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Azinger 3 Internet-Draft Frontier Communications 4 Intended status: Informational Corporation 5 Expires: July 8, 2011 L. Vegoda 6 ICANN 7 January 4, 2011 9 Issues Associated with Designating Additional Private IPv4 Address Space 10 draft-azinger-additional-private-ipv4-space-issues-05 12 Abstract 14 When a private network or internetwork grows very large it is 15 sometimes not possible to address all interfaces using private IPv4 16 address space because there are not enough addresses. This document 17 describes the problems faced by those networks, the available options 18 and the issues involved in assigning a new block of private IPv4 19 address space. 21 While this informational document does not make a recommendation for 22 action, it documents the issues surrounding the various options that 23 have been considered. 25 Status of this Memo 27 This Internet-Draft is submitted to IETF in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF), its areas, and its working groups. Note that 32 other groups may also distribute working documents as Internet- 33 Drafts. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 The list of current Internet-Drafts can be accessed at 41 http://www.ietf.org/ietf/1id-abstracts.txt. 43 The list of Internet-Draft Shadow Directories can be accessed at 44 http://www.ietf.org/shadow.html. 46 This Internet-Draft will expire on July 8, 2011. 48 Copyright Notice 49 Copyright (c) 2011 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Large Networks . . . . . . . . . . . . . . . . . . . . . . . . 3 66 3. Non-Unique Addresses . . . . . . . . . . . . . . . . . . . . . 3 67 3.1. Subscriber Use Network Address Translation . . . . . . . . 3 68 3.2. Carrier Grade Network Address Translation . . . . . . . . 4 69 4. Available Options . . . . . . . . . . . . . . . . . . . . . . 4 70 4.1. IPv6 Options . . . . . . . . . . . . . . . . . . . . . . . 4 71 4.1.1. Unique Globally Scoped IPv6 Unicast Addresses . . . . 4 72 4.1.2. Unique Local IPv6 Unicast Addresses . . . . . . . . . 4 73 4.2. IPv4 Options . . . . . . . . . . . . . . . . . . . . . . . 5 74 4.2.1. Address Transfers or Leases From Organizations 75 with Available Address Space . . . . . . . . . . . . . 5 76 4.2.2. Using Unannounced Address Space Allocated to 77 Another Organization . . . . . . . . . . . . . . . . . 5 78 4.2.3. Unique IPv4 Space Registered by an RIR . . . . . . . . 6 79 5. Options and Consequences for Defining New Private Use Space . 6 80 5.1. Redefining Existing Unicast Space as Private Address 81 Space . . . . . . . . . . . . . . . . . . . . . . . . . . 6 82 5.2. Unique IPv4 Space Shared by a Group of Operators . . . . . 7 83 5.3. Potential Consequences of Not Redefining Existing 84 Unicast Space as Private Address Space . . . . . . . . . . 8 85 5.4. Redefining Future Use Space as Unicast Address Space . . . 8 86 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 87 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 88 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 89 8.1. Normative References . . . . . . . . . . . . . . . . . . . 9 90 8.2. Informative References . . . . . . . . . . . . . . . . . . 9 91 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 11 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 94 1. Introduction 96 [RFC1918] sets aside three blocks of IPv4 address space for use in 97 private networks: 192.168.0.0/16, 172.16.0.0/12 and 10.0.0.0/8. 98 These blocks can be used simultaneously in multiple, separately 99 managed networks without registration or coordination with IANA or 100 any Internet registry. Very large networks can find that they need 101 to number more device interfaces than there are available addresses 102 in these three ranges. It has occasionally been suggested that 103 additional private IPv4 address space should be reserved for use by 104 these networks. Although such an action might address some of the 105 needs for these very large network operators it is not without 106 consequences, particularly as we near the date when the IANA free 107 pool will be fully allocated. 