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diff --git a/doc/rfc/rfc7368.txt b/doc/rfc/rfc7368.txt new file mode 100644 index 0000000..74210c9 --- /dev/null +++ b/doc/rfc/rfc7368.txt @@ -0,0 +1,2747 @@ + + + + + + +Internet Engineering Task Force (IETF) T. Chown, Ed. +Request for Comments: 7368 University of Southampton +Category: Informational J. Arkko +ISSN: 2070-1721 Ericsson + A. Brandt + Sigma Designs + O. Troan + Cisco Systems, Inc. + J. Weil + Time Warner Cable + October 2014 + + + IPv6 Home Networking Architecture Principles + +Abstract + + This text describes evolving networking technology within residential + home networks with increasing numbers of devices and a trend towards + increased internal routing. The goal of this document is to define a + general architecture for IPv6-based home networking, describing the + associated principles, considerations, and requirements. The text + briefly highlights specific implications of the introduction of IPv6 + for home networking, discusses the elements of the architecture, and + suggests how standard IPv6 mechanisms and addressing can be employed + in home networking. The architecture describes the need for specific + protocol extensions for certain additional functionality. It is + assumed that the IPv6 home network is not actively managed and runs + as an IPv6-only or dual-stack network. There are no recommendations + in this text for the IPv4 part of the network. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Not all documents + approved by the IESG are a candidate for any level of Internet + Standard; see Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc7368. + + + + + +Chown, et al. Informational [Page 1] + +RFC 7368 IPv6 Home Networking October 2014 + + +Copyright Notice + + Copyright (c) 2014 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (http://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 + 1.1. Terminology and Abbreviations . . . . . . . . . . . . . . 5 + 2. Effects of IPv6 on Home Networking . . . . . . . . . . . . . 6 + 2.1. Multiple Subnets and Routers . . . . . . . . . . . . . . 7 + 2.2. Global Addressability and Elimination of NAT . . . . . . 8 + 2.3. Multi-Addressing of Devices . . . . . . . . . . . . . . . 8 + 2.4. Unique Local Addresses (ULAs) . . . . . . . . . . . . . . 9 + 2.5. Avoiding Manual Configuration of IP Addresses . . . . . . 10 + 2.6. IPv6-Only Operation . . . . . . . . . . . . . . . . . . . 11 + 3. Homenet Architecture Principles . . . . . . . . . . . . . . . 11 + 3.1. General Principles . . . . . . . . . . . . . . . . . . . 12 + 3.1.1. Reuse Existing Protocols . . . . . . . . . . . . . . 12 + 3.1.2. Minimise Changes to Hosts and Routers . . . . . . . . 13 + 3.2. Homenet Topology . . . . . . . . . . . . . . . . . . . . 13 + 3.2.1. Supporting Arbitrary Topologies . . . . . . . . . . . 13 + 3.2.2. Network Topology Models . . . . . . . . . . . . . . . 14 + 3.2.3. Dual-Stack Topologies . . . . . . . . . . . . . . . . 18 + 3.2.4. Multihoming . . . . . . . . . . . . . . . . . . . . . 19 + 3.2.5. Mobility Support . . . . . . . . . . . . . . . . . . 20 + 3.3. A Self-Organising Network . . . . . . . . . . . . . . . . 21 + 3.3.1. Differentiating Neighbouring Homenets . . . . . . . . 21 + 3.3.2. Largest Practical Subnets . . . . . . . . . . . . . . 21 + 3.3.3. Handling Varying Link Technologies . . . . . . . . . 22 + 3.3.4. Homenet Realms and Borders . . . . . . . . . . . . . 22 + 3.3.5. Configuration Information from the ISP . . . . . . . 23 + 3.4. Homenet Addressing . . . . . . . . . . . . . . . . . . . 24 + 3.4.1. Use of ISP-Delegated IPv6 Prefixes . . . . . . . . . 24 + 3.4.2. Stable Internal IP Addresses . . . . . . . . . . . . 26 + 3.4.3. Internal Prefix Delegation . . . . . . . . . . . . . 27 + 3.4.4. Coordination of Configuration Information . . . . . . 28 + 3.4.5. Privacy . . . . . . . . . . . . . . . . . . . . . . . 28 + + + +Chown, et al. Informational [Page 2] + +RFC 7368 IPv6 Home Networking October 2014 + + + 3.5. Routing Functionality . . . . . . . . . . . . . . . . . . 28 + 3.5.1. Unicast Routing within the Homenet . . . . . . . . . 30 + 3.5.2. Unicast Routing at the Homenet Border . . . . . . . . 31 + 3.5.3. Multicast Support . . . . . . . . . . . . . . . . . . 31 + 3.6. Security . . . . . . . . . . . . . . . . . . . . . . . . 32 + 3.6.1. Addressability vs. Reachability . . . . . . . . . . . 32 + 3.6.2. Filtering at Borders . . . . . . . . . . . . . . . . 33 + 3.6.3. Partial Effectiveness of NAT and Firewalls . . . . . 34 + 3.6.4. Exfiltration Concerns . . . . . . . . . . . . . . . . 34 + 3.6.5. Device Capabilities . . . . . . . . . . . . . . . . . 34 + 3.6.6. ULAs as a Hint of Connection Origin . . . . . . . . . 35 + 3.7. Naming and Service Discovery . . . . . . . . . . . . . . 35 + 3.7.1. Discovering Services . . . . . . . . . . . . . . . . 35 + 3.7.2. Assigning Names to Devices . . . . . . . . . . . . . 36 + 3.7.3. The Homenet Name Service . . . . . . . . . . . . . . 37 + 3.7.4. Name Spaces . . . . . . . . . . . . . . . . . . . . . 38 + 3.7.5. Independent Operation . . . . . . . . . . . . . . . . 40 + 3.7.6. Considerations for LLNs . . . . . . . . . . . . . . . 40 + 3.7.7. DNS Resolver Discovery . . . . . . . . . . . . . . . 41 + 3.7.8. Devices Roaming to/from the Homenet . . . . . . . . . 41 + 3.8. Other Considerations . . . . . . . . . . . . . . . . . . 41 + 3.8.1. Quality of Service . . . . . . . . . . . . . . . . . 41 + 3.8.2. Operations and Management . . . . . . . . . . . . . . 42 + 3.9. Implementing the Architecture on IPv6 . . . . . . . . . . 43 + 4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 44 + 5. Security Considerations . . . . . . . . . . . . . . . . . . . 44 + 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 44 + 6.1. Normative References . . . . . . . . . . . . . . . . . . 44 + 6.2. Informative References . . . . . . . . . . . . . . . . . 44 + Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 48 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 49 + + + + + + + + + + + + + + + + + + + + +Chown, et al. Informational [Page 3] + +RFC 7368 IPv6 Home Networking October 2014 + + +1. Introduction + + This document focuses on evolving networking technology within + residential home networks with increasing numbers of devices and a + trend towards increased internal routing, as well as the associated + challenges with their deployment and operation. There is a growing + trend in home networking for the proliferation of networking + technology through an increasingly broad range of devices and media. + This evolution in scale and diversity sets requirements on IETF + protocols. Some of these requirements relate to the introduction of + IPv6, while others relate to the introduction of specialised networks + for home automation and sensors. + + While at the time of writing some complex home network topologies + exist, most are relatively simple single subnet networks and + ostensibly operate using just IPv4. While there may be IPv6 traffic + within the network, e.g., for service discovery, the homenet is + provisioned by the ISP as an IPv4 network. Such networks also + typically employ solutions that should be avoided, such as private + [RFC1918] addressing with (cascaded) Network Address Translation + (NAT) [RFC3022], or they may require expert assistance to set up. + + In contrast, emerging IPv6-capable home networks are very likely to + have multiple internal subnets, e.g., to facilitate private and guest + networks, heterogeneous link layers, and smart grid components, and + have enough address space available to allow every device to have a + globally unique address. This implies that internal routing + functionality is required, and that the homenet's ISP delegates a + large enough address block, to allow assignment of a prefix to each + subnet in the home network. + + It is not practical to expect home users to configure their networks. + Thus, the assumption of this document is that the homenet is as far + as possible self-organising and self-configuring, i.e., it should + function without proactive management by the residential user. + + The architectural constructs in this document are focused on the + problems to be solved when introducing IPv6, with an eye towards a + better result than what we have today with IPv4, as well as aiming + for a more consistent solution that addresses as many of the + identified requirements as possible. This document aims to provide + the basis and guiding principles for how standard IPv6 mechanisms and + addressing [RFC2460] [RFC4291] can be employed in home networking, + while coexisting with existing IPv4 mechanisms. In emerging dual- + stack home networks, it is vital that introducing IPv6 does not + adversely affect IPv4 operation. We assume that the IPv4 network + architecture in home networks is what it is and cannot be modified by + new recommendations. This document does not discuss how IPv4 home + + + +Chown, et al. Informational [Page 4] + +RFC 7368 IPv6 Home Networking October 2014 + + + networks provision or deliver support for multiple subnets. It + should not be assumed that any future new functionality created with + IPv6 in mind will be backward compatible to include IPv4 support. + Further, future deployments, or specific subnets within an otherwise + dual-stack home network, may be IPv6-only, in which case + considerations for IPv4 impact would not apply. + + This document proposes a baseline homenet architecture, using + protocols and implementations that are as far as possible proven and + robust. The scope of the document is primarily the network-layer + technologies that provide the basic functionality to enable + addressing, connectivity, routing, naming, and service discovery. + While it may, for example, state that homenet components must be + simple to deploy and use, it does not discuss specific user + interfaces, nor does it discuss specific physical, wireless, or data- + link-layer considerations. Likewise, we also do not specify the + whole design of a homenet router from top to bottom; rather, we focus + on the Layer 3 aspects. This means that Layer 2 is largely out of + scope, we're assuming a data-link layer that supports IPv6 is + present, and we react accordingly. Any IPv6-over-Foo definitions + occur elsewhere. + + [RFC7084], which has obsoleted [RFC6204], defines basic requirements + for Customer Edge (CE) routers. The update includes the definition + of requirements for specific transition tools on the CE router, + specifically Dual-Stack Lite (DS-Lite) [RFC6333] and IPv6 Rapid + Deployment on IPv4 Infrastructures (6rd) [RFC5969]. Such detailed + specification of CE router devices is considered out of scope of this + architecture document, and we assume that any required update of the + CE router device specification as a result of adopting this + architecture will be handled as separate and specific updates to + these existing documents. Further, the scope of this text is the + internal homenet, and thus specific features on the WAN side of the + CE router are out of scope for this text. + +1.1. Terminology and Abbreviations + + In this section, we define terminology and abbreviations used + throughout the text. + + o Border: A point, typically resident on a router, between two + networks, e.g., between the main internal homenet and a guest + network. This defines a point(s) at which filtering and + forwarding policies for different types of traffic may be applied. + + o CE router: Customer Edge router. A border router intended for use + in a homenet. A CE router connects the homenet to a service + provider network. + + + +Chown, et al. Informational [Page 5] + +RFC 7368 IPv6 Home Networking October 2014 + + + o FQDN: Fully Qualified Domain Name. A globally unique name. + + o Guest network: A part of the home network intended for use by + visitors or guests to the home(net). Devices on the guest network + may typically not see or be able to use all services in the + home(net). + + o Homenet: A home network, comprising host and router equipment, + with one or more CE routers providing connectivity to a service + provider network(s). + + o ISP: Internet Service Provider. An entity that provides access to + the Internet. In this document, a service provider specifically + offers Internet access using IPv6 and may also offer IPv4 Internet + access. The service provider can provide such access over a + variety of different transport methods such as DSL, cable, + wireless, and others. + + o LLN: Low-power and Lossy Network. + + o LQDN: Locally Qualified Domain Name. A name local to the homenet. + + o NAT: Network Address Translation. Typically referring to IPv4 + Network Address Port Translation (NAPT) [RFC3022]. + + o NPTv6: IPv6-to-IPv6 Network Prefix Translation [RFC6296]. + + o PCP: Port Control Protocol [RFC6887]. + + o Realm: A network delimited by a defined border. A guest network + within a homenet may form one realm. + + o 'Simple Security': Defined in [RFC4864] and expanded further in + [RFC6092]; describes recommended perimeter security capabilities + for IPv6 networks. + + o ULA: IPv6 Unique Local Address [RFC4193]. + + o VM: Virtual Machine. + +2. Effects of IPv6 on Home Networking + + While IPv6 resembles IPv4 in many ways, there are some notable + differences in the way it may typically be deployed. It changes + address allocation principles, making multi-addressing the norm, and + through the vastly increased address space, it allows globally unique + IP addresses to be used for all devices in a home network. This + section presents an overview of some of the key implications of the + + + +Chown, et al. Informational [Page 6] + +RFC 7368 IPv6 Home Networking October 2014 + + + introduction of IPv6 for home networking that are simultaneously both + promising and problematic. + +2.1. Multiple Subnets and Routers + + While simple Layer 3 topologies involving as few subnets as possible + are preferred in home networks, the incorporation of dedicated + (routed) subnets remains necessary for a variety of reasons. For + instance, an increasingly common feature in modern home routers is + the ability to support both guest and private network subnets. + Likewise, there may be a need to separate home automation or + corporate extension LANs (whereby a home worker can have their + corporate network extended into the home using a virtual private + network, commonly presented as one port on an Ethernet device) from + the main Internet access network, or different subnets may in general + be associated with parts of the homenet that have different routing + and security policies. Further, link-layer networking technology is + poised to become more heterogeneous as networks begin to employ both + traditional Ethernet technology and link layers designed for Low- + power and Lossy Networks (LLNs), such as those used for certain types + of sensor devices. Constraining the flow of certain traffic from + Ethernet links to links of much lower capacity thus becomes an + important topic. + + The introduction of IPv6 for home networking makes it possible for + every home network to be delegated enough address space from its ISP + to provision globally unique prefixes for each such subnet in the + home. While the number of addresses in a standard /64 IPv6 prefix is + practically unlimited, the number of prefixes available for + assignment to the home network is not. As a result, the growth + inhibitor for the home network shifts from the number of addresses to + the number of prefixes offered by the provider; this topic is + discussed in BCP 157 [RFC6177], which recommends that "end sites + always be able to obtain a reasonable amount of address space for + their actual and planned usage." + + The addition of routing between subnets raises a number of issues. + One is a method by which prefixes can be efficiently allocated to + each subnet, without user intervention. Another issue is how to + extend mechanisms such as zero-configuration service discovery that + currently only operate within a single subnet using link-local + traffic. In a typical IPv4 home network, there is only one subnet, + so such mechanisms would normally operate as expected. For multi- + subnet IPv6 home networks, there are two broad choices to enable such + protocols to work across the scope of the entire homenet: extend + existing protocols to work across that scope or introduce proxies for + existing link-layer protocols. This topic is discussed in + Section 3.7. + + + +Chown, et al. Informational [Page 7] + +RFC 7368 IPv6 Home Networking October 2014 + + +2.2. Global Addressability and Elimination of NAT + + The possibility for direct end-to-end communication on the Internet + to be restored by the introduction of IPv6 is, on the one hand, an + incredible opportunity for innovation and simpler network operation, + but on the other hand, it is also a concern as it potentially exposes + nodes in the internal networks to receipt of unwanted and possibly + malicious traffic from the Internet. + + With devices and applications able to talk directly to each other + when they have globally unique addresses, there may be an expectation + of improved host security to compensate for this. It should be noted + that many devices may (for example) ship with default settings that + make them readily vulnerable to compromise by external attackers if + globally accessible, or they may simply not be robust by design + because it was assumed that either such devices would only be used on + private networks or the devices don't have the computing power to + apply the necessary security methods. In addition, the upgrade cycle + for devices (or their firmware) may be slow and/or lack auto-update + mechanisms. + + It is thus important to distinguish between addressability and + reachability. While IPv6 offers global addressability through the + use of globally unique addresses in the home, whether devices are + globally reachable or not would depend on any firewall or filtering + configuration, and not, as is commonly the case with IPv4, the + presence or use of NAT. In this respect, IPv6 networks may or may + not have filters applied at their borders to control such traffic, + i.e., at the homenet CE router. [RFC4864] and [RFC6092] discuss such + filtering and the merits of 'default allow' against 'default deny' + policies for external traffic initiated into a homenet. This topic + is discussed further in Section 3.6.1. + +2.3. Multi-Addressing of Devices + + In an IPv6 network, devices will often acquire multiple addresses, + typically at least a link-local address and one or more globally + unique addresses (GUAs). Where a homenet is multihomed, a device + would typically receive a GUA from within the delegated prefix from + each upstream ISP. Devices may also have an IPv4 address if the + network is dual stack, an IPv6 Unique Local Address (ULA) [RFC4193] + (see below), and one or more IPv6 privacy addresses [RFC4941]. + + It should thus be considered the norm for devices on IPv6 home + networks to be multi-addressed and to need to make appropriate + address selection decisions for the candidate source and destination + address pairs for any given connection. In multihoming scenarios, + nodes will be configured with one address from each upstream ISP + + + +Chown, et al. Informational [Page 8] + +RFC 7368 IPv6 Home Networking October 2014 + + + prefix. In such cases, the presence of upstream ingress filtering as + described in BCP 38 [RFC2827] requires such multi-addressed nodes to + select the correct source address to be used for the corresponding + uplink. Default address selection for IPv6 [RFC6724] provides a + solution for this, but a challenge here is that the node may not have + the information it needs to make that decision based on addresses + alone. We discuss this challenge in Section 3.2.4. + +2.4. Unique Local Addresses (ULAs) + + [RFC4193] defines ULAs for IPv6 that may be used to address devices + within the scope of a single site. Support for ULAs for IPv6 CE + routers is described in [RFC7084]. A home network running IPv6 + should deploy ULAs alongside its globally unique prefix(es) to allow + stable communication between devices (on different subnets) within + the homenet where that externally allocated globally unique prefix + may change over time, e.g., due to renumbering within the + subscriber's ISP, or where external connectivity may be temporarily + unavailable. A homenet using provider-assigned global addresses is + exposed to its ISP renumbering the network to a much larger degree + than before whereas, for IPv4, NAT isolated the user against ISP + renumbering to some extent. + + While setting up a network, there may be a period where it has no + external connectivity, in which case ULAs would be required for + inter-subnet communication. In the case where home automation + networks are being set up in a new home/deployment (as early as + during construction of the home), such networks will likely need to + use their own /48 ULA prefix. Depending upon circumstances beyond + the control of the owner of the homenet, it may be impossible to + renumber the ULA used by the home automation network so routing + between ULA /48s may be required. Also, some devices, particularly + constrained devices, may have only a ULA (in addition to a link- + local), while others may have both a GUA and a ULA. + + Note that unlike private IPv4 space as described in RFC 1918, the use + of ULAs does not imply use of an IPv6 equivalent of a traditional + IPv4 NAT [RFC3022] or of NPTv6 prefix-based NAT [RFC6296]. When an + IPv6 node in a homenet has both a ULA and a globally unique IPv6 + address, it should only use its ULA address internally and use its + additional globally unique IPv6 address as a source address for + external communications. This should be the natural behaviour given + support for default address selection for IPv6 [RFC6724]. By using + such globally unique addresses between hosts and devices in remote + networks, the architectural cost and complexity, particularly to + applications, of NAT or NPTv6 translation are avoided. As such, + neither IPv6 NAT nor NPTv6 is recommended for use in the homenet + architecture. Further, the homenet border router(s) should filter + + + +Chown, et al. Informational [Page 9] + +RFC 7368 IPv6 Home Networking October 2014 + + + packets with ULA source/destination addresses as discussed in + Section 3.4.2. + + Devices in a homenet may be given only a ULA as a means to restrict + reachability from outside the homenet. ULAs can be used by default + for devices that, without additional configuration (e.g., via a web + interface), would only offer services to the internal network. For + example, a printer might only accept incoming connections on a ULA + until configured to be globally reachable, at which point it acquires + a global IPv6 address and may be advertised via a global name space. + + Where both a ULA and a global prefix are in use, the ULA source + address is used to communicate with ULA destination addresses when + appropriate, i.e., when the ULA source and destination lie within the + /48 ULA prefix(es) known to be used within the same homenet. In + cases where multiple /48 ULA prefixes are in use within a single + homenet (perhaps because multiple homenet routers each independently + auto-generate a /48 ULA prefix and then share prefix/routing + information), utilising a ULA source address and a ULA destination + address from two disjoint internal ULA prefixes is preferable to + using GUAs. + + While a homenet should operate correctly with two or more /48 ULAs + enabled, a mechanism for the creation and use of a single /48 ULA + prefix is desirable for addressing consistency and policy + enforcement. + + A counter argument to using ULAs is that it is undesirable to + aggressively deprecate global prefixes for temporary loss of + connectivity, so for a host to lose its global address, there would + have to be a connection breakage longer than the lease period, and + even then, deprecating prefixes when there is no connectivity may not + be advisable. However, it is assumed in this architecture that + homenets should support and use ULAs. + +2.5. Avoiding Manual Configuration of IP Addresses + + Some IPv4 home networking devices expose IPv4 addresses to users, + e.g., the IPv4 address of a home IPv4 CE router that may be + configured via a web interface. In potentially complex future IPv6 + homenets, users should not be expected to enter IPv6 literal + addresses in devices or applications, given their much greater length + and the apparent randomness of such addresses to a typical home user. + Thus, even for the simplest of functions, simple naming and the + associated (minimal, and ideally zero configuration) discovery of + services are imperative for the easy deployment and use of homenet + devices and applications. + + + + +Chown, et al. Informational [Page 10] + +RFC 7368 IPv6 Home Networking October 2014 + + +2.6. IPv6-Only Operation + + It is likely that IPv6-only networking will be deployed first in new + home network deployments, often referred to as 'greenfield' + scenarios, where there is no existing IPv4 capability, or perhaps as + one element of an otherwise dual-stack network. Running IPv6-only + adds additional requirements, e.g., for devices to get configuration + information via IPv6 transport (not relying on an IPv4 protocol such + as IPv4 DHCP) and for devices to be able to initiate communications + to external devices that are IPv4-only. + + Some specific transition technologies that may be deployed by the + homenet's ISP are discussed in [RFC7084]. In addition, certain other + functions may be desirable on the CE router, e.g., to access content + in the IPv4 Internet, NAT64 [RFC6144] and DNS64 [RFC6145] may be + applicable. + + The widespread availability of robust solutions to these types of + requirements will help accelerate the uptake of IPv6-only homenets. + The specifics of these are, however, beyond the scope of this + document, especially those functions that reside on the CE router. + +3. Homenet Architecture Principles + + The aim of this text is to outline how to construct advanced IPv6- + based home networks involving multiple routers and subnets using + standard IPv6 addressing and protocols [RFC2460] [RFC4291] as the + basis. As described in Section 3.1, solutions should as far as + possible reuse existing protocols and minimise changes to hosts and + routers, but some new protocols or extensions are likely to be + required. In this section, we present the elements of the proposed + home networking architecture with discussion of the associated design + principles. + + In general, home network equipment needs to be able to operate in + networks with a range of different properties and topologies, where + home users may plug components together in arbitrary ways and expect + the resulting network to operate. Significant manual configuration + is rarely, if at all, possible or even desirable given the knowledge + level of typical home users. Thus, the network should, as far as + possible, be self-configuring, though configuration by advanced users + should not be precluded. + + + + + + + + + +Chown, et al. Informational [Page 11] + +RFC 7368 IPv6 Home Networking October 2014 + + + The homenet needs to be able to handle or provision at least the + following: + + o Routing + + o Prefix configuration for routers + + o Name resolution + + o Service discovery + + o Network security + + The remainder of this document describes the principles by which the + homenet architecture may deliver these properties. + +3.1. General Principles + + There is little that the Internet standards community can do about + the physical topologies or the need for some networks to be separated + at the network layer for policy or link-layer compatibility reasons. + However, there is a lot of flexibility in using IP addressing and + internetworking mechanisms. This text discusses how such flexibility + should be used to provide the best user experience and ensure that + the network can evolve with new applications in the future. The + principles described in this text should be followed when designing + homenet protocol solutions. + +3.1.1. Reuse Existing Protocols + + Existing protocols will be used to meet the requirements of home + networks. Where necessary, extensions will be made to those + protocols. When no existing protocol is found to be suitable, a new + or emerging protocol may be used. Therefore, it is important that no + design or architectural decisions be made that would