idnits 2.17.1 draft-gont-v6ops-ipv6-ehs-in-real-world-00.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (August 7, 2014) is 3522 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 793 (Obsoleted by RFC 9293) ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) == Outdated reference: A later version (-10) exists of draft-ietf-6man-predictable-fragment-id-01 == Outdated reference: A later version (-03) exists of draft-wkumari-long-headers-02 Summary: 2 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPv6 Operations Working Group (v6ops) F. Gont 3 Internet-Draft SI6 Networks / UTN-FRH 4 Intended status: Informational J. Linkova 5 Expires: February 8, 2015 Google 6 T. Chown 7 University of Southampton 8 W. Liu 9 Huawei Technologies 10 August 7, 2014 12 IPv6 Extension Headers in the Real World 13 draft-gont-v6ops-ipv6-ehs-in-real-world-00 15 Abstract 17 IPv6 Extension Headers allow for the extension of the IPv6 protocol, 18 and provide support for some core functionality such as IPv6 19 fragmentation. However, IPv6 Extension Headers are deemed to present 20 a challenge to IPv6 implementations and networks, and are known to be 21 intentionally filtered in some existing IPv6 deployments. This 22 summarizes the issues associated with IPv6 extension headers, and 23 presents real-world data regarding the extent to which packets with 24 IPv6 extension headers are filtered in the public Internet, and where 25 in the network such filtering occurs. Additionally, it provides some 26 guidance to operators in troubleshooting IPv6 blackholes resulting 27 from the use of IPv6 extension headers. Finally, this document 28 provides some advice to protocol designers, and discusses areas where 29 further work might be needed. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on February 8, 2015. 48 Copyright Notice 50 Copyright (c) 2014 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 2. Previous Work on IPv6 Extension Headers . . . . . . . . . . . 3 67 3. Operational Implications . . . . . . . . . . . . . . . . . . 4 68 3.1. Performance Issues . . . . . . . . . . . . . . . . . . . 4 69 3.2. Security Implications . . . . . . . . . . . . . . . . . . 4 70 4. Support of IPv6 Extension Headers in the Public Internet . . 5 71 5. Implications of Widespread IPv6 Extension Header Filtering . 7 72 5.1. Advice to Protocol Designers . . . . . . . . . . . . . . 8 73 5.2. A possible attack vector . . . . . . . . . . . . . . . . 8 74 5.3. Possible Future Work . . . . . . . . . . . . . . . . . . 8 75 6. Troubleshooting Packet Drops due to IPv6 Extension Headers . 9 76 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 77 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 78 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 79 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 80 10.1. Normative References . . . . . . . . . . . . . . . . . . 9 81 10.2. Informative References . . . . . . . . . . . . . . . . . 10 82 Appendix A. Measurements Caveats . . . . . . . . . . . . . . . . 12 83 A.1. Isolating the Dropping Node . . . . . . . . . . . . . . . 12 84 A.2. Obtaining the Responsible Organization for the Packet 85 Drops . . . . . . . . . . . . . . . . . . . . . . . . . . 13 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 88 1. Introduction 90 IPv6 Extension Headers (EHs) allow for the extension of the IPv6 91 protocol, and provide support for core functionality such as IPv6 92 fragmentation. However, IPv6 Extension Headers have been deemed to 93 present a challenge to IPv6 implementations and networks, and have 94 been assumed/known to be intentionally filtered in some existing IPv6 95 deployments. 97 Discussions over the operational implications of IPv6 extension 98 headers and their usability in the public Internet come up over and 99 over again at both in IETF circles and other venues, and not 100 infrequently some key aspects involving IPv6 extension headers are 101 overlooked. 