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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Homenet D. Migault 3 Internet-Draft Ericsson 4 Intended status: Informational R. Weber 5 Expires: May 20, 2020 Nominum 6 M. Richardson 7 Sandelman Software Works 8 R. Hunter 9 Globis Consulting BV 10 C. Griffiths 12 W. Cloetens 13 SoftAtHome 14 November 17, 2019 16 Outsourcing Home Network Authoritative Naming Service 17 draft-ietf-homenet-front-end-naming-delegation-09 19 Abstract 21 The Homenet Naming authority is responsible for making devices within 22 the home network accessible by name within the home network as well 23 as from outside the home network (e.g. the Internet). The names of 24 the devices accessible from the Internet are stored in the Public 25 Homenet Zone, served by a DNS authoritative server. It is unlikely 26 that home networks will contain sufficiently robust platforms 27 designed to host a service such as the DNS on the Internet and as 28 such would expose the home network to DDoS attacks. 30 This document describes a mechanism that enables the Home Network 31 Authority (HNA) to outsource the naming service to the Outsourcing 32 Infrastructure via a Distribution Master (DM). 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at https://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on May 20, 2020. 50 Copyright Notice 52 Copyright (c) 2019 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (https://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 68 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 69 2.1. Alternative solutions . . . . . . . . . . . . . . . . . . 5 70 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 71 4. Architecture Description . . . . . . . . . . . . . . . . . . 7 72 4.1. Architecture Overview . . . . . . . . . . . . . . . . . . 7 73 4.2. Distribution Master Communication Channels . . . . . . . 10 74 5. Control Channel between HNA and DM . . . . . . . . . . . . . 11 75 5.1. Information to build the Public Homenet Zone. . . . . . . 11 76 5.2. Information to build the DNSSEC chain of trust. . . . . . 12 77 5.3. Information to set the Synchronization Channel, . . . . . 12 78 5.4. Deleting the delegation . . . . . . . . . . . . . . . . . 13 79 5.5. Messages Exchange Description . . . . . . . . . . . . . . 13 80 5.5.1. Retrieving information for the Public Homenet Zone. . 13 81 5.5.2. Providing information for the DNSSEC chain of trust . 14 82 5.5.3. Providing information for the Synchronization Channel 14 83 5.5.4. HNA instructing deleting the delegation . . . . . . . 15 84 5.6. Securing the Control Channel between HNA and DM . . . . . 15 85 5.7. Implementation Tips . . . . . . . . . . . . . . . . . . . 16 86 6. DM Synchronization Channel between HNA and DM . . . . . . . . 17 87 6.1. Securing the Synchronization Channel between HNA and DM . 18 88 7. DM Distribution Channel . . . . . . . . . . . . . . . . . . . 18 89 8. HNA Security Policies . . . . . . . . . . . . . . . . . . . . 18 90 9. DNSSEC compliant Homenet Architecture . . . . . . . . . . . . 19 91 10. Homenet Reverse Zone . . . . . . . . . . . . . . . . . . . . 19 92 11. Renumbering . . . . . . . . . . . . . . . . . . . . . . . . . 20 93 11.1. Hidden Primary . . . . . . . . . . . . . . . . . . . . . 20 94 11.2. Distribution Master . . . . . . . . . . . . . . . . . . 21 95 12. Operational considerations for Offline/Disconnected 96 resolution . . . . . . . . . . . . . . . . . . . . . . . . . 22 97 13. Privacy Considerations . . . . . . . . . . . . . . . . . . . 22 98 14. Security Considerations . . . . . . . . . . . . . . . . . . . 23 99 14.1. HNA DM channels . . . . . . . . . . . . . . . . . . . . 23 100 14.2. Names are less secure than IP addresses . . . . . . . . 23 101 14.3. Names are less volatile than IP addresses . . . . . . . 23 102 14.4. DNS Reflection Attacks . . . . . . . . . . . . . . . . . 23 103 14.5. Reflection Attack involving the Hidden Primary . . . . . 24 104 14.6. Reflection Attacks involving the DM . . . . . . . . . . 25 105 14.7. Reflection Attacks involving the Public Authoritative 106 Servers . . . . . . . . . . . . . . . . . . . . . . . . 26 107 14.8. Flooding Attack . . . . . . . . . . . . . . . . . . . . 26 108 14.9. Replay Attack . . . . . . . . . . . . . . . . . . . . . 27 109 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 110 16. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 28 111 17. Annex . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 112 17.1. Envisioned deployment scenarios . . . . . . . . . . . . 28 113 17.1.1. CPE Vendor . . . . . . . . . . . . . . . . . . . . . 28 114 17.1.2. Agnostic CPE . . . . . . . . . . . . . . . . . . . . 29 115 17.2. Example: Homenet Zone . . . . . . . . . . . . . . . . . 29 116 17.3. Example: HNA necessary parameters for outsourcing . . . 31 117 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 118 18.1. Normative References . . . . . . . . . . . . . . . . . . 33 119 18.2. Informative References . . . . . . . . . . . . . . . . . 36 120 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36 122 1. Requirements notation 124 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 125 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 126 document are to be interpreted as described in [RFC2119]. 128 2. Introduction 130 IPv6 provides global end to end IP connectivity. End users prefer to 131 use names instead of long and complex IPv6 addresses when accessing 132 services hosted in the home network. 134 [RFC7368] recommends that home networks be resilient to connectivity 135 disruption from the ISP. The public names should be resolvable 136 within the home network and on the Internet, even when there are 137 disruptions. This could be achieved by a device inside the home 138 network that builds, publishes, and manages a Public Homenet Zone, 139 thus providing bindings between public names, IP addresses, and other 140 RR types. 142 The management of the names can be a role that the Customer Premises 143 Equipment (CPE) does. Other devices in the home network could 144 fulfill this role e.g. a NAS server, but for simplicity, this 145 document assumes the function is located on one of the CPE devices. 147 A home network may have multiple CPEs. Since management of the 148 Public Homenet Zone involves DNS specific mechanisms that cannot be 149 distributed over multiple servers (primary server), when multiple 150 nodes can potentially manage the Public Homenet Zone, a single node 151 needs to be selected per outsourced zone. This selected node is 152 designated as providing the Homenet Naming Authority (HNA) function. 154 The process by which a single HNA is selected per zone is not in 155 scope for this document. 157 CPEs, which may host the HNA function, as well as home network 158 devices, are usually low powered devices not designed for terminating 159 heavy traffic. As a result, hosting an authoritative DNS service 160 visible to the Internet may expose the home network to resource 161 exhaustion and other attacks. Additionally, the names could become 162 unavailable during disruptions of the upstream Internet connectivity. 164 In order to avoid resource exhaustion and other attacks, this 165 document describes an architecture that outsources the authoritative 166 naming service of the home network. More specifically, the HNA 167 builds the Public Homenet Zone and outsources it to an Outsourcing 168 Infrastructure via a Distribution Master (DM). The Outsourcing 169 Infrastructure is in charge of publishing the corresponding Public 170 Homenet Zone on the Internet. The transfer of DNS zone information 171 is achieved using standard DNS mechanisms involving primary and 172 secondary DNS servers, with the HNA hosted primary being a stealth 173 primary, and the Distribution Master a secondary. 175 Section 4.1 provides an architecture description that describes the 176 relation between the HNA and the Outsourcing Architecture. In order 177 to keep the Public Homenet Zone up-to-date Section 6 describes how 178 the HNA and the Outsourcing Infrastructure synchronizes the Pubic 179 Homenet Zone. 181 The proposed architecture is explicitly designed to enable fully 182 functional DNSSEC, and the Public Homenet Zone is expected to be 183 signed with a secure delegation. DNSSEC key management and zone 184 signing is handled by the HNA. 186 Section 10 discusses management of one or more reverse zones. 187 Section 11 discusses how renumbering should be handled. Finally, 188 Section 13 and Section 14 respectively discuss privacy and security 189 considerations when outsourcing the Public Homenet Zone. 191 The Public Homenet Zone is expected to contain public information 192 only in a single universal view. This document does not define how 193 the information required to construct this view is derived. 195 It is also not in the scope of this document to define names for 196 exclusive use within the boundaries of the local home network. 197 Instead, local scope information is expected to be provided to the 198 home network using local scope naming services. mDNS [RFC6762] DNS-SD 199 [RFC6763] are two examples of these services. Currently mDNS is 200 limited to a single link network. However, future protocols and 201 architectures [I-D.ietf-homenet-simple-naming] are expected to 202 leverage this constraint as pointed out in [RFC7558]. 204 2.1. Alternative solutions 206 An alternative existing solution in IPv4 is to have a single zone, 207 where a host uses a RESTful HTTP service to register a single name 208 into a common public zone. This is often called "Dynamic DNS", and 209 there are a number of commercial providers, including Dyn, Gandi etc. 210 These solutions were typically used by a host behind the CPE to make 211 it's CPE IPv4 address visible, usually in order to enable incoming 212 connections. 214 For a small number (one to three) of hosts, use of such a system 215 provides an alternative to the architecture described in this 216 document. 