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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPv6 Operations L. Colitti 3 Internet-Draft V. Cerf 4 Intended status: Best Current Practice Google 5 Expires: August 15, 2016 S. Cheshire 6 D. Schinazi 7 Apple Inc. 8 February 12, 2016 10 Host address availability recommendations 11 draft-ietf-v6ops-host-addr-availability-05 13 Abstract 15 This document recommends that networks provide general-purpose end 16 hosts with multiple global IPv6 addresses when they attach, and 17 describes the benefits of and the options for doing so. 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 August 15, 2016. 36 Copyright Notice 38 Copyright (c) 2016 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 54 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 55 2. Common IPv6 deployment model . . . . . . . . . . . . . . . . 3 56 3. Benefits of providing multiple addresses . . . . . . . . . . 3 57 4. Problems with restricting the number of addresses per host . 4 58 5. Overcoming limits using Network Address Translation . . . . . 5 59 6. Options for providing more than one address . . . . . . . . . 6 60 7. Number of addresses required . . . . . . . . . . . . . . . . 7 61 8. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 8 62 9. Operational considerations . . . . . . . . . . . . . . . . . 8 63 9.1. Stateful addressing and host tracking . . . . . . . . . . 8 64 9.2. Address space management . . . . . . . . . . . . . . . . 9 65 9.3. Addressing link layer scalability issues via IP routing . 10 66 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 67 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 68 12. Security Considerations . . . . . . . . . . . . . . . . . . . 10 69 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 70 13.1. Normative References . . . . . . . . . . . . . . . . . . 11 71 13.2. Informative References . . . . . . . . . . . . . . . . . 11 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 74 1. Introduction 76 In most aspects, the IPv6 protocol is very similar to IPv4. This 77 similarity can create a tendency to think of IPv6 as 128-bit IPv4, 78 and thus lead network designers and operators to apply identical 79 configurations and operational practices to both. This is generally 80 a good thing because it eases the transition to IPv6 and the 81 operation of dual-stack networks. However, in some areas it can lead 82 to carrying over IPv4 practices that are not appropriate in IPv6 due 83 to significant differences between the protocols. 85 One such area is IP addressing, particularly IP addressing of hosts. 86 This is substantially different because unlike IPv4 addresses, IPv6 87 addresses are not a scarce resource. In IPv6, each link has a 88 virtually unlimited amount of address space [RFC7421]. Thus, unlike 89 IPv4, IPv6 networks are not forced by address availability 90 considerations to provide only one address per host. On the other 91 hand, providing multiple addresses has many benefits including 92 application functionality and simplicity, privacy, future 93 applications, and the ability to deploy the Internet without the use 94 of NAT. Providing only one IPv6 address per host negates these 95 benefits. 97 This document describes the benefits of providing multiple addresses 98 per host and the problems with not doing so. It recommends that 99 networks provide general-purpose end hosts with multiple global 100 addresses when they attach, and lists current options for doing so. 101 It does not specify any changes to protocols or host behavior. 103 1.1. Requirements Language 105 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 106 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 107 "OPTIONAL" in this document are to be interpreted as described in 108 "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119]. 110 2. Common IPv6 deployment model 112 IPv6 is designed to support multiple addresses, including multiple 113 global addresses, per interface ([RFC4291] section 2.1, [RFC6434] 114 section 5.9.4). Today, many general-purpose IPv6 hosts are 115 configured with three or more addresses per interface: a link-local 116 address, a stable address (e.g., using EUI-64 or Opaque Interface 117 Identifiers [RFC7217]), one or more privacy addresses [RFC4941], and 118 possibly one or more temporary or non-temporary addresses obtained 119 using DHCPv6 [RFC3315]. 