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Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- -- Obsolete informational reference (is this intentional?): RFC 6555 (Obsoleted by RFC 8305) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Perreault 3 Internet-Draft Jive Communications 4 Intended status: Informational T. Tsou 5 Expires: October 24, 2015 Huawei Technologies (USA) 6 C. Zhou 7 Huawei Technologies 8 P. Fan 9 China Mobile 10 April 22, 2015 12 Gap Analysis for IPv4 Sunset 13 draft-ietf-sunset4-gapanalysis-07 15 Abstract 17 Sunsetting IPv4 refers to the process of turning off IPv4 18 definitively. It can be seen as the final phase of the migration to 19 IPv6. This memo enumerates difficulties arising when sunsetting 20 IPv4, and identifies the gaps requiring additional work. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on October 24, 2015. 39 Copyright Notice 41 Copyright (c) 2015 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Related Work . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Remotely Disabling IPv4 . . . . . . . . . . . . . . . . . . . 4 59 3.1. Indicating that IPv4 connectivity is unavailable . . . . 4 60 3.2. Disabling IPv4 in the LAN . . . . . . . . . . . . . . . . 4 61 4. Client Connection Establishment Behavior . . . . . . . . . . 5 62 5. Disabling IPv4 in Operating System and Applications . . . . . 5 63 6. On-Demand Provisioning of IPv4 Addresses . . . . . . . . . . 6 64 7. IPv4 Address Literals . . . . . . . . . . . . . . . . . . . . 6 65 8. Managing Router Identifiers . . . . . . . . . . . . . . . . . 7 66 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 67 10. Security Considerations . . . . . . . . . . . . . . . . . . . 7 68 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 69 12. Informative References . . . . . . . . . . . . . . . . . . . 7 70 Appendix A. Solution Ideas . . . . . . . . . . . . . . . . . . . 9 71 A.1. Remotely Disabling IPv4 . . . . . . . . . . . . . . . . . 9 72 A.1.1. Indicating that IPv4 connectivity is unavailable . . 9 73 A.1.2. Disabling IPv4 in the LAN . . . . . . . . . . . . . . 9 74 A.2. Client Connection Establishment Behavior . . . . . . . . 10 75 A.3. Disabling IPv4 in Operating System and Applications . . . 10 76 A.4. Managing Router Identifiers . . . . . . . . . . . . . . . 10 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 79 1. Introduction 81 The final phase of the migration to IPv6 is the sunset of IPv4, that 82 is turning off IPv4 definitively on the attached networks and on the 83 upstream networks. 85 Some current implementation behavior makes it hard to sunset IPv4. 86 Additionally, some new features could be added to IPv4 to make its 87 sunsetting easier. This document analyzes the current situation and 88 proposes new work in this area. 90 The decision about when to turn off IPv4 is out of scope. This 91 document merely attempts to enumerate the issues one might encounter 92 if that decision is made. 94 2. Related Work 96 [RFC3789], [RFC3790],[RFC3791], [RFC3792], [RFC3793], [RFC3794], 97 [RFC3795] and [RFC3796] contain surveys of IETF protocols with their 98 IPv4 dependencies. 100 Additionally, although reviews in RFCs 3789-3796 ensured that IETF 101 standards then in use could support IPv6, no IETF-wide effort has 102 been undertaken to ensure that the issues identified in those drafts 103 are all addressed, nor to ensure that standards written after RFC3100 104 (where the previous review efforts stopped) function properly on 105 IPv6-only networks. 107 The IETF needs to ensure that existing standards and protocols have 108 been actively reviewed, and any parity gaps either identified so that 109 they can be fixed, or documented as unnecessary to address because it 110 is unused or superseded by other features. 112 First, the IETF must review RFCs 3789-3796 to ensure that any gaps in 113 specifications identified in these documents and still in active use 114 have been updated as necessary to enable operation in IPv6-only 115 environments (or if no longer in use, are declared historic). 