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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 3315 (Obsoleted by RFC 8415) -- Obsolete informational reference (is this intentional?): RFC 3736 (Obsoleted by RFC 8415) -- Obsolete informational reference (is this intentional?): RFC 5006 (Obsoleted by RFC 6106) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Jeong, Ed. 3 Internet-Draft Brocade/ETRI 4 Obsoletes: 5006 (if approved) S. Park 5 Intended status: Standards Track SAMSUNG Electronics 6 Expires: November 19, 2010 L. Beloeil 7 France Telecom R&D 8 S. Madanapalli 9 Ordyn Technologies 10 May 18, 2010 12 IPv6 Router Advertisement Options for DNS Configuration RFC 5006-bis 13 draft-ietf-6man-dns-options-bis-01 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 Status of This Memo 23 This Internet-Draft is submitted to IETF in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF), its areas, and its working groups. Note that 28 other groups may also distribute working documents as Internet- 29 Drafts. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 The list of current Internet-Drafts can be accessed at 37 http://www.ietf.org/ietf/1id-abstracts.txt. 39 The list of Internet-Draft Shadow Directories can be accessed at 40 http://www.ietf.org/shadow.html. 42 This Internet-Draft will expire on November 19, 2010. 44 Copyright Notice 46 Copyright (c) 2010 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 1.1. Applicability Statements . . . . . . . . . . . . . . . . . 3 63 1.2. Coexistence of RA Options and DHCP Options for DNS 64 Configuration . . . . . . . . . . . . . . . . . . . . . . 4 65 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 66 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 67 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 68 5. Neighbor Discovery Extension . . . . . . . . . . . . . . . . . 5 69 5.1. Recursive DNS Server Option . . . . . . . . . . . . . . . 5 70 5.2. DNS Search List Option . . . . . . . . . . . . . . . . . . 7 71 5.3. Procedure of DNS Configuration . . . . . . . . . . . . . . 8 72 5.3.1. Procedure in IPv6 Host . . . . . . . . . . . . . . . . 8 73 6. Implementation Considerations . . . . . . . . . . . . . . . . 9 74 6.1. DNS Repository Management . . . . . . . . . . . . . . . . 9 75 6.2. Synchronization between DNS Server List and Resolver 76 Repository . . . . . . . . . . . . . . . . . . . . . . . . 10 77 6.3. Synchronization between DNS Search List and Resolver 78 Repository . . . . . . . . . . . . . . . . . . . . . . . . 11 79 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 80 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 81 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 82 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 83 10.1. Normative References . . . . . . . . . . . . . . . . . . . 13 84 10.2. Informative References . . . . . . . . . . . . . . . . . . 14 86 1. Introduction 88 The purpose of this document is to standardize IPv6 Router 89 Advertisement (RA) option for DNS configuration in IPv6 hosts 90 specified in an earlier experimental specification [RFC5006] and also 91 to define a new RA option for Domain Name Search lists. 93 Neighbor Discovery (ND) for IP Version 6 and IPv6 Stateless Address 94 Autoconfiguration provide ways to configure either fixed or mobile 95 nodes with one or more IPv6 addresses, default routers and some other 96 parameters [RFC4861][RFC4862]. Most Internet services are identified 97 by using a DNS name. The two RA options defined in this document 98 provide the DNS information needed for an IPv6 host to reach Internet 99 services. 101 It is infeasible to manually configure nomadic hosts each time they 102 connect to a different network. While a one-time static 103 configuration is possible, it is generally not desirable on general- 104 purpose hosts such as laptops. For instance, locally defined name 105 spaces would not be available to the host if it were to run its own 106 name server software directly connected to the global DNS. 108 The DNS information can also be provided through DHCP 109 [RFC3315][RFC3736][RFC3646]. However, the access to DNS is a 110 fundamental requirement for almost all hosts, so IPv6 stateless 111 autoconfiguration cannot stand on its own as an alternative 112 deployment model in any practical network without any support for DNS 113 configuration. 