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Gont 3 Internet-Draft UTN/FRH 4 Updates: 792, 1122, 1812 December 22, 2011 5 (if approved) 6 Intended status: Standards Track 7 Expires: June 24, 2012 9 Deprecation of ICMP Source Quench messages 10 draft-ietf-tsvwg-source-quench-03.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 June 24, 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 UDP, 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) . . . . . . . . . . . . . . . 8 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 consensus 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. The recommendation that a sender "MUST NOT" send 155 an ICMP Source Quench message is because there is no known valid 156 reason for a host to generate this message. The only known impact of 157 a sender ignoring this requirement is that it may necessarily consume 158 network and endpoint resources. Discarding ICMP Source Quench 159 messages at the internet-layer (rather than at the transport layer) 160 is a performance optimization that is permitted by this update. 162 4. Updating RFC 1812 164 This document hereby updates Section 4.3.3.3 of [RFC1812] as follows: 166 A router MUST ignore any ICMP Source Quench messages it receives. 168 The consensus of the TSV WG was that there are no valid reasons for a 169 router to react to ICMP Source Quench messages in the current 170 Internet. 172 5. Clarification for UDP, SCTP, and DCCP 174 UDP did not explicitly specify support for ICMP Source Quench 175 messages. Hereby we clarify that UDP end-points MUST silently 176 discard received ICMP Source Quench messages. 178 It is understood that SCTP and DCCP did not specify support for 179 processing received ICMP Source Quench messages. Hereby we clarify 180 that DCCP and SCTP end-points MUST silently discard received ICMP 181 Source Quench messages. 183 6. General Advice to Transport Protocols 185 If a Source Quench message is received by any other transport- 186 protocol instance, it MUST be silently ignored. 188 The TSV WG is not aware of any use that requires processing of these 189 messages, and therefore expects other transports to follow the 190 recommendations in Section 3. Note that for IETF-specified 191 transports, this document formally deprecates reaction to ICMP Source 192 Quench messages, and that generation of ICMP Source Quench messages 193 has been deprecated for both hosts and routers. Therefore, future 194 applications can not expect to receive these messages. 196 7. Changing the status of RFC 1016 to Historic 198 This document requests the RFC Editor to change the status of 199 [RFC1016] to "Historic". 201 8. Security Considerations 203 ICMP Source Quench messages could be leveraged for performing blind 204 throughput-reduction attacks against TCP and similar protocols. This 205 attack vector, along with possible countermeasures, has been 206 discussed in great detail in [RFC5927] and [CPNI-TCP]. 208 Even though sources "MUST NOT" send ICMP Source Quench Message, there 209 are no known security issues that result from receipt of this message 210 because, as noted in [RFC5927] and [CPNI-TCP], virtually all current 211 versions of popular TCP implementations already silently ignore ICMP 212 Source Quench messages. This is also the case for SCTP and DCCP 213 implementations. Receivers should not treat reception as an 214 exception, error or logged event. Receipt of an ICMP Source Quench 215 message must not be interpreted as an attempt to attack the receiver. 217 Silently ignoring ICMP Source Quench messages, as specified in this 218 document, eliminates the aforementioned attack vector. 220 If deemed necessary, ICMP Source Quench messages could be filtered at 221 firewalls. 223 9. IANA Considerations 225 IANA is requested to mark ICMP type 4 (Source Quench) as "Deprecated" 226 in de ICMP Parameters registry [ICMPPARREG] with a reference to this 227 document. 