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Checking references for intended status: Informational ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) ** Obsolete normative reference: RFC 3633 (Obsoleted by RFC 8415) -- Obsolete informational reference (is this intentional?): RFC 4941 (Obsoleted by RFC 8981) -- Obsolete informational reference (is this intentional?): RFC 6145 (Obsoleted by RFC 7915) -- Obsolete informational reference (is this intentional?): RFC 6204 (Obsoleted by RFC 7084) -- Obsolete informational reference (is this intentional?): RFC 6555 (Obsoleted by RFC 8305) -- Obsolete informational reference (is this intentional?): RFC 6824 (Obsoleted by RFC 8684) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group T. Chown, Ed. 3 Internet-Draft University of Southampton 4 Intended status: Informational J. Arkko 5 Expires: September 5, 2014 Ericsson 6 A. Brandt 7 Sigma Designs 8 O. Troan 9 Cisco Systems, Inc. 10 J. Weil 11 Time Warner Cable 12 March 4, 2014 14 IPv6 Home Networking Architecture Principles 15 draft-ietf-homenet-arch-13 17 Abstract 19 This text describes evolving networking technology within residential 20 home networks with increasing numbers of devices and a trend towards 21 increased internal routing. The goal of this document is to define a 22 general architecture for IPv6-based home networking, describing the 23 associated principles, considerations and requirements. The text 24 briefly highlights specific implications of the introduction of IPv6 25 for home networking, discusses the elements of the architecture, and 26 suggests how standard IPv6 mechanisms and addressing can be employed 27 in home networking. The architecture describes the need for specific 28 protocol extensions for certain additional functionality. It is 29 assumed that the IPv6 home network is not actively managed, and runs 30 as an IPv6-only or dual-stack network. There are no recommendations 31 in this text for the IPv4 part of the network. 33 Status of this Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at http://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on September 5, 2014. 50 Copyright Notice 52 Copyright (c) 2014 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 (http://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. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 1.1. Terminology and Abbreviations . . . . . . . . . . . . . . 5 69 2. Effects of IPv6 on Home Networking . . . . . . . . . . . . . . 6 70 2.1. Multiple subnets and routers . . . . . . . . . . . . . . . 7 71 2.2. Global addressability and elimination of NAT . . . . . . . 8 72 2.3. Multi-Addressing of devices . . . . . . . . . . . . . . . 8 73 2.4. Unique Local Addresses (ULAs) . . . . . . . . . . . . . . 9 74 2.5. Avoiding manual configuration of IP addresses . . . . . . 10 75 2.6. IPv6-only operation . . . . . . . . . . . . . . . . . . . 11 76 3. Homenet Architecture Principles . . . . . . . . . . . . . . . 11 77 3.1. General Principles . . . . . . . . . . . . . . . . . . . . 12 78 3.1.1. Reuse existing protocols . . . . . . . . . . . . . . . 12 79 3.1.2. Minimise changes to hosts and routers . . . . . . . . 12 80 3.2. Homenet Topology . . . . . . . . . . . . . . . . . . . . . 13 81 3.2.1. Supporting arbitrary topologies . . . . . . . . . . . 13 82 3.2.2. Network topology models . . . . . . . . . . . . . . . 13 83 3.2.3. Dual-stack topologies . . . . . . . . . . . . . . . . 18 84 3.2.4. Multihoming . . . . . . . . . . . . . . . . . . . . . 19 85 3.2.5. Mobility support . . . . . . . . . . . . . . . . . . . 20 86 3.3. A Self-Organising Network . . . . . . . . . . . . . . . . 20 87 3.3.1. Differentiating neighbouring homenets . . . . . . . . 21 88 3.3.2. Largest practical subnets . . . . . . . . . . . . . . 21 89 3.3.3. Handling varying link technologies . . . . . . . . . . 22 90 3.3.4. Homenet realms and borders . . . . . . . . . . . . . . 22 91 3.3.5. Configuration information from the ISP . . . . . . . . 23 92 3.4. Homenet Addressing . . . . . . . . . . . . . . . . . . . . 23 93 3.4.1. Use of ISP-delegated IPv6 prefixes . . . . . . . . . . 24 94 3.4.2. Stable internal IP addresses . . . . . . . . . . . . . 26 95 3.4.3. Internal prefix delegation . . . . . . . . . . . . . . 27 96 3.4.4. Coordination of configuration information . . . . . . 28 97 3.4.5. Privacy . . . . . . . . . . . . . . . . . . . . . . . 28 98 3.5. Routing functionality . . . . . . . . . . . . . . . . . . 28 99 3.5.1. Multicast support . . . . . . . . . . . . . . . . . . 30 100 3.6. Security . . . . . . . . . . . . . . . . . . . . . . . . . 31 101 3.6.1. Addressability vs reachability . . . . . . . . . . . . 31 102 3.6.2. Filtering at borders . . . . . . . . . . . . . . . . . 32 103 3.6.3. Partial Effectiveness of NAT and Firewalls . . . . . . 32 104 3.6.4. Exfiltration concerns . . . . . . . . . . . . . . . . 33 105 3.6.5. Device capabilities . . . . . . . . . . . . . . . . . 33 106 3.6.6. ULAs as a hint of connection origin . . . . . . . . . 33 107 3.7. Naming and Service Discovery . . . . . . . . . . . . . . . 33 108 3.7.1. Discovering services . . . . . . . . . . . . . . . . . 34 109 3.7.2. Assigning names to devices . . . . . . . . . . . . . . 35 110 3.7.3. The homenet name service . . . . . . . . . . . . . . . 35 111 3.7.4. Name spaces . . . . . . . . . . . . . . . . . . . . . 36 112 3.7.5. Independent operation . . . . . . . . . . . . . . . . 38 113 3.7.6. Considerations for LLNs . . . . . . . . . . . . . . . 39 114 3.7.7. DNS resolver discovery . . . . . . . . . . . . . . . . 39 115 3.7.8. Devices roaming to/from the homenet . . . . . . . . . 39 116 3.8. Other Considerations . . . . . . . . . . . . . . . . . . . 40 117 3.8.1. Quality of Service . . . . . . . . . . . . . . . . . . 40 118 3.8.2. Operations and Management . . . . . . . . . . . . . . 40 119 3.9. Implementing the Architecture on IPv6 . . . . . . . . . . 41 120 4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 42 121 5. Security Considerations . . . . . . . . . . . . . . . . . . . 42 122 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 123 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42 124 7.1. Normative References . . . . . . . . . . . . . . . . . . . 42 125 7.2. Informative References . . . . . . . . . . . . . . . . . . 43 126 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 45 127 Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . . 46 128 B.1. Version 13 . . . . . . . . . . . . . . . . . . . . . . . . 46 129 B.2. Version 12 . . . . . . . . . . . . . . . . . . . . . . . . 46 130 B.3. Version 11 (after IESG review) . . . . . . . . . . . . . . 46 131 B.4. Version 10 (after AD review) . . . . . . . . . . . . . . . 47 132 B.5. Version 09 (after WGLC) . . . . . . . . . . . . . . . . . 47 133 B.6. Version 08 . . . . . . . . . . . . . . . . . . . . . . . . 48 134 B.7. Version 07 . . . . . . . . . . . . . . . . . . . . . . . . 48 135 B.8. Version 06 . . . . . . . . . . . . . . . . . . . . . . . . 49 136 B.9. Version 05 . . . . . . . . . . . . . . . . . . . . . . . . 49 137 B.10. Version 04 . . . . . . . . . . . . . . . . . . . . . . . . 49 138 B.11. Version 03 . . . . . . . . . . . . . . . . . . . . . . . . 50 139 B.12. Version 02 . . . . . . . . . . . . . . . . . . . . . . . . 51 140 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52 142 1. Introduction 144 This document focuses on evolving networking technology within 145 residential home networks with increasing numbers of devices and a 146 trend towards increased internal routing, and the associated 147 challenges with their deployment and operation. There is a growing 148 trend in home networking for the proliferation of networking 149 technology through an increasingly broad range of devices and media. 150 This evolution in scale and diversity sets requirements on IETF 151 protocols. Some of these requirements relate to the introduction of 152 IPv6, others to the introduction of specialised networks for home 153 automation and sensors. 155 While at the time of writing some complex home network topologies 156 exist, most are relatively simple single subnet networks, and 157 ostensibly operate using just IPv4. While there may be IPv6 traffic 158 within the network, e.g., for service discovery, the homenet is 159 provisioned by the ISP as an IPv4 network. Such networks also 160 typically employ solutions that should be avoided, such as private 161 [RFC1918] addressing with (cascaded) network address translation 162 (NAT) [RFC3022], or they may require expert assistance to set up. 164 In contrast, emerging IPv6-capable home networks are very likely to 165 have multiple internal subnets, e.g., to facilitate private and guest 166 networks, heterogeneous link layers, and smart grid components, and 167 have enough address space available to allow every device to have a 168 globally unique address. This implies that internal routing 169 functionality is required, and that the homenet's ISP both provides a 170 large enough prefix to allocate a prefix to each subnet, and that a 171 method is supported for such prefixes to be delegated efficiently to 172 those subnets. 174 It is not practical to expect home users to configure their networks. 175 Thus the assumption of this document is that the homenet is as far as 176 possible self-organising and self-configuring, i.e., it should 177 function without pro-active management by the residential user. 179 The architectural constructs in this document are focused on the 180 problems to be solved when introducing IPv6, with an eye towards a 181 better result than what we have today with IPv4, as well as aiming at 182 a more consistent solution that addresses as many of the identified 183 requirements as possible. The document aims to provide the basis and 184 guiding principles for how standard IPv6 mechanisms and addressing 185 [RFC2460] [RFC4291] can be employed in home networking, while 186 coexisting with existing IPv4 mechanisms. In emerging dual-stack 187 home networks it is vital that introducing IPv6 does not adversely 188 affect IPv4 operation. We assume that the IPv4 network architecture 189 in home networks is what it is, and can not be modified by new 190 recommendations. This document does not discuss how IPv4 home 191 networks provision or deliver support for multiple subnets. It 192 should not be assumed that any future new functionality created with 193 IPv6 in mind will be backward-compatible to include IPv4 support. 194 Further, future deployments, or specific subnets within an otherwise 195 dual-stack home network, may be IPv6-only, in which case 196 considerations for IPv4 impact would not apply. 198 This document proposes a baseline homenet architecture, using 199 protocols and implementations that are as far as possible proven and 200 robust. The scope of the document is primarily the network layer 201 technologies that provide the basic functionality to enable 202 addressing, connectivity, routing, naming and service discovery. 203 While it may, for example, state that homenet components must be 204 simple to deploy and use, it does not discuss specific user 205 interfaces, nor does it discuss specific physical, wireless or data- 206 link layer considerations. Likewise, we also do not specify the 207 whole design of a homenet router from top to bottom, rather we focus 208 on the Layer 3 aspects. This means that Layer 2 is largely out of 209 scope, we're assuming a data link layer that supports IPv6 is 210 present, and that we react accordingly. Any IPv6-over-Foo 211 definitions occur elsewhere. 213 [RFC6204] defines basic requirements for customer edge routers 214 (CERs). This document has recently been updated with the definition 215 of requirements for specific transition tools on the CER in 216 [RFC7084], specifically DS-Lite [RFC6333] and 6rd [RFC5969]. Such 217 detailed specification of CER devices is considered out of scope of 218 this architecture document, and we assume that any required update of 219 the CER device specification as a result of adopting this 220 architecture will be handled as separate and specific updates to 221 these existing documents. Further, the scope of this text is the 222 internal homenet, and thus specific features on the WAN side of the 223 CER are out of scope for this text. 225 1.1. Terminology and Abbreviations 227 In this section we define terminology and abbreviations used 228 throughout the text. 230 o Border: a point, typically resident on a router, between two 231 networks, e.g., between the main internal homenet and a guest 232 network. This defines point(s) at which filtering and forwarding 233 policies for different types of traffic may be applied. 235 o CER: Customer Edge Router: A border router intended for use in a 236 homenet, which connects the homenet to a service provider network. 238 o FQDN: Fully Qualified Domain Name. A globally unique name. 240 o Guest network: A part of the home network intended for use by 241 visitors or guests to the home(net). Devices on the guest network 242 may typically not see or be able to use all services in the 243 home(net). 245 o Homenet: A home network, comprising host and router equipment, 246 with one or more CERs providing connectivity to service provider 247 network(s). 249 o Internet Service Provider (ISP): an entity that provides access to 250 the Internet. In this document, a service provider specifically 251 offers Internet access using IPv6, and may also offer IPv4 252 Internet access. The service provider can provide such access 253 over a variety of different transport methods such as DSL, cable, 254 wireless, and others. 256 o LLN: Low-power and lossy network. 258 o LQDN: Locally Qualified Domain Name. A name local to the homenet. 260 o NAT: Network Address Translation. Typically referring to IPv4 261 Network Address and Port Translation (NAPT) [RFC3022]. 263 o NPTv6: Network Prefix Translation for IPv6 [RFC6296]. 265 o PCP: Port Control Protocol [RFC6887]. 267 o Realm: a network delimited by a defined border. A guest network 268 within a homenet may form one realm. 270 o 'Simple Security'. Defined in [RFC4864] and expanded further in 271 [RFC6092]; describes recommended perimeter security capabilities 272 for IPv6 networks. 274 o ULA: IPv6 Unique Local Address [RFC4193]. 276 o VM: Virtual machine. 278 2. Effects of IPv6 on Home Networking 280 While IPv6 resembles IPv4 in many ways, there are some notable 281 differences in the way it may typically be deployed. It changes 282 address allocation principles, making multi-addressing the norm, and, 283 through the vastly increased address space, allows globally unique IP 284 addresses to be used for all devices in a home network. This section 285 presents an overview of some of the key implications of the 286 introduction of IPv6 for home networking, that are simultaneously 287 both promising and problematic. 