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Gont 3 (tsvwg) UTN/FRH 4 Internet-Draft September 24, 2010 5 Updates: 792, 1122 6 (if approved) 7 Intended status: Standards Track 8 Expires: March 28, 2011 10 Deprecation of ICMP Source Quench messages 11 draft-gont-tsvwg-source-quench-00.txt 13 Abstract 15 This document formally deprecates the use of ICMP Source Quench 16 messages by transport protocols. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on March 28, 2011. 35 Copyright Notice 37 Copyright (c) 2010 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 2. ICMP Source Quench messages . . . . . . . . . . . . . . . . . . 3 54 3. Updating RFC 792 and RFC 1122 . . . . . . . . . . . . . . . . . 3 55 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 56 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 57 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 58 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 7.1. Normative References . . . . . . . . . . . . . . . . . . . 4 60 7.2. Informative References . . . . . . . . . . . . . . . . . . 5 61 Appendix A. Survey of support of ICMP Source Quench in some 62 popular TCP/IP implementations . . . . . . . . . . . . 5 63 Appendix B. Changes from previous versions of the draft (to 64 be removed by the RFC Editor before publishing 65 this document as an RFC) . . . . . . . . . . . . . . . 5 66 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5 68 1. Introduction 70 The ICMP specification [RFC0792] defines the ICMPv4 Source Quench 71 message (type 4, code 0), which is meant as a mechanism for 72 congestion control. ICMP Source Quench is known to be an ineffective 73 (and unfair) antidote for congestion, and generation of ICMP Source 74 Quench messages by routers has been deprecated by [RFC1812] for a 75 long time. However, reaction to ICMP Source Quench messages in 76 transport protocols has never been formally deprecated. 78 This document formally deprecates reaction to ICMP Source Quench 79 messages by transport protocols such as TCP. 81 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 82 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 83 document are to be interpreted as described in RFC 2119 [RFC2119]. 85 2. ICMP Source Quench messages 87 The ICMP specification [RFC0792] defines the ICMP Source Quench 88 message (type 4, code 0), which is meant to provide a mechanism for 89 congestion control. The Host Requirements RFC [RFC1122] states in 90 Section 4.2.3.9 that hosts MUST react to ICMP Source Quench messages 91 by slowing transmission on the connection, and further adds that the 92 RECOMMENDED procedure is to put the corresponding connection in the 93 slow-start phase of TCP's congestion control algorithm [RFC5681]. 95 [RFC1812] notes that research suggests that ICMP Source Quench is an 96 ineffective (and unfair) antidote for congestion, and formally 97 deprecates the generation of ICMP Source Quench messages by routers, 98 stating that routers SHOULD NOT send ICMP Source Quench messages in 99 response to congestion. 101 [RFC5927] discusses the use of ICMP Source Quench messages for 102 performing "blind throughput-reduction" attacks, and notes that most 103 TCP implementations silently ignore ICMP Source Quench messages. 105 We note that TCP implements its own congestion control mechanisms 106 [RFC5681] [RFC3168], that do not depend on ICMP Source Quench 107 messages. 109 3. Updating RFC 792 and RFC 1122 111 If an ICMP Source Quench message is received by a transport-protocol 112 instance (e.g., a TCP connection), it SHOULD be silently ignored. 114 4. Security Considerations 116 ICMP Source Quench messages can be leveraged for performing blind 117 throughput-reduction attacks against TCP and similar protocols. This 118 attack vector, along with possible countermeasures, have been 119 discussed in great detail in [RFC5927] and [CPNI-TCP]. 121 Silently ignoring ICMP Source Quench messages, as specified in this 122 document, eliminates the aforementioned attack vector. 124 5. IANA Considerations 126 This document has no actions for IANA. The RFC-Editor can remove 127 this section before publication of this document as an RFC. 129 6. Acknowledgements 131 This document has benefited from discussions within the TCPM Working 132 Group while working on [RFC5927]. 134 7. References 136 7.1. Normative References 138 [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, 139 RFC 792, September 1981. 141 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, 142 RFC 793, September 1981. 144 [RFC1122] Braden, R., "Requirements for Internet Hosts - 145 Communication Layers", STD 3, RFC 1122, October 1989. 147 [RFC1812] Baker, F., "Requirements for IP Version 4 Routers", 148 RFC 1812, June 1995. 150 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 151 Requirement Levels", BCP 14, RFC 2119, March 1997. 153 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 154 of Explicit Congestion Notification (ECN) to IP", 155 RFC 3168, September 2001. 157 [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion 158 Control", RFC 5681, September 2009. 160 7.2. Informative References 162 [CPNI-TCP] 163 CPNI, "Security Assessment of the Transmission Control 164 Protocol (TCP)", http://www.cpni.gov.uk/Docs/ 165 tn-03-09-security-assessment-TCP.pdf, 2009. 167 [FreeBSD] The FreeBSD Project, "http://www.freebsd.org". 169 [Linux] The Linux Project, "http://www.kernel.org". 171 [NetBSD] The NetBSD Project, "http://www.netbsd.org". 173 [OpenBSD] The OpenBSD Project, "http://www.openbsd.org". 175 [RFC5927] Gont, F., "ICMP Attacks against TCP", RFC 5927, July 2010. 177 Appendix A. Survey of support of ICMP Source Quench in some popular 178 TCP/IP implementations 180 A large number of implementations completely ignore ICMP Source 181 Quench messages meant for TCP connections. This behavior has been 182 implemented in, at least, Linux [Linux] since 2004, and in FreeBSD 183 [FreeBSD], NetBSD [NetBSD], and OpenBSD [OpenBSD] since 2005. 185 Appendix B. Changes from previous versions of the draft (to be removed 186 by the RFC Editor before publishing this document as an 187 RFC) 189 Author's Address 191 Fernando Gont 192 Universidad Tecnologica Nacional / Facultad Regional Haedo 193 Evaristo Carriego 2644 194 Haedo, Provincia de Buenos Aires 1706 195 Argentina 197 Phone: +54 11 4650 8472 198 Email: fernando@gont.com.ar 199 URI: http://www.gont.com.ar