Network Working Group T.J. Chown, Ed.
Internet-Draft University of Southampton
Intended status: Informational J. Arkko
Expires: December 31, 2012 Ericsson
A. Brandt
Sigma Designs
O. Troan
Cisco Systems, Inc.
J. Weil
Time Warner Cable
July 2012

Home Networking Architecture for IPv6


This text describes evolving networking technology within increasingly large residential home networks. The goal of this document is to define an architecture for IPv6-based home networking, while describing the associated principles, considerations and requirements. The text briefly highlights the 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

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This Internet-Draft will expire on December 31, 2012.

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Table of Contents

1. Introduction

This document focuses on evolving networking technology within increasingly large residential home networks and the associated challenges with their deployment and operation. There is a growing trend in home networking for the proliferation of networking technology in 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, others to the introduction of specialised networks for home automation and sensors.

While at the time of writing some complex home network topologies exist, most operate based on IPv4, employ solutions that we would like to avoid such as (cascaded) network address translation (NAT), or require expert assistance to set up. In IPv6 home networks, there are likely to be scenarios where internal routing is required, for example to support private and guest networks, in which case such networks may use increasing numbers of subnets, and require methods for IPv6 prefixes to be delegated to those subnets. The assumption of this document is that the homenet is as far as possible self-organising and self-configuring, and is thus not pro-actively managed 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 a better result than if the IETF had not given this specific guidance. The 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 can not be affected by new recommendations. 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 architecture document proposes a baseline homenet architecture, based on 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.

[RFC6204] defines basic requirements for customer edge routers (CERs). The scope of this text is the internal homenet, and thus specific features on the CER are out of scope for this text. While the network may be dual-stack or IPv6-only, the definition of specific transition tools on the CER, as introduced in RFC 6204-bis [I-D.ietf-v6ops-6204bis] with DS-Lite [RFC6333] and 6rd [RFC5969], are considered issues for that RFC, and are thus also out of scope of this text.

1.1. Terminology and Abbreviations

In this section we define terminology and abbreviations used throughout the text.

2. Effects of IPv6 on Home Networking

Service providers are deploying IPv6, content is becoming available on IPv6 (accelerated recently by the World IPv6 Launch event) and support for IPv6 is increasingly available in devices and software used in the home. While IPv6 resembles IPv4 in many ways, it changes address allocation principles, making multi-addressing the norm, and allowing direct IP addressability of home networking devices from the Internet. This section presents an overview of some of the key implications of the introduction of IPv6 for home networking, that are simultaneously both promising and problematic.

2.1. Multiple subnets and routers

The introduction of IPv6 for home networking enables the potential for every home network to be delegated enough address space to provision globally unique prefixes for each subnet in the home. Such subnetting is not common practice in existing IPv4 homenets, but is very likely to become increasingly standard in future IPv6 homenets.

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 building control or corporate extensions 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 much lower capacity links thus becomes an important topic.

Documents that provide some more specific background and depth on this topic include: [I-D.herbst-v6ops-cpeenhancements], [I-D.baker-fun-multi-router], and [I-D.baker-fun-routing-class].

The addition of routing between subnets raises the issue of how to extend mechanisms such as service discovery which currently rely on link-local addressing to limit scope. There are two broad choices; extend existing protocols to work across the scope of the homenet, or introduce proxies for existing link-layer protocols. This topic is discussed later in the document.

There will also be the need to discover which routers in the homenet are the border router(s) by an appropriate mechanism. Here, there are a number of choices. These include an appropriate service discovery protocol, or the use of a well-known name, resolved by some local name service. Both might have to deal with handling more than one router responding in multihomed environments.

2.2. Global addressability and elimination of NAT

Current IPv4 home networks typically receive a single global IPv4 address from their ISP and use NAT with private [RFC1918] addresses for devices within the network. An IPv6 home network removes the need to use NAT given the ISP offers a sufficiently large globally unique IPv6 prefix to the homenet, allowing every device on every link to be assigned a globally unique IPv6 address.

The end-to-end communication that is potentially enabled with IPv6 is on the one hand an incredible opportunity for innovation and simpler network operation, but it is also a concern as it exposes nodes in the internal networks to receipt of otherwise unwanted traffic from the Internet. There may thus be an expectation of improved host security to compensate for this, at least in general networked devices, but it must be noted that many devices may also (for example) ship with default settings that make them readily vulnerable to compromise by external attackers if globally accessible, or may simply not have robustness designed-in because it was either assumed such devices would only be used on private networks or the device itself doesn't have the computing power to apply the necessary security methods.

IPv6 networks may or may not have filters applied at their borders, i.e. at the homenet CER. [RFC4864], [RFC6092] and [I-D.vyncke-advanced-ipv6-security] discuss such filtering, and the merits of "default allow" against "default deny" policies for external traffic initiated into a homenet. It is important to distinguish between addressability and reachability. While IPv6 offers global addressability through use of globally unique addresses in the home, whether they are globally reachable or not would depend on the firewall or filtering configuration, and not, as is commonly the case with IPv4, the presence or use of NAT.

