



IPv6 Operations (v6ops)                                J. Palet Martinez
Internet-Draft                                         Consulintel, S.L.
Intended status: Informational                             June 12, 2017
Expires: December 14, 2017


         Transition Requirements for IPv6 Customer Edge Routers
              draft-palet-v6ops-rfc7084-bis-transition-00

Abstract

   This document specifies the transition requirements for an IPv6
   Customer Edge (CE) router.  Specifically, this document extends the
   "Minimum Requirements for IPv6-only Customer Edge Routers" (draft-
   palet-v6ops-rfc7084-bis2) in order to allow the provisioning of IPv6
   transition services for the hosts attached to it and the support of
   HNCP ([RFC7788]) for automated provisioning of downstream routers.
   The document covers several transition technologies, either for
   delivering IPv6 in IPv4-only access networks and specially for
   delivering IPv4 "as a service" as required in a world where IPv4
   addresses are no longer available, so hosts in the customer LANs with
   IPv4-only or IPv6-only applications or devices, requiring to
   communicate with IPv4-only services at the Internet, are able to do
   so.

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 December 14, 2017.

Copyright Notice

   Copyright (c) 2017 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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Architecture  . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Current IPv4 End-User Network Architecture  . . . . . . .   5
     4.2.  IPv6 End-User Network Architecture  . . . . . . . . . . .   6
       4.2.1.  Local Communication . . . . . . . . . . . . . . . . .   8
   5.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  General Requirements  . . . . . . . . . . . . . . . . . .   8
     5.2.  WAN-Side Configuration  . . . . . . . . . . . . . . . . .   8
     5.3.  LAN-Side Configuration  . . . . . . . . . . . . . . . . .   8
     5.4.  Transition Technologies Support . . . . . . . . . . . . .   8
       5.4.1.  IPv4 Service Continuity in Customer LANs  . . . . . .   9
         5.4.1.1.  464XLAT . . . . . . . . . . . . . . . . . . . . .   9
         5.4.1.2.  Dual-Stack Lite (DS-Lite) . . . . . . . . . . . .   9
         5.4.1.3.  Lightweight 4over6 (lw4o6)  . . . . . . . . . . .  10
         5.4.1.4.  MAP-E . . . . . . . . . . . . . . . . . . . . . .  11
         5.4.1.5.  MAP-T . . . . . . . . . . . . . . . . . . . . . .  11
       5.4.2.  Support of IPv6 in IPv4-only WAN access . . . . . . .  12
         5.4.2.1.  6in4  . . . . . . . . . . . . . . . . . . . . . .  12
         5.4.2.2.  6rd . . . . . . . . . . . . . . . . . . . . . . .  13
     5.5.  IPv4 Multicast Support  . . . . . . . . . . . . . . . . .  14
     5.6.  Security Considerations . . . . . . . . . . . . . . . . .  14
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   7.  ANNEX A: Code Considerations  . . . . . . . . . . . . . . . .  15
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   This document defines basic IPv6 transition features for a
   residential or small-office router, referred to as an "IPv6
   Transition CE router", in order to establish an industry baseline for
   dual-stack and transition features to be implemented on such a



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   router.

   These routers are based on draft-palet-v6ops-rfc7084-bis2, so the
   scope of this documents is to include also support IPv4, at least in
   the LAN side.

   This document covers the IP transition technologies required when
   ISPs have already and IPv4-only access network that they can't turn
   to dual-stack or IPv6-only, as well as the situation in a world where
   IPv4 addresses are no longer available, so the service providers need
   to provision IPv6-only WAN access, while at the same time ensuring
   that IPv4-only or IPv6-only devices or applications in the customer
   LANs can still reach IPv4-only devices or applications in Internet,
   which still don't have IPv6 support.

   This document specifies the transition mechanisms to be supported by
   an IPv6 transition CE router, relevant provisioning or configuration
   information differences from draft-palet-v6ops-rfc7084-bis2.
   Automatic provisioning of more complex topology than a single router
   with multiple LAN interfaces may be handled by means of HNCP
   ([RFC7788]).  In some cases, manual provisioning may be acceptable,
   when intended for a small number of customers.

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 IPv6 Transition CE router that interoperates successfully
   with a particular subset of currently deploying and planned common
   IPv6 access networks.

2.  Terminology

   This document uses the same terminology as in draft-palet-v6ops-
   rfc7084-bis2, with two minor clarifications.

   The term "IPv6 transition Customer Edge Router" is defined as an
   "IPv6 Customer Edge Router" that provides transition support to allow
   IPv4-IPv6 coexistence either in the WAN, the LAN or both.

   The "WAN Interface" term used across this document, means that can



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   also support link technologies based in Internet-layer (or higher-
   layers) "tunnels", such as tunnels over IPv4 or IPv6 itself.

3.  Usage Scenarios

   The IPv6 Transition CE router described in this document is expected
   to be used typically, in any of the following scenarios:

   1.  Residential/household users.  Common usage is any kind of
       Internet access (web, email, streaming, online gaming, etc.).

   2.  Residential with Small Office/Home Office (SOHO).  Same usage as
       for the first scenario.

   3.  Small Office/Home Office (SOHO).  Same usage as for the first
       scenario.

   4.  Small and Medium Enterprise (SME).  Same usage as for the first
       scenario.

   5.  Residential/household with advanced requirements.  Same basic
       usage as for the first scenario, however there may be
       requirements for exporting services to the WAN (IP cameras, web,
       DNS, email, VPN, etc.).

   6.  Small and Medium Enterprise (SME) with advanced requirements.
       Same basic usage as for the first scenario, however there may be
       requirements for exporting services to the WAN (IP cameras, web,
       DNS, email, VPN, etc.).

   The above list is not intended to be comprehensive of all the
   possible usage scenarios, just the main ones.  In fact, combinations
   of the above usages are also possible, for example a residential with
   SOHO and advanced requirements.

   The mechanisms for exporting IPv6 services are commonly "naturally"
   available in any IPv6 router, as when using GUA, unless they are
   blocked by firewall rules, which may require some manual
   configuration by means of a GUI and/or CLI.

   However, in the case of IPv4, because the usage of private addresses
   and NAT, it typically requires some degree of manual configuration
   such as setting up a DMZ, virtual servers, or port/protocol
   forwarding.  In general, CE routers already provide GUI and/or CLI to
   manually configure them, or the possibility to setup the CE in bridge
   mode, so another CE behind it, takes care of that.  It is out of the
   scope of this document the definition of any requirements for that.




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   The main difference for an IPv6 Transition CE router to support one
   or several of the above indicated scenarios, is related to the packet
   processing capabilities, performance, even other details such as the
   number of WAN/LAN interfaces, their maximum speed, memory for keeping
   tables or tracking connections, etc.  So, it is out of the scope of
   this document to classify them.

   For example, an SME may have just 10 employees (micro-SME), which
   commonly will be considered same as a SOHO, but a small SME can have
   up to 50 employees, or 250 for a medium one.  Depending on the IPv6
   Transition CE router capabilities or even how it is being configured
   (for instance, using SLAAC or DHCPv6), it may support even a higher
   number of employees if the traffic in the LANs is low, or switched by
   another device(s), or the WAN bandwidth requirements are low, etc.
   The actual bandwidth capabilities of access with technologies such as
   FTTH, cable and even 3GPP/LTE, allows the support of such usages, and
   indeed, is a very common situation that access networks and the IPv6
   Transition CE provided by the service provider are the same for SMEs
   and residential users.

   There is also no difference in terms of who actually provides the
   IPv6 Transition CE router.  In most of the cases is the service
   provider, and in fact is responsible, typically, of provisioning/
   managing at least the WAN side.  However, commonly the user has
   access to configure the LAN interfaces, firewall, DMZ, and many other
   aspects.  In fact, in many cases, the user must supply, or at least
   can replace the IPv6 Transition CE router, which makes even more
   relevant that all the IPv6 Transition CE routers, support the same
   requirements defined in this document.

   The IPv6 Transition CE router described in this document is not
   intended for usage in other scenarios such as bigger Enterprises,
   Data Centers, Content Providers, etc.  So, even if the documented
   requirements meet their needs, may have additional requirements,
   which are out of the scope of this document.

4.  Architecture

4.1.  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.



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   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.

4.2.  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.

   The end-user network is a stub network, in the sense that is not
   providing transit to other external networks.  However HNCP
   ([RFC7788]) allows support for automatic provisioning of downstream
   routers.  Figure 1 illustrates the model topology for the end-user
   network.
























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                     +---------------+                      \
                     |   Service     |                       \
                     |   Provider    |                        | Service
                     |    Router     |                        | Provider
                     +-------+-------+                        | Network
                             |                               /
                             | Customer                     /
                             | Internet Connection         /
                             |
                      +------+--------+                    \
                      |     IPv6      |                     \
                      | Customer Edge |                      \
                      |    Router     |                      /
                      +---+-------+---+                     /
          Network A       |       |   Network B            |
    ---+----------------+-+-    --+---+-------------+--    |
       |                |             |             |       \
   +---+------+         |        +----+-----+ +-----+----+   \
   |IPv6 Host |         |        | IPv4 Host| |IPv4/IPv6 |   /
   |          |         |        |          | | Host     |  /
   +----------+         |        +----------+ +----------+ /
                        |                                 |
                 +------+--------+                        | End-User
                 |     IPv6      |                        | Network(s)
                 |    Router     |                         \
                 +------+--------+                          \
          Network C     |                                    \
    ---+-------------+--+---                                  |
       |             |                                        |
   +---+------+ +----+-----+                                  |
   |IPv6 Host | |IPv6 Host |                                 /
   |          | |          |                                /
   +----------+ +----------+                               /

            Figure 1: An Example of a Typical End-User Network

   This architecture describes the:

   o  Basic capabilities of an IPv6 Transition CE router

   o  Provisioning of the WAN interface connecting to the service
      provider

   o  Provisioning of the LAN interfaces

   As indicated in draft-palet-v6ops-rfc7084-bis2, for IPv6 multicast
   traffic, the IPv6 Transition CE router may act as a Multicast
   Listener Discovery (MLD) proxy [RFC4605] and may support a dynamic



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   multicast routing protocol.

   The IPv6 Transition CE router may be manually configured in an
   arbitrary topology with a dynamic routing protocol or using HNCP
   ([RFC7788]).  Automatic provisioning and configuration is described
   for a single IPv6 Transition CE router only.

4.2.1.  Local Communication

   Section 3.2.1 from draft-palet-v6ops-rfc7084-bis2 apply here without
   changes.

   Coexistence with IPv4 requires any IPv6 Transition CE router(s) on
   the LAN to conform to these recommendations, especially requirements
   ULA-5 and L-4 from draft-palet-v6ops-rfc7084-bis2.

5.  Requirements

5.1.  General Requirements

   The IPv6 Transition CE router must comply with the general
   requirements stated in draft-palet-v6ops-rfc7084-bis2.

5.2.  WAN-Side Configuration

   The IPv6 Transition CE router must comply with WAN-Side Configuration
   as stated in draft-palet-v6ops-rfc7084-bis2.

5.3.  LAN-Side Configuration

   The IPv6 Transition CE router must comply with LAN-Side Configuration
   as stated in draft-palet-v6ops-rfc7084-bis2.

   In addition, a new LAN Requirement is:

   L-16 The IPv6 CE router SHOULD provide HNCP (Home Networking Control
   Protocol) services, as specified in [RFC7788].

5.4.  Transition Technologies Support

   Even if the main target of this document is the support of IPv6-only
   WAN access, for some time, there will be a need to support IPv4-only
   devices and applications in the customers LANs, in one side of the
   picture.  In the other side, some Service Providers willing to deploy
   IPv6, may not be able to do so in the first stage, neither as
   IPv6-only or dual-stack in the WAN.  Consequently, transition
   technologies to resolve both issues should be taken in consideration.




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5.4.1.  IPv4 Service Continuity in Customer LANs

5.4.1.1.  464XLAT

   464XLAT [RFC6877] is a technique to provide IPv4 access service to
   IPv6-only edge networks without encapsulation.

   The IPv6 Transition CE router SHOULD support CLAT functionality.  If
   464XLAT is supported, it MUST be implemented according to [RFC6877].
   The following CE Requirements also apply:

   464XLAT requirements:

   464XLAT-1:  The IPv6 Transition CE router MUST perform IPv4 Network
               Address Translation (NAT) on IPv4 traffic translated
               using the CLAT, unless a dedicated /64 prefix has been
               acquired using DHCPv6-PD [RFC3633].

   464XLAT-2:  The IPv6 Transition CE router MUST implement [RFC7050] in
               order to discover the PLAT-side translation IPv4 and IPv6
               prefix(es)/suffix(es).  In environments with PCP support,
               the IPv6 Transition CE SHOULD follow [RFC7225] to learn
               the PLAT-side translation IPv4 and IPv6
               prefix(es)/suffix(es) used by an upstream PCP-controlled
               NAT64 device.

5.4.1.2.  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
   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 IPv6 Transition
   CE router's native IPv6 WAN interface, and not encapsulated in
   another tunnel.

   The IPv6 Transition 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 IPv6 Transition CE
   router requirements also apply:

   DS-Lite requirements:

   DSLITE-1:  The IPv6 Transition CE router MUST support configuration



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              of DS-Lite via the DS-Lite DHCPv6 option [RFC6334].  The
              IPv6 Transition CE router MAY use other mechanisms to
              configure DS-Lite parameters.  Such mechanisms are outside
              the scope of this document.

   DSLITE-2:  The IPv6 Transition CE router MUST support the DHCPv6 S46
              priority option described in [RFC8026].

   DSLITE-3:  The IPv6 Transition CE router MUST NOT perform IPv4
              Network Address Translation (NAT) on IPv4 traffic
              encapsulated using DS-Lite.

   DSLITE-4:  If the IPv6 Transition CE router is configured with an
              IPv4 address on its WAN interface, then the IPv6
              Transition CE router SHOULD disable the DS-Lite Basic
              Bridging BroadBand (B4) element.

5.4.1.3.  Lightweight 4over6 (lw4o6)

   Lw4o6 [RFC7596] specifies an extension to DS-Lite, which moves the
   NAPT function from the DS-Lite tunnel concentrator to the tunnel
   client located in the IPv6 Transition CE router, removing the
   requirement for a CGN function in the tunnel concentrator and
   reducing the amount of centralized state.

   The IPv6 Transition CE router SHOULD implement lw4o6 functionality.
   If DS-Lite is implemented, lw4o6 MUST be supported as well.  If lw4o6
   is supported, it MUST be implemented according to [RFC7596].  This
   document takes no position on simultaneous operation of lw4o6 and
   native IPv4.  The following IPv6 Transition CE router Requirements
   also apply:

   Lw4o6 requirements:

   LW4O6-1:  The IPv6 Transition CE router MUST support configuration of
             lw4o6 via the lw4o6 DHCPv6 options [RFC7598].  The IPv6
             Transition CE router MAY use other mechanisms to configure
             lw4o6 parameters.  Such mechanisms are outside the scope of
             this document.

   LW4O6-2:  The IPv6 Transition CE router MUST support the DHCPv6 S46
             priority option described in [RFC8026].

   LW4O6-3:  The IPv6 Transition CE router MUST support the DHCPv4-over-
             DHCPv6 (DHCP 4o6) transport described in [RFC7341].

   LW4O6-4:  The IPv6 Transition CE router MAY support Dynamic
             Allocation of Shared IPv4 Addresses as described in



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             [RFC7618].

5.4.1.4.  MAP-E

   MAP-E [RFC7597] is a mechanism for transporting IPv4 packets across
   an IPv6 network using IP encapsulation, including a generic mechanism
   for mapping between IPv6 addresses and IPv4 addresses as well as
   transport-layer ports.

   The IPv6 Transition CE router SHOULD support MAP-E functionality.  If
   MAP-E is supported, it MUST be implemented according to [RFC7597].
   The following CE Requirements also apply:

   MAP-E requirements:

   MAPE-1:  The IPv6 Transition CE router MUST support configuration of
            MAP-E via the MAP-E DHCPv6 options [RFC7598].  The IPv6
            Transition CE router MAY use other mechanisms to configure
            MAP-E parameters.  Such mechanisms are outside the scope of
            this document.

   MAPE-2:  The IPv6 Transition CE router MUST support the DHCPv6 S46
            priority option described in [RFC8026].

5.4.1.5.  MAP-T

   MAP-T [RFC7599] is a mechanism similar to MAP-E, differing from it in
   that MAP-T uses IPv4-IPv6 translation, rather than encapsulation, as
   the form of IPv6 domain transport.

   The IPv6 Transition CE router SHOULD support MAP-T functionality.  If
   MAP-T is supported, it MUST be implemented according to [RFC7599].
   The following IPv6 Transition CE Requirements also apply:

   MAP-T requirements:

   MAPT-1:  The CE router MUST support configuration of MAP-T via the
            MAP-E DHCPv6 options [RFC7598].  The IPv6 Transition CE
            router MAY use other mechanisms to configure MAP-E
            parameters.  Such mechanisms are outside the scope of this
            document.

   MAPT-2:  The IPv6 Transition CE router MUST support the DHCPv6 S46
            priority option described in [RFC8026].







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5.4.2.  Support of IPv6 in IPv4-only WAN access

5.4.2.1.  6in4

   6in4 [RFC4213] specifies a tunneling mechanism to allow end-users to
   manually configure IPv6 support via a service provider's IPv4 network
   infrastructure.

   The IPv6 Transition CE router MAY support 6in4 functionality.  6in4
   used for a manually configured tunnel requires a subset of the 6rd
   parameters (delegated prefix and remote IPv4 end-point).  The on-wire
   and forwarding plane is identical for both mechanisms, however 6in4
   doesn't support mesh traffic and requires manually provisioning.
   Thus, if the device supports either 6rd or 6in4, it's commonly a
   minor UI addition to support both.  If 6in4 is supported, it MUST be
   implemented according to [RFC4213].  The following CE Requirements
   also apply:

   6in4 requirements:

   6IN4-1:  The IPv6 Transition CE router SHOULD support 6in4 automated
            configuration by means of the 6rd DHCPv4 Option 212.  If the
            IPv6 Transition 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 Transition CE router MAY use other
            mechanisms to configure 6in4 parameters.  Such mechanisms
            are outside the scope of this document.

   6IN4-2:  If the IPv6 Transition CE router is capable of automated
            configuration of IPv4 through IPCP (i.e., over a PPP
            connection), it MUST support user-entered configuration of
            6in4.

   6IN4-3:  If the IPv6 Transition CE router supports configuration
            mechanisms other than the 6rd DHCPv4 Option 212 (user-
            entered, TR-069 [TR-069], etc.), the IPv6 Transition CE
            router MUST support 6in4 in "hub and spoke" mode. 6in4 in
            "hub and spoke" requires all IPv6 traffic to go to the 6rd
            Border Relay, which in this case is the tunnel-end-point.
            In effect, this requirement removes the "direct connect to
            6rd" route defined in Section 7.1.1 of [RFC5969].

   6IN4-4:  The IPv6 Transition CE router MUST allow 6in4 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 transition period such as
            a transition from 6in4 to native IPv6.



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   6IN4-5:  Each packet sent on a 6in4 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]).

   6IN4-6:  The IPv6 Transition CE router MUST allow different as well
            as identical delegated prefixes to be configured via each
            (6in4 or native) WAN interface.

   6IN4-7:  In the event that forwarding rules produce a tie between
            6in4 and native IPv6, by default, the IPv6 Transition CE
            router MUST prefer native IPv6.

5.4.2.2.  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 IPv6 Transition CE router's native IPv4 WAN
   interface and not encapsulated in another tunnel.

   The IPv6 Transition CE router MAY support 6rd functionality.  If 6rd
   is supported, it MUST be implemented according to [RFC5969].  The
   following CE Requirements also apply:

   6rd requirements:

   6RD-1:  The IPv6 Transition CE router MUST support 6rd configuration
           via the 6rd DHCPv4 Option 212.  If the IPv6 Transition 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
           Transition CE router MAY use other mechanisms to configure
           6rd parameters.  Such mechanisms are outside the scope of
           this document.

   6RD-2:  If the IPv6 Transition 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 IPv6 Transition CE router supports configuration
           mechanisms other than the 6rd DHCPv4 Option 212 (user-
           entered, TR-069 [TR-069], etc.), the IPv6 Transition CE



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           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:  The IPv6 Transition 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 transition period such as a transition
           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 IPv6 Transition 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 Transition CE router
           MUST prefer native IPv6.

5.5.  IPv4 Multicast Support

   Actual deployments support IPv4 multicast for services such as IPTV.
   In the transition phase it is expected that multicast services will
   still be provided using IPv4 to the customer LANs.

   In order to support the delivery of IPv4 multicast services to IPv4
   clients over an IPv6 multicast network, the IPv6 Transition CE router
   SHOULD support [RFC8114] and [RFC8115].

5.6.  Security Considerations

   The IPv6 Transition CE router must comply with the Security
   Considerations as stated in draft-palet-v6ops-rfc7084-bis2.

6.  Acknowledgements

   Thanks to James Woodyatt, Mohamed Boucadair, Masanobu Kawashima,
   Mikael Abrahamsson, Barbara Stark, Ole Troan and Brian Carpenter for
   their review and comments.






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7.  ANNEX A: Code Considerations

   One of the apparent main issues for vendors to include new
   functionalities, such as support for new transition mechanisms, is
   the lack of space in the flash (or equivalent) memory.  However, it
   has been confirmed from existing open source implementations
   (OpenWRT/LEDE), that adding the support for the new transitions
   mechanisms, requires around 10-12 Kbytes (because most of the code is
   shared among several transition mechanisms), which typically means
   about 0,15% of the existing code size in popular CEs in the market.

   It is also clear that the new requirements don't have extra cost in
   terms of RAM memory, neither other hardware requirements such as more
   powerful CPUs.

   The other issue seems to be the cost of developing the code for those
   new functionalities.  However at the time of writing this document,
   it has been confirmed that there are several open source versions of
   the required code for supporting the new transition mechanisms, so
   the development cost is negligent, and only integration and testing
   cost may become a minor issue.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,
              <http://www.rfc-editor.org/info/rfc2131>.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              DOI 10.17487/RFC3633, December 2003,
              <http://www.rfc-editor.org/info/rfc3633>.

   [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
              Networks", BCP 84, RFC 3704, DOI 10.17487/RFC3704, March
              2004, <http://www.rfc-editor.org/info/rfc3704>.

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213,
              DOI 10.17487/RFC4213, October 2005,
              <http://www.rfc-editor.org/info/rfc4213>.



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   [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, DOI 10.17487/RFC4605,
              August 2006, <http://www.rfc-editor.org/info/rfc4605>.

   [RFC5969]  Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
              Infrastructures (6rd) -- Protocol Specification",
              RFC 5969, DOI 10.17487/RFC5969, August 2010,
              <http://www.rfc-editor.org/info/rfc5969>.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
              <http://www.rfc-editor.org/info/rfc6333>.

   [RFC6334]  Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
              RFC 6334, DOI 10.17487/RFC6334, August 2011,
              <http://www.rfc-editor.org/info/rfc6334>.

