One document matched: draft-ietf-homenet-arch-02.xml
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]>
<rfc ipr="trust200902"
docName="draft-ietf-homenet-arch-02"
category="info">
<?rfc toc="yes"?> <?rfc symrefs="yes"?> <?rfc autobreaks="yes"?>
<?rfc tocindent="yes"?> <?rfc compact="yes"?> <?rfc subcompact="no"?>
<front>
<title abbrev="IPv6 Home Networking">Home Networking Architecture for IPv6</title>
<author fullname="Tim Chown" initials="T.J." surname="Chown" role="editor">
<organization> University of Southampton </organization>
<address>
<postal>
<street> Highfield </street>
<city> Southampton </city>
<code> SO17 1BJ </code>
<region> Hampshire </region>
<country> United Kingdom </country>
</postal>
<email> tjc@ecs.soton.ac.uk </email>
</address>
</author>
<author initials="J" surname="Arkko" fullname="Jari Arkko">
<organization>Ericsson</organization>
<address>
<postal>
<street/>
<city>Jorvas</city> <code>02420</code>
<country>Finland</country>
</postal>
<email>jari.arkko@piuha.net</email>
</address>
</author>
<author initials="A" surname="Brandt" fullname="Anders Brandt">
<organization>Sigma Designs</organization>
<address>
<postal>
<street>Emdrupvej 26A, 1</street>
<city>Copenhagen</city> <code>DK-2100</code>
<country>Denmark</country>
</postal>
<email>abr@sdesigns.dk</email>
</address>
</author>
<author initials="O" surname="Troan" fullname="Ole Troan">
<organization>Cisco Systems, Inc.</organization>
<address>
<postal>
<street>Drammensveien 145A</street>
<city>Oslo</city><code>N-0212</code>
<country>Norway</country>
</postal>
<email>ot@cisco.com</email>
</address>
</author>
<author initials="J" surname="Weil" fullname="Jason Weil">
<organization>Time Warner Cable</organization>
<address>
<postal>
<street>13820 Sunrise Valley Drive</street>
<city>Herndon, VA</city><code>20171</code>
<country>USA</country>
</postal>
<email>jason.weil@twcable.com</email>
</address>
</author>
<date month="March" year="2012" />
<keyword>IPv6</keyword>
<abstract>
<t>This text describes evolving networking technology within small
residential home networks. The goal of this memo is to define the
architecture for IPv6-based home networking and the associated
principles, considerations and requirements. The text briefly highlights
the implications of the introduction of IPv6 for home networking,
discusses topology scenarios, 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.
</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>This document focuses on evolving networking technology within
small residential home networks and the associated challenges. 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. There are also likely to be scenarios where internal routing
is required, for example to support private and guest networks, in
which case home networks will use multiple subnets. </t>
<t> While some advanced home networks 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. 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.</t>
<t>This architecture document aims to provide the basis and
guiding principles for how
standard IPv6 mechanisms and addressing <xref target="RFC2460"/> <xref
target="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. 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.</t>
<t>
<xref target="RFC6204"/> defines basic requirements for customer edge
routers (CERs). The scope of this text is the homenet, and thus the
relevant part of RFC 6204 is the internal facing interface as well as
any other components within the home network. While the network may be
dual-stack or IPv6-only, the definition of specific transition tools
on the CER are out of scope of this text, as is any advice regarding
architecture of the IPv4 part of the network. We assume that IPv4 network
architecture in home networks is what it is, and can not be affected by
new recommendations.
</t>
<t>
This architecture document proposes a baseline homenet architecture, based
on protocols and implementations that are as far as possible proven and
robust, and as such is a "version 1" architecture. A future architecture
may incorporate more advanced elements at a later date.
</t>
<section title="Terminology and Abbreviations">
<t>
In this section we define terminology and abbreviations used throughout the text.
</t>
<t>
<list style="symbols">
<t>CER: Customer Edge Router. The border router at the edge of the homenet.</t>
<t>LLN: Low-power and lossy network.</t>
<t>NAT: Network Address Translation. Typically referring to Network Address
and Port Translation (NAPT) <xref target="RFC3022"/>.</t>
<t>NPTv6: Network Prefix Translation for IPv6 <xref target="RFC6296"/>.</t>
<t>PCP: Port Control Protocol <xref target="I-D.ietf-pcp-base"></xref>. </t>
<t>ULA: Unique Local Addresses <xref target="RFC4193"></xref>.</t>
<t>UPnP: Universal Plug and Play. Includes Internet Gateway Device (IGD)
function, which for IPv6 is UPnP IGD Version 2 <xref target="IGD-2"/>.</t>
<t>VM: Virtual machine.</t>
<t>WPA: Wi-Fi Protected Access, as defined by the Wi-Fi Alliance.</t>
</list>
</t>
</section>
</section>
<section anchor="trends" title="Effects of IPv6 on Home Networking">
<t>
Service providers are deploying IPv6, content is becoming available on
IPv6, 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, makes multi-addressing the
norm, and allows direct IP addressability and routing to devices in
the home from the Internet. This section presents an overview of some of
the key implications of the introduction of IPv6 for home networking,
that are both promising and problematic.