289 2.1. Multiple subnets and routers 291 While simple layer 3 topologies involving as few subnets as possible 292 are preferred in home networks, the incorporation of dedicated 293 (routed) subnets remains necessary for a variety of reasons. For 294 instance, an increasingly common feature in modern home routers is 295 the ability to support both guest and private network subnets. 296 Likewise, there may be a need to separate home automation or 297 corporate extension LANs (whereby a home worker can have their 298 corporate network extended into the home using a virtual private 299 network, commonly presented as one port on an Ethernet device) from 300 the main Internet access network, or different subnets may in general 301 be associated with parts of the homenet that have different routing 302 and security policies. Further, link layer networking technology is 303 poised to become more heterogeneous, as networks begin to employ both 304 traditional Ethernet technology and link layers designed for low- 305 power and lossy networks (LLNs), such as those used for certain types 306 of sensor devices. Constraining the flow of certain traffic from 307 Ethernet links to much lower capacity links thus becomes an important 308 topic. 310 The introduction of IPv6 for home networking makes it possible for 311 every home network to be delegated enough address space from its ISP 312 to provision globally unique prefixes for each such subnet in the 313 home. While the number of addresses in a standard /64 IPv6 prefix is 314 practically unlimited, the number of prefixes available for 315 assignment to the home network is not. As a result the growth 316 inhibitor for the home network shifts from the number of addresses to 317 the number of prefixes offered by the provider; this topic is 318 discussed in [RFC6177] (BCP 157), which recommends that "end sites 319 always be able to obtain a reasonable amount of address space for 320 their actual and planned usage". 322 The addition of routing between subnets raises a number of issues. 323 One is a method by which prefixes can be efficiently allocated to 324 each subnet, without user intervention. Another is the issue of how 325 to extend mechanisms such as zero configuration service discovery 326 which currently only operate within a single subnet using link-local 327 traffic. In a typical IPv4 home network, there is only one subnet, 328 so such mechanisms would normally operate as expected. For multi- 329 subnet IPv6 home networks there are two broad choices to enable such 330 protocols to work across the scope of the entire homenet; extend 331 existing protocols to work across that scope, or introduce proxies 332 for existing link layer protocols. This topic is discussed in 333 Section 3.7. 335 2.2. Global addressability and elimination of NAT 337 The possibility for direct end-to-end communication on the Internet 338 to be restored by the introduction of IPv6 is on the one hand an 339 incredible opportunity for innovation and simpler network operation, 340 but on the other hand it is also a concern as it potentially exposes 341 nodes in the internal networks to receipt of unwanted and possibly 342 malicious traffic from the Internet. 344 With devices and applications able to talk directly to each other 345 when they have globally unique addresses, there may be an expectation 346 of improved host security to compensate for this. It should be noted 347 that many devices may (for example) ship with default settings that 348 make them readily vulnerable to compromise by external attackers if 349 globally accessible, or may simply not have robustness designed-in 350 because it was either assumed such devices would only be used on 351 private networks or the device itself doesn't have the computing 352 power to apply the necessary security methods. In addition, the 353 upgrade cycle for devices (or their firmware) may be slow, and/or 354 lack auto-update mechanisms. 356 It is thus important to distinguish between addressability and 357 reachability. While IPv6 offers global addressability through use of 358 globally unique addresses in the home, whether devices are globally 359 reachable or not would depend on any firewall or filtering 360 configuration, and not, as is commonly the case with IPv4, the 361 presence or use of NAT. In this respect, IPv6 networks may or may 362 not have filters applied at their borders to control such traffic, 363 i.e., at the homenet CER. [RFC4864] and [RFC6092] discuss such 364 filtering, and the merits of 'default allow' against 'default deny' 365 policies for external traffic initiated into a homenet. This topic 366 is discussed further in Section 3.6.1. 368 2.3. Multi-Addressing of devices 370 In an IPv6 network, devices will often acquire multiple addresses, 371 typically at least a link-local address and one or more globally 372 unique addresses. Where a homenet is multihomed, a device would 373 typically receive a globally unique address (GUA) from within the 374 delegated prefix from each upstream ISP. Devices may also have an 375 IPv4 address if the network is dual-stack, an IPv6 Unique Local 376 Address (ULA) [RFC4193] (see below), and one or more IPv6 Privacy 377 Addresses [RFC4941]. 379 It should thus be considered the norm for devices on IPv6 home 380 networks to be multi-addressed, and to need to make appropriate 381 address selection decisions for the candidate source and destination 382 address pairs for any given connection. In multihoming scenarios 383 nodes will be configured with one address from each upstream ISP 384 prefix. In such cases the presence of upstream BCP 38 [RFC2827] 385 ingress filtering requires such multi-addressed nodes to select the 386 correct source address to be used for the corresponding uplink. 387 Default Address Selection for IPv6 [RFC6724] provides a solution for 388 this, but a challenge here is that the node may not have the 389 information it needs to make that decision based on addresses alone. 390 We discuss this challenge in Section 3.2.4. 392 2.4. Unique Local Addresses (ULAs) 394 [RFC4193] defines Unique Local Addresses (ULAs) for IPv6 that may be 395 used to address devices within the scope of a single site. Support 396 for ULAs for IPv6 CERs is described in [RFC6204]. A home network 397 running IPv6 should deploy ULAs alongside its globally unique 398 prefix(es) to allow stable communication between devices (on 399 different subnets) within the homenet where that externally allocated 400 globally unique prefix may change over time, e.g., due to renumbering 401 within the subscriber's ISP, or where external connectivity may be 402 temporarily unavailable. A homenet using provider-assigned global 403 addresses is exposed to its ISP renumbering the network to a much 404 larger degree than before whereas, for IPv4, NAT isolated the user 405 against ISP renumbering to some extent. 407 While setting up a network there may be a period where it has no 408 external connectivity, in which case ULAs would be required for 409 inter-subnet communication. In the case where home automation 410 networks are being set up in a new home/deployment (as early as 411 during construction of the home), such networks will likely need to 412 use their own /48 ULA prefix. Depending upon circumstances beyond 413 the control of the owner of the homenet, it may be impossible to 414 renumber the ULA used by the home automation network so routing 415 between ULA /48s may be required. Also, some devices, particularly 416 constrained devices, may have only a ULA (in addition to a link- 417 local), while others may have both a GUA and a ULA. 419 Note that unlike private IPv4 RFC 1918 space, the use of ULAs does 420 not imply use of an IPv6 equivalent of a traditional IPv4 NAT 421 [RFC3022], or of NPTv6 prefix-based NAT [RFC6296]. When an IPv6 node 422 in a homenet has both a ULA and a globally unique IPv6 address, it 423 should only use its ULA address internally, and use its additional 424 globally unique IPv6 address as a source address for external 425 communications. This should be the natural behaviour given support 426 for Default Address Selection for IPv6 [RFC6724]. By using such 427 globally unique addresses between hosts and devices in remote 428 networks, the architectural cost and complexity, particularly to 429 applications, of NAT or NPTv6 translation is avoided. As such, 430 neither IPv6 NAT or NPTv6 is recommended for use in the homenet 431 architecture. Further, the homenet border router(s) should filter 432 packets with ULA source/destination addresses as discussed in 433 Section 3.4.2. 435 Devices in a homenet may be given only a ULA as a means to restrict 436 reachability from outside the homenet. ULAs can be used by default 437 for devices that, without additional configuration (e.g., via a web 438 interface), would only offer services to the internal network. For 439 example, a printer might only accept incoming connections on a ULA 440 until configured to be globally reachable, at which point it acquires 441 a global IPv6 address and may be advertised via a global name space. 443 Where both a ULA and a global prefix are in use, the ULA source 444 address is used to communicate with ULA destination addresses when 445 appropriate, i.e., when the ULA source and destination lie within the 446 /48 ULA prefix(es) known to be used within the same homenet. In 447 cases where multiple /48 ULA prefixes are in use within a single 448 homenet (perhaps because multiple homenet routers each independently 449 auto-generate a /48 ULA prefix and then share prefix/routing 450 information), utilising a ULA source address and a ULA destination 451 address from two disjoint internal ULA prefixes is preferable to 452 using GUAs. 454 While a homenet should operate correctly with two or more /48 ULAs 455 enabled, a mechanism for the creation and use of a single /48 ULA 456 prefix is desirable for addressing consistency and policy 457 enforcement. 459 A counter-argument to using ULAs is that it is undesirable to 460 aggressively deprecate global prefixes for temporary loss of 461 connectivity, so for a host to lose its global address there would 462 have to be a connection breakage longer than the lease period, and 463 even then, deprecating prefixes when there is no connectivity may not 464 be advisable. However, it is assumed in this architecture that 465 homenets should support and use ULAs. 467 2.5. Avoiding manual configuration of IP addresses 469 Some IPv4 home networking devices expose IPv4 addresses to users, 470 e.g., the IPv4 address of a home IPv4 CER that may be configured via 471 a web interface. In potentially complex future IPv6 homenets, users 472 should not be expected to enter IPv6 literal addresses in devices or 473 applications, given their much greater length and the apparent 474 randomness of such addresses to a typical home user. Thus, even for 475 the simplest of functions, simple naming and the associated (minimal, 476 and ideally zero configuration) discovery of services is imperative 477 for the easy deployment and use of homenet devices and applications. 479 2.6. IPv6-only operation 481 It is likely that IPv6-only networking will be deployed first in new 482 home network deployments, often refered to as 'greenfield' scenarios, 483 where there is no existing IPv4 capability, or perhaps as one element 484 of an otherwise dual-stack network. Running IPv6-only adds 485 additional requirements, e.g., for devices to get configuration 486 information via IPv6 transport (not relying on an IPv4 protocol such 487 as IPv4 DHCP), and for devices to be able to initiate communications 488 to external devices that are IPv4-only. 490 Some specific transition technologies which may be deployed by the 491 homenet's ISP are discussed in [RFC7084]. In addition, certain other 492 functions may be desirable on the CER, e.g., to access content in the 493 IPv4 Internet, NAT64 [RFC6144] and DNS64 [RFC6145] may be applicable. 495 The widespread availability of robust solutions to these types of 496 requirements will help accelerate the uptake of IPv6-only homenets. 497 The specifics of these are however beyond the scope of this document, 498 especially those functions that reside on the CER. 500 3. Homenet Architecture Principles 502 The aim of this text is to outline how to construct advanced IPv6- 503 based home networks involving multiple routers and subnets using 504 standard IPv6 addressing and protocols [RFC2460] [RFC4291] as the 505 basis. As described in Section 3.1, solutions should as far as 506 possible re-use existing protocols, and minimise changes to hosts and 507 routers, but some new protocols, or extensions, are likely to be 508 required. In this section, we present the elements of the proposed 509 home networking architecture, with discussion of the associated 510 design principles. 512 In general, home network equipment needs to be able to operate in 513 networks with a range of different properties and topologies, where 514 home users may plug components together in arbitrary ways and expect 515 the resulting network to operate. Significant manual configuration 516 is rarely, if at all, possible, or even desirable given the knowledge 517 level of typical home users. Thus the network should, as far as 518 possible, be self-configuring, though configuration by advanced users 519 should not be precluded. 521 The homenet needs to be able to handle or provision at least 522 o Routing 524 o Prefix configuration for routers 526 o Name resolution 528 o Service discovery 530 o Network security 532 The remainder of this document describes the principles by which the 533 homenet architecture may deliver these properties. 535 3.1. General Principles 537 There is little that the Internet standards community can do about 538 the physical topologies or the need for some networks to be separated 539 at the network layer for policy or link layer compatibility reasons. 540 However, there is a lot of flexibility in using IP addressing and 541 inter-networking mechanisms. This text discusses how such 542 flexibility should be used to provide the best user experience and 543 ensure that the network can evolve with new applications in the 544 future. The principles described in this text should be followed 545 when designing homenet protocol solutions. 547 3.1.1. Reuse existing protocols 549 Existing protocols will be used to meet the requirements of home 550 networks. Where necessary, extensions will be made to those 551 protocols. When no existing protocol is found to be suitable, a new 552 or emerging protocol may be used. Therefore, it is important that no 553 design or architectural decisions are made that would preclude the 554 use of new or emerging protocols. 