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Gont 3 Internet-Draft UTN/FRH 4 Updates: 792, 1122, 1812 September 8, 2011 5 (if approved) 6 Intended status: Standards Track 7 Expires: March 11, 2012 9 Deprecation of ICMP Source Quench messages 10 draft-ietf-tsvwg-source-quench-02.txt 12 Abstract 14 This document formally deprecates the use of ICMP Source Quench 15 messages by transport protocols, formally updating RFC 792, RFC 1122, 16 and RFC 1812. Additionally, it requests that the status of RFC 1016 17 be changed to "Historic". 19 Status of this Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on March 11, 2012. 36 Copyright Notice 38 Copyright (c) 2011 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 2. ICMP Source Quench messages . . . . . . . . . . . . . . . . . . 3 55 3. Updating RFC 1122 . . . . . . . . . . . . . . . . . . . . . . . 4 56 4. Updating RFC 1812 . . . . . . . . . . . . . . . . . . . . . . . 4 57 5. Clarification for SCTP and DCCP . . . . . . . . . . . . . . . . 5 58 6. General Advice to Transport Protocols . . . . . . . . . . . . . 5 59 7. Changing the status of RFC 1016 to Historic . . . . . . . . . . 5 60 8. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 61 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 62 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 63 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 64 11.1. Normative References . . . . . . . . . . . . . . . . . . . 6 65 11.2. Informative References . . . . . . . . . . . . . . . . . . 7 66 Appendix A. Survey of support of ICMP Source Quench in some 67 popular TCP/IP implementations . . . . . . . . . . . . 7 68 Appendix B. Changes from previous versions of the draft (to 69 be removed by the RFC Editor before publishing 70 this document as an RFC) . . . . . . . . . . . . . . . 7 71 B.1. Changes from draft-ietf-tsvwg-source-quench-01 . . . . . . 8 72 B.2. Changes from draft-ietf-tsvwg-source-quench-00 . . . . . . 8 73 B.3. Changes from draft-gont-tsvwg-source-quench-01 . . . . . . 8 74 B.4. Changes from draft-gont-tsvwg-source-quench-00 . . . . . . 8 75 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 77 1. Introduction 79 The ICMP specification [RFC0792] defined the ICMP Source Quench 80 message (type 4, code 0), which was meant as a mechanism for 81 congestion control. ICMP Source Quench has been known to be an 82 ineffective (and unfair) antidote for congestion, and generation of 83 ICMP Source Quench messages by routers has been formally deprecated 84 by [RFC1812] since 1995. However, reaction to ICMP Source Quench 85 messages in transport protocols has never been formally deprecated. 87 This document formally deprecates reaction to ICMP Source Quench 88 messages by transport protocols such as TCP, formally updating 89 [RFC0792], [RFC1122], and [RFC1812]. Additionally, it requests that 90 the status of [RFC1016] be changed to "Historic". The rationale for 91 these specification updates is: 93 o Processing of ICMP Source Quench messages by routers has been 94 deprecated for more than 20 years [RFC1812]. 96 o Virtually all popular host implementations have removed support 97 for ICMP Source Quench messages since (at least) 2005 [RFC5927]. 99 o Widespread deployment of ICMP filtering makes it impossible to 100 rely on ICMP Source Quench messages for congestion control. 102 o The IETF has moved away from ICMP Source Quench messages for 103 congestion control (note e.g. the development of ECN [RFC3168], 104 and the fact that ICMPv6 [RFC4443] does not even specify a Source 105 Quench message). 107 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 108 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 109 document are to be interpreted as described in RFC 2119 [RFC2119]. 111 2. ICMP Source Quench messages 113 The ICMP specification [RFC0792] defined the ICMP Source Quench 114 message (type 4, code 0), which was meant to provide a mechanism for 115 congestion control. The Host Requirements RFC [RFC1122] stated in 116 Section 4.2.3.9 that hosts MUST react to ICMP Source Quench messages 117 by slowing transmission on the connection, and further added that the 118 RECOMMENDED procedure was to put the corresponding connection in the 119 slow-start phase of TCP's congestion control algorithm [RFC5681]. 