</t>
<section title="Multiple subnets and routers">
<t>
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.
</t>
<t>
For instance, a common feature in modern home routers is the
ability to support both guest and private network subnets. Also, 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. There may also be a need to
separate building control or corporate extensions from the main Internet
access network. Also, different subnets may be associated with parts of the
homenet that have different routing and security policies.</t>
<t>Documents that provide some more specific background and depth on this topic include:
<xref target="I-D.herbst-v6ops-cpeenhancements"></xref>,
<xref target="I-D.baker-fun-multi-router"></xref>, and
<xref target="I-D.baker-fun-routing-class"></xref>.</t>
<t> 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 will also be the need
to discover which are the border router(s) by an appropriate mechanism.
</t>
</section>
<section title="Global addressability and elimination of NAT">
<t>
Current IPv4 home networks typically receive a single global IPv4 address
from their ISP and use NAT with private <xref target="RFC1918"></xref>
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.
</t>
<t>
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.
</t>
<t>
In IPv4 NAT networks, the NAT provides an implicit firewall
function. <xref target="RFC4864"></xref> suggests that IPv6 networks
with global addresses utilise "Simple Security" in border firewalls to
restrict incoming connections through a default deny policy.
Applications or hosts wanting to accept inbound connections in networks
that are compliant with the architecture presented in this
document would then
need to signal that desire through a protocol such as UPnP or
<xref target="I-D.ietf-pcp-base">PCP</xref>. In networks
with multiple CERs, the signalling would need to handle the cases of
flows that may use one or both exit routers.
</t>
<t>
The "Simple Security" default deny approach effectively replaces the
need for IPv4 NAT traversal by a need to use a signalling protocol to
request a firewall hole be opened.
<xref target="RFC6092"></xref> states that while the default should be
default deny, CERs should also have an option to be put into a
"transparent" mode of operation which enables a default allow model.
</t>
<t>
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
presence or use of NAT.
</t>
</section>
<section title="Multi-Addressing of devices">
<t>
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) <xref target="RFC4193"></xref> (see below),
and one or more IPv6 Privacy Addresses <xref target="RFC4941"></xref>.
</t>
<t>
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 <xref
target="I-D.ietf-6man-rfc3484bis"/> provides a solution for this,
but 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 right source address to be used
for the corresponding uplink, but the node may not have the information
it needs to make that decision based on addresses alone.
</t>
</section>
<section title="Unique Local Addresses (ULAs)">
<t>
<xref target="RFC4193"></xref> 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 <xref
target="RFC6204"></xref>. A home network running IPv6 may deploy ULAs
for stable communication between devices (on different subnets) within the
network where externally allocated global prefix changes over time
(either due to
renumbering within the subscriber's ISP or a change of ISP) or where
external connectivity is temporarily unavailable.
</t>
<t>
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 are 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.
</t>
<t>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.</t>
<t>
ULA addresses will allow constrained LLN devices to create permanent
relations 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.
</t>
<t>
Default address selection mechanisms should ensure a ULA source address
is used to communicate with ULA destination addresses when appropriate.
Unlike the IPv4 RFC1918 space, the use of ULAs does not imply use of
host-based IPv6 NAT, or NPTv6 prefix-based NAT
<xref target="RFC6296"/>, rather that external communications should use
a node's globally unique IPv6 source address.
</t>
</section>
<section title="Security and borders">
<t>
<xref target="I-D.vyncke-advanced-ipv6-security">Advanced
Security for IPv6 CPEs</xref> 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. Such methods should be able to be automatically updating.
</t>
<t>
In addition to establishing the security mechanisms themselves,
it is important to know where the borders are at which they need to be
enabled. Any required policies must be able to be applied by typical
home users, e.g. to give a visitor in a "guest" network access to
media services in the home. Thus simple "association" mechanisms will
be required.
</t>
<t>
It may be useful 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 is useful for describing edge operations and interface
requirements across multiple functional areas including security, routing,
service discovery, and router discovery.
</t>
</section>
<section title="Naming, and manual configuration of IP addresses">
<t>
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, 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 discovery of services is imperative for easy
use of homenet devices and applications. </t>
<t>
In a multi-subnet homenet, naming and service discovery should be
expected to operate 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 scope for an improvement in IPv6.
</t>
</section>
</section>
<section anchor="arch" title="Architecture">
<t>An architecture outlines how to construct home networks involving
multiple routers and subnets. In this section, we present a set of
typical home network topology models/scenarios, followed by a list of
topics that may influence the architecture discussions, and a
set of architectural
principles that govern how the various nodes should work
together. Finally, some guidelines are given for realising the
architecture with the IPv6 addressing, prefix delegation,
global and ULA addresses, source address selection rules and other
existing components of the IPv6 architecture. The architecture also
drives what protocol extensions are necessary, as will be discussed
in <xref target="miss"/>.
</t>
<section title="Network Models">
<t>
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 architectures, such as separation of visitors
and private networks. These considerations apply to IPv6 networks
as well.