556 A generally conservative approach, giving weight to running (and 557 available) code, is preferable. Where new protocols are required, 558 evidence of commitment to implementation by appropriate vendors or 559 development communities is highly desirable. Protocols used should 560 be backwardly compatible, and forward compatible where changes are 561 made. 563 3.1.2. Minimise changes to hosts and routers 565 In order to maximise deployability of new homenets, where possible 566 any requirement for changes to hosts and routers should be minimised, 567 though solutions which, for example, incrementally improve capability 568 with host or router changes may be acceptable. There may be cases 569 where changes are unavoidable, e.g., to allow a given homenet routing 570 protocol to be self-configuring, or to support routing based on 571 sources addresses in addition to destination addresses (to improve 572 multihoming support, as discussed in Section 3.2.4). 574 3.2. Homenet Topology 576 This section considers homenet topologies, and the principles that 577 may be applied in designing an architecture to support as wide a 578 range of such topologies as possible. 580 3.2.1. Supporting arbitrary topologies 582 There should ideally be no built-in assumptions about the topology in 583 home networks, as users are capable of connecting their devices in 584 'ingenious' ways. Thus arbitrary topologies and arbitrary routing 585 will need to be supported, or at least the failure mode for when the 586 user makes a mistake should be as robust as possible, e.g., de- 587 activating a certain part of the infrastructure to allow the rest to 588 operate. In such cases, the user should ideally have some useful 589 indication of the failure mode encountered. 591 There should be no topology scenarios which cause loss of 592 connectivity, except when the user creates a physical island within 593 the topology. Some potentially pathological cases that can be 594 created include bridging ports of a router together, however this 595 case can be detected and dealt with by the router. Loops within a 596 routed topology are in a sense good in that they offer redundancy. 597 Topologies that include potential bridging loops can be dangerous but 598 are also detectable when a switch learns the MAC of one of its 599 interfaces on another or runs a spanning tree or link state protocol. 600 It is only topologies with such potential loops using simple 601 repeaters that are truly pathological. 603 The topology of the homenet may change over time, due to the addition 604 or removal of equipment, but also due to temporary failures or 605 connectivity problems. In some cases this may lead to, for example, 606 a multihomed homenet being split into two isolated homenets, or, 607 after such a fault is remedied, two isolated parts reconfiguring back 608 to a single network. 610 3.2.2. Network topology models 612 As hinted above, while the architecture may focus on likely common 613 topologies, it should not preclude any arbitrary topology from being 614 constructed. 616 Most IPv4 home network models at the time of writing tend to be 617 relatively simple, typically a single NAT router to the ISP and a 618 single internal subnet but, as discussed earlier, evolution in 619 network architectures is driving more complex topologies, such as the 620 separation of guest and private networks. There may also be some 621 cascaded IPv4 NAT scenarios, which we mention in the next section. 622 For IPv6 homenets, the Network Architectures described in [RFC6204] 623 and its successor [RFC7084] should, as a minimum, be supported. 625 There are a number of properties or attributes of a home network that 626 we can use to describe its topology and operation. The following 627 properties apply to any IPv6 home network: 629 o Presence of internal routers. The homenet may have one or more 630 internal routers, or may only provide subnetting from interfaces 631 on the CER. 633 o Presence of isolated internal subnets. There may be isolated 634 internal subnets, with no direct connectivity between them within 635 the homenet (with each having its own external connectivity). 636 Isolation may be physical, or implemented via IEEE 802.1q VLANs. 637 The latter is however not something a typical user would be 638 expected to configure. 640 o Demarcation of the CER. The CER(s) may or may not be managed by 641 the ISP. If the demarcation point is such that the customer can 642 provide or manage the CER, its configuration must be simple. Both 643 models must be supported. 645 Various forms of multihoming are likely to become more prevalent with 646 IPv6 home networks, where the homenet may have two or more external 647 ISP connections, as discussed further below. Thus the following 648 properties should also be considered for such networks: 650 o Number of upstream providers. The majority of home networks today 651 consist of a single upstream ISP, but it may become more common in 652 the future for there to be multiple ISPs, whether for resilience 653 or provision of additional services. Each would offer its own 654 prefix. Some may or may not provide a default route to the public 655 Internet. 657 o Number of CERs. The homenet may have a single CER, which might be 658 used for one or more providers, or multiple CERs. The presence of 659 multiple CERs adds additional complexity for multihoming 660 scenarios, and protocols like PCP that may need to manage 661 connection-oriented state mappings on the same CER as used for 662 subsequent traffic flows. 664 In the following sections we give some examples of the types of 665 homenet topologies we may see in the future. This is not intended to 666 be an exhaustive or complete list, rather an indicative one to 667 facilitate the discussion in this text. 669 3.2.2.1. A: Single ISP, Single CER, Internal routers 671 Figure 1 shows a home network with multiple local area networks. 672 These may be needed for reasons relating to different link layer 673 technologies in use or for policy reasons, e.g., classic Ethernet in 674 one subnet and a LLN link layer technology in another. In this 675 example there is no single router that a priori understands the 676 entire topology. The topology itself may also be complex, and it may 677 not be possible to assume a pure tree form, for instance (because 678 home users may plug routers together to form arbitrary topologies 679 including those with potential loops in them). 681 +-------+-------+ \ 682 | Service | \ 683 | Provider | | Service 684 | Router | | Provider 685 +-------+-------+ | network 686 | / 687 | Customer / 688 | Internet connection 689 | 690 +------+--------+ \ 691 | IPv6 | \ 692 | Customer Edge | \ 693 | Router | | 694 +----+-+---+----+ | 695 Network A | | | Network B(E) | 696 ----+-------------+----+ | +---+-------------+------+ | 697 | | | | | | | 698 +----+-----+ +-----+----+ | +----+-----+ +-----+----+ | | 699 |IPv6 Host | |IPv6 Host | | | IPv6 Host| |IPv6 Host | | | 700 | H1 | | H2 | | | H3 | | H4 | | | 701 +----------+ +----------+ | +----------+ +----------+ | | 702 | | | | | 703 Link F | ---+------+------+-----+ | 704 | | Network E(B) | 705 +------+--------+ | | End-User 706 | IPv6 | | | networks 707 | Interior +------+ | 708 | Router | | 709 +---+-------+-+-+ | 710 Network C | | Network D | 711 ----+-------------+---+ +---+-------------+--- | 712 | | | | | 713 +----+-----+ +-----+----+ +----+-----+ +-----+----+ | 714 |IPv6 Host | |IPv6 Host | | IPv6 Host| |IPv6 Host | | 715 | H5 | | H6 | | H7 | | H8 | / 716 +----------+ +----------+ +----------+ +----------+ / 718 Figure 1 720 In this diagram there is one CER. It has a single uplink interface. 721 It has three additional interfaces connected to Network A, Link F, 722 and Network B. IPv6 Internal Router (IR) has four interfaces 723 connected to Link F, Network C, Network D and Network E. Network B 724 and Network E have been bridged, likely inadvertently. This could be 725 as a result of connecting a wire between a switch for Network B and a 726 switch for Network E. 728 Any of logical Networks A through F might be wired or wireless. 730 Where multiple hosts are shown, this might be through one or more 731 physical ports on the CER or IPv6 (IR), wireless networks, or through 732 one or more layer-2 only Ethernet switches. 734 3.2.2.2. B: Two ISPs, Two CERs, Shared subnet 736 +-------+-------+ +-------+-------+ \ 737 | Service | | Service | \ 738 | Provider A | | Provider B | | Service 739 | Router | | Router | | Provider 740 +------+--------+ +-------+-------+ | network 741 | | / 742 | Customer | / 743 | Internet connections | / 744 | | 745 +------+--------+ +-------+-------+ \ 746 | IPv6 | | IPv6 | \ 747 | Customer Edge | | Customer Edge | \ 748 | Router 1 | | Router 2 | / 749 +------+--------+ +-------+-------+ / 750 | | / 751 | | | End-User 752 ---+---------+---+---------------+--+----------+--- | network(s) 753 | | | | \ 754 +----+-----+ +-----+----+ +----+-----+ +-----+----+ \ 755 |IPv6 Host | |IPv6 Host | | IPv6 Host| |IPv6 Host | / 756 | H1 | | H2 | | H3 | | H4 | / 757 +----------+ +----------+ +----------+ +----------+ 759 Figure 2 761 Figure 2 illustrates a multihomed homenet model, where the customer 762 has connectivity via CER1 to ISP A and via CER2 to ISP B. This 763 example shows one shared subnet where IPv6 nodes would potentially be 764 multihomed and receive multiple IPv6 global prefixes, one per ISP. 765 This model may also be combined with that shown in Figure 1 to create 766 a more complex scenario with multiple internal routers. Or the above 767 shared subnet may be split in two, such that each CER serves a 768 separate isolated subnet, which is a scenario seen with some IPv4 769 networks today. 771 3.2.2.3. C: Two ISPs, One CER, Shared subnet 773 +-------+-------+ +-------+-------+ \ 774 | Service | | Service | \ 775 | Provider A | | Provider B | | Service 776 | Router | | Router | | Provider 777 +-------+-------+ +-------+-------+ | network 778 | | / 779 | Customer | / 780 | Internet | / 781 | connections | 782 +---------+---------+ \ 783 | IPv6 | \ 784 | Customer Edge | \ 785 | Router | / 786 +---------+---------+ / 787 | / 788 | | End-User 789 ---+------------+-------+--------+-------------+--- | network(s) 790 | | | | \ 791 +----+-----+ +----+-----+ +----+-----+ +-----+----+ \ 792 |IPv6 Host | |IPv6 Host | | IPv6 Host| |IPv6 Host | / 793 | H1 | | H2 | | H3 | | H4 | / 794 +----------+ +----------+ +----------+ +----------+ 796 Figure 3 798 Figure 3 illustrates a model where a home network may have multiple 799 connections to multiple providers or multiple logical connections to 800 the same provider, with shared internal subnets. 802 3.2.3. Dual-stack topologies 804 It is expected that most homenet deployments will for the immediate 805 future be dual-stack IPv4/IPv6. In such networks it is important not 806 to introduce new IPv6 capabilities that would cause a failure if used 807 alongside IPv4+NAT, given that such dual-stack homenets will be 808 commonplace for some time. That said, it is desirable that IPv6 809 works better than IPv4 in as many scenarios as possible. Further, 810 the homenet architecture must operate in the absence of IPv4. 812 A general recommendation is to follow the same topology for IPv6 as 813 is used for IPv4, but not to use NAT. Thus there should be routed 814 IPv6 where an IPv4 NAT is used and, where there is no NAT, routing or 815 bridging may be used. Routing may have advantages when compared to 816 bridging together high speed and lower speed shared media, and in 817 addition bridging may not be suitable for some networks, such as ad- 818 hoc mobile networks. 820 In some cases IPv4 home networks may feature cascaded NATs. End 821 users are frequently unaware that they have created such networks as 822 'home routers' and 'home switches' are frequently confused. In 823 addition, there are cases where NAT routers are included within 824 Virtual Machine Hypervisors, or where Internet connection sharing 825 services have been enabled. This document applies equally to such 826 hidden NAT 'routers'. IPv6 routed versions of such cases will be 827 required. We should thus also note that routers in the homenet may 828 not be separate physical devices; they may be embedded within other 829 devices. 831 3.2.4. Multihoming 833 A homenet may be multihomed to multiple providers, as the network 834 models above illustrate. This may either take a form where there are 835 multiple isolated networks within the home or a more integrated 836 network where the connectivity selection needs to be dynamic. 837 Current practice is typically of the former kind, but the latter is 838 expected to become more commonplace. 840 In the general homenet architecture, multihomed hosts should be 841 multi-addressed with a global IPv6 address from the global prefix 842 delegated from each ISP they communicate with or through. When such 843 multi-addressing is in use, hosts need some way to pick source and 844 destination address pairs for connections. A host may choose a 845 source address to use by various methods, most commonly [RFC6724]. 846 Applications may of course do different things, and this should not 847 be precluded. 849 For the single CER Network Model C illustrated above, multihoming may 850 be offered by source-based routing at the CER. With multiple exit 851 routers, as in CER Network Model B, the complexity rises. Given a 852 packet with a source address on the home network, the packet must be 853 routed to the proper egress to avoid BCP 38 ingress filtering if 854 exiting through the wrong ISP. It is highly desirable that the 855 packet is routed in the most efficient manner to the correct exit, 856 though as a minimum requirement the packet should not be dropped. 858 The homenet architecture should support both the above models, i.e., 859 one or more CERs. However, the general multihoming problem is broad, 860 and solutions suggested to date within the IETF have included complex 861 architectures for monitoring connectivity, traffic engineering, 862 identifier-locator separation, connection survivability across 863 multihoming events, and so on. It is thus important that the homenet 864 architecture should as far as possible minimise the complexity of any 865 multihoming support. 867 An example of such a 'simpler' approach has been documented in 868 [I-D.ietf-v6ops-ipv6-multihoming-without-ipv6nat]. Alternatively a 869 flooding/routing protocol could potentially be used to pass 870 information through the homenet, such that internal routers and 871 ultimately end hosts could learn per-prefix configuration 872 information, allowing better address selection decisions to be made. 873 However, this would imply router and, most likely, host changes. 