rfc1036.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

    newsgroup is removed from every host on the network, this command
    should be used carefully by a responsible administrator.  The
    rmgroup message should be ignored unless there is an "Approved:"
    line in the same message header.













Horton & Adams                                                 [Page 13]

RFC 1036              Standard for USENET Messages         December 1987


3.5.  Sendsys
                           sendsys (no arguments)

    The sys file, listing all neighbors and the newsgroups to be sent to
    each neighbor, will be mailed to the author of the control message
    ("Reply-To", if present, otherwise "From").  This information is
    considered public information, and it is a requirement of membership
    in USENET that this information be provided on request, either
    automatically in response to this control message, or manually, by
    mailing the requested information to the author of the message.
    This information is used to keep the map of USENET up to date, and
    to determine where netnews is sent.

    The format of the file mailed back to the author should be the same
    as that of the sys file.  This format has one line per neighboring
    host (plus one line for the local host), containing four colon
    separated fields.  The first field has the host name of the
    neighbor, the second field has a newsgroup pattern describing the
    newsgroups sent to the neighbor.  The third and fourth fields are
    not defined by this standard.  The sys file is not the same as the
    UUCP L.sys file.  A sample response is:

      From: cbosgd!mark  (Mark Horton)
      Date: Sun, 27 Mar 83 20:39:37 -0500
      Subject: response to your sendsys request
      To: [e-mail]

      Responding-System: cbosgd.ATT.COM
      cbosgd:osg,cb,btl,bell,world,comp,sci,rec,talk,misc,news,soc,to,
            test
      ucbvax:world,comp,to.ucbvax:L:
      cbosg:world,comp,bell,btl,cb,osg,to.cbosg:F:/usr/spool/outnews
            /cbosg
      cbosgb:osg,to.cbosgb:F:/usr/spool/outnews/cbosgb
      sescent:world,comp,bell,btl,cb,to.sescent:F:/usr/spool/outnews
            /sescent
      npois:world,comp,bell,btl,ug,to.npois:F:/usr/spool/outnews/npois
      mhuxi:world,comp,bell,btl,ug,to.mhuxi:F:/usr/spool/outnews/mhuxi

3.6.  Version

                           version (no arguments)

    The name and version of the software running on the local system is
    to be mailed back to the author of the message ("Reply-to" if
    present, otherwise "From").

3.7.  Checkgroups



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RFC 1036              Standard for USENET Messages         December 1987


    The message body is a list of "official" newsgroups and their
    description, one group per line.  They are compared against the list
    of active newsgroups on the current host.  The names of any obsolete
    or new newsgroups are mailed to the user "usenet" and descriptions
    of the new newsgroups are added to the help file used when posting
    news.

4.  Transmission Methods

    USENET is not a physical network, but rather a logical network
    resting on top of several existing physical networks.  These
    networks include, but are not limited to, UUCP, the Internet, an
    Ethernet, the BLICN network, an NSC Hyperchannel, and a BERKNET.
    What is important is that two neighboring systems on USENET have
    some method to get a new message, in the format listed here, from
    one system to the other, and once on the receiving system, processed
    by the netnews software on that system.  (On UNIX systems, this
    usually means the rnews program being run with the message on the
    standard input. <1>)

    It is not a requirement that USENET hosts have mail systems capable
    of understanding the Internet mail syntax, but it is strongly
    recommended.  Since "From", "Reply-To", and "Sender" lines use the
    Internet syntax, replies will be difficult or impossible without an
    Internet mailer.  A host without an Internet mailer can attempt to
    use the "Path" header line for replies, but this field is not
    guaranteed to be a working path for replies.  In any event, any host
    generating or forwarding news messages must have an Internet address
    that allows them to receive mail from hosts with Internet mailers,
    and they must include their Internet address on their From line.

4.1.  Remote Execution

    Some networks permit direct remote command execution.  On these
    networks, news may be forwarded by spooling the rnews command with
    the message on the standard input.  For example, if the remote
    system is called remote, news would be sent over a UUCP link
    with the command:

                              uux - remote!rnews

    and on a Berknet:

                              net -mremote rnews







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RFC 1036              Standard for USENET Messages         December 1987


    It is important that the message be sent via a reliable mechanism,
    normally involving the possibility of spooling, rather than direct
    real-time remote execution.  This is because, if the remote system
    is down, a direct execution command will fail, and the message will
    never be delivered.  If the message is spooled, it will eventually
    be delivered when both systems are up.

4.2.  Transfer by Mail

    On some systems, direct remote spooled execution is not possible.
    However, most systems support electronic mail, and a news message
    can be sent as mail.  One approach is to send a mail message which
    is identical to the news message: the mail headers are the news
    headers, and the mail body is the news body.  By convention, this
    mail is sent to the user newsmail on the remote machine.

    One problem with this method is that it may not be possible to
    convince the mail system that the "From" line of the message is
    valid, since the mail message was generated by a program on a
    system different from the source of the news message.  Another
    problem is that error messages caused by the mail transmission
    would be sent to the originator of the news message, who has no
    control over news transmission between two cooperating hosts
    and does not know whom to contact.  Transmission error messages
    should be directed to a responsible contact person on the
    sending machine.