</t>
<t>
In general, the models described in
<xref target="RFC6204"/>
and <xref target="I-D.ietf-v6ops-ipv6-cpe-router-bis"/>
should be supported by an IPv6 home networking architecture.
</t>
<t>
The following properties apply to any IPv6 home network:
</t>
<t>
<list style="symbols">
<t>Presence of internal routers. The homenet may have one or more internal
routers, or may only provide subnetting from interfaces on the CER.</t>
<t>Presence of isolated internal subnets. There may be isolated internal
subnets, with
no direct connectivity between them within the homenet. Isolation may
be physical, or implemented via IEEE 802.1q VLANs.</t>
<t>Demarcation of the CER. The CER(s) may or may not be managed by
the ISP. If the demarcation point is such that the customer
can provide or manage the CER, its configuration must be simple. Both
models must be supported.</t>
</list>
</t>
<t>
It has also been suggested that various forms of multihoming are
more prevalent with IPv6 home networks. Thus the following properties
may also apply to such networks:
</t>
<t>
<list style="symbols">
<t>Number of upstream providers. A typical homenet might just have a
single upstream ISP, but it may become more common 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 be
walled gardens.</t>
<t>Number of CERs. The homenet may have a single CER, which might be
used for one or more providers, or multiple CERs. Multiple CERs adds
additional complexity for multihoming scenarios, and protocols like
PCP that need to manage connection-oriented state mappings.</t>
</list>
</t>
<t>
Some separate discussion of physical infrastructures
for homenets is included in
and <xref target="I-D.arkko-homenet-physical-standard"/>.
</t>
<t>
In the following sections we show some example homenet models.
</t>
<section title="A: Single ISP, Single CER, Internal routers">
<t>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. This is a valid consideration
as home users may plug routers together to form arbitrary topologies
including loops (we discuss support for arbitrary topologies in
layer sections).</t>
<figure align="left" anchor="Figure.1 ">
<preamble></preamble>
<artwork align="left">
+-------+-------+ \
| 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 | |
| | | | | | | | /
+----------+ +----------+ +----------+ +----------+ /
</artwork>
<postamble></postamble>
</figure>
</section>
<section title="B: Two ISPs, Two CERs, Shared subnet">
<figure align="left" anchor="Figure.2 ">
<preamble></preamble>
<artwork align="left">
+-------+-------+ +-------+-------+ \
| 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 | /
| | | | | | | | /
+----------+ +----------+ +----------+ +----------+
</artwork>
<postamble></postamble>
</figure>
<t>
Figure 2 illustrates a multihomed home network 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.
</t>
</section>
<section title="C: Two ISPs, One CER, Shared subnet">
<figure align="left" anchor="Figure.3 ">
<preamble></preamble>
<artwork align="left">
+-------+-------+ +-------+-------+ \
| 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 | /
| | | | | | | | /
+----------+ +----------+ +----------+ +----------+
</artwork>
<postamble></postamble>
</figure>
<t>
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.
</t>
</section>
</section>
<section anchor="req" title="Determining the Requirements">
<t><xref target="RFC6204"/> defines "basic" requirements for IPv6
Customer Edge Routers,
while <xref target="I-D.ietf-v6ops-ipv6-cpe-router-bis"></xref>
describes "advanced" features. In general, home network equipment needs to
cope with the different types of network properties and topologies
discussed above.
Manual configuration is rarely, if at all, possible, given the knowledge
level of typical home users. The equipment needs to be prepared
to handle at least
<list style="symbols">
<t>Routing</t>
<t>Prefix configuration for routers</t>
<t>Name resolution</t>
<t>Service discovery</t>
<t>Network security</t>
</list></t>
<t>
The remainder of the architecture document is presented as considerations
and principles that lead to more specific requirements for the five
general areas listed above.
</t>
</section>
<section title="Considerations">
<t>
This section lists some considerations for home networking that may
affect the architecture and associated requirements.
</t>
<section title="Multihoming">
<t>
A homenet may be multihomed to multiple providers. This may either
take a form where there are multiple isolated networks within the home
a more integrated network where the connectivity selection is dynamic.
Current practice is typically of the former kind, but the latter is
expected to become more commonplace.
</t>
<t>
In an integrated network, specific appliances or applications may
use their own external connectivity, or the entire network may
change its connectivity based on the status of the different upstream
connections. The complexity of the multihoming solution required
will depend on the Network Model deployed. For example, Network Model
C in the previous section has a single CER and thus could perform
source routing at the single network exit point.
</t>
<t>
The general approach for IPv6 multihoming is for a host to receive
multiple addresses from multiple providers, and to select the appropriate
source address to communicate via a given provider. An alternative is
to deploy ULAs with a site and then use NPTv6 <xref target="RFC6296"/>,
a prefix translation-based mechanism, at the edge. This obviously comes
at some architectural cost, which is why approaches such as
<xref target="I-D.v6ops-multihoming-without-ipv6nat"/> have been
suggested. There has been much work on multihoming in the IETF, without
(yet) widespread deployment of proposed solutions.