115 These issues are not pressing in dual stack networks as long as a DNS 116 server is available on the IPv4 side, but become more critical with 117 the deployment of IPv6-only networks. As a result, this document 118 defines a mechanism based on IPv6 RA options to allow IPv6 hosts to 119 perform the automatic DNS configuration. 121 1.1. Applicability Statements 123 RA-based DNS configuration is a useful alternative in networks where 124 an IPv6 host's address is autoconfigured through IPv6 stateless 125 address autoconfiguration, and where there is either no DHCPv6 126 infrastructure at all or some hosts do not have a DHCPv6 client. The 127 intention is to enable the full configuration of basic networking 128 information for hosts without requiring DHCPv6. However, when in 129 many networks some additional information needs to be distributed, 130 those networks are likely to employ DHCPv6. In these networks RA- 131 based DNS configuration may not be needed. 133 RA-based DNS configuration allows an IPv6 host to acquire the DNS 134 configuration (i.e., DNS recursive server addresses and DNS search 135 list) for the link(s) to which the host is connected. Furthermore, 136 the host learns this DNS configuration from the same RA message that 137 provides configuration information for the link, thereby avoiding 138 also running DHCPv6. 140 The advantages and disadvantages of the RA-based approach are 141 discussed in [RFC4339] along with other approaches, such as the DHCP 142 and well-known anycast addresses approaches. 144 1.2. Coexistence of RA Options and DHCP Options for DNS Configuration 146 Two protocols exist to configure the DNS information on a host, the 147 Router Advertisement options described in this document and the 148 DHCPv6 options described in [RFC3646]. They can be used together. 149 The rules governing the decision to use stateful configuration 150 mechanisms are specified in [RFC4861]. Hosts conforming to this 151 specification MUST extract DNS information from Router Advertisement 152 messages, unless static DNS configuration has been specified by the 153 user. If there is DNS information available from multiple Router 154 Advertisements and/or from DHCP, the host MUST maintain an ordered 155 list of this information as specified in Section 5.3.1. 157 2. Requirements Language 159 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 160 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 161 document are to be interpreted as described in [RFC2119]. 163 3. Terminology 165 This document uses the terminology described in [RFC4861] and 166 [RFC4862]. In addition, four new terms are defined below: 168 o Recursive DNS Server (RDNSS): Server which provides a recursive 169 DNS resolution service for translating domain names into IP 170 addresses as defined in [RFC1034] and [RFC1035]. 172 o RDNSS Option: IPv6 RA option to deliver the RDNSS information to 173 IPv6 hosts [RFC4861]. 175 o DNS Search List (DNSSL): The list of DNS suffix domain names used 176 by IPv6 hosts when they perform DNS query searches for short, 177 unqualified domain names. 179 o DNSSL Option: IPv6 RA option to deliver the DNSSL information to 180 IPv6 hosts. 182 o DNS Repository: Two data structures for managing DNS Configuration 183 Information in the IPv6 protocol stack in addition to Neighbor 184 Cache and Destination Cache for Neighbor Discovery [RFC4861]. The 185 first data structure is the DNS Server List for RDNSS addresses 186 and the second is the DNS Search List for DNS search domain names. 188 o Resolver Repository: Configuration repository with RDNSS addresses 189 and a DNS search list that a DNS resolver on the host uses for DNS 190 name resolution; for example, the Unix resolver file (i.e., /etc/ 191 resolv.conf) and Windows registry. 193 4. Overview 195 This document standardizes the ND option called RDNSS option defined 196 in [RFC5006] that contains the addresses of recursive DNS servers. 197 This document also defines a new ND option called DNSSL option for 198 Domain Search List. This is to maintain parity with the DHCPv6 199 options and to ensure that there is necessary functionality to 200 determine the search domains. 