218 The alternative does suffer from some severe limitations: 220 o the CPE/HNA router is unaware of the process, and cannot respond 221 to queries for these names when there are disruptions in 222 connectivity. This makes the home user or application dependent 223 on having to resolve different names in the event of outages or 224 disruptions. 226 o the CPE/HNA router cannot control the process. Any host can do 227 this regardless of whether or not the home network administrator 228 wants the name published or not. There is therefore no possible 229 audit trail. 231 o the credentials for the dynamic DNS server need to be securely 232 transferred to all hosts that wish to use it. This is not a 233 problem for a technical user to do with one or two hosts, but it 234 does not scale to multiple hosts and becomes a problem for non- 235 technical users. 237 o "all the good names are taken" - current services put everyone's 238 names into some small set of zones, and there are often conflicts. 240 Distinguishing similar names by delegation of zones was among the 241 primary design goals of the DNS system. 243 o The RESTful services do not always support all RR types. The 244 homenet user is dependent on the service provider supporting new 245 types. By providing full DNS delegation, this document enables 246 all RR types and also future extensions. 248 There is no technical reason why a RESTful cloud service could not 249 provide solutions to many of these problems, but this document 250 describes a DNS based solution. 252 3. Terminology 254 o Customer Premises Equipment: (CPE) is a router providing 255 connectivity to the home network. 257 o Homenet Zone: is the DNS zone for use within the boundaries of the 258 home network: home.arpa, see [RFC8375]). This zone is not 259 considered public and is out of scope for this document. 261 o Registered Homenet Domain: is the Domain Name associated with the 262 home network. 264 o Public Homenet Zone: contains the names in the home network that 265 are expected to be publicly resolvable on the Internet. 267 o Homenet Naming Authority: (HNA) is a function responsible for 268 managing the Public Homenet Zone. This includes populating the 269 Public Homenet Zone, signing the zone for DNSSEC, as well as 270 managing the distribution of that Homenet Zone to the Outsourcing 271 Infrastructure. 273 o Outsourcing Infrastructure: is the infrastructure responsible for 274 receiving the Public Homenet Zone and publishing it on the 275 Internet. It is mainly composed of a Distribution Master and 276 Public Authoritative Servers. 278 o Public Authoritative Servers: are the authoritative name servers 279 for the Public Homenet Zone. Name resolution requests for the 280 Homenet Domain are sent to these servers. For resiliency the 281 Public Homenet Zone SHOULD be hosted on multiple servers. 283 o Homenet Authoritative Servers: are authoritative name servers 284 within the Homenet network. 286 o Distribution Master (DM): is the (set of) server(s) to which the 287 HNA synchronizes the Public Homenet Zone, and which then 288 distributes the relevant information to the Public Authoritative 289 Servers. 291 o Homenet Reverse Zone: The reverse zone file associated with the 292 Public Homenet Zone. 294 o Reverse Public Authoritative Servers: equivalent to Public 295 Authoritative Servers specifically for reverse resolution. 297 o Reverse Distribution Master: equivalent to Distribution Master 298 specifically for reverse resolution. 300 o Homenet DNSSEC Resolver: a resolver that performs a DNSSEC 301 resolution on the home network for the Public Homenet Zone. The 302 resolution is performed requesting the Homenet Authoritative 303 Servers. 305 o DNSSEC Resolver: a resolver that performs a DNSSEC resolution on 306 the Internet for the Public Homenet Zone. The resolution is 307 performed requesting the Public Authoritative Servers. 309 4. Architecture Description 311 This section provides an overview of the architecture for outsourcing 312 the authoritative naming service from the HNA to the Outsourcing 313 Infrastructure in Section 4.1. Section Section 17.2 and Section 17.3 314 illustrates this architecture with the example of a Public Homenet 315 Zone as well as necessary parameter to configure the HNA. 317 4.1. Architecture Overview 319 Figure Figure 1 illustrates the architecture where the HNA outsources 320 the publication of the Public Homenet Zone to the Outsourcing 321 Infrastructure. 323 The Public Homenet Zone is identified by the Registered Homenet 324 Domain Name - example.com. 326 ".local" as well as ".home.arpa" are explicitly not considered as 327 Public Homenet zones. 329 The HNA SHOULD build the Public Homenet Zone in a single view 330 populated with all resource records that are expected to be published 331 on the Internet. 333 Resource records associated with services or devices that are not 334 expected to be resolvable from outside the home network, or resource 335 records bound to non-globally reachable IP addresses e.g. ULA, MUST 336 NOT be part of the Public Homenet Zone. 338 How the Public Homenet Zone is populated is out of the scope of this 339 document. The node providing the HNA function may also host or 340 interact with multiple services to determine name-to-address 341 mappings, such as a web GUI, DHCP [RFC6644] or mDNS [RFC6762]. These 342 services may coexist and may be used to populate the Public Homenet 343 Zone. 345 The HNA also signs the Public Homenet Zone. The HNA handles all 346 operations and keying material required for DNSSEC, so there is no 347 provision made in this architecture for transferring private DNSSEC 348 related keying material between the HNA and the DM. 350 Once the Public Homenet Zone has been built, the HNA outsources it to 351 the Outsourcing Infrastructure as described in Figure 1. 353 The HNA acts as a hidden primary while the DM behaves as a secondary 354 responsible to distribute the Public Homenet Zone to the multiple 355 Public Authoritative Servers that Outsourcing Infrastructure is 356 responsible for. 358 The DM has 3 communication channels: * a DM Control Channel (see 359 section Section 5) to configure the HNA and the Outsourcing 360 Infrastructure, * a DM Synchronization Channel (see section Section 6 361 to synchronize the Public Homenet Zone on the HNA and on the DM. * 362 one or more Distribution Channels (see section Section 7 that 363 distributes the Public Homenet Zone from the DM to the Public 364 Authoritative Server serving the Public Homenet Zone on the Internet. 366 There MAY be multiple DM's, and multiple servers per DM. This text 367 assumes a single DM server for simplicity, but there is no reason why 368 each channel need to be implemented on the same server, or indeed use 369 the same code base. 371 It is important to note that while the HNA is configured as an 372 authoritative server, it is not expected to answer to DNS requests 373 from the public Internet for the Public Homenet Zone. The function 374 of the HNA is limited to building the zone and synchronization with 375 the DM. 377 The addresses associated with the HNA SHOULD NOT be mentioned in the 378 NS records of the Public Homenet zone, unless additional security 379 provisions necessary to protect the HNA from external attack have 380 been taken. 382 The Outsourcing Infrastructure is also responsible for ensuring the 383 DS record has been updated in the parent zone. 385 Resolution is performed by the DNSSEC resolvers. When the resolution 386 is performed outside the home network, the DNSSEC Resolver resolves 387 the DS record on the Global DNS and the name associated to the Public 388 Homenet Zone (example.com) on the Public Authoritative Servers. 390 When the resolution is performed from within the home network, the 391 Homenet DNSSEC Resolver may proceed similarly. On the other hand, to 392 provide resilience to the Public Homenet Zone in case of disruption, 393 the Homenet DNSSEC Resolver SHOULD be able to perform the resolution 394 on the authoritative name service of the home network implemented by 395 the Homenet Authoritative Servers. These servers are not expected to 396 be mentioned in the Public Homenet Zone, nor to be accessible from 397 the Internet. As such their information as well as the corresponding 398 signed DS record MAY be provided by the HNA to the Homenet DNSSEC 399 Resolvers e.g. using HNCP. Such configuration is outside the scope 400 of this document. 402 How the Homenet Authoritative Servers are provisioned is also out of 403 scope of this specification. It could be implemented using primary 404 secondaries servers, or via rsync. In some cases, the HNA and 405 Homenet Authoritative Servers may be combined together which would 406 result in a common instantiation of an authoritative server on the 407 WAN and inner interface. Other mechanisms may also be used. 409 Home network | Internet 410 | 411 | +----------------------------+ 412 | | Outsourcing Infrastructure | 413 Control | | | 414 +-----------------------+Channel | | +-----------------------+ | 415 | HNA |<-------------->| Distribution Master | | 416 |+---------------------+| | | |+---------------------+| | 417 || Public Homenet Zone ||Synchronization || Public Homenet Zone || | 418 || (example.com) ||Channel | | || (example.com) || | 419 |+---------------------+|<-------------->|+---------------------+| | 420 +----------------------+| | | +-----------------------+ | 421 | | ^ Distribution | 422 | | | Channel | 423 +-----------------------+ | | v | 424 | Homenet Authoritative | | | +-----------------------+ | 425 | Server(s) | | | | Public Authoritative | | 426 |+---------------------+| | | | Server(s) | | 427 ||Public Homenet Zone || | | |+---------------------+| | 428 || (example.com) || | | || Public Homenet Zone || | 429 |+---------------------+| | | || (example.com) || | 430 +-----------------------+ | | |+---------------------+| | 431 ^ | | | +-----------------------+ | 432 | | | +----------^---|-------------+ 433 | | | | | 434 | | name resolution | | 435 | v | | v 436 +----------------------+ | +-----------------------+ 437 | Homenet | | | Internet | 438 | DNSSEC Resolver | | | DNSSEC Resolver | 439 +----------------------+ | +-----------------------+ 441 Figure 1: Homenet Naming Architecture Name Resolution 443 4.2. Distribution Master Communication Channels 445 This section details the interfaces and channels of the DM, that is 446 the Control Channel, the Synchronization Channel and the Distribution 447 Channel. 