</t>
<t>
Host-based methods such
as Shim6 <xref target="RFC5533"/> have been defined, but of course
require support in the hosts. There are also application-oriented
approaches such as
<xref target="I-D.ietf-v6ops-happy-eyeballs">Happy Eyeballs</xref>
exist; simplified versions of this are implemented in some commonly
used web browsers for example.
</t>
<t>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 <xref target="RFC5969"/>
sunset scenario. Second, one upstream
may be a "walled garden", and thus only appropriate to be used for
connectivity to the services of that provider.
</t>
<t>
If the homenet architecture supports multihoming, additional requirements
apply. The general multihoming problem is broad, and solutions
may include complex architectures for monitoring connectivity,
traffic engineering, identifier-locator separation, connection survivability
across multihoming events, and so on. This implies that
if there is any support for multihoming defined in the homenet architecture
it should be limited to a very small subset of the overall problem.
</t>
<t>
The current set of assumptions and requirements proposed by
the homenet architecture team is:
</t>
<t><list style="format MH%d)">
<t>The homenet WG should not try to make another attempt at solving complex
multihoming; we should prefer to support scenarios for which solutions
exist today.</t>
<t>Single CER Network Model C is in scope, and may be solved by source
routing at the CER.</t>
<t>The architecture does not support deployment of NPTv6
<xref target="RFC6296"/> at the CER.
Hosts should be multi-addressed with globally unique prefixes
from each ISP they may communicate with or through.</t>
<t>Solutions that require host changes should be avoided, but solutions
which incrementally improve with host changes may be acceptable.</t>
<t>Walled garden multihoming is in scope. </t>
<t>Transition method sunsetting is in scope.
The topic of multihoming with specific (6rd) transition coexistence is
discussed in <xref target="I-D.townsley-troan-ipv6-ce-transitioning"></xref>. </t>
<t>"Just" picking the right source address to use to fall foul of ingress
filtering on upstream ISP connections (as per Network Model B) is not a
trivial task. A solution is highly desirable, but not required in the
baseline homenet architecture.</t>
<t>A multihoming model for multiple CERs based on
<xref target="I-D.baker-fun-multi-router"/> requires source routing throughout
the homenet and thus relatively significant routing changes to "guarantee"
routing the packet to the correct exit given the source address. Thus
this approach is currently out of scope for homenet.</t>
</list></t>
<t>
Thus the homenet multihoming support is focused on the single CER model.
</t>
</section>
<section title="Quality of Service">
<t>
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.
</t>
<t>
However, homenet scenarios should require no new QoS protocols.
A DiffServ
<xref target="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.
</t>
<t>
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 <xref target="Gettys11"/>.
</t>
</section>
<section title="Operations and Management">
<t>
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 detail in the architecture text.
</t>
<t>
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. The SNMPv3 family of protocols
described in <xref target="RFC3411"/> and friends may be appropriate
(previous versions are not deemed secure and have been marked as Historic
by the IETF).
</t>
</section>
<section title="Privacy considerations">
<t>
There are no specific privacy concerns discussed in this text. It should be
noted 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 would not generally change over a reasonable 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.
</t>
</section>
</section>
<section title="Design Principles and Requirements">
<t>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. In this section we discuss
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.</t>
<t>The following principles should be followed when designing homenet
solutions. Where requirements are associated with those principles,
they are listed here. There is no implied priority by the order in
which the principles themselves are listed.</t>
<section title="Reuse existing protocols">
<t>
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.
</t>
<t>
Where possible, changes to hosts should be minimised. Some changes may
be unavoidable however, e.g. signalling protocols to punch holes in
firewalls where "Simple Security" is deployed in a CER.
Changes to routers should also be minimised, e.g.
<xref target="I-D.baker-fun-routing-class"></xref> suggests introducing
a routing protocol that may route on both source and destination
addresses, which would be a significant change compared to current
practices.
</t>
<t>
Liaisons with other appropriate standards groups and related organisations
is desirable, e.g. the IEEE and Wi-Fi Alliance.
</t>
<t><list style="format RE%d)">
<t>Reuse existing protocols, giving weight to running code.</t>
<t>Minimise changes to hosts and routers.</t>
<t>Maintain backwards compatibility where possible.</t>
</list></t>
</section>
<section title="Dual-stack Operation">
<t>
The homenet architecture targets both IPv6-only and dual-stack networks.
While the CER requirements in RFC 6204 are aimed at IPv6-only networks,
it is likely that dual-stack homenets will be the norm for
some period of time. IPv6-only networking may first be deployed
in home networks in "greenfield" scenarios, or perhaps as one element
of an otherwise dual-stack network. The homenet architecture must
operate in the absence of IPv4, and IPv6 must work in the same scenarios
as IPv4 today.
