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StJohns 3 Internet-Draft Nominum, Inc. 4 Expires: January 17, 2007 July 16, 2006 6 Automated Updates of DNSSEC Trust Anchors 7 draft-ietf-dnsext-trustupdate-timers-03 9 Status of this Memo 11 By submitting this Internet-Draft, each author represents that any 12 applicable patent or other IPR claims of which he or she is aware 13 have been or will be disclosed, and any of which he or she becomes 14 aware will be disclosed, in accordance with Section 6 of BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on January 17, 2007. 34 Copyright Notice 36 Copyright (C) The Internet Society (2006). 38 Abstract 40 This document describes a means for automated, authenticated and 41 authorized updating of DNSSEC "trust anchors". The method provides 42 protection against single key compromise of a key in the trust point 43 key set. Based on the trust established by the presence of a current 44 anchor, other anchors may be added at the same place in the 45 hierarchy, and, ultimately, supplant the existing anchor. 47 This mechanism will require changes to resolver management behavior 48 (but not resolver resolution behavior), and the addition of a single 49 flag bit to the DNSKEY record. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 1.1. Compliance Nomenclature . . . . . . . . . . . . . . . . . 3 55 1.2. Changes since -00 . . . . . . . . . . . . . . . . . . . . 3 56 2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4 57 2.1. Revocation . . . . . . . . . . . . . . . . . . . . . . . . 4 58 2.2. Add Hold-Down . . . . . . . . . . . . . . . . . . . . . . 5 59 2.3. Remove Hold-down . . . . . . . . . . . . . . . . . . . . . 6 60 2.4. Active Refresh . . . . . . . . . . . . . . . . . . . . . . 6 61 2.5. Resolver Parameters . . . . . . . . . . . . . . . . . . . 6 62 2.5.1. Add Hold-Down Time . . . . . . . . . . . . . . . . . . 6 63 2.5.2. Remove Hold-Down Time . . . . . . . . . . . . . . . . 6 64 2.5.3. Minimum Trust Anchors per Trust Point . . . . . . . . 6 65 3. Changes to DNSKEY RDATA Wire Format . . . . . . . . . . . . . 7 66 4. State Table . . . . . . . . . . . . . . . . . . . . . . . . . 7 67 4.1. Events . . . . . . . . . . . . . . . . . . . . . . . . . . 7 68 4.2. States . . . . . . . . . . . . . . . . . . . . . . . . . . 8 69 4.3. Trust Point Deletion . . . . . . . . . . . . . . . . . . . 8 70 5. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 9 71 5.1. Adding A Trust Anchor . . . . . . . . . . . . . . . . . . 9 72 5.2. Deleting a Trust Anchor . . . . . . . . . . . . . . . . . 10 73 5.3. Key Roll-Over . . . . . . . . . . . . . . . . . . . . . . 10 74 5.4. Active Key Compromised . . . . . . . . . . . . . . . . . . 10 75 5.5. Stand-by Key Compromised . . . . . . . . . . . . . . . . . 10 76 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 77 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 78 7.1. Key Ownership vs Acceptance Policy . . . . . . . . . . . . 11 79 7.2. Multiple Key Compromise . . . . . . . . . . . . . . . . . 11 80 7.3. Dynamic Updates . . . . . . . . . . . . . . . . . . . . . 11 81 8. Normative References . . . . . . . . . . . . . . . . . . . . . 12 82 Editorial Comments . . . . . . . . . . . . . . . . . . . . . . . . 83 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13 84 Intellectual Property and Copyright Statements . . . . . . . . . . 14 86 1. Introduction 88 As part of the reality of fielding DNSSEC (Domain Name System 89 Security Extensions) [RFC2535] [RFC4033][RFC4034][RFC4035], the 90 community has come to the realization that there will not be one 91 signed name space, but rather islands of signed name space each 92 originating from specific points (i.e. 'trust points') in the DNS 93 tree. Each of those islands will be identified by the trust point 94 name, and validated by at least one associated public key. For the 95 purpose of this document we'll call the association of that name and 96 a particular key a 'trust anchor'. A particular trust point can have 97 more than one key designated as a trust anchor. 99 For a DNSSEC-aware resolver to validate information in a DNSSEC 100 protected branch of the hierarchy, it must have knowledge of a trust 101 anchor applicable to that branch. It may also have more than one 102 trust anchor for any given trust point. Under current rules, a chain 103 of trust for DNSSEC-protected data that chains its way back to ANY 104 known trust anchor is considered 'secure'. 