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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Jeong 3 Internet-Draft Sungkyunkwan University 4 Obsoletes: 6106 (if approved) S. Park 5 Intended status: Standards Track Samsung Electronics 6 Expires: September 15, 2016 L. Beloeil 7 France Telecom R&D 8 S. Madanapalli 9 iRam Technologies 10 March 14, 2016 12 IPv6 Router Advertisement Options for DNS Configuration 13 draft-ietf-6man-rdnss-rfc6106bis-10 15 Abstract 17 This document specifies IPv6 Router Advertisement options to allow 18 IPv6 routers to advertise a list of DNS recursive server addresses 19 and a DNS Search List to IPv6 hosts. 21 This document obsoletes RFC 6106 and allows a higher default value of 22 the lifetime of the RA DNS options to avoid the frequent expiry of 23 the options on links with a relatively high rate of packet loss. 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 September 15, 2016. 48 Copyright Notice 49 Copyright (c) 2016 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 Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.1. Applicability Statements . . . . . . . . . . . . . . . . . 3 66 1.2. Coexistence of RA Options and DHCP Options for DNS 67 Configuration . . . . . . . . . . . . . . . . . . . . . . 4 68 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 69 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 70 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 71 5. Neighbor Discovery Extension . . . . . . . . . . . . . . . . . 5 72 5.1. Recursive DNS Server Option . . . . . . . . . . . . . . . 6 73 5.2. DNS Search List Option . . . . . . . . . . . . . . . . . . 7 74 5.3. Procedure of DNS Configuration . . . . . . . . . . . . . . 8 75 5.3.1. Procedure in IPv6 Host . . . . . . . . . . . . . . . . 8 76 5.3.2. Warnings for DNS Options Configuration . . . . . . . . 9 77 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 78 6.1. Security Threats . . . . . . . . . . . . . . . . . . . . . 9 79 6.2. Recommendations . . . . . . . . . . . . . . . . . . . . . 10 80 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 81 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 82 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 83 9.1. Normative References . . . . . . . . . . . . . . . . . . . 11 84 9.2. Informative References . . . . . . . . . . . . . . . . . . 12 85 Appendix A. Changes from RFC 6106 . . . . . . . . . . . . . . . . 13 87 1. Introduction 89 The purpose of this document is to standardize an IPv6 Router 90 Advertisement (RA) option for DNS Recursive Server Addresses used for 91 the DNS name resolution in IPv6 hosts. This RA option was originally 92 specified in an earlier Experimental specification [RFC5006] and was 93 later published as a Standards Track in [RFC6106]. This document 94 obsoletes [RFC6106], allowing a higher default value of the lifetime 95 of the RA DNS options to avoid the frequent expiry of the options on 96 links with a relatively high rate of packet loss, and also making 97 additional clarifications, see Appendix A for details. 99 Neighbor Discovery (ND) for IP version 6 and IPv6 Stateless Address 100 Autoconfiguration (SLAAC) provide ways to configure either fixed or 101 mobile nodes with one or more IPv6 addresses, default routers, and 102 some other parameters [RFC4861][RFC4862]. Most Internet names are 103 identified by using a DNS name. The two RA options defined in this 104 document provide the DNS information needed for an IPv6 host to reach 105 Internet names. 107 It is infeasible to manually configure nomadic hosts each time they 108 connect to a different network. While a one-time static 109 configuration is possible, it is generally not desirable on general- 110 purpose hosts such as laptops. For instance, locally defined name 111 spaces would not be available to the host if it were to run its own 112 recursive name server directly connected to the global DNS. 114 The DNS information can also be provided through DHCPv6 [RFC3315] 115 [RFC3736][RFC3646]. However, the access to DNS is a fundamental 116 requirement for almost all hosts, so IPv6 stateless autoconfiguration 117 cannot stand on its own as an alternative deployment model in any 118 practical network without any support for DNS configuration. 120 These issues are not pressing in dual-stack networks as long as a DNS 121 server is available on the IPv4 side, but they become more critical 122 with the deployment of IPv6-only networks. As a result, this 123 document defines a mechanism based on IPv6 RA options to allow IPv6 124 hosts to perform the automatic DNS configuration. 