MSDTP-Message Services Data Transmission Protocol
RFC 713

Document Type RFC - Unknown (April 1976; No errata)
Last updated 2013-03-02
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Request for Comments: 713                           Jack Haverty  (JFH@MIT-DMS)
NIC #34739                                                             Apr 1976

I. ABSTRACT

A mechanism is defined for use by message servers in
transferring data between hosts.  The mechanism, called the
MSDTP, is defined in terms of a model of the process as a
translation between two sets of items, the abstract entities
such as 'strings' and 'integers', and the formats used to
represent such data as a byte stream.

A proposed organization of a general data transfer
mechanism is described, and the manner in which the MSDTP
would be used in that environment is presented.

                                -1-


II. REFERENCES

Black, Edward H., "The DMS Message Composer", MIT Project
MAC, Programming Technology Division Document
SYS.16.02.

Burchfiel, Jerry D., Leavitt, Elsie M., Shapiro, Sonya and
Strollo, Theodore R., compilers, "Tenex Users' Guide",
Bolt Beranek and Newman, Cambridge, Mass., May 1971,
revised January 1975, Descriptive sections on the TENEX
subsystems: MAlLER, p. 116-11; MAlLSTAT, p. 118-119;
READMAIL, p. 137; and SNDMSG, p. 165-170.

Haverty, Jack, "Communications System Overview", MIT Project
MAC, Programming Technology Division Document
SYS.16.00.

Haverty, Jack, "Communications System Daemon Manual", MIT
Project MAC, Programming Technology Division Document
SYS.16.01.

ISI Information Automation Project, "Military Message
Processing System Design," Internal Project
Documentation (Out of Print), Jan. 1975

Message Services Committee, "Interim Report", Jan. 28, 1975

Mooers, Charlotte D., "Mailsys Message System: Manual For
Users", Bolt Beranek and Newman, Cambridge, Mass., June
1975 (draft).

Myer, Theodore H., "Notes On The BBN Mail System", Bolt
Beranek and Newman, November 8, 1974.

Myer, Theodore H., and Henderson, D. Austin, "Message
Transmission Protocol", Network Working Group RFC 680,
NIC 32116, April 30, 1975.

Postel, Jon, "The PCPB8 Format", NSW Proposal, June 5, 1975

Tugender, R., and D. R. Oestreicher, "Basic Functional
Capabilities for a Military Message Processing
Service," ISI?RR-74-23., May 1975

Vezza, Al, "Message Services Committee Minority Report",
Jan. 1975

                                   -2-


III. OVERVIEW

This document describes a mechanism developed for use
by message servers communicating over an eight-bit
byte-oriented network connection to move data structures and
associated data-typing information.  It is presented here in
the hope that it may be of use to other projects which need
to transfer data structures between dissimilar hosts.

A set of abstract entities called PRIMITIVE ITEMS is
enumerated.  These are intended to include traditional data
types of general utility, such as integers, strings, and
arrays.

A mechanism is defined for augmenting the set of
abstract data entities handled, to allow the introduction of
application-specific data, whose format and semantics are
understood by the application programs involved, but which
can be transmitted using common coding facilities.  An
example might be a data structure called a 'file
specification', or a 'date'.  Abstract data entities defined
using this mechanism will be termed SEMANTIC ITEMS, since
they are typically used to carry data having semantic
content in the application involved.

Semantic and primitive items are collectively referred
to simply as ITEMS.

The protocol next involves the definition of the format
of the byte stream used to convey items from machine to
machine.  These encodings are described in terms of OBJECTS,
which are the physical byte streams transmitted.

To complete the protocol, the rules for translating
between objects and items are presented as each object is
defined.

An item is transmitted by being translated into an
object which is transmitted over the connection as a stream
of bytes to the receiver, and reconstructed there as an
item.  The protocol mechanism may thus be viewed as a simple
translator.  It enumerates a set of abstract entities, the
items, which are known to programmers, a set of entities in
byte-stream format, the objects, and the translation rules
for conversion between the sets.  A site implementing the
MSDTP would typically provide a facility to convert between
objects and the local representation of the various items
handled.  Applications using the MSDTP define their
interactions using items, without regard to the actual
formats in which such items are represented at various
machines.  This permits programs to handle higher-level
concepts such as a character string, without concern for its
numerous representational formats.  Such detail is handled
by the MSDTP.

                                -3-


Finally, a discussion of a general data transfer
mechanism for communication between programs is presented,
and the manner in which the particular byte-oriented
protocol defined herein would be used in that environment is
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