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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 INTERNET-DRAFT R. Hinden, Nokia 2 February 12, 2004 B. Haberman, Caspian 4 Unique Local IPv6 Unicast Addresses 6 8 Status of this Memo 10 This document is an Internet-Draft and is in full conformance with 11 all provisions of Section 10 of RFC2026. Internet-Drafts are working 12 documents of the Internet Engineering Task Force (IETF), its areas, 13 and its working groups. Note that other groups may also distribute 14 working documents as Internet-Drafts. 16 Internet-Drafts are draft documents valid for a maximum of six months 17 and may be updated, replaced, or obsoleted by other documents at any 18 time. It is inappropriate to use Internet-Drafts as reference 19 material or to cite them other than as "work in progress." 21 To view the list Internet-Draft Shadow Directories, see 22 http://www.ietf.org/shadow.html. 24 This internet draft expires on August 17, 2004. 26 Abstract 28 This document defines an IPv6 unicast address format that is globally 29 unique and is intended for local communications, usually inside of a 30 site. They are not expected to be routable on the global Internet. 32 Table of Contents 34 1.0 Introduction....................................................2 35 2.0 Acknowledgments.................................................3 36 3.0 Local IPv6 Unicast Addresses....................................3 37 3.1 Format..........................................................3 38 3.1.1 Background....................................................4 39 3.2 Global ID.......................................................4 40 3.2.1 Centrally Assigned Global IDs.................................5 41 3.2.2 Locally Assigned Global IDs...................................6 42 3.2.3 Sample Code for Pseudo-Random Global ID Algorithm.............6 43 3.2.4 Analysis of the Uniqueness of Global IDs......................7 44 3.3 Scope Definition................................................8 45 4.0 Routing.........................................................8 46 5.0 Renumbering and Site Merging....................................8 47 6.0 Site Border Router and Firewall Packet Filtering................9 48 7.0 DNS Issues......................................................9 49 8.0 Application and Higher Level Protocol Issues...................10 50 9.0 Use of Local IPv6 Addresses for Local Communications...........10 51 10.0 Use of Local IPv6 Addresses with VPNs.........................11 52 11.0 Advantages and Disadvantages..................................12 53 12.0 Security Considerations.......................................12 54 13.0 IANA Considerations...........................................12 55 14.0 References....................................................13 56 14.1 Normative References..........................................13 57 14.2 Informative References........................................13 58 15.0 Authors' Addresses............................................14 59 16.0 Change Log....................................................15 61 1.0 Introduction 63 This document defines an IPv6 unicast address format that is globally 64 unique and is intended for local communications [IPV6]. These 65 addresses are called Unique Local IPv6 Unicast Addresses and are 66 abbreviated in this document as Local IPv6 addresses. They are not 67 expected to be routable on the global Internet. They are routable 68 inside of a more limited area such as a site. They may also be 69 routed between a limited set of sites. 71 Local IPv6 unicast addresses have the following characteristics: 73 - Globally unique prefix. 74 - Well known prefix to allow for easy filtering at site 75 boundaries. 76 - Allows sites to be combined or privately interconnected without 77 creating any address conflicts or require renumbering of 78 interfaces using these prefixes. 79 - Internet Service Provider independent and can be used for 80 communications inside of a site without having any permanent or 81 intermittent Internet connectivity. 82 - If accidentally leaked outside of a site via routing or DNS, 83 there is no conflict with any other addresses. 84 - In practice, applications may treat these addresses like global 85 scoped addresses. 