202 Existing ND message (i.e., Router Advertisement) is used to carry 203 this information. An IPv6 host can configure the IPv6 addresses of 204 one or more RDNSSes via RA messages. Through the RDNSS and DNSSL 205 options, along with the prefix information option based on the ND 206 protocol ([RFC4861] and [RFC4862]), an IPv6 host can perform the 207 network configuration of its IPv6 address and the DNS information 208 simultaneously without needing DHCPv6 for the DNS configuration. The 209 RA options for RDNSS and DNSSL can be used on any network that 210 supports the use of ND. 212 This approach requires the manual configuration or other automatic 213 mechanisms (e.g., DHCPv6 or vendor proprietary configuration 214 mechanisms) to configure the DNS information in routers sending the 215 advertisements. The automatic configuration of RDNSS addresses and a 216 DNS search list in routers is out of scope for this document. 218 5. Neighbor Discovery Extension 220 The IPv6 DNS configuration mechanism in this document needs two new 221 ND options in Neighbor Discovery: (i) the Recursive DNS Server 222 (RDNSS) option and (ii) the DNS Search List (DNSSL) option. 224 5.1. Recursive DNS Server Option 226 The RDNSS option contains one or more IPv6 addresses of recursive DNS 227 servers. All of the addresses share the same lifetime value. If it 228 is desirable to have different lifetime values, multiple RDNSS 229 options can be used. Figure 1 shows the format of the RDNSS option. 231 0 1 2 3 232 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 1 233 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 | Type | Length | Reserved | 235 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 236 | Lifetime | 237 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 238 | | 239 : Addresses of IPv6 Recursive DNS Servers : 240 | | 241 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 243 Figure 1: Recursive DNS Server (RDNSS) Option Format 245 Fields: 246 Type 8-bit identifier of the RDNSS option type as assigned 247 by the IANA: 25 249 Length 8-bit unsigned integer. The length of the option 250 (including the Type and Length fields) is in units of 251 8 octets. The minimum value is 3 if one IPv6 address 252 is contained in the option. Every additional RDNSS 253 address increases the length by 2. The Length field 254 is used by the receiver to determine the number of 255 IPv6 addresses in the option. 257 Lifetime 32-bit unsigned integer. The maximum time, in 258 seconds (relative to the time the packet is sent), 259 over which this RDNSS address MAY be used for name 260 resolution. Hosts MAY send a Router Solicitation to 261 ensure the RDNSS information is fresh before the 262 interval expires. In order to provide fixed hosts 263 with stable DNS service and allow mobile hosts to 264 prefer local RDNSSes to remote RDNSSes, the value of 265 Lifetime should be at least as long as the Maximum RA 266 Interval (MaxRtrAdvInterval) in [RFC4861], and be at 267 most as long as two times MaxRtrAdvInterval; Lifetime 268 SHOULD be bounded as follows: MaxRtrAdvInterval <= 269 Lifetime <= 2*MaxRtrAdvInterval. A value of all one 270 bits (0xffffffff) represents infinity. A value of 271 zero means that the RDNSS address MUST no longer be 272 used. 274 Addresses of IPv6 Recursive DNS Servers 275 One or more 128-bit IPv6 addresses of the recursive 276 DNS servers. The number of addresses is determined 277 by the Length field. That is, the number of 278 addresses is equal to (Length - 1) / 2. 280 5.2. DNS Search List Option 282 The DNSSL option contains one or more domain names of DNS suffixes. 283 All of the domain names share the same lifetime value. If it is 284 desirable to have different lifetime values, multiple DNSSL options 285 can be used. Figure 2 shows the format of the DNSSL option. 287 0 1 2 3 288 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 1 289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 290 | Type | Length | Reserved | 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 292 | Lifetime | 293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 294 | | 295 : Domain Names of DNS Search List : 296 | | 297 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 299 Figure 2: DNS Search List (DNSSL) Option Format 301 Fields: 302 Type 8-bit identifier of the RDNSS option type as assigned 303 by the IANA: (TBD) 305 Length 8-bit unsigned integer. The length of the option 306 (including the Type and Length fields) is in units of 307 8 octets. The minimum value is 2 if at least one 308 domain name is contained in the option. The