121 In most general-purpose IPv6 networks, including all 3GPP networks 122 ([RFC6459] section 5.2) and Ethernet and Wi-Fi networks using SLAAC 123 [RFC4862], IPv6 hosts have the ability to configure additional IPv6 124 addresses from the link prefix(es) without explicit requests to the 125 network. 127 3. Benefits of providing multiple addresses 129 Today, there are many host functions that require more than one IP 130 address to be available to the host: 132 o Privacy addressing to prevent tracking by off-network hosts 133 [RFC4941]. 135 o Multiple processors inside the same device. For example, in many 136 mobile devices both the application processor and baseband 137 processor need to communicate with the network, particularly for 138 recent technologies like ePDG. 140 o Extending the network (e.g., "tethering"). 142 o Running virtual machines on hosts. 144 o Translation-based transition technologies such as 464XLAT 145 [RFC6877] that provide IPv4 over IPv6. Some of these require the 146 availability of a dedicated IPv6 address in order to determine 147 whether inbound packets are translated or native ([RFC6877] 148 section 6.3). 150 o ILA ("Identifier-locator addressing") [I-D.herbert-nvo3-ila]. 152 o Future applications (e.g., per-application IPv6 addresses [TARP]). 154 Examples of how the availability of multiple addresses per host has 155 already allowed substantial deployment of new applications without 156 explicit requests to the network are: 158 o 464XLAT. 464XLAT is usually deployed within a particular network, 159 and in this model the operator can ensure that the network is 160 appropriately configured to provide the CLAT with the additional 161 IPv6 address it needs to implement 464XLAT. However, there are 162 deployments where the PLAT (i.e., NAT64) is provided as a service 163 by a different network, without the knowledge or cooperation of 164 the residential ISP (e.g., the IPv6v4 Exchange Service 165 ). This type of 166 deployment is only possible because those residential ISPs provide 167 multiple IP addresses to their users, and thus those users can 168 freely obtain the extra IPv6 address required to run 464XLAT. 170 o /64 sharing [RFC7278]. When the topology supports it, this is a 171 way to provide IPv6 tethering without needing to wait for network 172 operators to deploy DHCPv6 PD, which is only available in 3GPP 173 release 10 ([RFC6459] section 5.3). 175 4. Problems with restricting the number of addresses per host 177 Providing a restricted number of addresses per host implies that 178 functions that require multiple addresses will either be unavailable 179 (e.g., if the network provides only one IPv6 address per host, or if 180 the host has reached the limit of the number of addresses available), 181 or that the functions will only be available after an explicit 182 request to the network is granted. The necessity of explicit 183 requests has the following drawbacks: 185 o Increased latency, because a provisioning operation, and possibly 186 human intervention with an update to the service level agreement, 187 must complete before the functionality is available. 189 o Uncertainty, because it is not known in advance if a particular 190 operation function will be available. 192 o Complexity, because implementations need to deal with failures and 193 somehow present them to the user. Failures may manifest as 194 timeouts, which may be slow and frustrating to users. 196 o Increased load on the network's provisioning servers. 198 Some operators may desire to configure their networks to limit the 199 number of IPv6 addresses per host. Reasons might include hardware 200 limitations (e.g., TCAM or neighbor cache table size constraints), 201 business models (e.g., a desire to charge the network's users on a 202 per-device basis), or operational consistency with IPv4 (e.g., an IP 203 address management system that only supports one address per host). 204 However, hardware limitations are expected to ease over time, and an 205 attempt to generate additional revenue by charging per device may 206 prove counterproductive if customers respond (as they did with IPv4) 207 by using NAT, which results in no additional revenue, but leads to 208 more operational problems and higher support costs. 210 5. Overcoming limits using Network Address Translation 212 These limits can mostly be overcome by end hosts by using NAT, and 213 indeed in IPv4 most of these functions are provided by using NAT on 214 the host. Thus, the limits could be overcome in IPv6 as well by 215 implementing NAT66 on the host. 217 Unfortunately NAT has well-known drawbacks. For example, it causes 218 application complexity due to the need to implement NAT traversal. 