87 This document defines the format of Local IPv6 addresses, how to 88 allocate them, and usage considerations including routing, site 89 border routers, DNS, application support, VPN usage, and guidelines 90 for how to use for local communication inside a site. 92 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 93 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 94 document are to be interpreted as described in [RFC 2119]. 96 2.0 Acknowledgments 98 The underlying idea of creating Local IPv6 addresses described in 99 this document been proposed a number of times by a variety of people. 100 The authors of this draft do not claim exclusive credit. Credit goes 101 to Brian Carpenter, Christian Huitema, Aidan Williams, Andrew White, 102 Charlie Perkins, and many others. The authors would also like to 103 thank Brian Carpenter, Charlie Perkins, Harald Alvestrand, Keith 104 Moore, Margaret Wasserman, Shannon Behrens, Alan Beard, Hans Kruse, 105 Geoff Huston, Pekka Savola, and Christian Huitema for their comments 106 and suggestions on this document. 108 3.0 Local IPv6 Unicast Addresses 110 3.1 Format 112 The Local IPv6 addresses are created using a centrally allocated 113 global ID. They have the following format: 115 | 7 bits | 41 bits | 16 bits | 64 bits | 116 +--------+------------+-----------+-----------------------------+ 117 | prefix | global ID | subnet ID | interface ID | 118 +--------+------------+-----------+-----------------------------+ 120 Where: 122 prefix FC00::/7 prefix to identify Local IPv6 unicast 123 addresses. 125 global ID 41-bit global identifier used to create a 126 globally unique prefix. See section 3.2 for 127 additional information. 129 subnet ID 16-bit subnet ID is an identifier of a subnet 130 within the site. 132 interface ID 64-bit interface ID as defined in [ADDARCH]. 134 3.1.1 Background 136 There were a range of choices available when choosing the size of the 137 prefix and global ID field length. There is a direct tradeoff 138 between having a global ID field large enough to support foreseeable 139 future growth and not using too much of the IPv6 address space 140 needlessly. A reasonable way of evaluating a specific field length 141 is to compare it to a projected 2050 world population of 9.3 billion 142 [POPUL] and the number of resulting /48 prefixes per person. A range 143 of prefix choices is shown in the following table: 145 Prefix Global ID Number of Prefixes % of IPv6 146 Length /48 Prefixes per Person Address Space 148 /11 37 137,438,953,472 15 0.049% 149 /10 38 274,877,906,944 30 0.098% 150 /9 39 549,755,813,888 59 0.195% 151 /8 40 1,099,511,627,776 118 0.391% 152 /7 41 2,199,023,255,552 236 0.781% 153 /6 42 4,398,046,511,104 473 1.563% 155 A very high utilization ratio of these allocations can be assumed 156 because the global ID field does not require internal structure, and 157 there is no reason to be able to aggregate the prefixes. 159 The authors believe that a /7 prefix resulting in a 41 bit global ID 160 is a good choice. It provides for a large number of assignments 161 (i.e., 2.2 trillion) and at the same time uses less than .8% of the 162 total IPv6 address space. It is unlikely that this space will be 163 exhausted. If more than this were to be needed, then additional IPv6 164 address space could be allocated for this purpose. 166 3.2 Global ID 168 The allocation of global IDs should be pseudo-random [RANDOM]. They 169 should not be assigned sequentially or with well known numbers. This 170 is to ensure that there is not any relationship between allocations 171 and to help clarify that these prefixes are not intended to be routed 172 globally. Specifically, these prefixes are designed to not 173 aggregate. 175 There are two ways to allocate Global IDs. These are centrally by a 176 allocation authority and locally by the site. The Global ID is split 177 into two parts for each type of allocation. The prefixes for each 178 type are: 180 FC00::/8 Centrally assigned 181 FD00::/8 Locally assigned 183 Each results in a 40-bit space to allocate. 185 Two assignment methods are included because they have different 186 properties. The centrally assigned global IDs are uniquely assigned 187 and the assignments can be escrowed to resolve any disputes regarding 188 duplicate assignments. The local assignments are self generated and 189 do not need any central coordination or assignment, but have a lower 190 (but still adequate) probability of being unique. It is expected 191 that large managed sites will prefer central assignments and small or 192 disconnected sites will prefer local assignments. It is recommended 193 that sites planning to use Local IPv6 addresses for extensive inter- 194 site communication, initially or as a future possibility, use a 195 centrally assigned prefix as there is no possibility of assignment 196 conflicts. Sites are free to choose either approach. 