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Versions: (draft-chown-homenet-arch) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 RFC 7368

Network Working Group                                           J. Arkko
Internet-Draft                                                  Ericsson
Intended status: Informational                                 A. Brandt
Expires: August 2, 2012                                    Sigma Designs
                                                                T. Chown
                                               University of Southampton
                                                                 J. Weil
                                                       Time Warner Cable
                                                                O. Troan
                                                     Cisco Systems, Inc.
                                                        January 30, 2012


                 Home Networking Architecture for IPv6
                       draft-ietf-homenet-arch-01

Abstract

   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 highlights the
   impact of IPv6 on home networking, illustrates topology scenarios,
   and shows how standard IPv6 mechanisms and addressing can be employed
   in home networking.  The architecture describes the need for specific
   protocol extensions for certain additional functionality.  It is
   assumed that the IPv6 home network is not actively managed, and runs
   as an IPv6-only or dual-stack network.  There are no recommendations
   in this text for the IPv4 part of the network.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 2, 2012.

Copyright Notice



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   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.







































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology and Abbreviations  . . . . . . . . . . . . . .  5
   2.  Effects of IPv6 on Home Networking . . . . . . . . . . . . . .  5
     2.1.  Multiple subnets and routers . . . . . . . . . . . . . . .  5
     2.2.  Multi-Addressing of devices  . . . . . . . . . . . . . . .  6
     2.3.  Unique Local Addresses (ULAs)  . . . . . . . . . . . . . .  6
     2.4.  Security, Borders, and the elimination of NAT  . . . . . .  7
     2.5.  Naming, and manual configuration of IP addresses . . . . .  9
   3.  Architecture . . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Network Models . . . . . . . . . . . . . . . . . . . . . .  9
       3.1.1.  A: Single ISP, Single CER, Single subnet . . . . . . . 10
       3.1.2.  B: Single ISP, Single CER, Multiple subnets  . . . . . 11
       3.1.3.  C: Single ISP, Single CER, Multiple internal
               subnets  . . . . . . . . . . . . . . . . . . . . . . . 12
       3.1.4.  D: Two ISPs, Two CERs, Shared subnets with
               multiple internal routers  . . . . . . . . . . . . . . 14
       3.1.5.  E: Two ISPs, One CER, Isolated subnets with
               multiple internal routers  . . . . . . . . . . . . . . 15
       3.1.6.  F: Two ISPs, One CER, Shared subnets with multiple
               internal routers . . . . . . . . . . . . . . . . . . . 16
     3.2.  Determining the Requirements . . . . . . . . . . . . . . . 16
     3.3.  Considerations . . . . . . . . . . . . . . . . . . . . . . 17
       3.3.1.  Multihoming  . . . . . . . . . . . . . . . . . . . . . 17
       3.3.2.  Quality of Service in multi-service home networks  . . 19
       3.3.3.  Privacy considerations . . . . . . . . . . . . . . . . 19
     3.4.  Principles . . . . . . . . . . . . . . . . . . . . . . . . 19
       3.4.1.  Reuse existing protocols . . . . . . . . . . . . . . . 19
       3.4.2.  Dual-stack Operation . . . . . . . . . . . . . . . . . 20
       3.4.3.  Largest Possible Subnets . . . . . . . . . . . . . . . 21
       3.4.4.  Transparent End-to-End Communications  . . . . . . . . 21
       3.4.5.  IP Connectivity between All Nodes  . . . . . . . . . . 22
       3.4.6.  Routing functionality  . . . . . . . . . . . . . . . . 23
       3.4.7.  Self-Organising  . . . . . . . . . . . . . . . . . . . 25
       3.4.8.  Fewest Topology Assumptions  . . . . . . . . . . . . . 27
       3.4.9.  Naming and Service Discovery . . . . . . . . . . . . . 27
       3.4.10. Proxy or Extend? . . . . . . . . . . . . . . . . . . . 28
       3.4.11. Adapt to ISP constraints . . . . . . . . . . . . . . . 28
     3.5.  Summary of Homenet Architecture Recommendations  . . . . . 29
     3.6.  Implementing the Architecture on IPv6  . . . . . . . . . . 29
   4.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     4.1.  Normative References . . . . . . . . . . . . . . . . . . . 29
     4.2.  Informative References . . . . . . . . . . . . . . . . . . 30
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 33
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33





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1.  Introduction

   This document focuses on evolving networking technology within small
   "residential home" networks and the associated challenges.  For
   example, a trend in home networking is 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 need for
   multiple subnets, for example for private and guest networks, the
   introduction of IPv6, and the introduction of specialized networks
   for home automation and sensors.