219 It hinders development of new applications. On mobile devices, it 220 reduces battery life due to the necessity of frequent keepalives, 221 particularly for UDP. Applications using UDP that need to work on 222 most of the Internet are forced to send keepalives at least every 30 223 seconds . For example, the QUIC protocol uses a 15-second keepalive 225 [I-D.tsvwg-quic-protocol]. Other drawbacks of NAT are well known and 226 documented [RFC2993]. While IPv4 NAT is inevitable due to the 227 limited amount of IPv4 space available, that argument does not apply 228 to IPv6. Guidance from the IAB is that deployment of IPv6 NAT is not 229 desirable [RFC5902]. 231 The desire to overcome the problems listed in Section 4 without 232 disabling any features has resulted in developers implementing IPv6 233 NAT. There are fully-stateful address+port NAT66 implementations in 234 client operating systems today: for example, Linux has supported 235 NAT66 since late 2012 . A popular software 237 hypervisor also recently implemented NAT66 to work around these 238 issues . Wide 239 deployment of networks that provide a restricted number of addresses 240 will cause proliferation of NAT66 implementations. 242 This is not a desirable outcome. It is not desirable for users 243 because they may experience application brittleness. It is likely 244 not desirable for network operators either, as they may suffer higher 245 support costs, and even when the decision to provide only one IPv6 246 address per device is dictated by the network's business model, there 247 may be little in the way of incremental revenue, because devices can 248 share their IPv6 address with other devices. Finally, it is not 249 desirable for operating system manufacturers and application 250 developers, who will have to build more complexity, lengthening 251 development time and/or reducing the time spent on other features. 253 Indeed, it could be argued that the main reason for deploying IPv6, 254 instead of continuing to scale the Internet using only IPv4 and 255 large-scale NAT44, is because doing so can provide all the hosts on 256 the planet with end-to-end connectivity that is constrained not by 257 accidental technical limitations, but only by intentional security 258 policies. 260 6. Options for providing more than one address 262 Multiple IPv6 addresses can be provided in the following ways: 264 o Using Stateless Address Autoconfiguration [RFC4862]. SLAAC allows 265 hosts to create global IPv6 addresses on demand by simply forming 266 new addresses from the global prefix(es) assigned to the link. 267 Typically, SLAAC is used on shared links, but it is also possible 268 to use SLAAC while providing a dedicated /64 prefix to each host. 269 This is the case, for example, if the host is connected via a 270 point-to-point link such as in 3GPP networks, on a network where 271 each host has its own dedicated VLAN, or on a wireless network 272 where every MAC address is placed in its own broadcast domain. 274 o Using stateful DHCPv6 address assignment [RFC3315]. Most DHCPv6 275 clients only ask for one non-temporary address, but the protocol 276 allows requesting multiple temporary and even multiple non- 277 temporary addresses, and the server could choose to provide 278 multiple addresses. It is also technically possible for a client 279 to request additional addresses using a different DUID, though the 280 DHCPv6 specification implies that this is not expected behavior 281 ([RFC3315] section 9). The DHCPv6 server will decide whether to 282 grant or reject the request based on information about the client, 283 including its DUID, MAC address, and so on. The number of IPv6 284 addresses that can be provided in a single DHCPv6 packet is 285 approximately 30. 287 o DHCPv6 prefix delegation [RFC3633]. DHCPv6 PD allows the client 288 to request and be delegated a prefix, from which it can 289 autonomously form other addresses. If the prefix is shorter than 290 /64, it can be divided into multiple subnets which can be further 291 delegated to downstream clients. If the prefix is a /64, it can 292 be extended via L2 bridging, ND proxying [RFC4389] or /64 sharing 293 [RFC7278], but it cannot be further subdivided, as a prefix longer 294 than /64 is outside the current IPv6 specifications [RFC7421]. 295 While [RFC3633] assumes that the DHCPv6 client is a router, DHCPv6 296 PD itself does not require that the client forward IPv6 packets 297 not addressed to itself, and thus does not require that the client 298 be an IPv6 router as defined in [RFC2460]. 