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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (November 19, 2007) is 5975 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- -- Obsolete informational reference (is this intentional?): RFC 2460 (ref. '1') (Obsoleted by RFC 8200) -- Obsolete informational reference (is this intentional?): RFC 4941 (ref. '3') (Obsoleted by RFC 8981) -- Obsolete informational reference (is this intentional?): RFC 3315 (ref. '6') (Obsoleted by RFC 8415) -- Obsolete informational reference (is this intentional?): RFC 4214 (ref. '10') (Obsoleted by RFC 5214) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 11 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IPv6 Operations T. Chown 3 Internet-Draft University of Southampton 4 Intended status: Informational November 19, 2007 5 Expires: May 22, 2008 7 IPv6 Implications for Network Scanning 8 draft-ietf-v6ops-scanning-implications-04 10 Status of this Memo 12 By submitting this Internet-Draft, each author represents that any 13 applicable patent or other IPR claims of which he or she is aware 14 have been or will be disclosed, and any of which he or she becomes 15 aware will be disclosed, in accordance with Section 6 of BCP 79. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at 28 http://www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on May 22, 2008. 35 Copyright Notice 37 Copyright (C) The IETF Trust (2007). 39 Abstract 41 The much larger default 64-bit subnet address space of IPv6 should in 42 principle make traditional network (port) scanning techniques used by 43 certain network worms or scanning tools less effective. While 44 traditional network scanning probes (whether by individuals or 45 automated via network worms) may become less common, administrators 46 should be aware that attackers may use other techniques to discover 47 IPv6 addresses on a target network, and thus they should also be 48 aware of measures that are available to mitigate against them. This 49 informational document discusses approaches that administrators could 50 take when planning their site address allocation and management 51 strategies as part of a defence-in-depth approach to network 52 security. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2. Target Address Space for Network Scanning . . . . . . . . . . 4 58 2.1. IPv4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 2.2. IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 2.3. Reducing the IPv6 Search Space . . . . . . . . . . . . . . 4 61 2.4. Dual-stack Networks . . . . . . . . . . . . . . . . . . . 5 62 2.5. Defensive Scanning . . . . . . . . . . . . . . . . . . . . 5 63 3. Alternatives for Attackers: Off-link . . . . . . . . . . . . . 5 64 3.1. Gleaning IPv6 prefix information . . . . . . . . . . . . . 5 65 3.2. DNS Advertised Hosts . . . . . . . . . . . . . . . . . . . 6 66 3.3. DNS Zone Transfers . . . . . . . . . . . . . . . . . . . . 6 67 3.4. Log File Analysis . . . . . . . . . . . . . . . . . . . . 6 68 3.5. Application Participation . . . . . . . . . . . . . . . . 6 69 3.6. Multicast Group Addresses . . . . . . . . . . . . . . . . 6 70 3.7. Transition Methods . . . . . . . . . . . . . . . . . . . . 7 71 4. Alternatives for Attackers: On-link . . . . . . . . . . . . . 7 72 4.1. General on-link methods . . . . . . . . . . . . . . . . . 7 73 4.2. Intra-site Multicast or Other Service Discovery . . . . . 8 74 5. Tools to Mitigate Against Scanning Attacks . . . . . . . . . . 8 75 5.1. IPv6 Privacy Addresses . . . . . . . . . . . . . . . . . . 8 76 5.2. Cryptographically Generated Addresses (CGAs) . . . . . . . 9 77 5.3. Non-use of MAC addresses in EUI-64 format . . . . . . . . 9 78 5.4. DHCP Service Configuration Options . . . . . . . . . . . . 10 79 6. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 10 80 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 81 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 82 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 83 10. Informative References . . . . . . . . . . . . . . . . . . . . 11 84 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12 85 Intellectual Property and Copyright Statements . . . . . . . . . . 13 87 1. Introduction 89 One of the key differences between IPv4 and IPv6 is the much larger 90 address space for IPv6, which also goes hand-in-hand with much larger 91 subnet sizes. This change has a significant impact on the 92 feasibility of TCP and UDP network scanning, whereby an automated 93 process is run to detect open ports (services) on systems that may 94 then be subject of a subsequent attack. Today many IPv4 sites are 95 subjected to such probing on a recurring basis. Such probing is 96 common in part due to the relatively dense population of active hosts 97 in any given chunk of IPv4 address space. 