Standard for interchange of USENET messages
RFC 850

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RFC 850                                         June 1983

       Standard for Interchange of USENET Messages

                      Mark R. Horton

[ This memo is distributed as an RFC  only  to  make  this
information  easily  accessible to researchers in the ARPA
community.  It does not specify  an  Internet  standard. ] 

1.  Introduction

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

There are five sections to  this  document.   Section  two
section  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.  Article Format

The primary consideration in choosing an article format is
that  it  fit  in with existing tools as well as possible.
Existing tools include both implementations  of  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
ARPANET, and this  format  meets  most  of  the  needs  of
USENET.    Since   the   ARPANET   format  is  extensible,
extensions to meet the  additional  needs  of  USENET  are
easily  made  within the ARPANET standard.  Therefore, the
rule is adopted that all  USENET  news  articles  must  be
formatted as valid ARPANET mail messages, according to the
ARPANET  standard  RFC  822.   This   standard   is   more
restrictive  than the ARPANET standard, placing additional
requirements on each article and forbidding use of certain
ARPANET  features.   However, it should always be possible
to use a tool expecting an ARPANET message  to  process  a
news  article.   In  any  situation  where  this  standard
conflicts with the ARPANET standard,  RFC  822  should  be
considered correct and this standard in error.

                          - 1 -



An example message is included to illustrate the fields.

     Relay-Version: version B 2.10 2/13/83; site cbosgd.UUCP
     Posting-Version: version B 2.10 2/13/83; site eagle.UUCP
     Path: cbosgd!mhuxj!mhuxt!eagle!jerry
     From: jerry@eagle.uucp (Jerry Schwarz)
     Newsgroups: net.general
     Subject: Usenet Etiquette -- Please Read
     Message-ID: <642@eagle.UUCP>
     Date: Friday, 19-Nov-82 16:14:55 EST
     Followup-To: net.news
     Expires: Saturday, 1-Jan-83 00:00:00 EST
     Date-Received: Friday, 19-Nov-82 16:59:30 EST
     Organization: Bell Labs, Murray Hill

     The body of the article 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 articles  in  this  format  to
ease upward conversion.

     From: cbosgd!mhuxj!mhuxt!eagle!jerry (Jerry Schwarz)
     Newsgroups: net.general
     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 article comes here, after a blank line.

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

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

An article consists of several header lines, followed by a
blank  line,  followed  by  the  body of the message.  The
header lines consist of a keyword, a colon, a  blank,  and
some  additional  information.   This  is  a subset of the
ARPANET 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  ARPANET  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 ARPANET
convention of continuation header lines (beginning with  a
blank or tab) is allowed.

                          - 2 -



Certain  headers  are  required,   certain   headers   are
optional.   Any unrecognized headers are allowed, and will
be passed through unchanged.   The  required  headers  are
Relay-Version,  Posting-Version,  From,  Date, Newsgroups,
Subject,  Message-ID,  Path.   The  optional  headers  are
Followup-To,  Date-Received,  Expires,  Reply-To,  Sender,
References, Control, Distribution, Organization.

2.1  Required Headers

2.1.1  Relay-Version  This header line shows  the  version
of  the  program  responsible for the transmission of this
article over the immediate link, that is, the program that