300 +--------------------------+-------+-------------+--------+---------+ 301 | | SLAAC | DHCPv6 | DHCPv6 | DHCPv4 | 302 | | | IA_NA / | PD | | 303 | | | IA_TA | | | 304 +--------------------------+-------+-------------+--------+---------+ 305 | Extend network | Yes | No | Yes | Yes | 306 | | | | | (NAT44) | 307 | "Unlimited" endpoints | Yes* | Yes* | No | No | 308 | Stateful, request-based | No | Yes | Yes | Yes | 309 | Immune to layer 3 on- | No | Yes | Yes | Yes | 310 | link resource exhaustion | | | | | 311 | attacks | | | | | 312 +--------------------------+-------+-------------+--------+---------+ 314 [*] Subject to network limitations, e.g., ND cache entry size limits. 316 Table 1: Comparison of multiple address assignment options 318 7. Number of addresses required 320 If we itemize the use cases from section Section 3, we can estimate 321 the number of addresses currently used in normal operations. In 322 typical implementations, privacy addresses use up to 8 addresses - 323 one per day ([RFC4941] section 3.5). Current mobile devices may 324 typically support 8 clients, with each one requiring one or more 325 addresses. A client might choose to run several virtual machines. 326 Current implementations of 464XLAT require use of a separate address. 327 Some devices require another address for their baseband chip. Even a 328 host performing just a few of these functions simultaneously might 329 need on the order of 20 addresses at the same time. Future 330 applications designed to use an address per application or even per 331 resource will require many more. These will not function on networks 332 that enforce a hard limit on the number of addresses provided to 333 hosts. 335 8. Recommendations 337 In order to avoid the problems described above, and preserve the 338 Internet's ability to support new applications that use more than one 339 IPv6 address, it is RECOMMENDED that IPv6 network deployments provide 340 multiple IPv6 addresses from each prefix to general-purpose hosts. 341 To support future use cases, it is RECOMMENDED to not impose a hard 342 limit on the size of the address pool assigned to a host. 343 Particularly, it is NOT RECOMMENDED to limit a host to only one IPv6 344 address per prefix. 346 Due to the drawbacks imposed by requiring explicit requests for 347 address space (see section Section 4), it is RECOMMENDED that the 348 network give the host the ability to use new addresses without 349 requiring explicit requests. This can be achieved either by allowing 350 the host to form new addresses autonomously (e.g., via SLAAC), or by 351 providing the host with a dedicated /64 prefix. The prefix MAY be 352 provided using DHCPv6 PD, SLAAC with per-device VLANs, or any other 353 means. 355 Using stateful address assignment (DHCPv6 IA_NA or IA_TA) to provide 356 multiple addresses when the host connects (e.g. the approximately 30 357 addresses that can fit into a single packet) would accommodate 358 current clients, but sets a limit on the number of addresses 359 available to hosts when they attach and would limit the development 360 of future applications. 362 9. Operational considerations 364 9.1. Stateful addressing and host tracking 366 Some network operators - often operators of networks that provide 367 services to third parties such as university campus networks - are 368 required to track which IP addresses are assigned to which hosts on 369 their network. Maintaining persistent logs that map user IP 370 addresses and timestamps to hardware identifiers such as MAC 371 addresses may be used to avoid liability for copyright infringement 372 or other illegal activity. 374 It is worth noting that this requirement can be met without using 375 DHCPv6 address assignment. For example, it is possible to maintain 376 these mappings by monitoring IPv6 neighbor table: routers typically 377 allow periodic dumps of the neighbor cache via SNMP or other means, 378 and many can be configured to log every change to the neighbor cache. 379 Using SLAAC with a dedicated /64 prefix simplifies tracking, as it 380 does not require logging each address formed by the host, but only 381 the prefix assigned to the host when it attaches to the network. 382 Similarly, providing address space using DHCPv6 PD has the same 383 tracking properties as DHCPv6 address assignment, but allows the 384 network to provide unrestricted address space. 