106 Because of the probable balkanization of the DNSSEC tree due to 107 signing voids at key locations, a resolver may need to know literally 108 thousands of trust anchors to perform its duties. (e.g. Consider an 109 unsigned ".COM".) Requiring the owner of the resolver to manually 110 manage this many relationships is problematic. It's even more 111 problematic when considering the eventual requirement for key 112 replacement/update for a given trust anchor. The mechanism described 113 herein won't help with the initial configuration of the trust anchors 114 in the resolvers, but should make trust point key replacement/ 115 rollover more viable. 117 As mentioned above, this document describes a mechanism whereby a 118 resolver can update the trust anchors for a given trust point, mainly 119 without human intervention at the resolver. There are some corner 120 cases discussed (e.g. multiple key compromise) that may require 121 manual intervention, but they should be few and far between. This 122 document DOES NOT discuss the general problem of the initial 123 configuration of trust anchors for the resolver. 125 1.1. Compliance Nomenclature 127 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 128 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 129 document are to be interpreted as described in BCP 14, [RFC2119]. 131 1.2. Changes since -00 133 N.B. This section to be deleted prior to submission to RFC editor. 135 Added the concept of timer triggered resolver queries to refresh the 136 resolvers view of the trust anchor key RRSet. 138 Re-submitted expired draft as -01. Updated DNSSEC RFC References. 140 Draft -02. Added the IANA Considerations section. Added text to 141 describe what happens if all trust anchors at a trust point are 142 deleted. 144 Draft -03. Revised the trust point deletion language to note 145 limitations. 147 2. Theory of Operation 149 The general concept of this mechanism is that existing trust anchors 150 can be used to authenticate new trust anchors at the same point in 151 the DNS hierarchy. When a new SEP key (see [RFC4034] section 2.1.1) 152 is added to a trust point DNSKEY RRSet, and when that RRSet is 153 validated by an existing trust anchor, then the new key can be added 154 to the set of trust anchors. 156 There are some issues with this approach which need to be mitigated. 157 For example, a compromise of one of the existing keys could allow an 158 attacker to add their own 'valid' data. This implies a need for a 159 method to revoke an existing key regardless of whether or not that 160 key is compromised. As another example assuming a single key 161 compromise, an attacker could add a new key and revoke all the other 162 old keys. 164 2.1. Revocation 166 Assume two trust anchor keys A and B. Assume that B has been 167 compromised. Without a specific revocation bit, B could invalidate A 168 simply by sending out a signed trust point key set which didn't 169 contain A. To fix this, we add a mechanism which requires knowledge 170 of the private key of a DNSKEY to revoke that DNSKEY. 172 A key is considered revoked when the resolver sees the key in a self- 173 signed RRSet and the key has the REVOKE bit (see Section 6 below) set 174 to '1'. Once the resolver sees the REVOKE bit, it MUST NOT use this 175 key as a trust anchor or for any other purposes except validating the 176 RRSIG over the DNSKEY RRSet specifically for the purpose of 177 validating the revocation. Unlike the 'Add' operation below, 178 revocation is immediate and permanent upon receipt of a valid 179 revocation at the resolver. 181 A self-signed RRSet is a DNSKEY RRSet which contains the specific 182 DNSKey and for which there is a corresponding validated RRSIG record. 183 It's not a special DNSKEY RRSet, just a way of describing the 184 validation requirements for that RRSet. 186 N.B. A DNSKEY with the REVOKE bit set has a different fingerprint 187 than one without the bit set. This affects the matching of a DNSKEY 188 to DS records in the parent, or the fingerprint stored at a resolver 189 used to configure a trust point. 