117 Second, the IETF must review documents written after the existing 118 review stopped (according to RFC 3790, this review stopped with 119 approximately RFC 3100) to identify specifications where IPv6-only 120 operation is not possible, and update them as necessary and 121 appropriate, or document why an identified gap is not an issue i.e. 122 not necessary for functional parity with IPv4. 124 This document does not recommend excluding Informational and BCP RFCs 125 as the previous effort did, due to changes in the way that these 126 documents are used and their relative importance in the RFC Series. 127 Instead, any documents that are still active (i.e. not declared 128 historic or obsolete) and the product of IETF consensus (i.e. not a 129 product of the ISE Series) should be included. In addition, the 130 reviews undertaken by RFCs 3789-3796 were looking for "IPv4 131 dependency" or "usage of IPv4 addresses in standards". This document 132 recommends a slightly more specific set of criteria for review. 133 Reviews should include: 135 o Consideration of whether the specification can operate in an 136 environment without IPv4. 138 o Guidance on the use of 32-bit identifiers that are commonly 139 populated by IPv4 addresses. 141 o Consideration of protocols on which specifications depend or 142 interact, to identify indirect dependencies on IPv4. 144 o Consideration of how to migrate from an IPv4 environment to an 145 IPv6 environment. 147 3. Remotely Disabling IPv4 149 3.1. Indicating that IPv4 connectivity is unavailable 151 PROBLEM 1: When an IPv4 node boots and requests an IPv4 address 152 (e.g., using DHCP), it typically interprets the absence 153 of a response as a failure condition even when it is not. 155 PROBLEM 2: Home router devices often identify themselves as default 156 routers in DHCP responses that they send to requests 157 coming from the LAN, even in the absence of IPv4 158 connectivity on the WAN. 160 3.2. Disabling IPv4 in the LAN 162 PROBLEM 3: IPv4-enabled hosts inside an IPv6-only LAN can auto- 163 configure IPv4 addresses [RFC3927] and enable various 164 protocols over IPv4 such as mDNS [RFC6762] and LLMNR 165 [RFC4795]. This can be undesirable for operational or 166 security reasons, since in the absence of IPv4, no 167 monitoring or logging of IPv4 will be in place. 169 PROBLEM 4: IPv4 can be completely disabled on a link by filtering it 170 on the L2 switching device. However, this may not be 171 possible in all cases or may be too complex to deploy. 172 For example, an ISP is often not able to control the L2 173 switching device in the subscriber home network. 175 PROBLEM 5: A host with only Link-Local IPv4 addresses will "ARP for 176 everything", as described in Section 2.6.2 of [RFC3927]. 177 Applications running on such a host connected to an 178 IPv6-only network will believe that IPv4 connectivity is 179 available, resulting in various bad or sub-optimal 180 behavior patterns. See 181 [I-D.yourtchenko-ipv6-disable-ipv4-proxyarp] for further 182 analysis. 184 Some of these problems were described in [RFC2563], which 185 standardized a DHCP option to disable IPv4 address auto- 186 configuration. However, using this option requires running an IPv4 187 DHCP server, which is contrary to the goal of IPv4 sunsetting. 189 4. Client Connection Establishment Behavior 191 PROBLEM 6: Happy Eyeballs [RFC6555] refers to multiple approaches to 192 dual-stack client implementations that try to reduce 193 connection setup delays by trying both IPv4 and IPv6 194 paths simultaneously. Some implementations introduce 195 delays which provide an advantage to IPv6, while others 196 do not [Huston2012]. The latter will pick the fastest 197 path, no matter whether it is over IPv4 or IPv6, 198 directing more traffic over IPv4 than the other kind of 199 implementations. This can prove problematic in the 200 context of IPv4 sunsetting, especially for Carrier-Grade 201 NAT phasing out because CGN does not add significant 202 latency that would make the IPv6 path more preferable. 203 Traffic will therefore continue using the CGN path unless 204 other network conditions change. 