386 Many large enterprise networks, including the enterprise networks of 387 the authors' employers, are fully dual-stack and implement address 388 monitoring without using or supporting DHCPv6. The authors are 389 directly aware of several other networks that operate in this way, 390 including Universities of Loughborough, Minnesota, Reading, 391 Southampton, Wisconsin and Imperial College London. 393 It should also be noted that using DHCPv6 address assignment does not 394 ensure that the network can reliably track the IPv6 addresses used by 395 hosts. On any shared network without L2 edge port security, hosts 396 are able to choose their own addresses regardless of what address 397 provisioning methodology is in use. The only way to restrict the 398 addresses used by hosts is to use layer 2 security mechanisms that 399 enforce that particular IPv6 addresses are used by particular link- 400 layer addresses (for example, SAVI [RFC7039]). If those mechanisms 401 are available, it is possible to use them to provide tracking; this 402 form of tracking is more secure and reliable than server logs because 403 it operates independently of how addresses are allocated. Finally, 404 tracking address information via DHCPv6 server logs is likely to 405 become decreasingly viable due to ongoing efforts to improve the 406 privacy of DHCPv6 [I-D.ietf-dhc-anonymity-profile]. 408 9.2. Address space management 410 In IPv4, all but the world's largest networks can be addressed using 411 private space [RFC1918], with each host receiving one IPv4 address. 412 Many networks can be numbered in 192.168.0.0/16 which has roughly 64k 413 addresses. In IPv6, that is equivalent to a /48, with each of 64k 414 hosts receiving a /64 prefix. Under current RIR policies, a /48 is 415 easy to obtain for an enterprise network. 417 Networks that need a bigger block of private space use 10.0.0.0/8, 418 which has roughly 16 million addresses. In IPv6, that is equivalent 419 to a /40, with each host receiving /64 prefix. Enterprises of such 420 size can easily obtain a /40 under current RIR policies. Aggregation 421 and routing can be equivalent to IPv4, with /64 prefixes being 422 aggregated into the as many prefixes of length /64 - n as IPv4 423 addresses are aggregated into prefixes of length /32 - n. 425 Currently, residential users typically receive one IPv4 address and a 426 /48, /56 or /60 IPv6 prefix. While such networks do not provide 427 enough space to assign a /64 per host, such networks almost 428 universally use SLAAC, and thus do not pose any particular limit to 429 the number of addresses hosts can use. 431 Unlike IPv4 where addresses came at a premium, in all these networks, 432 there is enough IPv6 address space to supply clients with multiple 433 IPv6 addresses. 435 9.3. Addressing link layer scalability issues via IP routing 437 The number of IPv6 addresses on a link has direct impact for 438 networking infrastructure nodes (routers, switches) and other nodes 439 on the link. Setting aside exhaustion attacks via Layer 2 address 440 spoofing, every (Layer 2, IP) address pair impacts networking 441 hardware requirements in terms of memory, MLD snooping, solicited 442 node multicast groups, etc. Many of these costs are incurred by 443 neighboring hosts. 445 Hosts on such networks that create unreasonable numbers of addresses 446 risk impairing network connectivity for themselves and other hosts on 447 the network, and in extreme cases (e.g., hundreds or thousands of 448 addresses) may even find their network access restricted by denial- 449 of-service protection mechanisms. 451 We expect these scaling limitations to change over time as hardware 452 and applications evolve. However, switching to a dedicated /64 453 prefix per host can resolve these scaling limitations, with only one 454 routing entry and one ND cache entry per host on the network. If the 455 host is aware that the prefix is dedicated (e.g., if it was provided 456 via DHCPv6 PD and not SLAAC), it is possible for the host to assign 457 IPv6 addresses from this prefix to an internal interface such as a 458 loopback interface. This obviates the need to perform Neighbor 459 Discovery and Duplicate Address Detection on the network interface 460 for these addresses, reducing network traffic. 462 10. Acknowledgements 464 The authors thank Tore Anderson, Brian Carpenter, David Farmer, 465 Wesley George, Erik Kline, Shucheng (Will) Liu, Dieter Siegmund, Mark 466 Smith, Sander Steffann, Fred Templin and James Woodyatt for their 467 input and contributions. 