Internet DRAFT - draft-palet-v6ops-transition-ipv4aas

draft-palet-v6ops-transition-ipv4aas







IPv6 Operations (v6ops)                                J. Palet Martinez
Internet-Draft                                          The IPv6 Company
Intended status: Informational                              H. M.-H. Liu
Expires: September 3, 2018                          D-Link Systems, Inc.
                                                           March 2, 2018


 Transition Requirements for IPv6 Customer Edge Routers to support IPv4
                              as a Service
                draft-palet-v6ops-transition-ipv4aas-00

Abstract

   This document specifies the transition requirements for an IPv6
   Customer Edge (CE) router, either provided by the service provider or
   thru the retail market.

   Specifically, this document extends the "Basic Requirements for IPv6
   Customer Edge Routers" ([RFC7084]) in order to allow the provisioning
   of IPv6 transition services for the support of IPv4 as a Service
   (IPv4aaS) by means of new transition mechanisms, which where not
   available at the time [RFC7084] was published.  The document only
   covers transition technologies for delivering IPv4 in IPv6-only
   access networks, commonly called IPv4 "as-a-service" (IPv4aaS), 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 still 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 https://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 September 3, 2018.






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Copyright Notice

   Copyright (c) 2018 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
   (https://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 . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  End-User Network Architecture . . . . . . . . . . . . . . . .   6
   5.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  General Requirements  . . . . . . . . . . . . . . . . . .   9
     5.2.  LAN-Side Configuration  . . . . . . . . . . . . . . . . .   9
     5.3.  Transition Technologies Support for IPv4 Service
           Continuity        (IPv4 as a Service - IPv4aaS) . . . . .   9
       5.3.1.  464XLAT . . . . . . . . . . . . . . . . . . . . . . .  10
       5.3.2.  Lightweight 4over6 (lw4o6)  . . . . . . . . . . . . .  10
       5.3.3.  MAP-E . . . . . . . . . . . . . . . . . . . . . . . .  11
       5.3.4.  MAP-T . . . . . . . . . . . . . . . . . . . . . . . .  11
   6.  IPv4 Multicast Support  . . . . . . . . . . . . . . . . . . .  12
   7.  Code Considerations . . . . . . . . . . . . . . . . . . . . .  12
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     10.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   This document defines basic IPv6 transition features for a
   residential or small-office router, referred to as an "IPv6
   Transition CE router with IPv4aaS support", in order to establish an
   industry baseline for transition features to be implemented on such a
   router.




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   These routers are based on "Basic Requirements for IPv6 Customer Edge
   Routers" ([RFC7084]), so the scope of this documents is to ensure the
   IPv4 "service continuity" support, in the LAN side and the access to
   IPv4-only Internet services from an IPv6-only access WAN even from
   IPv6-only applications or devices in the LAN side.

   This document covers the IP transition technologies required when
   ISPs have already an IPv6-only access network, which is becoming a
   common 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 both IPv4-only and
   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, and relevant provisioning or
   configuration information differences from [RFC7084].

   This document is not a recommendation for service providers to use
   any specific transition mechanism.

   Automatic provisioning of more complex topology than a single router
   with multiple LAN interfaces may be handled by means of HNCP
   ([RFC7788]), which is out of the scope of this document.

   The CE vendors need to consider that the situation of lack of IPv4
   addresses and the IPv6 deployment, is a global issue, so the CEs
   fulfilling the requirements of this document aren't only those
   provided by the service providers to the customers, but also the
   customers may need to replace existing ones by themselves thru the
   retail market.

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.




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2.  Terminology

   This document uses the same terminology as in [RFC7084], with two
   minor clarifications.

   The term "IPv6 transition Customer Edge Router with IPv4aaS"
   (shortened as "IPv6 transition CE") is defined as an "IPv6 Customer
   Edge Router" that provides transition support to allow IPv4-IPv6
   coexistence either beyond the WAN, in the LAN or both.

   The "WAN Interface" term used across this document, means that can
   also support link technologies based in Internet-layer (or higher-
   layers) "tunnels", such as IPv4-in-IPv6 tunnels.

