Internet DRAFT - draft-ietf-tsvwg-source-quench
draft-ietf-tsvwg-source-quench
Transport Area Working Group (tsvwg) F. Gont
Internet-Draft UTN-FRH / SI6 Networks
Updates: 792, 1122, 1812 February 25, 2012
(if approved)
Intended status: Standards Track
Expires: August 28, 2012
Deprecation of ICMP Source Quench messages
draft-ietf-tsvwg-source-quench-06.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.
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This Internet-Draft will expire on August 28, 2012.
Copyright Notice
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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-05 . . . . . . 8
B.2. Changes from draft-ietf-tsvwg-source-quench-04 . . . . . . 8
B.3. Changes from draft-ietf-tsvwg-source-quench-03 . . . . . . 8
B.4. Changes from draft-ietf-tsvwg-source-quench-02 . . . . . . 9
B.5. Changes from draft-ietf-tsvwg-source-quench-01 . . . . . . 9
B.6. Changes from draft-ietf-tsvwg-source-quench-00 . . . . . . 9
B.7. Changes from draft-gont-tsvwg-source-quench-01 . . . . . . 9
B.8. 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, we 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
discussed in great detail in [RFC5927] and [CPNI-TCP]. Silently
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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-05
o Fixes minor writeo in Section 7.
B.2. 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.3. 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.4. Changes from draft-ietf-tsvwg-source-quench-02
o Clarifies the requirements language.
B.5. 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.6. 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.7. 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.8. 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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