   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 "not
   actively managed".  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.

   This architecture 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.
   Future deployments, or specific subnets within an otherwise dual-
   stack home network, may be IPv6-only.

   [RFC6204] defines basic requirements for customer edge routers
   (CERs).  The scope of this text is the homenet, and thus the internal
   facing interface described in RFC 6204 as well as 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.

   Discussion in the homenet WG has led to a suggestion that there
   should be a baseline homenet "version 1" architecture, based on
   protocols and implementations that are as far as possible proven and
   robust.  A future architecture may incorporate more advanced
   elements.  Feedback is sought on what if anything do we want to say
   about potential homenet versions here.





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1.1.  Terminology and Abbreviations

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

   o  CER: Customer Edge Router.  The border router at the edge of the
      homenet.

   o  LLN: Low-power and lossy network.

   o  NAT: Network Address Translation.  Typically referring to Network
      Address and Port Translation (NAPT).

   o  NPTv6: Network Prefix Translation for IPv6 [RFC6296].

   o  PCP: Port Control Protocol [I-D.ietf-pcp-base].

   o  ULA: Unique Local Addresses [RFC4193].

   o  uPnP: Universal Plug and Play.

   o  VM: Virtual machine.


2.  Effects of IPv6 on Home Networking

   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 areas impacted by the introduction of
   IPv6 into the home network that are both promising and problematic.

2.1.  Multiple subnets and routers

   Simple layer 3 topologies involving as few subnets as possible are
   preferred in home networks for a variety of reasons including simpler
   management and service discovery.  However, the incorporation of
   dedicated (routed) subnets remains necessary for a variety of
   reasons.

   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



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   those used for certain types of sensor devices.  Similar needs for
   subnetting may occur in other cases, such as separating building
   control or corporate extensions from the Internet access network.
   Also, different subnets may be associated with parts of the homenet
   that have different routing and security policies.

   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].

   In addition to routing, rather than NATing, between subnets, there
   are issues of when and how to extend mechanisms such as service
   discovery which currently rely on link-local addressing to limit
   scope.

   The presence of a multiple subnet, multi-router network implies that
   there is some kind of automatic routing mechanism in place.  In
   advanced configurations similar to those used in multihomed corporate
   networks, there may also be a need to discover border router(s) by an
   appropriate mechanism.

2.2.  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.  Thus it
   should be considered the norm for devices on IPv6 home networks to be
   multi-addressed, and to also have an IPv4 address where the network
   is dual-stack.  Default address selection mechanisms
   [I-D.ietf-6man-rfc3484-revise] allow a node to select appropriate
   src/dst address pairs for communications, though such selection may
   face problems in the event of multihoming, where nodes will be
   configured with one address from each upstream ISP prefix, and the
   presence of upstream ingress filtering thus requires multi-addressed
   nodes to select the right source address to be used for the
   corresponding uplink.

2.3.  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 communication between devices within
   the network.  ULAs have the potential to be used for stable
   addressing in a home network where the 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.  However, it is undesirable to
   aggressively deprecate global prefixes for temporary loss of



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   connectivity, so for this to matter there would have to be a
   connection breakage longer than the lease period, and even then,
   deprecating prefixes when there is no connectivity may not be
   advisable.  However, while setting a network up there may be a period
   with no connectivity.

   Another possible reason for using ULAs would be to provide an
   indication to applications that the traffic is local.  This could
   then be used with security settings to designate where a particular
   application is allowed to connect to.

   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.

   Address selection mechanisms should ensure a ULA source address is
   used to communicate with ULA destination addresses.  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
   global IPv6 source address.

2.4.  Security, Borders, and the 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 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
   both 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.

   In IPv4 NAT networks, the NAT provides an implicit firewall function.
   [RFC4864] 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 then need to signal that desire
   through a protocol such as uPNP or PCP [I-D.ietf-pcp-base].  In
   networks with multiple CERs, PCP will need to handle the cases of
   flows that may use one or both exit routers.

