WSCALE options in established TCP connections
draft-harris-estab-wscale-00

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Last updated 2016-10-31
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TCP Maintenance & Minor Extensions (tcpm)             J. Harris, Ed.
Internet-Draft                                                      None
Updates: 1323 (if approved)                             October 31, 2016
Intended status: Experimental
Expires: May 4, 2017

             WSCALE options in established TCP connections
                      draft-harris-estab-wscale-00

Abstract

   The TCP Window Scale option modifies the interpretation of packets in
   a flow but is transmitted only at the start of the connection.  As
   such there is a problem for observability and fault-finding, since a
   packet capture by a third party may miss the start of a relevant
   connection.  This document describes the use of TCP options to
   provide the scale values during a connection.

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
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   This Internet-Draft will expire on May 4, 2017.

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   Copyright (c) 2016 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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   include Simplified BSD License text as described in Section 4.e of

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Internet-DraftWSCALE options in established TCP connections October 2016

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  TCP WINDOW SCALE OPTION . . . . . . . . . . . . . . . . . . .   2
     2.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.2.  Sender  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.3.  Receiver  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   The TCP WSCALE option [RFC1323] provides a means for scaling the
   effective value of window size value in the TCP header.  This is
   needed for high bandwidth-delay product connections for adequate
   performance as large window sizes must be used.  Use of the facility
   is negotiated by the presence in both SYN-bearing packets at the
   start of the connection of WSCALE options, and is valid with the
   shift values presented there for the remainder of the connection.
   When debugging network problems it is common to take a packet capture
   and heuristically interpret it.  If a TCP connection is captured
   without the initiating SYN packets the window scale information will
   not be available.  The TCP extension usage defined here makes it
   available for such debugging purposes.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  TCP WINDOW SCALE OPTION

2.1.  Format

   The wire format of the option is as defined in [RFC1323].

2.2.  Sender

   A TCP endpoint which has both sent and received WSCALE options in
   SYN-bearing packet MAY send a WSCALE option in a subsequent non-SYN-

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