  Contact Address ..............................................   50
Appendix A.1 - A-News Article Format ..............................   50
Appendix A.2 - Early B-News Article Format ........................   51   49
Appendix A.3 A - Obsolete Control Messages ..........................   52 ............................   49
Appendix B - Notices ..............................................   52   50
Appendix C - Change Log ...........................................   53   51
                News Article Architecture and Protocols        July 2005

[This draft [USEPRO] and its partner [USEFOR] are an interim stage in
the splitting into two parts of the earlier draft [ARTICLE].  There     January 2006

1.  Introduction

1.1.  Basic Concepts

   "Netnews" is a
certain amount of material - basic concepts, definitions, etc - which
ultimately need occur in only one set of the documents, protocols for generating, storing and further such
material which may not be needed at all (e.g. terms currently defined
which in the event may not get used). For the moment, all such material
has been retained in the present draft (it being, in any case, easier to
take unwanted stuff out than to put new stuff in). It has also to be
decided, for such material which is needed by both documents, which one
(the "Primary") should contain it and which one should incorporate it by
reference (essentially, this draft is written so that it could be the
Primary).]

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
   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 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 publicly accessible 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).

   An important characteristic of Usenet is the lack of any requirement
   for a central administration or for the establishment of any
   controlling host to manage the network. Nevertheless, administrative
   agencies do exists with varying degrees of authority to establish
   "policies" applicable to particular parts of Usenet.

   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.

                News Article Architecture and Protocols        July 2005
[Could omit that last sentence.]

1.2.  Objectives

   The purpose of this present standard is to define the overall
   architecture 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. A companion standard
   [USEFOR] sets out the canonical format of news articles exchanged
   between the various agents comprising that architecture. In this
   standard, references to individual sections in the companion [USEFOR]
   are prefixed with "F-".

   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".
[It is not clear whether we still need that definition.]
                News Article Architecture and Protocols     January 2006

   It is NOT the purpose of this standard to settle matters of policy,
   nor aspects of software behaviour which do not impinge upon the
   generation, transmission, storage and reception of articles, nor how
   the authority of various agencies to create such policies and to
   exercise control or oversight of the various parts of Usenet is
   established. For these purposes, a separate Best Current Practice
   document [USEAGE] is being provided.

   Nevertheless, it is assumed that such agencies with the necessary
   authority 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,

   For an article format vaguely resembling
   Internet Mail was devised and used briefly.  Both account of those the earlier formats
   are completely obsolete; they are documented in Appendix A.1 and
   Appendix A.2 for historical reasons only.  With publication of [RFC
   850] used in 1983, news articles came Netnews prior to closely resemble Internet Mail
   messages, with some restrictions and some additional header fields. [RFC 1036] in 1987 updated [RFC 850] without making major changes.

   A Draft
   1036], see Henry Spencer's 1994 draft, popularly referred to as "Son
   of 1036" [Son-of-1036] was
   written in 1994 by Henry Spencer.  Much [Son-of-1036], which has recently been republished as an
   Informational RFC.
[That is taken directly from Son a tentative statement, which may need revision.]

   Although never adopted as a formal standard, [Son-of-1036] had a
   considerable effect on the development of
   1036, Netnews and hence on these
   present standards, and it is hoped that we have followed its spirit
   and intentions.

[It is anticipated that [Son-of-1036] will shortly be published as an
informational RFC (for purposes of historical documentation only), in
which case most historical information can be removed from this draft,
including the whole of Appendix A.1 and Appendix A.2.]

                News Article Architecture and Protocols        July 2005

2.  Definitions, Notations and Conventions

2.1.  Definitions

   An "article" is the unit of news, synonymous with an [RFC 2822]
   "message".  A "proto-article" is one that has not yet been injected
   into

   All the news system.  In constrast technical terms defined in F-1.5 are to an article, a proto- article
   may lack some mandatory header fields

   A "message identifier" (F-3.1.3) 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 be considered as
   defined also, with the same
   message identifier are treated as if they meaning, in this standard.  In addition,
   some further terms are the same article
   regardless of any differences defined here, and in the body or header fields. following section.

   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 "hierarchy" 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 the set of all newsgroups whose names share a first
   component
   <component> (as defined in F-3.1.5).  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 for submission to a posting agent.

   The
   poster is analogous "semantic content" (often abbreviated to [RFC 2822]'s author.

   A "reader" is just "content" when the person or software reading news articles.

   A "followup"
   context is an article containing a response to the contents clear) of
   an earlier article, its "precursor". Every followup includes a
   References header field identifying that precursor (but note that
   non-followup articles may also use a References header field).

   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.

   A "sender" is the person or software (usually, but not always, the
   same as the poster) responsible for semantic interpretation;
   i.e. what remains after unfolding it and removing its field name with
   its colon and any leading and trailing whitespace and, in the operation case of the posting
   agent or, which amounts to the same thing, for passing the article to
   the injecting agent.
[Is the definition in RFC 2822 sufficient?]
   structured header fields only, ignoring comments and other
   semantically invisible items and replacing white space by a single
   SP.

                News Article Architecture and Protocols        July 2005

   A "control message" is an article which is marked as containing
   control information; a "serving agent" (and in some cases a "relaying
   agent") receiving such an article may (subject to the policies
   observed at that site) take actions beyond just filing and passing on
   the article.

   The "semantic content" (often abbreviated to just "content" when the
   context is clear) of a header field is its semantic interpretation;
   i.e. what remains after unfolding it and removing its field name with
   its colon and any leading and trailing whitespace and, in the case of
   structured header fields only, ignoring comments and other
   semantically invisible items and replacing white space by a single
   SP.

2.2.  Defining the Architecture     January 2006

2.2.  Defining the Architecture

   A Netnews system is a distributed database composed of "agents" agents of
   various types which, acting together according to the protocols
   defined in section 7 of this standard, causes articles to be
   propagated throughout the system and to be made available to its
   readers. The protocols ensure that all copies of a given article,
   wherever stored, are identical apart from those header fields defined
   as variant (2.4).  For explaining the working of the protocols, it is
   convenient to define particular sub-categories of agent as follows:

   A "posting agent" is the software that assists posters to prepare
   proto-articles in compliance with [USEFOR].  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 "reading agent" is software which presents articles to a reader.

   A "followup agent" is a combination of reading agent and posting
   agent that aids in the preparation and posting of a followup.

   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 "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.
[There is a suggestion that "serving agent" should be changed to
"storage agent" throughout.]

   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.

                News Article Architecture and Protocols        July 2005

   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 the [USEFOR] news format
   and those using other formats.

   Posting, reading and followup agents (which are usually just
   different services provided by the same piece of software) are known
   collectively as together
   comprise the "user agents".

   Injecting, agents" defined in F-1.5.

                News Article Architecture and Protocols     January 2006

   Likewise, injecting, relaying and serving agents (which are often
   just different services provided by the same piece of software) are known
   collectively as "news-servers".
   together comprise the "news servers".

2.3.  Identification of news-servers

   News-servers news servers

[The format of the Path header is still under discussion (ticket #1047).
Hence the following texts are tentative, and will need to be changed (as
will the associated protocols in 7.3).  Moreover, there are two
alternative texts which have been proposed:]

   In order to record the passage of articles through the network, news
   servers need to identify themselves by inserting their public
   name, in the form means of a <path-identity>
   (F-3.1.6), into which can appear in Path, Injection-Info and Xref header
   fields. An injecting agent MUST
   identify itself with the same Whatever <path-identity> is used in both the Path and
   Injection-Info header fields, and a serving agent field
   SHOULD use the same
   <path-identity> be used also in both Path and Xref any Injection-Info header fields.

   The following possibilities are available when choosing a <path-
   identity>, but some of them are less suited field (and it would
   be normal to providing a unique
   identity use it in any Xref header field also).
[Maybe that last sentence moves elsewhere.]

        NOTE: Such <path-identity>s may also be suitable for sending
        email to news server administrators (see [USEAGE]).

[1st alternative]

   <Path-identity>s can take the news-server concerned and are NOT RECOMMENDED, as
   shown: following forms (in decreasing order of
   preference):

   1. 1. A fully qualified domain name (FQDN) associated with that SHOULD be resolvable
      in the DNS (whether via an "A" A, AAAA or
      "AAAA" MX record (or or an equivalent "CNAME"), which SHOULD identify
      the actual host inserting this <path-identity> and, ideally,
      should
      CNAME), thus guaranteeing a unique identity. Ideally, it will also be "mailable" (see below).