    A solution to this problem is to encapsulate the news message into a
    mail message, such that the entire message (headers and body) are
    part of the body of the mail message.  The convention here is that
    such mail is sent to user rnews on the remote system.  A mail
    message body is generated by prepending the letter N to each line of
    the news message, and then attaching whatever mail headers are
    convenient to generate.  The N's are attached to prevent any special
    lines in the news message from interfering with mail transmission,
    and to prevent any extra lines inserted by the mailer (headers,
    blank lines, etc.) from becoming part of the news message.  A
    program on the receiving machine receives mail to rnews, extracting
    the message itself and invoking the rnews program.  An example in
    this format might look like this:











Horton & Adams                                                 [Page 16]

RFC 1036              Standard for USENET Messages         December 1987


                Date: Mon, 3 Jan 83 08:33:47 MST
                From: [e-mail]
                Subject: network news message
                To: [e-mail]

                NPath: cbosgd!mhuxj!harpo!utah-cs!sask!derek
                NFrom: [e-mail] (Derek Andrew)
                NNewsgroups: misc.test
                NSubject: necessary test
                NMessage-ID: <[e-mail]>
                NDate: Mon, 3 Jan 83 00:59:15 MST
                N
                NThis really is a test.  If anyone out there more than 6
                Nhops away would kindly confirm this note I would
                Nappreciate it.  We suspect that our news postings
                Nare not getting out into the world.
                N

    Using mail solves the spooling problem, since mail must always be
    spooled if the destination host is down.  However, it adds more
    overhead to the transmission process (to encapsulate and extract the
    message) and makes it harder for software to give different
    priorities to news and mail.

4.3.  Batching

    Since news messages are usually short, and since a large number of
    messages are often sent between two hosts in a day, it may make
    sense to batch news messages.  Several messages can be combined into
    one large message, using conventions agreed upon in advance by the
    two hosts.  One such batching scheme is described here; its use is
    highly recommended.

    News messages are combined into a script, separated by a header of
    the form:


                   #! rnews 1234

    where 1234 is the length of the message in bytes.  Each such line is
    followed by a message containing the given number of bytes.  (The
    newline at the end of each line of the message is counted as one
    byte, for purposes of this count, even if it is stored as <CARRIAGE
    RETURN><LINE FEED>.)  For example, a batch of message might look
    like this:






Horton & Adams                                                 [Page 17]

RFC 1036              Standard for USENET Messages         December 1987


                #! rnews 239
                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 EST
                Approved: [e-mail]

                Here is an important message about USENET Etiquette.
                #! rnews 234
                From: [e-mail] (Jerry Schwarz)
                Path: cbosgd!mhuxj!mhuxt!eagle!jerry
                Newsgroups: news.announce
                Subject: Notes on Etiquette message
                Message-ID: <[e-mail]>
                Date: Fri, 19 Nov 82 17:24:12 EST
                Approved: [e-mail]

                There was something I forgot to mention in the last
                message.

    Batched news is recognized because the first character in the
    message is #.  The message is then passed to the unbatcher for
    interpretation.

    The second argument (in this example rnews) determines which
    batching scheme is being used.  Cooperating hosts may use whatever
    scheme is appropriate for them.

5.  The News Propagation Algorithm

    This section describes the overall scheme of USENET and the
    algorithm followed by hosts in propagating news to the entire
    logical network.  Since all hosts are affected by incorrectly
    formatted messages and by propagation errors, it is important
    for the method to be standardized.

    USENET is a directed graph.  Each node in the graph is a host
    computer, and each arc in the graph is a transmission path from
    one host to another host.  Each arc is labeled with a newsgroup
    pattern, specifying which newsgroup classes are forwarded along
    that link.  Most arcs are bidirectional, that is, if host A
    sends a class of newsgroups to host B, then host B usually sends
    the same class of newsgroups to host A.  This bidirectionality
    is not, however, required.

    USENET is made up of many subnetworks.  Each subnet has a name, such



Horton & Adams                                                 [Page 18]

RFC 1036              Standard for USENET Messages         December 1987


    as comp or btl.  Each subnet is a connected graph, that is, a path
    exists from every node to every other node in the subnet.  In
    addition, the entire graph is (theoretically) connected.  (In
    practice, some political considerations have caused some hosts to be
    unable to post messages reaching the rest of the network.)

    A message is posted on one machine to a list of newsgroups. That
    machine accepts it locally, then forwards it to all its neighbors
    that are interested in at least one of the newsgroups of the
    message.  (Site A deems host B to be "interested" in a newsgroup if
    the newsgroup matches the pattern on the arc from A to B.  This
    pattern is stored in a file on the A machine.)  The hosts receiving
    the incoming message examine it to make sure they really want the
    message, accept it locally, and then in turn forward the message to
    all their interested neighbors.  This process continues until the
    entire network has seen the message.

    An important part of the algorithm is the prevention of loops.  The
    above process would cause a message to loop along a cycle forever.
    In particular, when host A sends a message to host B, host B will
    send it back to host A, which will send it to host B, and so on.
    One solution to this is the history mechanism.  Each host keeps
    track of all messages it has seen (by their Message-ID) and
    whenever a message comes in that it has already seen, the incoming
    message is discarded immediately.  This solution is sufficient to
    prevent loops, but additional optimizations can be made to avoid
    sending messages to hosts that will simply throw them away.

    One optimization is that a message should never be sent to a machine
    listed in the "Path" line of the header.  When a machine name is
    in the "Path" line, the message is known to have passed through the
    machine.  Another optimization is that, if the message originated
    on host A, then host A has already seen the message.  Thus, if a
    message is posted to newsgroup misc.misc, it will match the pattern
    misc.all (where all is a metasymbol that matches any string), and
    will be forwarded to all hosts that subscribe to misc.all (as
    determined by what their neighbors send them).  These hosts make up
    the misc subnetwork.  A message posted to btl.general will reach all
    hosts receiving btl.all, but will not reach hosts that do not get
    btl.all.  In effect, the messages reaches the btl subnetwork.  A
    messages posted to newsgroups misc.misc,btl.general will reach all
    hosts subscribing to either of the two classes.

Notes

    <1>  UNIX is a registered trademark of AT&T.





Horton & Adams                                                 [Page 19]