198 3.2.1 Centrally Assigned Global IDs 200 Centrally assigned global IDs MUST be generated with a pseudo-random 201 algorithm consistent with [RANDOM]. They should not be assigned 202 sequentially or by locality. This is to ensure that there is no 203 relationship between allocations and to help clarify that these 204 prefixes are not intended to be routed globally by eliminating the 205 possibility of aggregation. Specifically, these prefixes are 206 designed to not aggregate. 208 Global IDs should be assigned centrally by a single allocation 209 authority because they are pseudo-random and without any structure. 210 This is easiest to accomplish if there is a single source for the 211 assignments. 213 The requirements for centrally assigned global ID allocations are: 215 - Available to anyone in an unbiased manner. 216 - Permanent with no periodic fees. 217 - Allocation on a permanent basis, without any need for renewal 218 and without any procedure for de-allocation. 219 - Provide mechanisms that prevent hoarding of these allocations. 220 - The ownership of each individual allocation should be private, 221 but should be escrowed. 223 The allocation authority should permit allocations to be obtained 224 without having any sort of Internet connectivity. For example in 225 addition to web based registration they should support some methods 226 like telephone, postal mail, fax, etc. 228 The allocation service should include sufficient provisions to avoid 229 hoarding of numbers. This can be accomplished by various ways, for 230 example, requiring an exchange of documents, a verbal contact, or a 231 proof that the request is on behalf of a human rather than a machine. 232 The service may charge a small fee in order to cover its costs, but 233 the fee should be low enough to not create a barrier to anyone 234 needing one. The precise mechanisms should be decided by the 235 registration authority. 237 The ownership of the allocations is not needed to be public since the 238 resulting addresses are intended to be used for local communication. 239 It is escrowed to ensure there are no duplicate allocations and in 240 case it is needed in the future (e.g., to resolve duplicate 241 allocation disputes, or to support a change of the central allocation 242 authority). 244 Note, there are many possible ways of of creating an allocation 245 authority. It is important to keep in mind when reviewing 246 alternatives that the goal is to pick one that can do the job. It 247 doesn't have to be perfect, only good enough to do the job at hand. 249 This document directs the IANA, in section 13.0, to delegate the 250 FC00::/8 prefix to an allocation authority to allocate centrally 251 assigned /48 prefixes consistent with the requirements defined in 252 this section. 254 3.2.2 Locally Assigned Global IDs 256 Global IDs can also be generated locally by an individual site. This 257 makes it easy to get a prefix without the need to contact an 258 assignment authority or internet service provider. There is not as 259 high a degree of assurance that the prefix will not conflict with 260 another locally generated prefix, but the likelihood of conflict is 261 small. Sites that are not comfortable with this degree of 262 uncertainty should use a centrally assigned global ID. 264 Locally assigned global IDs MUST be generated with a pseudo-random 265 algorithm consistent with [RANDOM]. Section 3.2.3 describes a 266 suggested algorithm. It is important to ensure a reasonable 267 likelihood uniqueness that all sites generating a Global IDs use a 268 functionally similar algorithm. 270 3.2.3 Sample Code for Pseudo-Random Global ID Algorithm 272 The algorithm described below is intended to be used for centrally 273 and locally assigned Global IDs. In each case the resulting global 274 ID will be used in the appropriate prefix as defined in section 3.2. 276 1) Obtain the current time of day in 64-bit NTP format [NTP]. 