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Host-host control message formats :: RFC0022

Network Working Group                                          Vint Cerf
Request for Comments: 22                                            UCLA
                                                        October 17, 1969

                   Host-Host Control Message Formats

   NWG/RFC 11 has been modified at UCLA; and will be republished.  In
   the meantime, it seems important to report a new control message
   format which does not use 7-bit ASCII character mode of transmission.

   All Host-Host control messages consist of sequences of 8-bit bytes of
   the form:


   It is reasonable to transmit more than one control message in any
   given packet, although this is not mandatory.

   Presently, 9 control messages have been defined by UCLA; these are
   given in the table below along with their parameters.  The
   interpretation is given from the point of view of the transmitting
   host. ("L" or "Li" mean Link#, and are binary values.)

   Control byte     Parameter      Interpretation

    <0>                        Please establish primary connection;
                                  our output link # is L

    <1>                   Please establish auxiliary connection
                                  parallel to our primary output link L.
                                  The auxiliary output link is L2.

    <2>                   DK primary.  Your primary output link
                                  to us was L; our primary output link
                                  to you is L2.

    <3>                   OK auxiliary.  Your auxiliary output
                                  link is Li, our auxiliary output link
                                  is L2.

    <4>                        Not OK primary.  We cannot establish a
                                  primary connection.  Your primary
                                  output link number was L.

  • Not OK auxiliary. We cannot establish an auxiliary connection. Your primary output link no was L2. Cerf [Page 1] RFC 22 Host-Host Control Message Formats October 1969 <6> Please stop transmitting over link number L. This is called the CEASE directive. <7> We are CLOSING our output link number L. You may get this message before the last message arrives over this link since control messages are higher priority than regular data messages. <8> UNCEASE: that is, you may resume transmitting over output link number L. Each control message is embedded in the appropriate message structure e.g.: <-------------32 bits ---------------> | HEADER | |____________________________________| | | | | | | mark | l | | | |______|_______|___________|_________| | | | | checksum | Padding | |_________________|__________________| typical control message (please establish auxiliary link #L2 parallel to our primary link #l) The header for all HOST-HOST control messages is given below: 0 3 4 7 8 9 10 14 LINK# 24 31 _______________________________________________________________ | | | | | |////////////////| | FLAGS | TYPE | H | SITE | 00000001 |////////////////| |_______|______|_____|_______|_______________|________________| where FLAGS - 0000 TYPE - 0000 (regular message) H - host #(0-3) at SITE (usually 0 for single HOST sites) SITE - Site # LINK# - 00000001 (HOST-HOST control link) [ This RFC was put into machine readable form for entry ] [ into the online RFC archives by Alison De La Cruz 12/00 ] Cerf [Page 2]