99 The 128 bits of IPv6 [1] address space is considerably bigger than 100 the 32 bits of address space in IPv4. In particular, the IPv6 101 subnets to which hosts attach will by default have 64 bits of host 102 address space [2]. As a result, traditional methods of remote TCP or 103 UDP network scanning to discover open or running services on a host 104 will potentially become less feasible, due to the larger search space 105 in the subnet. Similarly, worms that rely on off-link network 106 scanning to propagate may also be potentially be more limited in 107 impact. This document discusses this property of IPv6, and describes 108 related issues for IPv6 site network administrators to consider, 109 which may be useful when planning site address allocation and 110 management strategies. 112 For example, many worms, like Slammer, rely on such address scanning 113 methods to propagate, whether they pick subnets numerically (and thus 114 probably topologically) close to the current victim, or subnets in 115 random remote networks. The nature of these worms may change, if 116 detection of target hosts between sites or subnets is harder to 117 achieve by traditional methods. However, there are other worms that 118 propagate via methods such as email, for which the methods discussed 119 in this text are not relevant. 121 It must be remembered that the defence of a network must not rely 122 solely on the unpredictable sparseness of the host addresses on that 123 network. Such a feature or property is only one measure in a set of 124 measures that may be applied. This document discusses various 125 measures that can be used by a site to mitigate against attacks as 126 part of an overall strategy. Some of these have a lower cost to 127 deploy than others. For example, if numbering hosts on a subnet, it 128 may be as cheap to number hosts without any predictable pattern as it 129 is to number them sequentially. In contrast, use of IPv6 Privacy 130 Extensions [3] may complicate network management (identifying which 131 hosts use which addresses). 133 This document complements the transition-centric discussion of the 134 issues that can be found in Appendix A of the IPv6 Transition/ 135 Co-existence Security Considerations text [12], which takes a broad 136 view of security issues for transitioning networks. The reader is 137 also referred to a recent paper by Bellovin on network worm 138 propagation strategies in IPv6 networks [13]. This paper discusses 139 some of the issues included in this document, from a slightly 140 different perspective. 142 2. Target Address Space for Network Scanning 144 There are significantly different considerations for the feasibility 145 of plain, brute force IPv4 and IPv6 address scanning. 147 2.1. IPv4 149 A typical IPv4 subnet may have 8 bits reserved for host addressing. 150 In such a case, a remote attacker need only probe at most 256 151 addresses to determine if a particular service is running publicly on 152 a host in that subnet. Even at only one probe per second, such a 153 scan would take under 5 minutes to complete. 155 2.2. IPv6 157 A typical IPv6 subnet will have 64 bits reserved for host addressing. 158 In such a case, a remote attacker in principle needs to probe 2^64 159 addresses to determine if a particular open service is running on a 160 host in that subnet. At a very conservative one probe per second, 161 such a scan may take some 5 billion years to complete. A more rapid 162 probe will still be limited to (effectively) infinite time for the 163 whole address space. However, there are ways for the attacker to 164 reduce the address search space to scan against within the target 165 subnet, as we discuss below. 