preclude the use + of new or emerging protocols. + + A generally conservative approach, giving weight to running (and + available) code, is preferable. Where new protocols are required, + evidence of commitment to implementation by appropriate vendors or + development communities is highly desirable. Protocols used should + be backward compatible and forward compatible where changes are made. + + + + + + + + + +Chown, et al. Informational [Page 12] + +RFC 7368 IPv6 Home Networking October 2014 + + +3.1.2. Minimise Changes to Hosts and Routers + + In order to maximise the deployability of new homenets, any + requirement for changes to hosts and routers should be minimised + where possible; however, solutions that, for example, incrementally + improve capability via host or router changes may be acceptable. + There may be cases where changes are unavoidable, e.g., to allow a + given homenet routing protocol to be self-configuring or to support + routing based on source addresses in addition to destination + addresses (to improve multihoming support, as discussed in + Section 3.2.4). + +3.2. Homenet Topology + + This section considers homenet topologies and the principles that may + be applied in designing an architecture to support as wide a range of + such topologies as possible. + +3.2.1. Supporting Arbitrary Topologies + + There should ideally be no built-in assumptions about the topology in + home networks, as users are capable of connecting their devices in + 'ingenious' ways. Thus, arbitrary topologies and arbitrary routing + will need to be supported, or at least the failure mode for when the + user makes a mistake should be as robust as possible, e.g., + deactivating a certain part of the infrastructure to allow the rest + to operate. In such cases, the user should ideally have some useful + indication of the failure mode encountered. + + There should be no topology scenarios that cause a loss of + connectivity, except when the user creates a physical island within + the topology. Some potentially pathological cases that can be + created include bridging ports of a router together; however, this + case can be detected and dealt with by the router. Loops within a + routed topology are in a sense good in that they offer redundancy. + Topologies that include potential bridging loops can be dangerous but + are also detectable when a switch learns the Media Access Control + (MAC) address of one of its interfaces on another or runs a spanning + tree or link-state protocol. It is only topologies with such + potential loops using simple repeaters that are truly pathological. + + The topology of the homenet may change over time, due to the addition + or removal of equipment but also due to temporary failures or + connectivity problems. In some cases, this may lead to, for example, + a multihomed homenet being split into two isolated homenets or, after + such a fault is remedied, two isolated parts reconfiguring back to a + single network. + + + + +Chown, et al. Informational [Page 13] + +RFC 7368 IPv6 Home Networking October 2014 + + +3.2.2. Network Topology Models + + As hinted above, while the architecture may focus on likely common + topologies, it should not preclude any arbitrary topology from being + constructed. + + At the time of writing, most IPv4 home network models tend to be + relatively simple, typically a single NAT router to the ISP and a + single internal subnet but, as discussed earlier, evolution in + network architectures is driving more complex topologies, such as the + separation of guest and private networks. There may also be some + cascaded IPv4 NAT scenarios, which we mention in the next section. + For IPv6 homenets, the network architectures described in [RFC7084] + should, as a minimum, be supported. + + There are a number of properties or attributes of a home network that + we can use to describe its topology and operation. The following + properties apply to any IPv6 home network: + + o Presence of internal routers. The homenet may have one or more + internal routers or may only provide subnetting from interfaces on + the CE router. + + o Presence of isolated internal subnets. There may be isolated + internal subnets, with no direct connectivity between them within + the homenet (with each having its own external connectivity). + Isolation may be physical or implemented via IEEE 802.1q VLANs. + The latter is, however, not something a typical user would be + expected to configure. + + o Demarcation of the CE router. The CE router(s) may or may not be + managed by the ISP. If the demarcation point is such that the + customer can provide or manage the CE router, its configuration + must be simple. Both models must be supported. + + Various forms of multihoming are likely to become more prevalent with + IPv6 home networks, where the homenet may have two or more external + ISP connections, as discussed further below. Thus, the following + properties should also be considered for such networks: + + o Number of upstream providers. The majority of home networks today + consist of a single upstream ISP, but it may become more common in + the future for there to be multiple ISPs, whether for resilience + or provision of additional services. Each would offer its own + prefix. Some may or may not provide a default route to the public + Internet. + + + + + +Chown, et al. Informational [Page 14] + +RFC 7368 IPv6 Home Networking October 2014 + + + o Number of CE routers. The homenet may have a single CE router, + which might be used for one or more providers, or multiple CE + routers. The presence of multiple CE routers adds additional + complexity for multihoming scenarios and protocols like PCP that + may need to manage connection-oriented state mappings on the same + CE router as used for subsequent traffic flows. + + In the following sections, we give some examples of the types of + homenet topologies we may see in the future. This is not intended to + be an exhaustive or complete list but rather an indicative one to + facilitate the discussion in this text. + +3.2.2.1. A: Single ISP, Single CE Router, and Internal Routers + + Figure 1 shows a home network with multiple local area networks. + These may be needed for reasons relating to different link-layer + technologies in use or for policy reasons, e.g., classic Ethernet in + one subnet and an LLN link-layer technology in another. In this + example, there is no single router that a priori understands the + entire topology. The topology itself may also be complex, and it may + not be possible to assume a pure tree form, for instance (because + home users may plug routers together to form arbitrary topologies, + including those with potential loops in them). + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Chown, et al. Informational [Page 15] + +RFC 7368 IPv6 Home Networking October 2014 + + + +-------+-------+ \ + | Service | \ + | Provider | | Service + | Router | | Provider + +-------+-------+ | Network + | / + | Customer / + | Internet Connection + | + +------+--------+ \ + | IPv6 | \ + | Customer Edge | \ + | Router | | + +----+-+---+----+ | + Network A | | | Network B(E) | + ----+-------------+----+ | +---+-------------+------+ | + | | | | | | | + +----+-----+ +-----+----+ | +----+-----+ +-----+----+ | | + |IPv6 Host | |IPv6 Host | | | IPv6 Host| |IPv6 Host | | | + | H1 | | H2 | | | H3 | | H4 | | | + +----------+ +----------+ | +----------+ +----------+ | | + | | | | | + Link F | ---+------+------+-----+ | + | | Network E(B) | + +------+--------+ | | End-User + | IPv6 | | | Networks + | Interior +------+ | + | Router | | + +---+-------+-+-+ | + Network C | | Network D | + ----+-------------+---+ +---+-------------+--- | + | | | | | + +----+-----+ +-----+----+ +----+-----+ +-----+----+ | + |IPv6 Host | |IPv6 Host | | IPv6 Host| |IPv6 Host | | + | H5 | | H6 | | H7 | | H8 | / + +----------+ +----------+ +----------+ +----------+ / + + Figure 1 + + In this diagram, there is one CE router. It has a single uplink + interface. It has three additional interfaces connected to Network + A, Link F, and Network B. The IPv6 Internal Router (IR) has four + interfaces connected to Link F, Network C, Network D, and Network E. + Network B and Network E have been bridged, likely inadvertently. + This could be as a result of connecting a wire between a switch for + Network B and a switch for Network E. + + + + + +Chown, et al. Informational [Page 16] + +RFC 7368 IPv6 Home Networking October 2014 + + + Any of logical Networks A through F might be wired or wireless. + Where multiple hosts are shown, this might be through one or more + physical ports on the CE router or IPv6 (IR), wireless networks, or + through one or more Ethernet switches that are Layer 2 only. + +3.2.2.2. B: Two ISPs, Two CE Routers, and Shared Subnet + + +-------+-------+ +-------+-------+ \ + | Service | | Service | \ + | Provider A | | Provider B | | Service + | Router | | Router | | Provider + +------+--------+ +-------+-------+ | Network + | | / + | Customer | / + | Internet Connections | / + | | + +------+--------+ +-------+-------+ \ + | IPv6 | | IPv6 | \ + | Customer Edge | | Customer Edge | \ + | Router 1 | | Router 2 | / + +------+--------+ +-------+-------+ / + | | / + | | | End-User + ---+---------+---+---------------+--+----------+--- | Network(s) + | | | | \ + +----+-----+ +-----+----+ +----+-----+ +-----+----+ \ + |IPv6 Host | |IPv6 Host | | IPv6 Host| |IPv6 Host | / + | H1 | | H2 | | H3 | | H4 | / + +----------+ +----------+ +----------+ +----------+ + + Figure 2 + + Figure 2 illustrates a multihomed homenet model, where the customer + has connectivity via CE router 1 to ISP A and via CE router 2 to ISP + B. This example shows one shared subnet where IPv6 nodes would + potentially be multihomed and receive multiple IPv6 global prefixes, + one per ISP. This model may also be combined with that shown in + Figure 1 to create a more complex scenario with multiple internal + routers. Or, the above shared subnet may be split in two, such that + each CE router serves a separate isolated subnet, which is a scenario + seen with some IPv4 networks today. + + + + + + + + + + +Chown, et al. Informational [Page 17] + +RFC 7368 IPv6 Home Networking October 2014 + + +3.2.2.3. C: Two ISPs, One CE Router, and Shared Subnet + + +-------+-------+ +-------+-------+ \ + | Service | | Service | \ + | Provider A | | Provider B | | Service + | Router | | Router | | Provider + +-------+-------+ +------+--------+ | Network + | | / + | Customer | / + | Internet | / + | Connections | + +-----------+-----------+ \ + | IPv6 | \ + | Customer Edge | \ + | Router | / + +-----------+-----------+ / + | / + | | End-User + ---+------------+-------+--------+-------------+--- | Network(s) + | | | | \ + +----+-----+ +----+-----+ +----+-----+ +-----+----+ \ + |IPv6 Host | |IPv6 Host | | IPv6 Host| |IPv6 Host | / + | H1 | | H2 | | H3 | | H4 | / + +----------+ +----------+ +----------+ +----------+ + + Figure 3 + + Figure 3 illustrates a model where a home network may have multiple + connections to multiple providers or multiple logical connections to + the same provider, with shared internal subnets. + +3.2.3. Dual-Stack Topologies + + For the immediate future, it is expected that most homenet + deployments will be dual-stack IPv4/IPv6. In such networks, it is + important not to introduce new IPv6 capabilities that would cause a + failure if used alongside IPv4+NAT, given that such dual-stack + homenets will be commonplace for some time. That said, it is + desirable that IPv6 works better than IPv4 in as many scenarios as + possible. Further, the homenet architecture must operate in the + absence of IPv4. + + A general recommendation is to follow the same topology for IPv6 as + is used for IPv4 but not to use NAT. Thus, there should be routed + IPv6 where an IPv4 NAT is used, and where there is no NAT, routing or + bridging may be used. Routing may have advantages when compared to + bridging together high- and lower-speed shared media, and in + + + + +Chown, et al. Informational [Page 18] + +RFC 7368 IPv6 Home Networking October 2014 + + + addition, bridging may not be suitable for some networks, such as ad + hoc mobile networks. + + In some cases, IPv4 home networks may feature cascaded NATs. End + users are frequently unaware that they have created such networks, as + 'home routers' and 'home switches' are frequently confused. In + addition, there are cases where NAT routers are included within + Virtual Machine Hypervisors or where Internet connection-sharing + services have been enabled. This document applies equally to such + hidden NAT 'routers'. IPv6-routed versions of such cases will be + required. We should thus also note that routers in the homenet may + not be separate physical devices; they may be embedded within other + devices. + +3.2.4. Multihoming + + A homenet may be multihomed to multiple providers, as the network + models above illustrate. This may take a form where there are either + multiple isolated networks within the home or a more integrated + network where the connectivity selection needs to be dynamic. + Current practice is typically of the former kind, but the latter is + expected to become more commonplace. + + In the general homenet architecture, multihomed hosts should be + multi-addressed with a global IPv6 address from the global prefix + delegated from each ISP they communicate with or through. When such + multi-addressing is in use, hosts need some way to pick source and + destination address pairs for connections. A host may choose a + source address to use by various methods, most commonly [RFC6724]. + Applications may of course do different things, and this should not + be precluded. + + For the single CE Router Network Model C illustrated above, + multihoming may be offered by source-based routing at the CE router. + With multiple exit routers, as in CE Router Network Model B, the + complexity rises. Given a packet with a source address on the home + network, the packet must be routed to the proper egress to avoid + ingress filtering as described in BCP 38 if exiting through the wrong + ISP. It is highly desirable that the packet is routed in the most + efficient manner to the correct exit, though as a minimum requirement + the packet should not be dropped. + + The homenet