2.3. Multi-Addressing of devices

In an IPv6 network, devices may acquire multiple addresses, typically at least a link-local address and a globally unique address. They may also have an IPv4 address if the network is dual-stack, a Unique Local Address (ULA) [RFC4193] (see below), and one or more IPv6 Privacy Addresses [RFC4941].

Thus it should 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. Default Address Selection for IPv6 [I-D.ietf-6man-rfc3484bis] provides a solution for this, though it may face problems in the event of multihoming, where nodes will be configured with one address from each upstream ISP prefix. In such cases the presence of upstream ingress filtering requires multi-addressed nodes to select the correct source address to be used for the corresponding uplink, to avoid ISP BCP 38 ingress filtering, but the node may not have the information it needs to make that decision based on addresses alone. We discuss such challenges in the multihoming section later in this document.

2.4. Unique Local Addresses (ULAs)

[RFC4193] defines Unique Local Addresses (ULAs) for IPv6 that may be used to address devices within the scope of a single site. Support for ULAs for IPv6 CERs is described in [RFC6204]. A home network running IPv6 may deploy ULAs for stable communication between devices (on different subnets) within the network where the externally allocated global prefix changes over time (e.g. due to renumbering within the subscriber's ISP) or where external connectivity is temporarily unavailable.

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. It should also be noted that there may be timers on the prefix lease to the homenet, on the internal prefix delegations, and on the Router Advertisements to the hosts. Despite this counter-argument, while setting a network up there may be a period with no connectivity, in which case ULAs would be required for inter-subnet communication. In the case where LLNs are being set up in a new home/deployment, individual LLNs may, at least initially, each use their own /48 ULA prefix.

Default address selection mechanisms should ensure a ULA source address is used to communicate with ULA destination addresses when appropriate, in particular when the ULA destination lies within a /48 ULA prefix known to be used within the same homenet. Note that unlike the IPv4 private RFC 1918 space, the use of ULAs does not imply use of host-based IPv6 NAT, or NPTv6 prefix-based NAT [RFC6296], rather that external communications should use a node's additional globally unique IPv6 source address.

2.5. Naming, and manual configuration of IP addresses

Some IPv4 home networking devices expose IPv4 addresses to users, e.g. the IPv4 address of a home IPv4 CER that may be configured via a web interface. Users should not be expected to enter IPv6 literal addresses in homenet devices or applications, given their much greater length and apparent randomness to a typical home user. While shorter addresses, perhaps ones registered with IANA from ULA-C space [I-D.hain-ipv6-ulac], could be used for specific devices/services, in general it is better to not expose users to real IPv6 addresses. Thus, even for the simplest of functions, simple naming and the associated (ideally zero configuration) discovery of services is imperative for the easy deployment and use of homenet devices and applications.

In a multi-subnet homenet, naming and service discovery should be expected to be capable of operating across the scope of the entire home network, and thus be able to cross subnet boundaries. It should be noted that in IPv4, such services do not generally function across home router NAT boundaries, so this is one area where there is room for improvement in IPv6.

2.6. IPv6-only operation

It is likely that IPv6-only networking will be deployed first in "greenfield" homenet scenarios, 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. Thus, for example, the following requirements are amongst those that should be considered in IPv6-only environments:

The widespread availability of robust solutions to these types of requirements will help accelerate the uptake of IPv6-only homenets.

3. Homenet Architecture

The aim of this architecture text is to outline how to construct advanced IPv6-based home networks involving multiple routers and subnets using standard IPv6 protocols and addressing [RFC2460] [RFC4291]. In this section, we present the elements of such a home networking architecture, with discussion of the associated design principles.

Existing IETF work [RFC6204] defines the "basic" requirements for Customer Edge Routers, while [I-D.ietf-v6ops-6204bis] extends RFC 6204 to describe additional features. The homenet architecture is focused on the internal homenet, rather than the CER(s). 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, given the knowledge level of typical home users. Thus the network should, as far as possible, be self-configuring.

The equipment also needs to be prepared to handle at least

The remainder of this document describes the principles by which a 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 inter-networking mechanisms. This architecture text discusses how this 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 solutions.

3.1.1. Reuse existing protocols

It is desirable to reuse existing protocols where possible, but at the same time to avoid consciously precluding the introduction of new or emerging protocols. A generally conservative approach, giving weight to running 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 backwardly compatible, and forward compatible where changes are made.

3.1.2. Minimise changes to hosts and routers

Where possible, any requirement for changes to hosts and routers should be minimised, though solutions which, for example, incrementally improve with host changes may be acceptable.

3.2. Homenet Topology

In this section we consider homenet topologies, and the principles we may apply in designing an architecture to support as wide a range as possible of such topologies.

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. de-activating 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.

3.2.2. Network topology models

Most IPv4 home network models at the time of writing 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 visitor and private networks.

In general, the models described in [RFC6204] and its successor RFC 6204-bis [I-D.ietf-v6ops-6204bis] should be supported by the IPv6 home networking architecture. The functions resident on the CER itself are, as stated previously, out of scope of this text.