167 2.3. Reducing the IPv6 Search Space 169 The IPv6 host address space through which an attacker may search can 170 be reduced in at least two ways. 172 First, the attacker may rely on the administrator conveniently 173 numbering their hosts from [prefix]::1 upward. This makes scanning 174 trivial, and thus should be avoided unless the host's address is 175 readily obtainable from other sources (for example it is the site's 176 published primary DNS or email MX server). Alternatively if hosts 177 are numbered sequentially, or using any regular scheme, knowledge of 178 one address may expose other available addresses to scan. 180 Second, in the case of statelessly autoconfiguring [1] hosts, the 181 host part of the address will usually take a well-known format that 182 includes the Ethernet vendor prefix and the "fffe" stuffing. For 183 such hosts, the search space can be reduced to 48 bits. Further, if 184 the Ethernet vendor is also known, the search space may be reduced to 185 24 bits, with a one probe per second scan then taking a less daunting 186 194 days. Even where the exact vendor is not known, using a set of 187 common vendor prefixes can reduce the search. In addition, many 188 nodes in a site network may be procured in batches, and thus have 189 sequential or near sequential MAC addresses; if one node's 190 autoconfigured address is known, scanning around that address may 191 yield results for the attacker. Again, any form of sequential host 192 addressing should be avoided if possible. 194 2.4. Dual-stack Networks 196 Full advantage of the increased IPv6 address space in terms of 197 resilience to network scanning may not be gained until IPv6-only 198 networks and devices become more commonplace, given that most IPv6 199 hosts are currently dual stack, with (more readily scannable) IPv4 200 connectivity. However, many applications or services (e.g. new peer- 201 to-peer applications) on the (dual stack) hosts may emerge that are 202 only accessible over IPv6, and that thus can only be discovered by 203 IPv6 address scanning. 205 2.5. Defensive Scanning 207 The problem faced by the attacker for an IPv6 network is also faced 208 by a site administrator looking for vulnerabilities in their own 209 network's systems. The administrator should have the advantage of 210 being on-link for scanning purposes though. 212 3. Alternatives for Attackers: Off-link 214 If IPv6 hosts in subnets are allocated addresses 'randomly', and as a 215 result IPv6 network scanning becomes relatively infeasible, attackers 216 will need to find new methods to identify IPv6 addresses for 217 subsequent scanning. In this section, we discuss some possible paths 218 attackers may take. In these cases, the attacker will attempt to 219 identify specific IPv6 addresses for subsequent targeted probes. 221 3.1. Gleaning IPv6 prefix information 223 Note that in IPv6 an attacker would not be able to search across the 224 entire IPv6 address space as they might in IPv4. An attacker may 225 learn general prefixes to focus their efforts on by observing route 226 view information (e.g. from public looking glass services) or 227 information on allocated address space from RIRs. In general this 228 would only yield information at most at the /48 prefix granularity, 229 but specific /64 prefixes may be observed from route views on some 230 parts of some networks. 232 3.2. DNS Advertised Hosts 234 Any servers that are DNS listed, e.g. MX mail relays, or web 235 servers, will remain open to probing from the very fact that their 236 IPv6 addresses will be published in the DNS. 238 While servers are relatively easy to find because they are DNS- 239 published, any systems that are not DNS-published will be much harder 240 to locate via traditional scanning than is the case for IPv4 241 networks. It is worth noting that where a site uses sequential host 242 numbering, publishing just one address may lead to a threat upon the 243 other hosts. 245 3.3. DNS Zone Transfers 247 In the IPv6 world a DNS zone transfer is much more likely to narrow 248 the number of hosts an attacker needs to target. This implies 249 restricting zone transfers is (more) important for IPv6, even if it 250 is already good practice to restrict them in the IPv4 world. 252 There are some projects that provide Internet mapping data from 253 access to such transfers. Administrators may of course agree to 254 provide such transfers where they choose to do so. 256 3.4. Log File Analysis 258 IPv6 addresses may be harvested from recorded logs such as web site 259 logs. Anywhere else where IPv6 addresses are explicitly recorded may 260 prove a useful channel for an attacker, e.g. by inspection of the 261 (many) Received from: or other header lines in archived email or 262 Usenet news messages. 264 3.5. Application Participation 266 More recent peer-to-peer applications often include some centralised 267 server which coordinates the transfer of data between peers. The 268 BitTorrent application builds swarms of nodes that exchange chunks of 269 files, with a tracker passing information about peers with available 270 chunks of data between the peers. Such applications may offer an 271 attacker a source of peer IP addresses to probe. 