   Such an approach would reduce the efficacy of end-to-end connectivity



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   that IPv6 has the potential to restore, since the need for IPv4 NAT
   traversal is replaced by a need to use a signalling protocol to
   request a firewall hole be opened.  [RFC6092] provides
   recommendations for an IPv6 firewall that applies "limitations on
   end-to-end transparency where security considerations are deemed
   important to promote local and Internet security."  The firewall
   operation is "simple" in that there is an assumption that traffic
   which is to be blocked by default is defined in the RFC and not
   expected to be updated by the user or otherwise.  The RFC does
   however state that CERs should have an option to be put into a
   "transparent mode" of operation.

   It is important to distinguish between addressability and
   reachability; i.e. while IPv6 offers global addressability through
   use of globally unique addresses in the home, whether they are
   globally reachable or not would depend on firewall or filtering
   configuration, and not the presence or use of NAT.

   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 is much like a virus-
   scanning tool which must receive updates in order to detect and/or
   neutralize the latest attacks as they arrive.  As the name implies
   "advanced" security requires significantly more resources and
   infrastructure (including a source for attack signatures) in
   comparison to "simple" security.

   In addition to establishing the security mechanisms themselves, it is
   important to know where to enable them.  If there is some indication
   as to which router is connected to the "outside" of the home network,
   this is feasible.  Otherwise, it can be difficult to know which
   security policies to apply where.  Further, security policies may be
   different for various address ranges if ULA addressing is setup to
   only operate within the homenet itself and not be routed to the
   Internet at large.  Finally, such 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.

   It may be useful to classify the 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



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   discovery.

2.5.  Naming, and manual configuration of IP addresses

   In IPv4, a single subnet NATed home network environment is currently
   the norm.  As a result, it is for example common practice for users
   to be able to connect to a router for configuration via a literal
   address such as 192.168.1.1 or some other commonly used RFC 1918
   address.  In IPv6, while ULAs exist and could potentially be used to
   address internally-reachable services, little deployment experience
   exists to date.  Given a true ULA prefix is effectively a random 48-
   bit prefix, it is not reasonable to expect users to manually enter
   such address literals for configuration or other purposes.  As such,
   even for the simplest of functions, naming and the associated
   discovery of services is imperative for easy administration of the
   homenet.

   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.


3.  Architecture

   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 realizing 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
   Section 3.6.

3.1.  Network Models

   In this section we list six network models.

   A)  Single ISP, Single CER, Single subnet







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   B)  Single ISP, Single CER, Multiple subnets

   C)  Single ISP, Single CER, Multiple internal routers

   D)  Two ISPs, Two CERs, Shared subnets with multiple internal routers

   E)  Two ISPs, One CER, Isolated subnets with multiple internal
       routers

   F)  Two ISPs, One CER, Shared subnets with multiple internal routers

   The models are presented to frame the discussion as to which models
   are in scope for the homenet architecture, and which multi-homing
   requirements should be met in the architecture.

3.1.1.  A: Single ISP, Single CER, Single subnet

   Figure 1 shows the simplest possible home network topology, involving
   just one router, a local area network, and a set of hosts.  Setting
   up such networks is in principle well understood today [RFC6204].































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                +-------+-------+                      \
                |   Service     |                       \
                |   Provider    |                        | Service
                |    Router     |                        | Provider
                +-------+-------+                        | network
                        |                               /
                        | Customer                     /
         demarc #1 -->  | Internet connection         /
                        |
                 +------+--------+                    \
                 |     IPv6      |                     \
                 | Customer Edge |                      \
                 |    Router     |                      /
                 +------+--------+                     /
                        |                             |
         demarc #2 -->  |                             | End-User
                        |   Local network             | network(s)
               ---+-----+-------+---                   \
                  |             |                       \
             +----+-----+ +-----+----+                   \
             |IPv6 Host | |IPv6 Host |                   /
             |          | |          |                  /
             +----------+ +-----+----+                 /

                                 Figure 1

   Two possible demarcation points are illustrated in Figure 1, which
   indicate which party is responsible for configuration or
   autoconfiguration.  Demarcation #1 makes the Customer Edge Router the
   responsibility of the customer.  This is only practical if the
   Customer Edge Router can function with factory defaults installed.
   The Customer Edge Router may be pre-configured by the ISP, or by the
   home user by some suitably simple method.  Demarcation #2 makes the
   Customer Edge Router the responsibility of the provider.  Both models
   of operation must be supported in the homenet architecture, including
   the scenarios below with multiple ISPs and demarcation points.

