rfc1036.txt

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Network Working Group                                          M. Horton
Request for Comments:  1036                       AT&T Bell Laboratories
Obsoletes: RFC-850                                              R. Adams
                                              Center for Seismic Studies
                                                           December 1987


              Standard for Interchange of USENET Messages



STATUS OF THIS MEMO

    This document defines the standard format for the interchange of
    network News messages among USENET hosts.  It updates and replaces
    RFC-850, reflecting version B2.11 of the News program.  This memo is
    disributed as an RFC to make this information easily accessible to
    the Internet community.  It does not specify an Internet standard.
    Distribution of this memo is unlimited.

1.  Introduction

    This document defines the standard format for the interchange of
    network News messages among USENET hosts.  It describes the format
    for messages themselves and gives partial standards for transmission
    of news.  The news transmission is not entirely in order to give a
    good deal of flexibility to the hosts to choose transmission
    hardware and software, to batch news, and so on.

    There are five sections to this document.  Section two defines the
    format.  Section three defines the valid control messages.  Section
    four specifies some valid transmission methods.  Section five
    describes the overall news propagation algorithm.

2.  Message Format

    The primary consideration in choosing a message format is that it
    fit in with existing tools as well as possible.  Existing tools
    include implementations of both mail and news.  (The notesfiles
    system from the University of Illinois is considered a news
    implementation.)  A standard format for mail messages has existed
    for many years on the Internet, and this format meets most of the
    needs of USENET.  Since the Internet format is extensible,
    extensions to meet the additional needs of USENET are easily made
    within the Internet standard.  Therefore, the rule is adopted that
    all USENET news messages must be formatted as valid Internet mail
    messages, according to the Internet standard RFC-822.  The USENET
    News standard is more restrictive than the Internet standard,



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RFC 1036              Standard for USENET Messages         December 1987


    placing additional requirements on each message and forbidding use
    of certain Internet features.  However, it should always be possible
    to use a tool expecting an Internet message to process a news
    message.  In any situation where this standard conflicts with the
    Internet standard, RFC-822 should be considered correct and this
    standard in error.

    Here is an example USENET message to illustrate the fields.

              From: [e-mail] (Jerry Schwarz)
              Path: cbosgd!mhuxj!mhuxt!eagle!jerry
              Newsgroups: news.announce
              Subject: Usenet Etiquette -- Please Read
              Message-ID: <[e-mail]>
              Date: Fri, 19 Nov 82 16:14:55 GMT
              Followup-To: news.misc
              Expires: Sat, 1 Jan 83 00:00:00 -0500
              Organization: AT&T Bell Laboratories, Murray Hill

              The body of the message comes here, after a blank line.

      Here is an example of a message in the old format (before the
      existence of this standard). It is recommended that
      implementations also accept messages in this format to ease upward
      conversion.

               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

               The body of the message comes here, after a blank line.

      Some news systems transmit news in the A format, which looks like
      this:

                Aeagle.642
                news.misc
                cbosgd!mhuxj!mhuxt!eagle!jerry
                Fri Nov 19 16:14:55 1982
                Usenet Etiquette - Please Read
                The body of the message comes here, with no blank line.

    A standard USENET message consists of several header lines, followed
    by a blank line, followed by the body of the message.  Each header



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RFC 1036              Standard for USENET Messages         December 1987


    line consist of a keyword, a colon, a blank, and some additional
    information.  This is a subset of the Internet standard, simplified
    to allow simpler software to handle it.  The "From" line may
    optionally include a full name, in the format above, or use the
    Internet angle bracket syntax.  To keep the implementations simple,
    other formats (for example, with part of the machine address after
    the close parenthesis) are not allowed.  The Internet convention of
    continuation header lines (beginning with a blank or tab) is
    allowed.

    Certain headers are required, and certain other headers are
    optional.  Any unrecognized headers are allowed, and will be passed
    through unchanged.  The required header lines are "From", "Date",
    "Newsgroups", "Subject", "Message-ID", and "Path".  The optional
    header lines are "Followup-To", "Expires", "Reply-To", "Sender",
    "References", "Control", "Distribution", "Keywords", "Summary",
    "Approved", "Lines", "Xref", and "Organization".  Each of these
    header lines will be described below.