206 PROBLEM 7: getaddrinfo() [RFC3493] sends DNS queries for both A and 207 AAAA records regardless of the state of IPv4 or IPv6 208 availability. The AI_ADDRCONFIG flag can be used to 209 change this behavior, but it relies on programmers using 210 the getaddrinfo() function to always pass this flag to 211 the function. The current situation is that in an 212 IPv6-only environment, many useless A queries are made. 214 5. Disabling IPv4 in Operating System and Applications 216 It is possible to completely remove IPv4 support from an operating 217 system as has been shown by the work of Bjoern Zeeb on FreeBSD. 218 [Zeeb] Removing IPv4 support in the kernel revealed many IPv4 219 dependencies in libraries and applications. 221 PROBLEM 8: Completely disabling IPv4 at runtime often reveals 222 implementation bugs. Hard-coded dependencies on IPv4 223 abound, such as on the 127.0.0.1 address assigned to the 224 loopback interface, and legacy IPv4-only APIs are widely 225 used by applications. It is hard for the administrators 226 and users to know what applications running on the 227 operating system have implementation problems of IPv4 228 dependency. It is therefore often operationally 229 impossible to completely disable IPv4 on individual 230 nodes. 232 PROBLEM 9: In an IPv6-only world, legacy IPv4 code in operating 233 systems and applications incurs a maintenance overhead 234 and can present security risks. 236 6. On-Demand Provisioning of IPv4 Addresses 238 As IPv6 usage climbs, the usefulness of IPv4 addresses to subscribers 239 will become smaller. This could be exploited by an ISP to save IPv4 240 addresses by provisioning them on-demand to subscribers and 241 reclaiming them when they are no longer used. This idea is described 242 in [I-D.fleischhauer-ipv4-addr-saving] and [BBF.TR242] for the 243 context of PPP sessions. In these scenarios, the home router is 244 responsible for requesting and releasing IPv4 addresses, based on 245 snooping the traffic generated by the hosts in the LAN, which are 246 still dual-stack and unaware that their traffic is being snooped. 248 PROBLEM 10: Dual-stack hosts that implement Happy-Eyeballs [RFC6555] 249 will generate both IPv4 and IPv6 traffic even if the 250 algorithm end up chooosing IPv6. This means that an IPv4 251 address will always be requested by the home router, 252 which defeats the purpose of on-demand provisioning. 254 PROBLEM 11: Many operating systems periodically perform some kind of 255 network connectivity check as long as an interface is up. 256 Similarly, applications often send keep-alive traffic 257 continuously. This permanent "background noise" will 258 prevent an IPv4 address from being released by the home 259 router. 261 PROBLEM 12: Hosts in the LAN have no knowledge that IPv4 is available 262 to them on-demand only. If they had explicit knowledge 263 of this fact, they could tune their behaviour so as to be 264 more conservative in their use of IPv4. 266 PROBLEM 13: This mechanism is only being proposed for PPP even though 267 it could apply to other provisioning protocols (e.g., 268 DHCP). 270 7. IPv4 Address Literals 272 IPv4 addresses are often used as resource locators. For example, it 273 is common to encounter URLs containing IPv4 address literals on web 274 sites [I-D.wing-behave-http-ip-address-literals]. IPv4 address 275 literals may be published on media other than web sites, and may 276 appear in various forms other than URLs. For the operating systems 277 which exhibit the behavior described in 278 [I-D.yourtchenko-ipv6-disable-ipv4-proxyarp], this also means an 279 increase in the broadcast ARP traffic, which may be undesirable. 281 PROBLEM 14: IPv6-only hosts are unable to access resources identified 282 by IPv4 address literals. 284 8. Managing Router Identifiers 286 IPv4 addresses are often conventionally chosen to number a router ID, 287 which is used to identify a system running a specific protocol. The 288 common practice of tying an ID to an IPv4 address gives much 289 operational convenience. A human-readable ID is easy for network 290 operators to deal with, and it can be auto-configured, saving the 291 work of planning and assignment. It is also helpful to quickly 292 perform diagnosis and troubleshooting, and easy to identify the 293 availability and location of the identified router. 