   2. An encoding of an IP address - <IPv4address> or <IPv6address> [RFC
      3986] - which SHOULD be
      provide a publicly recognized address means to contact the administrators by email (according
      to [RFC 1918]
      for 2142], the actual host, as above. This option SHOULD NOT be used if
      an FQDN forms "usenet@server" and "news@server" are
      common addresses for that host is available.

   3. A fully qualified domain name (FQDN) associated with an "MX"
      record, which MUST be "mailable".

   4. a news server administrator).

   2. Some other (arbitrary) name believed to be unique and registered
      at least with all other news-servers news servers sending articles directly to
      the given one. The news-server administrator is responsible for
      choosing an appropriate name (and will bear the consequences of an
      inappropriate choice). This option SHOULD NOT be used unless the earlier options are
      option is unavailable (e.g. because the host server in question is not
      connected to the Internet), or unless it is of longstanding usage
      and cessation would be unduly disruptive.

                News Article Architecture and Protocols        July 2005

        NOTE: The syntax permits disruptive, or unless the colon character (which, prior to
        this standard, was a <path-delimiter>) within any <path-
        identity> which earlier
      option is in the form of an <IPv6address>.  It would
        therefor be unwise to choose, provided as such a name, anything composed
        solely from four (or less) hexadecimal digits.

   The FQDN of a news-server is "mailable" if its administrators well.

[2nd alternative]

   <Path-identity>s can be
   reached by email using both of take the following forms "usenet@" that FQDN and
   "news@" (in decreasing order of
   preference):

   1. A fully qualified domain name (FQDN) that FQDN, in conformity with [RFC 2142].

   For can be resolved to an injecting agent prepending
      email server via an MX, A or AAAA record according to a Path header field (7.2.2), the
   <path-identity> MUST be option 1 or 3
      procedures of [RFC 2821]; this guarantees that the name is unique,
      and makes it easy to contact the FQDN MUST be mailable, administrators if needed.

                News Article Architecture and Protocols     January 2006

   2. A fully qualified domain name (FQDN) that is guaranteed to be
      unique by the administrators of the domain; for instance, the
      uniqueness of "server.example.org" could be guaranteed by the
      administrator of "example.org" even if nothing is stored in the agent offers its services
      DNS for that name.

   3. Some other (arbitrary) name believed to be unique and registered
      at least with all other news-servers sending articles directly to
      the general public given one. This option SHOULD NOT be used unless the form
   "abuse@" that FQDN MUST also earlier
      options are unavailable, or unless the name is of longstanding
      usage and cessation would be available, unduly disruptive, or unless a more specific
   complaints address has been one of
      the earlier options is provided in as well.

   According to [RFC 2142]], the forms "usenet@server" and "news@server"
   are common addresses for a news server administrator.
[end of alternatives]

        NOTE: A news server administrator who chooses a name which turns
        out not to be unique will have to bear the consequences.

        NOTE: The syntax permits the colon character (which, prior to
        this standard, was a <complainto-param> <path-delimiter>) within any <path-
        identity> which is in the form of an
   Injection-Info header field (F-3.2.14). <IPv6address>.  It would
        therefore be unwise to choose, as such a name, anything composed
        solely from four (or less) hexadecimal digits.

2.4.  Variant Header Fields

   Header fields 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 some future) standard.
   Typically, these header fields 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. A variant header
   field MAY be placed anywhere within the header fields (though placing
   it first is recommended).

   The following header fields are classified as "variant":
     o Path (F-3.1.6) - augmented at each relaying agent that an article
       passes through.
     o Xref (F-3.2.11) - used to keep track of the <article-locator>s of
       crossposted articles so that reading agents serviced by a
       particular serving agent can mark such articles as read.
     o Injection-Info (F-3.2.14) is also considered variant in some
       special situations involving reinjection (7.2 and 7.2.2).

2.5.  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.

                News Article Architecture and Protocols     January 2006

        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.

                News Article Architecture and Protocols        July 2005

   "US-ASCII" is short for "the ANSI X3.4 character set" [ANSI 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].

        NOTE: The use of "MUST" or "SHOULD" implies a requirement that
        would or could lead to interoperability problems if not
        followed.

        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, header fields 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
   hierarchy "example.*" is also used as a sample hierarchy.
   Information on the ".example" top level domain is in [RFC 2606].

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, service
   (3.2), 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 <comment>s in
       header fields are supported in all newly defined header fields
       and in header fields inherited from [RFC 2822].  They are,
       however, still disallowed for performance and/or compatibility
       reasons in the Message-ID, Newsgroups, Path, Followup-To,
       Control, Supersedes, Distribution, Xref syntax and Lines header fields.
     o Whitespace is permitted
   format are documented in Newsgroups header fields, permitting
       folding of such header fields. Indeed, all header fields can now
       be folded.

                News Article Architecture F-Appendix B and Protocols        July 2005

     o An enhanced syntax for the Path header field enables the
       injection point of changes to control messages
   and the route taken by an article to be
       determined with certainty.
     o MIME is recognized as an integral part of Netnews. protocols are documented below.

3.1.  Protocol Changes

     o There is a new Control message 'mvgroup' to facilitate moving a
       group to a different place (name) in a hierarchy.
     o There is Certain Control messages (Appendix A) have been made obsolete,
       and the special significance of "cmsg" when at the start of a new mandatory Injection-Date
                News Article Architecture and Protocols     January 2006

       Subject header field to
       facilitate the rejection of stale articles. has been removed (section 6).
     o There Additional media types are new optional header fields defined, Archive,
       Injection-Info and User-Agent, leading to increased
       functionality.
     o Certain header fields and Control defined for better structuring of
       control messages (F-3.3 (5.3 and Appendix
       A.3) have been made obsolete. 5.4).
     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, news servers, 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 servers is rather small, at least so far as the main "backbone"
   of Usenet is concerned, and many of the new features are already
   supported. Contrariwise, there are a great number of implementations
   of user agents, installed on a vastly greater number of small sites.
   Therefore, the new functionality has been designed so that existing
   user 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 <comment>s have been prohibited in the case of
       those header fields do not affect
       serving and relaying agents. of particular concern to news servers. They
       are unlikely to hinder their proper display in existing reading
       agents except in the case of the References header field in
       agents which thread articles.
       Therefore, it is provided [USEFOR] therefore provides that
       they SHOULD NOT be generated in that case.
     o Because of its importance to all serving agents, the newly
       permitted whitespace
       and folding in Newsgroups header fields newly permitted by
       [USEFOR] SHOULD NOT be generated (though it MUST be accepted);
       this restriction may well be removed in a future version of this
       standard.
     o The new style of Path header
[That last bit needs discussion. It should probably be moved to USEFOR
if it is to be retained.]
     o The new style of Path header field, using "!!" as a <path-
       delimiter>, 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

                News Article Architecture and Protocols        July 2005
       agents are unaffected.
     o The introduction by [USEFOR] 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
                News Article Architecture and Protocols     January 2006

       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 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 Provision is made for relaying and serving agents to use the Date
       header field in the case of articles injected through existing
       agents which do not yet provide an Injection-Date header field.
     o All the header fields newly introduced by this standard [USEFOR] can safely be
       ignored by existing software, albeit with loss of the new
       functionality.

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.

   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.

   In particular, transmission paths MUST convey all header fields
   (including body part header fields and header fields within
   message/rfc822 objects) intact, even if they contain octets in the
   range 128 to 255.  Furthermore, relaying agents MUST, and other
   agents SHOULD, convey lines even if they exceed 998 characters in
   length, especially in article bodies. These requirements include the
   transmissiom paths between posting agents, injecting agents, relaying
   agents, serving agents and reading agents, but NOT the paths

                News Article Architecture and Protocols        July 2005
   traversed by Netnews articles that have been gatewayed into Email
   (7.9.1).
[At some point it will be necessary for the IMAP standards to catch up
with these requirements.]
                News Article Architecture and Protocols     January 2006

5.  Definition of new Media Types

   This standard defines (or redefines) several new Media Types, which
   require to be registered with IANA as provided for in [RFC 2048].

5.1.  Application/news-transmission

   The Media 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 7.2.2) and it is also the preferred method when sending to an
   email-to-news gateway (see 7.9.2).

        NOTE: The benefit of such encapsulation is that it removes
        possible conflict between news and email header fields and it
        provides a convenient way of "tunnelling" a news article through
        a transport medium that does not support 8bit characters.