109 2. Large Networks 111 The main categories of very large networks using private address 112 space are: cable operators, wireless (cell phone) operators, private 113 internets and VPN service providers. In the case of the first two 114 categories, the complete address space reserved in [RFC1918] tends to 115 be used by a single organization. In the case of private internets 116 and VPN service providers there are multiple independently managed 117 and operated networks and the difficulty is in avoiding address 118 clashes. 120 3. Non-Unique Addresses 122 3.1. Subscriber Use Network Address Translation 124 The address space set aside in [RFC1918] is a finite resource which 125 can be used to provide limited Internet access via Network Address 126 Translation (NAT). A discussion of the advantages and disadvantages 127 of NATs is outside the scope of this document but a an analysis of 128 the advantages, disadvantages and architectural implications can be 129 found in [RFC2993]. Nonetheless, it must be acknowledged that NAT is 130 adequate in some situations and not in others. For instance, it 131 might technically feasible to use NAT or even multiple layers of NAT 132 within the networks operated by residential users or corporations 133 where only limited Internet access is required. A more detailed 134 analysis can be found in [RFC3022]. Where true peer to peer 135 communication is needed or where services or applications do not work 136 properly behind NAT, globally unique address space is required. In 137 other cases, NAT traversal techniques facilitate peer-to-peer like 138 communication for devices behind NATs. 140 In many cases it is possible to use multiple layers of NAT to re-use 141 parts of the address space defined in [RFC1918]. It is not always 142 possible to rely on CPE devices using any particular range, however. 143 In some cases this means that unorthodox workarounds including 144 assigning CPE devices unallocated address space or address space 145 allocated to other network operators are feasible. In other cases, 146 organizations choose to operate multiple separate routing domains to 147 allow them to re-use the same private address ranges in multiple 148 contexts. One consequence of this is the added complexity involved 149 in identifying which system is referred to when an IP address is 150 identified in a log or management systems. 152 3.2. Carrier Grade Network Address Translation 154 Another option is to share one address across multiple interfaces and 155 in some cases, subscribers. This model breaks the classical model 156 used for logging address assignments and creates significant risks 157 and additional burdens, as described in [CLAYTON] and more fully 158 discussed in [FORD] and is documented in [DS-LITE]. 160 4. Available Options 162 When a network operator has exhausted the private address space set 163 aside in [RFC1918] but needs to continue operating a single routing 164 domain a number of options are available. These include: 166 4.1. IPv6 Options 168 4.1.1. Unique Globally Scoped IPv6 Unicast Addresses 170 Using unique, globally scoped IPv6 unicast addresses is the best 171 permanent solution as it removes any concerns about address scarcity 172 within the next few decades. Implementing IPv6 is a major endeavor 173 for service providers with millions of consumer customers and is 174 likely to take considerable effort and time. In some cases 175 implementing a new network protocol on a very large network takes 176 more time than is available, based on network growth and the 177 proportion of private space that has already been used. In these 178 cases, there is a call for additional private address space that can 179 be shared by all network operators. [DAVIES] makes one such case. 181 4.1.2. Unique Local IPv6 Unicast Addresses 183 Using the unique, local IPv6 unicast addresses defined in [RFC4193] 184 is another approach and does not require coordination with an 185 Internet registry. Although the addresses defined in [RFC4193] are 186 probabilistically unique, network operators on private internets and 187 those providing VPN services might not want to use them because there 188 is a very low probability of non-unique locally assigned global IDs 189 being generated by the algorithm. Also, in the case of private 190 internets, it can be very challenging to coordinate the introduction 191 of a new network protocol to support the internet's continued growth. 