191 In the given example, the attacker could revoke B because it has 192 knowledge of B's private key, but could not revoke A. 194 2.2. Add Hold-Down 196 Assume two trust point keys A and B. Assume that B has been 197 compromised. An attacker could generate and add a new trust anchor 198 key - C (by adding C to the DNSKEY RRSet and signing it with B), and 199 then invalidate the compromised key. This would result in the both 200 the attacker and owner being able to sign data in the zone and have 201 it accepted as valid by resolvers. 203 To mitigate, but not completely solve, this problem, we add a hold- 204 down time to the addition of the trust anchor. When the resolver 205 sees a new SEP key in a validated trust point DNSKEY RRSet, the 206 resolver starts an acceptance timer, and remembers all the keys that 207 validated the RRSet. If the resolver ever sees the DNSKEY RRSet 208 without the new key but validly signed, it stops the acceptance 209 process and resets the acceptance timer. If all of the keys which 210 were originally used to validate this key are revoked prior to the 211 timer expiring, the resolver stops the acceptance process and resets 212 the timer. 214 Once the timer expires, the new key will be added as a trust anchor 215 the next time the validated RRSet with the new key is seen at the 216 resolver. The resolver MUST NOT treat the new key as a trust anchor 217 until the hold down time expires AND it has retrieved and validated a 218 DNSKEY RRSet after the hold down time which contains the new key. 220 N.B.: Once the resolver has accepted a key as a trust anchor, the key 221 MUST be considered a valid trust anchor by that resolver until 222 explictly revoked as described above. 224 In the given example, the zone owner can recover from a compromise by 225 revoking B and adding a new key D and signing the DNSKEY RRSet with 226 both A and B. 228 The reason this does not completely solve the problem has to do with 229 the distributed nature of DNS. The resolver only knows what it sees. 231 A determined attacker who holds one compromised key could keep a 232 single resolver from realizing that key had been compromised by 233 intercepting 'real' data from the originating zone and substituting 234 their own (e.g. using the example, signed only by B). This is no 235 worse than the current situation assuming a compromised key. 237 2.3. Remove Hold-down 239 A new key which has been seen by the resolver, but hasn't reached 240 it's add hold-down time, MAY be removed from the DNSKEY RRSet by the 241 zone owner. If the resolver sees a validated DNSKEY RRSet without 242 this key, it waits for the remove hold-down time and then, if the key 243 hasn't reappeared, SHOULD discard any information about the key. 245 2.4. Active Refresh 247 A resolver which has been configured for automatic update of keys 248 from a particular trust point MUST query that trust point (e.g. do a 249 lookup for the DNSKEY RRSet and related RRSIG records) no less often 250 than the lesser of 15 days or half the original TTL for the DNSKEY 251 RRSet or half the RRSIG expiration interval. The expiration interval 252 is the amount of time from when the RRSIG was last retrieved until 253 the expiration time in the RRSIG. 255 If the query fails, the resolver MUST repeat the query until 256 satisfied no more often than once an hour and no less often than the 257 lesser of 1 day or 10% of the original TTL or 10% of the original 258 expiration interval. 260 2.5. Resolver Parameters 262 2.5.1. Add Hold-Down Time 264 The add hold-down time is 30 days or the expiration time of the TTL 265 of the first trust point DNSKEY RRSet which contained the key, 266 whichever is greater. This ensures that at least two validated 267 DNSKEY RRSets which contain the new key MUST be seen by the resolver 268 prior to the key's acceptance. 270 2.5.2. Remove Hold-Down Time 272 The remove hold-down time is 30 days. 274 2.5.3. Minimum Trust Anchors per Trust Point 276 A compliant resolver MUST be able to manage at least five SEP keys 277 per trust point. 279 3. Changes to DNSKEY RDATA Wire Format 281 Bit n [msj2] of the DNSKEY Flags field is designated as the 'REVOKE' 282 flag. If this bit is set to '1', AND the resolver sees an 283 RRSIG(DNSKEY) signed by the associated key, then the resolver MUST 284 consider this key permanently invalid for all purposes except for 285 validing the revocation. 287 4. State Table 289 The most important thing to understand is the resolver's view of any 290 key at a trust point. The following state table describes that view 291 at various points in the key's lifetime. The table is a normative 292 part of this specification. The initial state of the key is 'Start'. 