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Versions: 00

TCP Maintenance and Minor Extensions                             F. Gont
(tcpm)                                            UTN-FRH / SI6 Networks
Internet-Draft                                            March 29, 2012
Updates: 793 (if approved)
Intended status: Standards Track
Expires: September 30, 2012


          Processing of TCP segments with Mirrored End-points
             draft-gont-tcpm-tcp-mirrored-endpoints-00.txt

Abstract

   This document describes a problem found in some popular
   implementations regarding the processing of TCP segments in which the
   local endpoint is equal to the remote endpoint.  Additionally, it
   formally updates RFC 793 clarifying how this scenario should be
   handled.

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 http://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 September 30, 2012.

Copyright Notice

   Copyright (c) 2012 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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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of



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


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Updating RFC 793  . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 4
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 4




































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1.  Introduction

   Some systems have been found to be unable to process TCP segments in
   which the source endpoint {Source Address, Source Port} is the same
   than the destination end-point {Destination Address, Destination
   Port}.  Such TCP segments have been reported to cause malfunction of
   a number of implementations [CERT1996], and have been exploited in
   the past to perform Denial of Service (DoS) attacks [Meltman1997].
   While these packets are very very unlikely to exist in legitimate
   scenarios, TCP should nevertheless be able to process them without
   the need of any "extra" code.

   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.  Updating RFC 793

   TCP MUST be able to gracefully handle the case where the source end-
   point (IP Source Address, TCP Source Port) is the same as the
   destination end-point (IP Destination Address, TCP Destination Port).

      A SYN segment in which the source end-point {Source Address,
      Source Port} is the same as the destination end-point {Destination
      Address, Destination Port} will result in a "simultaneous open"
      scenario, such as the one described in page 32 of RFC 793
      [RFC0793].  Therefore, those TCP implementations that correctly
      handle simultaneous opens should already be prepared to handle
      these unusual TCP segments.


3.  IANA Considerations

   This document has no IANA actions.  The RFC Editor is requested to
   remove this section before publishing this document as an RFC.


4.  Security Considerations

   This document describes a problem found in some popular
   implementations regarding the processing of TCP instances in which
   the local and the remote TCP endpoints are the equal.  It formally
   updates RFC 793, clarifying how such packets should be handled, thus
   helping prevent unexpected behaviors in host implementations.






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5.  Acknowledgements

   The author would like to thank David Borman for a fruitful discussion
   about this topic at IETF 73 (Minneapolis).

   This document is based on the technical report "Security Assessment
   of the Transmission Control Protocol (TCP)" [CPNI-TCP] written by
   Fernando Gont on behalf of the UK CPNI.

   Fernando Gont would like to thank the UK CPNI for their continued
   support.


6.  References

6.1.  Normative References

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, September 1981.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

6.2.  Informative References

   [CERT1996]
              CERT, "CERT Advisory CA-1996-21: TCP SYN Flooding and IP
              Spoofing Attacks", 1996,
              <http://www.cert.org/advisories/CA-1996-21.html>.

   [CPNI-TCP]
              Gont, F., "CPNI Technical Note 3/2009: Security Assessment
              of the Transmission Control Protocol (TCP)", 2009, <http:/
              /www.gont.com.ar/papers/
              tn-03-09-security-assessment-TCP.pdf>.

   [Meltman1997]
              Meltman, "new TCP/IP bug in win95. Post to the bugtraq
              mailing-list", 1996,
              <http://insecure.org/sploits/land.ip.DOS.html>.











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Author's Address

   Fernando Gont
   UTN-FRH / SI6 Networks
   Evaristo Carriego 2644
   Haedo, Provincia de Buenos Aires  1706
   Argentina

   Phone: +54 11 4650 8472
   Email: fgont@si6networks.com
   URI:   http://www.si6networks.com








































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