103 This document tries raise awareness about the operational 104 implications of IPv6 Extension Headers, and their usability in the 105 public Internet. Additionally, it provides some guidance in 106 troubleshooting IPv6 blackholes resulting from the filtering of 107 packets that employ IPv6 extension headers. Finally, it aims to 108 raise awareness about the operational reality of IPv6 extension 109 headers to protocol designers, and trigger discussion within the IETF 110 community regarding areas where future work might be required. 112 Section 2 of this document summarizes the work that has been done in 113 the area of IPv6 extension headers. Section 3 discusses the 114 operational implications of IPv6 Extension Headers. Section 4 115 presents real-world data regarding the extent to which IPv6 Extension 116 Headers are usable in the public Internet. Section 5 provides advise 117 to protocol designers regarding the use of IPv6 extension headers, 118 and aims to raise awareness about the possible interoperability 119 implications on existing protocols. Finally, Section 6 provides some 120 guidance in troubleshooting of problems that may arise as a result of 121 filtering packets that employ IPv6 Extension Headers. 123 2. Previous Work on IPv6 Extension Headers 125 Some of the implications of IPv6 Extension Headers have been 126 discussed in IETF circles. For example, [I-D.taylor-v6ops-fragdrop] 127 discusses a rationale for which operators filter IPv6 fragments. 128 [I-D.wkumari-long-headers] discusses possible issues arising from 129 "long" IPv6 header chains. [RFC7045] clarifies how intermediate 130 nodes should deal with IPv6 extension headers. [RFC7112] discusses 131 the issues arising in a specific case where the IPv6 header chain is 132 fragmented into two or more fragments (and formally forbids such 133 case). [RFC6980] analyzes the security implications of employing 134 IPv6 fragmentation with Neighbor Discovery for IPv6, and formally 135 recommends against such usage. Finally, [RFC7123] discusses how some 136 popular RA-Guard implementations are subject to evasion by means of 137 IPv6 extension headers. 139 While packets employing IPv6 Extension Headers have been "known" to 140 be dropped in some IPv6 deployments, there was not much concrete data 141 on the topic. Some preliminary measurements have been presented in 142 [PMTUD-Blackholes], [Gont-IEPG88] and [Gont-Chown-IEPG89], whereas 143 [Linkova-Gont-IEPG90] presents more comprehensive results on which 144 Section 4 of this document is based. 146 3. Operational Implications 148 3.1. Performance Issues 150 Many IPv6 router implementations suffer from a negative performance 151 impact when IPv6 Extension Headers are employed. 153 In the most trivial case, a packet that includes a Hop-by-Hop Options 154 header will typically go through the slow forwarding path, and be 155 processed by the router's CPU. Another case is that in which a 156 router that has been configured to enforce an ACL based on upper- 157 layer information (e.g., upper layer protocol or TCP Destination 158 Port). In such case, the router will need to process the entire IPv6 159 header chain in order to find the required information, and this may 160 cause the packet to be processed in the slow path [Cisco-EH-Cons]. 162 Processing a large amounts of traffic in the slow patch may cause the 163 router to be unable to handle the same traffic loads when compared to 164 normal packets, and may result in Denial of Service (DoS) scenarios. 166 We note that, for obvious reasons, the aforementioned performance 167 issues may also affect other devices such as firewalls, Network 168 Intrusion Detection Systems (NIDS), etc. [Zack-FW-Benchmark]. 