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:

Various forms of multihoming are likely to be more prevalent with IPv6 home networks, as discussed further below. Thus the following properties should also be considered for such networks:

A separate discussion of physical infrastructures for homenets is included in and [I-D.arkko-homenet-physical-standard].

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, rather an indicative one to facilitate the discussion in this text. A: Single ISP, Single CER, Internal routers

Figure 1 shows a 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 a 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 (home users may plug routers together to form arbitrary topologies including loops).

                  +-------+-------+                     \
                  |   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 | |  |
|          | |          | |  |          | |          | |  |
+----------+ +----------+ |  +----------+ +----------+ |  |
                          |        |             |     |  |
                          |     ---+------+------+-----+  |
                          |               | Network B/E   |
                   +------+--------+      |               | End-User
                   |     IPv6      |      |               | networks
                   |   Interior    +------+               |
                   |    Router     |                      |
                   +---+-------+-+-+                      |
       Network C       |       |   Network D              |
 ----+-------------+---+-    --+---+-------------+---     |
     |             |               |             |        |
+----+-----+ +-----+----+     +----+-----+ +-----+----+   |
|IPv6 Host | |IPv6 Host |     | IPv6 Host| |IPv6 Host |   |
|          | |          |     |          | |          |   /
+----------+ +----------+     +----------+ +----------+  /

Figure 1 B: Two ISPs, Two CERs, 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 |  /
|          | |          |     |          | |          | /
+----------+ +----------+     +----------+ +----------+ 

Figure 2

Figure 2 illustrates a multihomed homenet model, where the customer has connectivity via CER1 to ISP A and via CER2 to ISP B. This example shows one shared subnet where IPv6 nodes would potentially be multihomed and receive multiple IPv6 global addresses, 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 CER serves a separate isolated subnet, which is a scenario seen with some IPv4 networks today. C: Two ISPs, One CER, 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 |  /
|          | |          |     |          | |          | /
+----------+ +----------+     +----------+ +----------+ 

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.

In general, while the architecture may focus on likely common topologies, it should not preclude any arbitrary topology from being constructed.

3.2.3. Dual-stack topologies

It is expected that most homenet deployments will for the immediate future 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 there should be bridging if the link layer allows this.

In some cases IPv4 NAT home networks may feature cascaded NATs, which may include cases where NAT routers are included within VMs, or where Internet connection sharing services are used. IPv6 routed versions of such cases will be required. We should thus 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 either take a form where there are 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.

The general multihoming problem is broad, and solutions suggested to date within the IETF may include complex architectures for monitoring connectivity, traffic engineering, identifier-locator separation, connection survivability across multihoming events, and so on. It is thus important that the homenet architecture should as far as possible minimise the complexity of any multihoming support. So we should limit the support to the smallest subset of the overall problem to meet the requirements of the topologies described above. This means that the homenet architecture should not try to make another attempt at solving complex multihoming, and we should prefer to support scenarios for which solutions exist today.

In the general homenet architecture, hosts should be multi-addressed with globally unique prefixes from each ISP they may communicate with or through. An alternative for a homenet would be to deploy NPTv6 [RFC6296] at the CER, with ULAs then typically used internally, but this mode is not considered by this text. If NPTv6 is used, the internal part of the homenet (which is the scope of this text) simply sees only the one (ULA) prefix in use. It should be noted that running NPTv6 has an architectural cost, due to the prefix translation used.

When 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, which would typically include [I-D.ietf-6man-rfc3484bis]. Applications may of course do different things, and this should not be precluded.

For the single CER Network Model C, multihoming may be offered by source routing at the CER. With multiple exit routers, the complexity rises. Given a packet with a source address on the network, the packet must be routed to the proper egress to avoid BCP 38 filtering at an ISP that did not delegate the prefix the address is chosen from. While the packet might not take an optimal path to the correct exit CER, the minimum requirement is that the packet is not dropped. It is of course highly desirable that the packet is routed in the most efficient manner to the correct exit.

There are various potential approaches to this problem, one example being described in [I-D.v6ops-multihoming-without-ipv6nat]. Another is discussed in [I-D.baker-fun-multi-router], which explores support for source routing throughout the homenet. This approach would however likely require relatively significant routing changes to route the packet to the correct exit given the source address. Such changes should preferably be minimised.

There are some other multihoming considerations for homenet scenarios. First, it may be the case that multihoming applies due to an ISP migration from a transition method to a native deployment, e.g. a 6rd [RFC5969] sunset scenario, as discussed in [I-D.townsley-troan-ipv6-ce-transitioning]. Second, one upstream may be a "walled garden", and thus only appropriate to be used 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. While we should not specifically target walled garden multihoming as a principal goal, it should not be precluded.

Host-based methods such as Shim6 [RFC5533] have been defined, but of course require support in the hosts. There are also application-oriented approaches such as Happy Eyeballs [RFC6555]; simplified versions of this are for example already implemented in some commonly-used web browsers. The homenet architecture should not preclude use of such tools should hosts include their support.