273 3.6. Multicast Group Addresses 275 Where an Embedded RP [7] multicast group address is known, the 276 unicast address of the rendezvous point is implied by the group 277 address. Where unicast prefix based multicast group addresses [5] 278 are used, specific /64 link prefixes may also be disclosed in traffic 279 that goes off-site. An administrator may thus choose to put aside 280 /64 bit prefixes for multicast group addresses that are not in use 281 for normal unicast routing and addressing. Alternatively a site may 282 simply use their /48 site prefix allocation to generate RFC3306 283 multicast group addresses. 285 3.7. Transition Methods 287 Specific knowledge of the target network may be gleaned if that 288 attacker knows it is using 6to4 [4], ISATAP [10], Teredo [11] or 289 other techniques that derive low-order bits from IPv4 addresses 290 (though in this case, unless they are using IPv4 NAT, the IPv4 291 addresses may be probed anyway). 293 For example, the current Microsoft 6to4 implementation uses the 294 address 2002:V4ADDR::V4ADDR while older Linux and FreeBSD 295 implementations default to 2002:V4ADDR::1. This leads to specific 296 knowledge of specific hosts in the network. Given one host in the 297 network is observed as using a given transition technique, it is 298 likely that there are more. 300 In the case of Teredo, the 64 bit node identifier is generated from 301 the IPv4 address observed at a Teredo server along with a UDP port 302 number. The Teredo specification also allows for discovery of other 303 Teredo clients on the same IPv4 subnet via a well-known IPv4 304 multicast address (see Section 2.17 of RFC4380 [11]). 306 4. Alternatives for Attackers: On-link 308 The main thrust of this text is considerations for off-link attackers 309 or probing of a network. In general, once one host on a link is 310 compromised, others on the link can be very readily discovered. 312 4.1. General on-link methods 314 If the attacker already has access to a system on the current subnet, 315 then traffic on that subnet, be it Neighbour Discovery or application 316 based traffic, can invariably be observed, and active node addresses 317 within the local subnet learnt. 319 In addition to making observations of traffic on the link, IPv6- 320 enabled hosts on local subnets may be discovered through probing the 321 "all hosts" link local multicast address. Likewise any routers on 322 the subnet may be found via the "all routers" link local multicast 323 address. An attacker may choose to probe in a slightly more 324 obfuscated way by probing the solicited node multicast address of a 325 potential target host. 327 Where a host has already been compromised, its Neighbour Discovery 328 cache is also likely to include information about active nodes on the 329 current subnet, just as an ARP cache would do for IPv4. 331 Also, depending on the node, traffic to or from other nodes (in 332 particular server systems) is likely to show up if an attacker can 333 gain a presence on a node in any one subnet in a site's network. 335 4.2. Intra-site Multicast or Other Service Discovery 337 A site may also have site or organisational scope multicast 338 configured, in which case application traffic, or service discovery, 339 may be exposed site wide. An attacker may also choose to use any 340 other service discovery methods supported by the site. 342 5. Tools to Mitigate Against Scanning Attacks 344 There are some tools that site administrators can apply to make the 345 task for IPv6 network scanning attackers harder. These methods arise 346 from the considerations in the previous section. 348 The author notes that at his current (university) site, there is no 349 evidence of general network scanning running across subnets. 350 However, there is network scanning over IPv6 connections to systems 351 whose IPv6 addresses are advertised (DNS servers, MX relays, web 352 servers, etc), which are presumably looking for other open ports on 353 these hosts to probe. At the time of writing, DHCPv6 DHCPv6 [6] is 354 not yet in use, and clients use stateless autoconfiguration. 355 Therefore the author's site does not yet have sequentially numbered 356 client hosts deployed as may typically seen in today's IPv4 DHCP- 357 served networks. 