3.1.2.  B: Single ISP, Single CER, Multiple subnets

   Figure 2 shows another network that now introduces multiple local
   area networks.  These may be needed for reasons relating to different
   link layer technologies in use or for policy reasons.  A common
   arrangement is to have different link types supported on the same
   router, bridged together.  This example however presents two subnets.
   This could be classic Ethernet in the one subnet and a LLN link layer
   technology in the other subnet.

   This topology is also relatively well understood today [RFC6204],



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   though it certainly presents additional demands with regards to
   suitable firewall policies and limits the operation of certain
   applications and discovery mechanisms (which may typically today only
   succeed within a single subnet).


                      +-------+-------+                    \
                      |   Service     |                     \
                      |   Provider    |                      | Service
                      |    Router     |                      | Provider
                      +------+--------+                      | network
                             |                              /
                             | Customer                    /
                             | Internet connection        /
                             |
                      +------+--------+                     \
                      |     IPv6      |                      \
                      | Customer Edge |                       \
                      |    Router     |                       /
                      +----+-------+--+                      /
           Network A       |       |   Network B            | End-User
     ---+-------------+----+-    --+--+-------------+---    | network(s)
        |             |               |             |        \
   +----+-----+ +-----+----+     +----+-----+ +-----+----+    \
   |IPv6 Host | |IPv6 Host |     | IPv6 Host| |IPv6 Host |    /
   |          | |          |     |          | |          |   /
   +----------+ +----------+     +----------+ +----------+  /

                                 Figure 2

3.1.3.  C: Single ISP, Single CER, Multiple internal subnets

   Figure 3 shows a little bit more complex network with two routers and
   eight devices connected to one ISP.  This network is similar to the
   one discussed in [I-D.ietf-v6ops-ipv6-cpe-router-bis].  The main
   complication in this topology compared to the ones described earlier
   is that there is no longer a single router that a priori understands
   the entire topology.  The topology itself may also be complex.  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.  In the following sections
   we discuss support for arbitrary topologies.









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                     +-------+-------+                     \
                     |   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 3













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3.1.4.  D: Two ISPs, Two CERs, Shared subnets with multiple internal
        routers


           +-------+-------+     +-------+-------+         \
           |   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 4

   Figure 4 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 3 to create a more complex scenario with subnets that my be
   behind multiple internal routers.















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3.1.5.  E: Two ISPs, One CER, Isolated subnets with multiple internal
        routers


           +-------+-------+     +-------+-------+         \
           |   Service     |     |   Service     |          \
           |  Provider A   |     |  Provider B   |           | Service
           |    Router     |     |    Router     |           | Provider
           +-------+-------+     +-------+-------+           | network
                    |                 |                     /
                    |    Customer     |                   /
                    |    Internet     |                  /
                    |   connections   |                 |
                   +---------+---------+                 \
                   |       IPv6        |                   \
                   |   Customer Edge   |                    \
                   |     Router 1      |                    /
                   +---------+---------+                   /
                      |             |                     /
                      |             |                     | End-User
     ---+---------+---+--           --+--+----------+---  | network(s)
        |             |               |             |      \
   +----+-----+ +-----+----+     +----+-----+ +-----+----+  \
   |IPv6 Host | |IPv6 Host |     | IPv6 Host| |IPv6 Host |  /
   |          | |          |     |          | |          | /
   +----------+ +----------+     +----------+ +----------+

                                 Figure 5

   Figure 5 illustrates a model where a home network may have multiple
   connections to multiple providers or multiple logical connections to
   the same provider, but the associated subnet(s) are isolated.  Some
   deployment scenarios may require this model.


















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3.1.6.  F: Two ISPs, One CER, Shared subnets with multiple internal
        routers


           +-------+-------+     +-------+-------+         \
           |   Service     |     |   Service     |          \
           |  Provider A   |     |  Provider B   |           | Service
           |    Router     |     |    Router     |           | Provider
           +-------+-------+     +-------+-------+           | network
                    |                 |                     /
                    |    Customer     |                   /
                    |    Internet     |                  /
                    |   connections   |                 |
                   +---------+---------+                 \
                   |       IPv6        |                   \
                   |   Customer Edge   |                    \
                   |     Router 1      |                    /
                   +---------+---------+                   /
                       |            |                     /
                       |            |                     | End-User
     ---+------------+-+------------+-+-------------+---  | network(s)
        |            |                |             |      \
   +----+-----+ +----+-----+     +----+-----+ +-----+----+  \
   |IPv6 Host | |IPv6 Host |     | IPv6 Host| |IPv6 Host |  /
   |          | |          |     |          | |          | /
   +----------+ +----------+     +----------+ +----------+

                                 Figure 6

   Figure 6 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, that may be multiple
   layers deep.