469 11. IANA Considerations 471 This memo includes no request to IANA. 473 12. Security Considerations 475 None so far. 477 13. References 479 13.1. Normative References 481 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 482 Requirement Levels", BCP 14, RFC 2119, 483 DOI 10.17487/RFC2119, March 1997, 484 . 486 13.2. Informative References 488 [I-D.herbert-nvo3-ila] 489 Herbert, T., "Identifier-locator addressing for network 490 virtualization", draft-herbert-nvo3-ila-01 (work in 491 progress), October 2015. 493 [I-D.ietf-dhc-anonymity-profile] 494 Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity 495 profile for DHCP clients", draft-ietf-dhc-anonymity- 496 profile-06 (work in progress), January 2016. 498 [I-D.tsvwg-quic-protocol] 499 Hamilton, R., Iyengar, J., Swett, I., and A. Wilk, "QUIC: 500 A UDP-Based Secure and Reliable Transport for HTTP/2", 501 draft-tsvwg-quic-protocol-02 (work in progress), January 502 2016. 504 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 505 and E. Lear, "Address Allocation for Private Internets", 506 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 507 . 509 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 510 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 511 December 1998, . 513 [RFC2993] Hain, T., "Architectural Implications of NAT", RFC 2993, 514 DOI 10.17487/RFC2993, November 2000, 515 . 517 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 518 C., and M. Carney, "Dynamic Host Configuration Protocol 519 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 520 2003, . 522 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 523 Host Configuration Protocol (DHCP) version 6", RFC 3633, 524 DOI 10.17487/RFC3633, December 2003, 525 . 527 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 528 Architecture", RFC 4291, DOI 10.17487/RFC4291, February 529 2006, . 531 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 532 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 533 2006, . 535 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 536 Address Autoconfiguration", RFC 4862, 537 DOI 10.17487/RFC4862, September 2007, 538 . 540 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 541 Extensions for Stateless Address Autoconfiguration in 542 IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, 543 . 545 [RFC5902] Thaler, D., Zhang, L., and G. Lebovitz, "IAB Thoughts on 546 IPv6 Network Address Translation", RFC 5902, 547 DOI 10.17487/RFC5902, July 2010, 548 . 550 [RFC6434] Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node 551 Requirements", RFC 6434, DOI 10.17487/RFC6434, December 552 2011, . 554 [RFC6459] Korhonen, J., Ed., Soininen, J., Patil, B., Savolainen, 555 T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation 556 Partnership Project (3GPP) Evolved Packet System (EPS)", 557 RFC 6459, DOI 10.17487/RFC6459, January 2012, 558 . 560 [RFC6877] Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT: 561 Combination of Stateful and Stateless Translation", 562 RFC 6877, DOI 10.17487/RFC6877, April 2013, 563 . 565 [RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed., 566 "Source Address Validation Improvement (SAVI) Framework", 567 RFC 7039, DOI 10.17487/RFC7039, October 2013, 568 . 570 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque 571 Interface Identifiers with IPv6 Stateless Address 572 Autoconfiguration (SLAAC)", RFC 7217, 573 DOI 10.17487/RFC7217, April 2014, 574 . 576 [RFC7278] Byrne, C., Drown, D., and A. Vizdal, "Extending an IPv6 577 /64 Prefix from a Third Generation Partnership Project 578 (3GPP) Mobile Interface to a LAN Link", RFC 7278, 579 DOI 10.17487/RFC7278, June 2014, 580 . 582 [RFC7421] Carpenter, B., Ed., Chown, T., Gont, F., Jiang, S., 583 Petrescu, A., and A. Yourtchenko, "Analysis of the 64-bit 584 Boundary in IPv6 Addressing", RFC 7421, 585 DOI 10.17487/RFC7421, January 2015, 586 . 588 [TARP] Gleitz, PM. and SM. Bellovin, "Transient Addressing for 589 Related Processes: Improved Firewalling by Using IPv6 and 590 Multiple Addresses per Host", August 2001. 592 Authors' Addresses 594 Lorenzo Colitti 595 Google 596 Roppongi 6-10-1 597 Minato, Tokyo 106-6126 598 JP 600 Email: lorenzo@google.com 602 Vint Cerf 603 Google 604 1875 Explorer St 605 10th Floor 606 Reston, VA 20190 607 US 609 Email: vint@google.com 610 Stuart Cheshire 611 Apple Inc. 612 1 Infinite Loop 613 Cupertino, CA 95014 614 US 616 Email: cheshire@apple.com 618 David Schinazi 619 Apple Inc. 620 1 Infinite Loop 621 Cupertino, CA 95014 622 US 624 Email: dschinazi@apple.com