126 1.1. Applicability Statements 128 RA-based DNS configuration is a useful alternative in networks where 129 an IPv6 host's address is autoconfigured through IPv6 stateless 130 address autoconfiguration and where there is either no DHCPv6 131 infrastructure at all or some hosts do not have a DHCPv6 client. The 132 intention is to enable the full configuration of basic networking 133 information for hosts without requiring DHCPv6. However, for 134 networks that need to distribute additional information, DHCPv6 is 135 likely to be employed. In these networks, RA-based DNS configuration 136 may not be needed. 138 RA-based DNS configuration allows an IPv6 host to acquire the DNS 139 configuration (i.e., DNS recursive server addresses and DNS Search 140 List) for the link(s) to which the host is connected. Furthermore, 141 the host learns this DNS configuration from the same RA message that 142 provides configuration information for the link. 144 The advantages and disadvantages of the RA-based approach are 145 discussed in [RFC4339] along with other approaches, such as the DHCP 146 and well-known anycast address approaches. 148 1.2. Coexistence of RA Options and DHCP Options for DNS Configuration 150 Two protocols exist to configure the DNS information on a host, the 151 Router Advertisement options specified in this document and the 152 DHCPv6 options specified in [RFC3646]. They can be used together. 153 The rules governing the decision to use stateful configuration 154 mechanisms are specified in [RFC4861]. Hosts conforming to this 155 specification MUST extract DNS information from Router Advertisement 156 messages, unless static DNS configuration has been specified by the 157 user. If there is DNS information available from multiple Router 158 Advertisements and/or from DHCP, the host MUST maintain an ordered 159 list of this information as specified in Section 5.3.1. 161 2. Requirements Language 163 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 164 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 165 document are to be interpreted as described in [RFC2119]. 167 3. Terminology 169 This document uses the terminology defined in [RFC4861] and 170 [RFC4862]. In addition, four new terms are defined below: 172 o Recursive DNS Server (RDNSS): Server that provides a recursive DNS 173 resolution service for translating domain names into IP addresses 174 or resolving PTR records, as defined in [RFC1034] and [RFC1035]. 176 o RDNSS Option: IPv6 RA option to deliver the RDNSS information to 177 IPv6 hosts [RFC4861]. 179 o DNS Search List (DNSSL): The list of DNS suffix domain names used 180 by IPv6 hosts when they perform DNS query searches for short, 181 unqualified domain names. 183 o DNSSL Option: IPv6 RA option to deliver the DNSSL information to 184 IPv6 hosts. 186 o DNS Repository: Two data structures for managing DNS Configuration 187 Information in the IPv6 protocol stack in addition to Neighbor 188 Cache and Destination Cache for Neighbor Discovery [RFC4861]. The 189 first data structure is the DNS Server List for RDNSS addresses 190 and the second is the DNS Search List for DNS search domain names. 192 o Resolver Repository: Configuration repository with RDNSS addresses 193 and a DNS Search List that a DNS resolver on the host uses for DNS 194 name resolution; for example, the Unix resolver file (i.e., /etc/ 195 resolv.conf) and Windows registry. 197 4. Overview 199 This document standardizes the ND option called the RDNSS option 200 defined in [RFC6106] that contains the addresses of recursive DNS 201 servers. This document also standardizes the ND option called the 202 DNSSL option defined in [RFC6106] that contains the Domain Search 203 List. This is to maintain parity with the DHCPv6 options and to 204 ensure that there is necessary functionality to determine the search 205 domains. 207 The existing ND message (i.e., Router Advertisement) is used to carry 208 this information. An IPv6 host can configure the IPv6 addresses of 209 one or more RDNSSes via RA messages. Through the RDNSS and DNSSL 210 options, along with the prefix information option based on the ND 211 protocol ([RFC4861] and [RFC4862]), an IPv6 host can perform the 212 network configuration of its IPv6 address and the DNS information 213 simultaneously without needing DHCPv6 for the DNS configuration. The 214 RA options for RDNSS and DNSSL can be used on the network that 215 supports the use of ND. 217 This approach requires the manual configuration or other automatic 218 mechanisms (e.g., DHCPv6 or vendor proprietary configuration 219 mechanisms) to configure the DNS information in routers sending the 220 advertisements. The automatic configuration of RDNSS addresses and a 221 DNS Search List in routers is out of scope for this document. 