170 3.2. Security Implications 172 The security implications of IPv6 Extension Headers generally fall 173 into one or more of these categories: 175 o Evasion of security controls 177 o DoS due to processing requirements 179 o DoS due to implementation errors 181 o Extension Header-specific issues 183 Different from IPv4, where the upper-layer protocol can be found 184 after the variable-length IPv4 header, the structure of IPv6 packets 185 is both more flexible and complex. Namely, finding the upper-layer 186 information may imply processing the (daisy-chain like) entire IPv6 187 header chain. This has been often overlooked, and a number of 188 security devices have been found to be trivially evasible by 189 inserting one or more IPv6 Extension Headers between the main IPv6 190 header and the upper layer protocol. [RFC7113] describes this issue 191 for the RA-Guard case, but same same techniques can be employed for 192 circumventing e.g. some IPv6 firewalls. Additionally, 193 inconsistencies in how some packets may be processed may result in 194 evasion of security controls [I-D.kampanakis-6man-ipv6-eh-parsing] 195 [Atlasis2014]. 197 As noted in Section 3.1, packets that employ IPv6 Extension Headers 198 may have a negative performance impact on the handling devices. 199 Unless appropriate mitigations are put in place (e.g., packet 200 filtering and/or rate-limiting), an attacker could simply send a 201 large amount of IPv6 traffic employing IPv6 Extension Headers with 202 the purpose of performing a Denial of Service (DoS) attack. 204 IPv6 implementations, as virtually every piece of software, tend to 205 mature over time. While the IPv6 protocol itself (and many 206 implementations) have been around for a long time already, bugs in 207 IPv6 Extension Header processing have been recently found in a number 208 of implementations. Because there is currently almost no reliance on 209 IPv6 Extension headers, the corresponding code paths are rarely 210 exercised, and there is the potential that bugs still remain to be 211 discovered in some implementations. 213 Besides the general implications of IPv6 Extension Headers, each 214 Extension Header tends to its own specific implications. One 215 particular case is that of the Fragment Header, which is employed to 216 provide the fragmentation function in IPv6. While many of the 217 security implications of the fragmentation/reassembly mechanism are 218 known from the IPv4 world, many of the related issues have creeped 219 into IPv6 implementations. They range from Denial of Service attacks 220 to information leakage (see e.g. 221 [I-D.ietf-6man-predictable-fragment-id], [Bonica-NANOG58], 222 [Atlasis2012]). 224 4. Support of IPv6 Extension Headers in the Public Internet 226 This section summarizes the results obtained when measuring the 227 support of IPv6 Extension Headers on the path towards different types 228 of public IPv6 servers. Two sources were employed for the list of 229 public IPv6 servers: the "World IPv6 Launch Day" site 230 (http://www.worldipv6launch.org/) and Alexa's top 1M web sites 231 (http://www.alexa.com). For each list of domain names, the following 232 datasets were obtained: 234 o Web servers (AAAA records of the aforementioned list) 236 o Mail servers (MX -> AAAA of such list 238 o Name servers (NS -> AAAA of such list) 240 Duplicate and unreachable addresses were eliminated from each of 241 those lists prior to obtaining the results below. 243 For each of the aforementioned address sets, three different types of 244 probes were sent: 246 o IPv6 packets with a Destination Options header of 8 bytes 248 o IPv6 packets resulting in two IPv6 fragments of 512 bytes each 249 (approximately) 251 o IPv6 packets with a Hop-by-Hop Options header of 8 bytes 253 In the case of packets with Destination Options Header and Hop-by-Hop 254 Options header, the desired EH size was achieved by means of PadN 255 options [RFC2460]. The upper-layer protocol of the probe packets 256 was, in all cases, TCP [RFC0793] segments with the Destination Port 257 set to the service port [IANA-PORT-NUMBERS] of the corresponding 258 dataset. For example, the probe packets for all the measurements 259 involving web servers were TCP segments with the destination port set 260 to 80. 