RFC 42 (rfc42) - Page 1 of 3
Message Data Types
Alternative Format: Original Text Document
Network Working Group E.I. Ancona
Request for Comments: 42 M.I.T. Lincoln Laboratory
31 March 1970
Message Data Types
Proposal:
We propose that the first eight bits of a normal message be reserved
for a message data type. Adoption of this convention does not in any
way signify agreement as to the actual data types to be used. It
merely establishes the convention that the first eight bits of every
normal message are not available for user data.
Discussion:
Socket Port
| | | ____________
| V V / \
V / \
|=| /==| |
-------(+)->|Y|-->< | |
|=| \==| |
| PROCESS |
| |
|=| /==| |
-------(-)->|X|<--< | |
|=| \==| |
\ /
\____________/
It is important that conventions regarding the contents of messages
be set up early so that there will not be a large proliferation of
such conventions between every pair of programs running on the
network.
As network usage grows, network languages may develop for specifying
both the syntax and semantics of messages. However, even before such
conventions are developed, a simple way of describing such a
specification is by means of a message type which both sender and
receiver know how to interpret.
It is important that currently running programs still run with this
convention; thus, we propose that two system programs be written
which initially put in and test and remove the type information from
the message. Let us call these two programs X and Y, for lack of
Ancona
