RFC 31 (rfc31) - Page 2 of 7

Binary Message Forms in Computer

RFC 31                    Binary Message Forms             February 1968


                   MESSAGE FORMS IN COMPUTER NETWORKS

INTRODUCTION


     Network communication between computers is becoming increasingly
   important.  However, the variety of installations working in the area
   probably precludes standardization of the content and form of inter-
   computer messages.  There is some hope, however, that a standard way
   of defining and describing message forms can be developed and used to
   facilitate communication between computers.  Just as ALGOL serves as
   a standard vehicle for describing numerous algorithms, and BNF serves
   as a standard for describing language syntax, a message description
   language would be useful as a standard vehicle for defining message
   formats.
     Considerable progress has been made at the low level of message
   handling protocol and one can expect the ASCII protocols to be used.
   The discussion which follows assumes that the mechanics of exchanging
   messages, check sums, repeat requests, etc., have been worked out.
   The topic of concern is how to describe the content and intent of a
   binary message body when the network header and trailer details have
   been stripped off.
     Most attempts at describing the content of binary messages
   jump immediately into a consideration of the bit codings to be used.
   Long, thin rectangles are drawn to represent the binary bit stream;
   this stream is sliced up into boxes, and tables generally describe
   the bit options for each box.  A better approach would be to provide
   a symbolic method for describing messages.  The symbolism, by
   avoiding immediate references to specific bit details, should help
   one's understanding of the message content and the alternatives
   available in the message body.  When the basic form of the binary
   message body is clear, the coding details of the actual bit fields
   can be shown.