293 The resolver's view of the state of the key changes as various events 294 occur. 296 [msj1] This is the state of a trust point key as seen from the 297 resolver. The column on the left indicates the current state. The 298 header at the top shows the next state. The intersection of the two 299 shows the event that will cause the state to transition from the 300 current state to the next. 302 NEXT STATE 303 -------------------------------------------------- 304 FROM |Start |AddPend |Valid |Missing|Revoked|Removed| 305 ---------------------------------------------------------- 306 Start | |NewKey | | | | | 307 ---------------------------------------------------------- 308 AddPend |KeyRem | |AddTime| | | 309 ---------------------------------------------------------- 310 Valid | | | |KeyRem |Revbit | | 311 ---------------------------------------------------------- 312 Missing | | |KeyPres| |Revbit | | 313 ---------------------------------------------------------- 314 Revoked | | | | | |RemTime| 315 ---------------------------------------------------------- 316 Removed | | | | | | | 317 ---------------------------------------------------------- 319 4.1. Events 320 NewKey The resolver sees a valid DNSKEY RRSet with a new SEP key. 321 That key will become a new trust anchor for the named trust point 322 after its been present in the RRSet for at least 'add time'. 324 KeyPres The key has returned to the valid DNSKEY RRSet. 325 KeyRem The resolver sees a valid DNSKEY RRSet that does not contain 326 this key. 327 AddTime The key has been in every valid DNSKEY RRSet seen for at 328 least the 'add time'. 329 RemTime A revoked key has been missing from the trust point DNSKEY 330 RRSet for sufficient time to be removed from the trust set. 331 RevBit The key has appeared in the trust anchor DNSKEY RRSet with its 332 "REVOKED" bit set, and there is an RRSig over the DNSKEY RRSet 333 signed by this key. 335 4.2. States 336 Start The key doesn't yet exist as a trust anchor at the resolver. 337 It may or may not exist at the zone server, but hasn't yet been 338 seen at the resolver. 339 AddPend The key has been seen at the resolver, has its 'SEP' bit set, 340 and has been included in a validated DNSKEY RRSet. There is a 341 hold-down time for the key before it can be used as a trust 342 anchor. 343 Valid The key has been seen at the resolver and has been included in 344 all validated DNSKEY RRSets from the time it was first seen up 345 through the hold-down time. It is now valid for verifying RRSets 346 that arrive after the hold down time. Clarification: The DNSKEY 347 RRSet does not need to be continuously present at the resolver 348 (e.g. its TTL might expire). If the RRSet is seen, and is 349 validated (i.e. verifies against an existing trust anchor), this 350 key MUST be in the RRSet otherwise a 'KeyRem' event is triggered. 351 Missing This is an abnormal state. The key remains as a valid trust 352 point key, but was not seen at the resolver in the last validated 353 DNSKEY RRSet. This is an abnormal state because the zone operator 354 should be using the REVOKE bit prior to removal. [Discussion 355 item: Should a missing key be considered revoked after some period 356 of time?] 357 Revoked This is the state a key moves to once the resolver sees an 358 RRSIG(DNSKEY) signed by this key where that DNSKEY RRSet contains 359 this key with its REVOKE bit set to '1'. Once in this state, this 360 key MUST permanently be considered invalid as a trust anchor. 361 Removed After a fairly long hold-down time, information about this 362 key may be purged from the resolver. A key in the removed state 363 MUST NOT be considered a valid trust anchor. 365 4.3. Trust Point Deletion 367 A trust point which has all of its trust anchors revoked is 368 considered deleted and is treated as if the trust point was never 369 configured. If there are no superior trust points, data at and below 370 the deleted trust point are considered insecure. If there ARE 371 superior trust points, data at and below the deleted trust point are 372 evaluated with respect to the superior trust point. 