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Versions: (draft-gont-tsvwg-source-quench) 00 01 02 03 04 05 06 RFC 6633

Transport Area Working Group (tsvwg)                             F. Gont
Internet-Draft                                    UTN-FRH / SI6 Networks
Updates: 792, 1122, 1812                               February 22, 2012
(if approved)
Intended status: Standards Track
Expires: August 25, 2012


               Deprecation of ICMP Source Quench messages
                 draft-ietf-tsvwg-source-quench-05.txt

Abstract

   This document formally deprecates the use of ICMP Source Quench
   messages by transport protocols, formally updating RFC 792, RFC 1122,
   and RFC 1812.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on August 25, 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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   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  ICMP Source Quench messages . . . . . . . . . . . . . . . . . . 3
   3.  Updating RFC 1122 . . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Updating RFC 1812 . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Clarification for UDP, SCTP, and DCCP . . . . . . . . . . . . . 5
   6.  General Advice to Transport Protocols . . . . . . . . . . . . . 5
   7.  Recommendation Regarding RFC 1016 . . . . . . . . . . . . . . . 5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     11.1.  Normative References . . . . . . . . . . . . . . . . . . . 7
     11.2.  Informative References . . . . . . . . . . . . . . . . . . 7
   Appendix A.  Survey of support of ICMP Source Quench in some
                popular TCP/IP implementations . . . . . . . . . . . . 8
   Appendix B.  Changes from previous versions of the draft (to
                be removed by the RFC Editor before publishing
                this document as an RFC) . . . . . . . . . . . . . . . 8
     B.1.   Changes from draft-ietf-tsvwg-source-quench-04 . . . . . . 8
     B.2.   Changes from draft-ietf-tsvwg-source-quench-03 . . . . . . 8
     B.3.   Changes from draft-ietf-tsvwg-source-quench-02 . . . . . . 9
     B.4.   Changes from draft-ietf-tsvwg-source-quench-01 . . . . . . 9
     B.5.   Changes from draft-ietf-tsvwg-source-quench-00 . . . . . . 9
     B.6.   Changes from draft-gont-tsvwg-source-quench-01 . . . . . . 9
     B.7.   Changes from draft-gont-tsvwg-source-quench-00 . . . . . . 9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 9























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1.  Introduction

   The ICMP specification [RFC0792] defined the ICMP Source Quench
   message (type 4, code 0), which was meant as a mechanism for
   congestion control.  ICMP Source Quench has been known to be an
   ineffective (and unfair) antidote for congestion, and generation of
   ICMP Source Quench messages by routers has been formally deprecated
   by [RFC1812] since 1995.  However, reaction to ICMP Source Quench
   messages in transport protocols has never been formally deprecated.

   This document formally deprecates reaction to ICMP Source Quench
   messages by transport protocols such as TCP, formally updating
   [RFC0792], [RFC1122], and [RFC1812].  Additionally, it provides
   recommendation against the implementation of [RFC1016].  The
   rationale for these specification updates is:

   o  Processing of ICMP Source Quench messages by routers has been
      deprecated for more than 20 years [RFC1812].

   o  Virtually all popular host implementations have removed support
      for ICMP Source Quench messages since (at least) 2005 [RFC5927].

   o  Widespread deployment of ICMP filtering makes it impossible to
      rely on ICMP Source Quench messages for congestion control.

   o  The IETF has moved away from ICMP Source Quench messages for
      congestion control (note e.g. the development of ECN [RFC3168],
      and the fact that ICMPv6 [RFC4443] does not even specify a Source
      Quench message).

         ICMP Source Quench messages are not normally seen in the
         deployed Internet and were considered rare at least as far back
         as 1994.  [Floyd1994]

   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.  ICMP Source Quench messages

   The ICMP specification [RFC0792] defined the ICMP Source Quench
   message (type 4, code 0), which was meant to provide a mechanism for
   congestion control.  The Host Requirements RFC [RFC1122] stated in
   Section 4.2.3.9 that hosts MUST react to ICMP Source Quench messages
   by slowing transmission on the connection, and further added that the
   RECOMMENDED procedure was to put the corresponding connection in the
   slow-start phase of TCP's congestion control algorithm [RFC5681].



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   [RFC1812] noted that research suggested that ICMP Source Quench was
   an ineffective (and unfair) antidote for congestion, and formally
   deprecated the generation of ICMP Source Quench messages by routers,
   stating that routers SHOULD NOT send ICMP Source Quench messages in
   response to congestion.

   [RFC5927] discussed the use of ICMP Source Quench messages for
   performing "blind throughput-reduction" attacks, and noted that most
   TCP implementations silently ignore ICMP Source Quench messages.