229 10. Acknowledgements 231 The author of this document would like to thank (in alphabetical 232 order) Fred Baker, David Black, Scott Bradner, James Carlson, Antonio 233 De Simone, Gorry Fairhurst, Alfred Hoenes, Mahesh Jethanandani, 234 Carlos Pignataro, Anantha Ramaiah, Randall Stewart, Dan Wing, and 235 Andrew Yourtchenko, for providing valuable feedback on earlier 236 versions of this document. 238 This document has benefited from discussions within the TCPM Working 239 Group while working on [RFC5927]. 241 11. References 243 11.1. Normative References 245 [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, 246 RFC 792, September 1981. 248 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, 249 RFC 793, September 1981. 251 [RFC1016] Prue, W. and J. Postel, "Something a host could do with 252 source quench: The Source Quench Introduced Delay 253 (SQuID)", RFC 1016, July 1987. 255 [RFC1122] Braden, R., "Requirements for Internet Hosts - 256 Communication Layers", STD 3, RFC 1122, October 1989. 258 [RFC1812] Baker, F., "Requirements for IP Version 4 Routers", 259 RFC 1812, June 1995. 261 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 262 Requirement Levels", BCP 14, RFC 2119, March 1997. 264 [RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion 265 Control", RFC 5681, September 2009. 267 11.2. Informative References 269 [CPNI-TCP] 270 CPNI, "Security Assessment of the Transmission Control 271 Protocol (TCP)", 2009, . 274 [FreeBSD] The FreeBSD Project, "http://www.freebsd.org". 276 [ICMPPARREG] 277 Internet Control Message Protocol (ICMP) Parameters, 278 "http://www.iana.org/assignments/icmp-parameters". 280 [Linux] The Linux Project, "http://www.kernel.org". 282 [NetBSD] The NetBSD Project, "http://www.netbsd.org". 284 [OpenBSD] The OpenBSD Project, "http://www.openbsd.org". 286 [OpenSolaris] 287 OpenSolaris, "http://www.opensolaris.org". 289 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 290 of Explicit Congestion Notification (ECN) to IP", 291 RFC 3168, September 2001. 293 [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control 294 Message Protocol (ICMPv6) for the Internet Protocol 295 Version 6 (IPv6) Specification", RFC 4443, March 2006. 297 [RFC5927] Gont, F., "ICMP Attacks against TCP", RFC 5927, July 2010. 299 Appendix A. Survey of support of ICMP Source Quench in some popular 300 TCP/IP implementations 302 A large number of implementations completely ignore ICMP Source 303 Quench messages meant for TCP connections. This behavior has been 304 implemented in, at least, Linux [Linux] since 2004, and in FreeBSD 305 [FreeBSD], NetBSD [NetBSD], OpenBSD [OpenBSD], and Solaris 10 since 306 2005. Additionally, OpenSolaris [OpenSolaris] has always shipped 307 with support for ICMP Source Quench messages disabled. 309 Appendix B. Changes from previous versions of the draft (to be removed 310 by the RFC Editor before publishing this document as an 311 RFC) 313 B.1. Changes from draft-ietf-tsvwg-source-quench-01 315 o Changes deprecation of ICMP SQ from "SHOULD NOT" to "MUST NOT" in 316 response of feedback from Scott Bradner and the TSV WG. 318 B.2. Changes from draft-ietf-tsvwg-source-quench-00 320 o Discusses the motivation for deprecating ICMP Source Quench 321 messages (as suggested by Anantha Ramaiah). 323 o Incorporates IANA considerations such that ICMP Source Quench 324 messages are deprecated in the corresponding registry. 326 B.3. Changes from draft-gont-tsvwg-source-quench-01 328 o Addresses nits and editorial changes suggested by Gorry Fairhurst. 330 o Added the status of Solaris and OpenSolaris to Appendix A. 332 o Document resubmitted as draft-ietf. 334 B.4. Changes from draft-gont-tsvwg-source-quench-00 336 o This revision reflects the recent discussion about ICMP Source 337 Quench messages on the tsvwg mailing-list. A detailed list of the 338 changes is available at: 339 http://www.ietf.org/mail-archive/web/tsvwg/current/msg10407.html 341 Author's Address 343 Fernando Gont 344 Universidad Tecnologica Nacional / Facultad Regional Haedo 345 Evaristo Carriego 2644 346 Haedo, Provincia de Buenos Aires 1706 347 Argentina 349 Phone: +54 11 4650 8472 350 Email: fernando@gont.com.ar 351 URI: http://www.gont.com.ar