262 Besides obtaining the packet drop rate when employing the 263 aforementioned IPv6 extension headers, we tried to identify whether 264 the Autonomous System (AS) dropping the packets was the same as the 265 Autonomous System of the destination/target address. This is of 266 particular interest since it essentially reveals whether the packet 267 drops are under the control of the intended destination of the 268 packets. Packets dropped by the destination AS are less of a 269 concern, since they can be assumed to be the result of an explicit 270 policy of the organization to which the packets are destined (who can 271 make its own decision regarding what kind of traffic is 272 "acceptable"). On the other hand, packets dropped by transit ASes 273 are more of a concern, since they affect the deployability and 274 usability of IPv6 extension headers (including IPv6 fragmentation) 275 regardless of the intent of the communicating end-points. Thus, when 276 packet drops do occur, the "best-case scenario" is that in which the 277 packets are dropped by the destination AS, whereas the "worst-case 278 scenario" is that in which the packets are dropped by a transit AS. 279 Since there is some ambiguity when identifying the autonomous system 280 to which a specific router belongs (see Appendix A.2, our 281 measurements result in a percentage *range*: the lowest percentage 282 value represents the "best case scenario" (where, when in doubt, we 283 assume the packet drops occur in the same AS as the destination AS), 284 and the highest percentage value represents the "worst case scenario" 285 (where, when in doubt, we assume the packet drops occur at different 286 AS than the destination AS). 288 +--------------+-----------------+-----------------+----------------+ 289 | Dataset | DO8 | HBH8 | FH512 | 290 +--------------+-----------------+-----------------+----------------+ 291 | Web | 11.88% | 40.70% | 30.51% | 292 | | (17.60%-20.80%) | (31.43%-40.00%) | (5.08%-6.78%) | 293 +--------------+-----------------+-----------------+----------------+ 294 | Mailservers | 17.07% | 48.86% | 39.17% | 295 | | (6.35%-26.98%) | (40.50%-65.42%) | (2.91%-12.73%) | 296 +--------------+-----------------+-----------------+----------------+ 297 | Namerservers | 15.37% | 43.25% | 38.55% | 298 | | (14.29%-33.46%) | (42.49%-72.07%) | (3.90%-13.96%) | 299 +--------------+-----------------+-----------------+----------------+ 301 Table 1: WIPv6LD dataset: Packet drop rate for different destination 302 types 304 +-------------+-----------------+-----------------+-----------------+ 305 | Dataset | DO8 | HBH8 | FH512 | 306 +-------------+-----------------+-----------------+-----------------+ 307 | Web | 10.91% | 39.03% | 28.26% | 308 | | (46.52%-53.23%) | (36.90%-46.35%) | (53.64%-61.43%) | 309 +-------------+-----------------+-----------------+-----------------+ 310 | Mailservers | 11.54% | 45.45% | 35.68% | 311 | | (2.41%-21.08%) | (41.27%-61.13%) | (3.15%-10.92%) | 312 +-------------+-----------------+-----------------+-----------------+ 313 | Namerserver | 21.33% | 54.12% | 55.23% | 314 | s | (10.27%-56.80%) | (50.64%-81.00%) | (5.66%-32.23%) | 315 +-------------+-----------------+-----------------+-----------------+ 317 Table 2: Alexa's top 1M sites dataset: Packet drop rate for different 318 destination types 320 There are a number of observations to be made based on the results 321 presented above. Firstly, while it has been generally assumed that 322 it is IPv6 fragments that are dropped by operators, our results 323 indicate that it is IPv6 extension headers in general that are 324 dropped. Secondly, our results indicate that a significant 325 percentage of such packet drops occur in transit Autonomous Systems; 326 that is, the packet drops are not under the control of the same 327 organization as the final destination. 