3.3. A Self-Organising Network

A home network architecture 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. While the homenet should be self-organising, it should be possible 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 WPA2 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 only one such key is needed for any set of functions, to increase usability for the homenet user.

3.3.1. Homenet realms and borders

The homenet will need to be aware of the extent of its own "site", which will define the borders for ULAs, site scope multicast, service discovery and security policies. The homenet will have one or more borders with external connectivity providers and potentially also have borders within the internal network (e.g. for policy-based reasons). It should be possible to automatically perform border discovery for the different borders. Such borders determine for example the scope of where prefixes, routing information, network traffic, service discovery and naming may be shared. The default internally should be to share everything.

A simple homenet model may just consider three types of realm and the borders between them. For example if the realms are the homenet, the ISP and the visitor network, then the borders will include that from the homenet to the ISP, and that from the homenet to a guest network. Regardless, it should be possible for additional types of realms and borders to be defined, e.g. for some specific Grid or LLN-based network, 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 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.

3.3.2. Largest possible 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 homenet should subdivide itself to the largest possible subnets that can be constructed within the constraints of link layer mechanisms, bridging, physical connectivity, and policy.

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 multiple homenets

It is important that self-configuration with "unintended" devices is avoided. Methods are needed for devices to know whether they are intended to be part of the same homenet site or not. Thus methods to ensure separation between neighbouring homenets are required. This may require use of some unique "secret" for devices/protocols in each homenet. Some existing mechanisms exist to assist home users to associate devices as simply as possible, e.g. "connect" button support.

3.3.4. 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. Homenet Addressing

The IPv6 addressing scheme used within a homenet must conform to the IPv6 addressing architecture [RFC4291]. The homenet will need to adapt to the prefixes made available to it through the prefix delegation method used by its upstream ISP.

3.4.1. Use of ISP-delegated IPv6 prefixes

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. Some ISPs may offer relatively stable prefixes, while others may change the prefix whenever the CER is reset. Some discussion of IPv6 prefix allocation policies is included in [RFC6177] which discusses why, for example, a one-size-fits-all /48 allocation is not desirable. The home network needs to be adaptable to such ISP policies, and thus make no assumptions about the stability of the prefix received from an ISP, or the length of the prefix that may be offered. However, if only a /64 is offered by the ISP, the homenet may be severely constrained, or even unable to function.

The internal operation of the home network should also not depend on the availability of the ISP network at any given time, other than for connectivity to services or systems off the home network. This implies the use of ULAs for stable internal communication, as described in the next section.

In practice, it is expected that ISPs will deliver a relatively stable home prefix to customers. 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 support Provider Independent (PI) addressing for general residential homenets.

When an ISP needs 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 which, 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 is 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.

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, e.g. a /60 rather than a /56. Regardless, it's desirable that homenet protocols support rapid renumbering and that operational processes don't add unnecessary complexity for the renumbering process.

The 6renum WG is studying IPv6 renumbering for enterprise networks. It is not currently targetting homenets, but may produce outputs that are relevant. The introduction of any new homenet protocols should not make any form of renumbering any more complex than it already is.

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 routing between subnets regardless of whether a globally unique ISP-provided prefix is available. It would be expected that ULAs would be used alongside one or more such global prefixes in a homenet, such that hosts become multi-addressed with both globally unique and ULA prefixes. 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.

ULA addresses will allow constrained LLN devices to create permanent relationships between IPv6 addresses, e.g. from a wall controller to a lamp. Symbolic host names would require additional non-volatile memory. Updating global prefixes in sleeping LLN devices might also be problematic.

ULAs may be used for all devices, not just those intended to only have internal connectivity. ULAs used in this way provide stable internal communications should the ISP-provided prefix (suddenly) change, or external connectivity be temporarily lost. The use of ULAs should be restricted to the homenet scope through filtering at the border(s) of the homenet, as described in RFC 6092.

3.4.3. Internal prefix delegation

As mentioned above, there are various sources of prefixes, e.g. they may be globally unique prefixes originating from ISP(s), they may be globally unique or ULA prefixes allocated by "master" router(s) in the homenet, or they may be ULAs allocated by LLN gateways. There may also be a prefix associated with NAT64, if in use in the homenet.

From the homenet perspective, a single prefix from each ISP should be received on the border CER [RFC3633]. Then each subnet in the homenet should receive a prefix from within the ISP-provided prefix(es). The ISP should only see the aggregate from the homenet, and not single /64 prefixes allocated within the homenet.

Delegation should be autonomous, and not assume a flat or hierarchical model. This text makes no assumption about whether the delegation of 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. A currently typical /60 allocation gives 16 /64 subnets. Duplicate assignment of multiple /64s to the same network should be avoided. The network should behave as gracefully as possible in the event of prefix exhaustion, though the options in such cases may be limited.

Where multiple CERs 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.

Where ULAs are used, most likely but not necessarily in parallel with global prefixes, one router should be elected to offer ULA prefixes for the homenet. The router should generate a /48 ULA for the site, and then delegate /64's from that ULA prefix to subnets. In the normal state, a single /48 ULA should be used within the homenet. In cases where two /48 ULAs are generated within a homenet, the network should still continue to function.