449 The Control Channel and the Synchronization Channel are the 450 interfaces used between the HNA and the Outsourcing Infrastructure. 451 The entity within the Outsourcing Infrastructure responsible to 452 handle these communications is the DM and communications between the 453 HNA and the DM SHOULD be protected and mutually authenticated. While 454 section Section 5.6 discusses in more depth the different security 455 protocols that could be used to secure, this specification RECOMMENDS 456 the use of TLS with mutually authentication based on certificates to 457 secure the channel between the HNA and the DM. 459 The Control Channel is used to set up the Synchronization Channel. 460 We assume that the HNA initiates the Control Channel connection with 461 the DM and as such has a prior knowledge of the DM identity (X509 462 certificate), the IP address and port to use and protocol to set 463 secure session. We also assume the DM has knowledge of the identity 464 of the HNA (X509 certificate) as well as the Registered Homenet 465 Domain. 467 The information exchanged between the HNA and the DM is using DNS 468 messages. DNS messages can be protected using various kind of 469 transport layers, among others, UDP:53/DTLS, TLS/TCP:53, HTTPS:443. 470 There was consideration to using a standard TSIG [RFC2845] or SIG(0) 471 [RFC2931] to perform a dynamic DNS update to the DM. There are a 472 number of issues with this. The main one is that the Dynamic DNS 473 update would also update the zone's NS records, while the goal is to 474 update the Distribution Master's configuration files. The visible NS 475 records SHOULD remain pointing at the cloud provider's anycast 476 addresses. Revealing the address of the HNA in the DNS is not 477 desireable. 479 This specification also assumes the same transport protocol and ports 480 used by the DM to serve the Control Channel and by the HNA to serve 481 the Synchronization Channel are the same. 483 The Distribution Channel is internal to the Outsourcing 484 Infrastructure and as such is not the primary concern of this 485 specification. 487 5. Control Channel between HNA and DM 489 The DM Control Channel is used by the HNA and the Outsourcing 490 Infrastructure to exchange information related to the configuration 491 of the delegation which includes: 493 5.1. Information to build the Public Homenet Zone. 495 More specifically, the Public Homenet Zone contains information that 496 is related to the infrastructure serving the zone. In our case, the 497 infrastructure serving the Public Homenet Zone is the Outsourcing 498 Infrastructure, so this information MUST reflect that Outsourcing 499 Infrastructure and MUST be provided to the HNA. 501 The information includes at least names and IP addresses of the 502 Public Authoritative Servers. In term of RRset information this 503 corresponds, for the Registered Homenet Domain the MNAME of the SOA, 504 the NS and associated A and AAA RRsets. Optionally the Outsourcing 505 Infrastructure MAY also provide operational parameters such as other 506 fields of SOA (SERIAL, RNAME, REFRESH, RETRY, EXPIRE and MINIMUM). 507 As the information is necessary for the HNA to proceed and the 508 information is associated to the Outsourcing Infrastructure, this 509 information exchange is mandatory. 511 5.2. Information to build the DNSSEC chain of trust. 513 The HNA SHOULD provide the hash of the KSK (DS RRset), so the that 514 Outsourcing Infrastructure provides this value to the parent zone. A 515 common deployment use case is that the Outsourcing Infrastructure is 516 the registrar of the Registered Homenet Domain, and as such, its 517 relationship with the registry of the parent zone enables it to 518 update the parent zone. When such relation exists, the HNA should be 519 able to request the Outsourcing Infrastructure to update the DS RRset 520 in the parent zone. A direct update is especially necessary to 521 initialize the chain of trust. 523 Though the HNA may also later directly update the values of the DS 524 via the Control Channel, it is RECOMMENDED to use other mechanisms 525 such as CDS and CDNSKEY [RFC7344] are used for key roll overs. 527 As some deployment may not provide an Outsourcing Infrastructure that 528 will be able to update the DS in the parent zone, this information 529 exchange is OPTIONAL. 531 By accepting the DS, the DM commits in taking care of advertising the 532 DS to the parent zone. Upon refusal, the DM MUST clearly indicate 533 the DM does not have the capacity to proceed to the update. 535 5.3. Information to set the Synchronization Channel, 537 That information sets the primary/secondary relation between the HNA 538 and the DM. The HNA works as a primary authoritative DNS server, and 539 MUST provide the corresponding IP address. 541 The specified IP address on the HNA side and the currently used IP 542 address of the DM defines the IP addresses involved in the 543 Synchronization Channel. Ports and transport protocol are the same 544 as those used by the Control Channel. By default, the same IP 545 address used by the HNA is considered by the DM. Exchange of this 546 information is OPTIONAL. 548 5.4. Deleting the delegation 550 The purpose of the previous sections were to exchange information in 551 order to set a delegation. The HNA MUST also be able to delete a 552 delegation with a specific DM. Upon an instruction of deleting the 553 delegation, the DM MUST stop serving the Public Homenet Zone. 555 5.5. Messages Exchange Description 557 There are multiple ways these information could be exchanged between 558 the HNA and the DM. This specification defines a mechanism that re- 559 use the DNS exchanges format. The intention is to reuse standard 560 libraries especially to check the format of the exchanged fields as 561 well as to minimize the additional libraries needed for the HNA. The 562 re-use of DNS exchanges achieves these goals. Note that while 563 information is provided using DNS exchanges, the exchanged 564 information is not expected to be set in any zone file, instead this 565 information is expected to be processed appropriately. 567 The Control Channel is not expected to be a long term session. After 568 a predefined timer the Control Channel is expected to be terminated. 569 The Control Channel MAY Be re-opened at any time later. 571 The provisioning process SHOULD provide a method of securing the 572 control channel, so that the content of messages can be 573 authenticated. This authentication MAY be based on certificates for 574 both the DM and each HNA. The DM may also create the initial 575 configuration for the delegation zone in the parent zone during the 576 provisioning process. 578 5.5.1. Retrieving information for the Public Homenet Zone. 580 The information provided by the DM to the HNA is retrieved by the HNA 581 with a AXFR exchange. The AXFR message enables the response to 582 contain any type of RRsets. The response might be extended in the 583 future if additional information will be needed. Alternatively, the 584 information provided by the HNA to the DM is pushed by the HNA via a 585 DNS update exchange. 587 To retrieve the necessary information to build the Public Homenet 588 Zone, the HNA MUST send an DNS request of type AXFR associated to the 589 Registered Homenet Domain. The DM MUST respond with a zone template. 590 The zone template MUST contain a RRset of type SOA, one or multiple 591 RRset of type NS and at least one RRset of type A or AAAA. The SOA 592 RR is used to indicate to the HNA the value of the MNAME of the 593 Public Homenet Zone. The NAME of the SOA RR MUST be the Registered 594 Homenet Domain. The MNAME value of the SOA RDATA is the value 595 provided by the Outsourcing Infrastructure to the HNA. Other RDATA 596 values (RNAME, REFRESH, RETRY, EXPIRE and MINIMUM) are provided by 597 the Outsourcing Infrastructure as suggestions. The NS RRsets are 598 used to carry the Public Authoritative Servers of the Outsourcing 599 Infrastructure. Their associated NAME MUST be the Registered Homenet 600 Domain. The TTL and RDATA are those expected to be published on the 601 Public Homenet Zone. The RRsets of Type A and AAAA MUST have their 602 NAME matching the NSDNAME of one of the NS RRsets. 604 Upon receiving the response, the HNA MUST validate the conditions on 605 the SOA, NS and A or AAAA RRsets. If an error occurs, the HNA MUST 606 stop proceeding and MUST report an error. Otherwise, the HNA builds 607 the Public Homenet Zone by setting the MNAME value of the SOA as 608 indicated by the SOA provided by the AXFR response. The HNA SHOULD 609 set the value of NAME, REFRESH, RETRY, EXPIRE and MINIMUM of the SOA 610 to those provided by the AXFR response. The HNA MUST insert the NS 611 and corresponding A or AAAA RRset in its Public Homenet Zone. The 612 HNA MUST ignore other RRsets. If an error message is returned by the 613 DM, the HNA MUST proceed as a regular DNS resolution. Error messages 614 SHOULD be logged for further analysis. If the resolution does not 615 succeed, the outsourcing operation is aborted and the HNA MUST close 616 the Control Channel. 