359 5.1. IPv6 Privacy Addresses 361 Hosts in a network using IPv6 Privacy Extensions [3] will typically 362 only connect to external systems using their current (temporary) 363 privacy address. The precise behaviour of a host with a stable 364 global address and one or more dynamic privacy address(es) when 365 selecting a source address to use may be operating-system specific, 366 or configuarable, but typical behaviour when initiating a connection 367 is use of a privacy address when available. 369 While an attacker may be able to port scan a privacy address if they 370 do so quickly upon observing or otherwise learning of the address, 371 the threat or risk is reduced due to the time-constrained value of 372 the address. One implementation of RFC4941 already deployed has 373 privacy addresses active (used by the node) for one day, with such 374 addresses reachable for seven days. 376 Note that an RFC4941 host will usually also have a separate static 377 global IPv6 address by which it can also be reached, and that may be 378 DNS-advertised if an externally reachable service is running on it. 379 DHCPv6 can be used to serve normal global addresses and IPv6 Privacy 380 Addresses. 382 The implication is that while Privacy Addresses can mitigate the 383 long-term value of harvested addresses, an attacker creating an IPv6 384 application server to which clients connect will still be able to 385 probe the clients by their Privacy Address as and when they visit 386 that server. The duration for which Privacy Addresses are valid will 387 impact on the usefulness of such observed addresses to an external 388 attacker. For example, a worm that may spread using such observed 389 addresses may be less effective if it relies on harvested privacy 390 addresses. The frequency with which such address get recycled could 391 be increased, though this may increase the complexity of local 392 network management for the administrator, since doing so will cause 393 more addresses to be used over time in the site. 395 A further option here may be to consider using different addresses 396 for specific applications, or even each new application instance, 397 which may reduce exposure to other services running on the same host 398 when such an address is observed externally. 400 5.2. Cryptographically Generated Addresses (CGAs) 402 The use of Cryptographically Generated Addresses (CGAs) [9] may also 403 cause the search space to be increased from that presented by default 404 use of Stateless Autoconfiguration. Such addresses would be seen 405 where Secure Neighbour Discovery (SEND) [8] is in use. 407 5.3. Non-use of MAC addresses in EUI-64 format 409 The EUI-64 identifier format does not require the use of MAC 410 addresses for identifier construction. At least one well-known 411 operating system currently defaults to generation of the 64 bit 412 interface identifier by use of random bits, and thus does not embed 413 the MAC address. Where such a method exists as an option, an 414 administrator may wish consider use of that option. 416 5.4. DHCP Service Configuration Options 418 One option open to an administrator is to configure DHCPv6, if 419 possible, so that the first addresses allocated from the pool begins 420 much higher in the address space than at [prefix]::1. Further, it is 421 desirable that allocated addresses are not sequential, nor have any 422 predictable pattern to them. Unpredictable sparseness in the 423 allocated addresses is a desirable property. DHCPv6 implementers 424 could reduce the cost for administrators to deploy such 'random' 425 addressing by supporting configuration options to allow such 426 behaviour. 428 DHCPv6 also includes an option to use Privacy Extension [3] 429 addresses, i.e. temporary addresses, as described in Section 12 of 430 the DHCPv6 [6] specification. 432 6. Conclusions 434 Due to the much larger size of IPv6 subnets in comparison to IPv4 it 435 will become less feasible for traditional network scanning methods to 436 detect open services for subsequent attacks, assuming the attackers 437 are off-site and services are not listed in the DNS. If 438 administrators number their IPv6 subnets in 'random', non-predictable 439 ways, attackers, whether they be in the form of automated network 440 scanners or dynamic worm propagation, will need to make wider use of 441 new methods to determine IPv6 host addresses to target (e.g. looking 442 to obtain logs of activity from a site and scanning addresses around 443 the ones observed). Such numbering schemes may be very low cost to 444 deploy in comparison to conventional sequential numbering, and thus a 445 useful part of an overall defence-in-depth strategy. Of course, if 446 those systems are dual-stack, and have open IPv4 services running, 447 they will remain exposed to traditional probes over IPv4 transport. 