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This is a modified version of the Internet RFC suitable for machine-translating. Original version is available here: RFC22




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:

<control byte> <parameter byte l> ... <parameter byte n>

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.

Cerf [Page 1]


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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