   The MIME Media Type definition of "application/news-transmission" is:

   MIME type name:           application
   MIME subtype name:        news-transmission
   Required parameters:      none
   Optional parameters:      usage=moderate
                             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:  [USEPRO]
   Body part:                A complete article or proto-article, ready
                             for injection into Netnews, or a batch of
                             such articles in the batch format described
                             in section 6.4.

        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

                News Article Architecture and Protocols        July 2005
        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.

                News Article Architecture and Protocols     January 2006

   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
   batch format defined in section 6.4 MUST be used.

5.2.  Message/news obsoleted

   The Media 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
   not recognize it was counter productive. The Media Type
   "message/rfc822" SHOULD be used in its place.

5.3.  Application/news-groupinfo

   The "application/news-groupinfo" is used in conjunction with the
   "newgroup" (6.2.1) and "mvgroup" (6.2.3) control messages.  The
   <newsgroup-name> in the <newsgroups-line> MUST agree with the
   <newsgroup-name> in the "newgroup" or "mvgroup" control message.  The
   Media Type "application/news-groupinfo" MUST NOT be used except as a
   part of such control messages.

   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 Media Type definition of "application/news-groupinfo" is:

   MIME type name:           application
   MIME subtype name:        news-groupinfo
   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 control message for the creation or
                             modification of a Netnews newsgroup
   Published specification:  [USEPRO]

   The content of the "application/news-groupinfo" body part is defined
   as:

      groupinfo-body      = [ newsgroups-tag CRLF ]
                               newsgroups-line CRLF

                News Article Architecture and Protocols        July 2005
      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:"
                News Article Architecture and Protocols     January 2006

      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.  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.

        NOTE: There is no provision for the use of charsets other than
        US-ASCII within a <newsgroup-description>. Such a facility may
        be provided in a future extension to this standard.
[That may seem harsh, but if we make any such provision now, it will
make life more complicated and restrict our freedom when it comes to the
proposed I18N extension. Therefore I resisted the temptation to include
any charset parameter with this Media Type. Note that this also applies
to the checkgroups message further on.]

5.4.  Application/news-checkgroups

   The "application/news-checkgroups" Media Type is used in conjunction
   with the "checkgroups" control message (6.2.4).  It MUST NOT be used
   except as a part of such control messages.

   The "application/news-checkgroups" body part contains a complete list
   of all the newsgroups in a (sub)hierarchy, their <newsgroup-
   description>s and their moderation status.

   The MIME Media 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
   Published specification:  [USEPRO]

                News Article Architecture and Protocols        July 2005

   The content of the "application/news-checkgroups" body part is
   defined as:

                News Article Architecture and Protocols     January 2006

      checkgroups-body    = *( valid-group CRLF )
      valid-group         = newsgroups-line ; see 5.3

6.  Control Messages

   The following sections document the control messages.  "Message" is
   used herein as a synonym for "article" unless context indicates
   otherwise.

   Each <control-command> comprises a <verb>, which indicates the action
   to be taken, and <argument>(s), which supply the details (see F-
   3.2.5).  The following sections contain syntactic definitions for the
   <verb>, <argument>s, and possibly the body, for each type of control
   message.
[The term <control-command> is now used to denote the syntactic object
within the Control header field, to distinguish it from "control
message", which refers to the whole article.]

   The Newsgroups header field 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-name>s 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).

        NOTE: Propagation is controlled by relaying agents, and it may
        be necessary for relaying agents to take special steps to ensure
        that control messages such as newgroup messages for not-yet-
        existent newsgroups are propagated correctly (see 7.3).

   The presence of a Subject header field whose content starts with the
   string "cmsg " followed by a <control-command> was construed under
   [RFC 1036] as a request to perform that control action (even if no
   genuine Control header field was present). Indeed, some
   implementations went further and added the implied Control header
   field before injecting. Likewise, the presence of a <newsgroup-name>
   ending in ".ctl" in the Newsgroups header field caused the Subject
   header field content (not starting with "cmsg" in this case) to be
   interpreted as a <control-command>.

   All these practices, which have already largely fallen into disuse,
   are now declared to be Obsolete, and Subject header fields MUST NOT
   now be interpreted as <control-command>s under any circumstances.

[Possible addtional text:]

                News Article Architecture and Protocols        July 2005

   In order to prevent continuing interpretation of Subject header
   fields in this way by existing agents, posting and injecting agents
   SHOULD detect and decline to post articles in which the Subject
   header field starts with the word "cmsg" and in which there is no
   Control header field.

                News Article Architecture and Protocols     January 2006

   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 refuse to
   honour any particular control message, or to refer it to an
   administrator for approval (either as a class or on a case-by-case
   basis).

6.1.  Digital Signature of Header Fields

   It is most desirable that group control messages (6.2) in particular
   be authenticated by incorporating them within some digital signature
   scheme that encompasses other header fields closely associated with
   them (including at least Approved, Message-ID and Date). At 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, header fields.  That
   extension would also address other Netnews security issues.

6.2.  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.

   Group control messages that attempt to create groups with names that
   are deprecated or reserved according to F-3.1.5 MUST NOT be issued,
   except by prior agreement within some cooperating subnet.  Moreover,
   sites receiving such control messages SHOULD check them for
   conformance before honouring them.

   All of the group control messages MUST have an Approved header field
   (F-3.2.9) which, in those hierarchies where appropriate
   administrative agencies exist (see 1.1), identifies the appropriate
   person or entity as authorized by those agencies.  The authorized
   person or entity SHOULD adhere to any conventions and restrictions on
   the format of <newsgroup-name>s established for those hierarchies
   [USEAGE].

                News Article Architecture and Protocols        July 2005

6.2.1.  The 'newgroup' Control Message

      control-command     =/ Newgroup-command
      Newgroup-command    = "newgroup" Newgroup-arguments
      Newgroup-arguments  = FWS newsgroup-name [ FWS newgroup-flag ]
      newgroup-flag       = "moderated"
                News Article Architecture and Protocols     January 2006

   The "newgroup" control message requests that the specified group be
   created or have its moderation status or <newsgroups-line> changed.
   When the request is honoured, if the <newgroup-flag> "moderated" is
   present then the status of the group SHOULD 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.

6.2.1.1.  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 (5.3) containing the name and
      <newsgroups-line> (5.3) of the group. This part MUST be present
      and SHOULD be used to update any copy of the <newsgroups-line>
      maintained by the serving agent.

   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
      6.2.1.2 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 header fields of the
   control message.  Otherwise, a "Content-Type: multipart/mixed" header
   field will be needed, and each separate part will then need its own
   Content-Type header field.

6.2.1.2.  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 as soon as it has been created or modified. These parts are
   identified by having the Media Type "application/news-transmission",
   possibly with the parameter "usage=inject".  The body of each such

                News Article Architecture and Protocols        July 2005
   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.

   The Newsgroups header field of the proto-article MUST include the
   <newsgroup-name> of the newly created or modified group. It MAY
   include other <newsgroup-name>s. If the proto-article includes a
                News Article Architecture and Protocols     January 2006

   Message-ID header field, 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 field
   "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 field, whether such a field 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.

6.2.1.3.  Example

   A "newgroup" with its charter:

      From: "example.all Administrator" <admin@noc.example>
      Newsgroups: example.admin.info,example.admin.announce
      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:

                News Article Architecture and Protocols        July 2005
      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
                News Article Architecture and Protocols     January 2006

      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--

6.2.2.  The 'rmgroup' Control Message

      control-command     =/ Rmgroup-command
      Rmgroup-command     = "rmgroup" Rmgroup-arguments
      Rmgroup-arguments   = FWS newsgroup-name

   The "rmgroup" control message requests that the specified group be
   removed from the list of valid groups. The Media 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.

6.2.2.1.  Example

      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
      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.

6.2.3.  The 'mvgroup' Control Message

      control-command   =/ Mvgroup-command
      Mvgroup-command   = "mvgroup" Mvgroup-arguments
      Mvgroup-arguments = FWS newsgroup-name FWS newsgroup-name
                             [ FWS newgroup-flag ]

                News Article Architecture and Protocols        July 2005

   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 message body contains an "application/news-groupinfo" part (5.3)
   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> (5.3), is applied to the new
   group.

                News Article Architecture and Protocols     January 2006

   When this message is received, the new group is created (if it does
   not exist already) as for a "newgroup" control message, and SHOULD 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
        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,

                News Article Architecture and Protocols        July 2005
   their Newsgroups header fields MUST contain exactly those newsgroups
   present when they were injected). On the other hand, the Xref header
   field (F-3.2.11) 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.

                News Article Architecture and Protocols     January 2006

        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.