277 2) Obtain an EUI-64 identifier from the system running this 278 algorithm. If an EUI-64 does not exist, one can be created from 279 a 48-bit MAC address as specified in [ADDARCH]. If an EUI-64 280 cannot be obtained or created, a suitably unique identifier, 281 local to the node, should be used (e.g. system serial number). 282 3) Concatenate the time of day with the system-specific identifier 283 creating a key. 284 4) Compute an MD5 digest on the key as specified in [MD5DIG]. 285 5) Use the least significant 40 bits as the Global ID. 287 This algorithm will result in a global ID that is reasonably unique 288 and can be used as a Global ID. 290 3.2.4 Analysis of the Uniqueness of Global IDs 292 The selection of a pseudo random global ID is similar to the 293 selection of an SSRC identifier in RTP/RTCP defined in section 8.1 of 294 [RTP]. This analysis is adapted from that document. 296 Since the global ID is chosen randomly, it is possible that two or 297 more networks that have an inter-network connection using globally- 298 unique local addresses will chose the same global ID. The 299 probability of collision can be approximated based on the number of 300 connections between networks using globally-unique local addresses 301 and the length of the ID (40 bits). The formula 303 P = 1 - exp(-N**2 / 2**(L+1)) 305 approximates the probability of collision (where N is the number 306 connections and L is the length of the global ID). 308 The following table shows the probability of a collision for a range 309 of connections using a 40 bit global ID field. 311 Connections Probability of Collision 313 2 1.81*10^-12 314 10 4.54*10^-11 315 100 4.54*10^-09 316 1000 4.54*10^-07 317 10000 4.54*10^-05 319 Based on this analysis the uniqueness of locally generated global IDs 320 is adequate for sites planning a small to moderate amount of inter- 321 site communication using locally generated global IDs. Sites 322 planning more extensive inter-site communication should consider 323 using the centrally assigned global ID. 325 3.3 Scope Definition 327 By default, the scope of these addresses is global. That is, they 328 are not limited by ambiguity like the site-local addresses defined in 329 [ADDARCH]. Rather, these prefixes are globally unique, and as such, 330 their applicability is greater than site-local addresses. Their 331 limitation is in the routability of the prefixes, which is limited to 332 a site and any explicit routing agreements with other sites to 333 propagate them. Also, unlike site-locals, a site may have more than 334 one of these prefixes and use them at the same time. 336 4.0 Routing 338 Local IPv6 addresses are designed to be routed inside of a site in 339 the same manner as other types of unicast addresses. They can be 340 carried in any IPv6 routing protocol without any change. 342 It is expected that they would share the same subnet IDs with 343 provider based global unicast addresses if they were being used 344 concurrently [GLOBAL]. 346 Any router that is used between sites must be configured to filter 347 out any incoming or outgoing Local IPv6 unicast routes. The 348 exception to this is if specific /48 IPv6 local unicast routes have 349 been configured to allow for inter-site communication. 351 If BGP is being used at the site border with an ISP, the default BGP 352 configuration must be set to to keep any Local IPv6 address prefixes 353 from being advertised outside of the site or for these prefixes to be 354 learned from another site. The exception to this is if there are 355 specific /48 routes created for one or more Local IPv6 prefixes. 357 5.0 Renumbering and Site Merging 359 The use of Local IPv6 addresses in a site results in making 360 communication using these addresses independent of renumbering a 361 site's provider based global addresses. 363 When merging multiple sites none of the addresses created with these 364 prefixes need to be renumbered because all of the addresses are 365 unique. Routes for each specific prefix would have to be configured 366 to allow routing to work correctly between the formerly separate 367 sites. 