</t>
<t>
Running IPv6-only may require documentation of additional considerations such as:
<list style="symbols">
<t>Ensuring there is a way to access content in the IPv4 Internet. This can
be arranged through incorporating <xref target="RFC6144">NAT64</xref>
and <xref target="RFC6145">DNS64</xref>
functionality in the home gateway router, for instance.</t>
<t>DNS discovery mechanisms are enabled for IPv6. Both stateless
DHCPv6 <xref target="RFC3736"/> <xref
target="RFC3646"/> and Router Advertisement options <xref
target="RFC6106"/> may have to be supported and turned on by default
to ensure maximum compatibility with all types of hosts in the
network. This requires, however, that a working DNS server is known
and addressable via IPv6.</t>
<t>All nodes in the home network support operations in IPv6-only
mode. Some current devices work well with dual-stack but fail to
recognise connectivity when IPv4 DHCP fails, for instance.</t>
</list>
</t>
<t>
In dual-stack networks, solutions for IPv6 should not adversely affect
IPv4 operation. It is likely that topologies of IPv4 and IPv6 networks
would be as congruent as possible.
</t>
<t>
Note that specific transition tools, particularly those running on the
border CER to support transition tools being used inside the homenet, are
out of scope. Use of tools, such as 6rd, on the border CER to support
ISP access network transition are to be expected, but not within scope
of homenet, which focuses on the internal networking.
</t>
<t><list style="format DS%d)">
<t>The homenet must support IPv6-only or dual-stack operation; it must
thus operate in the absence of IPv4 and IPv6 must work in the same scenarios
as IPv4 today.</t>
<t>IPv6 solutions should not adversely affect IPv4 operation.</t>
</list></t>
</section>
<section title="Largest Possible Subnets">
<t>
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.
</t>
<t>
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 network should subdivide
itself to the largest possible subnets that can be constructed within
the constraints of link layer mechanisms, bridging, physical
connectivity, and policy. For instance, separate subnetworks are
necessary where two different link layers cannot be bridged, or when a
policy requires the separation of private and visitor parts of the
network.</t>
<t>
While it may be desirable to maximise the chance of link-local
protocols operating across a homenet by maximising the size of a subnet
across the homenet, multiple subnet home networks are inevitable,
so their support must be included.
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.
</t>
<t>
In some cases IPv4 NAT
home networks may feature cascaded NATs, e.g. where NAT routers are
included within VMs or Internet connection services are used. IPv6
routed versions of such tools will be required.
</t>
<t><list style="format SN%d)">
<t>The network should subdivide itself to the largest possible subnets
that can be formed.</t>
<t>The IPv6 topology should follow the IPv4 topology, but not use NAT,
thus there should be routed IPv6 where IPv4 NAT is used.</t>
</list></t>
</section>
<section title="Security vs Transparent, End-to-End Communications">
<t>
An IPv6-based home network
architecture should naturally offer a transparent end-to-end
communications model as described in <xref target="RFC2775"/>.
Each device should be addressable by a globally unique
address, and those addresses must not be altered in transit.
Security perimeters can of course restrict the end-to-end
communications, and thus while a host may be globally addressable
it may not be globally reachable. RFC 4864 sets a default deny "Simple
Security" model, in which filtering is to be expected (while host-based
IPv6 NAT is not). However, RFC 6092 states that while the default should
be default deny, CERs should also have an option to be put into a
"transparent" mode of operation which enables a default allow model
(in which case home devices must be independently secure).
Such end-to-end communications are important for their robustness against
failure of intermediate systems, where in contrast NAT is dependent on
state machines which are not self-healing.
</t>
<t>
In the presence of "Simple Security" the use
of signalling protocols such as UPnP IGD (Version 2) or PCP may be
expected to punch
holes in the firewall (and be able to handle cases where there are
multiple CERs/firewall(s). When configuring holes in filters, protocols
for securely associating devices are desirable.
</t>
<t><list style="format EE%d)">
<t>The homenet should embrace transparent, end-to-end communications
to, from and within the homenet.</t>
<t>The default security model at the homenet border is "Simple Security"
(default deny).</t>
<t>Where "Simple Security" is applied, there must be support for an
appropriate signalling protocol to open per-application holes for
communications.</t>
<t>The homenet should also support a "transparent" mode of operation at
its borders if configured to do so.</t>
<t>Users should have simple methods to associate devices to services that
are expected to operate through borders at which "Simple Security"
is applied.</t>
</list></t>
</section>
<section title="IP Connectivity between All Nodes">
<t>
A logical consequence of the end-to-end
communications model is that the network should by default attempt to
provide IP-layer connectivity between all internal parts as well as between
the internal parts and the Internet. This connectivity should be
established at the link layer, if possible, and using routing at the
IP layer otherwise.</t>
<t>
Local addressing (ULAs) may be used within the scope of a home network
to provide a method to route between subnets.
It would be expected that ULAs may be used alongside one or more
globally unique ISP-provided addresses/prefixes in a homenet. ULAs
may be used for all devices, not just those intended to have internal
connectivity only. ULAs may then be used for 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; thus "end-to-end"
for ULAs is limited to the homenet.
</t>
<t>
In some cases 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). Certain
scenarios may require co-existence of ISP connectivity providing a
general Internet service with provider connectivity to a private "walled
garden" network.
</t>
<t>
Some home networking scenarios/models may involve 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).
</t>
<t>
LLNs provide an example of where there may be secure perimeters inside the
homenet. Constrained LLN nodes may implement WPA-style network key security
but may depend on access policies enforced by the LLN border router.