3.2.  Determining the Requirements

   [RFC6204] defines "basic" requirements for IPv6 Customer Edge
   Routers, while [I-D.ietf-v6ops-ipv6-cpe-router-bis] describes
   "advanced" features.  In general, home network equipment needs to
   cope with the different types of network 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

   o  Prefix configuration for routers

   o  Managing routing




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   o  Name resolution

   o  Service discovery

   o  Network security

   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.

3.3.  Considerations

   This section lists some considerations for home networking that may
   affect the architecture and associated requirements.

3.3.1.  Multihoming

   A homenet may be multihomed to multiple providers.  This may either
   take a form where there are multiple isolated networks within the
   home (see Network Model E above) or a more integrated network where
   the connectivity selection is dynamic (see Network Model D or F
   above).  Current practice is typically of the former kind, but the
   latter is expected to become more commonplace.

   There are some specific 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.  Second, one upstream may be a
   "walled garden", and thus only appropriate to be used for
   connectivity to the services of that provider.

   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
   Models E and F have a single CER and thus could perform source
   routing at the single network exit point.

   The general approach for IPv6 multihoming is for a hosts 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
   [RFC6296], a prefix translation-based mechanism, at the edge.  This
   obviously comes at some architectural cost, which is why approaches
   such as [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.  Host-based methods such



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   as Shim6 [RFC5533] have also been defined, but of course require
   support in the hosts.

   If multihoming is supported 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.

   The current set of assumptions and requirements proposed by the
   homenet architecture team is:

   MH1)  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.

   MH2)  Single CER Network Models E and F are in scope, and may be
         solved by source routing at the CER.

   MH3)  It is desirable to avoid deployment of NPTv6 at the CER.  Hosts
         should be multi-addressed from each ISP they may communicate
         with or through.

   MH4)  Solutions that involve host changes should be avoided.

   MH5)  Walled garden multihoming is in scope.

   MH6)  Transition method sunsetting is in scope.  The topic of
         multihoming with specific (6rd) transition coexistence is
         discussed in [I-D.townsley-troan-ipv6-ce-transitioning].

   MH7)  "Just" picking the right source address to use to fall foul of
         ingress filtering on upstream ISP connections (as per Network
         Model D) is not a trivial task.  A solution is highly
         desirable, but out of scope of homenet.

   MH8)  Source routing throughout the homenet, a la
         [I-D.baker-fun-multi-router], requires relatively significant
         routing changes.  The network should "guarantee" routing the
         packet to the correct exit given the source address, but hosts
         are responsible for anything extra, e.g. detecting failure, or
         choosing a new src/dst address combination.

   Feedback is sought on the above points.





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3.3.2.  Quality of Service in multi-service home networks

   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 QoS 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.

   There may also be complementary mechanisms that could be beneficial
   in the homenet domain, such as ensuring proper buffering algorithms
   are used as described in [Gettys11].

3.3.3.  Privacy considerations

   There are no specific privacy concerns for 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, e.g. between restructuring of an ISPs
   residential network provision.

3.4.  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.  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.

   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.

3.4.1.  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.




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   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.

   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.
   [I-D.baker-fun-routing-class] suggests introducing a routing protocol
   that may route on both source and destination addresses, which would
   be a significant change compared to current practices.

   Liaisons with other appropriate standards groups and related
   organisations is desirable, e.g. the IEEE and Wi-Fi Alliance.

3.4.2.  Dual-stack Operation

   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.

   Running IPv6-only may require documentation of additional
   considerations such as:

      Ensuring there is a way to access content in the IPv4 Internet.
      This can be arranged through incorporating NAT64 [RFC6144]
      functionality in the home gateway router, for instance.

      DNS discovery mechanisms are enabled for IPv6.  Both stateless
      DHCPv6 [RFC3736] [RFC3646] and Router Advertisement options
      [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.

