RFC:  793
Replaces: RFC 761
IENs:  129, 124, 112, 81,
55, 44, 40, 27, 21, 5

                     TRANSMISSION CONTROL PROTOCOL

                         DARPA INTERNET PROGRAM
                         PROTOCOL SPECIFICATION



                            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 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 focuses its attention primarily 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.

(—ª)

                               REFERENCES

[1]  Cerf, V., and R. Kahn, "A Protocol for Packet Network
     Intercommunication", IEEE Transactions on Communications,
     Vol. COM-22, No. 5, pp 637-648, May 1974.

[2]  Postel, J. (ed.), "Internet Protocol - DARPA Internet Program
     Protocol Specification", RFC 791, USC/Information Sciences
     Institute, September 1981.