369 6.0 Site Border Router and Firewall Packet Filtering 371 While no serious harm will be done if packets with these addresses 372 are sent outside of a site via a default route, it is recommended 373 that routers be configured by default to keep any packets with Local 374 IPv6 destination addresses from leaking outside of the site and to 375 keep any site prefixes from being advertised outside of their site. 377 Site border routers should install a "reject" route for the Local 378 IPv6 prefix FC00::/7. This will ensure that packets with Local IPv6 379 destination addresses will not be forwarded outside of the site via a 380 default route. Site border routers should respond with the 381 appropriate ICMPv6 Destination Unreachable message to inform the 382 source that the packet was not forwarded [ICMPV6]. This feedback is 383 important to avoid transport protocol timeouts. 385 Site border routers and firewalls should not forward any packets with 386 Local IPv6 source or destination addresses outside of the site unless 387 they have been explicitly configured with routing information about 388 other Local IPv6 prefixes. The default behavior of these devices 389 should be to install a "reject" route for these prefixes. Site 390 border routers should respond with the appropriate ICMPv6 Destination 391 Unreachable message to inform the source that the packet was not 392 forwarded. 394 Routers that maintain peering arrangements between Autonomous Systems 395 throughout the Internet should obey the recommendations for site 396 border routers unless configured otherwise. 398 7.0 DNS Issues 400 AAAA records for Local IPv6 addresses should not be installed in the 401 global DNS. They may be installed in a naming system local to the 402 site or kept separate from the global DNS. 404 If Local IPv6 address are configured in the global DNS, no harm is 405 done because they are unique and will not create any confusion. They 406 may not be reachable, but this is a property that is common to all 407 types of global IPv6 unicast addresses. 409 8.0 Application and Higher Level Protocol Issues 411 Application and other higher level protocols can treat Local IPv6 412 addresses in the same manner as other types of global unicast 413 addresses. No special handling is required. This type of addresses 414 may not be reachable, but that is no different from other types of 415 IPv6 global unicast addresses. Applications need to be able to 416 handle multiple addresses that may or may not be reachable any point 417 in time. In most cases this complexity should be hidden in APIs. 419 From a host's perspective this difference shows up as different 420 reachability than global unicast and could be handled by default that 421 way. In some cases it is better for nodes and applications to treat 422 them differently from global unicast addresses. A starting point 423 might be to give them preference over global unicast, but fall back 424 to global unicast if a particular destination is found to be 425 unreachable. Much of this behavior can be controlled by how they are 426 allocated to nodes and put into the DNS. However it is useful if a 427 host can have both types of addresses and use them appropriately. 429 Note that the address selection mechanisms of [ADDSEL], and in 430 particular the policy override mechanism replacing default address 431 selection, are expected to be used on a site where Local IPv6 432 addresses are configured. 434 9.0 Use of Local IPv6 Addresses for Local Communications 436 Local IPv6 addresses, like global scope unicast addresses, are only 437 assigned to nodes if their use has been enabled (via IPv6 address 438 autoconfiguration [ADDAUTO], DHCPv6 [DHCP6], or manually). They are 439 not created automatically the way that IPv6 link-local addresses are 440 and will not appear or be used unless they are purposely configured. 442 In order for hosts to autoconfigure Local IPv6 addresses, routers 443 have to be configured to advertise Local IPv6 /64 prefixes in router 444 advertisements, or a DHCPv6 server must have been configured to 445 assign them. In order for a node to learn the Local IPv6 address of 446 another node, the Local IPv6 address must have been installed in the 447 DNS or another naming system. For these reasons, it is straight 448 forward to control their usage in a site. 450 To limit the use of Local IPv6 addresses the following guidelines 451 apply: 453 - Nodes that are to only be reachable inside of a site: The local 454 DNS should be configured to only include the Local IPv6 455 addresses of these nodes. Nodes with only Local IPv6 addresses 456 must not be installed in the global DNS. 458 - Nodes that are to be limited to only communicate with other 459 nodes in the site: These nodes should be set to only 460 autoconfigure Local IPv6 addresses via [ADDAUTO] or to only 461 receive Local IPv6 addresses via [DHCP6]. Note: For the case 462 where both global and Local IPv6 prefixes are being advertised 463 on a subnet, this will require a switch in the devices to only 464 autoconfigure Local IPv6 addresses. 