6.2.3.1.  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
      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
      Content-Type: application/news-transmission

      Newsgroups: example.admin.info
      From: "example.all Administrator" <admin@noc.example>
      Subject: Charter for example.newgroup
      Message-ID: <mvgroup-example.newgroup-20020430@noc.example>

                News Article Architecture and Protocols        July 2005
      Distribution: local
      Content-Type: text/plain; charset=us-ascii
      Content-Transfer-Encoding: 7bit

      This group (formerly known as example.oldgroup) is for the
      discussion of examples.

      --nxt--

6.2.4.  The 'checkgroups' Control Message

   The "checkgroups" control message contains a list of all the valid
   groups in a complete hierarchy.

                News Article Architecture and Protocols     January 2006

      control-command     =/ Checkgroup-command
      Checkgroup-command  = "checkgroups" Checkgroup-arguments
      Checkgroup-arguments= [ chkscope ] [ chksernr ]
      chkscope            = 1*( FWS ["!"] newsgroup-name )
      chksernr            = FWS "#" 1*DIGIT

   A "checkgroups" message applies to any (sub-)hierarchy with a prefix
   listed in the <chkscope> argument, provided that the rightmost
   matching <newsgroup-name> in the list is not immediately preceded by
   a "!".  If no <chkscope> argument is given, it applies to all
   hierarchies for which group statements appear in the body of the
   message.

        NOTE: Some existing software does not support the <chkscope>
        argument.  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> argument of the "checkgroups" message.

   The <chksernr> argument 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 field cannot be authenticated.

   Example:

      Control: checkgroups de !de.alt #248

   which includes the whole of the 'de.*' hierarchy, with the exception
   of its 'de.alt.*' sub-hierarchy.

   The body of the message has the Media Type "application/news-
   checkgroups" (5.4).  It asserts that the <valid-group>s it lists are
   the only newsgroups in the specified hierarchies.

                News Article Architecture and Protocols        July 2005

        NOTE: The "checkgroups" message is intended to synchronize the
        list of newsgroups stored by a serving agent, and their
        <newsgroup-description>s, 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.

        NOTE: The possibility of removing a complete hierarchy by means
        of an "invalidation" line beginning with a '!' in the
        checkgroups-body 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>.

                News Article Architecture and Protocols     January 2006

6.3.  Cancel

   The "cancel" message requests that a target article be "canceled",
   i.e. be withdrawn from circulation or access.

      control-command     =/ Cancel-command
      Cancel-command      = "cancel" Cancel-arguments
      Cancel-arguments    = FWS msg-id [FWS]

   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(s), with the same distribution(s), 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 7.3 and 7.4.

        NOTE: It is expected that the security extension envisaged in
        section 6.1 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 (i.e. those issued other
        than by the sender, the moderator, or the injector).

        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 (7.8).

        NOTE: The former requirement [RFC 1036] that the From and/or
        Sender header fields of the "cancel" message should match those
        of the original article has been removed from this standard,

                News Article Architecture and Protocols        July 2005
        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
        header fields and any Approved header field should now relate to
        the entity responsible for issuing the "cancel" message.

6.4.  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.

                News Article Architecture and Protocols     January 2006

        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-command     =/ Ihave-command
      Ihave-command       = "ihave" Ihave-argument
      Ihave-argument      = relayer-name
      control-command     =/ Sendme-command
      Sendme-command      = "sendme" Sendme-argument
      Sendme-argument     = Ihave-argument
      relayer-name        = path-identity  ; see F-3.1.6
      ihave-body          = *( msg-id CRLF )
      sendme-body         = ihave-body

   The body of the message consists of a list of <msg-id>s, one per
   line. [RFC 1036] also permitted the list of <msg-id>s to appear in
   the Ihave- <Ihave-> or Sendme-argument <Sendme-argument> with the syntax
      Ihave-argument      = [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.

   Upon receipt of the sendme message, the receiving agent sends the
   article(s) requested, often (especially when the transport protocol
   is UUCP) in the form of one or more batches, each containing several
   articles. The usual form of a <batch> is defined by the following
   syntax (which is also used in the application/news transmission media
   type (5.1)).

                News Article Architecture and Protocols        July 2005

      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.

                News Article Architecture and Protocols     January 2006

   These control messages are normally sent essentially as point-to-
   point messages, by using <newsgroup-name>s in the Newsgroups header
   field of the form "to."  followed by one (or possibly more)
   <component>s in the form of a <relayer-name> (see section F-3.1.5
   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 neighbours, 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 identifiers. 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.

6.5.  Obsolete control messages.

   The following control messages (as described in Appendix A.3) A) are
   declared obsolete by this standard:

        sendsys
        version
        whogets
        senduuname

7.  Duties of Various Agents

   The following section sets out the duties of various agents involved
   in the creation, relaying and serving of Netnews 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

                News Article Architecture and Protocols        July 2005
   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.

                News Article Architecture and Protocols     January 2006

7.1.  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:

        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.

7.2.  Duties of an Injecting Agent

   An Injecting Agent is responsible for taking a (proto-)article from a
   posting (or other) 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 [USEFOR]. 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). posters.

   In the normal course of events, an article that has already been
   injected into a Netnews network will never pass through another
   injecting agent.  So, if an injecting agent receives an otherwise
   valid article that has already been injected (as evidenced by the
   presence of an Injection-Date header field, an Injection-Info header
   field, or more than one "POSTED" in a Path header field) it MAY

                News Article Architecture and Protocols        July 2005
   choose to reject it, but otherwise SHOULD cause it to be relayed, as
   it stands, by a relaying agent (7.3).

   In exceptional circumstances (e.g. as part of some complex gatewaying
   process, or where a relaying agent considers it essential for
   fulfilling its responsibility towards the rest of the network) an
   already injected article MAY be "reinjected" into the network.  This
   standard does not prescribe any such circumstance; rather this is a
   matter of policy to be determined by the administrators of each
   injecting agent, who have the responsibility to ensure that no harm
   arises. In all other circumstances, unintented reinjection is to be
   avoided (see 7.9).  Nevertheless, in order to preserve the integrity
   of the network in these special cases, this standard does set out the
   correct way to reinject (see special provisions in 7.2.2 Steps 3, 4, 7
                News Article Architecture and Protocols     January 2006

   and 9).

   It is usual for an injecting agent to be closely associated with a
   serving agent, thus giving it access to the list (7.4) showing the
   moderation status of the newsgroups it is likely to handle. In the
   event that it does not have such an associated serving agent, it MUST
   maintain that list itself.

7.2.1.  Proto-articles

   A proto-article 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 header fields MAY be omitted:
   Message-Id, Date, Path (and even From if the particular injecting
   agent can derive that information from other sources).  However, if
   it is intended to offer the proto-article to two or more injecting
   agents in parallel, then it is only the Path header field that MAY be
   omitted.  The header fields that can be omitted MUST NOT contain
   invalid values; they MUST either be correct or not present at all.
[Maybe omit that last sentence.]

        NOTE: An article that is offered for reinjection has, by
        definition, already been injected once, and is not therefore to
        be considered as a proto-article.  Hence a genuine proto-article
        will not contain any Injection-Date header field nor any
        "POSTED" in its Path header field, though that header field MAY
        contain <path-identity>s corresponding to machines traversed
        between the posting agent and the injecting agent proper.

7.2.2.  Procedure to be followed by Injecting Agents

   An injecting agent receives (proto-)articles from posting and
   followup agents. It verifies them, adds header fields where required,
   and then either forwards them to a moderator or injects them by
   passing them to serving or relaying agents.  It MUST NOT forward an
   already injected article to a moderator.

                News Article Architecture and Protocols        July 2005

   An injecting agent processes articles as follows:

   1. It MUST remove any Injection-Info header field already present
      (though it might be useful to copy it to a suitable "X-" header
      field). It SHOULD likewise remove any NNTP-Posting-Host, X-Trace,
      or other non-standard tracing header field.

   2. It SHOULD verify that the article is from a trusted source, and
      MAY reject articles in which header fields contain unverified
      email addresses, that is, addresses which are not known to be
      valid for the trusted source, though it would be perverse to
      reject intentionally unverifiable addresses such as those ending
      in ".invalid" (7.5).

                News Article Architecture and Protocols     January 2006

   3. It SHOULD reject any article whose Date header field (F-3.1.2) is
      more than 24 hours into the future (and MAY use a margin less than
      that 24 hours).  It MUST (except when reinjecting) reject any
      article with an Injection-Date header field already present (and
      SHOULD do likewise with any NNTP-Posting-Date header field). When
      reinjecting it MAY, in the absence of any Injection-Date header
      field, reject any article whose Date header field appears to be
      stale (e.g. more than 72 hours into the past).