2.1.  Required Header lines

2.1.1.  From

    The "From" line contains the electronic mailing address of the
    person who sent the message, in the Internet syntax.  It may
    optionally also contain the full name of the person, in parentheses,
    after the electronic address.  The electronic address is the same as
    the entity responsible for originating the message, unless the
    "Sender" header is present, in which case the "From" header might
    not be verified.  Note that in all host and domain names, upper and
    lower case are considered the same, thus "[e-mail]",
    "[e-mail]", and "[e-mail]" are all equivalent.
    User names may or may not be case sensitive, for example,
    "[e-mail]" might be different from
    "[e-mail]".  Programs should avoid changing the case of
    electronic addresses when forwarding news or mail.

    RFC-822 specifies that all text in parentheses is to be interpreted
    as a comment.  It is common in Internet mail to place the full name
    of the user in a comment at the end of the "From" line.  This
    standard specifies a more rigid syntax.  The full name is not
    considered a comment, but an optional part of the header line.
    Either the full name is omitted, or it appears in parentheses after
    the electronic address of the person posting the message, or it
    appears before an electronic address which is enclosed in angle
    brackets.  Thus, the three permissible forms are:





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RFC 1036              Standard for USENET Messages         December 1987


              From: [e-mail]
              From: [e-mail] (Mark Horton)
              From: Mark Horton <[e-mail]>

    Full names may contain any printing ASCII characters from space
    through tilde, except that they may not contain "(" (left
    parenthesis), ")" (right parenthesis), "<" (left angle bracket), or
    ">" (right angle bracket).  Additional restrictions may be placed on
    full names by the mail standard, in particular, the characters ","
    (comma), ":" (colon), "@" (at), "!" (bang), "/" (slash), "="
    (equal), and ";" (semicolon) are inadvisable in full names.

2.1.2.  Date

    The "Date" line (formerly "Posted") is the date that the message was
    originally posted to the network.  Its format must be acceptable
    both in RFC-822 and to the getdate(3) routine that is provided with
    the Usenet software.  This date remains unchanged as the message is
    propagated throughout the network.  One format that is acceptable to
    both is:

                      Wdy, DD Mon YY HH:MM:SS TIMEZONE

    Several examples of valid dates appear in the sample message above.
    Note in particular that ctime(3) format:

                          Wdy Mon DD HH:MM:SS YYYY

    is not acceptable because it is not a valid RFC-822 date.  However,
    since older software still generates this format, news
    implementations are encouraged to accept this format and translate
    it into an acceptable format.

    There is no hope of having a complete list of timezones.  Universal
    Time (GMT), the North American timezones (PST, PDT, MST, MDT, CST,
    CDT, EST, EDT) and the +/-hhmm offset specifed in RFC-822 should be
    supported.  It is recommended that times in message headers be
    transmitted in GMT and displayed in the local time zone.

2.1.3.  Newsgroups

    The "Newsgroups" line specifies the newsgroup or newsgroups in which
    the message belongs.  Multiple newsgroups may be specified,
    separated by a comma.  Newsgroups specified must all be the names of
    existing newsgroups, as no new newsgroups will be created by simply
    posting to them.





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RFC 1036              Standard for USENET Messages         December 1987


    Wildcards (e.g., the word "all") are never allowed in a "News-
    groups" line.  For example, a newsgroup comp.all is illegal,
    although a newsgroup rec.sport.football is permitted.

    If a message is received with a "Newsgroups" line listing some valid
    newsgroups and some invalid newsgroups, a host should not remove
    invalid newsgroups from the list.  Instead, the invalid newsgroups
    should be ignored.  For example, suppose host A subscribes to the
    classes btl.all and comp.all, and exchanges news messages with host
    B, which subscribes to comp.all but not btl.all.  Suppose A receives
    a message with Newsgroups: comp.unix,btl.general.

    This message is passed on to B because B receives comp.unix, but B
    does not receive btl.general.  A must leave the "Newsgroups" line
    unchanged.  If it were to remove btl.general, the edited header
    could eventually re-enter the btl.all class, resulting in a message
    that is not shown to users subscribing to btl.general.  Also,
    follow-ups from outside btl.all would not be shown to such users.

2.1.4.  Subject

    The "Subject" line (formerly "Title") tells what the message is
    about.  It should be suggestive enough of the contents of the
    message to enable a reader to make a decision whether to read the
    message based on the subject alone.  If the message is submitted in
    response to another message (e.g., is a follow-up) the default
    subject should begin with the four characters "Re:", and the
    "References" line is required.  For follow-ups, the use of the
    "Summary" line is encouraged.

2.1.5.  Message-ID

    The "Message-ID" line gives the message a unique identifier.  The
    Message-ID may not be reused during the lifetime of any previous
    message with the same Message-ID.  (It is recommended that no
    Message-ID be reused for at least two years.)  Message-ID's have the
    syntax: