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rfc:rfc7084

Internet Engineering Task Force (IETF) H. Singh Request for Comments: 7084 W. Beebee Obsoletes: 6204 Cisco Systems, Inc. Category: Informational C. Donley ISSN: 2070-1721 CableLabs

                                                              B. Stark
                                                                  AT&T
                                                         November 2013
         Basic Requirements for IPv6 Customer Edge Routers

Abstract

 This document specifies requirements for an IPv6 Customer Edge (CE)
 router.  Specifically, the current version of this document focuses
 on the basic provisioning of an IPv6 CE router and the provisioning
 of IPv6 hosts attached to it.  The document also covers IP transition
 technologies.  Two transition technologies in RFC 5969's IPv6 Rapid
 Deployment on IPv4 Infrastructures (6rd) and RFC 6333's Dual-Stack
 Lite (DS-Lite) are covered in the document.  The document obsoletes
 RFC 6204.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7084.

Singh, et al. Informational [Page 1] RFC 7084 IPv6 CE Router Requirements November 2013

Copyright Notice

 Copyright (c) 2013 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................3
    1.1. Requirements Language ......................................3
 2. Terminology .....................................................4
 3. Architecture ....................................................5
    3.1. Current IPv4 End-User Network Architecture .................5
    3.2. IPv6 End-User Network Architecture .........................5
         3.2.1. Local Communication .................................7
 4. Requirements ....................................................7
    4.1. General Requirements .......................................7
    4.2. WAN-Side Configuration .....................................8
    4.3. LAN-Side Configuration ....................................12
    4.4. Transition Technologies Support ...........................14
         4.4.1. 6rd ................................................14
         4.4.2. Dual-Stack Lite (DS-Lite) ..........................15
    4.5. Security Considerations ...................................16
 5. Acknowledgements ...............................................17
 6. Contributors ...................................................17
 7. References .....................................................18
    7.1. Normative References ......................................18
    7.2. Informative References ....................................20

Singh, et al. Informational [Page 2] RFC 7084 IPv6 CE Router Requirements November 2013

1. Introduction

 This document defines basic IPv6 features for a residential or small-
 office router, referred to as an "IPv6 CE router", in order to
 establish an industry baseline for features to be implemented on such
 a router.
 These routers typically also support IPv4.
 Mixed environments of dual-stack hosts and IPv6-only hosts (behind
 the CE router) can be more complex if the IPv6-only devices are using
 a translator to access IPv4 servers [RFC6144].  Support for such
 mixed environments is not in scope of this document.
 This document specifies how an IPv6 CE router automatically
 provisions its WAN interface, acquires address space for provisioning
 of its LAN interfaces, and fetches other configuration information
 from the service provider network.  Automatic provisioning of more
 complex topology than a single router with multiple LAN interfaces is
 out of scope for this document.
 See [RFC4779] for a discussion of options available for deploying
 IPv6 in service provider access networks.
 The document also covers the IP transition technologies that were
 available at the time this document was written.  Two transition
 technologies in 6rd [RFC5969] and DS-Lite [RFC6333] are covered in
 the document.

1.1. Requirements Language

 Take careful note: Unlike other IETF documents, the key words "MUST",
 "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
 "RECOMMENDED", "MAY", and "OPTIONAL" in this document are not used as
 described in RFC 2119 [RFC2119].  This document uses these keywords
 not strictly for the purpose of interoperability, but rather for the
 purpose of establishing industry-common baseline functionality.  As
 such, the document points to several other specifications (preferable
 in RFC or stable form) to provide additional guidance to implementers
 regarding any protocol implementation required to produce a
 successful CE router that interoperates successfully with a
 particular subset of currently deploying and planned common IPv6
 access networks.

Singh, et al. Informational [Page 3] RFC 7084 IPv6 CE Router Requirements November 2013

2. Terminology

 End-User Network          one or more links attached to the IPv6 CE
                           router that connect IPv6 hosts.
 IPv6 Customer Edge Router a node intended for home or small-office
                           use that forwards IPv6 packets not
                           explicitly addressed to itself.  The IPv6
                           CE router connects the end-user network to
                           a service provider network.
 IPv6 Host                 any device implementing an IPv6 stack
                           receiving IPv6 connectivity through the
                           IPv6 CE router.
 LAN Interface             an IPv6 CE router's attachment to a link in
                           the end-user network.  Examples are
                           Ethernet (simple or bridged), 802.11
                           wireless, or other LAN technologies.  An
                           IPv6 CE router may have one or more
                           network-layer LAN interfaces.
 Service Provider          an entity that provides access to the
                           Internet.  In this document, a service
                           provider specifically offers Internet
                           access using IPv6, and it may also offer
                           IPv4 Internet access.  The service provider
                           can provide such access over a variety of
                           different transport methods such as DSL,
                           cable, wireless, and others.
 WAN Interface             an IPv6 CE router's attachment to a link
                           used to provide connectivity to the service
                           provider network; example link technologies
                           include Ethernet (simple or bridged), PPP
                           links, Frame Relay, or ATM networks, as
                           well as Internet-layer (or higher-layer)
                           "tunnels", such as tunnels over IPv4 or
                           IPv6 itself.

Singh, et al. Informational [Page 4] RFC 7084 IPv6 CE Router Requirements November 2013

3. Architecture

3.1. Current IPv4 End-User Network Architecture

 An end-user network will likely support both IPv4 and IPv6.  It is
 not expected that an end user will change their existing network
 topology with the introduction of IPv6.  There are some differences
 in how IPv6 works and is provisioned; these differences have
 implications for the network architecture.  A typical IPv4 end-user
 network consists of a "plug and play" router with NAT functionality
 and a single link behind it, connected to the service provider
 network.
 A typical IPv4 NAT deployment by default blocks all incoming
 connections.  Opening of ports is typically allowed using a Universal
 Plug and Play Internet Gateway Device (UPnP IGD) [UPnP-IGD] or some
 other firewall control protocol.
 Another consequence of using private address space in the end-user
 network is that it provides stable addressing; that is, it never
 changes even when you change service providers, and the addresses are
 always there even when the WAN interface is down or the customer edge
 router has not yet been provisioned.
 Many existing routers support dynamic routing (which learns routes
 from other routers), and advanced end-users can build arbitrary,
 complex networks using manual configuration of address prefixes
 combined with a dynamic routing protocol.

3.2. IPv6 End-User Network Architecture

 The end-user network architecture for IPv6 should provide equivalent
 or better capabilities and functionality than the current IPv4
 architecture.

Singh, et al. Informational [Page 5] RFC 7084 IPv6 CE Router Requirements November 2013

 The end-user network is a stub network.  Figure 1 illustrates the
 model topology for the end-user network.
                 +-------+-------+                      \
                 |   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 1: An Example of a Typical End-User Network
 This architecture describes the:
 o  Basic capabilities of an IPv6 CE router
 o  Provisioning of the WAN interface connecting to the service
    provider
 o  Provisioning of the LAN interfaces
 For IPv6 multicast traffic, the IPv6 CE router may act as a Multicast
 Listener Discovery (MLD) proxy [RFC4605] and may support a dynamic
 multicast routing protocol.
 The IPv6 CE router may be manually configured in an arbitrary
 topology with a dynamic routing protocol.  Automatic provisioning and
 configuration are described for a single IPv6 CE router only.

Singh, et al. Informational [Page 6] RFC 7084 IPv6 CE Router Requirements November 2013

3.2.1. Local Communication

 Link-local IPv6 addresses are used by hosts communicating on a single
 link.  Unique Local IPv6 Unicast Addresses (ULAs) [RFC4193] are used
 by hosts communicating within the end-user network across multiple
 links, but without requiring the application to use a globally
 routable address.  The IPv6 CE router defaults to acting as the
 demarcation point between two networks by providing a ULA boundary, a
 multicast zone boundary, and ingress and egress traffic filters.
 At the time of this writing, several host implementations do not
 handle the case where they have an IPv6 address configured and no
 IPv6 connectivity, either because the address itself has a limited
 topological reachability (e.g., ULA) or because the IPv6 CE router is
 not connected to the IPv6 network on its WAN interface.  To support
 host implementations that do not handle multihoming in a multi-prefix
 environment [MULTIHOMING-WITHOUT-NAT], the IPv6 CE router should not,
 as detailed in the requirements below, advertise itself as a default
 router on the LAN interface(s) when it does not have IPv6
 connectivity on the WAN interface or when it is not provisioned with
 IPv6 addresses.  For local IPv6 communication, the mechanisms
 specified in [RFC4191] are used.
 ULA addressing is useful where the IPv6 CE router has multiple LAN
 interfaces with hosts that need to communicate with each other.  If
 the IPv6 CE router has only a single LAN interface (IPv6 link), then
 link-local addressing can be used instead.
 Coexistence with IPv4 requires any IPv6 CE router(s) on the LAN to
 conform to these recommendations, especially requirements ULA-5 and
 L-4 below.

4. Requirements

4.1. General Requirements

 The IPv6 CE router is responsible for implementing IPv6 routing; that
 is, the IPv6 CE router must look up the IPv6 destination address in
 its routing table to decide to which interface it should send the
 packet.
 In this role, the IPv6 CE router is responsible for ensuring that
 traffic using its ULA addressing does not go out the WAN interface
 and does not originate from the WAN interface.

Singh, et al. Informational [Page 7] RFC 7084 IPv6 CE Router Requirements November 2013

 G-1:  An IPv6 CE router is an IPv6 node according to the IPv6 Node
       Requirements specification [RFC6434].
 G-2:  The IPv6 CE router MUST implement ICMPv6 according to
       [RFC4443].  In particular, point-to-point links MUST be handled
       as described in Section 3.1 of [RFC4443].
 G-3:  The IPv6 CE router MUST NOT forward any IPv6 traffic between
       its LAN interface(s) and its WAN interface until the router has
       successfully completed the IPv6 address and the delegated
       prefix acquisition process.
 G-4:  By default, an IPv6 CE router that has no default router(s) on
       its WAN interface MUST NOT advertise itself as an IPv6 default
       router on its LAN interfaces.  That is, the "Router Lifetime"
       field is set to zero in all Router Advertisement messages it
       originates [RFC4861].
 G-5:  By default, if the IPv6 CE router is an advertising router and
       loses its IPv6 default router(s) and/or detects loss of
       connectivity on the WAN interface, it MUST explicitly
       invalidate itself as an IPv6 default router on each of its
       advertising interfaces by immediately transmitting one or more
       Router Advertisement messages with the "Router Lifetime" field
       set to zero [RFC4861].

4.2. WAN-Side Configuration

 The IPv6 CE router will need to support connectivity to one or more
 access network architectures.  This document describes an IPv6 CE
 router that is not specific to any particular architecture or service
 provider and that supports all commonly used architectures.
 IPv6 Neighbor Discovery and DHCPv6 protocols operate over any type of
 IPv6-supported link layer, and there is no need for a link-layer-
 specific configuration protocol for IPv6 network-layer configuration
 options as in, e.g., PPP IP Control Protocol (IPCP) for IPv4.  This
 section makes the assumption that the same mechanism will work for
 any link layer, be it Ethernet, the Data Over Cable Service Interface
 Specification (DOCSIS), PPP, or others.

Singh, et al. Informational [Page 8] RFC 7084 IPv6 CE Router Requirements November 2013

 WAN-side requirements:
 W-1:  When the router is attached to the WAN interface link, it MUST
       act as an IPv6 host for the purposes of stateless [RFC4862] or
       stateful [RFC3315] interface address assignment.
 W-2:  The IPv6 CE router MUST generate a link-local address and
       finish Duplicate Address Detection according to [RFC4862] prior
       to sending any Router Solicitations on the interface.  The
       source address used in the subsequent Router Solicitation MUST
       be the link-local address on the WAN interface.
 W-3:  Absent other routing information, the IPv6 CE router MUST use
       Router Discovery as specified in [RFC4861] to discover a
       default router(s) and install a default route(s) in its routing
       table with the discovered router's address as the next hop.
 W-4:  The router MUST act as a requesting router for the purposes of
       DHCPv6 prefix delegation ([RFC3633]).
 W-5:  The IPv6 CE router MUST use a persistent DHCP Unique Identifier
       (DUID) for DHCPv6 messages.  The DUID MUST NOT change between
       network-interface resets or IPv6 CE router reboots.
 W-6:  The WAN interface of the CE router SHOULD support a Port
       Control Protocol (PCP) client as specified in [RFC6887] for use
       by applications on the CE router.  The PCP client SHOULD follow
       the procedure specified in Section 8.1 of [RFC6887] to discover
       its PCP server.  This document takes no position on whether
       such functionality is enabled by default or mechanisms by which
       users would configure the functionality.  Handling PCP requests
       from PCP clients in the LAN side of the CE router is out of
       scope.
 Link-layer requirements:
 WLL-1:  If the WAN interface supports Ethernet encapsulation, then
         the IPv6 CE router MUST support IPv6 over Ethernet [RFC2464].
 WLL-2:  If the WAN interface supports PPP encapsulation, the IPv6 CE
         router MUST support IPv6 over PPP [RFC5072].
 WLL-3:  If the WAN interface supports PPP encapsulation, in a dual-
         stack environment with IPCP and IPV6CP running over one PPP
         logical channel, the Network Control Protocols (NCPs) MUST be
         treated as independent of each other and start and terminate
         independently.

Singh, et al. Informational [Page 9] RFC 7084 IPv6 CE Router Requirements November 2013

 Address assignment requirements:
 WAA-1:   The IPv6 CE router MUST support Stateless Address
          Autoconfiguration (SLAAC) [RFC4862].
 WAA-2:   The IPv6 CE router MUST follow the recommendations in
          Section 4 of [RFC5942], and in particular the handling of
          the L flag in the Router Advertisement Prefix Information
          option.
 WAA-3:   The IPv6 CE router MUST support DHCPv6 [RFC3315] client
          behavior.
 WAA-4:   The IPv6 CE router MUST be able to support the following
          DHCPv6 options: Identity Association for Non-temporary
          Address (IA_NA), Reconfigure Accept [RFC3315], and
          DNS_SERVERS [RFC3646].  The IPv6 CE router SHOULD be able to
          support the DNS Search List (DNSSL) option as specified in
          [RFC3646].
 WAA-5:   The IPv6 CE router SHOULD implement the Network Time
          Protocol (NTP) as specified in [RFC5905] to provide a time
          reference common to the service provider for other
          protocols, such as DHCPv6, to use.  If the CE router
          implements NTP, it requests the NTP Server DHCPv6 option
          [RFC5908] and uses the received list of servers as primary
          time reference, unless explicitly configured otherwise.  LAN
          side support of NTP is out of scope for this document.
 WAA-6:   If the IPv6 CE router receives a Router Advertisement
          message (described in [RFC4861]) with the M flag set to 1,
          the IPv6 CE router MUST do DHCPv6 address assignment
          (request an IA_NA option).
 WAA-7:   If the IPv6 CE router does not acquire a global IPv6
          address(es) from either SLAAC or DHCPv6, then it MUST create
          a global IPv6 address(es) from its delegated prefix(es) and
          configure those on one of its internal virtual network
          interfaces, unless configured to require a global IPv6
          address on the WAN interface.
 WAA-8:   The CE router MUST support the SOL_MAX_RT option [RFC7083]
          and request the SOL_MAX_RT option in an Option Request
          Option (ORO).

Singh, et al. Informational [Page 10] RFC 7084 IPv6 CE Router Requirements November 2013

 WAA-9:   As a router, the IPv6 CE router MUST follow the weak host
          (Weak End System) model [RFC1122].  When originating packets
          from an interface, it will use a source address from another
          one of its interfaces if the outgoing interface does not
          have an address of suitable scope.
 WAA-10:  The IPv6 CE router SHOULD implement the Information Refresh
          Time option and associated client behavior as specified in
          [RFC4242].
 Prefix delegation requirements:
 WPD-1:  The IPv6 CE router MUST support DHCPv6 prefix delegation
         requesting router behavior as specified in [RFC3633]
         (Identity Association for Prefix Delegation (IA_PD) option).
 WPD-2:  The IPv6 CE router MAY indicate as a hint to the delegating
         router the size of the prefix it requires.  If so, it MUST
         ask for a prefix large enough to assign one /64 for each of
         its interfaces, rounded up to the nearest nibble, and SHOULD
         be configurable to ask for more.
 WPD-3:  The IPv6 CE router MUST be prepared to accept a delegated
         prefix size different from what is given in the hint.  If the
         delegated prefix is too small to address all of its
         interfaces, the IPv6 CE router SHOULD log a system management
         error.  [RFC6177] covers the recommendations for service
         providers for prefix allocation sizes.
 WPD-4:  By default, the IPv6 CE router MUST initiate DHCPv6 prefix
         delegation when either the M or O flags are set to 1 in a
         received Router Advertisement (RA) message.  Behavior of the
         CE router to use DHCPv6 prefix delegation when the CE router
         has not received any RA or received an RA with the M and the
         O bits set to zero is out of scope for this document.
 WPD-5:  Any packet received by the CE router with a destination
         address in the prefix(es) delegated to the CE router but not
         in the set of prefixes assigned by the CE router to the LAN
         must be dropped.  In other words, the next hop for the
         prefix(es) delegated to the CE router should be the null
         destination.  This is necessary to prevent forwarding loops
         when some addresses covered by the aggregate are not
         reachable [RFC4632].

Singh, et al. Informational [Page 11] RFC 7084 IPv6 CE Router Requirements November 2013

    (a)  The IPv6 CE router SHOULD send an ICMPv6 Destination
         Unreachable message in accordance with Section 3.1 of
         [RFC4443] back to the source of the packet, if the packet is
         to be dropped due to this rule.
 WPD-6:  If the IPv6 CE router requests both an IA_NA and an IA_PD
         option in DHCPv6, it MUST accept an IA_PD option in DHCPv6
         Advertise/Reply messages, even if the message does not
         contain any addresses, unless configured to only obtain its
         WAN IPv6 address via DHCPv6; see [DHCPv6-STATEFUL-ISSUES].
 WPD-7:  By default, an IPv6 CE router MUST NOT initiate any dynamic
         routing protocol on its WAN interface.
 WPD-8:  The IPv6 CE router SHOULD support the [RFC6603] Prefix
         Exclude option.

4.3. LAN-Side Configuration

 The IPv6 CE router distributes configuration information obtained
 during WAN interface provisioning to IPv6 hosts and assists IPv6
 hosts in obtaining IPv6 addresses.  It also supports connectivity of
 these devices in the absence of any working WAN interface.
 An IPv6 CE router is expected to support an IPv6 end-user network and
 IPv6 hosts that exhibit the following characteristics:
 1.  Link-local addresses may be insufficient for allowing IPv6
     applications to communicate with each other in the end-user
     network.  The IPv6 CE router will need to enable this
     communication by providing globally scoped unicast addresses or
     ULAs [RFC4193], whether or not WAN connectivity exists.
 2.  IPv6 hosts should be capable of using SLAAC and may be capable of
     using DHCPv6 for acquiring their addresses.
 3.  IPv6 hosts may use DHCPv6 for other configuration information,
     such as the DNS_SERVERS option for acquiring DNS information.
 Unless otherwise specified, the following requirements apply to the
 IPv6 CE router's LAN interfaces only.
 ULA requirements:
 ULA-1:  The IPv6 CE router SHOULD be capable of generating a ULA
         prefix [RFC4193].

Singh, et al. Informational [Page 12] RFC 7084 IPv6 CE Router Requirements November 2013

 ULA-2:  An IPv6 CE router with a ULA prefix MUST maintain this prefix
         consistently across reboots.
 ULA-3:  The value of the ULA prefix SHOULD be configurable.
 ULA-4:  By default, the IPv6 CE router MUST act as a site border
         router according to Section 4.3 of [RFC4193] and filter
         packets with local IPv6 source or destination addresses
         accordingly.
 ULA-5:  An IPv6 CE router MUST NOT advertise itself as a default
         router with a Router Lifetime greater than zero whenever all
         of its configured and delegated prefixes are ULA prefixes.
 LAN requirements:
 L-1:   The IPv6 CE router MUST support router behavior according to
        Neighbor Discovery for IPv6 [RFC4861].
 L-2:   The IPv6 CE router MUST assign a separate /64 from its
        delegated prefix(es) (and ULA prefix if configured to provide
        ULA addressing) for each of its LAN interfaces.
 L-3:   An IPv6 CE router MUST advertise itself as a router for the
        delegated prefix(es) (and ULA prefix if configured to provide
        ULA addressing) using the "Route Information Option" specified
        in Section 2.3 of [RFC4191].  This advertisement is
        independent of having or not having IPv6 connectivity on the
        WAN interface.
 L-4:   An IPv6 CE router MUST NOT advertise itself as a default
        router with a Router Lifetime [RFC4861] greater than zero if
        it has no prefixes configured or delegated to it.
 L-5:   The IPv6 CE router MUST make each LAN interface an advertising
        interface according to [RFC4861].
 L-6:   In Router Advertisement messages ([RFC4861]), the Prefix
        Information option's A and L flags MUST be set to 1 by
        default.
 L-7:   The A and L flags' ([RFC4861]) settings SHOULD be user
        configurable.
 L-8:   The IPv6 CE router MUST support a DHCPv6 server capable of
        IPv6 address assignment according to [RFC3315] OR a stateless
        DHCPv6 server according to [RFC3736] on its LAN interfaces.

Singh, et al. Informational [Page 13] RFC 7084 IPv6 CE Router Requirements November 2013

 L-9:   Unless the IPv6 CE router is configured to support the DHCPv6
        IA_NA option, it SHOULD set the M flag to zero and the O flag
        to 1 in its Router Advertisement messages [RFC4861].
 L-10:  The IPv6 CE router MUST support providing DNS information in
        the DHCPv6 DNS_SERVERS and DOMAIN_LIST options [RFC3646].
 L-11:  The IPv6 CE router MUST support providing DNS information in
        the Router Advertisement Recursive DNS Server (RDNSS) and DNS
        Search List options.  Both options are specified in [RFC6106].
 L-12:  The IPv6 CE router SHOULD make available a subset of DHCPv6
        options (as listed in Section 5.3 of [RFC3736]) received from
        the DHCPv6 client on its WAN interface to its LAN-side DHCPv6
        server.
 L-13:  If the delegated prefix changes, i.e., the current prefix is
        replaced with a new prefix without any overlapping time
        period, then the IPv6 CE router MUST immediately advertise the
        old prefix with a Preferred Lifetime of zero and a Valid
        Lifetime of either a) zero or b) the lower of the current
        Valid Lifetime and two hours (which must be decremented in
        real time) in a Router Advertisement message as described in
        Section 5.5.3, (e) of [RFC4862].
 L-14:  The IPv6 CE router MUST send an ICMPv6 Destination Unreachable
        message, code 5 (Source address failed ingress/egress policy)
        for packets forwarded to it that use an address from a prefix
        that has been invalidated.

4.4. Transition Technologies Support

4.4.1. 6rd

 6rd [RFC5969] specifies an automatic tunneling mechanism tailored to
 advance deployment of IPv6 to end users via a service provider's IPv4
 network infrastructure.  Key aspects include automatic IPv6 prefix
 delegation to sites, stateless operation, simple provisioning, and
 service that is equivalent to native IPv6 at the sites that are
 served by the mechanism.  It is expected that such traffic is
 forwarded over the CE router's native IPv4 WAN interface and not
 encapsulated in another tunnel.
 The CE router SHOULD support 6rd functionality.  If 6rd is supported,
 it MUST be implemented according to [RFC5969].  The following CE
 Requirements also apply:

Singh, et al. Informational [Page 14] RFC 7084 IPv6 CE Router Requirements November 2013

 6rd requirements:
 6RD-1:  The IPv6 CE router MUST support 6rd configuration via the 6rd
         DHCPv4 Option 212.  If the CE router has obtained an IPv4
         network address through some other means such as PPP, it
         SHOULD use the DHCPINFORM request message [RFC2131] to
         request the 6rd DHCPv4 Option.  The IPv6 CE router MAY use
         other mechanisms to configure 6rd parameters.  Such
         mechanisms are outside the scope of this document.
 6RD-2:  If the IPv6 CE router is capable of automated configuration
         of IPv4 through IPCP (i.e., over a PPP connection), it MUST
         support user-entered configuration of 6rd.
 6RD-3:  If the CE router supports configuration mechanisms other than
         the 6rd DHCPv4 Option 212 (user-entered, TR-069 [TR-069],
         etc.), the CE router MUST support 6rd in "hub and spoke"
         mode. 6rd in "hub and spoke" requires all IPv6 traffic to go
         to the 6rd Border Relay.  In effect, this requirement removes
         the "direct connect to 6rd" route defined in Section 7.1.1 of
         [RFC5969].
 6RD-4:  A CE router MUST allow 6rd and native IPv6 WAN interfaces to
         be active alone as well as simultaneously in order to support
         coexistence of the two technologies during an incremental
         migration period such as a migration from 6rd to native IPv6.
 6RD-5:  Each packet sent on a 6rd or native WAN interface MUST be
         directed such that its source IP address is derived from the
         delegated prefix associated with the particular interface
         from which the packet is being sent (Section 4.3 of
         [RFC3704]).
 6RD-6:  The CE router MUST allow different as well as identical
         delegated prefixes to be configured via each (6rd or native)
         WAN interface.
 6RD-7:  In the event that forwarding rules produce a tie between 6rd
         and native IPv6, by default, the IPv6 CE router MUST prefer
         native IPv6.

4.4.2. Dual-Stack Lite (DS-Lite)

 Dual-Stack Lite [RFC6333] enables both continued support for IPv4
 services and incentives for the deployment of IPv6.  It also
 de-couples IPv6 deployment in the service provider network from the
 rest of the Internet, making incremental deployment easier.  Dual-
 Stack Lite enables a broadband service provider to share IPv4

Singh, et al. Informational [Page 15] RFC 7084 IPv6 CE Router Requirements November 2013

 addresses among customers by combining two well-known technologies:
 IP in IP (IPv4-in-IPv6) and Network Address Translation (NAT).  It is
 expected that DS-Lite traffic is forwarded over the CE router's
 native IPv6 WAN interface, and not encapsulated in another tunnel.
 The IPv6 CE router SHOULD implement DS-Lite functionality.  If
 DS-Lite is supported, it MUST be implemented according to [RFC6333].
 This document takes no position on simultaneous operation of Dual-
 Stack Lite and native IPv4.  The following CE router requirements
 also apply:
 WAN requirements:
 DLW-1:  The CE router MUST support configuration of DS-Lite via the
         DS-Lite DHCPv6 option [RFC6334].  The IPv6 CE router MAY use
         other mechanisms to configure DS-Lite parameters.  Such
         mechanisms are outside the scope of this document.
 DLW-2:  The IPv6 CE router MUST NOT perform IPv4 Network Address
         Translation (NAT) on IPv4 traffic encapsulated using DS-Lite.
 DLW-3:  If the IPv6 CE router is configured with an IPv4 address on
         its WAN interface, then the IPv6 CE router SHOULD disable the
         DS-Lite Basic Bridging BroadBand (B4) element.

4.5. Security Considerations

 It is considered a best practice to filter obviously malicious
 traffic (e.g., spoofed packets, "Martian" addresses, etc.).  Thus,
 the IPv6 CE router ought to support basic stateless egress and
 ingress filters.  The CE router is also expected to offer mechanisms
 to filter traffic entering the customer network; however, the method
 by which vendors implement configurable packet filtering is beyond
 the scope of this document.
 Security requirements:
 S-1:  The IPv6 CE router SHOULD support [RFC6092].  In particular,
       the IPv6 CE router SHOULD support functionality sufficient for
       implementing the set of recommendations in [RFC6092],
       Section 4.  This document takes no position on whether such
       functionality is enabled by default or mechanisms by which
       users would configure it.

Singh, et al. Informational [Page 16] RFC 7084 IPv6 CE Router Requirements November 2013

 S-2:  The IPv6 CE router SHOULD support ingress filtering in
       accordance with BCP 38 [RFC2827].  Note that this requirement
       was downgraded from a MUST from RFC 6204 due to the difficulty
       of implementation in the CE router and the feature's redundancy
       with upstream router ingress filtering.
 S-3:  If the IPv6 CE router firewall is configured to filter incoming
       tunneled data, the firewall SHOULD provide the capability to
       filter decapsulated packets from a tunnel.

5. Acknowledgements

 Thanks to the following people (in alphabetical order) for their
 guidance and feedback:
 Mikael Abrahamsson, Tore Anderson, Merete Asak, Rajiv Asati, Scott
 Beuker, Mohamed Boucadair, Rex Bullinger, Brian Carpenter, Tassos
 Chatzithomaoglou, Lorenzo Colitti, Remi Denis-Courmont, Gert Doering,
 Alain Durand, Katsunori Fukuoka, Brian Haberman, Tony Hain, Thomas
 Herbst, Ray Hunter, Joel Jaeggli, Kevin Johns, Erik Kline, Stephen
 Kramer, Victor Kuarsingh, Francois-Xavier Le Bail, Arifumi Matsumoto,
 David Miles, Shin Miyakawa, Jean-Francois Mule, Michael Newbery,
 Carlos Pignataro, John Pomeroy, Antonio Querubin, Daniel Roesen,
 Hiroki Sato, Teemu Savolainen, Matt Schmitt, David Thaler, Mark
 Townsley, Sean Turner, Bernie Volz, Dan Wing, Timothy Winters, James
 Woodyatt, Carl Wuyts, and Cor Zwart.
 This document is based in part on CableLabs' eRouter specification.
 The authors wish to acknowledge the additional contributors from the
 eRouter team:
 Ben Bekele, Amol Bhagwat, Ralph Brown, Eduardo Cardona, Margo Dolas,
 Toerless Eckert, Doc Evans, Roger Fish, Michelle Kuska, Diego
 Mazzola, John McQueen, Harsh Parandekar, Michael Patrick, Saifur
 Rahman, Lakshmi Raman, Ryan Ross, Ron da Silva, Madhu Sudan, Dan
 Torbet, and Greg White.

6. Contributors

 The following people have participated as co-authors or provided
 substantial contributions to this document: Ralph Droms, Kirk
 Erichsen, Fred Baker, Jason Weil, Lee Howard, Jean-Francois Tremblay,
 Yiu Lee, John Jason Brzozowski, and Heather Kirksey.  Thanks to Ole
 Troan for editorship in the original RFC 6204 document.

Singh, et al. Informational [Page 17] RFC 7084 IPv6 CE Router Requirements November 2013

7. References

7.1. Normative References

 [RFC1122]  Braden, R., "Requirements for Internet Hosts -
            Communication Layers", STD 3, RFC 1122, October 1989.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol", RFC
            2131, March 1997.
 [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
            Networks", RFC 2464, December 1998.
 [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
            Defeating Denial of Service Attacks which employ IP Source
            Address Spoofing", BCP 38, RFC 2827, May 2000.
 [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.
 [RFC3646]  Droms, R., "DNS Configuration options for Dynamic Host
            Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
            December 2003.
 [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
            Networks", BCP 84, RFC 3704, March 2004.
 [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
            (DHCP) Service for IPv6", RFC 3736, April 2004.
 [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
            More-Specific Routes", RFC 4191, November 2005.
 [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
            Addresses", RFC 4193, October 2005.
 [RFC4242]  Venaas, S., Chown, T., and B. Volz, "Information Refresh
            Time Option for Dynamic Host Configuration Protocol for
            IPv6 (DHCPv6)", RFC 4242, November 2005.

Singh, et al. Informational [Page 18] RFC 7084 IPv6 CE Router Requirements November 2013

 [RFC4443]  Conta, A., Deering, S., and M. Gupta, "Internet Control
            Message Protocol (ICMPv6) for the Internet Protocol
            Version 6 (IPv6) Specification", RFC 4443, March 2006.
 [RFC4605]  Fenner, B., He, H., Haberman, B., and H. Sandick,
            "Internet Group Management Protocol (IGMP) / Multicast
            Listener Discovery (MLD)-Based Multicast Forwarding
            ("IGMP/MLD Proxying")", RFC 4605, August 2006.
 [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
            (CIDR): The Internet Address Assignment and Aggregation
            Plan", BCP 122, RFC 4632, August 2006.
 [RFC4779]  Asadullah, S., Ahmed, A., Popoviciu, C., Savola, P., and
            J. Palet, "ISP IPv6 Deployment Scenarios in Broadband
            Access Networks", RFC 4779, January 2007.
 [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
            "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
            September 2007.
 [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
            Address Autoconfiguration", RFC 4862, September 2007.
 [RFC5072]  Varada, S., Haskins, D., and E. Allen, "IP Version 6 over
            PPP", RFC 5072, September 2007.
 [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
            Time Protocol Version 4: Protocol and Algorithms
            Specification", RFC 5905, June 2010.
 [RFC5908]  Gayraud, R. and B. Lourdelet, "Network Time Protocol (NTP)
            Server Option for DHCPv6", RFC 5908, June 2010.
 [RFC5942]  Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet
            Model: The Relationship between Links and Subnet
            Prefixes", RFC 5942, July 2010.
 [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.

Singh, et al. Informational [Page 19] RFC 7084 IPv6 CE Router Requirements November 2013

 [RFC6106]  Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
            "IPv6 Router Advertisement Options for DNS Configuration",
            RFC 6106, November 2010.
 [RFC6177]  Narten, T., Huston, G., and L. Roberts, "IPv6 Address
            Assignment to End Sites", BCP 157, RFC 6177, March 2011.
 [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
            Stack Lite Broadband Deployments Following IPv4
            Exhaustion", RFC 6333, August 2011.
 [RFC6334]  Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
            Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
            RFC 6334, August 2011.
 [RFC6434]  Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
            Requirements", RFC 6434, December 2011.
 [RFC6603]  Korhonen, J., Savolainen, T., Krishnan, S., and O. Troan,
            "Prefix Exclude Option for DHCPv6-based Prefix
            Delegation", RFC 6603, May 2012.
 [RFC6887]  Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
            Selkirk, "Port Control Protocol (PCP)", RFC 6887, April
            2013.
 [RFC7083]  Droms, R., "Modification to Default Values of SOL_MAX_RT
            and INF_MAX_RT", RFC 7083, November 2013.

7.2. Informative References

 [DHCPv6-STATEFUL-ISSUES]
            Troan, O. and B. Volz, "Issues with multiple stateful
            DHCPv6 options", Work in Progress, May 2013.
 [MULTIHOMING-WITHOUT-NAT]
            Troan, O., Ed., Miles, D., Matsushima, S., Okimoto, T.,
            and D. Wing, "IPv6 Multihoming without Network Address
            Translation", Work in Progress, December 2010.
 [RFC6144]  Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
            IPv4/IPv6 Translation", RFC 6144, April 2011.
 [TR-069]   Broadband Forum, "CPE WAN Management Protocol", TR-069
            Amendment 4, July 2011,
            <http://www.broadband-forum.org/technical/trlist.php>.

Singh, et al. Informational [Page 20] RFC 7084 IPv6 CE Router Requirements November 2013

 [UPnP-IGD] UPnP Forum, , "InternetGatewayDevice:2 Device Template
            Version 1.01", December 2010,
            <http://upnp.org/specs/gw/igd2/>.

Authors' Addresses

 Hemant Singh
 Cisco Systems, Inc.
 1414 Massachusetts Ave.
 Boxborough, MA  01719
 USA
 Phone: +1 978 936 1622
 EMail: shemant@cisco.com
 URI:   http://www.cisco.com/
 Wes Beebee
 Cisco Systems, Inc.
 1414 Massachusetts Ave.
 Boxborough, MA  01719
 USA
 Phone: +1 978 936 2030
 EMail: wbeebee@cisco.com
 URI:   http://www.cisco.com/
 Chris Donley
 CableLabs
 858 Coal Creek Circle
 Louisville, CO  80027
 USA
 EMail: c.donley@cablelabs.com
 Barbara Stark
 AT&T
 1057 Lenox Park Blvd. NE
 Atlanta, GA  30319
 USA
 EMail: barbara.stark@att.com

Singh, et al. Informational [Page 21]

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