618 5.5.2. Providing information for the DNSSEC chain of trust 620 To provide the DS RRset to initialize the DNSSEC chain of trust the 621 HNA MAY send a DNS UPDATE [RFC2136] message. The NAME in the SOA 622 MUST be set to the parent zone of the Registered Homenet Domain - 623 that is where the DS records should be inserted. The DS RRset MUST 624 be placed in the Update section of the UPDATE query, and the NAME 625 SHOULD be set to the Registered Homenet Domain. The rdata of the DS 626 RR SHOULD correspond to the DS record to be inserted in the parent 627 zone. 629 A NOERROR response from the MD is a commitment to update the parent 630 zone with the provided DS. An error indicates the MD will not update 631 the DS, and other method should be used by the HNA. 633 5.5.3. Providing information for the Synchronization Channel 635 To provide the IP address of the primary, the HNA MAY send a DNS 636 UPDATE message. The NAME in the SOA MUST be the parent zone of the 637 Registered Homenet Domain. The Update section MUST be a RRset of 638 Type NS. The NAME associated to the NS RRSet MUST be the Registered 639 Domain Name. The RDATA MUST be a FQDN that designates the IP 640 addresses associated to the primary. There may be multiple IP 641 addresses. These IP addresses MUST be provided in the additional 642 section. The reason to provide these IP addresses is that it is NOT 643 RECOMMENDED to publish these IP addresses. As a result, it is not 644 expected to resolve them. IP addresses are provided via RRsets of 645 type A or AAAA. The NAME associated to RRsets of type A and AAAA 646 MUST be the Registered Homenet Domain. 648 A NOERROR response indicates the DM has configured the secondary and 649 is committed to serve as a secondary. An error indicates the DM is 650 not configured as a secondary. 652 The regular DNS error message SHOULD be returned to the HNA when an 653 error occurs. In particular a FORMERR is returned when a format 654 error is found, this error includes when unexpected RRSets are added 655 or when RRsets are missing. A SERVFAIL error is returned when a 656 internal error is encountered. a NOTZONE error is returned when 657 update and Zone sections are not coherent, a NOTAUTH error is 658 returned when the DM is not authoritative for the Zone section. A 659 REFUSED error is returned when the DM refuses to proceed to the 660 configuration and the requested action. 662 5.5.4. HNA instructing deleting the delegation 664 To instruct to delete the delegation the HNA MAY send a DNS UPDATE 665 Delete message. The NAME in the SOA MUST be the parent zone of the 666 Registered Homenet Domain. The Update section MUST be a RRset of 667 Type NS. The NAME associated to the NS RRSet MUST be the Registered 668 Domain Name. As indictaed by [RFC2136] section 2.5.2 the delete 669 instruction is set by setting the TTL to 0, the CLass to ANY, the 670 RDLENGTH to 0 and the RDATA MUST be empty. 672 5.6. Securing the Control Channel between HNA and DM 674 The control channel between the HNA and the DM MUST be secured at 675 both the HNA and the DM. 677 Secure protocols (like TLS [RFC5246] / DTLS [RFC6347]) SHOULD be used 678 to secure the transactions between the DM and the HNA. 680 The advantage of TLS/DTLS is that this technology is widely deployed, 681 and most of the devices already embed TLS/DTLS libraries, possibly 682 also taking advantage of hardware acceleration. Further, TLS/DTLS 683 provides authentication facilities and can use certificates to 684 authenticate the DM and the HNA. On the other hand, using TLS/DTLS 685 requires implementing DNS exchanges over TLS/DTLS, as well as a new 686 service port. This document RECOMMENDS this option. 688 The HNA SHOULD authenticate inbound connections from the DM using 689 standard mechanisms, such as a public certificate with baked-in root 690 certificates on the HNA, or via DANE {!RFC6698}}. 692 The DM SHOULD authenticate the HNA and check that inbound messages 693 are from the appropriate client. The DM MAY use a self-signed CA 694 certificate mechanism per HNA, or public certificates for this 695 purpose. 697 IPsec [RFC4301] IKEv2 [RFC7296] MAY also be used to secure 698 transactions between the HNA and the DM. Similarly to TLS/DTLS, most 699 HNAs already embed an IPsec stack, and IKEv2 supports multiple 700 authentication mechanisms via the EAP framework. In addition, IPsec 701 can be used to protect DNS exchanges between the HNA and the DM 702 without any modifications of the DNS server or client. DNS 703 integration over IPsec only requires an additional security policy in 704 the Security Policy Database (SPD). One disadvantage of IPsec is 705 that NATs and firewall traversal may be problematic. However, in our 706 case, the HNA is connected to the Internet, and IPsec communication 707 between the HNA and the DM should not be impacted by middle boxes. 709 How the PSK can be used by any of the TSIG, TLS/DTLS or IPsec 710 protocols: Authentication based on certificates implies a mutual 711 authentication and thus requires the HNA to manage a private key, a 712 public key, or certificates, as well as Certificate Authorities. 713 This adds complexity to the configuration especially on the HNA side. 714 For this reason, we RECOMMEND that the HNA MAY use PSK or certificate 715 based authentication, and that the DM MUST support PSK and 716 certificate based authentication. 718 Note also that authentication of message exchanges between the HNA 719 and the DM SHOULD NOT use the external IP address of the HNA to index 720 the appropriate keys. As detailed in Section 11, the IP addresses of 721 the DM and the Hidden Primary are subject to change, for example 722 while the network is being renumbered. This means that the necessary 723 keys to authenticate transaction SHOULD NOT be indexed using the IP 724 address, and SHOULD be resilient to IP address changes. 726 5.7. Implementation Tips 728 The Hidden Primary Server on the HNA differs from a regular 729 authoritative server for the home network due to: 731 o Interface Binding: the Hidden Primary Server will almost certainly 732 listen on the WAN Interface, whereas a regular authoritative 733 server for the home network would listen on the internal home 734 network interface. 736 o Limited exchanges: the purpose of the Hidden Primary Server is to 737 synchronize with the DM, not to serve any zones to end users, or 738 the public Internet. 740 As a result, exchanges are performed with specific nodes (the DM). 741 Further, exchange types are limited. The only legitimate exchanges 742 are: NOTIFY initiated by the Hidden Primary and IXFR or AXFR 743 exchanges initiated by the DM. On the other hand, regular 744 authoritative servers would respond to any hosts, and any DNS query 745 would be processed. The HNA SHOULD filter IXFR/AXFR traffic and drop 746 traffic not initiated by the DM. The HNA MUST listen for DNS on TCP 747 and UDP and MUST at least allow SOA lookups of the Homenet Zone. 749 6. DM Synchronization Channel between HNA and DM 751 The DM Synchronization Channel is used for communication between the 752 HNA and the DM for synchronizing the Public Homenet Zone. Note that 753 the Control Channel and the Synchronization Channel are by 754 construction different channels even though there they MAY use the 755 same IP addresses. In fact the Control Channel is set between the 756 HNA working as a client using port YYYY (a high range port) toward a 757 service provided by the MD at port XX (well known port). On the 758 other hand, the Synchronization Channel is set between the MD working 759 as a client using port ZZZZ ( a high range port) toward a service a 760 service provided by the HNA at port XX. As a result, even though the 761 same couple of IP addresses may be involved the Control Channel and 762 the Synchronization Channel are always disc tint channels. 764 Uploading and dynamically updating the zone file on the DM can be 765 seen as zone provisioning between the HNA (Hidden Primary) and the DM 766 (Secondary Server). This can be handled via AXFR + DNS UPDATE. 768 This document RECOMMENDS use of a primary / secondary mechanism 769 instead of the use of DNS UPDATE. The primary / secondary mechanism 770 is RECOMMENDED as it scales better and avoids DoS attacks. Note that 771 even when UPDATE messages are used, these messages are using a 772 distinct channel as those used to set the configuration. 774 Note that there is no standard way to distribute a DNS primary 775 between multiple devices. As a result, if multiple devices are 776 candidate for hosting the Hidden Primary, some specific mechanisms 777 should be designed so the home network only selects a single HNA for 778 the Hidden Primary. Selection mechanisms based on HNCP [RFC7788] are 779 good candidates. 781 The HNA acts as a Hidden Primary Server, which is a regular 782 authoritative DNS Server listening on the WAN interface. 784 The DM is configured as a secondary for the Homenet Domain Name. 785 This secondary configuration has been previously agreed between the 786 end user and the provider of the Outsourcing Infrastructure as part 787 of either the provisioning or due to receipt of UPDATE messages on 788 the DM Control Channel. 790 The Homenet Reverse Zone MAY also be updated either with DNS UPDATE 791 [RFC2136] or using a primary / secondary synchronization. 793 6.1. Securing the Synchronization Channel between HNA and DM 795 The Synchronization Channel used standard DNS request. 797 First the primary notifies the secondary that the zone must be 798 updated and eaves the secondary to proceed with the update when 799 possible/ convenient. 801 Then, a NOTIFY message is sent by the primary, which is a small 802 packet that is less likely to load the secondary. 804 Finally, the AXFR [RFC1034] or IXFR [RFC1995] query performed by the 805 secondary is a small packet sent over TCP (section 4.2 [RFC5936]), 806 which mitigates reflection attacks using a forged NOTIFY. 808 The AXFR request from the DM to the HNA SHOULD be secured. DNS over 809 TLS [RFC7858] is RECOMMENDED. 811 When using TLS, the HNA MAY authenticate inbound connections from the 812 DM using standard mechanisms, such as a public certificate with 813 baked-in root certificates on the HNA, or via DANE {!RFC6698}} 815 The HNA MAY apply a simple IP filter on inbound AXFR requests to 816 ensure they only arrive from the DM Synchronization Channel. In this 817 case, the HNA SHOULD regularly check (via DNS resolution) that the 818 address of the DM in the filter is still valid. 