193 4.2. IPv4 Options 195 4.2.1. Address Transfers or Leases From Organizations with Available 196 Address Space 198 The Regional Internet Registry (RIR) communities have recently been 199 developing policies to allow organizations with available address 200 space to transfer such designated space to other organizations 201 [RIR-POLICY]. In other cases, leases might be arranged. This 202 approach is only viable for operators of very large networks if 203 enough address space is made available for transfer or lease and if 204 the very large networks are able to pay the costs of these transfers. 205 It is not possible to know how much address space will become 206 available in this way, when it will be available and how much it will 207 cost. However, it is unlikely to become available in large 208 contiguous blocks and this would add to the network management burden 209 for the operator as a significant number of small prefixes would 210 inflate the size of the operators routing table at a time when it is 211 also adding an IPv6 routing table. These reasons will make address 212 transfers a less attractive proposition to many large network 213 operators. Leases might not be attractive to some organizations if 214 both parties cannot agree a suitable length of time. Also, the 215 lessor might worry about its own unanticipated needs for additional 216 IPv4 address space. 218 4.2.2. Using Unannounced Address Space Allocated to Another 219 Organization 221 Some network operators have considered using IP address space which 222 is allocated to another organization but is not publicly visible in 223 BGP routing tables. This option is very strongly discouraged as the 224 fact that an address block is not visible from one view does not mean 225 that it is not visible from another. Furthermore, address usage 226 tends to leak beyond private network borders in e-mail headers, DNS 227 queries, traceroute output and other ways. The ambiguity this causes 228 is problematic for multiple organizations. This issue is discussed 229 in [RFC3879], section 2.3. 231 It is also possible that the registrant of the address block might 232 want to increase its visibility to other networks in the future, 233 causing problems for anyone using it unofficially. In some cases 234 there might also be legal risks involved in using address space 235 officially allocated to another organization. 237 Where this has happened in the past it has caused operational 238 problems [FASTWEB]. 240 4.2.3. Unique IPv4 Space Registered by an RIR 242 RIRs policies allow network operators to receive unique IP addresses 243 for use on internal networks. Further, network operators are not 244 required to have already exhausted the private address space set 245 aside in [RFC1918]. Nonetheless, network operators are naturally 246 disinclined to request unique IPv4 addresses for the private areas of 247 their networks as using addresses in this way means they are not 248 available for use by new Internet user connections. 250 It is likely to become more difficult for network operators to obtain 251 large blocks of unique address space as we approach the point where 252 all IPv4 unicast /8s have been allocated. Several RIRs already have 253 policies how to allocate from their last /8 [RIR-POLICY-FINAL-8] and 254 there have been policy discussions that would reduce the maximum 255 allocation size available to network operators [MAX-ALLOC] or would 256 reduce the period of need for which the RIR can allocate 257 [SHORTER-PERIODS]. 259 5. Options and Consequences for Defining New Private Use Space 261 5.1. Redefining Existing Unicast Space as Private Address Space 263 It is possible to re-designate a portion of the current global 264 unicast IPv4 address space as private unicast address space. Doing 265 this could benefit a number of operators of large network for the 266 short period before they complete their IPv6 roll-out. However, this 267 benefit incurs a cost by reducing the pool of global unicast 268 addresses available to users in general. 270 When discussing re-designating a portion of the current global 271 unicast IPv4 address space as private unicast address space it is 272 important to consider how much space would be used and for how long 273 it would be sufficient. Not all of the large networks making full 274 use of the space defined in [RFC1918] would have their needs met with 275 a single /8. In 2005, [HAIN] suggested reserving three /8s for this 276 purpose while in 2009 [DAVIES] suggested a single /10 would be 277 sufficient. There does not seem to be a consensus for a particular 278 prefix length nor an agreed basis for deciding what is sufficient. 