architecture should support both the above models, i.e., + one or more CE routers. However, the general multihoming problem is + broad, and solutions suggested to date within the IETF have included + complex architectures for monitoring connectivity, traffic + engineering, identifier-locator separation, connection survivability + across multihoming events, and so on. It is thus important that the + + + +Chown, et al. Informational [Page 19] + +RFC 7368 IPv6 Home Networking October 2014 + + + homenet architecture should as far as possible minimise the + complexity of any multihoming support. + + An example of such a 'simpler' approach has been documented in + [RFC7157]. Alternatively, a flooding/routing protocol could + potentially be used to pass information through the homenet, such + that internal routers and ultimately end hosts could learn per-prefix + configuration information, allowing better address selection + decisions to be made. However, this would imply router and, most + likely, host changes. Another avenue is to introduce support + throughout the homenet for routing that is based on the source as + well as the destination address of each packet. While greatly + improving the 'intelligence' of routing decisions within the homenet, + such an approach would require relatively significant router changes + but avoid host changes. + + As explained previously, while NPTv6 has been proposed for providing + multihoming support in networks, its use is not recommended in the + homenet architecture. + + It should be noted that some multihoming scenarios may see one + upstream being a "walled garden" and thus only appropriate for + connectivity to the services of that provider; an example may be a + VPN service that only routes back to the enterprise business network + of a user in the homenet. As per Section 4.2.1 of [RFC3002], we do + not specifically target walled-garden multihoming as a goal of this + document. + + The homenet architecture should also not preclude use of host or + application-oriented tools, e.g., Shim6 [RFC5533], Multipath TCP + (MPTCP) [RFC6824], or Happy Eyeballs [RFC6555]. In general, any + incremental improvements obtained by host changes should give benefit + for the hosts introducing them but should not be required. + +3.2.5. Mobility Support + + Devices may be mobile within the homenet. While resident on the same + subnet, their address will remain persistent, but should devices move + to a different (wireless) subnet, they will acquire a new address in + that subnet. It is desirable that the homenet supports internal + device mobility. To do so, the homenet may either extend the reach + of specific wireless subnets to enable wireless roaming across the + home (availability of a specific subnet across the home) or support + mobility protocols to facilitate such roaming where multiple subnets + are used. + + + + + + +Chown, et al. Informational [Page 20] + +RFC 7368 IPv6 Home Networking October 2014 + + +3.3. A Self-Organising Network + + The home network infrastructure should be naturally self-organising + and self-configuring under different circumstances relating to the + connectivity status to the Internet, number of devices, and physical + topology. At the same time, it should be possible for advanced users + to manually adjust (override) the current configuration. + + While a goal of the homenet architecture is for the network to be as + self-organising as possible, there may be instances where some manual + configuration is required, e.g., the entry of a cryptographic key to + apply wireless security or to configure a shared routing secret. The + latter may be relevant when considering how to bootstrap a routing + configuration. It is highly desirable that the number of such + configurations is minimised. + +3.3.1. Differentiating Neighbouring Homenets + + It is important that self-configuration with 'unintended' devices be + avoided. There should be a way for a user to administratively assert + in a simple way whether or not a device belongs to a given homenet. + The goal is to allow the establishment of borders, particularly + between two adjacent homenets, and to avoid unauthorised devices from + participating in the homenet. Such an authorisation capability may + need to operate through multiple hops in the homenet. + + The homenet should thus support a way for a homenet owner to claim + ownership of their devices in a reasonably secure way. This could be + achieved by a pairing mechanism by, for example, pressing buttons + simultaneously on an authenticated and a new homenet device or by an + enrollment process as part of an autonomic networking environment. + + While there may be scenarios where one homenet may wish to + intentionally gain access through another, e.g., to share external + connectivity costs, such scenarios are not discussed in this + document. + +3.3.2. Largest Practical Subnets + + Today's IPv4 home networks generally have a single subnet, and early + dual-stack deployments have a single congruent IPv6 subnet, possibly + with some bridging functionality. More recently, some vendors have + started to introduce 'home' and 'guest' functions, which in IPv6 + would be implemented as two subnets. + + Future home networks are highly likely to have one or more internal + routers and thus need multiple subnets for the reasons described + earlier. As part of the self-organisation of the network, the + + + +Chown, et al. Informational [Page 21] + +RFC 7368 IPv6 Home Networking October 2014 + + + homenet should subdivide itself into the largest practical subnets + that can be constructed within the constraints of link-layer + mechanisms, bridging, physical connectivity, and policy, and where + applicable, performance or other criteria. In such subdivisions, the + logical topology may not necessarily match the physical topology. + This text does not, however, make recommendations on how such + subdivision should occur. It is expected that subsequent documents + will address this problem. + + While it may be desirable to maximise the chance of link-local + protocols operating across a homenet by maximising the size of a + subnet, multi-subnet home networks are inevitable, so their support + must be included. + +3.3.3. Handling Varying Link Technologies + + Homenets tend to grow organically over many years, and a homenet will + typically be built over link-layer technologies from different + generations. Current homenets typically use links ranging from 1 + Mbit/s up to 1 Gbit/s -- a throughput discrepancy of three orders of + magnitude. We expect this discrepancy to widen further as both high- + speed and low-power technologies are deployed. + + Homenet protocols should be designed to deal well with + interconnecting links of very different throughputs. In particular, + flows local to a link should not be flooded throughout the homenet, + even when sent over multicast, and, whenever possible, the homenet + protocols should be able to choose the faster links and avoid the + slower ones. + + Links (particularly wireless links) may also have limited numbers of + transmit opportunities (txops), and there is a clear trend driven by + both power and downward compatibility constraints toward aggregation + of packets into these limited txops while increasing throughput. + Transmit opportunities may be a system's scarcest resource and, + therefore, also strongly limit actual throughput available. + +3.3.4. Homenet Realms and Borders + + The homenet will need to be aware of the extent of its own 'site', + which will, for example, define the borders for ULA and site scope + multicast traffic and may require specific security policies to be + applied. The homenet will have one or more such borders with + external connectivity providers. + + A homenet will most likely also have internal borders between + internal realms, e.g., a guest realm or a corporate network extension + realm. It is desirable that appropriate borders can be configured to + + + +Chown, et al. Informational [Page 22] + +RFC 7368 IPv6 Home Networking October 2014 + + + determine, for example, the scope of where network prefixes, routing + information, network traffic, service discovery, and naming may be + shared. The default mode internally should be to share everything. + + It is expected that a realm would span at least an entire subnet, and + thus the borders lie at routers that receive delegated prefixes + within the homenet. It is also desirable, for a richer security + model, that hosts are able to make communication decisions based on + available realm and associated prefix information in the same way + that routers at realm borders can. + + A simple homenet model may just consider three types of realms and + the borders between them, namely the internal homenet, the ISP, and a + guest network. In this case, the borders will include the border + from the homenet to the ISP, the border from the guest network to the + ISP, and the border from the homenet to the guest network. + Regardless, it should be possible for additional types of realms and + borders to be defined, e.g., for some specific LLN-based network, + such as Smart Grid, and for these to be detected automatically and + for an appropriate default policy to be applied as to what type of + traffic/data can flow across such borders. + + It is desirable to classify the external border of the home network + as a unique logical interface separating the home network from a + service provider network(s). This border interface may be a single + physical interface to a single service provider, multiple Layer 2 + sub-interfaces to a single service provider, or multiple connections + to a single or multiple providers. This border makes it possible to + describe edge operations and interface requirements across multiple + functional areas including security, routing, service discovery, and + router discovery. + + It should be possible for the homenet user to override any + automatically determined borders and the default policies applied + between them, the exception being that it may not be possible to + override policies defined by the ISP at the external border. + +3.3.5. Configuration Information from the ISP + + In certain cases, it may be useful for the homenet to get certain + configuration information from its ISP. For example, the homenet + DHCP server may request and forward some options that it gets from + its upstream DHCP server, though the specifics of the options may + vary across deployments. There is potential complexity here, of + course, should the homenet be multihomed. + + + + + + +Chown, et al. Informational [Page 23] + +RFC 7368 IPv6 Home Networking October 2014 + + +3.4. Homenet Addressing + + The IPv6 addressing scheme used within a homenet must conform to the + IPv6 addressing architecture [RFC4291]. In this section, we discuss + how the homenet needs to adapt to the prefixes made available to it + by its upstream ISP, such that internal subnets, hosts, and devices + can obtain and configure the necessary addressing information to + operate. + +3.4.1. Use of ISP-Delegated IPv6 Prefixes + + Discussion of IPv6 prefix allocation policies is included in + [RFC6177]. In practice, a homenet may receive an arbitrary length + IPv6 prefix from its provider, e.g., /60, /56, or /48. The offered + prefix may be stable or change from time to time; it is generally + expected that ISPs will offer relatively stable prefixes to their + residential customers. Regardless, the home network needs to be + adaptable as far as possible to ISP prefix allocation policies and + assume nothing about the stability of the prefix received from an ISP + or the length of the prefix that may be offered. + + However, if, for example, only a /64 is offered by the ISP, the + homenet may be severely constrained or even unable to function. BCP + 157 [RFC6177] states the following: + + A key principle for address management is that end sites always be + able to obtain a reasonable amount of address space for their + actual and planned usage, and over time ranges specified in years + rather than just months. In practice, that means at least one + /64, and in most cases significantly more. One particular + situation that must be avoided is having an end site feel + compelled to use IPv6-to-IPv6 Network Address Translation or other + burdensome address conservation techniques because it could not + get sufficient address space. + + This architecture document assumes that the guidance in the quoted + text is being followed by ISPs. + + There are many problems that would arise from a homenet not being + offered a sufficient prefix size for its needs. Rather than attempt + to contrive a method for a homenet to operate in a constrained manner + when faced with insufficient prefixes, such as the use of subnet + prefixes longer than /64 (which would break stateless address + autoconfiguration [RFC4862]), the use of NPTv6, or falling back to + bridging across potentially very different media, it is recommended + that the receiving router instead enters an error state and issues + appropriate warnings. Some consideration may need to be given to how + + + + +Chown, et al. Informational [Page 24] + +RFC 7368 IPv6 Home Networking October 2014 + + + such a warning or error state should best be presented to a typical + home user. + + Thus, a homenet CE router should request, for example, via DHCP + Prefix Delegation (DHCP PD) [RFC3633], that it would like a /48 + prefix from its ISP, i.e., it asks the ISP for the maximum size + prefix it might expect to be offered, even if in practice it may only + be offered a /56 or /60. For a typical IPv6 homenet, it is not + recommended that an ISP offers less than a /60 prefix, and it is + highly preferable that the ISP offers at least a /56. It is expected + that the allocated prefix to the homenet from any single ISP is a + contiguous, aggregated one. While it may be possible for a homenet + CE router to issue multiple prefix requests to attempt to obtain + multiple delegations, such behaviour is out of scope of this + document. + + The norm for residential customers of large ISPs may be similar to + their single IPv4 address provision; by default it is likely to + remain persistent for some time, but changes in the ISP's own + provisioning systems