820 7. DM Distribution Channel 822 The DM Distribution Channel is used for communication between the DM 823 and the Public Authoritative Servers. The architecture and 824 communication used for the DM Distribution Channels is outside the 825 scope of this document, and there are many existing solutions 826 available e.g. rsynch, DNS AXFR, REST, DB copy. 828 8. HNA Security Policies 830 This section details security policies related to the Hidden Primary 831 / Secondary synchronization. 833 The Hidden Primary, as described in this document SHOULD drop any 834 queries from the home network. This could be implemented via port 835 binding and/or firewall rules. The precise mechanism deployed is out 836 of scope of this document. The Hidden Primary SHOULD drop any DNS 837 queries arriving on the WAN interface that are not issued from the 838 DM. The Hidden Primary SHOULD drop any outgoing packets other than 839 DNS NOTIFY query, SOA response, IXFR response or AXFR responses. The 840 Hidden Primary SHOULD drop any incoming packets other than DNS NOTIFY 841 response, SOA query, IXFR query or AXFR query. The Hidden Primary 842 SHOULD drop any non protected IXFR or AXFR exchange,depending on how 843 the synchronization is secured. 845 9. DNSSEC compliant Homenet Architecture 847 [RFC7368] in Section 3.7.3 recommends DNSSEC to be deployed on both 848 the authoritative server and the resolver. The resolver side is out 849 of scope of this document, and only the authoritative part of the 850 server is considered. 852 This document assumes the HNA signs the Public Homenet Zone. 854 Secure delegation is achieved only if the DS RRset is properly set in 855 the parent zone. Secure delegation is performed by the HNA or the 856 Outsourcing Infrastructures. 858 The DS RRset can be updated manually with nsupdate for example. This 859 requires the HNA or the Outsourcing Infrastructure to be 860 authenticated by the DNS server hosting the parent of the Public 861 Homenet Zone. Such a trust channel between the HNA and the parent 862 DNS server may be hard to maintain with HNAs, and thus may be easier 863 to establish with the Outsourcing Infrastructure. In fact, the 864 Public Authoritative Server(s) may use Automating DNSSEC Delegation 865 Trust Maintenance [RFC7344]. 867 10. Homenet Reverse Zone 869 This section is focused on the Homenet Reverse Zone. 871 Firstly, all considerations for the Public Homenet Zone apply to the 872 Homenet Reverse Zone. The main difference between the Homenet 873 Reverse Zone and the Homenet Zone is that the parent zone of the 874 Homenet Reverse Zone is most likely managed by the ISP. As the ISP 875 also provides the IP prefix to the HNA, it may be able to 876 authenticate the HNA using mechanisms outside the scope of this 877 document e.g. the physical attachment point to the ISP network. If 878 the Reverse DM is managed by the ISP, credentials to authenticate the 879 HNA for the zone synchronization may be set automatically and 880 transparently to the end user. 881 [I-D.ietf-homenet-naming-architecture-dhc-options] describes how 882 automatic configuration may be performed. 884 With IPv6, the domain space for IP addresses is so large that reverse 885 zone may be confronted with scalability issues. How the reverse zone 886 is generated is out of scope of this document. 887 [I-D.howard-dnsop-ip6rdns] provides guidance on how to address 888 scalability issues. 890 11. Renumbering 892 This section details how renumbering is handled by the Hidden Primary 893 server or the DM. Both types of renumbering are discussed i.e. 894 "make-before-break" and "break-before-make". 896 In the make-before-break renumbering scenario, the new prefix is 897 advertised, the network is configured to prepare the transition to 898 the new prefix. During a period of time, the two prefixes old and 899 new coexist, before the old prefix is completely removed. In the 900 break-before-make renumbering scenario, the new prefix is advertised 901 making the old prefix obsolete. 903 Renumbering has been extensively described in [RFC4192] and analyzed 904 in [RFC7010] and the reader is expected to be familiar with them 905 before reading this section. 907 11.1. Hidden Primary 909 In a renumbering scenario, the Hidden Primary is informed it is being 910 renumbered. In most cases, this occurs because the whole home 911 network is being renumbered. As a result, the Public Homenet Zone 912 will also be updated. Although the new and old IP addresses may be 913 stored in the Public Homenet Zone, we recommend that only the newly 914 reachable IP addresses be published. 916 To avoid reachability disruption, IP connectivity information 917 provided by the DNS SHOULD be coherent with the IP plane. In our 918 case, this means the old IP address SHOULD NOT be provided via the 919 DNS when it is not reachable anymore. Let for example TTL be the TTL 920 associated with a RRset of the Public Homenet Zone, it may be cached 921 for TTL seconds. Let T_NEW be the time the new IP address replaces 922 the old IP address in the Homenet Zone, and T_OLD_UNREACHABLE the 923 time the old IP is not reachable anymore. 925 In the case of the make-before-break, seamless reachability is 926 provided as long as T_OLD_UNREACHABLE - T_NEW > 2 * TTL. If this is 927 not satisfied, then devices associated with the old IP address in the 928 home network may become unreachable for 2 * TTL - (T_OLD_UNREACHABLE 929 - T_NEW). In the case of a break-before-make, T_OLD_UNREACHABLE = 930 T_NEW, and the device may become unreachable up to 2 * TTL. 932 Once the Public Homenet Zone file has been updated on the Hidden 933 Primary, the Hidden Primary needs to inform the Outsourcing 934 Infrastructure that the Public Homenet Zone has been updated and that 935 the IP address to use to retrieve the updated zone has also been 936 updated. Both notifications are performed using regular DNS 937 exchanges. Mechanisms to update an IP address provided by lower 938 layers with protocols like SCTP [RFC4960], MOBIKE [RFC4555] are not 939 considered in this document. 941 The Hidden Primary SHOULD inform the DM that the Public Homenet Zone 942 has been updated by sending a NOTIFY payload with the new IP address. 943 In addition, this NOTIFY payload SHOULD be authenticated using SIG(0) 944 or TSIG. When the DM receives the NOTIFY payload, it MUST 945 authenticate it. Note that the cryptographic key used for the 946 authentication SHOULD be indexed by the Registered Homenet Domain 947 contained in the NOTIFY payload as well as the RRSIG. In other 948 words, the IP address SHOULD NOT be used as an index. If 949 authentication succeeds, the DM MUST also notice the IP address has 950 been modified and perform a reachability check before updating its 951 primary configuration. The routability check MAY performed by 952 sending a SOA request to the Hidden Primary using the source IP 953 address of the NOTIFY. This exchange is also secured, and if an 954 authenticated response is received from the Hidden Primary with the 955 new IP address, the DM SHOULD update its configuration file and 956 retrieve the Public Homenet Zone using an AXFR or a IXFR exchange. 958 Note that the primary reason for providing the IP address is that the 959 Hidden Primary is not publicly announced in the DNS. If the Hidden 960 Primary were publicly announced in the DNS, then the IP address 961 update could have been performed using the DNS as described in 962 Section 11.2. 964 11.2. Distribution Master 966 Renumbering of the Distribution Master results in it changing its IP 967 address. As the DM is a secondary, the destination of DNS NOTIFY 968 payloads MUST be changed, and any configuration/firewalling that 969 restricts DNS AXFR/IXFR operations MUST be updated. 971 If the DM is configured in the Hidden Primary configuration file 972 using a FQDN, then the update of the IP address is performed by DNS. 973 More specifically, before sending the NOTIFY, the Hidden Primary 974 performs a DNS resolution to retrieve the IP address of the 975 secondary. 977 As described in Section 11.1, the DM DNS information SHOULD be 978 coherent with the IP plane. The TTL of the Distribution Master name 979 SHOULD be adjusted appropriately prior to changing the IP address. 981 Some DNS infrastructure uses the IP address to designate the 982 secondary, in which case, other mechanisms must be found. The reason 983 for using IP addresses instead of names is generally to reach an 984 internal interface that is not designated by a FQDN, and to avoid 985 potential bootstrap problems. Such scenarios are considered as out 986 of scope in the case of home networks. 988 12. Operational considerations for Offline/Disconnected resolution 990 This section is non-normative. It provides suggestions on 991 operational consideration. TBD. 993 13. Privacy Considerations 995 Outsourcing the DNS Authoritative service from the HNA to a third 996 party raises a few privacy related concerns. 998 The Public Homenet Zone contains a full description of the services 999 hosted in the network. These services may not be expected to be 1000 publicly shared although their names remain accessible through the 1001 Internet. Even though DNS makes information public, the DNS does not 1002 expect to make the complete list of services public. In fact, making 1003 information public still requires the key (or FQDN) of each service 1004 to be known by the resolver in order to retrieve information about 1005 the services. More specifically, making mywebsite.example.com public 1006 in the DNS, is not sufficient to make resolvers aware of the 1007 existence web site. However, an attacker may walk the reverse DNS 1008 zone, or use other reconnaissance techniques to learn this 1009 information as described in [RFC7707]. 