223 5. Neighbor Discovery Extension 225 The IPv6 DNS configuration mechanism in this document needs two ND 226 options in Neighbor Discovery: (i) the Recursive DNS Server (RDNSS) 227 option and (ii) the DNS Search List (DNSSL) option. 229 5.1. Recursive DNS Server Option 231 The RDNSS option contains one or more IPv6 addresses of recursive DNS 232 servers. All of the addresses share the same Lifetime value. If it 233 is desirable to have different Lifetime values, multiple RDNSS 234 options can be used. Figure 1 shows the format of the RDNSS option. 236 0 1 2 3 237 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 239 | Type | Length | Reserved | 240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 241 | Lifetime | 242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 243 | | 244 : Addresses of IPv6 Recursive DNS Servers : 245 | | 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 Figure 1: Recursive DNS Server (RDNSS) Option Format 250 Fields: 251 Type 8-bit identifier of the RDNSS option type as assigned 252 by the IANA: 25 254 Length 8-bit unsigned integer. The length of the option 255 (including the Type and Length fields) is in units of 256 8 octets. The minimum value is 3 if one IPv6 address 257 is contained in the option. Every additional RDNSS 258 address increases the length by 2. The Length field 259 is used by the receiver to determine the number of 260 IPv6 addresses in the option. 262 Lifetime 32-bit unsigned integer. The maximum time in 263 seconds (relative to the time the packet is received) 264 over which these RDNSS addresses MAY be used for name 265 resolution. The value of Lifetime SHOULD by default 266 be at least 3 * MaxRtrAdvInterval where 267 MaxRtrAdvInterval is the Maximum RA Interval defined 268 in [RFC4861]. A value of all one bits (0xffffffff) 269 represents infinity. A value of zero means that the 270 RDNSS addresses MUST no longer be used. 272 Addresses of IPv6 Recursive DNS Servers 273 One or more 128-bit IPv6 addresses of the recursive 274 DNS servers. The number of addresses is determined 275 by the Length field. That is, the number of 276 addresses is equal to (Length - 1) / 2. 278 Note: The addresses for recursive DNS servers in the RDNSS option 279 MAY be link-local addresses. Such link-local addresses SHOULD be 280 registered into the resolver repository along with the 281 corresponding link zone indices of the links that receive the 282 RDNSS option(s) for them. The link-local addresses MAY be 283 represented with their link zone indices in the textual format for 284 scoped addresses as described in [RFC4007]. When a resolver sends 285 a DNS query message to an RDNSS with a link-local address, it MUST 286 use the corresponding link. 288 5.2. DNS Search List Option 290 The DNSSL option contains one or more domain names of DNS suffixes. 291 All of the domain names share the same Lifetime value. If it is 292 desirable to have different Lifetime values, multiple DNSSL options 293 can be used. Figure 2 shows the format of the DNSSL option. 295 0 1 2 3 296 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 298 | Type | Length | Reserved | 299 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 300 | Lifetime | 301 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 302 | | 303 : Domain Names of DNS Search List : 304 | | 305 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 307 Figure 2: DNS Search List (DNSSL) Option Format 309 Fields: 310 Type 8-bit identifier of the DNSSL option type as assigned 311 by the IANA: 31 313 Length 8-bit unsigned integer. The length of the option 314 (including the Type and Length fields) is in units of 315 8 octets. The minimum value is 2 if at least one 316 domain name is contained in the option. The Length 317 field is set to a multiple of 8 octets to accommodate 318 all the domain names in the field of Domain Names of 319 DNS Search List. 321 Lifetime 32-bit unsigned integer. The maximum time in 322 seconds (relative to the time the packet is received) 323 over which these DNSSL domain names MAY be used for 324 name resolution. The Lifetime value has the same 325 semantics as with the RDNSS option. That is, 326 Lifetime SHOULD by default be at least 327 3 * MaxRtrAdvInterval. A value of all one bits 328 (0xffffffff) represents infinity. A value of zero 329 means that the DNSSL domain names MUST no longer be 330 used. 332 Domain Names of DNS Search List 333 One or more domain names of DNS Search List that MUST 334 be encoded as described in Section 3.1 of [RFC1035]. 