may lead to the customer's IP (and in the IPv6 + case their prefix pool) changing. It is not expected that ISPs will + generally support Provider Independent (PI) addressing for + residential homenets. + + When an ISP does need to restructure, and in doing so renumber its + customer homenets, 'flash' renumbering is likely to be imposed. This + implies a need for the homenet to be able to handle a sudden + renumbering event that, unlike the process described in [RFC4192], + would be a 'flag day' event, which means that a graceful renumbering + process moving through a state with two active prefixes in use would + not be possible. While renumbering can be viewed as an extended + version of an initial numbering process, the difference between flash + renumbering and an initial 'cold start' is the need to provide + service continuity. + + There may be cases where local law means some ISPs are required to + change IPv6 prefixes (current IPv4 addresses) for privacy reasons for + their customers. In such cases, it may be possible to avoid an + instant 'flash' renumbering and plan a non-flag day renumbering as + per RFC 4192. Similarly, if an ISP has a planned renumbering + process, it may be able to adjust lease timers, etc., appropriately. + + The customer may of course also choose to move to a new ISP and thus + begin using a new prefix. In such cases, the customer should expect + a discontinuity, and not only may the prefix change, but potentially + also the prefix length if the new ISP offers a different default size + prefix. The homenet may also be forced to renumber itself if + significant internal 'replumbing' is undertaken by the user. + + + +Chown, et al. Informational [Page 25] + +RFC 7368 IPv6 Home Networking October 2014 + + + Regardless, it's desirable that homenet protocols support rapid + renumbering and that operational processes don't add unnecessary + complexity for the renumbering process. Further, the introduction of + any new homenet protocols should not make any form of renumbering any + more complex than it already is. + + Finally, the internal operation of the home network should also not + depend on the availability of the ISP network at any given time, + other than, of course, for connectivity to services or systems off + the home network. This reinforces the use of ULAs for stable + internal communication and the need for a naming and service + discovery mechanism that can operate independently within the + homenet. + +3.4.2. Stable Internal IP Addresses + + The network should by default attempt to provide IP-layer + connectivity between all internal parts of the homenet as well as to + and from the external Internet, subject to the filtering policies or + other policy constraints discussed later in the security section. + + ULAs should be used within the scope of a homenet to support stable + routing and connectivity between subnets and hosts regardless of + whether a globally unique ISP-provided prefix is available. In the + case of a prolonged external connectivity outage, ULAs allow internal + operations across routed subnets to continue. ULA addresses also + allow constrained devices to create permanent relationships between + IPv6 addresses, e.g., from a wall controller to a lamp, where + symbolic host names would require additional non-volatile memory, and + updating global prefixes in sleeping devices might also be + problematic. + + As discussed previously, it would be expected that ULAs would + normally be used alongside one or more global prefixes in a homenet, + such that hosts become multi-addressed with both globally unique and + ULA prefixes. ULAs should be used for all devices, not just those + intended to only have internal connectivity. Default address + selection would then enable ULAs to be preferred for internal + communications between devices that are using ULA prefixes generated + within the same homenet. + + In cases where ULA prefixes are in use within a homenet but there is + no external IPv6 connectivity (and thus no GUAs in use), + recommendations ULA-5, L-3, and L-4 in RFC 7084 should be followed to + ensure correct operation, in particular where the homenet may be dual + stack with IPv4 external connectivity. The use of the Route + Information Option described in [RFC4191] provides a mechanism to + advertise such more-specific ULA routes. + + + +Chown, et al. Informational [Page 26] + +RFC 7368 IPv6 Home Networking October 2014 + + + The use of ULAs should be restricted to the homenet scope through + filtering at the border(s) of the homenet, as mandated by RFC 7084 + requirement S-2. + + Note that in some cases, it is possible that multiple /48 ULA + prefixes may be in use within the same homenet, e.g., when the + network is being deployed, perhaps also without external + connectivity. In cases where multiple ULA /48s are in use, hosts + need to know that each /48 is local to the homenet, e.g., by + inclusion in their local address selection policy table. + +3.4.3. Internal Prefix Delegation + + As mentioned above, there are various sources of prefixes. From the + homenet perspective, a single global prefix from each ISP should be + received on the border CE router [RFC3633]. Where multiple CE + routers exist with multiple ISP prefix pools, it is expected that + routers within the homenet would assign themselves prefixes from each + ISP they communicate with/through. As discussed above, a ULA prefix + should be provisioned for stable internal communications or for use + on constrained/LLN networks. + + The delegation or availability of a prefix pool to the homenet should + allow subsequent internal autonomous assignment of prefixes for use + within the homenet. Such internal assignment should not assume a + flat or hierarchical model, nor should it make an assumption about + whether the assignment of internal prefixes is distributed or + centralised. The assignment mechanism should provide reasonable + efficiency, so that typical home network prefix allocation sizes can + accommodate all the necessary /64 allocations in most cases, and not + waste prefixes. Further, duplicate assignment of multiple /64s to + the same network should be avoided, and the network should behave as + gracefully as possible in the event of prefix exhaustion (though the + options in such cases may be limited). + + Where the home network has multiple CE routers and these are + delegated prefix pools from their attached ISPs, the internal prefix + assignment would be expected to be served by each CE router for each + prefix associated with it. Where ULAs are used, it is preferable + that only one /48 ULA covers the whole homenet, from which /64s can + be assigned to the subnets. In cases where two /48 ULAs are + generated within a homenet, the network should still continue to + function, meaning that hosts will need to determine that each ULA is + local to the homenet. + + Prefix assignment within the homenet should result in each link being + assigned a stable prefix that is persistent across reboots, power + outages, and similar short-term outages. The availability of + + + +Chown, et al. Informational [Page 27] + +RFC 7368 IPv6 Home Networking October 2014 + + + persistent prefixes should not depend on the router boot order. The + addition of a new routing device should not affect existing + persistent prefixes, but persistence may not be expected in the face + of significant 'replumbing' of the homenet. However, assigned ULA + prefixes within the homenet should remain persistent through an ISP- + driven renumbering event. + + Provisioning such persistent prefixes may imply the need for stable + storage on routing devices and also a method for a home user to + 'reset' the stored prefix should a significant reconfiguration be + required (though ideally the home user should not be involved at + all). + + This document makes no specific recommendation towards solutions but + notes that it is very likely that all routing devices participating + in a homenet must use the same internal prefix delegation method. + This implies that only one delegation method should be in use. + +3.4.4. Coordination of Configuration Information + + The network elements will need to be integrated in a way that takes + account of the various lifetimes on timers that are used on different + elements, e.g., DHCPv6 PD, router, valid prefix, and preferred prefix + timers. + +3.4.5. Privacy + + If ISPs offer relatively stable IPv6 prefixes to customers, the + network prefix part of addresses associated with the homenet may not + change over a reasonably long period of time. + + The exposure of which traffic is sourced from the same homenet is + thus similar to IPv4; the single IPv4 global address seen through use + of IPv4 NAT gives the same hint as the global IPv6 prefix seen for + IPv6 traffic. + + While IPv4 NAT may obfuscate to an external observer which internal + devices traffic is sourced from, IPv6, even with use of privacy + addresses [RFC4941], adds additional exposure of which traffic is + sourced from the same internal device through use of the same IPv6 + source address for a period of time. + +3.5. Routing Functionality + + Routing functionality is required when there are multiple routers + deployed within the internal home network. This functionality could + be as simple as the current 'default route is up' model of IPv4 NAT, + + + + +Chown, et al. Informational [Page 28] + +RFC 7368 IPv6 Home Networking October 2014 + + + or more likely, it would involve running an appropriate routing + protocol. + + A mechanism is required to discover which router(s) in the homenet is + providing the CE router function. Borders may include but are not + limited to the interface to the upstream ISP, a gateway device to a + separate home network such as an LLN network, or a gateway to a guest + or private corporate extension network. In some cases, there may be + no border present, which may, for example, occur before an upstream + connection has been established. + + The routing environment should be self-configuring, as discussed + previously. The homenet self-configuration process and the routing + protocol must interact in a predictable manner, especially during + startup and reconvergence. The border discovery functionality and + other self-configuration functionality may be integrated into the + routing protocol itself but may also be imported via a separate + discovery mechanism. + + It is preferable that configuration information is distributed and + synchronised within the homenet by a separate configuration protocol. + + The homenet routing protocol should be based on a previously deployed + protocol that has been shown to be reliable and robust. This does + not preclude the selection of a newer protocol for which a high- + quality open source implementation becomes available. The resulting + code must support lightweight implementations and be suitable for + incorporation into consumer devices, where both fixed and temporary + storage and processing power are at a premium. + + At most, one unicast and one multicast routing protocol should be in + use at a given time in a given homenet. In some simple topologies, + no routing protocol may be needed. If more than one routing protocol + is supported by routers in a given homenet, then a mechanism is + required to ensure that all routers in that homenet use the same + protocol. + + The homenet architecture is IPv6-only. In practice, dual-stack + homenets are still likely for the foreseeable future, as described in + Section 3.2.3. Whilst support for IPv4 and other address families + may therefore be beneficial, it is not an explicit requirement to + carry the routing information in the same routing protocol. + + Multiple types of physical interfaces must be accounted for in the + homenet routing topology. Technologies such as Ethernet, Wi-Fi, + Multimedia over Coax Alliance (MoCA), etc., must be capable of + coexisting in the same environment and should be treated as part of + any routed deployment. The inclusion of physical-layer + + + +Chown, et al. Informational [Page 29] + +RFC 7368 IPv6 Home Networking October 2014 + + + characteristics in path computation should be considered for + optimising communication in the homenet. + +3.5.1. Unicast Routing within the Homenet + + The role of the unicast routing protocol is to provide good enough + end-to-end connectivity often enough, where good/often enough is + defined by user expectations. + + Due to the use of a variety of diverse underlying link technologies, + path selection in a homenet may benefit from being more refined than + minimising hop count. It may also be beneficial for traffic to use + multiple paths to a given destination within the homenet where + available rather than just a single best path. + + Minimising convergence time should be a goal in any routed + environment. It is reasonable to assume that convergence time should + not be significantly longer than network outages users are accustomed + to should their CE router reboot. + + The homenet architecture is agnostic as to the choice of underlying + routing technology, e.g., link state versus Bellman-Ford. + + The routing protocol should support the generic use of multiple + customer Internet connections and the concurrent use of multiple + delegated prefixes. A routing protocol that can make routing + decisions based on source and destination addresses is thus highly + desirable, to avoid problems with upstream ISP ingress filtering as + described in BCP 38. Multihoming support may also include load + balancing to multiple providers and failover from a primary to a + backup link when available. The protocol should not require upstream + ISP connectivity to be established to continue routing within the + homenet. + + The homenet architecture is agnostic on a minimum hop count that has + to be supported by the routing protocol. The architecture should, + however, be scalable to other scenarios where homenet technology may + be deployed, which may include small office and small enterprise + sites. To allow for such cases, it would be desirable that the + architecture is scalable to higher hop counts and to larger numbers + of routers than would be typical in a true home network. + + At the time of writing, link-layer networking technology is poised