</t>
<t><list style="format CN%d)">
<t>The homenet should utilise ULAs to provide stable addressing in the
event of there being no global prefix available or changes in the
global prefix.</t>
<t>ULAs must be filtered at the homenet site border(s).</t>
<t>Walled garden connectivity must be supported.</t>
<t>Isolated networks within the homenet must be supported.</t>
</list></t>
</section>
<section title="Routing functionality">
<t>
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 it could involve running an appropriate
routing protocol.
</t>
<t>
The homenet routing environment may include traditional IP networking
where existing link-state or distance-vector protocols may be used, but
also new LLN or other "constrained" networks where other protocols
may be more appropriate. IPv6 VM solutions may also add additional
routing requirements. Current home deployments use largely different
mechanisms in sensor and basic Internet connectivity networks.
</t>
<t>
In this section we list the assumptions and requirements
for routing functionality within the homenet environment.
</t>
<t><list style="format RT%d)">
<t> The protocol should preferably be an existing deployed protocol
that has been shown to be reliable and robust. </t>
<t> It is preferable that the protocol is "lightweight". </t>
<t> The protocol should be able to provide reachability between all
nodes in the homenet.</t>
<t> 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.</t>
<t> 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.</t>
<t> Minimising convergence time should be a goal in any routed
environment, but as a guideline a maximum convergence time of a
couple of minutes should be the target.</t>
<t> It is desirable that the routing protocol has knowledge of the homenet
topology, which implies a link-state protocol may be preferable. If so,
it is also desirable that the announcements and use of LSAs and RAs are
appropriately coordinated. </t>
<t> 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,
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 before an upstream connection has been
established. Devices in the homenet must be able to find the path to the Internet as
well as other devices on the home intranet. The border discovery functionality may be
integrated into the routing protocol itself, but may also be imported via a separate
discovery mechanism. </t>
<t> The routing environment should be self-configuring, as discussed in the
next subsection. An
example of how OSPFv3 can be self-configuring in a homenet is
described in <xref target="I-D.acee-ospf-ospfv3-autoconfig"/>.
An exception is configuration of a "secret" for authentication methods.</t>
<t> The protocol should not require upstream ISP connectivity to be established to
continue routing within the homenet. </t>
<t> Multiple upstreams should be supported, as described in the multihoming
section earlier. The primary target for multihoming support is the single
CER case (where source routing may assist path selection).</t>
<t> 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. </t>
<t> Load-balancing to multiple providers is not a requirement, but
failover from a primary to a backup link when available must be a requirement. </t>
<t> It is assumed that the
typical router designed for residential use does not contain the
memory or CPU required to process a full Internet routing table
this should not be a requirement for any homenet device.</t>
</list></t>
<t>
A new I-D has been published on homenet routing requirements, see
<xref target="I-D.howard-homenet-routing-comparison"></xref> and
evaluations of common routing protocols made against those requirements,
see <xref target="I-D.howard-homenet-routing-requirements"></xref>.
The requirements from the former document have been worked into this
architecture text.
</t>
</section>
<section title="Self-Organising">
<t>
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. </t>
<t>
The homenet will need to be aware of the extent of its own "site".
The homenet will have one or more borders, with external connectivity
providers and potentially parts of the internal network (e.g. for
policy-based reasons). It should be possible to automatically perform
border discovery at least for the ISP borders. Such borders determine
for example the scope of ULAs, service discovery boundaries, site scope
multicast boundaries and
where firewall policies may be applied.
</t>
<t>
The most important function in this respect is prefix delegation and
management. The assumptions and requirements for the prefix delegation
function are summarised as follows:
</t>
<t><list style="format PD%d)">
<t> From the homenet perspective, a single prefix from each ISP should
be received on the border CER
<xref target="RFC3633"/>. The ISP should only see that aggregate, and
not single /64 prefixes allocated within the homenet. </t>
<t> Each link in the homenet should receive a prefix from within the
ISP-provided prefix(es). </t>
<t> Delegation should be autonomous, and not assume a flat or
hierarchical model. </t>
<t>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. A currently typical /60
allocation gives 16 /64 subnets.</t>
<t>Duplicate assignment of multiple /64s to the same network should be
avoided.</t>
<t> The network should behave as gracefully as possible
in the event of prefix exhaustion. The options in such cases may
however be limited. </t>
<t> 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.</t>
<t> Where ULAs are used, most likely but not necessarily in parallel with
global prefixes, one router will need to 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. </t>
<t> Delegation within the homenet should give each link a prefix that
is persistent across reboots, power outages and similar short-term
outages. </t>
<t> 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. </t>
<t> Persistent prefixes should not depend on router boot order. </t>
<t> 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).</t>
<t>The delegation method should support "flash" renumbering. As a minimum, delegated ULA prefixes within the homenet should remain persistent through an ISP-driven renumbering event. </t>
</list></t>
<t>
Several proposals have been made for prefix delegation within a homenet. One group of proposals
is based on DHCPv6 PD, as described in
<xref target="I-D.baker-homenet-prefix-assignment"/>,
<xref target="I-D.chakrabarti-homenet-prefix-alloc"/>,
<xref target="RFC3315"/> and <xref target="RFC3633"/>.