Length 309 field is set to a multiple of 8 octets to accommodate 310 all the domain names in the field of Domain Names of 311 DNS Search List. 313 Lifetime 32-bit unsigned integer. The maximum time, in 314 seconds (relative to the time the packet is sent), 315 over which this DNSSL domain name MAY be used for 316 name resolution. The Lifetime value has the same 317 semantics as with RDNSS option. That is, Lifetime 318 SHOULD be bounded as follows: MaxRtrAdvInterval <= 319 Lifetime <= 2*MaxRtrAdvInterval. A value of all one 320 bits (0xffffffff) represents infinity. A value of 321 zero means that the DNSSL domain name MUST no longer 322 be used. 324 Domain Names of DNS Search List 325 One or more domain names of DNS search list that MUST 326 be encoded in the non-compressed form, using the 327 technique described in Section 3.1 of [RFC1035]. The 328 size of this field is a multiple of 8 octets. The 329 remaining octets other than the encoding parts for 330 the domain names are padded with zeros. 332 Note: An RDNSS address or a DNSSL domain name MUST be used only as 333 long as both the RA router lifetime and the option lifetime have 334 not expired. The reason is that in the current network to which 335 an IPv6 host is connected, the RDNSS may not be currently 336 reachable, that the DNSSL domain name is not valid any more, or 337 that these options do not provide service to the host's current 338 address (e.g., due to network ingress filtering 339 [RFC2827][RFC5358]). 341 5.3. Procedure of DNS Configuration 343 The procedure of DNS configuration through the RDNSS and DNSSL 344 options is the same as with any other ND option [RFC4861]. 346 5.3.1. Procedure in IPv6 Host 348 When an IPv6 host receives DNS options (i.e., RDNSS option and DNSSL 349 option) through RA messages, it checks whether the options are valid 350 or not as follow: 352 o If the DNS options are valid, the host SHOULD copy the values of 353 the options into the DNS Repository and the Resolver Repository in 354 order; the value of the Length field in the RDNSS option is 355 greater than or equal to the minimum value (3) and also the value 356 of the Length field in the DNSSL option is greater than or equal 357 to the minimum value (2). 359 o If the DNS options are invalid, the host MUST discard the options; 360 for example, the Length field in the RDNSS option has a value less 361 than 3 or the Length field in the DNSSL option has a value less 362 than 2. 364 When the IPv6 host has gathered a sufficient number (e.g., three) of 365 RDNSS addresses (or DNS search domain names), it MAY ignore 366 additional RDNSS addresses (or DNS search domain names) within an 367 RDNSS (or DNSSL) option and/or additional RDNSS (or DNSSL) options 368 within an RA. 370 In the case where the DNS options of RDNSS and DNSSL can be obtained 371 from multiple sources, such as RA and DHCP, the IPv6 host can keep 372 some DNS options from RA and some from DHCP; for example, two RDNSS 373 addresses (or DNS search domain names) from RA and one RDNSS address 374 (or DNS search domain name) from DHCP. 376 6. Implementation Considerations 378 Note: This non-normative section gives some hints for implementing 379 the processing of the RDNSS and DNSSL options in an IPv6 host. 381 For the configuration and management of DNS information, the 382 advertised DNS configuration information can be stored and managed in 383 both the DNS Repository and the Resolver Repository. 385 In environments where the DNS information is stored in user space and 386 ND runs in the kernel, it is necessary to synchronize the DNS 387 information (i.e., RDNSS addresses and DNS search domain names) in 388 kernel space and the Resolver Repository in user space. For the 389 synchronization, an implementation where ND works in the kernel 390 should provide a write operation for updating DNS information from 391 the kernel to the Resolver Repository. One simple approach is to 392 have a daemon (or a program that is called at defined intervals) that 393 keeps monitoring the lifetimes of RDNSS addresses and DNS search 394 domain names all the time. Whenever there is an expired entry in the 395 DNS Repository, the daemon can delete the corresponding entry from 396 the Resolver Repository. 