1011 In order to prevent the complete Public Homenet Zone being published 1012 on the Internet, AXFR queries SHOULD be blocked on the Public 1013 Authoritative Server(s). Similarly, to avoid zone-walking NSEC3 1014 [RFC5155] SHOULD be preferred over NSEC [RFC4034]. When the Public 1015 Homenet Zone is outsourced, the end user should be aware that it 1016 provides a complete description of the services available on the home 1017 network. More specifically, names usually provides a clear 1018 indication of the service and possibly even the device type, and as 1019 the Public Homenet Zone contains the IP addresses associated with the 1020 service, they also limit the scope of the scan space. 1022 In addition to the Public Homenet Zone, the third party can also 1023 monitor the traffic associated with the Public Homenet Zone. This 1024 traffic may provide an indication of the services an end user 1025 accesses, plus how and when they use these services. Although, 1026 caching may obfuscate this information inside the home network, it is 1027 likely that outside your home network this information will not be 1028 cached. 1030 14. Security Considerations 1032 The Homenet Naming Architecture described in this document solves 1033 exposing the HNA's DNS service as a DoS attack vector. 1035 14.1. HNA DM channels 1037 The HNA DM channels are specified to include their own security 1038 mechanisms that are designed to provide the minimum attacke surface, 1039 and to authenticate transactions where necessary. 1041 14.2. Names are less secure than IP addresses 1043 This document describes how an end user can make their services and 1044 devices from his home network reachable on the Internet by using 1045 names rather than IP addresses. This exposes the home network to 1046 attackers, since names are expected to include less entropy than IP 1047 addresses. In fact, with IP addresses, the Interface Identifier is 1048 64 bits long leading to up to 2^64 possibilities for a given 1049 subnetwork. This is not to mention that the subnet prefix is also of 1050 64 bits long, thus providing up to 2^64 possibilities. On the other 1051 hand, names used either for the home network domain or for the 1052 devices present less entropy (livebox, router, printer, nicolas, 1053 jennifer, ...) and thus potentially exposes the devices to dictionary 1054 attacks. 1056 14.3. Names are less volatile than IP addresses 1058 IP addresses may be used to locate a device, a host or a service. 1059 However, home networks are not expected to be assigned a time 1060 invariant prefix by ISPs. As a result, observing IP addresses only 1061 provides some ephemeral information about who is accessing the 1062 service. On the other hand, names are not expected to be as volatile 1063 as IP addresses. As a result, logging names over time may be more 1064 valuable than logging IP addresses, especially to profile an end 1065 user's characteristics. 1067 PTR provides a way to bind an IP address to a name. In that sense, 1068 responding to PTR DNS queries may affect the end user's privacy. For 1069 that reason end users may choose not to respond to PTR DNS queries 1070 and MAY instead return a NXDOMAIN response. 1072 14.4. DNS Reflection Attacks 1074 An attacker performs a reflection attack when it sends traffic to one 1075 or more intermediary nodes (reflectors), that in turn send back 1076 response traffic to the victim. Motivations for using an 1077 intermediary node might be anonymity of the attacker, as well as 1078 amplification of the traffic. Typically, when the intermediary node 1079 is a DNSSEC server, the attacker sends a DNSSEC query and the victim 1080 is likely to receive a DNSSEC response. This section analyzes how 1081 the different components may be involved as a reflector in a 1082 reflection attack. Section 14.5 considers the Hidden Primary, 1083 Section 14.6 the Synchronization Server, and Section 14.7 the Public 1084 Authoritative Server(s). 1086 14.5. Reflection Attack involving the Hidden Primary 1088 With the specified architecture, the Hidden Primary is only expected 1089 to receive DNS queries of type SOA, AXFR or IXFR. This section 1090 analyzes how these DNS queries may be used by an attacker to perform 1091 a reflection attack. 1093 DNS queries of type AXFR and IXFR use TCP and as such are less 1094 subject to reflection attacks. This makes SOA queries the only 1095 remaining practical vector of attacks for reflection attacks, based 1096 on UDP. 1098 SOA queries are not associated with a large amplification factor 1099 compared to queries of type "ANY" or to query of non existing FQDNs. 1100 This reduces the probability a DNS query of type SOA will be involved 1101 in a DDoS attack. 1103 SOA queries are expected to follow a very specific pattern, which 1104 makes rate limiting techniques an efficient way to limit such 1105 attacks, and associated impact on the naming service of the home 1106 network. 1108 Motivations for such a flood might be a reflection attack, but could 1109 also be a resource exhaustion attack performed against the Hidden 1110 Primary. The Hidden Primary only expects to exchange traffic with 1111 the DM, that is its associated secondary. Even though secondary 1112 servers may be renumbered as mentioned in Section 11, the Hidden 1113 Primary is likely to perform a DNSSEC resolution and find out the 1114 associated secondary's IP addresses in use. As a result, the Hidden 1115 Primary is likely to limit the origin of its incoming traffic based 1116 on the origin IP address. 1118 With filtering rules based on IP address, SOA flooding attacks are 1119 limited to forged packets with the IP address of the secondary 1120 server. In other words, the only victims are the Hidden Primary 1121 itself or the secondary. There is a need for the Hidden Primary to 1122 limit that flood to limit the impact of the reflection attack on the 1123 secondary, and to limit the resource needed to carry on the traffic 1124 by the HNA hosting the Hidden Primary. On the other hand, mitigation 1125 should be performed appropriately, so as to limit the impact on the 1126 legitimate SOA sent by the secondary. 1128 The main reason for the DM sending a SOA query is to update the SOA 1129 RRset after the TTL expires, to check the serial number upon the 1130 receipt of a NOTIFY query from the Hidden Primary, or to re-send the 1131 SOA request when the response has not been received. When a flood of 1132 SOA queries is received by the Hidden Primary, the Hidden Primary may 1133 assume it is involved in an attack. 1135 There are few legitimate time slots when the secondary is expected to 1136 send a SOA query. Suppose T_NOTIFY is the time a NOTIFY is sent by 1137 the Hidden Primary, T_SOA the last time the SOA has been queried, TTL 1138 the TTL associated to the SOA, and T_REFRESH the refresh time defined 1139 in the SOA RRset. The specific time SOA queries are expected can be 1140 for example T_NOTIFY, T_SOA + 2/3 TTL, T_SOA + TTL, T_SOA + 1141 T_REFRESH., and. Outside a few minutes following these specific time 1142 slots, the probability that the HNA discards a legitimate SOA query 1143 is very low. Within these time slots, the probability the secondary 1144 may have its legitimate query rejected is higher. If a legitimate 1145 SOA is discarded, the secondary will re-send SOA query every "retry 1146 time" second until "expire time" seconds occurs, where "retry time" 1147 and "expire time" have been defined in the SOA. 1149 As a result, it is RECOMMENDED to set rate limiting policies to 1150 protect HNA resources. If a flood lasts more than the expired time 1151 defined by the SOA, it is RECOMMENDED to re-initiate a 1152 synchronization between the Hidden Primary and the secondaries. 1154 14.6. Reflection Attacks involving the DM 1156 The DM acts as a secondary coupled with the Hidden Primary. The 1157 secondary expects to receive NOTIFY query, SOA responses, AXFR and 1158 IXFR responses from the Hidden Primary. 1160 Sending a NOTIFY query to the secondary generates a NOTIFY response 1161 as well as initiating an SOA query exchange from the secondary to the 1162 Hidden Primary. As mentioned in [RFC1996], this is a known "benign 1163 denial of service attack". As a result, the DM SHOULD enforce rate 1164 limiting on sending SOA queries and NOTIFY responses to the Hidden 1165 Primary. Most likely, when the secondary is flooded with valid and 1166 signed NOTIFY queries, it is under a replay attack which is discussed 1167 in Section 14.9. The key thing here is that the secondary is likely 1168 to be designed to be able to process much more traffic than the 1169 Hidden Primary hosted on a HNA. 1171 This paragraph details how the secondary may limit the NOTIFY 1172 queries. Because the Hidden Primary may be renumbered, the secondary 1173 SHOULD NOT perform permanent IP filtering based on IP addresses. In 1174 addition, a given secondary may be shared among multiple Hidden 1175 Primaries which make filtering rules based on IP harder to set. The 1176 time at which a NOTIFY is sent by the Hidden Primary is not 1177 predictable. However, a flood of NOTIFY messages may be easily 1178 detected, as a NOTIFY originated from a given Homenet Zone is 1179 expected to have a very limited number of unique source IP addresses, 1180 even when renumbering is occurring. As a result, the secondary, MAY 1181 rate limit incoming NOTIFY queries. 1183 On the Hidden Primary side, it is recommended that the Hidden Primary 1184 sends a NOTIFY as long as the zone has not been updated by the 1185 secondary. Multiple SOA queries may indicate the secondary is under 1186 attack. 1188 14.7. Reflection Attacks involving the Public Authoritative Servers 1190 Reflection attacks involving the Public Authoritative Server(s) are 1191 similar to attacks on any Outsourcing Infrastructure. This is not 1192 specific to the architecture described in this document, and thus are 1193 considered as out of scope. 