279 The problem is exacerbated by the continually changing needs of ever 280 expanding networks. 282 A further consideration is which of the currently unallocated IPv4 283 unicast /8 blocks should be used for this purpose. Using address 284 space which is known to be used unofficially is tempting. For 285 instance, 1.0.0.0/8, which was unallocated until January 2010, was 286 proposed in [HAIN] and is known to be used by a number of different 287 users. These include networks making use of HIP LSIs [RFC4423], 288 [WIANA], [anoNet] and others. There is anecdotal [VEGODA] and 289 research [WESSELS] evidence to suggest that several other IPv4 /8s 290 are used in this fashion. Also there have been discussions [NANOG] 291 about some sections of these /8's being carved out and filtered 292 therefore unofficially enabling the use of these sections for private 293 use. 295 Although new IPv4 /8s are allocated approximately once a month, they 296 are not easy to bring into use because network operators are slow to 297 change their filter configurations. This is despite long-running 298 awareness campaigns [CYMRU], [LEWIS] and active work [ripe-351] to 299 notify people whose filters are not changed in a timely fashion. 300 Updating code that recognises private address space in deployed 301 software and infrastructure systems is likely to be far more 302 difficult as many systems have these ranges hard-coded and cannot be 303 quickly changed with a new configuration file. 305 Another consideration when redefining existing unicast space as 306 private address space is that no single class of user can expect the 307 space to stay unique to them. This means that an ISP using a new 308 private address range cannot expect its customers not to already be 309 using that address range within their own networks. 311 5.2. Unique IPv4 Space Shared by a Group of Operators 313 Where a group of networks find themselves in a position where they 314 each need a large amount of IPv4 address space from an RIR in 315 addition to that defined in [RFC1918] they might cooperatively agree 316 to all use the same address space to number their networks. The 317 clear benefit to this approach is that it significantly reduces the 318 potential demand on the pool of unallocated IPv4 address space. 319 However, the issues discussed in 4.4 could also be of concern here, 320 particularly the possibility that one operator might decide to use 321 the address space to number customer connections, rather than private 322 infrastructure. 324 Nonetheless, this approach has the potential to create an unofficial 325 new private address range without proper scrutiny. 327 5.3. Potential Consequences of Not Redefining Existing Unicast Space as 328 Private Address Space 330 If additional private address space is not defined and the large 331 network operators affected by this problem are not able to solve 332 their problems with IPv6 address space or by segmenting their 333 networks into multiple routing domains, those networks will need 334 unique IPv4 addresses. It is possible and even likely that a single 335 network could consume a whole IPv4 /8 in a year. At the time of 336 writing there are just 24 unallocated IPv4 /8s, so it would not take 337 many such requests to make a major dent in the available IPv4 address 338 space. [POTAROO] provides an analysis of IPv4 address consumption 339 and projects the date on which the IANA and RIR pools will be fully 340 allocated. 342 5.4. Redefining Future Use Space as Unicast Address Space 344 There have also been proposals to re-designate the former Class E 345 space (240.0.0.0/4) as unicast address space. [WILSON] suggests that 346 it should be privately scoped while [FULLER] does not propose a 347 scope. Both proposals note that existing deployed equipment may not 348 be able to use addresses from 240.0.0.0/4. Potential users would 349 need to be sure of the status of the equipment on their network and 350 the networks with which they intend to communicate. 