295 PROBLEM 15: In an IPv6 only network, there is no IP address that can 296 be directly used to number a router ID. IDs have to be 297 planned individually to meet the uniqueness requirement. 298 Tying the ID directly to an IP address which yields 299 human-friendly, auto-configured ID that helps with 300 troubleshooting is not possible. 302 9. IANA Considerations 304 None. 306 10. Security Considerations 308 It is believed that none of the problems identified in this draft are 309 security issues. 311 11. Acknowledgements 313 Thanks in particular to Andrew Yourtchenko, Lee Howard, Nejc 314 Skoberne, and Wes George for their thorough reviews and comments. 316 Special thanks to Marc Blanchet who was the driving force behind this 317 work and to Jean-Philippe Dionne who helped with the initial version 318 of this document. 320 12. Informative References 322 [BBF.TR242] 323 Broadband Forum, "TR-242: IPv6 Transition Mechanisms for 324 Broadband Networks", August 2012. 326 [Huston2012] 327 Huston, G. and G. Michaelson, "RIPE 64: Analysing Dual 328 Stack Behaviour and IPv6 Quality", April 2012. 330 [I-D.fleischhauer-ipv4-addr-saving] 331 Fleischhauer, K. and O. Bonness, "On demand IPv4 address 332 provisioning in Dual-Stack PPP deployment scenarios", 333 draft-fleischhauer-ipv4-addr-saving-05 (work in progress), 334 September 2013. 336 [I-D.wing-behave-http-ip-address-literals] 337 Wing, D., "Coping with IP Address Literals in HTTP URIs 338 with IPv6/IPv4 Translators", draft-wing-behave-http-ip- 339 address-literals-02 (work in progress), March 2010. 341 [I-D.yourtchenko-ipv6-disable-ipv4-proxyarp] 342 Yourtchenko, A. and O. Owen, "Disable "Proxy ARP for 343 Everything" on IPv4 link-local in the presence of IPv6 344 global address", draft-yourtchenko-ipv6-disable- 345 ipv4-proxyarp-00 (work in progress), May 2013. 347 [RFC2563] Troll, R., "DHCP Option to Disable Stateless Auto- 348 Configuration in IPv4 Clients", RFC 2563, May 1999. 350 [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. 351 Stevens, "Basic Socket Interface Extensions for IPv6", RFC 352 3493, February 2003. 354 [RFC3789] Nesser, P. and A. Bergstrom, "Introduction to the Survey 355 of IPv4 Addresses in Currently Deployed IETF Standards 356 Track and Experimental Documents", RFC 3789, June 2004. 358 [RFC3790] Mickles, C. and P. Nesser, "Survey of IPv4 Addresses in 359 Currently Deployed IETF Internet Area Standards Track and 360 Experimental Documents", RFC 3790, June 2004. 362 [RFC3791] Olvera, C. and P. Nesser, "Survey of IPv4 Addresses in 363 Currently Deployed IETF Routing Area Standards Track and 364 Experimental Documents", RFC 3791, June 2004. 366 [RFC3792] Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in 367 Currently Deployed IETF Security Area Standards Track and 368 Experimental Documents", RFC 3792, June 2004. 370 [RFC3793] Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in 371 Currently Deployed IETF Sub-IP Area Standards Track and 372 Experimental Documents", RFC 3793, June 2004. 374 [RFC3794] Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in 375 Currently Deployed IETF Transport Area Standards Track and 376 Experimental Documents", RFC 3794, June 2004. 378 [RFC3795] Sofia, R. and P. Nesser, "Survey of IPv4 Addresses in 379 Currently Deployed IETF Application Area Standards Track 380 and Experimental Documents", RFC 3795, June 2004. 382 [RFC3796] Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in 383 Currently Deployed IETF Operations & Management Area 384 Standards Track and Experimental Documents", RFC 3796, 385 June 2004. 387 [RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic 388 Configuration of IPv4 Link-Local Addresses", RFC 3927, May 389 2005. 391 [RFC4795] Aboba, B., Thaler, D., and L. Esibov, "Link-local 392 Multicast Name Resolution (LLMNR)", RFC 4795, January 393 2007. 