466 - Nodes that are to be reachable from inside of the site and from 467 outside of the site: The DNS should be configured to include 468 the global addresses of these nodes. The local DNS may be 469 configured to also include the Local IPv6 addresses of these 470 nodes. 472 - Nodes that can communicate with other nodes inside of the site 473 and outside of the site: These nodes should autoconfigure global 474 addresses via [ADDAUTO] or receive global address via [DHCP6]. 475 They may also obtain Local IPv6 addresses via the same 476 mechanisms. 478 10.0 Use of Local IPv6 Addresses with VPNs 480 Local IPv6 addresses can be used for inter-site Virtual Private 481 Networks (VPN) if appropriate routes are set up. Because the 482 addresses are unique these VPNs will work reliably and without the 483 need for translation. They have the additional property that they 484 will continue to work if the individual sites are renumbered or 485 merged. 487 11.0 Advantages and Disadvantages 489 11.1 Advantages 491 This approach has the following advantages: 493 - Provides Local IPv6 prefixes that can be used independently of 494 any provider based IPv6 unicast address allocations. This is 495 useful for sites not always connected to the Internet or sites 496 that wish to have a distinct prefix that can be used to localize 497 traffic inside of the site. 498 - Applications can treat these addresses in an identical manner as 499 any other type of global IPv6 unicast addresses. 500 - Sites can be merged without any renumbering of the Local IPv6 501 addresses. 503 - Sites can change their provider based IPv6 unicast address 504 without disrupting any communication using Local IPv6 addresses. 505 - Well known prefix that allows for easy filtering at site 506 boundary. 507 - Can be used for inter-site VPNs. 508 - If accidently leaked outside of a site via routing or DNS, there 509 is no conflict with any other addresses. 511 11.2 Disadvantages 513 This approach has the following disadvantages: 515 - Not possible to route Local IPv6 prefixes on the global Internet 516 with current routing technology. Consequentially, it is 517 necessary to have the default behavior of site border routers to 518 filter these addresses. 519 - There is a very low probability of non-unique locally assigned 520 global IDs being generated by the algorithm in section 3.2.3. 521 This risk can be ignored for all practical purposes, but it 522 leads to a theoretical risk of clashing address prefixes. 524 12.0 Security Considerations 526 Local IPv6 addresses do not provide any inherent security to the 527 nodes that use them. They may be used with filters at site 528 boundaries to keep Local IPv6 traffic inside of the site, but this is 529 no more or less secure than filtering any other type of global IPv6 530 unicast addresses. 532 Local IPv6 addresses do allow for address-based security mechanisms, 533 including IPSEC, across end to end VPN connections. 535 13.0 IANA Considerations 537 The IANA is instructed to allocate the FC00::/7 prefix for Unique 538 Local IPv6 unicast addresses. 540 The IANA is instructed to delegate, within a reasonable time, the 541 prefix FC00::/8 to an allocation authority for Unique Local IPv6 542 Unicast prefixes of length /48. This allocation authority shall 543 comply with the requirements described in section 3.2 of this 544 document, including in particular allocation on a permanent basis and 545 with sufficient provisions to avoid hoarding of numbers. If deemed 546 appropriate, the authority may also consist of multiple organizations 547 performing the authority duties. 549 14.0 References 551 14.1 Normative References 553 [ADDARCH] Hinden, R., S. Deering, S., "IP Version 6 Addressing 554 Architecture", RFC 3515, April 2003. 556 [GLOBAL] Hinden, R., S. Deering, E. Nordmark, "IPv6 Global Unicast 557 Address Format", RFC 3587, August 2003. 559 [ICMPV6] Conta, A., S. Deering, "Internet Control Message Protocol 560 (ICMPv6) for the Internet Protocol Version 6 (IPv6) 561 Specification", RFC2463, December 1998. 