874 Another avenue is to introduce support throughout the homenet for 875 routing which is based on the source as well as the destination 876 address of each packet. While greatly improving the 'intelligence' 877 of routing decisions within the homenet, such an approach would 878 require relatively significant router changes but avoid host changes. 880 As explained previously, while NPTv6 has been proposed for providing 881 multi-homing support in networks, its use is not recommended in the 882 homenet architecture. 884 It should be noted that some multihoming scenarios may see one 885 upstream being a "walled garden", and thus only appropriate for 886 connectivity to the services of that provider; an example may be a 887 VPN service that only routes back to the enterprise business network 888 of a user in the homenet. As per Section 4.2.1 of [RFC3002] we do 889 not specifically target walled garden multihoming as a goal of this 890 document. 892 The homenet architecture should also not preclude use of host or 893 application-oriented tools, e.g., Shim6 [RFC5533], MPTCP [RFC6824] or 894 Happy Eyeballs [RFC6555]. In general, any incremental improvements 895 obtained by host changes should give benefit for the hosts 896 introducing them, but not be required. 898 3.2.5. Mobility support 900 Devices may be mobile within the homenet. While resident on the same 901 subnet, their address will remain persistent, but should devices move 902 to a different (wireless) subnet, they will acquire a new address in 903 that subnet. It is desirable that the homenet supports internal 904 device mobility. To do so, the homenet may either extend the reach 905 of specific wireless subnets to enable wireless roaming across the 906 home (availability of a specific subnet across the home), or it may 907 support mobility protocols to facilitate such roaming where multiple 908 subnets are used. 910 3.3. A Self-Organising Network 912 The home network infrastructure should be naturally self-organising 913 and self-configuring under different circumstances relating to the 914 connectivity status to the Internet, number of devices, and physical 915 topology. At the same time, it should be possible for advanced users 916 to manually adjust (override) the current configuration. 918 While a goal of the homenet architecture is for the network to be as 919 self-organising as possible, there may be instances where some manual 920 configuration is required, e.g., the entry of a cryptographic key to 921 apply wireless security, or to configure a shared routing secret. 922 The latter may be relevant when considering how to bootstrap a 923 routing configuration. It is highly desirable that the number of 924 such configurations is minimised. 926 3.3.1. Differentiating neighbouring homenets 928 It is important that self-configuration with 'unintended' devices is 929 avoided. There should be a way for a user to administratively assert 930 in a simple way whether or not a device belongs to a given homenet. 931 The goal is to allow the establishment of borders, particularly 932 between two adjacent homenets, and to avoid unauthorised devices from 933 participating in the homenet. Such an authorisation capability may 934 need to operate through multiple hops in the homenet. 936 The homenet should thus support a way for a homenet owner to claim 937 ownership of their devices in a reasonably secure way. This could be 938 achieved by a pairing mechanism, by for example pressing buttons 939 simultaneously on an authenticated and a new homenet device, or by an 940 enrolment process as part of an autonomic networking environment. 942 While there may be scenarios where one homenet may wish to 943 intentionally gain access through another, e.g. to share external 944 connectivity costs, such scenarios are not discussed in this 945 document. 947 3.3.2. Largest practical subnets 949 Today's IPv4 home networks generally have a single subnet, and early 950 dual-stack deployments have a single congruent IPv6 subnet, possibly 951 with some bridging functionality. More recently, some vendors have 952 started to introduce 'home' and 'guest' functions, which in IPv6 953 would be implemented as two subnets. 955 Future home networks are highly likely to have one or more internal 956 routers and thus need multiple subnets, for the reasons described 957 earlier. As part of the self-organisation of the network, the 958 homenet should subdivide itself into the largest practical subnets 959 that can be constructed within the constraints of link layer 960 mechanisms, bridging, physical connectivity, and policy, and where 961 applicable performance or other criteria. In such subdivisions the 962 logical topology may not necessarily match the physical topology. 964 This text does not, however, make recommendations on how such 965 subdivision should occur. It is expected that subsequent documents 966 will address this problem. 968 While it may be desirable to maximise the chance of link-local 969 protocols operating across a homenet by maximising the size of a 970 subnet, multi-subnet home networks are inevitable, so their support 971 must be included. 973 3.3.3. Handling varying link technologies 975 Homenets tend to grow organically over many years, and a homenet will 976 typically be built over link-layer technologies from different 977 generations. Current homenets typically use links ranging from 978 1Mbit/s up to 1Gbit/s, which is a three orders of magnitude 979 throughput discrepancy. We expect this discrepancy to widen further 980 as both high-speed and low-power technologies are deployed. 982 Homenet protocols should be designed to deal well with 983 interconnecting links of very different throughputs. In particular, 984 flows local to a link should not be flooded throughout the homenet, 985 even when sent over multicast, and, whenever possible, the homenet 986 protocols should be able to choose the faster links and avoid the 987 slower ones. 989 Links (particularly wireless links) may also have limited numbers of 990 transmit opportunities (txops), and there is a clear trend driven by 991 both power and downward compatibility constraints toward aggregation 992 of packets into these limited txops while increasing throughput. 993 Transmit opportunities may be a system's scarcest resource and 994 therefore also strongly limit actual throughput available. 996 3.3.4. Homenet realms and borders 998 The homenet will need to be aware of the extent of its own 'site', 999 which will, for example, define the borders for ULA and site scope 1000 multicast traffic, and may require specific security policies to be 1001 applied. The homenet will have one or more such borders with 1002 external connectivity providers. 1004 A homenet will most likely also have internal borders between 1005 internal realms, e.g., a guest realm or a corporate network extension 1006 realm. It is desirable that appropriate borders can be configured to 1007 determine, for example, the scope of where network prefixes, routing 1008 information, network traffic, service discovery and naming may be 1009 shared. The default mode internally should be to share everything. 1011 It is expected that a realm would span at least an entire subnet, and 1012 thus the borders lie at routers which receive delegated prefixes 1013 within the homenet. It is also desirable, for a richer security 1014 model, that hosts are able to make communication decisions based on 1015 available realm and associated prefix information in the same way 1016 that routers at realm borders can. 1018 A simple homenet model may just consider three types of realm and the 1019 borders between them, namely the internal homenet, the ISP and a 1020 guest network. In this case the borders will include that from the 1021 homenet to the ISP, that from the guest network to the ISP, and that 1022 from the homenet to the guest network. Regardless, it should be 1023 possible for additional types of realms and borders to be defined, 1024 e.g., for some specific LLN-based network, such as Smart Grid, and 1025 for these to be detected automatically, and for an appropriate 1026 default policy to be applied as to what type of traffic/data can flow 1027 across such borders. 1029 It is desirable to classify the external border of the home network 1030 as a unique logical interface separating the home network from 1031 service provider network/s. This border interface may be a single 1032 physical interface to a single service provider, multiple layer 2 1033 sub-interfaces to a single service provider, or multiple connections 1034 to a single or multiple providers. This border makes it possible to 1035 describe edge operations and interface requirements across multiple 1036 functional areas including security, routing, service discovery, and 1037 router discovery. 1039 It should be possible for the homenet user to override any 1040 automatically determined borders and the default policies applied 1041 between them, the exception being that it may not be possible to 1042 override policies defined by the ISP at the external border. 1044 3.3.5. Configuration information from the ISP 1046 In certain cases, it may be useful for the homenet to get certain 1047 configuration information from its ISP. For example, the homenet 1048 DHCP server may request and forward some options that it gets from 1049 its upstream DHCP server, though the specifics of the options may 1050 vary across deployments. There is potential complexity here of 1051 course should the homenet be multihomed. 1053 3.4. Homenet Addressing 1055 The IPv6 addressing scheme used within a homenet must conform to the 1056 IPv6 addressing architecture [RFC4291]. In this section we discuss 1057 how the homenet needs to adapt to the prefixes made available to it 1058 by its upstream ISP, such that internal subnets, hosts and devices 1059 can obtain the and configure the necessary addressing information to 1060 operate. 1062 3.4.1. Use of ISP-delegated IPv6 prefixes 1064 Discussion of IPv6 prefix allocation policies is included in 1065 [RFC6177]. In practice, a homenet may receive an arbitrary length 1066 IPv6 prefix from its provider, e.g., /60, /56 or /48. The offered 1067 prefix may be stable or change from time to time; it is generally 1068 expected that ISPs will offer relatively stable prefixes to their 1069 residential customers. Regardless, the home network needs to be 1070 adaptable as far as possible to ISP prefix allocation policies, and 1071 thus make no assumptions about the stability of the prefix received 1072 from an ISP, or the length of the prefix that may be offered. 1074 However, if, for example, only a /64 is offered by the ISP, the 1075 homenet may be severely constrained or even unable to function. 1076 [RFC6177] (BCP 157) states that "a key principle for address 1077 management is that end sites always be able to obtain a reasonable 1078 amount of address space for their actual and planned usage, and over 1079 time ranges specified in years rather than just months. In practice, 1080 that means at least one /64, and in most cases significantly more. 1081 One particular situation that must be avoided is having an end site 1082 feel compelled to use IPv6-to-IPv6 Network Address Translation or 1083 other burdensome address conservation techniques because it could not 1084 get sufficient address space." This architecture document assumes 1085 that the guidance in the quoted text is being followed by ISPs. 1087 There are many problems that would arise from a homenet not being 1088 offered a sufficient prefix size for its needs. Rather than attempt 1089 to contrive a method for a homenet to operate in a constrained manner 1090 when faced with insufficient prefixes, such as the use of subnet 1091 prefixes longer than /64 (which would break stateless address 1092 autoconfiguration [RFC4862]), use of NPTv6, or falling back to 1093 bridging across potentially very different media, it is recommended 1094 that the receiving router instead enters an error state and issues 1095 appropriate warnings. Some consideration may need to be given to how 1096 such a warning or error state should best be presented to a typical 1097 home user. 1099 Thus a homenet CER should request, for example via DHCP Prefix 1100 Delegation (DHCP PD) [RFC3633], that it would like a /48 prefix from 1101 its ISP, i.e., it asks the ISP for the maximum size prefix it might 1102 expect to be offered, even if in practice it may only be offered a 1103 /56 or /60. For a typical IPv6 homenet, it is not recommended that 1104 an ISP offer less than a /60 prefix, and it is highly preferable that 1105 the ISP offers at least a /56. It is expected that the allocated 1106 prefix to the homenet from any single ISP is a contiguous, aggregated 1107 one. While it may be possible for a homenet CER to issue multiple 1108 prefix requests to attempt to obtain multiple delegations, such 1109 behaviour is out of scope of this document. 1111 The norm for residential customers of large ISPs may be similar to 1112 their single IPv4 address provision; by default it is likely to 1113 remain persistent for some time, but changes in the ISP's own 1114 provisioning systems may lead to the customer's IP (and in the IPv6 1115 case their prefix pool) changing. It is not expected that ISPs will 1116 generally support Provider Independent (PI) addressing for 1117 residential homenets. 1119 When an ISP does need to restructure, and in doing so renumber its 1120 customer homenets, 'flash' renumbering is likely to be imposed. This 1121 implies a need for the homenet to be able to handle a sudden 1122 renumbering event which, unlike the process described in [RFC4192], 1123 would be a 'flag day" event, which means that a graceful renumbering 1124 process moving through a state with two active prefixes in use would 1125 not be possible. While renumbering can be viewed as an extended 1126 version of an initial numbering process, the difference between flash 1127 renumbering and an initial 'cold start' is the need to provide 1128 service continuity. 1130 There may be cases where local law means some ISPs are required to 1131 change IPv6 prefixes (current IPv4 addresses) for privacy reasons for 1132 their customers. In such cases it may be possible to avoid an 1133 instant 'flash' renumbering and plan a non-flag day renumbering as 1134 per RFC 4192. Similarly, if an ISP has a planned renumbering 1135 process, it may be able to adjust lease timers, etc appropriately. 