1195 In fact, one motivation of the architecture described in this 1196 document is to expose the Public Authoritative Server(s) to attacks 1197 instead of the HNA, as it is believed that the Public Authoritative 1198 Server(s) will be better able to defend itself. 1200 14.8. Flooding Attack 1202 The purpose of flooding attacks is mostly resource exhaustion, where 1203 the resource can be bandwidth, memory, or CPU for example. 1205 One goal of the architecture described in this document is to limit 1206 the surface of attack on the HNA. This is done by outsourcing the 1207 DNS service to the Public Authoritative Server(s). By doing so, the 1208 HNA limits its DNS interactions between the Hidden Primary and the 1209 DM. This limits the number of entities the HNA interacts with as 1210 well as the scope of DNS exchanges - NOTIFY, SOA, AXFR, IXFR. 1212 The use of an authenticated channel with SIG(0) or TSIG between the 1213 HNA and the DM, enables detection of illegitimate DNS queries, so 1214 appropriate action may be taken - like dropping the queries. If 1215 signatures are validated, then most likely, the HNA is under a replay 1216 attack, as detailed in Section 14.9 1218 In order to limit the resource required for authentication, it is 1219 recommended to use TSIG that uses symmetric cryptography over SIG(0) 1220 that uses asymmetric cryptography. 1222 14.9. Replay Attack 1224 Replay attacks consist of an attacker either resending or delaying a 1225 legitimate message that has been sent by an authorized user or 1226 process. As the Hidden Primary and the DM use an authenticated 1227 channel, replay attacks are mostly expected to use forged DNS queries 1228 in order to provide valid traffic. 1230 From the perspective of an attacker, using a correctly authenticated 1231 DNS query may not be detected as an attack and thus may generate a 1232 response. Generating and sending a response consumes more resources 1233 than either dropping the query by the defender, or generating the 1234 query by the attacker, and thus could be used for resource exhaustion 1235 attacks. In addition, as the authentication is performed at the DNS 1236 layer, the source IP address could be impersonated in order to 1237 perform a reflection attack. 1239 Section 14.4 details how to mitigate reflection attacks and 1240 Section 14.8 details how to mitigate resource exhaustion. Both 1241 sections assume a context of DoS with a flood of DNS queries. This 1242 section suggests a way to limit the attack surface of replay attacks. 1244 As SIG(0) and TSIG use inception and expiration time, the time frame 1245 for replay attack is limited. SIG(0) and TSIG recommends a fudge 1246 value of 5 minutes. This value has been set as a compromise between 1247 possibly loose time synchronization between devices and the valid 1248 lifetime of the message. As a result, better time synchronization 1249 policies could reduce the time window of the attack. 1251 []() 1262 15. IANA Considerations 1264 This document has no actions for IANA. 1266 16. Acknowledgment 1268 The authors wish to thank Philippe Lemordant for its contributions on 1269 the early versions of the draft; Ole Troan for pointing out issues 1270 with the IPv6 routed home concept and placing the scope of this 1271 document in a wider picture; Mark Townsley for encouragement and 1272 injecting a healthy debate on the merits of the idea; Ulrik de Bie 1273 for providing alternative solutions; Paul Mockapetris, Christian 1274 Jacquenet, Francis Dupont and Ludovic Eschard for their remarks on 1275 HNA and low power devices; Olafur Gudmundsson for clarifying DNSSEC 1276 capabilities of small devices; Simon Kelley for its feedback as 1277 dnsmasq implementer; Andrew Sullivan, Mark Andrew, Ted Lemon, Mikael 1278 Abrahamson, Michael Richardson and Ray Bellis for their feedback on 1279 handling different views as well as clarifying the impact of 1280 outsourcing the zone signing operation outside the HNA; Mark Andrew 1281 and Peter Koch for clarifying the renumbering. 1283 17. Annex 1285 17.1. Envisioned deployment scenarios 1287 A number of deployment have been envisionned, this section aims at 1288 providing a brief description. The use cases are not limitatives and 1289 this section is not normative. 1291 17.1.1. CPE Vendor 1293 A specific vendor with specific relations with a registrar or a 1294 registry may sell a CPE that is provisioned with provisioned domain 1295 name. Such domain name does not need to be necessary human readable. 1297 One possible way is that the vendor also provisions the HNA with a 1298 private and public keys as well as a certificate. Note that these 1299 keys are not expected to be used for DNSSEC signing. Instead these 1300 keys are solely used by the HNA to proceed to the authentication. 1301 Normally the keys should be necessary and sufficient to proceed to 1302 the authentication. The reason to combine the domain name and the 1303 key is that outsourcing infrastructure are likely handle names better 1304 than keys and that domain names might be used as a login which 1305 enables the key to be regenerated. 1307 When the home network owner plugs the CPE at home, the relation 1308 between HNA and DM is expected to work out-of-the-box. 1310 17.1.2. Agnostic CPE 1312 An CPE that is not preconfigured may also take advanatge to the 1313 protocol defined in this document but some configuration steps will 1314 be needed. 1316 1. The owner of the home network buys a domain name to a registrar, 1317 and as such creates an account on that registrar 1319 2. Either the registrar is also providing the outsourcing 1320 infrastructure or the home network needs to create a specific 1321 account on the outsourcing infrastructure. * If the outsourcing 1322 provider is the registrar, the outsourcing has by design a proof 1323 of ownership of the domain name by the homenet owner. In this 1324 case, it is expected the infrastructure provides the necessary 1325 parameters to the home network owner to configure the HNA. A 1326 good way to provide the parameters would be the home network be 1327 able to copy/paste a JSON object. What matters at that point is 1328 the outsourcing infrastructure being able to generate 1329 authentication credentials for the HNA to authenticate itself to 1330 the outsourcing infrastructure. This obviously requires the home 1331 network to provide the public key gnerated by the HNA in a CSR. 1333 o If the outsourcing infrastructure is not the registrar, then the 1334 proof of ownership needs to be established using protocols like 1335 ACME for example that will end in the generation of a certificate. 1336 ACME is used here to the purpose of automating the generation of 1337 the certificate, the CA may be a specific CA or the outsourcing 1338 infrastructure. With that being done, the outsourcing 1339 infrastructure has a roof of ownership and can proceed as above. 1341 17.2. Example: Homenet Zone 1343 This section is not normative and intends to illustrate how the HNA 1344 builds the Homenet Zone. 1346 As depicted in Figure 1, the Public Homenet Zone is hosted on the 1347 Public Authoritative Server(s), whereas the Homenet Zone is hosted on 1348 the HNA. This section considers that the HNA builds the zone that 1349 will be effectively published on the Public Authoritative Server(s). 1350 In other words "Homenet to Public Zone transformation" is the 1351 identity also commonly designated as "no operation" (NOP). 1353 In that case, the Homenet Zone should configure its Name Server RRset 1354 (NS) and Start of Authority (SOA) with the values associated with the 1355 Public Authoritative Server(s). This is illustrated in Figure 2. 1356 public.primary.example.net is the FQDN of the Public Authoritative 1357 Server(s), and IP1, IP2, IP3, IP4 are the associated IP addresses. 1359 Then the HNA should add the additional new nodes that enter the home 1360 network, remove those that should be removed, and sign the Homenet 1361 Zone. 1363 $ORIGIN example.com 1364 $TTL 1h 1366 @ IN SOA public.primary.example.net 1367 hostmaster.example.com. ( 1368 2013120710 ; serial number of this zone file 1369 1d ; secondary refresh 1370 2h ; secondary retry time in case of a problem 1371 4w ; secondary expiration time 1372 1h ; maximum caching time in case of failed 1373 ; lookups 1374 ) 1376 @ NS public.authoritative.servers.example.net 1378 public.primary.example.net A @IP1 1379 public.primary.example.net A @IP2 1380 public.primary.example.net AAAA @IP3 1381 public.primary.example.net AAAA @IP4 1383 Figure 2: Homenet Zone 1385 The SOA RRset is defined in [RFC1033], [RFC1035] and [RFC2308]. This 1386 SOA is specific, as it is used for the synchronization between the 1387 Hidden Primary and the DM and published on the DNS Public 1388 Authoritative Server(s).. 1390 o MNAME: indicates the primary. In our case the zone is published 1391 on the Public Authoritative Server(s), and its name MUST be 1392 included. If multiple Public Authoritative Server(s) are 1393 involved, one of them MUST be chosen. More specifically, the HNA 1394 MUST NOT include the name of the Hidden Primary. 1396 o RNAME: indicates the email address to reach the administrator. 1397 [RFC2142] recommends using hostmaster@domain and replacing the '@' 1398 sign by '.'. 1400 o REFRESH and RETRY: indicate respectively in seconds how often 1401 secondaries need to check the primary, and the time between two 1402 refresh when a refresh has failed. Default values indicated by 1403 [RFC1033] are 3600 (1 hour) for refresh and 600 (10 minutes) for 1404 retry. This value might be too long for highly dynamic content. 1405 However, the Public Authoritative Server(s) and the HNA are 1406 expected to implement NOTIFY [RFC1996]. So whilst shorter refresh 1407 timers might increase the bandwidth usage for secondaries hosting 1408 large number of zones, it will have little practical impact on the 1409 elapsed time required to achieve synchronization between the 1410 Outsourcing Infrastructure and the Hidden Master. As a result, 1411 the default values are acceptable. 