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The Data Transfer Protocol (RFC0171)

IP.com Disclosure Number: IPCOM000002549D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2001-Oct-24
Document File: 10 page(s) / 21K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

A. Bhushan: AUTHOR [+10]

Abstract

A common protocol is desirable for data transfer in such diverse applications as remote job entry, file transfer, network mail system, graphics, remote program execution, and communication with block data terminals (such as printers, card, paper tape, and magnetic tape equipment, especially in context of terminal IMPs). Although it would be possible to include some or even all of the above applications in an all-inclusive file transfer protocol, a separation between data transfer and application functions would provide flexibility in implementation, and reduce complexity. Separating the data transfer function would also reduce proliferation of programs and protocols.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 20% of the total text.

Network Working Group                                      Abhay Bhushan

Request for Comments: 171                                            MIT

NIC 6793                                                      Bob Braden

Categories: D.4, D.5, and D.7                                       UCLA

Updates: 114                                               Will Crowther

Obsolete: None                                             Alex McKenzie

                                                                     BBN

                                                            Eric Harslem

                                                            John Heafner

                                                                    Rand

                                                             John Melvin

                                                             Dick Watson

                                                                     SRI

                                                            Bob Sundberg

                                                                 HARVARD

                                                               Jim White

                                                                    UCSB

                                                            23 June 1971

                       THE DATA TRANSFER PROTOCOL

I. INTRODUCTION

   A common protocol is desirable for data transfer in such diverse

   applications as remote job entry, file transfer, network mail system,

   graphics, remote program execution, and communication with block data

   terminals (such as printers, card, paper tape, and magnetic tape

   equipment, especially in context of terminal IMPs).  Although it

   would be possible to include some or even all of the above

   applications in an all-inclusive file transfer protocol, a separation

   between data transfer and application functions would provide

   flexibility in implementation, and reduce complexity.  Separating the

   data transfer function would also reduce proliferation of programs

   and protocols.

   We have therefore defined a low-level data transfer protocol (DTP) to

   be used for transfer of data in file transfer, remote job entry, and

   other applications protocols.  This paper concerns itself solely with

   the data transfer protocol.  A companion paper (RFC 172) describes

   file transfer protocol.

II. DISCUSSION

   The data transfer protocol (DTP) serves three basic functions.  It

   provides for convenient separation of NCP messages into "logical"

   blocks (transactions, units, records, groups, and files), it allows

   for the separation of data and control information, and it includes

   some error control mechanisms.

Bhushan, et al.                                                 [Page 1]

RFC 171                THE DATA TRANSFER PROTOCOL              June 1971

   Three modes of separating messages into transactions [1] are allowed

   by DTP.  The first is an indefinite bit stream which terminates only

   when the connection is closed (i.e., the bit stream represents a

   single transaction for duration of connection).  This mode would be

   useful in data transfer between hosts and terminal IMPs (TIPs).

   The second mode utilizes a "transparent" block convention, similar to

   the ASCII DLE (Data Link Escape).  In "transparent" mode,

   transactions (which may be arbitrarily long) end whenever the

   character sequence DLE ETX is encountered (DLE and ETX are 8-bit

   character codes).  To prevent the possibility of a DLE ETX sequence

   occurring within data stream, any occurrence of DLE is replaced by

   DLE DLE on transmission.  The extra DLE is stripped on reception.  A

   departure from the ASCII convention is that "transparent" block does

   not begin with DLE STX, but with a transaction type byte.  This mode

   will be useful in data transfer between terminal IMPs.

   The third mode utilizes a count mechanism.  Each transaction begins

   with a fixed-length descriptor field containing separate binary

   counts of information bits and filler bits.  If a transaction has no

   filler bits, its filler count is zero.  This mode will be useful in

   most host-to-host data transfer applications.

   DTP allows for...