329 5. Implications of Widespread IPv6 Extension Header Filtering 331 The results presented in Section 4 indicate that at least for part of 332 the public Internet, communication employing IPv6 extension headers 333 is unreliable. The following subsections discuss specific 334 implications arising from this conclusion. 336 5.1. Advice to Protocol Designers 338 New protocols that are to operate in the public Internet should 339 consider the effect of widespread filtering of IPv6 extension headers 340 in the public Internet. If IPv6 extension headers are at all 341 employed, a fall-back mechanism that does not rely on IPv6 extension 342 headers should be considered. 344 5.2. A possible attack vector 346 The widespread filtering of IPv6 packets employing IPv6 Extension 347 Headers could, in some scenarios, be exploited for malicious 348 purposes: if packets employing IPv6 EHs are known to be filtered on 349 the path from one system (say, "A") to another (say, "B"), an 350 attacker could cause packets sent from A to B to be dropped by 351 sending a forged an ICMPv6 Packet Too Big [RFC4443] error message to 352 A (with a Next-Hop MTU smaller than 1280), such that subsequent 353 packets from A to B include a fragment header (i.e., they result in 354 atomic fragments [RFC6946]). 356 A problem with this attack scenario is that a node cannot simply 357 "filter/drop all incoming ICMPv6 Packet Too Big error messages", or 358 else it might not be able to properly reduce the assumed path MTU 359 when communicating with other IPv6 nodes. 361 Possible mitigations for this issue include: 363 o Filtering incoming ICMPv6 Packet Too Big (PTB) error messages that 364 advertise a Next-Hop MTU smaller than 1280 bytes. 366 o Artificially reducing the MTU to 1280 bytes and filter incoming 367 ICMPv6 PTB error messages 369 Filtering only those ICMPv6 PTB messages that advertise a Next-Hop 370 MTU smaller than 1280 would prevent the generation of IPv6 atomic 371 fragments without breaking Path-MTU Discovery. However, such 372 filtering would require deep packet inspection, and such 373 functionality (if at all desirable) might not be available. 375 5.3. Possible Future Work 377 The impact of widespread filtering of IPv6 EHs on existing protocols 378 should be considered. In particular, the effect of widespread 379 filtering of IPv6 fragments on the Domain Name System (DNS) [RFC1034] 380 should be evaluated (particularly when it is expected that reliance 381 on IPv6 transport will increase over time). 383 6. Troubleshooting Packet Drops due to IPv6 Extension Headers 385 Isolating IPv6 blackholes essentially involves performing IPv6 386 traceroute for a destination system with and without IPv6 extension 387 headers. The (EH-free) traceroute would provide the full working 388 path towards a destination, while the EH-enabled traceroute would 389 provide the address of the last-responding node for EH-enabled 390 packets (say, "M"). In principle, one could isolate the dropping 391 node by looking-up "M" in the EH-free traceroute, with the dropping 392 node being "M+1" (see Appendix A.1 for caveats). 394 At the time of this writing, most traceroute implementations do not 395 support IPv6 extension headers. However, the path6 tool [path6] and 396 RIPE Atlas [RIPE-Atlas] provide such support. Additionally, the 397 blackhole6 tool [blackhole6] automates the troubleshooting process 398 and can readily provide information such as: dropping node's IPv6 399 address, dropping node's Autonomous System, etc. 401 7. IANA Considerations 403 There are no IANA registries within this document. The RFC-Editor 404 can remove this section before publication of this document as an 405 RFC. 407 8. Security Considerations 409 The security implications of IPv6 extension headers are discussed in 410 Section 3.2. This document does not introduce any new security 411 issues. 413 9. Acknowledgements 415 Fernando Gont would like to thank Jan Zorz and Go6 Lab 416 for providing access to systems and networks that 417 were employed to produce some of the measurement results presented in 418 this document. Additionally, he would like to thank SixXS 419 for providing IPv6 connectivity. 