563 [IPV6] Deering, S., R. Hinden, "Internet Protocol, Version 6 564 (IPv6) Specification", RFC 2460, December 1998. 566 [MD5DIG] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, 567 April 1992. 569 [NTP] Mills, David L., "Network Time Protocol (Version 3) 570 Specification, Implementation and Analysis", RFC 1305, 571 March 1992. 573 [POPUL] Population Reference Bureau, "World Population Data Sheet 574 of the Population Reference Bureau 2002", August 2002. 576 [RANDOM] Eastlake, D. 3rd, S. Crocker, J. Schiller, "Randomness 577 Recommendations for Security", RFC 1750, December 1994. 579 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 580 Requirement Levels", RFC 2119, BCP14, March 1997. 582 14.2 Informative References 584 [ADDAUTO] Thomson, S., T. Narten, "IPv6 Stateless Address 585 Autoconfiguration", RFC 2462, December 1998. 587 [ADDSEL] Draves, R., "Default Address Selection for Internet 588 Protocol version 6 (IPv6)", RFC 3484, February 2003. 590 [DHCP6] Droms, R., et. al., "Dynamic Host Configuration Protocol 591 for IPv6 (DHCPv6)", RFC3315, July 2003. 593 [RTP] Schulzrinne, H., S. Casner, R. Frederick, V. Jacobson, 594 "RTP: A Transport Protocol for Real-Time Applications" 595 RFC3550, July 2003. 597 15.0 Authors' Addresses 599 Robert M. Hinden 600 Nokia 601 313 Fairchild Drive 602 Mountain View, CA 94043 603 USA 605 phone: +1 650 625-2004 606 email: bob.hinden@nokia.com 608 Brian Haberman 609 Caspian Networks 610 1 Park Drive, Suite 300 611 Research Triangle Park, NC 27709 612 USA 614 phone: +1-929-949-4828 615 email: brian@innovationslab.net 617 16.0 Change Log 619 Draft 621 o Removed requirement of a fee per central allocation and updated 622 IANA considerations to reflect this. Rewrote text to focus on 623 the requirement to avoid hoarding of allocations. 624 o Changed "filtering" and "black hole routes" to "reject" routes. 625 o Changed uppers case requirements (i.e., MUST, SHOULD, etc.) to 626 lower case in sections giving operational advice. 627 o Removed paragraph mentioning "Multicast DNS". 628 o Various editorial changes. 630 Draft 632 o Removed mention of 10 euro charge and changed text in section 633 3.2.1 and IANA considerations to restate the requirement for low 634 cost allocations and added specific requirement to prevent 635 hording. 636 o Added need to send ICMPv6 destination unreachable messages if 637 packets are filtered or dropped at site boundaries. 638 o Changed format section to list prefix sizes and definition, and 639 changed discussion of prefix sizes to new background section. 640 o Various editorial changes. 642 Draft 644 o Removed example of PIR as an example of an allocation authority 645 and clarified the text that the IANA should delegate the 646 centrally assigned prefix to an allocation authority. 647 o Changed sample code for generating pseudo random Global IDs to 648 not require any human input. Changes from using birthday to 649 unique token (e.g., EUI-64, serial number, etc.) available on 650 machine running the algorithm. 651 o Added a new section analyzing the uniqueness properties of the 652 pseudo random number algorithm. 653 o Added text to recommend that centrally assigned local addresses 654 be used for site planning extensive inter-site communication. 655 o Clarified that domain border routers should follow site border 656 router recommendations. 657 o Clarified that AAAA DNS records should not be installed in the 658 global DNS. 659 o Several editorial changes. 661 Draft 663 o Changed file name to become an IPv6 w.g. group document. 664 o Clarified language in Routing and Firewall sections. 666 o Several editorial changes. 668 Draft 670 o Changed title and name of addresses defined in this document to 671 "Unique Local IPv6 Unicast Addresses" with abbreviation of 672 "Local IPv6 addresses". 673 o Several editorial changes. 675 Draft 677 o Added section on scope definition and updated application 678 requirement section. 679 o Clarified that, by default, the scope of these addresses is 680 global. 681 o Renumbered sections and general text improvements 682 o Removed reserved global ID values 683 o Added pseudo code for local allocation submitted by Brian 684 Haberman and added him as an author. 685 o Split Global ID values into centrally assigned and local 686 assignments and added text to describe local assignments 688 Draft 690 o Initial Draft