to + become more heterogeneous, as networks begin to employ both + traditional Ethernet technology and link layers designed for LLNs, + such as those used for certain types of sensor devices. + + + + + +Chown, et al. Informational [Page 30] + +RFC 7368 IPv6 Home Networking October 2014 + + + Ideally, LLN or other logically separate networks should be able to + exchange routes such that IP traffic may be forwarded among the + networks via gateway routers that interoperate with both the homenet + and any LLNs. Current home deployments use largely different + mechanisms in sensor and basic Internet connectivity networks. IPv6 + virtual machine (VM) solutions may also add additional routing + requirements. + + In this homenet architecture, LLNs and other specialised networks are + considered stub areas of the homenet and are thus not expected to act + as a transit for traffic between more traditional media. + +3.5.2. Unicast Routing at the Homenet Border + + The current practice defined in [RFC7084] would suggest that routing + between the homenet CE router and the service provider router follow + the WAN-side requirements model in [RFC7084], Section 4 (WAN-side + requirements), at least in initial deployments. However, + consideration of whether a routing protocol is used between the + homenet CE router and the service provider router is out of scope of + this document. + +3.5.3. Multicast Support + + It is desirable that, subject to the capacities of devices on certain + media types, multicast routing is supported across the homenet, + including source-specific multicast (SSM) [RFC4607]. + + [RFC4291] requires that any boundary of scope 4 or higher (i.e., + admin-local or higher) be administratively configured. Thus, the + boundary at the homenet-ISP border must be administratively + configured, though that may be triggered by an administrative + function such as DHCP PD. Other multicast forwarding policy borders + may also exist within the homenet, e.g., to/from a guest subnet, + whilst the use of certain link media types may also affect where + specific multicast traffic is forwarded or routed. + + There may be different drivers for multicast to be supported across + the homenet -- for example, + + o for homenet-wide service discovery, should a multicast service + discovery protocol of scope greater than link-local be defined + + o for multicast-based streaming or file-sharing applications + + Where multicast is routed across a homenet, an appropriate multicast + routing protocol is required, one that as per the unicast routing + protocol should be self-configuring. As hinted above, it must be + + + +Chown, et al. Informational [Page 31] + +RFC 7368 IPv6 Home Networking October 2014 + + + possible to scope or filter multicast traffic to avoid it being + flooded to network media where devices cannot reasonably support it. + + A homenet may not only use multicast internally, it may also be a + consumer or provider of external multicast traffic, where the + homenet's ISP supports such multicast operation. This may be + valuable, for example, where live video applications are being + sourced to/from the homenet. + + The multicast environment should support the ability for applications + to pick a unique multicast group to use. + +3.6. Security + + The security of an IPv6 homenet is an important consideration. The + most notable difference to the IPv4 operational model is the removal + of NAT, the introduction of global addressability of devices, and + thus a need to consider whether devices should have global + reachability. Regardless, hosts need to be able to operate securely, + end to end where required, and also be robust against malicious + traffic directed towards them. However, there are other challenges + introduced, e.g., default filtering policies at the borders between + various homenet realms. + +3.6.1. Addressability vs. Reachability + + An IPv6-based home network architecture should embrace the + transparent end-to-end communications model as described in + [RFC2775]. Each device should be globally addressable, and those + addresses must not be altered in transit. However, security + perimeters can be applied to restrict end-to-end communications, and + thus while a host may be globally addressable, it may not be globally + reachable. + + [RFC4864] describes a 'Simple Security' model for IPv6 networks, + whereby stateful perimeter filtering can be applied to control the + reachability of devices in a homenet. RFC 4864 states in Section 4.2 + that "the use of firewalls...is recommended for those that want + boundary protection in addition to host defences." It should be + noted that a 'default deny' filtering approach would effectively + replace the need for IPv4 NAT traversal protocols with a need to use + a signalling protocol to request a firewall hole be opened, e.g., a + protocol such as PCP [RFC6887]. In networks with multiple CE + routers, the signalling would need to handle the cases of flows that + may use one or more exit routers. CE routers would need to be able + to advertise their existence for such protocols. + + + + + +Chown, et al. Informational [Page 32] + +RFC 7368 IPv6 Home Networking October 2014 + + + [RFC6092] expands on RFC 4864, giving a more detailed discussion of + IPv6 perimeter security recommendations, without mandating a 'default + deny' approach. Indeed, RFC 6092 does not enforce a particular mode + of operation, instead stating that CE routers must provide an easily + selected configuration option that permits a 'transparent' mode, thus + ensuring a 'default allow' model is available. + + The topic of whether future home networks as described in this + document should have a 'default deny' or 'default allow' position has + been discussed at length in various IETF meetings without any + consensus being reached on which approach is more appropriate. + Further, the choice of which default to apply may be situational, and + thus this text makes no recommendation on the default setting beyond + what is written on this topic in RFC 6092. We note in Section 3.6.3 + below that the implicit firewall function of an IPv4 NAT is + commonplace today, and thus future CE routers targeted at home + networks should continue to support the option of running in 'default + deny mode', whether or not that is the default setting. + +3.6.2. Filtering at Borders + + It is desirable that there are mechanisms to detect different types + of borders within the homenet, as discussed previously, and further + mechanisms to then apply different types of filtering policies at + those borders, e.g., whether naming and service discovery should pass + a given border. Any such policies should be able to be easily + applied by typical home users, e.g., to give a user in a guest + network access to media services in the home or access to a printer. + Simple mechanisms to apply policy changes, or associations between + devices, will be required. + + There are cases where full internal connectivity may not be + desirable, e.g., in certain utility networking scenarios, or where + filtering is required for policy reasons against a guest network + subnet(s). As a result, some scenarios/models may involve running an + isolated subnet(s) with their own CE routers. In such cases, + connectivity would only be expected within each isolated network + (though traffic may potentially pass between them via external + providers). + + LLNs provide another example of where there may be secure perimeters + inside the homenet. Constrained LLN nodes may implement network key + security but may depend on access policies enforced by the LLN border + router. + + Considerations for differentiating neighbouring homenets are + discussed in Section 3.3.1. + + + + +Chown, et al. Informational [Page 33] + +RFC 7368 IPv6 Home Networking October 2014 + + +3.6.3. Partial Effectiveness of NAT and Firewalls + + Security by way of obscurity (address translation) or through + firewalls (filtering) is at best only partially effective. The very + poor security track record of home computers, home networking, and + business PC computers and networking is testimony to this. A + security compromise behind the firewall of any device exposes all + others, making an entire network that relies on obscurity or a + firewall as vulnerable as the most insecure device on the private + side of the network. + + However, given current evidence of home network products with very + poor default device security, putting a firewall in place does + provide some level of protection. The use of firewalls today, + whether a good practice or not, is common practice, and the + capability to afford protection via a 'default deny' setting, even if + marginally effective, should not be lost. Thus, while it is highly + desirable that all hosts in a homenet be adequately protected by + built-in security functions, it should also be assumed that all CE + routers will continue to support appropriate perimeter defence + functions, as per [RFC7084]. + +3.6.4. Exfiltration Concerns + + As homenets become more complex, with more devices, and with service + discovery potentially enabled across the whole home, there are + potential concerns over the leakage of information should devices use + discovery protocols to gather information and report it to equipment + vendors or application service providers. + + While it is not clear how such exfiltration could be easily avoided, + the threat should be recognised, be it from a new piece of hardware + or some 'app' installed on a personal device. + +3.6.5. Device Capabilities + + In terms of the devices, homenet hosts should implement their own + security policies in accordance to their computing capabilities. + They should have the means to request transparent communications that + can be initiated to them through security filters in the homenet, for + either all ports or specific services. Users should have simple + methods to associate devices to services that they wish to operate + transparently through (CE router) borders. + + + + + + + + +Chown, et al. Informational [Page 34] + +RFC 7368 IPv6 Home Networking October 2014 + + +3.6.6. ULAs as a Hint of Connection Origin + + As noted in Section 3.6, if appropriate filtering is in place on the + CE router(s), as mandated by requirement S-2 in RFC 7084, a ULA + source address may be taken as an indication of locally sourced + traffic. This indication could then be used with security settings + to designate between which nodes a particular application is allowed + to communicate, provided ULA address space is filtered appropriately + at the boundary of the realm. + +3.7. Naming and Service Discovery + + The homenet requires devices to be able to determine and use unique + names by which they can be accessed on the network and that are not + used by other devices on the network. Users and devices will need to + be able to discover devices and services available on the network, + e.g., media servers, printers, displays, or specific home automation + devices. Thus, naming and service discovery must be supported in the + homenet, and given the nature of typical home network users, the + service(s) providing this function must as far as possible support + unmanaged operation. + + The naming system will be required to work internally or externally, + whether the user is within or outside of the homenet, i.e., the user + should be able to refer to devices by name, and potentially connect + to them, wherever they may be. The most natural way to think about + such naming and service discovery is to enable it to work across the + entire homenet residence (site), disregarding technical borders such + as subnets but respecting policy borders such as those between guest + and other internal network realms. Remote access may be desired by + the homenet residents while travelling but also potentially by + manufacturers or other 'benevolent' third parties. + +3.7.1. Discovering Services + + Users will typically perform service discovery through graphical user + interfaces (GUIs) that allow them to browse services on their network + in an appropriate and intuitive way. Devices may also need to + discover other devices, without any user intervention or choice. + Either way, such interfaces are beyond the scope of this document, + but the interface should have an appropriate application programming + interface (API) for the discovery to be performed. + + Such interfaces may also typically hide the local domain name element + from users, especially where only one name space is available. + However, as we discuss below, in some cases the ability to discover + available domains may be useful. + + + + +Chown, et al. Informational [Page 35] + +RFC 7368 IPv6 Home Networking October 2014 + + + We note that current zero-configuration service discovery protocols + are generally aimed at single subnets. There is thus a choice to + make for multi-subnet homenets as to whether such protocols should be + proxied or extended to operate across a whole homenet. In this + context, that may mean bridging a link-local method, taking care to + avoid packets entering looping paths, or extending the scope of + multicast traffic used for the purpose. It may mean that some proxy + or hybrid service is utilised, perhaps co-resident on the CE router. + Or, it may be that a new approach is preferable, e.g., flooding + information around the homenet as attributes within the routing + protocol (which could allow per-prefix configuration). However, we + should prefer approaches that are backward compatible and allow + current implementations to continue to be used. Note that this + document does not mandate a particular solution; rather, it expresses + the principles that should be used for a homenet naming and service + discovery environment. + + One of the primary challenges facing service discovery today is lack + of interoperability due to the ever increasing number of service + discovery protocols available. While it is conceivable for consumer + devices to support multiple discovery protocols, this is clearly not + the most efficient use of network and computational resources. One + goal of the homenet architecture should be a path to service + discovery protocol interoperability through either a standards-based + translation scheme, hooks into current protocols to allow some form + of communication among discovery protocols, extensions to support a + central service repository in the homenet, or simply convergence + towards a unified protocol suite. + +3.7.2. Assigning Names to Devices + + Given the large number of devices that may be networked in the + future, devices should have a means to generate their own unique + names within a homenet and to detect clashes should they arise, e.g., + where a second device of the same type/vendor as an existing device + with the same default name is deployed or where a new subnet is added + to the homenet that already has a device of the same name. It is + expected that a device should have a fixed name while within the + scope of the homenet. + + Users will also want simple ways to (re)name devices, again most + likely through an appropriate and intuitive interface that is beyond + the scope of this document. Note that the name a user assigns to a + device may be a label that is stored on the device as an attribute of + the device, and it may be distinct from the name used in a name + service, e.g., 'Study Laser Printer' as opposed to + printer2.