395 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 396 Dual-Stack Hosts", RFC 6555, April 2012. 398 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 399 February 2013. 401 [Zeeb] "FreeBSD Snapshots without IPv4 support", 402 . 404 Appendix A. Solution Ideas 406 A.1. Remotely Disabling IPv4 408 A.1.1. Indicating that IPv4 connectivity is unavailable 410 One way to address these issues is to send a signal to a dual-stack 411 node that IPv4 connectivity is unavailable. Given that IPv4 shall be 412 off, the message must be delivered through IPv6. 414 A.1.2. Disabling IPv4 in the LAN 416 One way to address these issues is to send a signal to a dual-stack 417 node that auto-configuration of IPv4 addresses is undesirable, or 418 that direct IPv4 communication between nodes on the same link should 419 not take place. 421 A signalling protocol equivalent to the one from [RFC2563] but over 422 IPv6 is necessary, using either Router Advertisements or DHCPv6. 424 Furthermore, it could be useful to have L2 switches snoop this 425 signalling and automatically start filtering IPv4 traffic as a 426 consequence. 428 Finally, it could be useful to publish guidelines on how to safely 429 block IPv4 on an L2 switch. 431 A.2. Client Connection Establishment Behavior 433 Recommendations on client connection establishment behavior that 434 would facilitate IPv4 sunsetting would be appropriate. 436 A.3. Disabling IPv4 in Operating System and Applications 438 It would be useful for the IETF to provide guidelines to programmers 439 on how to avoid creating dependencies on IPv4, how to discover 440 existing dependencies, and how to eliminate them. It would be useful 441 if operating systems provide functions for users to see what 442 applications uses legacy IPv4-only APIs, so they can know it better 443 whether they can turn off IPv4 completely. Having programs and 444 operating systems that behave well in an IPv6-only environment is a 445 prerequisite for IPv4 sunsetting. 447 A.4. Managing Router Identifiers 449 Router IDs can be manually planned, possibly with some hierarchy or 450 design rule, or can be created automatically. A simple way of 451 automatic creation is to generate pseudo-random numbers, and one can 452 use another source of data such as the clock time at boot or 453 configuration time to provide additional entropy during the 454 generation of unique IDs. Another way is to hash an IPv6 address 455 down to a value as ID. The hash algorithm is supposed to be known 456 and the same across the domain. Since typically the number of 457 routers in a domain is far smaller than the value range of IDs, the 458 hashed IDs are hardly likely to conflict with each other, as long as 459 the hash algorithm is not designed too badly. It is necessary to be 460 able to override the automatically created value, and desirable if 461 the mechanism is provided by the system implementation. 463 If the ID is created from IPv6 address, e.g. by hashing from an IPv6 464 address, then naturally it has relationship with the address. If the 465 ID is created regardless of IP address, one way to build association 466 with IPv6 address is to embed the ID into an IPv6 address that is to 467 be configured on the router, e.g. use a /96 IPv6 prefix and append it 468 with a 32-bit long ID. One can also use some record keeping 469 mechanisms, e.g. text file, DNS or other provisioning system like 470 network management system to manage the IDs and mapping relations 471 with IPv6 addresses, though extra record keeping does introduce 472 additional work. 474 Authors' Addresses 476 Simon Perreault 477 Jive Communications 478 Quebec, QC 479 Canada 481 Email: sperreault@jive.com 483 Tina Tsou 484 Huawei Technologies (USA) 485 2330 Central Expressway 486 Santa Clara, CA 95050 487 USA 489 Phone: +1 408 330 4424 490 Email: tina.tsou.zouting@huawei.com 492 Cathy Zhou 493 Huawei Technologies 494 Huawei Industrial Base 495 Bantian, Shenzhen 496 China 498 Email: cathy.zhou@huawei.com 500 Peng Fan 501 China Mobile 502 32 Xuanwumen West Street 503 Beijing, Beijing 504 China 506 Email: fanp08@gmail.com