      All nodes in the home network support operations in IPv6-only
      mode.  Some current devices work well with dual-stack but fail to
      recognize connectivity when IPv4 DHCP fails, for instance.

   In dual-stack networks, solutions for IPv6 must not adversely affect
   IPv4 operation.  It is likely that topologies of IPv4 and IPv6



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   networks would be as congruent as possible.

   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.

3.4.3.  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.

   Future home networks are highly likely to 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 a private and visitor parts of the network.

   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.

   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.

3.4.4.  Transparent End-to-End Communications

   An IPv6-based home network architecture should naturally offer a
   transparent end-to-end communications model.  Each device should be
   addressable by a unique address.  Security perimeters can of course
   restrict the end-to-end communications, but it is simpler given the
   availability of globally unique addresses to block certain nodes from
   communicating by use of an appropriate filtering device than to
   configure the address translation device to enable appropriate
   address/port forwarding in the presence of a NAT.



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   As discussed previously, it is important to note the difference
   between hosts being addressable and reachable.  Thus filtering is to
   be expected, while host-based IPv6 NAT is not.  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.

   When configuring filters, protocols for securely associating devices
   are desirable.  In the presence of "Simple Security" the use of
   signalling protocols such as uPnP or PCP may be expected to punch
   holes in the firewall (and be able to handle cases where there are
   multiple CERs/firewall(s).  Alternatively, RFC 6092 supports the
   option for a border CER to run in "transparent mode", in which case a
   protocol like PCP is not required, but the security model is more
   open.

3.4.5.  IP Connectivity between All Nodes

   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.

   Local addressing (ULAs) may be used within the scope of a home
   network.  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.

   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).  Note
   that certain scenarios may require co-existence of ISP connectivity
   providing a general Internet service with provider connectivity to a
   private "walled garden" network.

   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).




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   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.

3.4.6.  Routing functionality

   Routing functionality is required when there are multiple routers in
   use.  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.

   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.

   In this section we list the requirements and assumptions for routing
   functionality within the homenet environment.

   RT1)   The protocol should preferably be an existing deployed
          protocol that has been proven to be reliable and robust.

   RT2)   It is preferable that the protocol is "lightweight".

   RT3)   The protocol should provide reachability between all nodes in
          the homement.

   RT4)   In general, LLN or other networks should be able to attach and
          participate the same way or map/be gatewayed to the main
          homenet.

   RT5)   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 tested 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 optimizing communication in the homenet.

   RT6)   Minimizing 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.





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   RT7)   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.

   RT8)   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, and 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.

   RT9)   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
          [I-D.acee-ospf-ospfv3-autoconfig].  The exception is
          configuration of a "secret" for authentication methods.  It is
          important that self-configuration with "unintended" devices is
          avoided.

   RT10)  The protocol should not require upstream ISP connectivity to
          be established to continue routing within the homenet.

   RT11)  Multiple upstreams should be supported, as described in the
          Network Models earlier.

   RT12)  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.

   RT13)  The routing system should support walled garden environments.

   RT14)  Load-balancing to multiple providers is not a requirement, but
          failover from a primary to a backup link when available must
          be a requirement.







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   RT15)  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.

   A new I-D has been published on homenet routing requirements, see
   [I-D.howard-homenet-routing-comparison] and evaluations of common
   routing protocols made against those requirements, see
   [I-D.howard-homenet-routing-requirements].  The requirements from the
   former document have been worked into this architecture text.
   Feedback is sought on how these documents move forward.

3.4.7.  Self-Organising

   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.

   The most important function in this respect is prefix delegation and
   management.  The requirements and assumptions for the prefix
   delegation function are summarised as follows:

   PD1)   From the homenet perspective, a single prefix should be
          received on the border CER [RFC3633].  The ISP should only see
          that aggregate, and not single /64 prefixes allocated within
          the homenet.

   PD2)   Each link in the homenet should receive a prefix from within
          the ISP-provided prefix.

   PD3)   Delegation should be autonomous, and not assume a flat or
          hierarchical model.

   PD4)   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.

   PD5)   Duplicate assignment of multiple /64s to the same network
          should be avoided.

   PD6)   The network should behave as gracefully as possible in the
          event of prefix exhaustion.






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   PD7)   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.

   PD8)   Where ULAs are used, most likely but not necessarily in
          parallel with global prefixes, one router will need to be
          elected as the generator of ULA prefixes for the homenet.