1137 The customer may of course also choose to move to a new ISP, and thus 1138 begin using a new prefix. In such cases the customer should expect a 1139 discontinuity, and not only may the prefix change, but potentially 1140 also the prefix length if the new ISP offers a different default size 1141 prefix. The homenet may also be forced to renumber itself if 1142 significant internal 'replumbing' is undertaken by the user. 1143 Regardless, it's desirable that homenet protocols support rapid 1144 renumbering and that operational processes don't add unnecessary 1145 complexity for the renumbering process. Further, the introduction of 1146 any new homenet protocols should not make any form of renumbering any 1147 more complex than it already is. 1149 Finally, the internal operation of the home network should also not 1150 depend on the availability of the ISP network at any given time, 1151 other than of course for connectivity to services or systems off the 1152 home network. This reinforces the use of ULAs for stable internal 1153 communication, and the need for a naming and service discovery 1154 mechanism that can operate independently within the homenet. 1156 3.4.2. Stable internal IP addresses 1158 The network should by default attempt to provide IP-layer 1159 connectivity between all internal parts of the homenet as well as to 1160 and from the external Internet, subject to the filtering policies or 1161 other policy constraints discussed later in the security section. 1163 ULAs should be used within the scope of a homenet to support stable 1164 routing and connectivity between subnets and hosts regardless of 1165 whether a globally unique ISP-provided prefix is available. In the 1166 case of a prolonged external connectivity outage, ULAs allow internal 1167 operations across routed subnets to continue. ULA addresses also 1168 allow constrained devices to create permanent relationships between 1169 IPv6 addresses, e.g., from a wall controller to a lamp, where 1170 symbolic host names would require additional non-volatile memory and 1171 updating global prefixes in sleeping devices might also be 1172 problematic. 1174 As discussed previously, it would be expected that ULAs would 1175 normally be used alongside one or more global prefixes in a homenet, 1176 such that hosts become multi-addressed with both globally unique and 1177 ULA prefixes. ULAs should be used for all devices, not just those 1178 intended to only have internal connectivity. Default address 1179 selection would then enable ULAs to be preferred for internal 1180 communications between devices that are using ULA prefixes generated 1181 within the same homenet. 1183 In cases where ULA prefixes are in use within a homenet but there is 1184 no external IPv6 connectivity (and thus no GUAs in use), 1185 recommendations ULA-5, L-3 and L-4 in RFC 6204 should be followed to 1186 ensure correct operation, in particular where the homenet may be 1187 dual-stack with IPv4 external connectivity. The use of the Route 1188 Information Option described in [RFC4191] provides a mechanism to 1189 advertise such more-specific ULA routes. 1191 The use of ULAs should be restricted to the homenet scope through 1192 filtering at the border(s) of the homenet, as mandated by RFC 6204 1193 requirement S-2. 1195 Note that it is possible that in some cases multiple /48 ULA prefixes 1196 may be in use within the same homenet, e.g., when the network is 1197 being deployed, perhaps also without external connectivity. In cases 1198 where multiple ULA /48's are in use, hosts need to know that each /48 1199 is local to the homenet, e.g., by inclusion in their local address 1200 selection policy table. 1202 3.4.3. Internal prefix delegation 1204 As mentioned above, there are various sources of prefixes. From the 1205 homenet perspective, a single global prefix from each ISP should be 1206 received on the border CER [RFC3633]. Where multiple CERs exist with 1207 multiple ISP prefix pools, it is expected that routers within the 1208 homenet would assign themselves prefixes from each ISP they 1209 communicate with/through. As discussed above, a ULA prefix should be 1210 provisioned for stable internal communications or for use on 1211 constrained/LLN networks. 1213 The delegation or availability of a prefix pool to the homenet should 1214 allow subsequent internal autonomous delegation of prefixes for use 1215 within the homenet. Such internal delegation should not assume a 1216 flat or hierarchical model, nor should it make an assumption about 1217 whether the delegation of internal prefixes is distributed or 1218 centralised. The assignment mechanism should provide reasonable 1219 efficiency, so that typical home network prefix allocation sizes can 1220 accommodate all the necessary /64 allocations in most cases, and not 1221 waste prefixes. Further, duplicate assignment of multiple /64s to 1222 the same network should be avoided, and the network should behave as 1223 gracefully as possible in the event of prefix exhaustion (though the 1224 options in such cases may be limited). 1226 Where the home network has multiple CERs and these are delegated 1227 prefix pools from their attached ISPs, the internal prefix delegation 1228 would be expected to be served by each CER for each prefix associated 1229 with it. Where ULAs are used, it is preferable that only one /48 ULA 1230 covers the whole homenet, from which /64's can be delegated to the 1231 subnets. In cases where two /48 ULAs are generated within a homenet, 1232 the network should still continue to function, meaning that hosts 1233 will need to determine that each ULA is local to the homenet. 1235 Delegation within the homenet should result in each link being 1236 assigned a stable prefix that is persistent across reboots, power 1237 outages and similar short-term outages. The availability of 1238 persistent prefixes should not depend on the router boot order. The 1239 addition of a new routing device should not affect existing 1240 persistent prefixes, but persistence may not be expected in the face 1241 of significant 'replumbing' of the homenet. However, delegated ULA 1242 prefixes within the homenet should remain persistent through an ISP- 1243 driven renumbering event. 1245 Provisioning such persistent prefixes may imply the need for stable 1246 storage on routing devices, and also a method for a home user to 1247 'reset' the stored prefix should a significant reconfiguration be 1248 required (though ideally the home user should not be involved at 1249 all). 1251 This document makes no specific recommendation towards solutions, but 1252 notes that it is very likely that all routing devices participating 1253 in a homenet must use the same internal prefix delegation method. 1254 This implies that only one delegation method should be in use. 1256 3.4.4. Coordination of configuration information 1258 The network elements will need to be integrated in a way that takes 1259 account of the various lifetimes on timers that are used on different 1260 elements, e.g., DHCPv6 PD, router, valid prefix and preferred prefix 1261 timers. 1263 3.4.5. Privacy 1265 If ISPs offer relatively stable IPv6 prefixes to customers, the 1266 network prefix part of addresses associated with the homenet may not 1267 change over a reasonably long period of time. 1269 The exposure of which traffic is sourced from the same homenet is 1270 thus similar to IPv4; the single IPv4 global address seen through use 1271 of IPv4 NAT gives the same hint as the global IPv6 prefix seen for 1272 IPv6 traffic. 1274 While IPv4 NAT may obfuscate to an external observer which internal 1275 devices traffic is sourced from, IPv6, even with use of Privacy 1276 Addresses [RFC4941], adds additional exposure of which traffic is 1277 sourced from the same internal device, through use of the same IPv6 1278 source address for a period of time. 1280 3.5. Routing functionality 1282 Routing functionality is required when there are multiple routers 1283 deployed within the internal home network. This functionality could 1284 be as simple as the current 'default route is up' model of IPv4 NAT, 1285 or, more likely, it would involve running an appropriate routing 1286 protocol. Regardless of the solution method, the functionality 1287 discussed below should be met. 1289 The homenet unicast routing protocol should be based on a previously 1290 deployed protocol that has been shown to be reliable and robust, and 1291 that allows lightweight implementations, but that does not preclude 1292 the selection of a newer protocol for which a high quality open 1293 source implemenation becomes available. The availability of open 1294 source implementations is an important consideration. Using 1295 information distributed through the routing protocol, each node in 1296 the homenet should be able to build a graph of the topology of the 1297 whole homenet including links, nodes, connectivity, and (if the 1298 routing protocol supports them) link metrics. 1300 Multiple types of physical interfaces must be accounted for in the 1301 homenet routed topology. Technologies such as Ethernet, WiFi, 1302 Multimedia over Coax Alliance (MoCA), etc. must be capable of 1303 coexisting in the same environment and should be treated as part of 1304 any routed deployment. The inclusion of physical layer 1305 characteristics including bandwidth, loss, and latency in path 1306 computation should be considered for optimising communication in the 1307 homenet. 1309 The routing protocol should support the generic use of multiple 1310 customer Internet connections, and the concurrent use of multiple 1311 delegated prefixes. A routing protocol that can make routing 1312 decisions based on source and destination addresses is thus 1313 desirable, to avoid upstream ISP BCP 38 ingress filtering problems. 1314 Multihoming support should also include load-balancing to multiple 1315 providers, and failover from a primary to a backup link when 1316 available. The protocol however should not require upstream ISP 1317 connectivity to be established to continue routing within the 1318 homenet. 1320 The routing environment should be self-configuring, as discussed 1321 previously. Minimising convergence time should be a goal in any 1322 routed environment, but as a guideline a maximum convergence time at 1323 most 30 seconds should be the target (this target is somewhat 1324 arbitrary, and was chosen based on how long a typical home user might 1325 wait before attempting another reset; ideally the routers might have 1326 some status light indicating they are converging, similar to an ADSL 1327 router light indicating it is establishing a connection to its ISP). 1329 Homenets may use a variety of underlying link layer technologies, and 1330 may therefore benefit from being able to use link metrics if 1331 available. It may be beneficial for traffic to use multiple paths to 1332 a given destination within the homenet whwre available, rather than a 1333 single best path. 1335 Ideally, a single routing protocol solution is in use at a given time 1336 in a given homenet. If more than one routing protocol is defined for 1337 use in a homenet, then a mechanism is required to ensure that all 1338 routers in a given homenet support the same protocol before it is 1339 used, and that a particular routing solution is enabled by default. 1341 An appropriate mechanism is required to discover which router(s) in 1342 the homenet are providing the CER function. Borders may include but 1343 are not limited to the interface to the upstream ISP, a gateway 1344 device to a separate home network such as a LLN network, or a gateway 1345 to a guest or private corporate extension network. In some cases 1346 there may be no border present, which may for example occur before an 1347 upstream connection has been established. The border discovery 1348 functionality may be integrated into the routing protocol itself, but 1349 may also be imported via a separate discovery mechanism. 1351 Ideally, LLN or other logically separate networks should be able 1352 exchange routes such that IP traffic may be forwarded among the 1353 networks via gateway routers which interoperate with both the homenet 1354 and the LLN. Current home deployments use largely different 1355 mechanisms in sensor and basic Internet connectivity networks. IPv6 1356 virtual machine (VM) solutions may also add additional routing 1357 requirements. 1359 3.5.1. Multicast support 1361 It is desirable that, subject to the capacities of devices on certain 1362 media types, multicast routing is supported across the homenet. 1364 [RFC4291] requires that any boundary of scope 4 or higher (i.e., 1365 admin-local or higher) be administratively configured. Thus the 1366 boundary at the homenet-ISP border must be administratively 1367 configured, though that may be triggered by an administrative 1368 function such as DHCP-PD. Other multicast forwarding policy borders 1369 may also exist within the homenet, e.g., to/from a guest subnet, 1370 whilst the use of certain media types may also affect where specific 1371 multicast traffic is forwarded or routed. 1373 There may be different drivers for multicast to be supported across 1374 the homenet, e.g., for homenet-wide service discovery should a 1375 multicast service discovery protocol of scope greater than link-local 1376 be defined, or potentially for multicast-based streaming or 1377 filesharing applications. Where multicast is routed across a homenet 1378 an appropriate multicast routing protocol is required, one that as 1379 per the unicast routing protocol should be self-configuring. As 1380 hinted above, it must be possible to scope or filter multicast 1381 traffic to avoid it being flooded to network media where devices 1382 cannot reasonably support it. 1384 A homenet may not only use multicast internally, it may also be a 1385 consumer or provider of external multicast traffic, where the 1386 homenet's ISP supports such multicast operation. This may be 1387 valuable for example where live video applications are being sourced 1388 to/from the homenet. 1390 The multicast environment should support the ability for applications 1391 to pick a unique multicast group to use. 1393 3.6. Security 1395 The security of an IPv6 homenet is an important consideration. The 1396 most notable difference to the IPv4 operational model is the removal 1397 of NAT, the introduction of global addressability of devices, and 1398 thus a need to consider whether devices should have global 1399 reachability. Regardless, hosts need to be able to operate securely, 1400 end-to-end where required, and also be robust against malicious 1401 traffic directed towards them. However, there are other challenges 1402 introduced, e.g., default filtering policies at the borders between 1403 various homenet realms. 