374 To delete a trust point which is subordinate to another configured 375 trust point (e.g. example.com to .com) requires some juggling of the 376 data. The specific process is a) generate a new DNSKEY and DS record 377 and provide the DS record to the parent along with DS records for the 378 old keys; b) once the parent has published the DSs, add the new 379 DNSKEY to the RRSet and revoke ALL of the old keys at the same time 380 while signing the DNSKEY RRSet with all of the old and new keys; c) 381 after 30 days remove the old, revoked keys and any corresponding DS 382 records in the parent. 384 Revoking the old trust point keys at the same time as adding new keys 385 that chain to a superior trust prevents the resolver from adding the 386 new keys as trust anchors. Adding DS records for the old keys avoids 387 a race condition where either the subordinate zone becomes unsecure 388 (because the trust point was deleted) or becomes bogus (because it 389 didn't chain to the superior zone). 391 Alternately, a trust point which is subordinate to another configured 392 trust point MAY be deleted by a resolver after 180 days where such 393 trust point validly chains to a superior trust point. The decision 394 to delete the subordinate trust anchor is a local configuration 395 decision. Once the subordinate trust point is deleted, validation of 396 the subordinate zone is dependent on validating the chain of trust to 397 the superior trust point. 399 5. Scenarios 401 The suggested model for operation is to have one active key and one 402 stand-by key at each trust point. The active key will be used to 403 sign the DNSKEY RRSet. The stand-by key will not normally sign this 404 RRSet, but the resolver will accept it as a trust anchor if/when it 405 sees the signature on the trust point DNSKEY RRSet. 407 Since the stand-by key is not in active signing use, the associated 408 private key may (and SHOULD) be provided with additional protections 409 not normally available to a key that must be used frequently. E.g. 410 locked in a safe, split among many parties, etc. Notionally, the 411 stand-by key should be less subject to compromise than an active key, 412 but that will be dependent on operational concerns not addressed 413 here. 415 5.1. Adding A Trust Anchor 417 Assume an existing trust anchor key 'A'. 419 1. Generate a new key pair. 420 2. Create a DNSKEY record from the key pair and set the SEP and Zone 421 Key bits. 422 3. Add the DNSKEY to the RRSet. 423 4. Sign the DNSKEY RRSet ONLY with the existing trust anchor key - 424 'A'. 425 5. Wait a while. 427 5.2. Deleting a Trust Anchor 429 Assume existing trust anchors 'A' and 'B' and that you want to revoke 430 and delete 'A'. 431 1. Set the revolcation bit on key 'A'. 432 2. Sign the DNSKEY RRSet with both 'A' and 'B'. 433 'A' is now revoked. The operator SHOULD include the revoked 'A' in 434 the RRSet for at least the remove hold-down time, but then may remove 435 it from the DNSKEY RRSet. 437 5.3. Key Roll-Over 439 Assume existing keys A and B. 'A' is actively in use (i.e. has been 440 signing the DNSKEY RRSet.) 'B' was the stand-by key. (i.e. has been 441 in the DNSKEY RRSet and is a valid trust anchor, but wasn't being 442 used to sign the RRSet.) 443 1. Generate a new key pair 'C'. 444 2. Add 'C' to the DNSKEY RRSet. 445 3. Set the revocation bit on key 'A'. 446 4. Sign the RRSet with 'A' and 'B'. 447 'A' is now revoked, 'B' is now the active key, and 'C' will be the 448 stand-by key once the hold-down expires. The operator SHOULD include 449 the revoked 'A' in the RRSet for at least the remove hold-down time, 450 but may then remove it from the DNSKEY RRSet. 452 5.4. Active Key Compromised 454 This is the same as the mechanism for Key Roll-Over (Section 5.3) 455 above assuming 'A' is the active key. 457 5.5. Stand-by Key Compromised 459 Using the same assumptions and naming conventions as Key Roll-Over 460 (Section 5.3) above: 461 1. Generate a new key pair 'C'. 462 2. Add 'C' to the DNSKEY RRSet. 463 3. Set the revocation bit on key 'B'. 464 4. Sign the RRSet with 'A' and 'B'. 465 'B' is now revoked, 'A' remains the active key, and 'C' will be the 466 stand-by key once the hold-down expires. 'B' SHOULD continue to be 467 included in the RRSet for the remove hold-down time. 469 6. IANA Considerations 471 The IANA will need to assign a bit in the DNSKEY flags field (see 472 section 4.3 of [RFC3755]) for the REVOKE bit. There are no other 473 IANA actions required. 