1413 o EXPIRE: is the upper limit data SHOULD be kept in absence of 1414 refresh. The default value indicated by [RFC1033] is 3600000 1415 (approx. 42 days). In home network architectures, the HNA 1416 provides both the DNS synchronization and the access to the home 1417 network. This device may be plugged and unplugged by the end user 1418 without notification, thus we recommend a long expiry timer. 1420 o MINIMUM: indicates the minimum TTL. The default value indicated 1421 by [RFC1033] is 86400 (1 day). For home network, this value MAY 1422 be reduced, and 3600 (1 hour) seems more appropriate. 1424 <> 1440 17.3. Example: HNA necessary parameters for outsourcing 1442 This section specifies the various parameters required by the HNA to 1443 configure the naming architecture of this document. This section is 1444 informational, and is intended to clarify the information handled by 1445 the HNA and the various settings to be done. 1447 DM may be configured with the following parameters. These parameters 1448 are necessary to establish a secure channel between the HNA and the 1449 DM as well as to specify the DNS zone that is in the scope of the 1450 communication: 1452 o DM: The associated FQDNs or IP addresses of the DM. IP addresses 1453 are optional and the FQDN is sufficient. To secure the binding 1454 name and IP addresses, a DNSSEC exchange is required. Otherwise, 1455 the IP addresses should be entered manually. 1457 o Authentication Method: How the HNA authenticates itself to the DM. 1458 This MAY depend on the implementation but this should cover at 1459 least IPsec, DTLS and TSIG 1461 o Authentication data: Associated Data. PSK only requires a single 1462 argument. If other authentication mechanisms based on 1463 certificates are used, then HNA private keys, certificates and 1464 certification authority should be specified. 1466 o Public Authoritative Server(s): The FQDN or IP addresses of the 1467 Public Authoritative Server(s). It MAY correspond to the data 1468 that will be set in the NS RRsets and SOA of the Homenet Zone. IP 1469 addresses are optional and the FQDN is sufficient. To secure the 1470 binding between name and IP addresses, a DNSSEC exchange is 1471 required. Otherwise, the IP addresses should be entered manually. 1473 o Registered Homenet Domain: The domain name used to establish the 1474 secure channel. This name is used by the DM and the HNA for the 1475 primary / secondary configuration as well as to index the NOTIFY 1476 queries of the HNA when the HNA has been renumbered. 1478 Setting the Homenet Zone requires the following information. 1480 o Registered Homenet Domain: The Domain Name of the zone. Multiple 1481 Registered Homenet Domains may be provided. This will generate 1482 the creation of multiple Public Homenet Zones. 1484 o Public Authoritative Server(s): The Public Authoritative Server(s) 1485 associated with the Registered Homenet Domain. Multiple Public 1486 Authoritative Server(s) may be provided. 1488 Two possible methods of providing the required information would be: 1490 JSON for forward zones [should be standardized in a similar way to 1491 zone file layout in RFC1035] 1493 DHCP for reverse zones [needs a separate draft] 1495 18. References 1496 18.1. Normative References 1498 [RFC1033] Lottor, M., "Domain Administrators Operations Guide", 1499 RFC 1033, DOI 10.17487/RFC1033, November 1987, 1500 . 1502 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1503 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1504 . 1506 [RFC1035] Mockapetris, P., "Domain names - implementation and 1507 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 1508 November 1987, . 1510 [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, 1511 DOI 10.17487/RFC1995, August 1996, 1512 . 1514 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 1515 Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996, 1516 August 1996, . 1518 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1519 Requirement Levels", BCP 14, RFC 2119, 1520 DOI 10.17487/RFC2119, March 1997, 1521 . 1523 [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, 1524 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1525 RFC 2136, DOI 10.17487/RFC2136, April 1997, 1526 . 1528 [RFC2142] Crocker, D., "Mailbox Names for Common Services, Roles and 1529 Functions", RFC 2142, DOI 10.17487/RFC2142, May 1997, 1530 . 1532 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 1533 Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997, 1534 . 1536 [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS 1537 NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, 1538 . 1540 [RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B. 1541 Wellington, "Secret Key Transaction Authentication for DNS 1542 (TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000, 1543 . 1545 [RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures 1546 ( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September 1547 2000, . 1549 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 1550 Rose, "Resource Records for the DNS Security Extensions", 1551 RFC 4034, DOI 10.17487/RFC4034, March 2005, 1552 . 1554 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 1555 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 1556 DOI 10.17487/RFC4192, September 2005, 1557 . 1559 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1560 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 1561 December 2005, . 1563 [RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol 1564 (MOBIKE)", RFC 4555, DOI 10.17487/RFC4555, June 2006, 1565 . 1567 [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", 1568 RFC 4960, DOI 10.17487/RFC4960, September 2007, 1569 . 1571 [RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS 1572 Security (DNSSEC) Hashed Authenticated Denial of 1573 Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008, 1574 . 1576 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1577 (TLS) Protocol Version 1.2", RFC 5246, 1578 DOI 10.17487/RFC5246, August 2008, 1579 . 1581 [RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol 1582 (AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010, 1583 . 1585 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 1586 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 1587 January 2012, . 1589 [RFC6644] Evans, D., Droms, R., and S. Jiang, "Rebind Capability in 1590 DHCPv6 Reconfigure Messages", RFC 6644, 1591 DOI 10.17487/RFC6644, July 2012, 1592 . 1594 [RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the 1595 DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012, 1596 . 1598 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 1599 DOI 10.17487/RFC6762, February 2013, 1600 . 1602 [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service 1603 Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, 1604 . 1606 [RFC7010] Liu, B., Jiang, S., Carpenter, B., Venaas, S., and W. 1607 George, "IPv6 Site Renumbering Gap Analysis", RFC 7010, 1608 DOI 10.17487/RFC7010, September 2013, 1609 . 1611 [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. 1612 Kivinen, "Internet Key Exchange Protocol Version 2 1613 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 1614 2014, . 1616 [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating 1617 DNSSEC Delegation Trust Maintenance", RFC 7344, 1618 DOI 10.17487/RFC7344, September 2014, 1619 . 1621 [RFC7368] Chown, T., Ed., Arkko, J., Brandt, A., Troan, O., and J. 1622 Weil, "IPv6 Home Networking Architecture Principles", 1623 RFC 7368, DOI 10.17487/RFC7368, October 2014, 1624 . 1626 [RFC7558] Lynn, K., Cheshire, S., Blanchet, M., and D. Migault, 1627 "Requirements for Scalable DNS-Based Service Discovery 1628 (DNS-SD) / Multicast DNS (mDNS) Extensions", RFC 7558, 1629 DOI 10.17487/RFC7558, July 2015, 1630 . 1632 [RFC7707] Gont, F. and T. Chown, "Network Reconnaissance in IPv6 1633 Networks", RFC 7707, DOI 10.17487/RFC7707, March 2016, 1634 . 1636 [RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking 1637 Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April 1638 2016, . 1640 [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D., 1641 and P. Hoffman, "Specification for DNS over Transport 1642 Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May 1643 2016, . 1645 [RFC8375] Pfister, P. and T. Lemon, "Special-Use Domain 1646 'home.arpa.'", RFC 8375, DOI 10.17487/RFC8375, May 2018, 1647 . 1649 18.2. Informative References 1651 [I-D.howard-dnsop-ip6rdns] 1652 Howard, L., "Reverse DNS in IPv6 for Internet Service 1653 Providers", draft-howard-dnsop-ip6rdns-00 (work in 1654 progress), June 2014. 1656 [I-D.ietf-homenet-naming-architecture-dhc-options] 1657 Migault, D., Mrugalski, T., Griffiths, C., Weber, R., and 1658 W. Cloetens, "DHCPv6 Options for Homenet Naming 1659 Architecture", draft-ietf-homenet-naming-architecture-dhc- 1660 options-06 (work in progress), June 2018. 1662 [I-D.ietf-homenet-simple-naming] 1663 Lemon, T., Migault, D., and S. Cheshire, "Homenet Naming 1664 and Service Discovery Architecture", draft-ietf-homenet- 1665 simple-naming-03 (work in progress), October 2018. 1667 [I-D.sury-dnsext-cname-dname] 1668 Sury, O., "CNAME+DNAME Name Redirection", draft-sury- 1669 dnsext-cname-dname-00 (work in progress), April 2010. 1671 Authors' Addresses 1673 Daniel Migault 1674 Ericsson 1675 8275 Trans Canada Route 1676 Saint Laurent, QC 4S 0B6 1677 Canada 1679 EMail: daniel.migault@ericsson.com 1680 Ralf Weber 1681 Nominum 1682 2000 Seaport Blvd 1683 Redwood City 94063 1684 US 1686 EMail: ralf.weber@nominum.com 1688 Michael Richardson 1689 Sandelman Software Works 1690 470 Dawson Avenue 1691 Ottawa, ON K1Z 5V7 1692 Canada 1694 EMail: mcr+ietf@sandelman.ca 1696 Ray Hunter 1697 Globis Consulting BV 1698 Weegschaalstraat 3 1699 Eindhoven 5632CW 1700 NL 1702 EMail: v6ops@globis.net 1704 Chris Griffiths 1706 EMail: cgriffiths@gmail.com 1708 Wouter Cloetens 1709 SoftAtHome 1710 vaartdijk 3 701 1711 Wijgmaal 3018 1712 BE 1714 EMail: wouter.cloetens@softathome.com