1405 3.6.1. Addressability vs reachability 1407 An IPv6-based home network architecture should embrace the 1408 transparent end-to-end communications model as described in 1409 [RFC2775]. Each device should be globally addressable, and those 1410 addresses must not be altered in transit. However, security 1411 perimeters can be applied to restrict end-to-end communications, and 1412 thus while a host may be globally addressable it may not be globally 1413 reachable. 1415 [RFC4864] describes a 'Simple Security' model for IPv6 networks, 1416 whereby stateful perimeter filtering can be applied to control the 1417 reachability of devices in a homenet. RFC 4864 states in Section 4.2 1418 that "the use of firewalls ... is recommended for those that want 1419 boundary protection in addition to host defences". It should be 1420 noted that a 'default deny' filtering approach would effectively 1421 replace the need for IPv4 NAT traversal protocols with a need to use 1422 a signalling protocol to request a firewall hole be opened, e.g., a 1423 protocol such as PCP [RFC6887]. In networks with multiple CERs, the 1424 signalling would need to handle the cases of flows that may use one 1425 or more exit routers. CERs would need to be able to advertise their 1426 existence for such protocols. 1428 [RFC6092] expands on RFC 4864, giving a more detailed discussion of 1429 IPv6 perimeter security recommendations, without mandating a 'default 1430 deny' approach. Indeed, RFC 6092 does not enforce a particular mode 1431 of operation, instead stating that CERs must provide an easily 1432 selected configuration option that permits a 'transparent' mode, thus 1433 ensuring a 'default allow' model is available. 1435 The topic of whether future home networks as described in this 1436 document should have have a 'default deny' or 'default allow' 1437 position has been discussed at length in various IETF meetings 1438 without any consensus being reached on which approach is more 1439 appropriate. Further, the choice of which default to apply may be 1440 situational, and thus this text makes no recommendation on the 1441 default setting beyond what is written on this topic in RFC 6092. We 1442 note in Section 3.6.3 below that the implicit firewall function of an 1443 IPv4 NAT is commonplace today, and thus future CERs targeted at home 1444 networks should continue to support the option of running in 'default 1445 deny mode', whether or not that is the default setting 1447 3.6.2. Filtering at borders 1449 It is desirable that there are mechanisms to detect different types 1450 of borders within the homenet, as discussed previously, and further 1451 mechanisms to then apply different types of filtering policies at 1452 those borders, e.g., whether naming and service discovery should pass 1453 a given border. Any such policies should be able to be easily 1454 applied by typical home users, e.g., to give a user in a guest 1455 network access to media services in the home, or access to a printer. 1456 Simple mechanisms to apply policy changes, or associations between 1457 devices, will be required. 1459 There are cases where full internal connectivity may not be 1460 desirable, e.g., in certain utility networking scenarios, or where 1461 filtering is required for policy reasons against guest network 1462 subnet(s). Some scenarios/models may as a result involve running 1463 isolated subnet(s) with their own CERs. In such cases connectivity 1464 would only be expected within each isolated network (though traffic 1465 may potentially pass between them via external providers). 1467 LLNs provide an another example of where there may be secure 1468 perimeters inside the homenet. Constrained LLN nodes may implement 1469 network key security but may depend on access policies enforced by 1470 the LLN border router. 1472 Considerations for differentiating neighbouring homenets are 1473 discussed in Section 3.3.1. 1475 3.6.3. Partial Effectiveness of NAT and Firewalls 1477 Security by way of obscurity (address translation) or through 1478 firewalls (filtering) is at best only partially effective. The very 1479 poor security track record of home computer, home networking and 1480 business PC computers and networking is testimony to this. A 1481 security compromise behind the firewall of any device exposes all 1482 others, making an entire network that relies on obscurity or a 1483 firewall as vulnerable as the most insecure device on the private 1484 side of the network. 1486 However, given current evidence of home network products with very 1487 poor default device security, putting a firewall in place does 1488 provide some level of protection. The use of firewalls today, 1489 whether a good practice or not, is common practice and the capability 1490 to afford protection via a 'default deny' setting, even if marginally 1491 effective, should not be lost. Thus, while it is highly desirable 1492 that all hosts in a homenet be adequately protected by built-in 1493 security functions, it should also be assumed that all CERs will 1494 continue to support appropriate perimeter defence functions, as per 1495 [RFC7084]. 1497 3.6.4. Exfiltration concerns 1499 As homenets become more complex, with more devices, and with service 1500 discovery potentially enabled across the whole home, there are 1501 potential concerns over the leakage of information should devices use 1502 discovery protocols to gather information and report it to equipment 1503 vendors or application service providers. 1505 While it is not clear how such exfiltration could be easily avoided, 1506 the threat should be recognised, be it from a new piece of hardware 1507 or some 'app' installed on a personal device. 1509 3.6.5. Device capabilities 1511 In terms of the devices, homenet hosts should implement their own 1512 security policies in accordance to their computing capabilities. 1513 They should have the means to request transparent communications to 1514 be able to be initiated to them through security filters in the 1515 homenet, either for all ports or for specific services. Users should 1516 have simple methods to associate devices to services that they wish 1517 to operate transparently through (CER) borders. 1519 3.6.6. ULAs as a hint of connection origin 1521 As noted in Section 3.6, if appropriate filtering is in place on the 1522 CER(s), as mandated by RFC 6204 requirement S-2, a ULA source address 1523 may be taken as an indication of locally sourced traffic. This 1524 indication could then be used with security settings to designate 1525 between which nodes a particular application is allowed to 1526 communicate, provided ULA address space is filtered appropriately at 1527 the boundary of the realm. 1529 3.7. Naming and Service Discovery 1531 The homenet requires devices to be able to determine and use unique 1532 names by which they can be accessed on the network, and which are not 1533 used by other devices on the network. Users and devices will need to 1534 be able to discover devices and services available on the network, 1535 e.g., media servers, printers, displays or specific home automation 1536 devices. Thus naming and service discovery must be supported in the 1537 homenet, and, given the nature of typical home network users, the 1538 service(s) providing this function must as far as possible support 1539 unmanaged operation. 1541 The naming system will be required to work internally or externally, 1542 be the user within the homenet or outside it, i.e., the user should 1543 be able to refer to devices by name, and potentially connect to them, 1544 wherever they may be. The most natural way to think about such 1545 naming and service discovery is to enable it to work across the 1546 entire homenet residence (site), disregarding technical borders such 1547 as subnets but respecting policy borders such as those between guest 1548 and other internal network realms. Remote access may be desired by 1549 the homenet residents while travelling, but also potentially by 1550 manufacturers or other 'benevolent' third parties. 1552 3.7.1. Discovering services 1554 Users will typically perform service discovery through graphical user 1555 interfaces (GUIs) that allow them to browse services on their network 1556 in an appropriate and intuitive way. Devices may also need to 1557 discover other devices, without any user intervention or choice. 1558 Either way, such interfaces are beyond the scope of this document, 1559 but the interface should have an appropriate application programming 1560 interface (API) for the discovery to be performed. 1562 Such interfaces may also typically hide the local domain name element 1563 from users, especially where only one name space is available. 1564 However, as we discuss below, in some cases the ability to discover 1565 available domains may be useful. 1567 We note that current zero-configuration service discovery protocols 1568 are generally aimed at single subnets. There is thus a choice to 1569 make for multi-subnet homenets as to whether such protocols should be 1570 proxied or extended to operate across a whole homenet. In this 1571 context, that may mean bridging a link-local method, taking care to 1572 avoid packets entering looping paths, or extending the scope of 1573 multicast traffic used for the purpose. It may mean that some proxy 1574 or hybrid service is utilised, perhaps co-resident on the CER. Or it 1575 may be that a new approach is preferable, e.g., flooding information 1576 around the homenet as attributes within the routing protocol (which 1577 could allow per-prefix configuration). However, we should prefer 1578 approaches that are backwardly compatible, and allow current 1579 implementations to continue to be used. Note that this document does 1580 not mandate a particular solution, rather it expresses the principles 1581 that should be used for a homenet naming and service discovery 1582 environment. 1584 One of the primary challenges facing service discovery today is lack 1585 of interoperability due to the ever increasing number of service 1586 discovery protocols available. While it is conceivable for consumer 1587 devices to support multiple discovery protocols, this is clearly not 1588 the most efficient use of network and computational resources. One 1589 goal of the homenet architecture should be a path to service 1590 discovery protocol interoperability either through a standards based 1591 translation scheme, hooks into current protocols to allow some for of 1592 communication among discovery protocols, extensions to support a 1593 central service repository in the homenet, or simply convergence 1594 towards a unified protocol suite. 1596 3.7.2. Assigning names to devices 1598 Given the large number of devices that may be networked in the 1599 future, devices should have a means to generate their own unique 1600 names within a homenet, and to detect clashes should they arise, 1601 e.g., where a second device of the same type/vendor as an existing 1602 device with the same default name is deployed, or where a new subnet 1603 is added to the homenet which already has a device of the same name. 1604 It is expected that a device should have a fixed name while within 1605 the scope of the homenet. 1607 Users will also want simple ways to (re)name devices, again most 1608 likely through an appropriate and intuitive interface that is beyond 1609 the scope of this document. Note the name a user assigns to a device 1610 may be a label that is stored on the device as an attribute of the 1611 device, and may be distinct from the name used in a name service, 1612 e.g., 'Study Laser Printer' as opposed to printer2.. 1614 3.7.3. The homenet name service 1616 The homenet name service should support both lookups and discovery. 1617 A lookup would operate via a direct query to a known service, while 1618 discovery may use multicast messages or a service where applications 1619 register in order to be found. 1621 It is highly desirable that the homenet name service must at the very 1622 least co-exist with the Internet name service. There should also be 1623 a bias towards proven, existing solutions. The strong implication is 1624 thus that the homenet service is DNS-based, or DNS-compatible. There 1625 are naming protocols that are designed to be configured and operate 1626 Internet-wide, like unicast-based DNS, but also protocols that are 1627 designed for zero-configuration local environments, like mDNS 1628 [RFC6762]. 1630 When DNS is used as the homenet name service, it typically includes 1631 both a resolving service and an authoritative service. The 1632 authoritative service hosts the homenet related zone. One approach 1633 when provisioning such a name service, which is designed to 1634 facilitate name resolution from the global Internet, is to run an 1635 authoritative name service on the CER and a secondary authoritative 1636 name service provided by the ISP or perhaps an external third party. 1638 Where zero configuration name services are used, it is desirable that 1639 these can also coexist with the Internet name service. In 1640 particular, where the homenet is using a global name space, it is 1641 desirable that devices have the ability, where desired, to add 1642 entries to that name space. There should also be a mechanism for 1643 such entries to be removed or expired from the global name space. 1645 To protect against attacks such as cache poisoning, where an attacker 1646 is able to insert a bogus DNS entry in the local cache, it is 1647 desirable to support appropriate name service security methods, 1648 including DNS Security Extensions (DNSSEC) [RFC4033], on both the 1649 authoritative server and the resolver sides. Where DNS is used, the 1650 homenet router or naming service must not prevent DNSSEC from 1651 operating. 1653 While this document does not specify hardware requirements, it is 1654 worth noting briefly here that e.g., in support of DNSSEC, 1655 appropriate homenet devices should have good random number generation 1656 capability, and future homenet specifications should indicate where 1657 high quality random number generators, i.e., with decent entropy, are 1658 needed. 1660 Finally, the impact of a change in CER must be considered. It would 1661 be desirable to retain any relevant state (configuration) that was 1662 held in the old CER. This might imply that state information should 1663 be distributed in the homenet, to be recoverable by/to the new CER, 1664 or to the homenet's ISP or a third party externally provided service 1665 by some means. 