398 6.1. DNS Repository Management 400 For DNS repository management, the kernel or user-space process 401 (depending on where RAs are processed) should maintain two data 402 structures: (i) DNS Server List that keeps the list of RDNSS 403 addresses and (ii) DNS Search List that keeps the list of DNS search 404 domain names. Each entry in these two lists consists of a pair of an 405 RDNSS address (or DNSSL domain name) and Expiration-time as follows: 407 o RDNSS address for DNS Server List: IPv6 address of the Recursive 408 DNS Server, which is available for recursive DNS resolution 409 service in the network advertising the RDNSS option. 411 o DNSSL domain name for DNS Search List: DNS suffix domain names, 412 which is used to perform DNS query searches for short, unqualified 413 domain names in the network advertising the DNSSL option. 415 o Expiration-time for DNS Server List or DNS Search List: The time 416 when this entry becomes invalid. Expiration-time is set to the 417 value of the Lifetime field of the RDNSS option or DNSSL option 418 plus the current system time. Whenever a new RDNSS option with 419 the same address (or DNSSL option with the same domain name) is 420 received on the same interface as a previous RDNSS option (or 421 DNSSL option), this field is updated to have a new expiration 422 time. When Expiration-time becomes less than the current system 423 time, this entry is regarded as expired. 425 6.2. Synchronization between DNS Server List and Resolver Repository 427 When an IPv6 host receives the information of multiple RDNSS 428 addresses within a network (e.g., campus network and company network) 429 through an RA message with RDNSS option(s), it stores the RDNSS 430 addresses (in order) into both the DNS Server List and the Resolver 431 Repository. The processing of the RDNSS option(s) included in an RA 432 message is as follows: 434 Step (a): Receive and parse the RDNSS option(s). For the RDNSS 435 addresses in each RDNSS option, perform Step (b) through Step (d). 436 Note that Step (e) is performed whenever an entry expires in the 437 DNS Server List. 439 Step (b): For each RDNSS address, check the following: If the 440 RDNSS address already exists in the DNS Server List and the RDNSS 441 option's Lifetime field is set to zero, delete the corresponding 442 RDNSS entry from both the DNS Server List and the Resolver 443 Repository in order to prevent the RDNSS address from being used 444 any more for certain reasons in network management, e.g., the 445 termination of the RDNSS or a renumbering situation. The 446 processing of this RDNSS address is finished here. Otherwise, go 447 to Step (c). 449 Step (c): For each RDNSS address, if it already exists in the DNS 450 Server List, then just update the value of the Expiration-time 451 field according to the procedure specified in the second bullet of 452 Section 6.1. Otherwise, go to Step (d). 454 Step (d): For each RDNSS address, if it does not exist in the DNS 455 Server List, register the RDNSS address and lifetime with the DNS 456 Server List and then insert the RDNSS address in front of the 457 Resolver Repository. In the case where the data structure for the 458 DNS Server List is full of RDNSS entries, delete from the DNS 459 Server List the entry with the shortest expiration time (i.e., the 460 entry that will expire first). The corresponding RDNSS address is 461 also deleted from the Resolver Repository. In the order in the 462 RDNSS option, position the newly added RDNSS addresses in front of 463 the Resolver Repository so that the new RDNSS addresses may be 464 preferred according to their order in the RDNSS option for the DNS 465 name resolution. The processing of these RDNSS addresses is 466 finished here. Note that, in the case where there are several 467 routers advertising RDNSS option(s) in a subnet, the RDNSSes that 468 have been announced recently are preferred. 470 Step (e): Delete each expired entry from the DNS Server List, and 471 delete the RDNSS address corresponding to the entry from the 472 Resolver Repository. 