The other uses OSPFv3, as described in
<xref target="I-D.arkko-homenet-prefix-assignment"/>.
More detailed analysis of these approaches needs to be made against the requirements/assumptions
listed above.
</t>
<t>
Other parameters of the network will need to be self-organising.
The network elements will need to be integrated in a way that takes
account of the various lifetimes on timers that are used on those
different elements, e.g.
DHCPv6 PD, router, valid prefix and preferred prefix timers.
</t>
<t>
The network cannot be expected to be completely self-organising, e.g.
some security parameters are likely to need manual configuration,
e.g. WPA2 configuration for wireless access control. Some existing
mechanisms exist to assist home users to associate devices as simply
as possible, e.g. "connect" button support.
</t>
<t><list style="format ZC%d)">
<t>The homenet must as far as possible be self-organising and
self-configuring.</t>
<t>Manual override of the configuration should be possible.</t>
<t>The homenet must be able to determine where its own borders lie.</t>
<t>The homenet "site" defines the borders for ULAs, site scope multicast,
service discovery and security policies.</t>
<t>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. </t>
</list></t>
</section>
<section title="Fewest Topology Assumptions">
<t>
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 will need to be supported.</t>
<t>
It is important not to introduce new IPv6 scenarios that would break with
IPv4+NAT, given that dual-stack homenets will be commonplace for some time.
There may be IPv6-only topologies that work where IPv4 is not used or
required.
</t>
<t><list style="format ZC%d)">
<t>Arbitrary topologies should be supported.</t>
</list></t>
</section>
<section title="Naming and Service Discovery">
<t>
The most natural way to think about naming and service discovery
within a homenet is
to enable it to work across the entire residence (site), disregarding
technical borders such as subnets but respecting policy borders such
as those between visitor and internal networks.</t>
<t>
Homenet naming systems will be required that work internally or externally,
be the user within the homenet or outside it,
though the domains used may be different from those different perspectives.
It is possible that not all internal devices should be reflected by name
in an external-facing domain.
</t>
<t>
A desirable target may be a fully functional self-configuring secure
local DNS service so that all devices can be referred to by name,
and these FQDNs are resolved locally. This would make clean use of
ULAs and multiple ISP-provided prefixes much easier.
Such a local DNS 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.
</t>
<t>
Consideration will also need to be given for existing protocols that
may be used within a network, e.g. mDNS, and how these interact with
unicast-based DNS services.
</t>
<t>With the introduction of
new "dotless" top level domains, there is potential for ambiguity between
for example a local host called apple and (if it is registered)
an apple gTLD, so some local name space is probably required,
which should also be configurable to something else by a home user,
e.g. ".home", if desired. There is also potential
ambiguity if, for example, a mobile device should move between two
local name spaces called ".home".
</t>
<t>
For service discovery, support may be required for IPv6 multicast
across the scope of the home network. This would be the case if an
approach to create Extended mDNS (xmDNS) is followed as described in
<xref target="I-D.lynn-homenet-site-mdns"></xref>.
</t>
<t><list style="format SD%d)">
<t>The homenet must support naming and service discovery functions.</t>
<t>All naming and service discovery functions should be able to
function across the entire homenet site if required.</t>
<t>Disconnected operation ("fate sharing"): name resolution for reachable devices continues if the local network is disconnected from the global Internet.</t>
<t>Message utilisation should be efficient considering the network technologies
the service may need to operate over.</t>
<t>Devices represented in the homenet name space may also be represented
in the global DNS namespace.</t>
<t>Site scope IPv6 multicast should be supported across the homenet.</t>
</list></t>
</section>
<section title="Proxy or Extend?">
<t>
Related to the above, the architecture proposes that any existing
protocols (e.g. service discovery) that are designed to only work within
a subnet should be modified/extended
to work across subnets, rather than defining proxy capabilities
for each of those functions.
</t>
<t>
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.
</t>
<t>
Feedback is desirable on which other functions/protocols
assume subnet-only operation, in the context of existing home networks.
Some experience from enterprises may be relevant here.
</t>
<t><list style="format SD%d)">
<t>Prefer to extend protocols to site scope operation rather than providing
proxy functions on subnet boundaries.</t>
</list></t>
</section>
<section title="Adapt to ISP constraints">
<t>
Different homenets may be subject to different behaviour by its ISP(s).
The home network may receive an arbitrary length IPv6 prefix from
its provider, e.g. /60 or /56. The offered prefix may be stable over
time 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
<xref target="RFC6177"></xref>, which discusses why, for example, a
one-size-fits-all /48 allocation is not appropriate.
The home network needs to be adaptable to such ISP policies.
</t>
<t>
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 as supported in RFC6204.
If used, ULA addresses should be stable so that they can always be
used internally, independent of the link to the ISP.
</t>
<t>
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 in general residential homenets.
</t>
<t>
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 <xref target="RFC4192"></xref>, 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. The customer may of course also choose to move
to a new ISP, and thus begin using a new prefix, though in such cases the
customer may expect a discontinuity. Regardless, it's desirable that
homenet protocols support rapid renumbering and operational processes
don't add unnecessary complexity for the renumbering process.