475 7. Security Considerations 477 7.1. Key Ownership vs Acceptance Policy 479 The reader should note that, while the zone owner is responsible 480 creating and distributing keys, it's wholly the decision of the 481 resolver owner as to whether to accept such keys for the 482 authentication of the zone information. This implies the decision 483 update trust anchor keys based on trust for a current trust anchor 484 key is also the resolver owner's decision. 486 The resolver owner (and resolver implementers) MAY choose to permit 487 or prevent key status updates based on this mechanism for specific 488 trust points. If they choose to prevent the automated updates, they 489 will need to establish a mechanism for manual or other out-of-band 490 updates outside the scope of this document. 492 7.2. Multiple Key Compromise 494 This scheme permits recovery as long as at least one valid trust 495 anchor key remains uncompromised. E.g. if there are three keys, you 496 can recover if two of them are compromised. The zone owner should 497 determine their own level of comfort with respect to the number of 498 active valid trust anchors in a zone and should be prepared to 499 implement recovery procedures once they detect a compromise. A 500 manual or other out-of-band update of all resolvers will be required 501 if all trust anchor keys at a trust point are compromised. 503 7.3. Dynamic Updates 505 Allowing a resolver to update its trust anchor set based in-band key 506 information is potentially less secure than a manual process. 507 However, given the nature of the DNS, the number of resolvers that 508 would require update if a trust anchor key were compromised, and the 509 lack of a standard management framework for DNS, this approach is no 510 worse than the existing situation. 512 8. Normative References 514 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 515 Requirement Levels", BCP 14, RFC 2119, March 1997. 517 [RFC2535] Eastlake, D., "Domain Name System Security Extensions", 518 RFC 2535, March 1999. 520 [RFC3755] Weiler, S., "Legacy Resolver Compatibility for Delegation 521 Signer (DS)", RFC 3755, May 2004. 523 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 524 Rose, "DNS Security Introduction and Requirements", 525 RFC 4033, March 2005. 527 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 528 Rose, "Resource Records for the DNS Security Extensions", 529 RFC 4034, March 2005. 531 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 532 Rose, "Protocol Modifications for the DNS Security 533 Extensions", RFC 4035, March 2005. 535 Editorial Comments 537 [msj1] msj: N.B. This table is preliminary and will be revised to 538 match implementation experience. For example, should there 539 be a state for "Add hold-down expired, but haven't seen the 540 new RRSet"? 542 [msj2] msj: To be assigned. 544 Author's Address 546 Michael StJohns 547 Nominum, Inc. 548 2385 Bay Road 549 Redwood City, CA 94063 550 USA 552 Phone: +1-301-528-4729 553 Email: Mike.StJohns@nominum.com 554 URI: www.nominum.com 556 Intellectual Property Statement 558 The IETF takes no position regarding the validity or scope of any 559 Intellectual Property Rights or other rights that might be claimed to 560 pertain to the implementation or use of the technology described in 561 this document or the extent to which any license under such rights 562 might or might not be available; nor does it represent that it has 563 made any independent effort to identify any such rights. 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Please address the information to the IETF at 578 ietf-ipr@ietf.org. 580 Disclaimer of Validity 582 This document and the information contained herein are provided on an 583 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 584 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET 585 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, 586 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE 587 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 588 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 590 Copyright Statement 592 Copyright (C) The Internet Society (2006). This document is subject 593 to the rights, licenses and restrictions contained in BCP 78, and 594 except as set forth therein, the authors retain all their rights. 596 Acknowledgment 598 Funding for the RFC Editor function is currently provided by the 599 Internet Society.