474 6.3. Synchronization between DNS Search List and Resolver Repository 476 When an IPv6 host receives the information of multiple DNSSL domain 477 names within a network (e.g., campus network and company network) 478 through an RA message with DNSSL option(s), it stores the DNSSL 479 domain names (in order) into both the DNS Search List and the 480 Resolver Repository. The processing of the DNSSL option(s) included 481 in an RA message is as follows: 483 Step (a): Receive and parse the DNSSL option(s). For the DNSSL 484 domain names in each DNSSL option, perform Step (b) through Step 485 (d). Note that Step (e) is performed whenever an entry expires in 486 the DNS Search List. 488 Step (b): For each DNSSL domain name, check the following: If the 489 DNSSL domain name already exists in the DNS Search List and the 490 DNSSL option's Lifetime field is set to zero, delete the 491 corresponding DNSSL entry from both the DNS Search List and the 492 Resolver Repository in order to prevent the DNSSL domain name from 493 being used any more for certain reasons in network management, 494 e.g., the termination of the RDNSS or a renaming situation. The 495 processing of this DNSSL domain name is finished here. Otherwise, 496 go to Step (c). 498 Step (c): For each DNSSL domain name, if it already exists in the 499 DNS Server List, then just update the value of the Expiration-time 500 field according to the procedure specified in the second bullet of 501 Section 6.1. Otherwise, go to Step (d). 503 Step (d): For each DNSSL domain name, if it does not exist in the 504 DNS Search List, register the DNSSL domain name and lifetime with 505 the DNS Search List and then insert the DNSSL domain name in front 506 of the Resolver Repository. In the case where the data structure 507 for the DNS Search List is full of DNSSL domain name entries, 508 delete from the DNS Server List the entry with the shortest 509 expiration time (i.e., the entry that will expire first). The 510 corresponding DNSSL domain name is also deleted from the Resolver 511 Repository. In the order in the DNSSL option, position the newly 512 added DNSSL domain names in front of the Resolver Repository so 513 that the new DNSSL domain names may be preferred according to 514 their order in the DNSSL option for the DNS domain name used by 515 the DNS query. The processing of these DNSSL domain name is 516 finished here. Note that, in the case where there are several 517 routers advertising DNSSL option(s) in a subnet, the DNSSL domain 518 names that have been announced recently are preferred. 520 Step (e): Delete each expired entry from the DNS Search List, and 521 delete the DNSSL domain name corresponding to the entry from the 522 Resolver Repository. 524 7. Security Considerations 526 The security of the RA options for DNS configuration does not affect 527 ND protocol security [RFC4861]. This is because learning DNS 528 information via the RA options cannot be worse than learning bad 529 router information via the RA options. It can be claimed that the 530 vulnerability of ND is not worse and is a subset of the attacks that 531 any node attached to a LAN can do independently of ND. A malicious 532 node on a LAN can promiscuously receive packets for any router's MAC 533 address and send packets with the router's MAC address as the source 534 MAC address in the L2 header. As a result, L2 switches send packets 535 addressed to the router to the malicious node. Also, this attack can 536 send redirects that tell the hosts to send their traffic somewhere 537 else. The malicious node can send unsolicited RA or Neighbor 538 Advertisement (NA) replies, answer RS or Neighbor Solicitation (NS) 539 requests, etc. Also, an attacker could configure a host to send out 540 an RA with a fraudulent RDNSS address, which is presumably an easier 541 avenue of attack than becoming a rogue router and having to process 542 all traffic for the subnet. It is necessary to disable the RA RDNSS 543 option or DNSSL option in both routers and clients administratively 544 to avoid this problem. All of this can be done independently of 545 implementing ND. Therefore, it can be claimed that the RA options 546 for RDNSS and DNSSL has vulnerabilities similar to those existing in 547 unauthenticated DHCPv6. 549 It is common for network devices such as switches to include 550 mechanisms to block unauthorized ports from running a DHCPv6 server 551 to provide protection from rogue DHCP servers. That means that an 552 attacker on other ports cannot insert bogus DNS servers using DHCPv6. 553 The corresponding technique for network devices is recommended to 554 block rogue Router Advertisement messages including the RDNSS and 555 DNSSL options from unauthorized nodes. 