1667 3.7.4. Name spaces 1669 If access to homenet devices is required remotely from anywhere on 1670 the Internet, then at least one globally unique name space is 1671 required, though the use of multiple name spaces should not be 1672 precluded. One approach is that the name space(s) used for the 1673 homenet would be served authoritatively by the homenet, most likely 1674 by a server resident on the CER. Such name spaces may be acquired by 1675 the user or provided/generated by their ISP or an alternative 1676 externally provided service. It is likely that the default case is 1677 that a homenet will use a global domain provided by the ISP, but 1678 advanced users wishing to use a name space that is independent of 1679 their provider in the longer term should be able to acquire and use 1680 their own domain name. For users wanting to use their own 1681 independent domain names, such services are already available. 1683 Devices may also be assigned different names in different name 1684 spaces, e.g., by third parties who may manage systems or devices in 1685 the homenet on behalf of the resident(s). Remote management of the 1686 homenet is out of scope of this document. 1688 If however a global name space is not available, the homenet will 1689 need to pick and use a local name space which would only have meaning 1690 within the local homenet (i.e., it would not be used for remote 1691 access to the homenet). The .local name space currently has a 1692 special meaning for certain existing protocols which have link-local 1693 scope, and is thus not appropriate for multi-subnet home networks. A 1694 different name space is thus required for the homenet. 1696 One approach for picking a local name space is to use an Ambiguous 1697 Local Qualified Domain Name (ALQDN) space, such as .sitelocal (or an 1698 appropriate name reserved for the purpose). While this is a simple 1699 approach, there is the potential in principle for devices that are 1700 bookmarked somehow by name by an application in one homenet to be 1701 confused with a device with the same name in another homenet. In 1702 practice however the underlying service discovery protocols should be 1703 capable of handling moving to a network where a new device is using 1704 the same name as a device used previously in another homenet. 1706 An alternative approach for a local name space would be to use a 1707 Unique Locally Qualified Domain Name (ULQDN) space such as 1708 ..sitelocal. The could be generated in 1709 a variety of ways, one potentially being based on the local /48 ULA 1710 prefix being used across the homenet. Such a should 1711 survive a cold restart, i.e., be consistent after a network power- 1712 down, or, if a value is not set on startup, the CER or device running 1713 the name service should generate a default value. It would be 1714 desirable for the homenet user to be able to override the 1715 with a value of their choice, but that would increase 1716 the likelihood of a name conflict. Any generated 1717 should not be predictable; thus adding a salt/hash function would be 1718 desirable. 1720 In the (likely) event that the homenet is accessible from outside the 1721 homenet (using the global name space), it is vital that the homenet 1722 name space follow the rules and conventions of the global name space. 1723 In this mode of operation, names in the homenet (including those 1724 automatically generated by devices) must be usable as labels in the 1725 global name space. [RFC5890] describes considerations for 1726 Internationalizing Domain Names in Applications (IDNA). 1728 Also, with the introduction of new 'dotless' top level domains, there 1729 is also potential for ambiguity between, for example, a local host 1730 called 'computer' and (if it is registered) a .computer gTLD. Thus 1731 qualified names should always be used, whether these are exposed to 1732 the user or not. The IAB has issued a statement which explains why 1733 dotless domains should be considered harmful [IABdotless]. 1735 There may be use cases where either different name spaces may be 1736 desired for different realms in the homenet, or for segmentation of a 1737 single name space within the homenet. Thus hierarchical name space 1738 management is likely to be required. There should also be nothing to 1739 prevent individual device(s) being independently registered in 1740 external name spaces. 1742 It may be the case that if there are two or more CERs serving the 1743 home network, that if each has name space delegated from a different 1744 ISP there is the potential for devices in the home to have multiple 1745 fully qualified names under multiple domains. 1747 Where a user is in a remote network wishing to access devices in 1748 their home network, there may be a requirement to consider the domain 1749 search order presented where multiple associated name spaces exist. 1750 This also implies that a domain discovery function is desirable. 1752 It may be the case that not all devices in the homenet are made 1753 available by name via an Internet name space, and that a 'split view' 1754 (as described in [RFC6950] Section 4) is preferred for certain 1755 devices, whereby devices inside the homenet see different DNS 1756 responses to those outside. 1758 Finally, this document makes no assumption about the presence or 1759 omission of a reverse lookup service. There is an argument that it 1760 may be useful for presenting logging information to users with 1761 meaningful device names rather than literal addresses. There are 1762 also some services, most notably email mail exchangers, where some 1763 operators have chosen to require a valid reverse lookup before 1764 accepting connections. 1766 3.7.5. Independent operation 1768 Name resolution and service discovery for reachable devices must 1769 continue to function if the local network is disconnected from the 1770 global Internet, e.g., a local media server should still be available 1771 even if the Internet link is down for an extended period. This 1772 implies the local network should also be able to perform a complete 1773 restart in the absence of external connectivity, and have local 1774 naming and service discovery operate correctly. 1776 The approach described above of a local authoritative name service 1777 with a cache would allow local operation for sustained ISP outages. 1779 Having an independent local trust anchor is desirable, to support 1780 secure exchanges should external connectivity be unavailable. 1782 A change in ISP should not affect local naming and service discovery. 1783 However, if the homenet uses a global name space provided by the ISP, 1784 then this will obviously have an impact if the user changes their 1785 network provider. 1787 3.7.6. Considerations for LLNs 1789 In some parts of the homenet, in particular LLNs or any devices where 1790 battery power is used, devices may be sleeping, in which case a proxy 1791 for such nodes may be required, that could respond (for example) to 1792 multicast service discovery requests. Those same devices or parts of 1793 the network may have less capacity for multicast traffic that may be 1794 flooded from other parts of the network. In general, message 1795 utilisation should be efficient considering the network technologies 1796 and constrained devices that the service may need to operate over. 1798 There are efforts underway to determine naming and discovery 1799 solutions for use by the Constrained Application Protocol (CoAP) 1800 [I-D.ietf-core-coap] in LLN networks. These are outside the scope of 1801 this document. 1803 3.7.7. DNS resolver discovery 1805 Automatic discovery of a name service to allow client devices in the 1806 homenet to resolve external domains on the Internet is required, and 1807 such discovery must support clients that may be a number of router 1808 hops away from the name service. Similarly it may be desirable to 1809 convey any DNS domain search list that may be in effect for the 1810 homenet. 1812 3.7.8. Devices roaming to/from the homenet 1814 It is likely that some devices which have registered names within the 1815 homenet Internet name space and that are mobile will attach to the 1816 Internet at other locations and acquire an IP address at those 1817 locations. Devices may move between different homenets. In such 1818 cases it is desirable that devices may be accessed by the same name 1819 as is used in their home network. 1821 Solutions to this problem are not discussed in this document. They 1822 may include use of Mobile IPv6 or Dynamic DNS, either of which would 1823 put additional requirements on to the homenet, or establishment of a 1824 (VPN) tunnel to a server in the home network. 1826 3.8. Other Considerations 1828 This section discusses two other considerations for home networking 1829 that the architecture should not preclude, but that this text is 1830 neutral towards. 1832 3.8.1. Quality of Service 1834 Support for Quality of Service in a multi-service homenet may be a 1835 requirement, e.g., for a critical system (perhaps healthcare 1836 related), or for differentiation between different types of traffic 1837 (file sharing, cloud storage, live streaming, VoIP, etc). Different 1838 media types may have different such properties or capabilities. 1840 However, homenet scenarios should require no new Quality of Service 1841 protocols. A DiffServ [RFC2475] approach with a small number of 1842 predefined traffic classes may generally be sufficient, though at 1843 present there is little experience of Quality of Service deployment 1844 in home networks. It is likely that QoS, or traffic prioritisation, 1845 methods will be required at the CER, and potentially around 1846 boundaries between different media types (where for example some 1847 traffic may simply not be appropriate for some media, and need to be 1848 dropped to avoid overloading the constrained media). 1850 There may also be complementary mechanisms that could be beneficial 1851 to application performance and behaviour in the homenet domain, such 1852 as ensuring proper buffering algorithms are used as described in 1853 [Gettys11]. 1855 3.8.2. Operations and Management 1857 In this section we briefly review some initial considerations for 1858 operations and management in the type of homenet described in this 1859 document. It is expected that a separate document will define an 1860 appropriate operations and management framework for such homenets. 1862 As described in this document, the homenet should have the general 1863 goal of being self-organising and configuring from the network layer 1864 perspective, e.g. prefixes should be able to be assigned to router 1865 interfaces. Further, applications running on devices should be able 1866 to use zero configuration service discovery protocols to discover 1867 services of interest to the home user. In contrast, a home user 1868 would not be expected, for example, to have to assign prefixes to 1869 links, or manage the DNS entries for the home network. Such expert 1870 operation should not be precluded, but it is not the norm. 1872 The user may still be required to, or wish to, perform some 1873 configuration of the network and the devices on it. Examples might 1874 include entering a security key to enable access to their wireless 1875 network, or choosing to give a 'friendly name' to a device presented 1876 to them through service discovery. Configuration of link layer and 1877 application layer services is out of scope of this architectural 1878 principles document, but are likely to be required in an operational 1879 homenet. 1881 While not being expected to actively configure the networking 1882 elements of their homenet, users may be interested in being able to 1883 view the status of their networks and the devices connected to it, in 1884 which case appropriate network monitoring protocols will be required 1885 to allow them to view their network, and its status, e.g. via a web 1886 interface or equivalent. While the user may not understand how the 1887 network operates, it is reasonable to assume they are interested in 1888 understanding what faults or problems may exist on it. Such 1889 monitoring may extend to other devices on the network, e.g. storage 1890 devices, or web cameras, but such devices are beyond the scope of 1891 this document. 1893 It may also be the case that an ISP, or a third party, might wish to 1894 offer a remote management service for the homenet on behalf of the 1895 user, or to be able to assist the user in event of some problem they 1896 are experiencing, in which case appropriate management and monitoring 1897 protocols would be required. 1899 The specific protocols required to facilitate homenet management and 1900 monitoring are out of scope of this document. As stated above, it is 1901 expected that a separate document will be produced to describe the 1902 operations and management framework for the types of home network 1903 presented in this document. 1905 As a final point, we note that it is desirable that all network 1906 management and monitoring functions should be available over IPv6 1907 transport, even where the homenet is dual-stack. 1909 3.9. Implementing the Architecture on IPv6 1911 This architecture text encourages re-use of existing protocols. Thus 1912 the necessary mechanisms are largely already part of the IPv6 1913 protocol set and common implementations, though there are some 1914 exceptions. 1916 For automatic routing, it is expected that solutions can be found 1917 based on existing protocols. Some relatively smaller updates are 1918 likely to be required, e.g., a new mechanism may be needed in order 1919 to turn a selected protocol on by default, a mechanism may be 1920 required to automatically assign prefixes to links within the 1921 homenet. 1923 Some functionality, if required by the architecture, may need more 1924 significant changes or require development of new protocols, e.g., 1925 support for multihoming with multiple exit routers would likely 1926 require extensions to support source and destination address based 1927 routing within the homenet. 1929 Some protocol changes are however required in the architecture, e.g., 1930 for name resolution and service discovery, extensions to existing 1931 zero configuration link-local name resolution protocols are needed to 1932 enable them to work across subnets, within the scope of the home 1933 network site. 1935 Some of the hardest problems in developing solutions for home 1936 networking IPv6 architectures include discovering the right borders 1937 where the 'home' domain ends and the service provider domain begins, 1938 deciding whether some of the necessary discovery mechanism extensions 1939 should affect only the network infrastructure or also hosts, and the 1940 ability to turn on routing, prefix delegation and other functions in 1941 a backwards compatible manner. 