Transmission Control Protocol (TCP) Specification
draft-ietf-tcpm-rfc793bis-20

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Internet Engineering Task Force                             W. Eddy, Ed.
Internet-Draft                                               MTI Systems
Obsoletes: 793, 879, 2873, 6093, 6429,                  January 21, 2021
           6528, 6691 (if approved)
Updates: 5961, 1122 (if approved)
Intended status: Standards Track
Expires: July 25, 2021

           Transmission Control Protocol (TCP) Specification
                      draft-ietf-tcpm-rfc793bis-20

Abstract

   This document specifies the Transmission Control Protocol (TCP).  TCP
   is an important transport layer protocol in the Internet protocol
   stack, and has continuously evolved over decades of use and growth of
   the Internet.  Over this time, a number of changes have been made to
   TCP as it was specified in RFC 793, though these have only been
   documented in a piecemeal fashion.  This document collects and brings
   those changes together with the protocol specification from RFC 793.
   This document obsoletes RFC 793, as well as RFCs 879, 2873, 6093,
   6429, 6528, and 6691 that updated parts of RFC 793.  It updates RFC
   1122, and should be considered as a replacement for the portions of
   that document dealing with TCP requirements.  It also updates RFC
   5961 by adding a small clarification in reset handling while in the
   SYN-RECEIVED state.  The TCP header control bits from RFC 793 have
   also been updated based on RFC 3168.

   RFC EDITOR NOTE: If approved for publication as an RFC, this should
   be marked additionally as "STD: 7" and replace RFC 793 in that role.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 25, 2021.

Eddy                      Expires July 25, 2021                 [Page 1]
Internet-Draft              TCP Specification               January 2021

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Purpose and Scope . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   5
     2.2.  Key TCP Concepts  . . . . . . . . . . . . . . . . . . . .   5
   3.  Functional Specification  . . . . . . . . . . . . . . . . . .   6
     3.1.  Header Format . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  TCP Terminology Overview  . . . . . . . . . . . . . . . .  12
       3.2.1.  Key Connection State Variables  . . . . . . . . . . .  12
       3.2.2.  State Machine Overview  . . . . . . . . . . . . . . .  14
     3.3.  Sequence Numbers  . . . . . . . . . . . . . . . . . . . .  17
     3.4.  Establishing a connection . . . . . . . . . . . . . . . .  24
     3.5.  Closing a Connection  . . . . . . . . . . . . . . . . . .  31
       3.5.1.  Half-Closed Connections . . . . . . . . . . . . . . .  33
     3.6.  Segmentation  . . . . . . . . . . . . . . . . . . . . . .  34
       3.6.1.  Maximum Segment Size Option . . . . . . . . . . . . .  35
       3.6.2.  Path MTU Discovery  . . . . . . . . . . . . . . . . .  37