Delegation within the homenet should give each link a prefix that is persistent across reboots, power outages and similar short-term outages. 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. Persistent prefixes should not depend on router boot order. 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).

The delegation method should support renumbering, which would typically be "flash" renumbering in that the homenet would not have advance notice of the event or thus be able to apply the types of approach described in [RFC4192]. As a minimum, delegated ULA prefixes within the homenet should remain persistent through an ISP-driven renumbering event.

Several proposals have been made for prefix delegation within a homenet. One group of proposals is based on DHCPv6 PD, as described in [I-D.baker-homenet-prefix-assignment], [I-D.chakrabarti-homenet-prefix-alloc], [RFC3315] and [RFC3633]. The other uses OSPFv3, as described in [I-D.arkko-homenet-prefix-assignment]. More detailed analysis of these approaches needs to be made against the requirements/principles described above.

3.4.4. Privacy

There are no specific privacy concerns discussed in this text. It should be noted as above that many ISPs are expected to offer relatively stable IPv6 prefixes to customers, and thus the network prefix associated with the host addresses they use may not change over a reasonably long period of time. This exposure is similar to IPv4 networks that expose the same IPv4 global address via use of NAT, where the IPv4 address received from the ISP may change over time, but not necessarily that frequently.

Hosts inside an IPv6 homenet may get new IPv6 addresses over time regardless, e.g. through Privacy Addresses [RFC4941].

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, or, more likely, it would involve running an appropriate routing protocol.

The homenet routing protocol should preferably be an existing deployed protocol that has been shown to be reliable and robust, and it is preferable that the protocol is "lightweight". It is desirable that the routing protocol has knowledge of the homenet topology, which implies a link-state protocol is preferable. If so, it is also desirable that the announcements and use of LSAs and RAs are appropriately coordinated. This would mean the routing protocol gives a consistent view of the network, and that it can pass around more than just routing information.

Multiple interface PHYs must be accounted for in the homenet routed topology. Technologies such as Ethernet, WiFi, MoCA, etc must be capable of coexisting in the same environment and should be treated as part of any routed deployment. The inclusion of the PHY layer characteristics including bandwidth, loss, and latency in path computation should be considered for optimising communication in the homenet. Multiple upstreams should be supported, as described in the multihoming section earlier. This should include load-balancing to multiple providers, and failover from a primary to a backup link when available. The protocol however should not require upstream ISP connectivity to be established to continue routing within the homenet.

To support multihoming within a homenet, a routing protocol that can make routing decisions based on source and destination addresses is desirable, to avoid upstream ISP ingress filtering problems. In general the routing protocol should support multiple ISP uplinks and delegated prefixes in concurrent use.

The routing environment should be self-configuring, as discussed previously. An example of how OSPFv3 can be self-configuring in a homenet is described in [I-D.acee-ospf-ospfv3-autoconfig]. Minimising convergence time should be a goal in any routed environment, but as a guideline a maximum convergence time of around 30 seconds should be the target.

Any routed solution will require a means for determining the boundaries of the homenet. Borders may include but are not limited to the interface to the upstream ISP, or a gateway device to a separate home network such as a SmartGrid or similar LLN network. In some cases there may be no border such as occurs before an upstream connection has been established. The border discovery functionality may be integrated into the routing protocol itself, but may also be imported via a separate discovery mechanism.

In general, LLN or other networks should be able to attach and participate the same way as the main homenet, or alternatively map/be gatewayed to the main homenet. Current home deployments use largely different mechanisms in sensor and basic Internet connectivity networks. IPv6 VM solutions may also add additional routing requirements.

[I-D.howard-homenet-routing-comparison] contains evaluations of common routing protocols made against the type of requirements described above.

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. However, there are other challenges introduced, e.g. default filtering policies at the borders between other homenet realms.

There is no defined "threat model" as such for the type of IPv6 homenet described in this text. Such a document may be very useful. It may include a variety of perspectives, from probing for specific types of home appliance being present, to potential denial of service attacks. Hosts need to be able to operate securely, end-to-end where required, but also be robust against malicious traffic direct towards them. We simply note at this point that software on home devices will have an increase in security if it allows its software to be updated regularly.

3.6.1. Addressability vs reachability

An IPv6-based home network architecture should embrace and naturally offer a transparent end-to-end communications model as described in [RFC2775]. Each device should be addressable by a globally unique address, and those addresses must not be altered in transit. Security perimeters can (via policy) restrict end-to-end communications, and thus while a host may be globally addressable it may not be globally reachable.

In IPv4 NAT networks, the NAT provides an implicit firewall function. [RFC4864] describes a "Simple Security" model for IPv6 networks, whereby stateful perimeter filtering can be applied instead where global addresses are used. RFC 4864 implies an IPv6 "default deny" policy for inbound connections be used for similar functionality to IPv4 NAT. It should be noted that such a "default deny" 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. Thus to support applications wanting to accept connections initiated into home networks where a "default deny" policy is in place support for a signalling protocol such as UPnP or PCP [I-D.ietf-pcp-base] is required. In networks with multiple CERs, the signalling would need to handle the cases of flows that may use one or more exit routers. CERs would need to be able to advertise their existence for such protocols.