<somedomain>. + + + + +Chown, et al. Informational [Page 36] + +RFC 7368 IPv6 Home Networking October 2014 + + +3.7.3. The Homenet Name Service + + The homenet name service should support both lookups and discovery. + A lookup would operate via a direct query to a known service, while + discovery may use multicast messages or a service where applications + register in order to be found. + + It is highly desirable that the homenet name service must at the very + least coexist with the Internet name service. There should also be a + bias towards proven, existing solutions. The strong implication is + thus that the homenet service is DNS based, or DNS compatible. There + are naming protocols that are designed to be configured and operate + Internet-wide, like unicast-based DNS, but also protocols that are + designed for zero-configuration local environments, like Multicast + DNS (mDNS) [RFC6762]. + + When DNS is used as the homenet name service, it typically includes + both a resolving service and an authoritative service. The + authoritative service hosts the homenet-related zone. One approach + when provisioning such a name service, which is designed to + facilitate name resolution from the global Internet, is to run an + authoritative name service on the CE router and a secondary + authoritative name service provided by the ISP or perhaps an external + third party. + + Where zero-configuration name services are used, it is desirable that + these can also coexist with the Internet name service. In + particular, where the homenet is using a global name space, it is + desirable that devices have the ability, where desired, to add + entries to that name space. There should also be a mechanism for + such entries to be removed or expired from the global name space. + + To protect against attacks such as cache poisoning, where an attacker + is able to insert a bogus DNS entry in the local cache, it is + desirable to support appropriate name service security methods, + including DNS Security Extensions (DNSSEC) [RFC4033], on both the + authoritative server and the resolver sides. Where DNS is used, the + homenet router or naming service must not prevent DNSSEC from + operating. + + While this document does not specify hardware requirements, it is + worth noting briefly here that, e.g., in support of DNSSEC, + appropriate homenet devices should have good random number generation + capability, and future homenet specifications should indicate where + high-quality random number generators, i.e., with decent entropy, are + needed. + + + + + +Chown, et al. Informational [Page 37] + +RFC 7368 IPv6 Home Networking October 2014 + + + Finally, the impact of a change in the CE router must be considered. + It would be desirable to retain any relevant state (configuration) + that was held in the old CE router. This might imply that state + information should be distributed in the homenet, to be recoverable + by/to the new CE router, or to the homenet's ISP or a third-party + externally provided service by some means. + +3.7.4. Name Spaces + + If access to homenet devices is required remotely from anywhere on + the Internet, then at least one globally unique name space is + required, though the use of multiple name spaces should not be + precluded. One approach is that the name space(s) used for the + homenet would be served authoritatively by the homenet, most likely + by a server resident on the CE router. Such name spaces may be + acquired by the user or provided/generated by their ISP or an + alternative externally provided service. It is likely that the + default case is that a homenet will use a global domain provided by + the ISP, but advanced users wishing to use a name space that is + independent of their provider in the longer term should be able to + acquire and use their own domain name. For users wanting to use + their own independent domain names, such services are already + available. + + Devices may also be assigned different names in different name + spaces, e.g., by third parties who may manage systems or devices in + the homenet on behalf of the resident(s). Remote management of the + homenet is out of scope of this document. + + If, however, a global name space is not available, the homenet will + need to pick and use a local name space, which would only have + meaning within the local homenet (i.e., it would not be used for + remote access to the homenet). The .local name space currently has a + special meaning for certain existing protocols that have link-local + scope and is thus not appropriate for multi-subnet home networks. A + different name space is thus required for the homenet. + + One approach for picking a local name space is to use an Ambiguous + Local Qualified Domain Name (ALQDN) space, such as .sitelocal (or an + appropriate name reserved for the purpose). While this is a simple + approach, there is the potential in principle for devices that are + bookmarked somehow by name by an application in one homenet to be + confused with a device with the same name in another homenet. In + practice, however, the underlying service discovery protocols should + be capable of handling moving to a network where a new device is + using the same name as a device used previously in another homenet. + + + + + +Chown, et al. Informational [Page 38] + +RFC 7368 IPv6 Home Networking October 2014 + + + An alternative approach for a local name space would be to use a + Unique Locally Qualified Domain Name (ULQDN) space such as + .<UniqueString>.sitelocal. The <UniqueString> could be generated in + a variety of ways, one potentially being based on the local /48 ULA + prefix being used across the homenet. Such a <UniqueString> should + survive a cold restart, i.e., be consistent after a network power- + down, or if a value is not set on startup, the CE router or device + running the name service should generate a default value. It would + be desirable for the homenet user to be able to override the + <UniqueString> with a value of their choice, but that would increase + the likelihood of a name conflict. Any generated <UniqueString> + should not be predictable; thus, adding a salt/hash function would be + desirable. + + In the (likely) event that the homenet is accessible from outside the + homenet (using the global name space), it is vital that the homenet + name space follow the rules and conventions of the global name space. + In this mode of operation, names in the homenet (including those + automatically generated by devices) must be usable as labels in the + global name space. [RFC5890] describes considerations for + Internationalizing Domain Names in Applications (IDNA). + + Also, with the introduction of new 'dotless' top-level domains, there + is also potential for ambiguity between, for example, a local host + called 'computer' and (if it is registered) a .computer Generic Top + Level Domain (gTLD). Thus, qualified names should always be used, + whether these are exposed to the user or not. The IAB has issued a + statement that explains why dotless domains should be considered + harmful [IABdotless]. + + There may be use cases where different name spaces may be desired for + either different realms in the homenet or segmentation of a single + name space within the homenet. Thus, hierarchical name space + management is likely to be required. There should also be nothing to + prevent an individual device(s) from being independently registered + in external name spaces. + + It may be the case that if there are two or more CE routers serving + the home network, if each has a name space delegated from a different + ISP, there is the potential for devices in the home to have multiple + fully qualified names under multiple domains. + + Where a user is in a remote network wishing to access devices in + their home network, there may be a requirement to consider the domain + search order presented where multiple associated name spaces exist. + This also implies that a domain discovery function is desirable. + + + + + +Chown, et al. Informational [Page 39] + +RFC 7368 IPv6 Home Networking October 2014 + + + It may be the case that not all devices in the homenet are made + available by name via an Internet name space, and that a 'split view' + (as described in [RFC6950], Section 4) is preferred for certain + devices, whereby devices inside the homenet see different DNS + responses to those outside. + + Finally, this document makes no assumption about the presence or + omission of a reverse lookup service. There is an argument that it + may be useful for presenting logging information to users with + meaningful device names rather than literal addresses. There are + also some services, most notably email mail exchangers, where some + operators have chosen to require a valid reverse lookup before + accepting connections. + +3.7.5. Independent Operation + + Name resolution and service discovery for reachable devices must + continue to function if the local network is disconnected from the + global Internet, e.g., a local media server should still be available + even if the Internet link is down for an extended period. This + implies that the local network should also be able to perform a + complete restart in the absence of external connectivity and have + local naming and service discovery operate correctly. + + As described above, the approach of a local authoritative name + service with a cache would allow local operation for sustained ISP + outages. + + Having an independent local trust anchor is desirable, to support + secure exchanges should external connectivity be unavailable. + + A change in ISP should not affect local naming and service discovery. + However, if the homenet uses a global name space provided by the ISP, + then this will obviously have an impact if the user changes their + network provider. + +3.7.6. Considerations for LLNs + + In some parts of the homenet, in particular LLNs or any devices where + battery power is used, devices may be sleeping, in which case a proxy + for such nodes may be required that could respond (for example) to + multicast service discovery requests. Those same devices or parts of + the network may have less capacity for multicast traffic that may be + flooded from other parts of the network. In general, message + utilisation should be efficient considering the network technologies + and constrained devices that the service may need to operate over. + + + + + +Chown, et al. Informational [Page 40] + +RFC 7368 IPv6 Home Networking October 2014 + + + There are efforts underway to determine naming and discovery + solutions for use by the Constrained Application Protocol (CoAP) + [RFC7252] in LLN networks. These are outside the scope of this + document. + +3.7.7. DNS Resolver Discovery + + Automatic discovery of a name service to allow client devices in the + homenet to resolve external domains on the Internet is required, and + such discovery must support clients that may be a number of router + hops away from the name service. Similarly, it may be desirable to + convey any DNS domain search list that may be in effect for the + homenet. + +3.7.8. Devices Roaming to/from the Homenet + + It is likely that some devices that have registered names within the + homenet Internet name space and that are mobile will attach to the + Internet at other locations and acquire an IP address at those + locations. Devices may move between different homenets. In such + cases, it is desirable that devices may be accessed by the same name + as is used in their home network. + + Solutions to this problem are not discussed in this document. They + may include the use of Mobile IPv6 or Dynamic DNS -- either of which + would put additional requirements on the homenet -- or establishment + of a (VPN) tunnel to a server in the home network. + +3.8. Other Considerations + + This section discusses two other considerations for home networking + that the architecture should not preclude but that this text is + neutral towards. + +3.8.1. Quality of Service + + Support for Quality of Service (QoS) in a multi-service homenet may + be a requirement, e.g., for a critical system (perhaps health care + related) or for differentiation between different types of traffic + (file sharing, cloud storage, live streaming, Voice over IP (VoIP), + etc). Different link media types may have different such properties + or capabilities. + + However, homenet scenarios should require no new QoS protocols. A + Diffserv [RFC2475] approach with a small number of predefined traffic + classes may generally be sufficient, though at present there is + little experience of QoS deployment in home networks. It is likely + that QoS, or traffic prioritisation, methods will be required at the + + + +Chown, et al. Informational [Page 41] + +RFC 7368 IPv6 Home Networking October 2014 + + + CE router and potentially around boundaries between different link + media types (where, for example, some traffic may simply not be + appropriate for some media and need to be dropped to avoid + overloading the constrained media). + + There may also be complementary mechanisms that could be beneficial + to