449 7. Security Considerations 451 There are no specific security considerations in this document 452 outside of the topic of discussion itself. However, it must be noted 453 that the 'security through obscurity' discussions and commentary 454 within this text must be noted in their proper context. Relying 455 purely on obscurity of a node address is not prudent, rather the 456 advice here should be considered as part of a 'defence-in-depth' 457 approach to security for a site or network. This also implies that 458 these measures require coordination between network administrators 459 and those who maintain DNS services, though that is common in most 460 scenarios. 462 8. IANA Considerations 464 There are no IANA considerations for this document. 466 9. Acknowledgements 468 Thanks are due to people in the 6NET project (www.6net.org) for 469 discussion of this topic, including Pekka Savola, Christian Strauf 470 and Martin Dunmore, as well as other contributors from the IETF v6ops 471 and other mailing lists, including Tony Finch, David Malone, Bernie 472 Volz, Fred Baker, Andrew Sullivan, Tony Hain, Dave Thaler and Alex 473 Petrescu. Thanks are also due for editorial feedback from Brian 474 Carpenter, Lars Eggert and Jonne Soininen amongst others. 476 10. Informative References 478 [1] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) 479 Specification", RFC 2460, December 1998. 481 [2] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address 482 Autoconfiguration", RFC 4862, September 2007. 484 [3] Narten, T., Draves, R., and S. Krishnan, "Privacy Extensions 485 for Stateless Address Autoconfiguration in IPv6", RFC 4941, 486 September 2007. 488 [4] Carpenter, B. and K. Moore, "Connection of IPv6 Domains via 489 IPv4 Clouds", RFC 3056, February 2001. 491 [5] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 492 Multicast Addresses", RFC 3306, August 2002. 494 [6] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. 495 Carney, "Dynamic Host Configuration Protocol for IPv6 496 (DHCPv6)", RFC 3315, July 2003. 498 [7] Savola, P. and B. Haberman, "Embedding the Rendezvous Point 499 (RP) Address in an IPv6 Multicast Address", RFC 3956, 500 November 2004. 502 [8] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure 503 Neighbor Discovery (SEND)", RFC 3971, March 2005. 505 [9] Aura, T., "Cryptographically Generated Addresses (CGA)", 506 RFC 3972, March 2005. 508 [10] Templin, F., Gleeson, T., Talwar, M., and D. Thaler, "Intra- 509 Site Automatic Tunnel Addressing Protocol (ISATAP)", RFC 4214, 510 October 2005. 512 [11] Huitema, C., "Teredo: Tunneling IPv6 over UDP through Network 513 Address Translations (NATs)", RFC 4380, February 2006. 515 [12] Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/ 516 Co-existence Security Considerations", RFC 4942, 517 September 2007. 519 [13] Bellovin, S. et al, "Worm Propagation Strategies in an IPv6 520 Internet (http://www.cs.columbia.edu/~smb/papers/v6worms.pdf)", 521 ;login:, February 2006. 523 Author's Address 525 Tim Chown 526 University of Southampton 527 Southampton, Hampshire SO17 1BJ 528 United Kingdom 530 Email: tjc@ecs.soton.ac.uk 532 Full Copyright Statement 534 Copyright (C) The IETF Trust (2007). 536 This document is subject to the rights, licenses and restrictions 537 contained in BCP 78, and except as set forth therein, the authors 538 retain all their rights. 540 This document and the information contained herein are provided on an 541 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 542 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 543 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 544 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 545 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 546 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 548 Intellectual Property 550 The IETF takes no position regarding the validity or scope of any 551 Intellectual Property Rights or other rights that might be claimed to 552 pertain to the implementation or use of the technology described in 553 this document or the extent to which any license under such rights 554 might or might not be available; nor does it represent that it has 555 made any independent effort to identify any such rights. 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