1943 4. Conclusions 1945 This text defines principles and requirements for a homenet 1946 architecture. The principles and requirements documented here should 1947 be observed by any future texts describing homenet protocols for 1948 routing, prefix management, security, naming or service discovery. 1950 5. Security Considerations 1952 Security considerations for the homenet architecture are discussed in 1953 Section 3.6 above. 1955 6. IANA Considerations 1957 This document has no actions for IANA. 1959 7. References 1961 7.1. Normative References 1963 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1964 (IPv6) Specification", RFC 2460, December 1998. 1966 [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic 1967 Host Configuration Protocol (DHCP) version 6", RFC 3633, 1968 December 2003. 1970 [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast 1971 Addresses", RFC 4193, October 2005. 1973 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 1974 Architecture", RFC 4291, February 2006. 1976 7.2. Informative References 1978 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 1979 E. Lear, "Address Allocation for Private Internets", 1980 BCP 5, RFC 1918, February 1996. 1982 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., 1983 and W. Weiss, "An Architecture for Differentiated 1984 Services", RFC 2475, December 1998. 1986 [RFC2775] Carpenter, B., "Internet Transparency", RFC 2775, 1987 February 2000. 1989 [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: 1990 Defeating Denial of Service Attacks which employ IP Source 1991 Address Spoofing", BCP 38, RFC 2827, May 2000. 1993 [RFC3002] Mitzel, D., "Overview of 2000 IAB Wireless Internetworking 1994 Workshop", RFC 3002, December 2000. 1996 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 1997 Address Translator (Traditional NAT)", RFC 3022, 1998 January 2001. 2000 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 2001 Rose, "DNS Security Introduction and Requirements", 2002 RFC 4033, March 2005. 2004 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 2005 More-Specific Routes", RFC 4191, November 2005. 2007 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 2008 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 2009 September 2005. 2011 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless 2012 Address Autoconfiguration", RFC 4862, September 2007. 2014 [RFC4864] Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and 2015 E. Klein, "Local Network Protection for IPv6", RFC 4864, 2016 May 2007. 2018 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 2019 Extensions for Stateless Address Autoconfiguration in 2020 IPv6", RFC 4941, September 2007. 2022 [RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming 2023 Shim Protocol for IPv6", RFC 5533, June 2009. 2025 [RFC5890] Klensin, J., "Internationalized Domain Names for 2026 Applications (IDNA): Definitions and Document Framework", 2027 RFC 5890, August 2010. 2029 [RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4 2030 Infrastructures (6rd) -- Protocol Specification", 2031 RFC 5969, August 2010. 2033 [RFC6092] Woodyatt, J., "Recommended Simple Security Capabilities in 2034 Customer Premises Equipment (CPE) for Providing 2035 Residential IPv6 Internet Service", RFC 6092, 2036 January 2011. 2038 [RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for 2039 IPv4/IPv6 Translation", RFC 6144, April 2011. 2041 [RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation 2042 Algorithm", RFC 6145, April 2011. 2044 [RFC6177] Narten, T., Huston, G., and L. Roberts, "IPv6 Address 2045 Assignment to End Sites", BCP 157, RFC 6177, March 2011. 2047 [RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B., and O. 2048 Troan, "Basic Requirements for IPv6 Customer Edge 2049 Routers", RFC 6204, April 2011. 2051 [RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix 2052 Translation", RFC 6296, June 2011. 2054 [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- 2055 Stack Lite Broadband Deployments Following IPv4 2056 Exhaustion", RFC 6333, August 2011. 2058 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 2059 Dual-Stack Hosts", RFC 6555, April 2012. 2061 [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, 2062 "Default Address Selection for Internet Protocol Version 6 2063 (IPv6)", RFC 6724, September 2012. 2065 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 2066 February 2013. 2068 [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, 2069 "TCP Extensions for Multipath Operation with Multiple 2070 Addresses", RFC 6824, January 2013. 2072 [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. 2073 Selkirk, "Port Control Protocol (PCP)", RFC 6887, 2074 April 2013. 2076 [RFC6950] Peterson, J., Kolkman, O., Tschofenig, H., and B. Aboba, 2077 "Architectural Considerations on Application Features in 2078 the DNS", RFC 6950, October 2013. 2080 [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic 2081 Requirements for IPv6 Customer Edge Routers", RFC 7084, 2082 November 2013. 2084 [I-D.ietf-v6ops-ipv6-multihoming-without-ipv6nat] 2085 Troan, O., Miles, D., Matsushima, S., Okimoto, T., and D. 2086 Wing, "IPv6 Multihoming without Network Address 2087 Translation", 2088 draft-ietf-v6ops-ipv6-multihoming-without-ipv6nat-06 (work 2089 in progress), February 2014. 2091 [I-D.ietf-core-coap] 2092 Shelby, Z., Hartke, K., and C. Bormann, "Constrained 2093 Application Protocol (CoAP)", draft-ietf-core-coap-18 2094 (work in progress), June 2013. 2096 [IABdotless] 2097 "IAB Statement: Dotless Domains Considered Harmful", 2098 February 2013, . 2102 [Gettys11] 2103 Gettys, J., "Bufferbloat: Dark Buffers in the Internet", 2104 March 2011, 2105 . 2107 Appendix A. Acknowledgments 2109 The authors would like to thank Aamer Akhter, Mikael Abrahamsson, 2110 Mark Andrews, Dmitry Anipko, Ran Atkinson, Fred Baker, Ray Bellis, 2111 Teco Boot, John Brzozowski, Cameron Byrne, Brian Carpenter, Stuart 2112 Cheshire, Julius Chroboczek, Lorenzo Colitti, Robert Cragie, Elwyn 2113 Davies, Ralph Droms, Lars Eggert, Jim Gettys, Olafur Gudmundsson, 2114 Wassim Haddad, Joel M. Halpern, David Harrington, Lee Howard, Ray 2115 Hunter, Joel Jaeggli, Heather Kirksey, Ted Lemon, Acee Lindem, Kerry 2116 Lynn, Daniel Migault, Erik Nordmark, Michael Richardson, Mattia 2117 Rossi, Barbara Stark, Markus Stenberg, Sander Steffann, Don Sturek, 2118 Andrew Sullivan, Dave Taht, Dave Thaler, Michael Thomas, Mark 2119 Townsley, JP Vasseur, Curtis Villamizar, Dan Wing, Russ White, and 2120 James Woodyatt for their comments and contributions within homenet WG 2121 meetings and on the WG mailing list. An acknowledgement generally 2122 means that person's text made it in to the document, or was helpful 2123 in clarifying or reinforcing an aspect of the document. It does not 2124 imply that each controbutor agrees with every point in the document. 2126 Appendix B. Changes 2128 This section will be removed in the final version of the text. 2130 B.1. Version 13 2132 Changes made include: 2134 o Changes to address last outstanding IESG DISCUSSes/COMMENTs. 2136 B.2. Version 12 2138 Changes made include: 2140 o Fixed minor typo nits introduced in -11. 2142 o Elwyn Davies' gen-art review comments addressed. 2144 o Some further IESG DISCUSSes/COMMENTs addressed. 2146 B.3. Version 11 (after IESG review) 2148 Changes made include: 2150 o Jouni Korhonen's OPSDIR review comments addressed. 2152 o Elwyn Davies' gen-art review comments addressed. 2154 o Considered secdir review by Samiel Weiler; many points addressed. 2156 o Considered APPSDIR review. 2158 o Addressed a large number of IESG comments and discusses. 2160 B.4. Version 10 (after AD review) 2162 Changes made include: 2164 o Minor changes/clarifications resulting from AD review 2166 B.5. Version 09 (after WGLC) 2168 Changes made include: 2170 o Added note about multicast into or out of site 2172 o Removed further personal draft references, replaced with covering 2173 text 2175 o Routing functionality text updated to avoid ambiguity 2177 o Added note that devices away from homenet may tunnel home (via 2178 VPN) 2180 o Added note that homenets more exposed to provider renumbering than 2181 with IPv4 and NAT 2183 o Added note about devices that may be ULA-only until configured to 2184 be globally addressable 2186 o Removed paragraph about broken CERs that do not work with prefixes 2187 other than /64 2189 o Noted no recommendation on methods to convey prefix information is 2190 made in this text 2192 o Stated that this text does not recommend how to form largest 2193 possible subnets 2195 o Added text about homenet evolution and handling disparate media 2196 types 2198 o Rephrased NAT/firewall text on marginal effectiveness 2200 o Emphasised that multihoming may be to any number of ISPs 2202 B.6. Version 08 2204 Changes made include: 2206 o Various clarifications made in response to list comments 2208 o Added note on ULAs with IPv4, where no GUAs in use 2210 o Added note on naming and internationalisation (IDNA) 2212 o Added note on trust relationships when adding devices 2214 o Added note for MPTCP 2216 o Added various naming and SD notes 2218 o Added various notes on delegated ISP prefixes 2220 B.7. Version 07 2222 Changes made include: 2224 o Removed reference to NPTv6 in section 3.2.4. Instead now say it 2225 has an architectural cost to use in the earlier section, and thus 2226 it is not recommended for use in the homenet architecture. 2228 o Removed 'proxy or extend?' section. Included shorter text in main 2229 body, without mandating either approach for service discovery. 2231 o Made it clearer that ULAs are expected to be used alongside 2232 globals. 2234 o Removed reference to 'advanced security' as described in 2235 draft-vyncke-advanced-ipv6-security. 2237 o Balanced the text between ULQDN and ALQDN. 2239 o Clarify text does not assume default deny or allow on CER, but 2240 that either mode may be enabled. 2242 o Removed ULA-C reference for 'simple' addresses. Instead only 2243 suggested service discovery to find such devices. 2245 o Reiterated that single/multiple CER models to be supported for 2246 multihoming. 2248 o Reordered section 3.3 to improve flow. 2250 o Added recommendation that homenet is not allocated less than /60, 2251 and a /56 is preferable. 2253 o Tidied up first few intro sections. 2255 o Other minor edits from list feedback. 2257 B.8. Version 06 2259 Changes made include: 2261 o Stated that unmanaged goal is 'as far as possible'. 2263 o Added note about multiple /48 ULAs potentially being in use. 2265 o Minor edits from list feedback. 2267 B.9. Version 05 2269 Changes made include: 2271 o Some significant changes to naming and SD section. 2273 o Removed some expired drafts. 2275 o Added notes about issues caused by ISP only delegating a /64. 2277 o Recommended against using prefixes longer than /64. 2279 o Suggested CER asks for /48 by DHCP PD, even if it only receives 2280 less. 2282 o Added note about DS-Lite but emphasised transition is out of 2283 scope. 2285 o Added text about multicast routing. 2287 B.10. Version 04 2289 Changes made include: 2291 o Moved border section from IPv6 differences to principles section. 2293 o Restructured principles into areas. 2295 o Added summary of naming and service discovery discussion from WG 2296 list. 2298 B.11. Version 03 2300 Changes made include: 2302 o Various improvements to the readability. 2304 o Removed bullet lists of requirements, as requested by chair. 2306 o Noted 6204bis has replaced advanced-cpe draft. 2308 o Clarified the topology examples are just that. 2310 o Emphasised we are not targetting walled gardens, but they should 2311 not be precluded. 2313 o Also changed text about requiring support for walled gardens. 2315 o Noted that avoiding falling foul of ingress filtering when 2316 multihomed is desirable. 2318 o Improved text about realms, detecting borders and policies at 2319 borders. 2321 o Stated this text makes no recommendation about default security 2322 model. 2324 o Added some text about failure modes for users plugging things 2325 arbitrarily. 2327 o Expanded naming and service discovery text. 2329 o Added more text about ULAs. 2331 o Removed reference to version 1 on chair feedback. 2333 o Stated that NPTv6 adds architectural cost but is not a homenet 2334 matter if deployed at the CER. This text only considers the 2335 internal homenet. 2337 o Noted multihoming is supported. 2339 o Noted routers may not by separate devices, they may be embedded in 2340 devices. 2342 o Clarified simple and advanced security some more, and RFC 4864 and 2343 6092. 2345 o Stated that there should be just one secret key, if any are used 2346 at all. 2348 o For multihoming, support multiple CERs but note that routing to 2349 the correct CER to avoid ISP filtering may not be optimal within 2350 the homenet. 2352 o Added some ISPs renumber due to privacy laws. 2354 o Removed extra repeated references to Simple Security. 2356 o Removed some solution creep on RIOs/RAs. 2358 o Load-balancing scenario added as to be supported. 2360 B.12. Version 02 2362 Changes made include: 2364 o Made the IPv6 implications section briefer. 2366 o Changed Network Models section to describe properties of the 2367 homenet with illustrative examples, rather than implying the 2368 number of models was fixed to the six shown in 01. 2370 o Text to state multihoming support focused on single CER model. 2371 Multiple CER support is desirable, but not required. 2373 o Stated that NPTv6 not supported. 2375 o Added considerations section for operations and management. 2377 o Added bullet point principles/requirements to Section 3.4. 2379 o Changed IPv6 solutions must not adversely affect IPv4 to should 2380 not. 2382 o End-to-end section expanded to talk about "Simple Security" and 2383 borders. 2385 o Extended text on naming and service discovery. 2387 o Added reference to RFC 2775, RFC 6177. 2389 o Added reference to the new xmDNS draft. 2391 o Added naming/SD requirements from Ralph Droms. 2393 Authors' Addresses 2395 Tim Chown (editor) 2396 University of Southampton 2397 Highfield 2398 Southampton, Hampshire SO17 1BJ 2399 United Kingdom 2401 Email: tjc@ecs.soton.ac.uk 2403 Jari Arkko 2404 Ericsson 2405 Jorvas 02420 2406 Finland 2408 Email: jari.arkko@piuha.net 2410 Anders Brandt 2411 Sigma Designs 2412 Emdrupvej 26A, 1 2413 Copenhagen DK-2100 2414 Denmark 2416 Email: abr@sdesigns.dk 2418 Ole Troan 2419 Cisco Systems, Inc. 2420 Drammensveien 145A 2421 Oslo N-0212 2422 Norway 2424 Email: ot@cisco.com 2426 Jason Weil 2427 Time Warner Cable 2428 13820 Sunrise Valley Drive 2429 Herndon, VA 20171 2430 USA 2432 Email: jason.weil@twcable.com