   4. It MUST reject any article that does not have the proper mandatory
      header fields for a proto-article (except, when reinjecting, for
      the Injection-Date header field), or which contains any header
      field that does not have legal contents.  It SHOULD reject any
      article which contains any header field deprecated for Netnews
      (e.g. as in [RFC 2298]).  It SHOULD reject any article whose
      Newsgroups header field does not contain at least one <newsgroup-
      name> for an existing group (as listed by its associated serving
      agent) and it MAY reject any <newsgroup-name> which violates one
      of the restrictions in F-3.1.5 or which, although otherwise
      correct, violates a policy restriction established, for some
      (sub-)hierarchy, by an agency with the appropriate authority
      (1.2).  Observe that crossposting to unknown newsgroups is not
      precluded provided at least one of those in the Newsgroups header
      field is listed.

        NOTE: This ability to reject <newsgroup-name>s in breach of
        established policy does not extend to relaying agents, though it
        might be reasonable for posting agents to do it.

   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, Date and From header fields (with appropriate
      contents) MUST be added when not already present.  A User-Agent
      header field MAY be added (or an already present User-Agent header
      field MAY be augmented) so as to identify the software (e.g.
      "INN/1.7.2") used by the injecting agent.

                News Article Architecture and Protocols        July 2005
[That last sentence may need to be reconsidered (in which case see
consequential change in 7.3).]

        NOTE: The Message-ID, Date and From fields will already be
        present during reinjection.

   7. The injecting agent MUST NOT alter the body of the article in any
      way (including any change of Content-Transfer-Encoding). It MAY
      (except when reinjecting) add other header fields not already
      provided by the poster, but SHOULD NOT alter, delete, or reorder
      any existing header field, with the specific exception of the
      "tracing" header field Injection-Info, which is to be removed as
      already mentioned.

                News Article Architecture and Protocols     January 2006

   8. If the Newsgroups header field contains one or more moderated
      groups and the article does NOT contain an Approved header field,
      the injecting agent MUST forward it to a moderator as specified in
      section 7.2.3 below.

   9. Otherwise, a Path header field with a <tail-entry> (F-3.1.6) MUST
      be correctly added if not already present. During reinjection, the
      existing Path header field SHOULD be retained.

   10.It MUST then prepend the <path-identity> of the injecting agent,
      followed by a '!', the <path-keyword> "POSTED" and a further "!"
      (or "!!" if appropriate) to the content of the Path header field;
      this header field SHOULD then be folded if it would otherwise
      result in a header line of excessive length.  The prepended
      <path-identity> MUST be an FQDN mailable address (2.3).
[This may need further changes depending on the resolution of ticket
#1047.]

        NOTE: This could result in more that one "POSTED" <path-keyword>
        in the case of reinjection.

   11.An Injection-Info header field (F-3.2.14) SHOULD be added,
      identifying the trusted source of the article and possibly an
      address for mailing complaints to.  Each injecting agent SHOULD
      use a consistent form of the Injection-Info header field for all
      articles emanating from the same or similar origins.

        NOTE: The step above is the only place in which an Injection-
        Info header field is to be created. It follows that this header
        field MUST NOT be created, replaced, changed or deleted by any
        other agent (except during reinjection, in which case it will
        always relate to the latest injection and is, to that extent,
        regarded as a variant header field).

   12.The injecting agent MUST then add an Injection-Date header field
      (F-3.2.1) if one is not already present, but it MUST NOT alter, or
      delete, an already present Injection-Date header field (and
      likewise SHOULD NOT alter, or delete, an already present NNTP-
      Posting-Date header field).  Finally, it forwards the article to
      one or more relaying or serving agents, and the injection process
      is to be considered complete.

        NOTE: The step above is the only place where an Injection-Date
        header field is to be created It follows that it MUST NOT
        subsequently be replaced, changed or deleted by any other agent,

                News Article Architecture and Protocols        July 2005
        even during reinjection.

7.2.3.  Procedure for Forwarding to a Moderator

   An injecting agent forwards an article to a moderator as follows:

   1. It MUST forward it to the moderator of the first (leftmost)
      moderated group listed in the Newsgroups header field, customarily
      via email, (see 7.8 for how that moderator may forward it to
      further moderators). There are two possibilities for doing this:

                News Article Architecture and Protocols     January 2006

      (a)  The complete article is encapsulated (header fields and all)
           within the email, preferably using the Content-Type
           "application/news-transmission" (5.1) 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 header fields, or of
           changes to those fields during transport through email.

      (b)  The article is sent as an email as it stands, with the
           addition of such extra header fields (e.g. a To header field)
           as are necessary for an email. The existing Message-ID header
           field SHOULD be retained.

      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.

   2. 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)  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".

7.3.  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.

                News Article Architecture and Protocols        July 2005

   An article SHOULD NOT be relayed unless the sending agent has been
   configured to supply and the receiving agent to receive at least one
   of the <newsgroup-name>s in its Newsgroups header field and at least
   one of the <dist-name>s in its Distribution header field, if any.
   Exceptionally, ALL relaying agents are deemed willing to supply or
   accept the <dist-name> "world", and NO relaying agent should supply
   or accept the <dist-name> "local".

   However, if the particular implementation does not relay non-existent
   newsgroups, even when included in the Newsgroups header field and
   implied (e.g. by some "wild card" notation) in the configuration
   tables, then the agent MUST examine all group control messages (6.2)
   in order to ensure that relaying of those messages proceeds normally.

                News Article Architecture and Protocols     January 2006

        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.  A similar possibility for reading agents to filter
        distributions is also suggested in [USEAGE]) for the same
        reason.

   In order to avoid unnecessary relaying, an article SHOULD NOT be
   relayed if the <path-identity> of the receiving agent (or some known
   alias thereof) appears as a <path-identity> (excluding within the
   <tail-entry>) in its Path header field.

   A relaying agent processes articles as follows:

   1. It MUST establish the trusted identity of the source of the
      article and compare it with the leftmost <path-identity> of the
      Path header field's content. If it matches it MUST then prepend
      its own <path-identity> and a '!!' <path-delimiter> to that
      content. If it does not match then it prepends instead two entries
      to that content; firstly the true established <path-identity> of
      the source followed by a '!', the <path-keyword> "MISMATCH" and a
      further '!', and then, to the left of that, its own <path-
      identity> followed by a '!!' <path-delimiter> as usual. This
      prepending of two entries SHOULD NOT be done if the provided and

                News Article Architecture and Protocols        July 2005
      established identities match. This header field SHOULD then be
      folded if it would otherwise result in a header line of excessive
      length.
[This may need further changes depending on the resolution of ticket
#1047.]
[It has been suggested that relaying agents should be permitted to
prepend more than the one or two entries permitted above.]
[something like the following from Diablo might also be useful:
>>> NOTE <<< you should grep through newly created spool directories
every so often looking for .MISMATCH in the spool files to locate
incoming feeds with improperly configured I found that four of my 80+
feeds were misconfigured. ]
                News Article Architecture and Protocols     January 2006

        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).

   2. It MUST examine the Injection-Date header field (or, if that is
      absent, the Date header field) and reject the article as stale
      (F-3.2.1) if that predates the earliest articles of which it
      normally keeps record, or if it is more than 24 hours into the
      future (the margin MAY be less than that 24 hours).

   3. It SHOULD reject any article that does not include all the
      mandatory header fields (section F-3.1).

   4. It MAY reject any article whose header fields 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).

        NOTE: 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 when forming a References header
        field), 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.

   6. It SHOULD reject any article that matches an already received
      cancel message (or an equivalent Supersedes header field) issued
      by its poster or by some other trusted entity.

   7. It MAY reject any article without an Approved header field posted
      to newsgroups known to be moderated (this practice is strongly
      recommended, but the information necessary to do so may not be
      available to all agents).

   8. It MAY delete any Xref header field that is present.

   9. Finally, it passes the articles on to neighbouring relaying and
      serving agents.

                News Article Architecture and Protocols        July 2005

   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
                News Article Architecture and Protocols     January 2006

   entity has explicitly requested that it be informed of such errors.