121 [RFC1812] noted that research suggested that ICMP Source Quench was 122 an ineffective (and unfair) antidote for congestion, and formally 123 deprecated the generation of ICMP Source Quench messages by routers, 124 stating that routers SHOULD NOT send ICMP Source Quench messages in 125 response to congestion. 127 [RFC5927] discussed the use of ICMP Source Quench messages for 128 performing "blind throughput-reduction" attacks, and noted that most 129 TCP implementations silently ignore ICMP Source Quench messages. 131 We note that TCP implements its own congestion control mechanisms 132 [RFC5681] [RFC3168], that do not depend on ICMP Source Quench 133 messages. 135 It is interesting to note that ICMPv6 [RFC4443] does not specify a 136 "Source Quench" message. 138 3. Updating RFC 1122 140 This document hereby updates Section 3.2.2.3 of [RFC1122] as follows: 142 A host MUST NOT send ICMP Source Quench messages. 144 If a Source Quench message is received, the IP layer MAY silently 145 discard it. 147 Section 4.2.3.9 of [RFC1122] is updated as follows: 149 TCP MUST silently discard any received ICMP Source Quench 150 messages. 152 The consenus of the TSV WG was that there are no valid reasons for a 153 host to generate or react to an ICMP Source Quench message in the 154 current Internet. Discarding ICMP Source Quench messages at the 155 internet-layer (rather than at the transport layer) is a performance 156 optimization that is permitted by this update. 158 4. Updating RFC 1812 160 This document hereby updates Section 4.3.3.3 of [RFC1812] as follows: 162 A router MUST ignore any ICMP Source Quench messages it receives. 164 The consenus of the TSV WG was that there are no valid reasons for a 165 router to react to ICMP Source Quench messages in the current 166 Internet. 168 5. Clarification for SCTP and DCCP 170 It is understood that SCTP and SCCP did not specify support for 171 processing received ICMP Source Quench messages. Hereby we clarify 172 that DCCP and SCTP end-points MUST silently discard received ICMP 173 Source Quench messages. 175 6. General Advice to Transport Protocols 177 If a Source Quench message is received by any other transport- 178 protocol instance (e.g., a UDP-based protocol), it SHOULD be silently 179 ignored. 181 The TSV WG is not aware of any use that requires processing of these 182 messages, and therefore expects other transports to follow the 183 recommendations in Section 3. Note that for IETF-specified 184 transports, this document formally deprecates reaction to ICMP Source 185 Quench messages, and that generation of ICMP Source Quench messages 186 has been deprecated for both hosts and routers. Therefore, future 187 applications can not expect to receive these messages. 189 7. Changing the status of RFC 1016 to Historic 191 This document requests the RFC Editor to change the status of 192 [RFC1016] to "Historic". 194 8. Security Considerations 196 ICMP Source Quench messages could be leveraged for performing blind 197 throughput-reduction attacks against TCP and similar protocols. This 198 attack vector, along with possible countermeasures, has been 199 discussed in great detail in [RFC5927] and [CPNI-TCP]. However, as 200 noted in [RFC5927] and [CPNI-TCP], virtually all current versions of 201 popular TCP implementations already silently ignore ICMP Source 202 Quench messages. This is also the case for SCTP and DCCP 203 implementations. 205 Silently ignoring ICMP Source Quench messages, as specified in this 206 document, eliminates the aforementioned attack vector. 208 If deemed necessary, ICMP Source Quench messages could be filtered at 209 firewalls. 211 9. IANA Considerations 213 IANA is requested to mark ICMP type 4 (Source Quench) as "Deprecated" 214 in de ICMP Parameters registry [ICMPPARREG] with a reference to this 215 document. 