RFC 22: Host-host control message formats (original) (raw)

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

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

<2>             <L1> <L2>     DK primary.  Your primary output link
                              to us was L; our primary output link
                              to you is L2.

<3>             <L1> <L2>     OK auxiliary.  Your auxiliary output
                              link is Li, our auxiliary output link
                              is L2.

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

<5>             <Li> <L2>     Not OK auxiliary.  We cannot establish
                              an auxiliary connection.  Your primary
                              output link no was L2.

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RFC 22 Host-Host Control Message Formats October 1969

<6>             <L>           Please stop transmitting over link
                              number L.  This is called the CEASE
                              directive.

<7>             <L>           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>             <L>           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    |  <L1>     |  <L2>   |
           |______|_______|___________|_________|
           |                 |                  |
           |     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 ]

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