[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 proscribe a particular mode of operation, instead stating that CERs must provide an easily selected configuration option that permits a "transparent" mode of operation, thus ensuring a "default allow" model is available. The homenet architecture text makes no recommendation on the default setting, and refers the reader to RFC 6092, which in turn simply states that a CER should provide functionality sufficient to support the recommendations in that RFC.

Advanced Security for IPv6 CPEs [I-D.vyncke-advanced-ipv6-security] takes the approach that in order to provide the greatest end-to-end transparency as well as security, security policies must be updated by a trusted party which can provide intrusion signatures and other "active" information on security threats. This might for example allow different malware detection profiles to be configured on a CER. Such methods should be able to be automatically updating.

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 then the means to 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 visitor in a "guest" network access to media services in the home, or access to a printer in the residence. 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 guest network subnet(s). Some scenarios/models may as a result involve running isolated subnet(s) with their own CERs. In such cases connectivity would only be expected within each isolated network (though traffic may potentially pass between them via external providers).

LLNs provide an another example of where there may be secure perimeters inside the homenet. Constrained LLN nodes may implement WPA2-style network key security but may depend on access policies enforced by the LLN border router.

3.6.3. 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 to be initiated to them, either for all ports or for specific services. Users should have simple methods to associate devices to services that they wish to operate transparently through (CER) borders.

3.6.4. ULAs as a hint of connection origin

It has been suggested that using ULAs would provide an indication to applications that received traffic is locally sourced. This could then be used with security settings to designate where a particular application is allowed to connect to or receive traffic from.

3.7. Naming and Service Discovery

Naming and service discovery must be supported in the homenet. The service(s) providing this function must support unmanaged operation.

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 potentially respecting policy borders such as those between visitor and internal network realms.

Users will want simple ways to name devices, or be provided with appropriate ways for devices to generate unique names within the homenet. Users may typically perform device (re)naming and discovery through GUI interfaces that hide the local domain name element from them. Users may also wish to associated named devices to Internet domains, so that devices in their homenet can be accessed remotely. Thus from the user's perspective a device is given a name; the user may expect that same unqualified name toy be valid within the local name service or through an Internet name service. Thus implies relative name resolution should be supported, i.e. there is some naming convention that allows name resolution while mitigating the need for the user to know an absolute location in the Internet name space. Or that there is some means to discover the domain transparently to the user.

Homenet devices may thus appear in one or more local homenet name spaces and also in one or more Internet name spaces. While typically there would be only one local name space, there may be scenarios where segmentation of that name space may be desirable. The naming system will be required to work internally or externally, be the user within the homenet or outside it, and there may be multiple naming domains used for any given device, e.g. Internet, home or guest domains. It is likely that a home user will want access to many of the devices and services in their home while "roaming" elsewhere. However, 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" is preferred for certain devices.

The homenet name service must therefore at the very least co-exist with Internet name services. 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 mDNS. Consideration should be made for how these interact with each other in a homenet scenario.

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 (as per mDNS and DNS-SD) or a service where applications register in order to be found.

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 the local network should also be able to perform a complete restart in the absence of external connectivity, and have local naming and discovery operate correctly. This might be achieved via a local cache and an authoritative local name service. Also, a change in ISP should also not affect local naming and service discovery.

There should be consideration of the security of any local name space. A typical problem here may be that many homenets may use a common "well-known" local domain suffix, e.g. .local, and this may be ambiguous to a device that could attach to multiple homenets that use that name, but this is also part of the "avoid joining unintended networks" problem. A method to utilise a local trust anchor is desirable.

With the introduction of new "dotless" top level domains, there is potential for ambiguity between for example a local host called "computer" and (if it is registered) a .computer gTLD. This suggests some implicit local name space is probably required. Such a name space should also be configurable to something else by the user. Discovery of a name service for access to external Internet resources is also a fundamental requirement in a multi-subnet homenet; the problem is not just name and service discovery within the homenet itself.

In some parts of the homenet, e.g. LLNs, devices may be sleeping, in which case a proxy for such nodes may be required, that can respond for example to multicast service discovery requests. Those same 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 the service may need to operate over.

A desirable target may be a fully functional, self-configuring secure local name service so that all devices can be referred to by name, and these FQDNs are resolved locally. This could make clean use of ULAs and multiple ISP-provided prefixes much easier. Such a local name service should be (by default) authoritative for the local name space in both IPv4 and IPv6. A dual-stack residential gateway should include a dual-stack DNS server.

Current service discovery protocols are generally aimed at single subnets. If service discovery is to operate across the an entire homenet, by adopting an approach like that proposed as Extended mDNS (xmDNS) [I-D.lynn-homenet-site-mdns], then support may be required for IPv6 multicast across the scope of the whole homenet.

3.8. Other Considerations

This section discusses some other considerations for home networking that may affect the architecture.