   Relaying agents MUST NOT alter, delete or rearrange any part of an
   article except for header fields designated as variant (2.4).  In
   particular

     o they MUST NOT create or augment a User-Agent header field in
       order to identify themselves;
     o they MUST NOT rewrite the Newsgroups header field in any way,
       even if some supposedly non-existent newsgroup is included;
     o they MUST NOT refold any header field (i.e. they must pass on the
       folding as received);
     o they MUST NOT alter the Date header field or the Injection-Date
       header field;
     o they MUST NOT delete any unrecognized header field whose field
       name is syntactically correct (whether or not it is registered
       with IANA [RFC 3864]);
     o they MUST NOT change the Content-Transfer-Encoding of the body or
       any body part;
     o they MUST transmit lines of arbitrary length and articles of
       arbitrary size.

7.3.1.  Path Header Field Example

      Path: foo.isp.example!!foo-server!!bar.isp.example!MISMATCH!
         2001:DB8:0:0:8:800:200C:417A!!old.site.example!barbaz!!
         baz.isp.example!POSTED!!dialup123.baz.isp.example!not-for-mail

        NOTE: That article was injected into the news stream by
        baz.isp.example, as indicated by the <path-keyword> "POSTED"
        (complaints may be addressed to abuse@baz.isp.example). The
        injector has chosen to record that it got it from
        dialup123.baz.isp.example. "not-for-mail" 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 old.site.example, 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 IPv6
        address [2001:DB8:0:0:8:800:200C:417A], and claiming (by using
        the '!!'  <path-delimiter>) to have verified that it came from
        old.site.example.

                News Article Architecture and Protocols        July 2005

        [2001:DB8:0:0:8:800:200C:417A] relayed it to "foo-server" which,
        not being convinced that it truly came from
        [2001:DB8:0:0:8:800:200C:417A], inserted the <path-keyword>
        "MISMATCH" and then did a reverse lookup on the actual source
        and concluded it was known as bar.isp.example (that is not to
        say that [2001:DB8:0:0:8:800:200C:417A] was not a correct IPv6
        address for bar.isp.example, but simply that that connection
                News Article Architecture and Protocols     January 2006

        could not be substantiated by foo-server). Observe 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-server and barbaz decided to fold the line,
        on the grounds that it seemed to be getting a little too long.

7.4.  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-locator> (usually in the form of a decimal number - see F-
   3.2.11).

   A serving agent MUST maintain a list of the newsgroups it stores in
   its news database showing the moderation status of each one (see
   6.2.1), and SHOULD include in that list all groups likely to be
   crossposted to from those groups (e.g. all other groups in the same
   hierarchy(ies)).

        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 MAY decline to accept an article if the Path header
   field contains some <path-identity> whose articles the serving 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.
[INN at least does this. It might be argued that it is not necessary to
mention it here.]

   A serving agent processes articles as follows:

                News Article Architecture and Protocols        July 2005

   1. It MUST establish the trusted identity of the source of the
      article and modify the Path header field as for a relaying agent
      (7.3).

   2. It MUST examine the Injection-Date header field (or, if that is
      absent, the Date header field) and reject the article as stale
      (F-3.2.1) if that predates the earliest articles of which it
      normally keeps record, or if it is more than 24 hours into the
                News Article Architecture and Protocols     January 2006

      future (the margin MAY be less than that 24 hours).

   3. It MUST reject any article that does not include all the mandatory
      header fields (section F-3.1), or which contains any header field
      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 articles is usually kept
      and matched against).

   5. It SHOULD reject any article that matches an already received
      cancel message (or an equivalent Supersedes header field) issued
      by its poster or by some other trusted entity.

   6. It MUST reject any article without an Approved header field posted
      to any newsgroup listed as moderated.

   7. It MUST (exept when specially configured to preserve the
      <article-locator>s set by the sending site) remove any Xref header
      field (F-3.2.11) from each article.  It then MAY (and usually
      will) generate a fresh Xref header field.

   8. Finally, it stores the article in its news database.

   Serving agents MUST NOT create new newsgroups simply because an
   unrecognized <newsgroup-name> occurs in a Newsgroups header field
   (see 6.2.1 for the correct method of newsgroup creation).

   Serving agents MUST NOT alter, delete or rearrange any part of an
   article in any other way. The list of particular cases given for
   relaying agents (7.3) applies here also.

7.5.  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 according to [USEFOR] and other applicable policies. In
   particular, they MUST NOT create any Injection-Date or Injection-Info
   header field.

   Contrary to [RFC 2822], which implies that the mailbox(es) in the
   From header field should be that of the poster(s), a poster who does
   not, for whatever reason, wish to use his own mailbox MAY use any
   mailbox ending in the top level domain ".invalid" [RFC 2606].

                News Article Architecture and Protocols        July 2005

   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 or sender.

                News Article Architecture and Protocols     January 2006

7.6.  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. Followup agents MUST
   create valid followups and are subject to special requirements
   involving the Newsgroups, Subject, Distribution and References header
   fields.  Wherever in the following it is stated that, "by default", a
   header field is to be "inherited" from one of those header fields in
   the precursor, it means that its initial (semantic) content is to be
   a copy of the content of that precursor header field.  However,
   posters MAY then override that default before posting if they so
   wish.

        NOTE: The Keywords header field is not inheritable, though some
        older newsreaders treated it as such.

   1. The Newsgroups header field (F-3.1.5) SHOULD by default be
      inherited from the precursor's Followup-To header field if
      present, and otherwise from the precursor's Newsgroups header
      field. However, if the content of that Followup-To header field
      consists of "poster" (and the user does not override it), then the
      followup MUST NOT be posted but, rather, is to be emailed to the
      precursor's poster.

   2. The Subject header field SHOULD by default be inherited from that
      of the precursor.  The case sensitive string "Re: " MAY be
      prepended to the content of its Subject header field, unless it
      already begins with that string.

   3. The Distribution header field (F-3.2.7) SHOULD by default be
      inherited from the precursor's Distribution header field, if any.

   4. The followup MUST (in accordance with the definition of that term)
      have a References header field referring to its precursor,
      constructed in accordance with section 7.6.1 below.

        NOTE: That "MUST" is to be contrasted with the weaker
        recomendation using "SHOULD" applied, in [RFC 2822], to the
        generation of "replies" in email. Moreover, in Netnews, there is
        no expectation of any In-Reply-To header field in a followup.

7.6.1.  Construction of the References header field

   The following procedure is to be used whenever some previous article
   (the "parent") is to be referred to in the References header field
   (F-3.2.2) of a new article, whether in the course of generating a
   followup or for some other reason (e.g. the later parts of a
   multipart posting such as a FAQ, or the later parts of a
   message/partial as suggested in [RFC 2046]).

                News Article Architecture and Protocols        July 2005

   The (semantic) content of the new article's References header field
   consists of the content of the Message-ID header field of the parent
   preceded, if the parent had a References header field, by the content
   of that References header field and a SP (subject to trimming as
                News Article Architecture and Protocols     January 2006

   described below).

   If the resulting References header field would, after unfolding,
   exceed 998 characters in length (including its field name but not the
   final CRLF), it MUST be trimmed (and otherwise it MAY be trimmed).
   Trimming involves removing any number of message identifiers from its
   content, except that the first message identifier and the last two
   MUST NOT be removed.

        NOTE: There is no provision in this standard for an article to
        have more than one parent. The essential property of the
        References header field, guaranteed by the procedure above and
        to be preserved in any future extension, is that no article can
        ever precede one of its own parents.

7.7.  Duties of a Reading Agent

   A reading agent downloads articles from a serving agent, as directed
   by the reader, and displays them to the reader (or processes them in
   some other manner). It SHOULD also have the capability to show the
   raw article exactly as received.

   It MAY present lists of articles available for display, and MAY
   structure those lists so as to show the relationships between the
   articles, as determined by the References, Subject, Date and other
   header fields (see [USEAGE] for some usual methods of doing this).
[This whole section may yet get omitted]

7.8.  Duties of a Moderator

   A Moderator receives news articles, customarily by email, decides
   whether to approve 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 field), or
   else directly as an email already containing all the header fields
   appropriate for a Netnews article (see 7.2.2).  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 approve 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 (6.3) issued by the poster of
      an earlier article, then he is expected to cancel that earlier

                News Article Architecture and Protocols        July 2005
      article (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
      header fields and add Comments and other informational header
                News Article Architecture and Protocols     January 2006

      fields).  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.

      If the article is rejected, then it normally fails for all the
      newsgroups for which it was intended. If it is approved, the
      moderator proceeds with the following steps.

   2. If the Newsgroups header field 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 7.2.2 for the proper method of doing this), or

      (b)  he rotates the <newsgroup-name>s in the Newsgroups header
           field to the left so that the targeted group is the leftmost
           moderated group in that field, and injects it again (thus
           causing the injecting agent to forward it to the correct
           moderator). However, he MUST first ensure that the article
           contains no Approved header field.