335 By this technique, each domain name is represented as 336 a sequence of labels ending in a zero octet, defined 337 as domain name representation. For more than one 338 domain name, the corresponding domain name 339 representations are concatenated as they are. Note 340 that for the simple decoding, the domain names MUST 341 NOT be encoded in a compressed form, as described in 342 Section 4.1.4 of [RFC1035]. Because the size of this 343 field MUST be a multiple of 8 octets, for the minimum 344 multiple including the domain name representations, 345 the remaining octets other than the encoding parts of 346 the domain name representations MUST be padded with 347 zeros. 349 5.3. Procedure of DNS Configuration 351 The procedure of DNS configuration through the RDNSS and DNSSL 352 options is the same as with any other ND option [RFC4861]. 354 5.3.1. Procedure in IPv6 Host 356 When an IPv6 host receives DNS options (i.e., RDNSS option and DNSSL 357 option) through RA messages, it processes the options as follows: 359 o The validity of DNS options is checked with the Length field; that 360 is, the value of the Length field in the RDNSS option is greater 361 than or equal to the minimum value (3), and satisfies that (Length 362 - 1) % 2 == 0. The value of the Length field in the DNSSL option 363 is greater than or equal to the minimum value (2). Also, the 364 validity of the RDNSS option is checked with the "Addresses of 365 IPv6 Recursive DNS Servers" field; that is, the addresses should 366 be unicast addresses. 368 o If the DNS options are valid, the host SHOULD copy the values of 369 the options into the DNS Repository and the Resolver Repository in 370 order. Otherwise, the host MUST discard the options. 372 In the case where the DNS options of RDNSS and DNSSL can be obtained 373 from multiple sources, such as RA and DHCP, the IPv6 host SHOULD keep 374 some DNS options from all sources. Unless explicitly specified for 375 the discovery mechanism, the exact number of addresses and domain 376 names to keep is a matter of local policy and implementation choice 377 as a local configuration option. However, in the case of multiple 378 sources, the ability to store a total of at least three RDNSS 379 addresses (or DNSSL domain names) from the multiple sources is 380 RECOMMENDED. The DNS options from Router Advertisements and DHCP 381 SHOULD be stored into the DNS Repository and Resolver Repository so 382 that information from DHCP appears there first and therefore takes 383 precedence. Thus, the DNS information from DHCP takes precedence 384 over that from RA for DNS queries. On the other hand, for DNS 385 options announced by RA, if some RAs use the Secure Neighbor 386 Discovery (SEND) protocol [RFC3971] for RA security, they MUST be 387 preferred over those that do not use SEND. Refer to Section 6 for 388 the detailed discussion on SEND for RA DNS options. 390 5.3.2. Warnings for DNS Options Configuration 392 There are two warnings for DNS options configuration: (i) warning for 393 multiple sources of DNS options and (ii) warning for multiple network 394 interfaces. First, in the case of multiple sources for DNS options 395 (e.g., RA and DHCP), an IPv6 host can configure its IP addresses from 396 these sources. In this case, it is not possible to control how the 397 host uses DNS information and what source addresses it uses to send 398 DNS queries. As a result, configurations where different information 399 is provided by different sources may lead to problems. Therefore, 400 the network administrator needs to configure different DNS options in 401 the multiple sources in order to minimize the impact of such problems 402 [DHCPv6-SLAAC]. 404 Second, if different DNS information is provided on different network 405 interfaces, this can lead to inconsistent behavior. The IETF worked 406 on solving this problem for both DNS and other information obtained 407 by multiple interfaces [RFC6418][RFC6419], and standardized the 408 solution for RDNSS selection for multi-interfaced nodes in [RFC6731], 409 which is based on DHCP. 411 6. Security Considerations 413 In this section, we analyze security threats related to DNS options 414 and then suggest recommendations to cope with such security threats. 