3.8.1. Proxy or Extend?

There are two broad choices for allowing services that would otherwise be link-local to work across a homenet site. In the example of service discovery, one is to take protocols like mDNS and have them run over site multicast within the homenet. This is fine if all hosts support the extension, and the scope within any internal borders is well-understood. But it's not backwards-compatible with existing link-local protocols. The alternative is to proxy service discovery across each link, to propagate it. This is more complex, but is backwards-compatible. It would need to work with IPv6, and dual-stack.

The homenet architecture proposes that any existing protocols that are designed to only work within a subnet should be extended to work across subnets, rather than defining proxy capabilities for each of those functions. However, while it is desirable to extend protocols to site scope operation rather than providing proxy functions on subnet boundaries, the reality is that until all hosts can use site-scope discovery protocols, existing link-local protocols would need to be proxied anyway.

Some protocols already have proxy functions defined and in use, e.g. DHCPv6 relays, in which case those protocols would be expected to continue to operate that way.

3.8.2. Quality of Service

Support for QoS in a multi-service homenet may be a requirement, e.g. for a critical system (perhaps healthcare related), or for differentiation between different types of traffic (file sharing, cloud storage, live streaming, VoIP, etc). Different 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 should 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 CER, and potentially around boundaries between different media types (where for example some traffic may simply not be appropriate for some media, and need to be dropped to avoid drowning 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].

3.8.3. Operations and Management

The homenet should be self-organising and configuring as far as possible, and thus not be pro-actively managed by the home user. Thus protocols to manage the network are not discussed in this architecture text.

However, users may be interested in the status of their networks and devices on the network, in which case simplified monitoring mechanisms may be desirable. It may also be the case that an ISP, or a third party, might offer management of the homenet on behalf of a user, in which case management protocols would be required. How such management is done is out of scope of this document; many solutions exist.

3.9. Implementing the Architecture on IPv6

This architecture text encourages re-use of existing protocols. Thus the necessary mechanisms are largely already part of the IPv6 protocol set and common implementations. There are though some exceptions. For automatic routing, it is expected that existing routing protocols can be used as is. However, a new mechanism may be needed in order to turn a selected protocol on by default.

Some functionality, if required by the architecture, would add 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 multicast-based 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 domain "home" 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 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. References

5.1. Normative References

[RFC2460] Deering, S.E. and R.M. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003.
[RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6", RFC 3736, April 2004.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, October 2005.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006.
[RFC4864] Van de Velde, G., Hain, T., Droms, R., Carpenter, B. and E. Klein, "Local Network Protection for IPv6", RFC 4864, May 2007.
[RFC4941] Narten, T., Draves, R. and S. Krishnan, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 4941, September 2007.
[RFC6092] Woodyatt, J., "Recommended Simple Security Capabilities in Customer Premises Equipment (CPE) for Providing Residential IPv6 Internet Service", RFC 6092, January 2011.
[RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B. and O. Troan, "Basic Requirements for IPv6 Customer Edge Routers", RFC 6204, April 2011.
[I-D.ietf-v6ops-6204bis] Singh, H, Beebee, W, Donley, C and B Stark, "Basic Requirements for IPv6 Customer Edge Routers", Internet-Draft draft-ietf-v6ops-6204bis-09, May 2012.