</t>
<t>
The 6renum WG is studying IPv6 renumbering for enterprise networks. It is not
currently targetting homenets, but may produce outputs that are relevant.
</t>
<t><list style="format AD%d)">
<t>The homenet should make no assumptions about the stability of the prefix
received from an ISP, or the length of the prefix that may be offered.</t>
<t>The operation of the homenet must not depend on the availability of
the ISP connection.</t>
<t>The homenet should support "flash" renumbering. Applications and services
operating within or to/from the homenet should be as resilient as possible to an
external change of delegated prefix(es).</t>
</list></t>
</section>
</section>
<section anchor="miss" title="Implementing the Architecture on IPv6">
<t>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.
</t>
<t>
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 require extensions to support
source and destination address based routing within the homenet.
</t>
<t>
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.</t>
<t>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.</t>
</section>
</section>
<section title="Conclusions">
<t>
This text defines principles and requirements for a homenet architecture.
(More to be added.)
</t>
</section>
</middle>
<back>
<references title="Normative References">
&rfc1918;
&rfc2460;
&rfc2475;
&rfc3022;
&rfc3315;
&rfc3411;
&rfc3633;
&rfc4192;
&rfc4193;
&rfc4291;
&rfc4864;
&rfc4941;
&rfc5533;
&rfc5969;
&rfc6092;
&rfc6204;
&rfc6296;
</references>
<references title="Informative References">
&rfc2775;
&rfc3646;
&rfc3736;
&rfc6106;
&rfc6144;
&rfc6145;
&rfc6177;
&I-D.baker-fun-multi-router;
&I-D.lynn-homenet-site-mdns;
&I-D.townsley-troan-ipv6-ce-transitioning;
&I-D.baker-fun-routing-class;
&I-D.howard-homenet-routing-comparison;
&I-D.howard-homenet-routing-requirements;
&I-D.herbst-v6ops-cpeenhancements;
&I-D.vyncke-advanced-ipv6-security;
&I-D.ietf-v6ops-ipv6-cpe-router-bis;
&I-D.ietf-6man-rfc3484bis;
&I-D.v6ops-multihoming-without-ipv6nat;
&I-D.baker-homenet-prefix-assignment;
&I-D.arkko-homenet-prefix-assignment;
&I-D.acee-ospf-ospfv3-autoconfig;
&I-D.ietf-pcp-base;
&I-D.ietf-v6ops-happy-eyeballs;
&I-D.chakrabarti-homenet-prefix-alloc;
&I-D.arkko-homenet-physical-standard;
<reference anchor='Gettys11' target="http://www.ietf.org/proceedings/80/slides/tsvarea-1.pdf">
<front>
<title>Bufferbloat: Dark Buffers in the Internet</title>
<author initials="J." surname="Gettys" fullname=" Jim Gettys"> <organization />
</author>
<date month="March" year="2011" />
</front>
</reference>
<reference anchor="IGD-2" target="http://upnp.org/specs/gw/UPnP-gw-WANIPConnection-v2-Service.pdf">
<front>
<title>Internet Gateway Device (IGD) V 2.0</title>
<author fullname="UPnP Gateway Committee"
surname="UPnP Gateway Committee">
<organization>UPnP Forum</organization>
</author>
<date month="September" year="2010" />
</front>
</reference>
</references>
<section title="Acknowledgments">
<t>The authors would like to thank Brian Carpenter,
Mark Andrews,
Fred Baker,
Ray Bellis,
Cameron Byrne,
Brian Carpenter,
Stuart Cheshire,
Lorenzo Colitti,
Ralph Droms,
Lars Eggert,
Jim Gettys,
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 Thaler,
JP Vasseur,
Curtis Villamizar,
Dan Wing,
Russ White,
and James Woodyatt
for their contributions within homenet WG meetings and the mailing list,
and Mark Townsley
for being an initial editor/author of this text before taking his
position as homenet WG co-chair.</t>
</section>
<section title="Changes">
<t>This section will be removed in the final version of the text.
</t>
<section title="Version 02">
<t>Changes made include:</t>
<t>
<list style="symbols">
<t>Made the IPv6 implications section briefer.</t>
<t>Changed Network Models section to describe properties of the homent
with illustrative examples, rather than implying the number of models
was fixed to the six shown in 01. </t>
<t>Text to state multihoming support focused on single CER model.
Multiple CER support is desirable, but not required.</t>
<t>Stated that NPTv6 not supported.</t>
<t>Added considerations section for operations and management.</t>
<t>Added bullet point principles/requirements to Section 3.4.</t>
<t>Changed IPv6 solutions must not adversely affect IPv4 to should not.</t>
<t>End-to-end section expanded to talk about "Simple Security" and borders.</t>
<t>Extended text on naming and service discovery.</t>
<t>Added reference to RFC 2775, RFC 6177.</t>
<t>Added reference to the new xmDNS draft.</t>
<t>Added naming/SD requirements from Ralph Droms.</t>
</list>
</t>
</section>
</section>
</back>
</rfc>
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