416 6.1. Security Threats 418 For the RDNSS option, an attacker could send an RA with a fraudulent 419 RDNSS address, misleading IPv6 hosts into contacting an unintended 420 DNS server for DNS name resolution. Also, for the DNSSL option, an 421 attacker can let IPv6 hosts resolve a host name without a DNS suffix 422 into an unintended host's IP address with a fraudulent DNS Search 423 List. These attacks are similar to ND attacks specified in [RFC4861] 424 that use Redirect or Neighbor Advertisement messages to redirect 425 traffic to individual addresses of malicious parties. 427 However, the security of these RA options for DNS configuration does 428 not affect ND protocol security [RFC4861]. This is because learning 429 DNS information via the RA options cannot be worse than learning bad 430 router information via the RA options. Therefore, the vulnerability 431 of ND is not worse and is a subset of the attacks that any node 432 attached to a LAN can do. 434 6.2. Recommendations 436 The Secure Neighbor Discovery (SEND) protocol [RFC3971] is designed 437 as a security mechanism for ND. In this case, ND can use SEND to 438 allow all the ND options including the RDNSS and DNSSL options to be 439 automatically included in the signatures. Other approaches specified 440 in [RFC4861] can be used for securing the RA options for DNS 441 configuration. 443 It is common for network devices such as switches to include 444 mechanisms to block unauthorized ports from running a DHCPv6 server 445 to provide protection from rogue DHCPv6 servers [RFC7610]. That 446 means that an attacker on other ports cannot insert bogus DNS servers 447 using DHCPv6. The corresponding technique for network devices is 448 RECOMMENDED to block rogue Router Advertisement messages [RFC6104] 449 including the RDNSS and DNSSL options from unauthorized nodes. 451 An attacker may provide a bogus DNS Search List option in order to 452 cause the victim to send DNS queries to a specific DNS server when 453 the victim queries non-FQDNs (fully qualified domain names). For 454 this attack, the DNS resolver in IPv6 hosts can mitigate the 455 vulnerability with the recommendations mentioned in [RFC1535], 456 [RFC1536], and [RFC3646]. 458 7. IANA Considerations 460 The RDNSS option defined in this document uses the IPv6 Neighbor 461 Discovery Option type defined in RFC 6106 [RFC6106], which was 462 assigned by the IANA as follows: 464 Option Name Type 465 Recursive DNS Server Option 25 467 The DNSSL option defined in this document uses the IPv6 Neighbor 468 Discovery Option type defined in RFC 6106 [RFC6106], which was 469 assigned by the IANA as follows: 471 Option Name Type 472 DNS Search List Option 31 474 These options have been registered in the "Internet Control Message 475 Protocol version 6 (ICMPv6) Parameters" registry (http:// 476 www.iana.org/assignments/icmpv6-parameters/ 477 icmpv6-parameters.xhtml#icmpv6-parameters-5). 479 8. Acknowledgements 481 This document has greatly benefited from inputs by Robert Hinden, 482 Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik 483 Nordmark, Dan Wing, Jari Arkko, Ben Campbell, Vincent Roca, Tony 484 Cheneau, Fernando Gont, Jen Linkova, Ole Troan, Mark Smith, Tatuya 485 Jinmei, Lorenzo Colitti, Tore Anderson, David Farmer, and Bing Liu. 486 The authors sincerely appreciate their contributions. 488 This document was supported by Institute for Information & 489 communications Technology Promotion (IITP) grant funded by the Korea 490 government (MSIP) [10041244, Smart TV 2.0 Software Platform]. 492 9. References 494 9.1. Normative References 496 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 497 Requirement Levels", BCP 14, RFC 2119, March 1997. 499 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. 500 Soliman, "Neighbor Discovery for IP version 6 501 (IPv6)", RFC 4861, September 2007. 503 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 504 Stateless Address Autoconfiguration", RFC 4862, 505 September 2007. 507 [RFC1035] Mockapetris, P., "Domain names - implementation and 508 specification", STD 13, RFC 1035, November 1987. 510 [RFC4007] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., 511 and B. Zill, "IPv6 Scoped Address Architecture", 512 RFC 4007, March 2005. 514 9.2. Informative References 516 [RFC1034] Mockapetris, P., "Domain names - concepts and 517 facilities", STD 13, RFC 1034, November 1987. 519 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, 520 C., and M. Carney, "Dynamic Host Configuration 521 Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. 