352 It is not immediately clear how useful 240.0.0.0/4 could be in 353 practice. While [FULLER] documents the status of several popular 354 desktop and server operating systems, the status of the most widely 355 deployed routers and switches is less clear and it is possible that 356 240.0.0.0/4 might only be useful in very large, new green field 357 deployments where full control of all deployed systems is available. 358 However, in such cases it might well be easier to deploy an IPv6 359 network. 361 6. Security Considerations 363 This document has no security implications. 365 7. IANA Considerations 367 This document makes no request of IANA. 369 8. References 370 8.1. Normative References 372 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 373 E. Lear, "Address Allocation for Private Internets", 374 BCP 5, RFC 1918, February 1996. 376 [RFC2993] Hain, T., "Architectural Implications of NAT", RFC 2993, 377 November 2000. 379 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 380 Address Translator (Traditional NAT)", RFC 3022, 381 January 2001. 383 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 384 Addresses", RFC 4193, October 2005. 386 8.2. Informative References 388 [RFC3879] Huitema, C. and B. Carpenter, "Deprecating Site Local 389 Addresses", RFC 3879, September 2004. 391 [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol 392 (HIP) Architecture", RFC 4423, May 2006. 394 [anoNet] anoNet, "anoNet: Cooperative Chaos", 395 . 397 [CLAYTON] Clayton, R., "Practical mobile Internet access 398 traceability", January 2010, . 402 [CYMRU] Greene, B., "The Bogon Reference", 403 . 405 [DAVIES] Davies, G. and C. Liljenstolpe, "Work in Progress: 406 Transitional non-conflicting reusable IPv4 address block", 407 November 2009, . 410 [DS-LITE] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Work in 411 Progress: Dual-Stack Lite Broadband Deployments Following 412 IPv4 Exhaustion", August 2010, . 415 [FASTWEB] Aina, A., "41/8 announcement", May 2006, 416 . 418 [FORD] Ford, M., Boucadair, M., Durand, A., Levis, P., and P. 419 Roberts, "Work in Progress: Issues with IP Address 420 Sharing", March 2010, . 423 [FULLER] Fuller, V., Lear, E., and D. Meyer, "Work in Progress: 424 Reclassifying 240/4 as usable unicast address space", 425 March 2008, 426 . 428 [HAIN] Hain, T., "Work in Progress: Expanded Address Allocation 429 for Private Internets", January 2005, 430 . 432 [LEWIS] Lewis, J., "This system has been setup for testing 433 purposes for 69/8 address space", March 2003, 434 . 436 [MAX-ALLOC] 437 Spenceley, J. and J. Martin, "prop-070: Maximum IPv4 438 allocation size", January 2009, 439 . 441 [NANOG] Dickson, B., "1/8 and 27/8 allocated to APNIC", 442 January 2010, . 445 [POTAROO] Huston, G., "IPv4 Address Report", 446 . 448 [ripe-351] 449 Karrenberg, D., "De-Bogonising New Address Blocks", 450 October 2005, 451 . 453 [RIR-POLICY] 454 Number Resource Organization, "RIR Comparative Policy 455 Overview, October 2009, Section 1.3.2 Transfer of 456 Custodianship", 457 . 459 [RIR-POLICY-FINAL-8] 460 Number Resource Organization, "RIR Comparative Policy 461 Overview, October 2009, 2.6. Use of Final Unallocated IPv4 462 Address Space", October 2009, 463 . 465 [SHORTER-PERIODS] 466 Karrenberg, D., O'Reilly, N., Titley, N., and R. Bush, 467 "RIPE Policy Proposal 2009-03", April 2009, 468 . 471 [VEGODA] Vegoda, L., "Awkward /8 Assignments", September 2007, . 475 [WESSELS] Wessels, D., "Searching for Evidence of Unallocated 476 Address Space Usage in DITL 2008 Data", June 2008, . 480 [WIANA] WIANA, "The Wireless Internet Assigned Numbers Authority", 481 . 483 [WILSON] Wilson, P., Michaelson, G., and G. Huston, "Work in 484 Progress: Redesignation of 240/4 from "Future Use" to 485 "Private Use"", 486 . 488 Appendix A. Acknowledgments 490 The authors would also like to thank Ron Bonica, Michelle Cotton, Lee 491 Howard and Barbara Roseman for their assistance in early discussions 492 of this document and to Maria Blackmore, Alex Bligh, Mat Ford, Thomas 493 Narten, Ricardo Patara and for improvement suggestions. 495 Authors' Addresses 497 Marla Azinger 498 Frontier Communications Corporation 499 Vancouver, WA 500 United States of America 502 Email: marla.azinger@ftr.com 503 URI: http://www.frontiercorp.com/ 504 Leo Vegoda 505 Internet Corporation for Assigned Names and Numbers 506 4676 Admiralty Way, Suite 330 507 Marina del Rey, CA 90292 508 United States of America 510 Phone: +1-310-823-9358 511 Email: leo.vegoda@icann.org 512 URI: http://www.iana.org/