   We note that TCP implements its own congestion control mechanisms
   [RFC5681] [RFC3168], that do not depend on ICMP Source Quench
   messages.

      It is interesting to note that ICMPv6 [RFC4443] does not specify a
      "Source Quench" message.


3.  Updating RFC 1122

   This document hereby updates Section 3.2.2.3 of [RFC1122] as follows:

      A host MUST NOT send ICMP Source Quench messages.

      If a Source Quench message is received, the IP layer MAY silently
      discard it.

   Section 4.2.3.9 of [RFC1122] is updated as follows:

      TCP MUST silently discard any received ICMP Source Quench
      messages.

   The consensus of the TSV WG was that there are no valid reasons for a
   host to generate or react to an ICMP Source Quench message in the
   current Internet.  The recommendation that a sender "MUST NOT" send
   an ICMP Source Quench message is because there is no known valid
   reason for a host to generate this message.  The only known impact of
   a sender ignoring this requirement is that it may necessarily consume
   network and endpoint resources.  Discarding ICMP Source Quench
   messages at the internet-layer (rather than at the transport layer)
   is a performance optimization that is permitted by this update.


4.  Updating RFC 1812

   This document hereby updates Section 4.3.3.3 of [RFC1812] as follows:





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      A router MUST ignore any ICMP Source Quench messages it receives.

   The consensus of the TSV WG was that there are no valid reasons for a
   router to react to ICMP Source Quench messages in the current
   Internet.


5.  Clarification for UDP, SCTP, and DCCP

   UDP did not explicitly specify support for ICMP Source Quench
   messages.  Hereby we clarify that UDP end-points MUST silently
   discard received ICMP Source Quench messages.

   It is understood that SCTP and DCCP did not specify support for
   processing received ICMP Source Quench messages.  Hereby we clarify
   that DCCP and SCTP end-points MUST silently discard received ICMP
   Source Quench messages.


6.  General Advice to Transport Protocols

   If a Source Quench message is received by any other transport-
   protocol instance, it MUST be silently ignored.

   The TSV WG is not aware of any use that requires processing of these
   messages, and therefore expects other transports to follow the
   recommendations in Section 3.  Note that for IETF-specified
   transports, this document formally deprecates reaction to ICMP Source
   Quench messages, and that generation of ICMP Source Quench messages
   has been deprecated for both hosts and routers.  Therefore, future
   applications can not expect to receive these messages.


7.  Recommendation Regarding RFC 1016

   RFC 1016 [RFC1016] described an experimental approach to ICMP Source
   Quench message handling in hosts that was being thought about in
   1987.  The IETF notes that RFC 1016 has never been on the IETF
   standards-track, but for clarity and avoidance of doubt, the note
   that the approach described in RFC 1016 [RFC1016] MUST NOT be
   implemented.


8.  Security Considerations

   ICMP Source Quench messages could be leveraged for performing blind
   throughput-reduction attacks against TCP and similar protocols.  This
   attack vector, along with possible countermeasures, has been



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   discussed in great detail in [RFC5927] and [CPNI-TCP].  Silently
   ignoring ICMP Source Quench messages, as specified in this document,
   eliminates the aforementioned attack vector.

   For current TCP implementations, receipt of an ICMP Source Quench
   message should not result in security issues because, as noted in
   [RFC5927] and [CPNI-TCP], virtually all current versions of popular
   TCP implementations already silently ignore ICMP Source Quench
   messages.  This is also the case for SCTP and DCCP implementations.

   Hosts, security gateways, and firewalls MUST silently discard
   received ICMP Source Quench packets and SHOULD log such drops as a
   security fault with at least minimal details (IP Source Address, IP
   Destination Address, ICMP message type, and date/time the packet was
   seen).

      We note that security devices such as the Snort Network Intrusion
      Detection System (NIDS) has logged ICMP Source Quench messages as
      such for more than ten years.  [Anderson2002].


9.  IANA Considerations

   IANA is requested to mark ICMP type 4 (Source Quench) as "Deprecated"
   in de ICMP Parameters registry [ICMPPARREG] with a reference to this
   document.


10.  Acknowledgements

   The author of this document would like to thank Ran Atkinson, who
   contributed text that was incorporated into this document and also
   provided valuable feedback on earlier versions of this document.

   The author of this document would like to thank (in alphabetical
   order) Fred Baker, David Black, Scott Bradner, James Carlson, Antonio
   De Simone, Wesley Eddy, Gorry Fairhurst, Alfred Hoenes, Mahesh
   Jethanandani, Kathleen Moriarty, Carlos Pignataro, James Polk,
   Anantha Ramaiah, Randall Stewart, Dan Wing, and Andrew Yourtchenko,
   for providing valuable feedback on earlier versions of this document.