   [RFC6877]  Mawatari, M., Kawashima, M., and C. Byrne, "464XLAT:
              Combination of Stateful and Stateless Translation",
              RFC 6877, DOI 10.17487/RFC6877, April 2013,
              <http://www.rfc-editor.org/info/rfc6877>.

   [RFC7050]  Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
              the IPv6 Prefix Used for IPv6 Address Synthesis",
              RFC 7050, DOI 10.17487/RFC7050, November 2013,
              <http://www.rfc-editor.org/info/rfc7050>.

   [RFC7225]  Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the
              Port Control Protocol (PCP)", RFC 7225,
              DOI 10.17487/RFC7225, May 2014,
              <http://www.rfc-editor.org/info/rfc7225>.

   [RFC7341]  Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I.
              Farrer, "DHCPv4-over-DHCPv6 (DHCP 4o6) Transport",
              RFC 7341, DOI 10.17487/RFC7341, August 2014,
              <http://www.rfc-editor.org/info/rfc7341>.

   [RFC7596]  Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
              Farrer, "Lightweight 4over6: An Extension to the Dual-
              Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
              July 2015, <http://www.rfc-editor.org/info/rfc7596>.






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   [RFC7597]  Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
              Murakami, T., and T. Taylor, Ed., "Mapping of Address and
              Port with Encapsulation (MAP-E)", RFC 7597,
              DOI 10.17487/RFC7597, July 2015,
              <http://www.rfc-editor.org/info/rfc7597>.

   [RFC7598]  Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec,
              W., Bao, C., Yeh, L., and X. Deng, "DHCPv6 Options for
              Configuration of Softwire Address and Port-Mapped
              Clients", RFC 7598, DOI 10.17487/RFC7598, July 2015,
              <http://www.rfc-editor.org/info/rfc7598>.

   [RFC7599]  Li, X., Bao, C., Dec, W., Ed., Troan, O., Matsushima, S.,
              and T. Murakami, "Mapping of Address and Port using
              Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599, July
              2015, <http://www.rfc-editor.org/info/rfc7599>.

   [RFC7618]  Cui, Y., Sun, Q., Farrer, I., Lee, Y., Sun, Q., and M.
              Boucadair, "Dynamic Allocation of Shared IPv4 Addresses",
              RFC 7618, DOI 10.17487/RFC7618, August 2015,
              <http://www.rfc-editor.org/info/rfc7618>.

   [RFC7788]  Stenberg, M., Barth, S., and P. Pfister, "Home Networking
              Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April
              2016, <http://www.rfc-editor.org/info/rfc7788>.

   [RFC8026]  Boucadair, M. and I. Farrer, "Unified IPv4-in-IPv6
              Softwire Customer Premises Equipment (CPE): A DHCPv6-Based
              Prioritization Mechanism", RFC 8026, DOI 10.17487/RFC8026,
              November 2016, <http://www.rfc-editor.org/info/rfc8026>.

   [RFC8114]  Boucadair, M., Qin, C., Jacquenet, C., Lee, Y., and Q.
              Wang, "Delivery of IPv4 Multicast Services to IPv4 Clients
              over an IPv6 Multicast Network", RFC 8114,
              DOI 10.17487/RFC8114, March 2017,
              <http://www.rfc-editor.org/info/rfc8114>.

   [RFC8115]  Boucadair, M., Qin, J., Tsou, T., and X. Deng, "DHCPv6
              Option for IPv4-Embedded Multicast and Unicast IPv6
              Prefixes", RFC 8115, DOI 10.17487/RFC8115, March 2017,
              <http://www.rfc-editor.org/info/rfc8115>.

8.2.  Informative References

   [TR-069]   Broadband Forum, "CPE WAN Management Protocol", TR-069
              Amendment 4, July 2011,
              <http://www.broadband-forum.org/technical/trlist.php>.




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

Author's Address

   Jordi Palet Martinez
   Consulintel, S.L.
   Molino de la Navata, 75
   La Navata - Galapagar, Madrid  28420
   Spain

   EMail: jordi.palet@consulintel.es
   URI:   http://www.consulintel.es/




































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