421 10. References 423 10.1. Normative References 425 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 426 793, September 1981. 428 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 429 STD 13, RFC 1034, November 1987. 431 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 432 (IPv6) Specification", RFC 2460, December 1998. 434 [RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control 435 Message Protocol (ICMPv6) for the Internet Protocol 436 Version 6 (IPv6) Specification", RFC 4443, March 2006. 438 [RFC6946] Gont, F., "Processing of IPv6 "Atomic" Fragments", RFC 439 6946, May 2013. 441 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 442 with IPv6 Neighbor Discovery", RFC 6980, August 2013. 444 [RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing 445 of IPv6 Extension Headers", RFC 7045, December 2013. 447 [RFC7112] Gont, F., Manral, V., and R. Bonica, "Implications of 448 Oversized IPv6 Header Chains", RFC 7112, January 2014. 450 [RFC7113] Gont, F., "Implementation Advice for IPv6 Router 451 Advertisement Guard (RA-Guard)", RFC 7113, February 2014. 453 [RFC7123] Gont, F. and W. Liu, "Security Implications of IPv6 on 454 IPv4 Networks", RFC 7123, February 2014. 456 10.2. Informative References 458 [Atlasis2012] 459 Atlasis, A., "Attacking IPv6 Implementation Using 460 Fragmentation", BlackHat Europe 2012. Amsterdam, 461 Netherlands. March 14-16, 2012, 462 . 465 [Atlasis2014] 466 Atlasis, A., "A Novel Way of Abusing IPv6 Extension 467 Headers to Evade IPv6 Security Devices", May 2014, 468 . 471 [Bonica-NANOG58] 472 Bonica, R., "IPv6 Extension Headers in the Real World 473 v2.0", NANOG 58. New Orleans, Louisiana, USA. June 3-5, 474 2013, . 477 [Cisco-EH-Cons] 478 Cisco, , "IPv6 Extension Headers Review and 479 Considerations", October 2006, 480 . 483 [Gont-Chown-IEPG89] 484 Gont, F. and T. Chown, "A Small Update on the Use of IPv6 485 Extension Headers", IEPG 89. London, UK. March 2, 2014, 486 . 489 [Gont-IEPG88] 490 Gont, F., "Fragmentation and Extension header Support in 491 the IPv6 Internet", IEPG 88. Vancouver, BC, Canada. 492 November 13, 2013, . 495 [I-D.ietf-6man-predictable-fragment-id] 496 Gont, F., "Security Implications of Predictable Fragment 497 Identification Values", draft-ietf-6man-predictable- 498 fragment-id-01 (work in progress), April 2014. 500 [I-D.kampanakis-6man-ipv6-eh-parsing] 501 Kampanakis, P., "Implementation Guidelines for parsing 502 IPv6 Extension Headers", draft-kampanakis-6man-ipv6-eh- 503 parsing-01 (work in progress), August 2014. 505 [I-D.taylor-v6ops-fragdrop] 506 Jaeggli, J., Colitti, L., Kumari, W., Vyncke, E., Kaeo, 507 M., and T. Taylor, "Why Operators Filter Fragments and 508 What It Implies", draft-taylor-v6ops-fragdrop-02 (work in 509 progress), December 2013. 511 [I-D.wkumari-long-headers] 512 Kumari, W., Jaeggli, J., and R. Bonica, "Operational 513 Issues Associated With Long IPv6 Header Chains", draft- 514 wkumari-long-headers-02 (work in progress), October 2013. 516 [IANA-PORT-NUMBERS] 517 IANA, "Service Name and Transport Protocol Port Number 518 Registry", . 522 [Linkova-Gont-IEPG90] 523 Linkova, J. and F. Gont, "IPv6 Extension Headers in the 524 Real World v2.0", IEPG 90. Toronto, ON, Canada. July 20, 525 2014, . 528 [PMTUD-Blackholes] 529 De Boer, M. and J. Bosma, "Discovering Path MTU black 530 holes on the Internet using RIPE Atlas", July 2012, 531 . 534 [RIPE-Atlas] 535 RIPE, , "RIPE Atlas", . 537 [Zack-FW-Benchmark] 538 Zack, E., "Firewall Security Assessment and Benchmarking 539 IPv6 Firewall Load Tests", IPv6 Hackers Meeting #1, 540 Berlin, Germany. June 30, 2013, 541 . 545 [blackhole6] 546 blackhole6, , "blackhole6 tool manual page", 547 , 2014. 549 [path6] path6, , "path6 tool manual page", 550 , 2014. 552 Appendix A. Measurements Caveats 554 A number of issues have needed some consideration when producing the 555 results presented in Section 4. These same issues should be 556 considered when troubleshooting connectivity problems resulting from 557 the use of IPv6 Extension headers. 