   PD9)   Delegation within the homenet should give each link a prefix
          that is persistent across reboots, power outages and similar
          short-term outages.

   PD10)  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.

   PD11)  Persistence should not depend on router boot order.

   PD12)  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).

   PD13)  The delegation method should support "flash" renumbering.

   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/
   assumptions listed above.

   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.

   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, site scope multicast
   boundaries and where firewall policies may be applied.



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   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.

3.4.8.  Fewest Topology Assumptions

   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.

   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.

3.4.9.  Naming and Service Discovery

   The most natural way to think about naming and service discovery
   within a homenet is to enable it to work across the entire residence,
   disregarding technical borders such as subnets but respecting policy
   borders such as those between visitor and internal networks.

   Homenet naming systems will be required that work internally or
   externally, though the domains used may be different from those
   different perspectives.

   A desirable target may be a fully functional self-configuring secure
   local DNS service so that all devices are referred to by name, and
   these FQDNs are resolved locally.  This would make clean use of ULAs
   and multiple ISP-provided prefixes much easier.  The 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.

   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.

   With the introduction of new 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.

   It is also important to note here that there is also potential
   ambiguity if a mobile device should move between two local name



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   spaces called ".home", for example.

   For service discovery, support may be required for IPv6 multicast
   across the scope of the home network, and thus at least all routing
   devices in the network.

3.4.10.  Proxy or Extend?

   Related to the above, we believe that general existing discovery
   protocols 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.

   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.

3.4.11.  Adapt to ISP constraints

   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 frequently.  The home network needs to be adaptable to
   such ISP policies, e.g. on constraints placed by the size of prefix
   offered by the ISP.  The ISP may use [I-D.ietf-dhc-pd-exclude] for
   example.

   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.

   It is expected that ISPs will deliver a relatively stable home prefix
   to customers.  The norm for residential customers of large ISPs may
   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.

   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 without a "flag day".  The customer may of course also
   choose to move to a new ISP, and thus begin using a new prefix.  Thus
   it's desirable that homenet protocols or operational processes don't
   add unnecessary complexity for renumbering.



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   The 6renum WG is studying IPv6 renumbering for enterprise networks.
   It is not currently targetting homenets, but may produce outputs that
   are relevant.

3.5.  Summary of Homenet Architecture Recommendations

   Feedback sought on whether a summary section would be useful.

3.6.  Implementing the Architecture on IPv6

   The necessary mechanisms are largely already part of the IPv6
   protocol set and common implementations, though there are some
   exceptions.  For automatic routing, it is expected that 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.  Support
   for multiple exit routers and multi-homing would also require
   extensions, even if focused on the problem of multi-addressed hosts
   selecting the right source address to avoid falling foul of ingress
   filtering on upstream ISP connections.

   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.

   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 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.  References

4.1.  Normative References

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, December 1998.




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   [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.

   [RFC4192]  Baker, F., Lear, E., and R. Droms, "Procedures for
              Renumbering an IPv6 Network without a Flag Day", RFC 4192,
              September 2005.

   [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.

   [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.

   [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.

   [RFC6296]  Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
              Translation", RFC 6296, June 2011.

4.2.  Informative References

   [RFC3646]  Droms, R., "DNS Configuration options for Dynamic Host
              Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
              December 2003.

   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol



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              (DHCP) Service for IPv6", RFC 3736, April 2004.

   [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.

   [I-D.baker-fun-multi-router]
              Baker, F., "Exploring the multi-router SOHO network",
              draft-baker-fun-multi-router-00 (work in progress),
              July 2011.

   [I-D.townsley-troan-ipv6-ce-transitioning]
              Townsley, M. and O. Troan, "Basic Requirements for
              Customer Edge Routers - multihoming and transition",
              draft-townsley-troan-ipv6-ce-transitioning-02 (work in
              progress), December 2011.

   [I-D.baker-fun-routing-class]
              Baker, F., "Routing a Traffic Class",
              draft-baker-fun-routing-class-00 (work in progress),
              July 2011.

   [I-D.howard-homenet-routing-comparison]
              Howard, L., "Evaluation of Proposed Homenet Routing
              Solutions", draft-howard-homenet-routing-comparison-00
              (work in progress), December 2011.

   [I-D.howard-homenet-routing-requirements]
              Howard, L., "Homenet Routing Requirements",
              draft-howard-homenet-routing-requirements-00 (work in
              progress), December 2011.

