RFC 761 (rfc761) - Page 1 of 84
DoD standard Transmission Control Protocol
Alternative Format: Original Text Document
RFC: 761
IEN: 129
DOD STANDARD
TRANSMISSION CONTROL PROTOCOL
January 1980
prepared for
Defense Advanced Research Projects Agency
Information Processing Techniques Office
1400 Wilson Boulevard
Arlington, Virginia 22209
by
Information Sciences Institute
University of Southern California
4676 Admiralty Way
Marina del Rey, California 90291
January 1980
Transmission Control Protocol
TABLE OF CONTENTS
PREFACE ........................................................ iii
1. INTRODUCTION ..................................................... 1
1.1 Motivation .................................................... 1
1.2 Scope ......................................................... 2
1.3 About This Document ........................................... 2
1.4 Interfaces .................................................... 3
1.5 Operation ..................................................... 3
2. PHILOSOPHY ....................................................... 7
2.1 Elements of the Internetwork System ........................... 7
2.2 Model of Operation ............................................ 7
2.3 The Host Environment .......................................... 8
2.4 Interfaces .................................................... 9
2.5 Relation to Other Protocols ................................... 9
2.6 Reliable Communication ....................................... 10
2.7 Connection Establishment and Clearing ........................ 10
2.8 Data Communication ........................................... 12
2.9 Precedence and Security ...................................... 13
2.10 Robustness Principle ......................................... 13
3. FUNCTIONAL SPECIFICATION ........................................ 15
3.1 Header Format ................................................ 15
3.2 Terminology .................................................. 19
3.3 Sequence Numbers ............................................. 24
3.4 Establishing a connection .................................... 29
3.5 Closing a Connection ......................................... 35
3.6 Precedence and Security ...................................... 38
3.7 Data Communication ........................................... 38
3.8 Interfaces ................................................... 42
3.9 Event Processing ............................................. 52
GLOSSARY ............................................................ 75
REFERENCES .......................................................... 83
[Page i]
January 1980
Transmission Control Protocol
[Page ii]
January 1980
Transmission Control Protocol
PREFACE
This document describes the DoD Standard Transmission Control Protocol
(TCP). There have been eight earlier editions of the ARPA TCP
specification on which this standard is based, and the present text
draws heavily from them. There have been many contributors to this work
both in terms of concepts and in terms of text. This edition
incorporates the addition of security, compartmentation, and precedence
concepts into the TCP specification.
Jon Postel
Editor
[Page iii]
January 1980
RFC:761
IEN:129
Replaces: IENs 124, 112,
81, 55, 44, 40, 27, 21, 5
DOD STANDARD
TRANSMISSION CONTROL PROTOCOL
1. INTRODUCTION
The Transmission Control Protocol (TCP) is intended for use as a highly
reliable host-to-host protocol between hosts in packet-switched computer
communication networks, and especially in interconnected systems of such
networks.
This document describes the functions to be performed by the
Transmission Control Protocol, the program that implements it, and its
interface to programs or users that require its services.
1.1. Motivation
Computer communication systems are playing an increasingly important
role in military, government, and civilian environments. This
document primarily focuses its attention on military computer
communication requirements, especially robustness in the presence of
communication unreliability and availability in the presence of
congestion, but many of these problems are found in the civilian and
government sector as well.
As strategic and tactical computer communication networks are
developed and deployed, it is essential to provide means of
interconnecting them and to provide standard interprocess
communication protocols which can support a broad range of
applications. In anticipation of the need for such standards, the
Deputy Undersecretary of Defense for Research and Engineering has
declared the Transmission Control Protocol (TCP) described herein to
be a basis for DoD-wide inter-process communication protocol
standardization.
TCP is a connection-oriented, end-to-end reliable protocol designed to
fit into a layered hierarchy of protocols which support multi-network
applications. The TCP provides for reliable inter-process
communication between pairs of processes in host computers attached to
distinct but interconnected computer communication networks. Very few
assumptions are made as to the reliability of the communication
protocols below the TCP layer. TCP assumes it can obtain a simple,
potentially unreliable datagram service from the lower level
protocols. In principle, the TCP should be able to operate above a
wide spectrum of communication systems ranging from hard-wired
connections to packet-switched or circuit-switched networks.