        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 field
        (or a similar but differently named header field if method (b)
        is being used) listing all the approvals made so far, or adding
        a separate header field for each individual approval (the header
        field X-Auth is sometimes used for this purpose).  The approval
        may also be confirmed with some form of digital signature (6.1).

   3. If the Newsgroups header field contains no further unapproved
      moderated groups, he adds an Approved header field (F-3.2.9)
      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 approved by
      the moderators of all the moderated groups involved.

   4. The Date header field SHOULD be retained. Any Injection-Date
      header field already present (though there should be none) MUST be
      removed. Exceptionally, if it is known that the injecting agent
      does not yet support the Injection-Date header field and the Date
      header field appears to be stale (F-3.2.1) for reasons understood
      by the moderator (e.g. delays in the moderation process) he MAY
      substitute the current date. The Message-ID header field SHOULD

                News Article Architecture and Protocols        July 2005
      also be retained unless it is obviously non-compliant with this
      standard.

                News Article Architecture and Protocols     January 2006

        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).

   5. Any variant header fields (2.4) MUST be removed, except that a
      Path header field MAY be truncated to only those entries following
      its "POSTED" <path-keyword>.  Any Injection-Info header field (F-
      3.2.14) SHOULD be removed (and if not, the injecting agent will do
      so, as required in 7.2.2).

   6. He then causes the article to be injected, having first 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.

7.9.  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 diktat 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
   unintended reinjection of gated articles. Circular gatewaying

                News Article Architecture and Protocols        July 2005
   (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.

                News Article Architecture and Protocols     January 2006

   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.

   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.

7.9.1.  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 subject to additional constraints due to the possibility of one or
   more corresponding incoming gateways back from that medium to
   Netnews, since this opens the possibility of loops.

   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 and Injection-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

                News Article Architecture and Protocols        July 2005
      human-readable indication that the article should not be gated
      back to Netnews can help locate a human problem.

                News Article Architecture and Protocols     January 2006

   4. Netnews control messages should not be gated to another medium
      unless they would somehow be meaningful in that medium.

   5. Changes MAY be made to the Content-Transfer-Encoding of some or
      all parts of the body, and even to the charsets specified in
      <encoded-word>s or in Content-Type header fields, but such changes
      SHOULD NOT be made unless absolutely necessary.

7.9.2.  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 header fields
   (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 header fields,
   MUST fully conform to the restrictions on those fields, and SHOULD
   exclude any deprecated header fields (e.g. as in [RFC 2298]).  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 field) without removing or renaming
   that header field. Gateways MAY, however, generate their own cancel
   messages, under the general allowance for injecting agents to cancel
   their own messages ([USEAGE]).  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.

   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

                News Article Architecture and Protocols        July 2005
        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
                News Article Architecture and Protocols     January 2006

        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 field 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 F-3.1.3. Such transformations SHOULD be designed so
   that two messages with the same identifier generate the same
   Message-ID header field.

        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 field with the gateway's current date.  If no injection-date
   information is available, the gateway MUST supply an Injection-Date
   header field with whatever date information is available, and
   otherwise 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 and/or Injection-Date header field by
   adding default values rather than discarding this information. Only
   in very exceptional circumstances should Date information be
   discarded, as it plays an important role in preventing reinjection of
   old messages.

                News Article Architecture and Protocols        July 2005

   An incoming gateway MUST add a Sender header field to the news
   article it forms containing the <mailbox> of the administrator of the
   gateway.  Problems with the gateway may be reported to this
                News Article Architecture and Protocols     January 2006

   <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 field,
   it SHOULD be renamed so that its contents can be preserved.

7.9.3.  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 field to all
      messages it generates. The mail-to-news gateway discards any
      incoming messages containing this header field. This is robust
      against mailing list managers that replace the message identifier,
      and against any number of email hops, provided that the other
      message header fields are preserved.

   3. The mail-to-news gateway prepends the host name from which it
      received the email message to the content of the Path header
      field.  The news-to-mail gateway refuses to gateway any message
      that contains the list server name in its Path header field. This
      is robust against any amount of munging of the message header
      fields 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
   which is in turn gated to a different newsgroup.

                News Article Architecture and Protocols        July 2005     January 2006

8.  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.

   See also F-5 for further security considerations related to the
   format of articles.
[And a similar pointer from there to here might be in order.]

8.1.  Leakage

   Articles which are intended to have restricted distribution are
   dependent on the goodwill of every site receiving them.  The
   "Archive: no" header field (F-3.2.12) is available as a signal to
   automated archivers not to file an article, but that cannot be
   guaranteed.

   The Distribution header field 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 (6.4), 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.

8.2.  Attacks

8.2.1.  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.

                News Article Architecture and Protocols     January 2006

   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.

                News Article Architecture and Protocols        July 2005

   Similar effects could be caused by any email header field which could
   cause every reading agent receiving it to take some externally
   visible action.  For example, the Disposition-Notification-To header
   field 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 field 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 7.5).

   A malicious poster may also prevent his article being seen at a
   particular site by preloading that site into the Path header field
   (F-3.1.6) 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 Injection-Info header field) 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 7.2), and to provide assistance to the rest of
   the network by making proper use of the Injection-Info (F-3.2.14)
   header field, 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.

                News Article Architecture and Protocols     January 2006

8.2.2.  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

                News Article Architecture and Protocols        July 2005
   the authenticity of such control messages, either by manual
   inspection (particularly of the Approved header field) or by checking
   any digital signatures that may be provided (see 6.1).  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 (6.3) 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 6.1).  Articles containing Supersedes
   header fields (F-3.2.6) 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 header
   fields and/or check any digital signatures that may be provided (see
   6.1).

   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
   header fields. 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 (as in 5).  Even the Content-Type "text/html"
   could have unexpected side effects on account of embedded objects,
   especially embedded executable code or URIs 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 URIs referring to other
   parts of the same article.
[Frank wants
MIME security considerations are discussed in [RFC2046].  Note that
applying some [RFC2231] extensions for parameters like multi-line
paramters on a boundary parameter as defined in [RFC2046] might be
abused to bypass simple algorithms trying to analyze MIME parts.]

   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.
                News Article Architecture and Protocols        July 2005     January 2006

   reading agent has terminated.

8.3.  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 field 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.

9.  IANA Considerations

   IANA is requested to register the following media types, described
   elsewhere in this standard, for use with the Content-Type header
   field, in the IETF tree in accordance with the procedures set out in
   [RFC 2048].

      application/news-transmission  (5.1)
      application/news-groupinfo     (5.3)
      application/news-checkgroups   (5.4)

   IANA is also requested to change the status of the following media
   type to "OBSOLETE".

      message/news                   (5.2)

        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".

10.  References

10.1.  Normative 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.

                News Article Architecture and Protocols     January 2006

   [RFC 2048] N. Freed, J. Klensin, and J. Postel, "Multipurpose
        Internet Mail Extensions (MIME) Part Four: Registration
        Procedures", RFC 2048, November 1996.

                News Article Architecture and Protocols        July 2005

   [RFC 2119] S. Bradner, "Key words for use in RFCs to Indicate
        Requirement Levels", RFC 2119, March 1997.

   [RFC 2606] D. Eastlake and A. Panitz, "Reserved Top Level DNS Names",
        RFC 2606, June 1999.

   [RFC 2822] P. Resnick, "Internet Message Format", RFC 2822, April
        2001.

   [RFC 3864] G. Klyne, M. Nottingham, and J. Mogul, "Registration
        procedures for message header fields", RFC 3864.

   [USEAGE] draft-ietf-usefor-useage-*.txt.

   [USEFOR] K. Murchison et al, "News Article Format", draft-ietf-
        usefor-usefor-*.txt.

   [USEPRO] This Standard.

10.2.  Informative References

   [ARTICLE] Charles H. Lindsey, "News Article Format and Transmission",
        draft-ietf-usefor-article-format-*.txt.

   [NNTP] Clive D.W. Feather, "Network News Transport Protocol", draft-
        ietf-nntpext-base-*.txt.

   [PGPVERIFY] David Lawrence,
        <ftp://ftp.isc.org/pub/pgpcontrol/README.html>.

   [RFC 1036] M. Horton and R. Adams, "Standard for Interchange of
        USENET Messages", RFC 1036, December 1987.

   [RFC 1918] Y. Rekhter, B. Moskowitz, D. Karrenberg, G. J. de Groot,
        and E. Lear, "Address Allocation for Private Internets", RFC
        1918, February 1996.