217 10. Acknowledgements 219 The author of this document would like to thank (in alphabetical 220 order) Fred Baker, David Black, Scott Bradner, James Carlson, Antonio 221 De Simone, Gorry Fairhurst, Alfred Hoenes, Mahesh Jethanandani, 222 Carlos Pignataro, Anantha Ramaiah, Randall Stewart, Dan Wing, and 223 Andrew Yourtchenko, for providing valuable feedback on earlier 224 versions of this document. 226 This document has benefited from discussions within the TCPM Working 227 Group while working on [RFC5927]. 229 11. References 231 11.1. Normative References 233 [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, 234 RFC 792, September 1981. 236 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, 237 RFC 793, September 1981. 239 [RFC1016] Prue, W. and J. Postel, "Something a host could do with 240 source quench: The Source Quench Introduced Delay 241 (SQuID)", RFC 1016, July 1987. 243 [RFC1122] Braden, R., "Requirements for Internet Hosts - 244 Communication Layers", STD 3, RFC 1122, October 1989. 246 [RFC1812] Baker, F., "Requirements for IP Version 4 Routers", 247 RFC 1812, June 1995. 249 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 250 Requirement Levels", BCP 14, RFC 2119, March 1997. 252 [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion 253 Control", RFC 5681, September 2009. 255 11.2. Informative References 257 [CPNI-TCP] 258 CPNI, "Security Assessment of the Transmission Control 259 Protocol (TCP)", 2009, . 262 [FreeBSD] The FreeBSD Project, "http://www.freebsd.org". 264 [ICMPPARREG] 265 Internet Control Message Protocol (ICMP) Parameters, 266 "http://www.iana.org/assignments/icmp-parameters". 268 [Linux] The Linux Project, "http://www.kernel.org". 270 [NetBSD] The NetBSD Project, "http://www.netbsd.org". 272 [OpenBSD] The OpenBSD Project, "http://www.openbsd.org". 274 [OpenSolaris] 275 OpenSolaris, "http://www.opensolaris.org". 277 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 278 of Explicit Congestion Notification (ECN) to IP", 279 RFC 3168, September 2001. 281 [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control 282 Message Protocol (ICMPv6) for the Internet Protocol 283 Version 6 (IPv6) Specification", RFC 4443, March 2006. 285 [RFC5927] Gont, F., "ICMP Attacks against TCP", RFC 5927, July 2010. 287 Appendix A. Survey of support of ICMP Source Quench in some popular 288 TCP/IP implementations 290 A large number of implementations completely ignore ICMP Source 291 Quench messages meant for TCP connections. This behavior has been 292 implemented in, at least, Linux [Linux] since 2004, and in FreeBSD 293 [FreeBSD], NetBSD [NetBSD], OpenBSD [OpenBSD], and Solaris 10 since 294 2005. Additionally, OpenSolaris [OpenSolaris] has always shipped 295 with support for ICMP Source Quench messages disabled. 297 Appendix B. Changes from previous versions of the draft (to be removed 298 by the RFC Editor before publishing this document as an 299 RFC) 301 B.1. Changes from draft-ietf-tsvwg-source-quench-01 303 o Changes deprecation of ICMP SQ from "SHOULD NOT" to "MUST NOT" in 304 response of feedback from Scott Bradner and the TSV WG. 306 B.2. Changes from draft-ietf-tsvwg-source-quench-00 308 o Discusses the motivation for deprecating ICMP Source Quench 309 messages (as suggested by Anantha Ramaiah). 311 o Incorporates IANA considerations such that ICMP Source Quench 312 messages are deprecated in the corresponding registry. 314 B.3. Changes from draft-gont-tsvwg-source-quench-01 316 o Addresses nits and editorial chagnes suggested by Gorry Fairhurst. 318 o Added the status of Solaris and OpenSolaris to Appendix A. 320 o Document resubmitted as draft-ietf. 322 B.4. Changes from draft-gont-tsvwg-source-quench-00 324 o This revision reflects the recent discussion about ICMP Source 325 Quench messages on the tsvwg mailing-list. A detailed list of the 326 changes is available at: 327 http://www.ietf.org/mail-archive/web/tsvwg/current/msg10407.html 329 Author's Address 331 Fernando Gont 332 Universidad Tecnologica Nacional / Facultad Regional Haedo 333 Evaristo Carriego 2644 334 Haedo, Provincia de Buenos Aires 1706 335 Argentina 337 Phone: +54 11 4650 8472 338 Email: fernando@gont.com.ar 339 URI: http://www.gont.com.ar