523 [RFC3736] Droms, R., "Stateless Dynamic Host Configuration 524 Protocol (DHCP) Service for IPv6", RFC 3736, 525 April 2004. 527 [RFC3646] Droms, R., "DNS Configuration options for Dynamic 528 Host Configuration Protocol for IPv6 (DHCPv6)", 529 RFC 3646, December 2003. 531 [RFC5006] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, 532 "IPv6 Router Advertisement Option for DNS 533 Configuration", RFC 5006, September 2007. 535 [RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, 536 "IPv6 Router Advertisement Options for DNS 537 Configuration", RFC 6106, November 2010. 539 [RFC4339] Jeong, J., "IPv6 Host Configuration of DNS Server 540 Information Approaches", RFC 4339, February 2006. 542 [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, 543 "SEcure Neighbor Discovery (SEND)", RFC 3971, 544 March 2005. 546 [RFC6104] Chown, T. and S. Venaas, "Rogue IPv6 Router 547 Advertisement Problem Statement", RFC 6104, 548 February 2011. 550 [RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6- 551 Shield: Protecting against Rogue DHCPv6 Servers", 552 RFC 7610, August 2015. 554 [RFC1535] Gavron, E., "A Security Problem and Proposed 555 Correction With Widely Deployed DNS Software", 556 RFC 1535, October 1993. 558 [RFC1536] Kumar, A., Postel, J., Neuman, C., Danzig, P., and S. 559 Miller, "Common DNS Implementation Errors and 560 Suggested Fixes", RFC 1536, October 1993. 562 [DHCPv6-SLAAC] Liu, B., Jiang, S., Gong, X., Wang, W., and E. Rey, 563 "DHCPv6/SLAAC Interaction Problems on Address and DNS 564 Configuration", Work in Progress, February 2016. 566 [RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and 567 Provisioning Domains Problem Statement", RFC 6418, 568 November 2011. 570 [RFC6419] Wasserman, M. and P. Seite, "Current Practices for 571 Multiple-Interface Hosts", RFC 6419, November 2011. 573 [RFC6731] Savolainen, T., Kato, J., and T. Lemon, "Improved 574 Recursive DNS Server Selection for Multi-Interfaced 575 Nodes", RFC 6731, December 2012. 577 Appendix A. Changes from RFC 6106 579 The following changes were made from RFC 6106 "IPv6 Router 580 Advertisement Options for DNS Configuration": 582 o The generation of Router Solicitation to ensure that the RDNSS 583 information is fresh before the expiry of the RDNSS option is 584 removed in order to prevent multicast traffic on the link from 585 increasing. 587 o The lifetime's upper bound of 2 * MaxRtrAdvInterval was shown to 588 lead to the expiry of these options on links with a relatively 589 high rate of packet loss. This revision relaxes the upper bound 590 and sets a higher default value to avoid this problem. 592 o The addresses for recursive DNS servers in the RDNSS option can be 593 not only global addresses, but also link-local addresses. The 594 link-local addresses for RDNSSes should be registered into the 595 resolver repository along with the corresponding link zone 596 indices. 598 o The recommendation that at most three RDNSS addresses to maintain 599 by RDNSS options should be limited is removed. By this removal, 600 the number of RDNSSes to maintain is up to an implementer's local 601 policy. 603 o The recommendation that at most three DNS domains to maintain by 604 DNSSL options should be limited is removed. By this removal, when 605 the set of unique DNSSL values are not equivalent, none of them 606 are ignored for hostname lookups. 608 o The section of implementation considerations for RA DNS Options is 609 removed. 611 o The usage of the keywords of SHOULD and RECOMMENDED in RFC 2119 is 612 removed in the recommendation of using SEND for secure ND. 613 Instead of the keywords, SEND is specified as a possible solution 614 for secure ND. 616 Authors' Addresses 618 Jaehoon Paul Jeong 619 Department of Software 620 Sungkyunkwan University 621 2066 Seobu-Ro, Jangan-Gu 622 Suwon, Gyeonggi-Do 16419 623 Republic of Korea 625 Phone: +82 31 299 4957 626 Fax: +82 31 290 7996 627 EMail: pauljeong@skku.edu 628 URI: http://iotlab.skku.edu/people-jaehoon-jeong.php 630 Soohong Daniel Park 631 Software R&D Center 632 Samsung Electronics 633 Seoul R&D Campus D-Tower, 56, Seongchon-Gil, Seocho-Gu 634 Seoul 06765 635 Republic of Korea 637 EMail: soohong.park@samsung.com 639 Luc Beloeil 640 France Telecom R&D 641 42, rue des coutures 642 BP 6243 643 14066 CAEN Cedex 4 644 France 646 Phone: +33 2 40 44 97 40 647 EMail: luc.beloeil@orange-ftgroup.com 648 Syam Madanapalli 649 iRam Technologies 650 #H304, Shriram Samruddhi, Thubarahalli 651 Bangalore - 560066 652 India 654 EMail: smadanapalli@gmail.com