559 A.1. Isolating the Dropping Node 561 Let us assume that we find that IPv6 EHs are dropping on their way to 562 the destination system 2001:db8:d::1, and the output of running 563 traceroute towards such destination is: 565 1. 2001:db8:1:1000::1 566 2. 2001:db8:2:2000::4 567 3. 2001:db8:2:4000::1 568 4. 2001:db8:3:4000::1 569 5. 2001:db8:3:1000::1 570 6. 2001:db8:4:4000::1 571 7. 2001:db8:4:1000::1 572 8. 2001:db8:5:5000::1 573 9. 2001:db8:5:6000::1 574 10. 2001:db8:d::1 576 and the output of EH-enabled traceroute to the same destination is: 578 1. 2001:db8:1:1000::1 579 2. 2001:db8:2:2000::4 580 3. 2001:db8:2:4000::1 581 4. 2001:db8:3:4000::1 582 5. 2001:db8:3:1000::1 583 6. 2001:db8:4:4000::1 585 For the sake of brevity, let us refer to the last-responding node in 586 the EH-enabled traceroute ("2001:db8:4:4000::1" in this case) as "M". 587 Assuming both packets in both traceroutes employ the same path, we'll 588 refer to "the node following the last responding node in the EH- 589 enabled traceroute" ("2001:db8:4:1000::1" in our case), as "M+1", 590 etc. 592 Based on traceroute information above, which node is the one actually 593 dropping the EH-enabled packets will depend on whether the dropping 594 node filters packets on ingress or the egress. If the former, the 595 dropping node will be M+1. If the latter, the dropping node will be 596 "M". 598 Throughout this document (and our measurements), we assume that nodes 599 perform ingress-filtering. Thus, in our example above the last 600 responding node to the EH-enabled traceroute ("M") is 601 "2001:db8:4:4000::1", and therefore we assume the "node" dropping 602 node to be "2001:db8:4:1000::1" ("M+1"). 604 Additionally, we note that when isolating the dropping node we assume 605 that both the EH-enabled and the EH-free traceroutes result in the 606 same paths. However, this might not be the case. 608 A.2. Obtaining the Responsible Organization for the Packet Drops 610 In order to identify the organization operating the dropping node, 611 one would be tempted to lookup the ASN corresponding to the dropping 612 node. However, assuming that M and M+1 are two peering routers, any 613 of these two organizations could be providing the address space 614 employed for such peering. Or, in the case of an Internet eXchange 615 Point (IXP), the address space could correspond to the IXP AS, rather 616 than to any of the participating ASes. Thus, the organization 617 operating the dropping node (M+1) could be the AS for M+1, but it 618 might as well be the AS for M+2. Only when the ASN for M+1 is the 619 same as the ASN for M+2 we have certainty about who the responsible 620 organization for the packet drops is (see slides 21-23 of 621 [Linkova-Gont-IEPG90]). 623 In the measurement results presented in Section 4, the aforementioned 624 ambiguity results in "percentage ranges" (rather than a specific 625 ratio). This same ambiguity should be considered when 626 troubleshooting and reporting IPv6 packet drops. 628 Finally, we note that a specific organization might be operating more 629 than one Autonomous System. However, our measurements assume that 630 different Autonomous System Numbers imply different organizations. 632 Authors' Addresses 634 Fernando Gont 635 SI6 Networks / UTN-FRH 636 Evaristo Carriego 2644 637 Haedo, Provincia de Buenos Aires 1706 638 Argentina 640 Phone: +54 11 4650 8472 641 Email: fgont@si6networks.com 642 URI: http://www.si6networks.com 644 J. Linkova 645 Google 646 1600 Amphitheatre Parkway 647 Mountain View, CA 94043 648 USA 650 Email: furry@google.com 652 Tim Chown 653 University of Southampton 654 Highfield 655 Southampton , Hampshire SO17 1BJ 656 United Kingdom 658 Email: tjc@ecs.soton.ac.uk 659 Will (Shucheng) Liu 660 Huawei Technologies 661 Bantian, Longgang District 662 Shenzhen 518129 663 P.R. China 665 Email: liushucheng@huawei.com