application performance and behaviour in the homenet domain, such + as ensuring proper buffering algorithms are used as described in + [Gettys11]. + +3.8.2. Operations and Management + + In this section, we briefly review some initial considerations for + operations and management in the type of homenet described in this + document. It is expected that a separate document will define an + appropriate operations and management framework for such homenets. + + As described in this document, the homenet should have the general + goal of being self-organising and self-configuring from the network- + layer perspective, e.g., prefixes should be able to be assigned to + router interfaces. Further, applications running on devices should + be able to use zero-configuration service discovery protocols to + discover services of interest to the home user. In contrast, a home + user would not be expected, for example, to have to assign prefixes + to links or manage the DNS entries for the home network. Such expert + operation should not be precluded, but it is not the norm. + + The user may still be required to, or wish to, perform some + configuration of the network and the devices on it. Examples might + include entering a security key to enable access to their wireless + network or choosing to give a 'friendly name' to a device presented + to them through service discovery. Configuration of link- and + application-layer services is out of scope of this architectural + principles document but is likely to be required in an operational + homenet. + + While not being expected to actively configure the networking + elements of their homenet, users may be interested in being able to + view the status of their networks and the devices connected to it, in + which case appropriate network monitoring protocols will be required + to allow them to view their network, and its status, e.g., via a web + interface or equivalent. While the user may not understand how the + network operates, it is reasonable to assume they are interested in + understanding what faults or problems may exist on it. Such + monitoring may extend to other devices on the network, e.g., storage + devices or web cameras, but such devices are beyond the scope of this + document. + + + + +Chown, et al. Informational [Page 42] + +RFC 7368 IPv6 Home Networking October 2014 + + + It may also be the case that an ISP, or a third party, might wish to + offer a remote management service for the homenet on behalf of the + user, or to be able to assist the user in the event of some problem + they are experiencing, in which case appropriate management and + monitoring protocols would be required. + + Specifying the required protocols to facilitate homenet management + and monitoring is out of scope of this document. As stated above, it + is expected that a separate document will be produced to describe the + operations and management framework for the types of home networks + presented in this document. + + As a final point, we note that it is desirable that all network + management and monitoring functions should be available over IPv6 + transport, even where the homenet is dual stack. + +3.9. Implementing the Architecture on IPv6 + + This architecture text encourages reuse of existing protocols. Thus, + the necessary mechanisms are largely already part of the IPv6 + protocol set and common implementations, though there are some + exceptions. + + For automatic routing, it is expected that solutions can be found + based on existing protocols. Some relatively smaller updates are + likely to be required, e.g., a new mechanism may be needed in order + to turn a selected protocol on by default, or a mechanism may be + required to automatically assign prefixes to links within the + homenet. + + Some functionality, if required by the architecture, may need more + significant changes or require development of new protocols, e.g., + support for multihoming with multiple exit routers would likely + require extensions to support source and destination address-based + routing within the homenet. + + Some protocol changes are, however, required in the architecture, + e.g., for name resolution and service discovery, extensions to + existing zero-configuration link-local name resolution protocols are + needed to enable them to work across subnets, within the scope of the + home network site. + + Some of the hardest problems in developing solutions for home + networking IPv6 architectures include discovering the right borders + where the 'home' domain ends and the service provider domain begins, + deciding whether some of the necessary discovery mechanism extensions + should affect only the network infrastructure or also hosts, and the + + + + +Chown, et al. Informational [Page 43] + +RFC 7368 IPv6 Home Networking October 2014 + + + ability to turn on routing, prefix delegation, and other functions in + a backwards-compatible manner. + +4. Conclusions + + This text defines principles and requirements for a homenet + architecture. The principles and requirements documented here should + be observed by any future texts describing homenet protocols for + routing, prefix management, security, naming, or service discovery. + +5. Security Considerations + + Security considerations for the homenet architecture are discussed in + Section 3.6 above. + +6. References + +6.1. Normative References + + [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 + (IPv6) Specification", RFC 2460, December 1998, + <http://www.rfc-editor.org/info/rfc2460>. + + [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic + Host Configuration Protocol (DHCP) version 6", RFC 3633, + December 2003, <http://www.rfc-editor.org/info/rfc3633>. + + [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast + Addresses", RFC 4193, October 2005, + <http://www.rfc-editor.org/info/rfc4193>. + + [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing + Architecture", RFC 4291, February 2006, + <http://www.rfc-editor.org/info/rfc4291>. + +6.2. Informative References + + [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and + E. Lear, "Address Allocation for Private Internets", BCP + 5, RFC 1918, February 1996, + <http://www.rfc-editor.org/info/rfc1918>. + + [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., + and W. Weiss, "An Architecture for Differentiated + Services", RFC 2475, December 1998, + <http://www.rfc-editor.org/info/rfc2475>. + + + + + +Chown, et al. Informational [Page 44] + +RFC 7368 IPv6 Home Networking October 2014 + + + [RFC2775] Carpenter, B., "Internet Transparency", RFC 2775, February + 2000, <http://www.rfc-editor.org/info/rfc2775>. + + [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: + Defeating Denial of Service Attacks which employ IP Source + Address Spoofing", BCP 38, RFC 2827, May 2000, + <http://www.rfc-editor.org/info/rfc2827>. + + [RFC3002] Mitzel, D., "Overview of 2000 IAB Wireless Internetworking + Workshop", RFC 3002, December 2000, + <http://www.rfc-editor.org/info/rfc3002>. + + [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network + Address Translator (Traditional NAT)", RFC 3022, January + 2001, <http://www.rfc-editor.org/info/rfc3022>. + + [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. + Rose, "DNS Security Introduction and Requirements", RFC + 4033, March 2005, + <http://www.rfc-editor.org/info/rfc4033>. + + [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and + More-Specific Routes", RFC 4191, November 2005, + <http://www.rfc-editor.org/info/rfc4191>. + + [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for + Renumbering an IPv6 Network without a Flag Day", RFC 4192, + September 2005, <http://www.rfc-editor.org/info/rfc4192>. + + [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for + IP", RFC 4607, August 2006, + <http://www.rfc-editor.org/info/rfc4607>. + + [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless + Address Autoconfiguration", RFC 4862, September 2007, + <http://www.rfc-editor.org/info/rfc4862>. + + [RFC4864] Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and + E. Klein, "Local Network Protection for IPv6", RFC 4864, + May 2007, <http://www.rfc-editor.org/info/rfc4864>. + + [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy + Extensions for Stateless Address Autoconfiguration in + IPv6", RFC 4941, September 2007, + <http://www.rfc-editor.org/info/rfc4941>. + + + + + + +Chown, et al. Informational [Page 45] + +RFC 7368 IPv6 Home Networking October 2014 + + + [RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming + Shim Protocol for IPv6", RFC 5533, June 2009, + <http://www.rfc-editor.org/info/rfc5533>. + + [RFC5890] Klensin, J., "Internationalized Domain Names for + Applications (IDNA): Definitions and Document Framework", + RFC 5890, August 2010, + <http://www.rfc-editor.org/info/rfc5890>. + + [RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4 + Infrastructures (6rd) -- Protocol Specification", RFC + 5969, August 2010, + <http://www.rfc-editor.org/info/rfc5969>. + + [RFC6092] Woodyatt, J., "Recommended Simple Security Capabilities in + Customer Premises Equipment (CPE) for Providing + Residential IPv6 Internet Service", RFC 6092, January + 2011, <http://www.rfc-editor.org/info/rfc6092>. + + [RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for + IPv4/IPv6 Translation", RFC 6144, April 2011, + <http://www.rfc-editor.org/info/rfc6144>. + + [RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation + Algorithm", RFC 6145, April 2011, + <http://www.rfc-editor.org/info/rfc6145>. + + [RFC6177] Narten, T., Huston, G., and L. Roberts, "IPv6 Address + Assignment to End Sites", BCP 157, RFC 6177, March 2011, + <http://www.rfc-editor.org/info/rfc6177>. + + [RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B., and O. + Troan, "Basic Requirements for IPv6 Customer Edge + Routers", RFC 6204, April 2011, + <http://www.rfc-editor.org/info/rfc6204>. + + [RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix + Translation", RFC 6296, June 2011, + <http://www.rfc-editor.org/info/rfc6296>. + + [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- + Stack Lite Broadband Deployments Following IPv4 + Exhaustion", RFC 6333, August 2011, + <http://www.rfc-editor.org/info/rfc6333>. + + [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with + Dual-Stack Hosts", RFC 6555, April 2012, + <http://www.rfc-editor.org/info/rfc6555>. + + + +Chown, et al. Informational [Page 46] + +RFC 7368 IPv6 Home Networking October 2014 + + + [RFC6724] Thaler, D., Draves, R., Matsumoto, A., and T. Chown, + "Default Address Selection for Internet Protocol Version 6 + (IPv6)", RFC 6724, September 2012, + <http://www.rfc-editor.org/info/rfc6724>. + + [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, + February 2013, <http://www.rfc-editor.org/info/rfc6762>. + + [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, + "TCP Extensions for Multipath Operation with Multiple + Addresses", RFC 6824, January 2013, + <http://www.rfc-editor.org/info/rfc6824>. + + [RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. + Selkirk, "Port Control Protocol (PCP)", RFC 6887, April + 2013, <http://www.rfc-editor.org/info/rfc6887>. + + [RFC6950] Peterson, J., Kolkman, O., Tschofenig, H., and B. Aboba, + "Architectural Considerations on Application Features in + the DNS", RFC 6950, October 2013, + <http://www.rfc-editor.org/info/rfc6950>. + + [RFC7084] Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic + Requirements for IPv6 Customer Edge Routers", RFC 7084, + November 2013, <http://www.rfc-editor.org/info/rfc7084>. + + [RFC7157] Troan, O., Miles, D., Matsushima, S., Okimoto, T., and D. + Wing, "IPv6 Multihoming without Network Address + Translation", RFC 7157, March 2014, + <http://www.rfc-editor.org/info/rfc7157>. + + [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained + Application Protocol (CoAP)", RFC 7252, June 2014, + <http://www.rfc-editor.org/info/rfc7252>. + + [IABdotless] + IAB, "IAB Statement: Dotless Domains Considered Harmful", + February 2013, <http://www.iab.org/documents/ + correspondence-reports-documents/2013-2/ + iab-statement-dotless-domains-considered-harmful>. + + [Gettys11] + Gettys, J., "Bufferbloat: Dark Buffers in the Internet", + March 2011, + <http://www.ietf.org/proceedings/80/slides/tsvarea-1.pdf>. + + + + + + +Chown, et al. Informational [Page 47] + +RFC 7368 IPv6 Home Networking October 2014 + + +Acknowledgments + + The authors would like to thank Mikael Abrahamsson, Aamer Akhter, + Mark Andrews, Dmitry Anipko, Ran Atkinson, Fred Baker, Ray Bellis, + Teco Boot, John Brzozowski, Cameron Byrne, Brian Carpenter, Stuart + Cheshire, Julius Chroboczek, Lorenzo Colitti, Robert Cragie, Elwyn + Davies, Ralph Droms, Lars Eggert, Jim Gettys, Olafur Gudmundsson, + Wassim Haddad, Joel M. Halpern, David Harrington, Lee Howard, Ray + Hunter, Joel Jaeggli, Heather Kirksey, Ted Lemon, Acee Lindem, Kerry + Lynn, Daniel Migault, Erik Nordmark, Michael Richardson, Mattia + Rossi, Barbara Stark, Sander Steffann, Markus Stenberg, Don Sturek, + Andrew Sullivan, Dave Taht, Dave Thaler, Michael Thomas, Mark + Townsley, JP Vasseur, Curtis Villamizar, Russ White, Dan Wing, and + James Woodyatt for their comments and contributions within homenet WG + meetings and on the WG mailing list. An acknowledgment generally + means that a person's text made it into the document or was helpful + in clarifying or reinforcing an aspect of the document. It does not + imply that each contributor agrees with every point in the document. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Chown, et al. Informational [Page 48] + +RFC 7368 IPv6 Home Networking October 2014 + + +Authors' Addresses + + Tim Chown (editor) + University of Southampton + Highfield + Southampton, Hampshire SO17 1BJ + United Kingdom + + EMail: tjc@ecs.soton.ac.uk + + + Jari Arkko + Ericsson + Jorvas 02420 + Finland + + EMail: jari.arkko@piuha.net + + + Anders Brandt + Sigma Designs + Emdrupvej 26A, 1 + Copenhagen DK-2100 + Denmark + + EMail: anders_brandt@sigmadesigns.com + + + Ole Troan + Cisco Systems, Inc. + Philip Pedersensvei 1 + Lysaker, N-1325 + Norway + + EMail: ot@cisco.com + + + Jason Weil + Time Warner Cable + 13820 Sunrise Valley Drive + Herndon, VA 20171 + United States + + EMail: jason.weil@twcable.com + + + + + + + +Chown, et al. Informational [Page 49] + |