   [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 2142] D. Crocker, "Mailbox Names for Common Services, Roles and
        Functions", RFC 2142, May 1997.

   [RFC 2298] R. Fajman, "An Extensible Message Format for Message
        Disposition Notifications", RFC 2298, March 1998.

   [RFC 2616] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter,

                News Article Architecture and Protocols        July 2005
        P. Leach, and T. Berners-Lee, "Hypertext Transfer Protocol --
        HTTP/1.1", RFC 2616, June 1999.

   [RFC 3986] T. Berners-Lee, R. Fielding,

                News Article Architecture and L. Masinter, "Uniform
        Resource Identifier (URI): Generic Syntax", STD 66, Protocols     January
        2005. 2006

   [RFC 850] Mark R. Horton, "Standard for interchange of Usenet
        messages", 2821] John C. Klensin and Dawn P. Mann, "Simple Mail Transfer
        Protocol", RFC 850, June 1983. 2821, April 2001.

   [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.

11.  Acknowledgements

   TBD

12.  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 chairs

        Alexey Melnikov <alexey.melnikov-usefor@isode.com>
        Harald Tveit Alvestrand <harald@alvestrand.no>
]

   Comments on this draft should preferably be sent to the mailing list
   of the Usenet Format Working Group at

        ietf-usefor@imc.org.

Appendix A.1 - A-News Article Format

   The obsolete "A News" article format consisted of exactly five lines
   of header field information, followed by the body. For example:

                News Article Architecture and Protocols        July 2005

      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 identifier 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 archaeological 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
   header fields. 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 field contained the information now found in the Path
   header field, plus possibly the full name now typically found in the
   From header field. The Title header field contained what is now the
   content of the Subject header field. The Posted header field
   contained what is now the content of the Date header field. The
   Article-I.D. header field contained an article ID, analogous to a
   message identifier and used for similar purposes. The Newsgroups and
   Expires header fields were approximately as now. The Received header
   field contained
        <ftp://ftp.zoo.toronto.edu/pub/news.txt.Z>, June 1994.

11.  Acknowledgements

   As this document is the date when result of an eight year effort, the latest relaying agent number of
   people that have contributed to process its content are too numerous to
   mention individually.  Many thanks go out to all past and present
   members of the article first saw it. All dates were in USEFOR Working Group of the above format, with
   all fields fixed width, resembling an Internet date but not quite Engineering Task
   Force (IETF) and the
   same.

   This format is documented for archaeological purposes only.  Articles
   MUST NOT be generated in accompanying mailing list.

12.  Contact Address

Editor

        Charles. H. Lindsey
        5 Clerewood Avenue
        Heald Green
        Cheadle
        Cheshire SK8 3JU
        United Kingdom
        Phone: +44 161 436 6131
        Email: chl@clerew.man.ac.uk

[

Working group chairs

        Alexey Melnikov <alexey.melnikov-usefor@isode.com>
        Harald Tveit Alvestrand <harald@alvestrand.no>
]

   Comments on this format.

                News Article Architecture and Protocols        July 2005 draft should preferably be sent to the mailing list
   of the Usenet Format Working Group at

        ietf-usefor@imc.org.

Appendix A.3 A - Obsolete Control Messages

   This present standard obsoletes certain control messages defined in
   [RFC 1036] (see 6.5), 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.

                News Article Architecture and Protocols     January 2006

      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. "Whogets" was similar, but restricted to a
   named newsgroup.  "Senduuname" resembled "sendsys" but restricted to
   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 field
   specified the actions, in the same way the Control header field does
   now.

   These forms are documented for archaeological purposes only; they
   MUST NO LONGER be used.

Appendix B - Notices

Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights 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; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

                News Article Architecture and Protocols        July 2005

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at ietf-
   ipr@ietf.org.

                News Article Architecture and Protocols     January 2006

Full Copyright Statement

   Copyright (C) The Internet Society (2005). (2006).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Appendix C - Change Log

[This Appendix is to be removed prior to final publication.]

   For version 01

   1    Numerous texts describing protocol features related to
        particular header fields in parts of [ARTICLE] which were
        destined to become part of [USEFOR] have been moved to
        appropriate locations within section 7 of this document. Such
        revised texts will be found in sections
        7.2.2 Steps 4, 6, 7, 10, 11, 12;
        7.2.3 Step 1(b);
        7.3 introductory paragraphs, Steps 1, 4, 8, 9, and some final
        paragraphs;
        7.4 introductory and final paragraphs;
        7.9.1 Step 5.

   2    A section on "Duties of a Reading Agent" (7.8) has been added.

   3    Some demotions MUST -> SHOULD -> MAY, as noted in pseudo-
        comments, have been made or proposed in sections
        7.3
        7.3 Step 4.

   4    Part of the procedure for examining Path header fields by
        relaying agents has been moved to serving agents, as explained
        in pseudo-comments in section 7.4.

   5    Some renumbering of sections and minor textual clarifications.

   For version 02

                News Article Architecture and Protocols        July 2005

   1    2nd para. of a-7 temporarily reinstated in section 6.

   2    Para. in section 6 relating to propagation of control messages
        and local policy removed to [USEAGE].]
                News Article Architecture and Protocols     January 2006

   3    Requirement for some relaying agents to examine control messages
        for non-existent groups
        6
        7.3

   4    Text regarding "aliasing out" brought into line with actual
        practice.
        7.3

   5    More realistic wording regarding the expectations of reading
        agents
        7.7
        7.4

   6    "Precursor" is now defined for all cases in which a References
        header field may be used (even though "followup" is not always
        defined under Alternative-1).
        2.1

   7    Provision is made for a poster to use a mailbox ending in
        ".invalid" in a From header field (formerly in a-5.2).
        7.5

   8    "Inheritable" and "Variant" header fields defined (formerly in
        a-4.2.5).
        2.3

   9    Additional wording regarding function of verb/arguments/body in
        control messages (formerly in a-6.13).
        6

   10   NOTE regarding not altering message indentifiers during
        transport or copying added (formerly in a-5.3).
        7.3

   11   All mention of MIME-style parameters and extension-parameters
        removed.
        3.1
        7.6

   For version 03

   1    The term "inheritable header" is no longer defined. Instead, the
        term "inherited' is used in place of "taken" when defining the
        actions of a followup agent.
        7.6

                News Article Architecture and Protocols        July 2005

   2    Consequent changes to "variant header field", and also mention
        of Injection-Info as sometimes variant.
        2.3

   3    The term "reply address" is no longer defined.

                News Article Architecture and Protocols     January 2006

   4    References now made to sections within USEFOR using "F-..."
        notation.

   5    Cross-references to sections within USEFOR added. Consistent use
        of <...> around all mentions of syntactic objects. All
        occurrences of "Foobar-header" changed to "Foobar header". Many
        other minor textual changes.

   6    <control-message> changed to <control-command>, to avoid
        confusion with "control message", which signifies the complete
        article containing the <control-command>.

   7    <ihave-arguments> has been changed to <ihave-argument> (since
        the earlier practice of multiple arguments is now deprecated).
        Likewise <sendme-argument>.

   For version 04

   1    References divided into Normative and Informational.

   2    All mention of the Mail-Copies-To, Posted-And-Mailed and
        Complaints-To header fields removed.

   3    NOTE added to contrast MUST for References header field with
        SHOULD in RFC 2822.
        7.6

   4    Changes arising from the new syntax of <path-delimiter>s and
        <path-keyword>s.
        7.3

   5    Changes to clarify the construction of the References header
        field.
        7.6.1

   6    Changes due to removal of <comment>s from further header fields.

   7    New section on Identification of news-servers describing
        acceptable forms for <path-identity>s.
        2.3

   8    Definition of "semantic content" of a header field.
        2.1

   9    Systematic replacement of "header" by "header field".

                News Article Architecture and Protocols        July 2005

   10   More stringent rules for checking <newsgroup-name>s in control
        messages for compliance with USEFOR.
        6.2

   For version 05
                News Article Architecture and Protocols     January 2006

   1    Historical Appendices A.1 and A.2 removed, in anticipation of
        republication of Son-of-1036 as an Informational RFC.
        1.3

   2    Definitions of technical terms adopted from USEFOR rather than
        defining them separately.

   3    Discussion of <path-identity> rewritten to reflect recent
        developments (but still awaiting further work in USEFOR).
        2.3

   4    Items now included in Appendix A of USEFOR have been removed
        from section 3, and the "Transitional Arrangements" (which still
        cover the USEFOR changes) have been modified to reflect this.