   This document has benefited from discussions within the TCPM Working
   Group while working on [RFC5927].


11.  References





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11.1.  Normative References

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, September 1981.

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

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1812]  Baker, F., "Requirements for IP Version 4 Routers",
              RFC 1812, June 1995.

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

   [RFC5681]  Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
              Control", RFC 5681, September 2009.

11.2.  Informative References

   [Anderson2002]
              Anderson, D., Fong, M., and A. Valdes, "Heterogeneous
              Sensor Correlation: A Case Study of Live Traffic
              Analysis", Proceedings of the 3rd Annual IEEE Information
              Assurance Workshop New York, NY, USA, 2002.

   [CPNI-TCP]
              CPNI, "Security Assessment of the Transmission Control
              Protocol (TCP)", 2009, <http://www.cpni.gov.uk/Docs/
              tn-03-09-security-assessment-TCP.pdf>.

   [Floyd1994]
              Floyd, S., "TCP and Explicit Congestion Notification", ACM
              CCR Volume 24, Issue 5, 1994.

   [FreeBSD]  The FreeBSD Project, "http://www.freebsd.org".

   [ICMPPARREG]
              Internet Control Message Protocol (ICMP) Parameters,
              "http://www.iana.org/assignments/icmp-parameters".

   [Linux]    The Linux Project, "http://www.kernel.org".

   [NetBSD]   The NetBSD Project, "http://www.netbsd.org".

   [OpenBSD]  The OpenBSD Project, "http://www.openbsd.org".



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   [OpenSolaris]
              OpenSolaris, "http://www.opensolaris.org".

   [RFC1016]  Prue, W. and J. Postel, "Something a host could do with
              source quench: The Source Quench Introduced Delay
              (SQuID)", RFC 1016, July 1987.

   [RFC3168]  Ramakrishnan, K., Floyd, S., and D. Black, "The Addition
              of Explicit Congestion Notification (ECN) to IP",
              RFC 3168, September 2001.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, "Internet Control
              Message Protocol (ICMPv6) for the Internet Protocol
              Version 6 (IPv6) Specification", RFC 4443, March 2006.

   [RFC5927]  Gont, F., "ICMP Attacks against TCP", RFC 5927, July 2010.


Appendix A.  Survey of support of ICMP Source Quench in some popular
             TCP/IP implementations

   A large number of implementations completely ignore ICMP Source
   Quench messages meant for TCP connections.  This behavior has been
   implemented in, at least, Linux [Linux] since 2004, and in FreeBSD
   [FreeBSD], NetBSD [NetBSD], OpenBSD [OpenBSD], and Solaris 10 since
   2005.  Additionally, OpenSolaris [OpenSolaris] has always shipped
   with support for ICMP Source Quench messages disabled.


Appendix B.  Changes from previous versions of the draft (to be removed
             by the RFC Editor before publishing this document as an
             RFC)

B.1.  Changes from draft-ietf-tsvwg-source-quench-04

   o  Removes request to move RFC 1016 to "Historic" status.

   o  Updates the Security Considerations section.

B.2.  Changes from draft-ietf-tsvwg-source-quench-03

   o  Added 'Obsoletes' metadata, and moved the reference to [RFC1016]
      from the 'Normative References' to the 'Informative References'.








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B.3.  Changes from draft-ietf-tsvwg-source-quench-02

   o  Clarifies the requirements language.

B.4.  Changes from draft-ietf-tsvwg-source-quench-01

   o  Changes deprecation of ICMP SQ from "SHOULD NOT" to "MUST NOT" in
      response of feedback from Scott Bradner and the TSV WG.

B.5.  Changes from draft-ietf-tsvwg-source-quench-00

   o  Discusses the motivation for deprecating ICMP Source Quench
      messages (as suggested by Anantha Ramaiah).

   o  Incorporates IANA considerations such that ICMP Source Quench
      messages are deprecated in the corresponding registry.

B.6.  Changes from draft-gont-tsvwg-source-quench-01

   o  Addresses nits and editorial changes suggested by Gorry Fairhurst.

   o  Added the status of Solaris and OpenSolaris to Appendix A.

   o  Document resubmitted as draft-ietf.

B.7.  Changes from draft-gont-tsvwg-source-quench-00

   o  This revision reflects the recent discussion about ICMP Source
      Quench messages on the tsvwg mailing-list.  A detailed list of the
      changes is available at:
      http://www.ietf.org/mail-archive/web/tsvwg/current/msg10407.html


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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