3.  Usage Scenarios

   The situation before described, where there is ongoing IPv6
   deployment and lack of IPv4 addresses, is not happening at the same
   pace at every country, and even within every country, every ISP.  For
   different technical, financial, commercial/marketing and socio-
   economical reasons, each network is transitioning at their own pace,
   and nobody has a magic crystal ball, to make a guess.

   Different studies also show that this is a changing situation,
   because in a single country, may be not all operators provide IPv6
   support, and customer churn implies that the same customers at some
   point may have IPv6 service and may not have it, if changing ISP, and
   viceversa.

   So it is clear that, to cover all those evolving situations, it is
   required an IPv6 transition CE which, at least from the perspective
   of the transition support, can keep accommodating to those changes,
   as it may be or not provided by the service provider.  Even may be a
   point when, having one working seamlessly among different operators
   means lower cost for changing them, and so, increase and facilitate
   competition.

   Moreover, because some services will remain as IPv4-only for an
   undetermined time and some service providers may also delay their
   IPv6 support, again for an undetermined period of time, there is an
   uncertainty about how much time there will be a percentage of IPv4
   traffic between end-users and end-services, that definitively needs
   to be "serviced", so there will be a need to provide CEs with support
   "IPv4 as a Service" for some time.

   This document is consequently, based on those premises, in order to
   ensure the continued transition from networks that today may provide
   access with dual-stack or IPv6-in-IPv4, as described in [RFC7084],



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   and as an "extension" to it, evolving to an IPv6-only access with
   IPv4-as-a-Service.

   Considering that situation and different possible usage cases, 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, as well as situations where the same
   CE is used at different times in different scenarios or even
   different services providers that may use a different transition
   mechanism.

   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



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   scope of this document the definition of any requirements for that.

   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, despite if they are provided
   directly by the service provider or acquired thru the retail market.

   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.  End-User Network Architecture

   According to the descriptions in the precedent sections, 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.




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   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.

   From the perspective of an "IPv4 user" behind an IPv6 transition
   Customer Edge Router with IPv4aaS, this doesn't change.

   However, while a typical IPv4 NAT deployment by default blocks all
   incoming connections and may allow opening of ports using a Universal
   Plug and Play Internet Gateway Device (UPnP IGD) [UPnP-IGD] or some
   other firewall control protocol, in the case of an IPv6-only access,
   the latest may not be feasible depending on specific transition
   mechanism details.  PCP (Port Control Protocol, [RFC6887]) may be an
   alternative solution, as well.

   Another consequence of using IPv4 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.  In the case of an IPv6-only
   access, there is no change on that if the transition mechanism keeps
   running the NAT interface towards the LAN side.

   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.  Once again, this is true
   for both, IPv4 and IPv6.

   In general, 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

   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



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   for a single IPv6 Transition CE router only.

5.  Requirements

   The IPv6 Transition CE router must comply with all the requirements
   stated in [RFC7084].

5.1.  General Requirements

   A new general requirement is added:

   G-6 The IPv6-only CE router MUST comply with [RFC7608].

5.2.  LAN-Side Configuration

   A new LAN requirement is:

   L-15 The IPv6 CE router SHOULD implement a DNS proxy as described in
   [RFC5625].

5.3.  Transition Technologies Support for IPv4 Service Continuity (IPv4
      as a Service - IPv4aaS)

   The main target of this document is the support of IPv6-only WAN
   access, and while needed, the support of IPv4-only devices and
   applications in the customers LANs, in one side of the picture.  In
   the other side, some remote services may stay IPv4-only, so a
   solution is also required for both the IPv4-only and the IPv6-only
   devices inside the CE are able to reach the IPv4-only services.
   Consequently, transition technologies to resolve both sides of the
   picture are considered.

   In order to seamlessly provide the IPv4 Service Continuity in
   Customer LANs, allowing an automated IPv6 transition mechanism
   provisioning, a new general transition requirement is added.

   General transition requirement:

   TRANS-1:  The IPv6 Transition CE router MUST support the DHCPv6 S46
             priority option described in [RFC8026] if more than one S46
             mechanisms is supported.

   The following sections describe the requirements for supporting
   additional transition mechanisms not included in [RFC7084].







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5.3.1.  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 verify if the WAN link
               supports native IPv4, and if that's not available, MUST
               enable the CLAT (in order to automatically configure
               [RFC6877]), unless there is a match with a valid
               OPTION_S46_PRIORITY (following section 1.4 of [RFC8026]),
               which will allow configuring any of the other transition
               mechanisms.

   464XLAT-2:  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-3:  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.

5.3.2.  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:



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   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 DHCPv4-over-
             DHCPv6 (DHCP 4o6) transport described in [RFC7341].

   LW4O6-3:  The IPv6 Transition CE router MAY support Dynamic
             Allocation of Shared IPv4 Addresses as described in
             [RFC7618].

5.3.3.  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.

5.3.4.  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-T DHCPv6 options [RFC7598].  The IPv6 Transition CE
            router MAY use other mechanisms to configure MAP-T
            parameters.  Such mechanisms are outside the scope of this



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            document.

6.  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].

7.  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, Linux, others), that adding the support for the new
   transitions mechanisms, requires around 10-12 Kbytes (because most of
   the code base is shared among several transition mechanisms already
   supported by [RFC7084]), as a single data plane is common to all
   them, which typically means about 0,15% of the existing code size in
   popular CEs already 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, and
   even several vendors already have implementations and provide it to
   ISPs, so the development cost is negligent, and only integration and
   testing cost may become a minor issue.

8.  Security Considerations

   The IPv6 Transition CE router must comply with the Security
   Considerations as stated in [RFC7084].

9.  Acknowledgements

   Thanks to James Woodyatt, Mohamed Boucadair, Masanobu Kawashima,
   Mikael Abrahamsson, Barbara Stark, Ole Troan and Brian Carpenter for
   their review and comments in previous versions of this document.




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10.  References

10.1.  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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,
              <https://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,
              <https://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, <https://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,
              <https://www.rfc-editor.org/info/rfc4213>.

   [RFC5625]  Bellis, R., "DNS Proxy Implementation Guidelines",
              BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009,
              <https://www.rfc-editor.org/info/rfc5625>.

   [RFC5969]  Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
              Infrastructures (6rd) -- Protocol Specification",
              RFC 5969, DOI 10.17487/RFC5969, August 2010,
              <https://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,
              <https://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,
              <https://www.rfc-editor.org/info/rfc6334>.






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

   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              DOI 10.17487/RFC6887, April 2013,
              <https://www.rfc-editor.org/info/rfc6887>.

   [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,
              <https://www.rfc-editor.org/info/rfc7050>.

   [RFC7084]  Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
              Requirements for IPv6 Customer Edge Routers", RFC 7084,
              DOI 10.17487/RFC7084, November 2013,
              <https://www.rfc-editor.org/info/rfc7084>.

   [RFC7225]  Boucadair, M., "Discovering NAT64 IPv6 Prefixes Using the
              Port Control Protocol (PCP)", RFC 7225,
              DOI 10.17487/RFC7225, May 2014,
              <https://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,
              <https://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, <https://www.rfc-editor.org/info/rfc7596>.

   [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,
              <https://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,
              <https://www.rfc-editor.org/info/rfc7598>.





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   [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, <https://www.rfc-editor.org/info/rfc7599>.

   [RFC7608]  Boucadair, M., Petrescu, A., and F. Baker, "IPv6 Prefix
              Length Recommendation for Forwarding", BCP 198, RFC 7608,
              DOI 10.17487/RFC7608, July 2015,
              <https://www.rfc-editor.org/info/rfc7608>.

   [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,
              <https://www.rfc-editor.org/info/rfc7618>.

   [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, <https://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,
              <https://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,
              <https://www.rfc-editor.org/info/rfc8115>.

10.2.  Informative References

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

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

Authors' Addresses








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   Jordi Palet Martinez
   The IPv6 Company
   Molino de la Navata, 75
   La Navata - Galapagar, Madrid  28420
   Spain

   EMail: jordi.palet@theipv6company.com
   URI:   http://www.theipv6company.com/


   Hans M.-H. Liu
   D-Link Systems, Inc.
   17595 Mount Herrmann St.
   Fountain Valley, California  92708
   US

   EMail: hans.liu@dlinkcorp.com
   URI:   http://www.dlink.com/

































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