TCP ESN: Extended Sequence Numbers for TCP
draft-bagnulo-tcpm-esn-00

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Network Working Group                                         M. Bagnulo
Internet-Draft                                                      UC3M
Intended status: Experimental                                 Y. Nishida
Expires: April 2, 2018                                GE Global Research
                                                      September 29, 2017

               TCP ESN: Extended Sequence Numbers for TCP
                     draft-bagnulo-tcpm-esn-00.txt

Abstract

   This note defines the Extended Sequence Number (ESN) experimental
   modification to TCP to increase TCP's sequence number using the
   TimeStamp (TS) option.  It also modifies the Window Scale (WS) option
   to support larger receiver window enable by the extended sequence
   number space.  At this stage, the purpose of this document is to
   discuss different design choices to generate discussion about the
   approach to follow.

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Bagnulo & Nishida         Expires April 2, 2018                 [Page 1]
Internet-Draft                   TCP ESN                  September 2017

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Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Design rationale  . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Reduced option space consumption in the SYN and graceful
           fallback  . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Deployability . . . . . . . . . . . . . . . . . . . . . .   4
   3.  RTTM With Extended Sequence Number Prefix . . . . . . . . . .   4
   4.  Middleboxes Implications  . . . . . . . . . . . . . . . . . .   7
   5.  SACK for Extended Sequence Number . . . . . . . . . . . . . .   8
   6.  Impacts On Other TCP Extensions . . . . . . . . . . . . . . .   8
     6.1.  PAWS  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.2.  Eifel Detection Algorithm . . . . . . . . . . . . . . . .   9
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   9
     10.2.  Informative References . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Overview

   The proposed Extended Sequence Number (ESN) mechanism re-purposes the
   TS option [RFC7323] to carry a prefix for the sequence number and a
   prefix for the Acknowledgement number, increasing the sequence number
   used in TCP connections.

   As currently defined, the TS option contains two 32-bit fields, TSval
   and TSecr.  The current ESN proposal re-defines TSval to carry a
   prefix for the sequence number and TSecr to carry a prefix for the
   Acknowledgment number.  In this way, the actual sequence number
   corresponding to the first data byte contained in the segment would
   the the concatenation of the value contained in the TSval and the
   value of the Sequence Number field of the TCP header.  The
   Acknowledgment sequence number would be the concatenation of the
   value contained in the TSecr and the value of the Acknowledgment
   Number field of the TCP header.

   The proposed ESN mechanism also modifies the WS option as follows:
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