557 An attacker may provide a bogus DNS Search List option in order to 558 cause the victim to send DNS queries to a specific DNS server when 559 the victim queries non-fully qualified domain names. For this 560 attack, the DNS resolver in IPv6 hosts can mitigate the vulnerability 561 with the recommendations in [RFC1535], [RFC1536], and [RFC3646]. 563 If the Secure Neighbor Discovery (SEND) protocol is used as a 564 security mechanism for ND, all the ND options including the RDNSS and 565 DNSSL options are automatically included in the signatures [RFC3971], 566 so the transport for the RA options is integrity-protected. However, 567 since any valid SEND node can still insert RDNSS and DNSSL options, 568 SEND cannot verify who is or is not authorized to send the options. 570 8. IANA Considerations 572 The RDNSS option defined in this document is using the IPv6 Neighbor 573 Discovery Option type in RFC 5006 [RFC5006] assigned by the IANA as 574 follows: 576 Option Name Type 577 RDNSS option 25 579 The IANA is requested to assign a new IPv6 Neighbor Discovery Option 580 type for the DNSSL option defined in this document: 582 Option Name Type 583 DNSSL option (TBD) 585 The IANA registry for these options is: 587 http://www.iana.org/assignments/icmpv6-parameters 589 9. Acknowledgements 591 This document has greatly benefited from inputs by Robert Hinden, 592 Pekka Savola, Iljitsch van Beijnum, Brian Haberman, Tim Chown, Erik 593 Nordmark, Dan Wing, and Jari Arkko. The authors sincerely appreciate 594 their contributions. 596 10. References 598 10.1. Normative References 600 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 601 Requirement Levels", BCP 14, RFC 2119, March 1997. 603 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 604 "Neighbor Discovery for IP Version 6 (IPv6)", RFC 4861, 605 September 2007. 607 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 608 Address Autoconfiguration", RFC 4862, September 2007. 610 10.2. Informative References 612 [RFC1034] Mockapetris, P., "Domain Names - Concepts and Facilities", 613 RFC 1034, November 1987. 615 [RFC1035] Mockapetris, P., "Domain Names - Implementation and 616 Specification", RFC 1035, November 1987. 618 [RFC3315] Droms, R., Ed., "Dynamic Host Configuration Protocol for 619 IPv6 (DHCPv6)", RFC 3315, July 2003. 621 [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol 622 (DHCP) Service for IPv6", RFC 3736, April 2004. 624 [RFC3646] Droms, R., Ed., "DNS Configuration options for Dynamic 625 Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, 626 December 2003. 628 [RFC5006] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, 629 "IPv6 Router Advertisement Option for DNS Configuration", 630 RFC 5006, September 2007. 632 [RFC4339] Jeong, J., Ed., "IPv6 Host Configuration of DNS Server 633 Information Approaches", RFC 4339, February 2006. 635 [RFC3971] Arkko, J., Ed., "SEcure Neighbor Discovery (SEND)", 636 RFC 3971, March 2005. 638 [RFC5358] Damas, J. and F. Neves, "Preventing Use of Recursive 639 Nameservers in Reflector Attacks", BCP 140, RFC 5358, 640 October 2008. 642 [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: 643 Defeating Denial of Service Attacks which employ IP Source 644 Address Spoofing", BCP 38, RFC 2827, May 2000. 646 [RFC1535] Gavron, E., "A Security Problem and Proposed Correction 647 With Widely Deployed DNS Software", RFC 1535, 648 October 1993. 650 [RFC1536] Kumar, A., Postel, J., Neuman, C., Danzig, P., and S. 651 Miller, "Common DNS Implementation Errors and Suggested 652 Fixes", RFC 1536, October 1993. 654 Authors' Addresses 656 Jaehoon Paul Jeong (editor) 657 Brocade Communications Systems/ETRI 658 6000 Nathan Ln N 659 Plymouth, MN 55442 660 USA 662 Phone: +1 763 268 7173 +1 763 268 7173 663 Fax: +1 763 268 6800 664 EMail: pjeong@brocade.com 665 URI: http://www.cs.umn.edu/~jjeong/ 667 Soohong Daniel Park 668 Mobile Platform Laboratory 669 SAMSUNG Electronics 670 416 Maetan-3dong, Yeongtong-Gu 671 Suwon, Gyeonggi-Do 443-742 672 Korea 674 Phone: +82 31 200 4508 +82 31 200 4508 675 EMail: soohong.park@samsung.com 677 Luc Beloeil 678 France Telecom R&D 679 42, rue des coutures 680 BP 6243 681 14066 CAEN Cedex 4 682 France 684 Phone: +33 02 3175 9391 +33 02 3175 9391 685 EMail: luc.beloeil@orange-ftgroup.com 687 Syam Madanapalli 688 Ordyn Technologies 689 1st Floor, Creator Building, ITPL 690 Bangalore - 560066 691 India 693 Phone: +91-80-40383000 +91-80-40383000 694 EMail: smadanapalli@gmail.com