   [I-D.herbst-v6ops-cpeenhancements]
              Herbst, T. and D. Sturek, "CPE Considerations in IPv6
              Deployments", draft-herbst-v6ops-cpeenhancements-00 (work
              in progress), October 2010.

   [I-D.vyncke-advanced-ipv6-security]
              Vyncke, E., Yourtchenko, A., and M. Townsley, "Advanced
              Security for IPv6 CPE",
              draft-vyncke-advanced-ipv6-security-03 (work in progress),
              October 2011.

   [I-D.ietf-v6ops-ipv6-cpe-router-bis]
              Singh, H., Beebee, W., Donley, C., Stark, B., and O.



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              Troan, "Advanced Requirements for IPv6 Customer Edge
              Routers", draft-ietf-v6ops-ipv6-cpe-router-bis-01 (work in
              progress), July 2011.

   [I-D.ietf-6man-rfc3484-revise]
              Matsumoto, A., Kato, J., Fujisaki, T., and T. Chown,
              "Update to RFC 3484 Default Address Selection for IPv6",
              draft-ietf-6man-rfc3484-revise-05 (work in progress),
              October 2011.

   [I-D.ietf-dhc-pd-exclude]
              Korhonen, J., Savolainen, T., Krishnan, S., and O. Troan,
              "Prefix Exclude Option for DHCPv6-based Prefix
              Delegation", draft-ietf-dhc-pd-exclude-04 (work in
              progress), December 2011.

   [I-D.v6ops-multihoming-without-ipv6nat]
              Troan, O., Miles, D., Matsushima, S., Okimoto, T., and D.
              Wing, "IPv6 Multihoming without Network Address
              Translation", draft-v6ops-multihoming-without-ipv6nat-00
              (work in progress), March 2011.

   [I-D.baker-homenet-prefix-assignment]
              Baker, F. and R. Droms, "IPv6 Prefix Assignment in Small
              Networks", draft-baker-homenet-prefix-assignment-00 (work
              in progress), October 2011.

   [I-D.arkko-homenet-prefix-assignment]
              Arkko, J. and A. Lindem, "Prefix Assignment in a Home
              Network", draft-arkko-homenet-prefix-assignment-01 (work
              in progress), October 2011.

   [I-D.acee-ospf-ospfv3-autoconfig]
              Lindem, A. and J. Arkko, "OSPFv3 Auto-Configuration",
              draft-acee-ospf-ospfv3-autoconfig-00 (work in progress),
              October 2011.

   [I-D.ietf-pcp-base]
              Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)",
              draft-ietf-pcp-base-22 (work in progress), January 2012.

   [I-D.chakrabarti-homenet-prefix-alloc]
              Nordmark, E., Chakrabarti, S., Krishnan, S., and W.
              Haddad, "Simple Approach to Prefix Distribution in Basic
              Home Networks", draft-chakrabarti-homenet-prefix-alloc-01
              (work in progress), October 2011.




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   [Gettys11]
              Gettys, J., "Bufferbloat: Dark Buffers in the Internet",
              March 2011,
              <http://www.ietf.org/proceedings/80/slides/tsvarea-1.pdf>.


Appendix A.  Acknowledgments

   The authors would like to thank Brian Carpenter, Mark Andrews, Fred
   Baker, Ray Bellis, Cameron Byrne, 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, Erik Nordmark, Michael Richardson, Barbara Stark,
   Sander Steffann, Dave Thaler, JP Vasseur, Curtis Villamizar, 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.


Authors' Addresses

   Jari Arkko
   Ericsson
   Jorvas  02420
   Finland

   Email: jari.arkko@piuha.net


   Anders Brandt
   Sigma Designs
   Emdrupvej 26A, 1
   Copenhagen  DK-2100
   Denmark

   Email: abr@sdesigns.dk


   Tim Chown
   University of Southampton
   Highfield
   Southampton, Hampshire  SO17 1BJ
   United Kingdom

   Email: tjc@ecs.soton.ac.uk





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   Jason Weil
   Time Warner Cable
   13820 Sunrise Valley Drive
   Herndon, VA  20171
   USA

   Email: jason.weil@twcable.com


   Ole Troan
   Cisco Systems, Inc.
   Drammensveien 145A
   Oslo  N-0212
   Norway

   Email: ot@cisco.com



































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