5.2. 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.
[RFC2475] Blake, S., Black, D.L., Carlson, M.A., Davies, E., Wang, Z. and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998.
[RFC2775] Carpenter, B.E., "Internet Transparency", RFC 2775, February 2000.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network Address Translator (Traditional NAT)", RFC 3022, January 2001.
[RFC3646] Droms, R., "DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, December 2003.
[RFC4192] Baker, F., Lear, E. and R. Droms, "Procedures for Renumbering an IPv6 Network without a Flag Day", RFC 4192, September 2005.
[RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming Shim Protocol for IPv6", RFC 5533, June 2009.
[RFC5969] Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4 Infrastructures (6rd) -- Protocol Specification", RFC 5969, August 2010.
[RFC6106] Jeong, J., Park, S., Beloeil, L. and S. Madanapalli, "IPv6 Router Advertisement Options for DNS Configuration", RFC 6106, November 2010.
[RFC6144] Baker, F., Li, X., Bao, C. and K. Yin, "Framework for IPv4/IPv6 Translation", RFC 6144, April 2011.
[RFC6145] Li, X., Bao, C. and F. Baker, "IP/ICMP Translation Algorithm", RFC 6145, April 2011.
[RFC6177] Narten, T., Huston, G. and L. Roberts, "IPv6 Address Assignment to End Sites", BCP 157, RFC 6177, March 2011.
[RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix Translation", RFC 6296, June 2011.
[RFC6333] Durand, A., Droms, R., Woodyatt, J. and Y. Lee, "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion", RFC 6333, August 2011.
[RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with Dual-Stack Hosts", RFC 6555, April 2012.
[I-D.baker-fun-multi-router] Baker, F, "Exploring the multi-router SOHO network", Internet-Draft draft-baker-fun-multi-router-00, July 2011.
[I-D.lynn-homenet-site-mdns] Lynn, K and D Sturek, "Extended Multicast DNS", Internet-Draft draft-lynn-homenet-site-mdns-00, March 2012.
[I-D.townsley-troan-ipv6-ce-transitioning] Townsley, M and O Troan, "Basic Requirements for Customer Edge Routers - multihoming and transition", Internet-Draft draft-townsley-troan-ipv6-ce-transitioning-02, December 2011.
[I-D.baker-fun-routing-class] Baker, F, "Routing a Traffic Class", Internet-Draft draft-baker-fun-routing-class-00, July 2011.
[I-D.howard-homenet-routing-comparison] Howard, L, "Evaluation of Proposed Homenet Routing Solutions", Internet-Draft draft-howard-homenet-routing-comparison-00, December 2011.
[I-D.herbst-v6ops-cpeenhancements] Herbst, T and D Sturek, "CPE Considerations in IPv6 Deployments", Internet-Draft draft-herbst-v6ops-cpeenhancements-00, October 2010.
[I-D.vyncke-advanced-ipv6-security] Vyncke, E, Yourtchenko, A and M Townsley, "Advanced Security for IPv6 CPE", Internet-Draft draft-vyncke-advanced-ipv6-security-03, October 2011.
[I-D.ietf-6man-rfc3484bis] Thaler, D, Draves, R, Matsumoto, A and T Chown, "Default Address Selection for Internet Protocol version 6 (IPv6)", Internet-Draft draft-ietf-6man-rfc3484bis-01, March 2012.
[I-D.v6ops-multihoming-without-ipv6nat] Troan, O, Miles, D, Matsushima, S, Okimoto, T and D Wing, "IPv6 Multihoming without Network Address Translation", Internet-Draft draft-v6ops-multihoming-without-ipv6nat-00, March 2011.
[I-D.baker-homenet-prefix-assignment] Baker, F and R Droms, "IPv6 Prefix Assignment in Small Networks", Internet-Draft draft-baker-homenet-prefix-assignment-00, October 2011.
[I-D.arkko-homenet-prefix-assignment] Arkko, J and A Lindem, "Prefix Assignment in a Home Network", Internet-Draft draft-arkko-homenet-prefix-assignment-01, October 2011.
[I-D.acee-ospf-ospfv3-autoconfig] Lindem, A and J Arkko, "OSPFv3 Auto-Configuration", Internet-Draft draft-acee-ospf-ospfv3-autoconfig-00, October 2011.
[I-D.ietf-pcp-base] Wing, D, Cheshire, S, Boucadair, M, Penno, R and P Selkirk, "Port Control Protocol (PCP)", Internet-Draft draft-ietf-pcp-base-22, January 2012.
[I-D.hain-ipv6-ulac] Hain, T, Hinden, R and G Huston, "Centrally Assigned IPv6 Unicast Unique Local Address Prefixes", Internet-Draft draft-hain-ipv6-ulac-02, July 2010.
[I-D.chakrabarti-homenet-prefix-alloc] Nordmark, E, Chakrabarti, S, Krishnan, S and W Haddad, "Simple Approach to Prefix Distribution in Basic Home Networks", Internet-Draft draft-chakrabarti-homenet-prefix-alloc-01, October 2011.
[I-D.arkko-homenet-physical-standard] Arkko, J and A Keranen, "Minimum Requirements for Physical Layout of Home Networks", Internet-Draft draft-arkko-homenet-physical-standard-00, March 2012.
[Gettys11] Gettys, J., "Bufferbloat: Dark Buffers in the Internet", March 2011.
[IGD-2] UPnP Gateway Committee, , "Internet Gateway Device (IGD) V 2.0", September 2010.

Appendix A. Acknowledgments

The authors would like to thank Aamer Akhter, Mark Andrews, Dmitry Anipko, Fred Baker, Ray Bellis, Cameron Byrne, Brian Carpenter, Stuart Cheshire, Lorenzo Colitti, Robert Cragie, 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, Kerry Lynn, Erik Nordmark, Michael Richardson, Barbara Stark, Sander Steffann, Dave Taht, Dave Thaler, Mark Townsley, JP Vasseur, Curtis Villamizar, Dan Wing, Russ White, and James Woodyatt for their contributions within homenet WG meetings and on the WG mailing list.

Appendix B. Changes

This section will be removed in the final version of the text.

Appendix B.1. Version 04

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Appendix B.2. Version 03

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Appendix B.3. Version 02

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Authors' Addresses

Tim Chown (editor) University of Southampton Highfield Southampton , Hampshire SO17 1BJ United Kingdom EMail:
Jari Arkko Ericsson Jorvas, 02420 Finland EMail:
Anders Brandt Sigma Designs Emdrupvej 26A, 1 Copenhagen, DK-2100 Denmark EMail:
Ole Troan Cisco Systems, Inc. Drammensveien 145A Oslo, N-0212 Norway EMail:
Jason Weil Time Warner Cable 13820 Sunrise Valley Drive Herndon, VA, 20171 USA EMail: