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Individual Submission                               E. Jankiewicz (Ed.)
Internet Draft                                  SRI International, Inc.
Intended status: Informational                         October 25, 2010
Expires: April 2011

    An Annotated Bibliography for IPv4-IPv6 Transition and Coexistence


   The Internet is in the early stages of what may be a protracted
   period of coexistence of IPv4 and IPv6.  Network operators are
   challenged with the task of activating IPv6 without negative impact
   on operating IPv4 networks and their customers.  This draft is an
   informational "annotated bibliography" compiled to help in the
   analysis and development of basic guidelines and recommendations for
   network operators.  The goal of this document is to survey the
   current state of RFCs, Internet-Drafts and external reference
   materials that define the use cases, problem statements, protocols,
   transition mechanisms and coexistence tools that will be of interest
   to a network operator planning to turn on IPv6.

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), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-

   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."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

   This Internet-Draft will expire on April 25, 2009.

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Copyright Notice

   Copyright (c) 2010 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.

Table of Contents

   1. Introduction......................................... 3
      1.1. The Three Laws of IPv4/IPv6 Coexistence Mechanisms..... 4
   2. IPv6 and related Protocol Specifications.................. 6
   3. Problem Statements and Use Cases........................ 7
   4. Transition and Coexistence Scenarios and Architectures...... 8
   5. Transition/Coexistence Tools .......................... 10
      5.1. Address Mapping................................. 11
         5.1.1. Address Translation in Network Operations........ 11
         5.1.2. Application and End-User Considerations With NAT.. 13
         5.1.3. Dual-Stack Lite (DS-lite)..................... 15
      5.2. Tunneling Mechanisms............................. 17
         5.2.1. Teredo.................................... 17
         5.2.2. IPv6 Rapid Deployment (6rd)and Extensions........ 18
         5.2.3. Tunnel Support Protocol (TSP) ................. 20
         5.2.4. Residual IPv4 Deployment over IPv6-only Infrastructure20
         5.2.5. Address Plus Port (AplusP).................... 20
         5.2.6. IRON-RANGER and ISATAP Solutions............... 21
         5.2.7. Softwires Hub and Spoke with L2TP.............. 22
      5.3. Translation.................................... 22
         5.3.1. Historic Approach........................... 22
         5.3.2. Current Translation Approaches................. 23
   An IPv6 network to the IPv4 Internet........ 25
   The IPv4 Internet to an IPv6 network........ 25
   The IPv6 Internet to an IPv4 network........ 25
   An IPv4 network to the IPv6 Internet........ 26
   An IPv6 network to an IPv4 network......... 26
   An IPv4 network to an IPv6 network......... 26
   The IPv6 Internet to the IPv4 Internet...... 26
   The IPv4 Internet to the IPv6 Internet...... 26
      5.4. Connectivity Checking and Delay Avoidance............ 27
   6. Prefix and Address Assignment and Distribution............ 28
   7. How-to, Whitepapers and FAQs .......................... 30

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   8. Experiments, Trials and Prototypes...................... 30
   9. Implementation Reports ............................... 31
   10. Books on IPv6...................................... 31
   11. Miscellaneous...................................... 32
   12. Security Considerations.............................. 33
   13. IANA Considerations................................. 33
   14. Conclusions........................................ 33
   15. References ........................................ 33
      15.1. Normative References............................ 33
      15.2. Informative References .......................... 33
   16. Acknowledgments.................................... 34

1. Introduction

   Since the IPv6 protocol was defined in 1995 as RFC 1883 (replaced in
   1998 by RFC 2460) the Internet has been in a long transition from
   IPv4 to IPv6.  In reality, we are still in the early stages of what
   is likely to be a protracted period of coexistence, where IPv6
   penetration in hosts (both servers and clients) will gradually ramp
   up as networks make IPv6 available through their infrastructures.

   Network operators face a daunting task to design and implement plans
   to activate IPv6 without negative impact on large (in some cases very
   large) operating IPv4 networks with many live customers.  Some basic
   guidelines and recommendations for network operators are being
   developed (http://tools.ietf.org/html/draft-lee-v4v6tran-problem) and
   this draft is an informational companion to that effort.  The goal of
   this document is to survey the current state of RFCs, active (and
   expired but still relevant) Internet-Drafts and external reference
   materials that define the use cases, problem statements, protocols,
   transition mechanisms and coexistence tools that will be of interest
   to a network operator planning to turn on IPv6.

   This is a dynamic and evolving marketplace of ideas.  At best, this
   draft is a blurry snapshot of the landscape near to the time of its
   publication.  The editor intends this compendium to be merely the
   starting point for an active database or wiki available for community
   contribution including feedback on the real-world experience of
   network operators as they turn on IPv6.  Note that the links to RFCs
   and drafts are based on the IETF Tools view of the repository at
   http://tools.ietf.org/html/.  The links for active drafts are not for
   a specific revision but should link to the last or latest version.

   The following sections comprise an annotated bibliography of the
   currently available documentation to knowledge of the editor.  It is
   provided as informational guidance only, and any network operator
   contemplating an IPv6 implementation will of course exercise due

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   diligence in researching all the issues, standards and
   recommendations and analyze applicability to the particular network

   Note that as the body of this text includes full reference
   information for the bibliography entries these are not included in
   the normal Reference section.

   [Editor's note to be removed before publication:

   While this draft is circulating, the editor is interested in any and
   all pointers to additional useful references.  Contributions of
   capsule summaries and applicability for any of the listed entries
   would also be appreciated and will be graciously acknowledged.  If I
   have missed anyone who already chipped in, this will be cheerfully
   rectified upon your reminder via a private e-mail.  ]

1.1. The Three Laws of IPv4/IPv6 Coexistence Mechanisms

   The Editor of this draft thought it might be helpful to briefly
   explore the motivations driving the current profusion of coexistence
   mechanisms.  In the not so distant past little or no discussion of
   this topic was going on in the IETF, as many felt the case was
   closed.  A discussion in the Intarea meeting at IETF 71 in Dublin and
   a presentation at the plenary at that meeting led to a reawakening of
   interest in coexistence and transition tools.  This discussion
   continued at a special meeting in Montreal in October 2008, and has
   occupied substantial time on the mailing lists and meetings of
   several Working Groups since then.  The Internet Area, IPv6 Operation
   (v6ops), Softwires and Behave WGs have generated many contributions,
   and an ad-hoc discussion mailing list has been established at

   Early in the life of IPv6, the assumption was made that IPv6
   deployment, based on dual-stack implementations, would be ubiquitous
   long before the IPv4 address pool would run out.  For special cases,
   tunneling through dissimilar networks or use of an external
   translation box such as NAT-PT would allow interim operation of
   legacy equipment.  At present, this has not yet come to pass.  The
   impending exhaustion of IPv4 address space renders dual-stack
   impossible in some deployments and issues have resulted in NAT-PT
   being deprecated to Historic status.

   Nature (and your average Internet-Draft author) abhors a vacuum.
   With the demise of NAT-PT and the increasing urgency to get moving on
   IPv6 transition, we are now in a period of "Let 1000 Flowers Bloom"
   where many ideas are being advanced, and a lot of IETF brainpower is

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   being spent debating the relative merits and evilness of various
   approaches.  The spectrum of opinion on coexistence mechanisms has
   two extremes:

   IPv4 is so Over:  Concentrate on deploying native IPv6 and managing
   it effectively, rather than spinning more complex webs of IPv4
   accommodation.  Deploying anything that delays IPv6 and enables more
   IPv4 usage at this point is irresponsible.

   Where's the Business Case:  Real customers need IPv4, there is no
   IPv6 content, no demand for IPv6.  Scale up NAT to keep IPv4 viable,
   provide some sort of artificial IPv6 access, if and when customers
   ask.  No plans for native IPv6 in the foreseeable future.

   A reasonable position recognizes the valid motivation on both sides.
   An ISP may not be able to dictate updates to customer computers and
   routers, and must provide access to all legacy customers, not just
   eager IPv6 adopters, so an interim mechanism that minimizes their
   inconvenience is needed.  One size will never fit all, so some
   solutions may be a good fit for one ISP, and not for others.  While
   evaluating all the alternative documented here, the principle to keep
   in mind is that the IETF should provide good engineering opinions on
   all these alternatives, to permit things that will help, and prevent
   things that will cause problems.

   This can be summed up in the "Three Laws of IPv4/IPv6 Coexistence

   1. First, do no harm.

   2. Keep it simple.

   3. Keep moving towards more native IPv6.

   "No harm" in this case means that a good solution will not unduly
   interfere with good experience for the legacy IPv4 customer, nor will
   it impede the eager IPv6 adopter.  The solution must not cause
   problems for peer or backbone networks or for the Internet community
   at large.

   "Simple" means to solve particular problems with specific solutions
   focused to the point of need rather than attempting broad and complex
   methods that impinge on all traffic.  However, do not simplify any
   more than necessary to avoid harm.

   The compulsion to move towards native IPv6 follows from the first two
   laws.  Over time, even minimal harm and complexity that even a good

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   mechanism presents can and should be reduced over time by continuing
   to enable, promote and encourage transition to native IPv6.  Design
   and deploy your interim solution(s) with a clear migration path that
   will eventually render them redundant.  Set a date after which you
   will not deploy any new equipment that does not support IPv6.  Set a
   date to sunset IPv4 access, giving legacy customers plenty of time
   (and incentive) to upgrade their old equipment.

   In summary, it seems that the Robustness Principle (Postel's Law)
   would apply, as it does in many situations:

        "Be conservative in what you do, be liberal in what you
        accept from others."  [RFC 793]

   Following the Robustness Principle and the Three Laws should allow an
   operator complete freedom to manage their own network and to chose
   and operate any coexistence mechanism as long as they need to for
   supporting their customers, except where those choices cause harm to
   someone else.  Of course, there is no universal definition of "harm"
   so reasonable people can disagree, e.g. if a mechanism in use on the
   access side causes additional delay, content providers may see that
   as "harming" their users' experience.  That's why Working Group
   mailing lists and IETF meetings are just so much fun.

   Oh, and by the way, the Fourth Law should be "Don't reinvent the
   wheel" so please explore the RFCs, drafts and other citations to see
   if someone has already proposed something similar to your idea.  Your
   contributions are needed, but time and energy is better spent
   exploring novel approaches and building on what has already been

2. IPv6 and related Protocol Specifications

   "IPv6 Node Requirements" J. Loughney, Ed. April 2006

   "IPv6 Node Requirements RFC 4294-bis" E. Jankiewicz, J. Loughney, T.

   RFC 4294 and its update draft are included by reference.  These
   provide a comprehensive overview of the IPv6 baseline specifications
   and the reader is directed to them to avoid a redundant listing here.

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3. Problem Statements and Use Cases

   "Problem Statements of IPv6 Transition of ISP" Y. Lee, Ed.

   This draft is being developed by an ad-hoc group interested in
   providing guidance to network operators on the IPv6 transition.  It
   will include high level use cases (as contributed by IETF
   participants with network operator experience) and a problem
   statement documenting what additional work IETF could do to provide
   sufficient tools and guidance for the network operators

   "Mobile Networks Considerations for IPv6 Deployment" R. Koodli

   Mobile Internet access from smartphones and other mobile devices is
   accelerating the exhaustion of IPv4 addresses.  IPv6 is widely seen
   as crucial for the continued operation and growth of the Internet,
   and in particular, it is critical in mobile networks.  This document
   discusses the issues that arise when deploying IPv6 in mobile
   networks.  Hence, this document can be a useful reference for service
   providers and network designers.

   "Routing Loop Attack using IPv6 Automatic Tunnels: Problem Statement
   and Proposed Mitigations", G. Nakibly and F. Templin

   This document is concerned with security vulnerabilities in IPv6-in-
   IPv4 automatic tunnels.  These vulnerabilities allow an attacker to
   take advantage of inconsistencies between the IPv4 routing state and
   the IPv6 routing state.  The attack forms a routing loop which can be
   abused as a vehicle for traffic amplification to facilitate DoS
   attacks.  If automatic tunnels are used in a deployment the warnings
   and mitigations in this draft should be considered.

   "Use Case for IPv6 Transition for a Large-Scale Broadband Network"
   CC. Huang (Ed.), XY. Li and LM. Hu

   "IPv6 Transition Cable Access Network Use Cases" Y. Lee and V.

   "IPv6 Transition Use Case for a Large Mobile Network" C. Zhou (Ed.)
   and T. Taylor

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   Each of these use case drafts is focused on a particular deployment
   model for a specific market segment.  While each may be based on a
   singular operator's experience or planning, the intention is to
   develop the set of use cases drafts to be of interest to any network
   operator in the segment.

   "Considerations for Stateless Translation (IVI/dIVI) in Large SP
   Network" Q. Sun et al.

   "dIVI" is a prefix-specific and stateless address mapping method
   based on IVI which can directly translate IPv4 packet to IPv6 packet.
   This document describes the challenges and requirements for large
   Service Provider to deploy IPv6 in an operational network and
   specifically considerations for dIVI deployment.

4. Transition and Coexistence Scenarios and Architectures

   RFC 5211 "An Internet Transition Plan." J. Curran, July 2008

   While the abstract for this RFC humbly describes it as just "one
   possible plan" for the IPv6 transition, it provides very good context
   and a common language to use when talking about transition plans, and
   can be seen as a call to action.  It describes three phases of the
   transition, and proposes a timeline based on predictions of the
   imminent exhaustion of the IPv4 address space.  The phases are:

   1. Preparation, where IPv4 predominates while service providers
      trial and experiment with IPv6, and end-users prepare to provide
      Internet-facing IPv6 services in the future.  The timeline in the
      RFC described this phase as in progress, and optimally this phase
      would have ended already.

   2. Transition, where both IPv4 and IPv6 services are offered and
      used, with production level support for IPv6, although this may
      be via transition mechanisms rather than native IPv6.  The RFC
      targeted this phase to end in 2011.

   3. Post-Transition, where native IPv6 services should be offered
      while IPv4 services may still be supported.

   "Guidelines for Using Transition Mechanisms During IPv6 Deployment"
   J. Arkko and F. Baker

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   IPv6 deployment requires some effort, resources, and expertise.  The
   availability of many different deployment models is one reason why
   expertise is required.  This draft discusses the IPv6 deployment
   models and migration tools, and recommends ones that have been found
   to work well in operational networks in many common situations.

   "IPv6 Transition Guide For A Large ISP Providing Broadband Access",
   G. Yang (Ed.), L. Hu and J. Lin

   This draft is a product of the current v4tov6transition effort and it
   examines IPv6 migration solutions for each part of the Large-scale
   broadband infrastructure with a layer 2 access network.  The analysis
   is based on the requirements for providing existing broadband
   services in v4v6-coexisting or IPv6-only situations. The draft
   describes the suitable scenarios for each solution.

   "IPv6 Transition Guide for a Large Mobile Operator" T. Tsou (Ed.) and
   T. Taylor

   Similarly, this draft examines IPv6 migration solutions for a large
   mobile network.

   RFC 6036 "Emerging Service Provider Scenarios for IPv6 Deployment",
   B. Carpenter, S. Jiang

   This document describes practices and plans that are emerging among
   Internet Service Providers for the deployment of IPv6 services.  They
   are based on practical experience so far, as well as current plans
   and requirements, reported in a survey of a number of ISPs carried
   out in early 2010.  The document identifies a number of technology
   gaps, but does not make recommendations.

   "Framework for IP Version Transition Scenarios", B. Carpenter, S.
   Jiang and V. Kuarasingh

   This document sets out a framework for the presentation of scenarios
   and recommendations for a variety of approaches to the transition
   from IPv4 to IPv6, given the necessity for a long period of co-
   existence of the two protocols.

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5. Transition/Coexistence Tools

   As network operators and end-users independently proceed with
   transition to IPv6 while others continue to use IPv4, a potentially
   long period of coexistence will ensue.  Variations on terminology
   have been used since the specification of IPv6; transition implies a
   process whereby the star of IPv6 rises and the star of IPv4 sets;
   coexistence implies that both will operate together.  Due to
   thoroughly discussed limits to the growth of an Internet using only
   IPv4, IPv6 is a necessary technology for the future of the Internet.
   However, nothing compels the elimination of IPv4; no protocol police
   will forbid its use in the foreseeable future.  IPv4 may disappear
   due to irrelevance when IPv6 is so pervasive to make it redundant,
   but network operators should be prepared to operate IPv4 and IPv6 in
   a mixed deployment for some time.  However, the techniques and
   mechanisms supported by a network operator can be expected to evolve
   and change over time as a rational goal would be to gradually shift
   coexistence costs (real operational expense as well as convenience)
   from "early adopters" of IPv6 to the shrinking pool of IPv4

   Various techniques are required for coexistence, roughly divided into
   three categories:

   1. Address Mapping:  Many situations will require the use of address
       mapping to maintain scalability in the face of dwindling IPv4
       global address space and to support translation and tunneling

   2. Tunneling:  A method for the encapsulation and transport of one
       protocol over or through the infrastructure that favors the
       other, e.g. IPv6 traffic via an IPv4 infrastructure

   3. Protocol Translation:  A mechanism for rewriting packets from one
       protocol to the other so they can be delivered as native (non-
       encapsulated) packets typically due to incompatible end nodes,
       e.g. an IPv6 client to an IPv4 server.

   These categories are not mutually exclusive, as some scenarios and
   solutions incorporate aspects of multiple approaches.

   RFC 4213 "Basic Transition Mechanisms for IPv6 Hosts and Routers" E.
   Nordmark and R. Gilligan October 2005

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5.1. Address Mapping

   The introduction of address family translation presents challenges
   similar to those experienced with Network Address Translation (NAT)
   as it has evolved in the IPv4 Internet.  The depletion of IPv4 global
   address space conspires with the continuing need for routable IPv4
   address in some coexistence approaches to further press proliferation
   and scale of NAT.  While alternatives exist, some network operators
   will continue to see the various flavors of NAT as a necessary evil,
   so it remains important to understand the impact on network
   operations, on the end-user and on applications.

   Dual-Stack Lite (DS-lite) is one of the alternatives to providing
   dual-stack support to end-users in the face of limited global IPv4
   address space.

   RFC 2663 "IP Network Address Translator (NAT) Terminology and
   Considerations" P. Srisuresh and M. Holdrege August 1999

   This document attempts to describe the operation of NAT devices and
   the associated considerations in general, and to define the
   terminology used to identify various flavors of NAT.

5.1.1. Address Translation in Network Operations

   "Common Requirements for IP Address Sharing Schemes" I. Yamagati et
   al. http://tools.ietf.org/html/draft-ietf-behave-lsn-requirements

   This document defines common requirements of multiple types of Large
   Scale Network Address Translation (NAT) that handles Unicast UDP, TCP
   and ICMP.

   "Issues with IP Address Sharing" M. Ford (Ed.) et al.

   The completion of IPv4 address allocations from IANA and the RIRs is
   causing service providers around the world to question how they will
   continue providing IPv4 connectivity service to their subscribers
   when there are no longer sufficient IPv4 addresses to allocate them
   one per subscriber.  Several possible solutions to this problem are
   now emerging based around the idea of shared IPv4 addressing.  These
   solutions give rise to a number of issues and this memo identifies
   those common to all such address sharing approaches.

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   "An Incremental Carrier-Grade NAT (CGN) for IPv6 Transition", Sheng
   Jiang, Dayong Guo, Brian Carpenter

   Carrier-Grade NAT (CGN) devices with integrated transition mechanisms
   can reduce the operational change required during the IPv4 to IPv6
   migration or coexistence period.  This document proposes an
   incremental CGN approach for IPv6 transition.  It can provide IPv6
   access services for IPv6-enabled hosts and IPv4 access services for
   IPv4 hosts while leaving much of a legacy IPv4 ISP network unchanged.
   It is suitable for the initial stage of IPv4 to IPv6 migration.
   Unlike NAT444 based CGN alone, Incremental CGN also supports and
   encourages transition towards dual-stack or IPv6-only ISP networks. A
   smooth transition to IPv6 deployment is also described in this

   "Stateful NAT64: Network Address and Protocol Translation from IPv6
   Clients to IPv4 Servers" Bagnulo, Matthews, van Beijnum

   This document describes stateful NAT64 translation, which allows
   IPv6-only clients to contact IPv4 servers using unicast UDP, TCP, or
   ICMP.  The public IPv4 address can be shared among several IPv6-only
   clients.  When the stateful NAT64 is used in conjunction with DNS64
   no changes are usually required in the IPv6 client or the IPv4

   "NAT64-CPE Mode Operation for Opening Residential Service" G. Chen
   and H. Deng

   The authors of this draft describe the application of fundamental
   NAT64 functionality in CPE deployment scenarios.  The approach is
   intended to eliminate the need for CPE to cooperate with DNS64, and
   to be compatible with legacy residential servers without changes to
   DNS requirements.

   "Flexible IPv6 Migration Scenarios in the Context of IPv4 Address
   Shortage" M. Boucadair (Ed.) et al, October 20, 2009 (expired)

   This memo presents a solution to solve IPv4 address shortage and ease
   IPv4-IPv6 interconnection.  The document presents a set of
   incremental steps for the deployment of IPv6 as a means to solve IPv4
   address exhaustion.  Stateless IPv4/IPv6 address mapping functions
   are introduced and IPv4-IPv6 interconnection scenarios presented.

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   This memo advocates for a more proactive approach for the deployment
   of IPv6 into operational networks.  This memo specifies the IPv6
   variant of the A+P. Both encapsulation and translation scheme are
   covered.  Moreover, two modes are elaborated: the binding mode
   (compatible mode with DS-lite) and the stateless mode.

   "A Note on NAT64 Interaction with Mobile IPv6" W. Haddad and C.

   This memo discusses potential NAT64 technology repercussions for
   mobile nodes using Mobile IPv6.  An ambiguity is identified related
   to the use of DNS during bootstrapping, which is likely to inhibit
   proper signaling between mobile node and home agent.

   "NAT64 for Dual Stack Mobile IPv6" B. Sarikaya and F. Xia

   This memo specifies how IPv6 only mobile nodes (MN) receiving host-
   based mobility management using Dual Stack Mobile IPv6 (DSMIPv6) can
   communicate with IPv4 only servers.  The protocol is based on home
   agents maintaining a table similar to NAT64 and linking it to the
   binding cache.  This technique avoids the problems encountered when
   NAT64 is used for mobile nodes in Dual Stack Mobile IPv6.  How IPv6
   only mobile nodes can receive multicast data from IPv4 only content
   providers is also explained.

   "NAT64 for Proxy Mobile IPv6" B. Sarikaya and F. Xia

   Similarly, this memo specifies how IPv6 only mobile nodes (MN)
   receiving network-based mobility management using Proxy Mobile IPv6
   (PMIPv6) can communicate with IPv4 only servers.

5.1.2. Application and End-User Considerations With NAT

   "Problem Statement for Referrals" B. Carpenter, S. Jiang and B. Zhou

   The purpose of a referral is to enable a given entity in a multiparty
   Internet application to pass information to another party.  It
   enables a communication initiator to be aware of relevant information
   of its destination entity before launching the communication.  This
   memo discusses the problems involved in referral scenarios.

   "Referrals Across an IPv6/IPv4 Translator" D. Wing, October 19, 2009

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   While this draft is expired, this issue remains a topic of
   conversation, including a Bar-BoF at IETF 78.  Referrals across
   disparate address domains may be needed for provision of services
   such as SIP during transition.

   "Legacy NAT Traversal for IPv6: Simple Address Mapping for Premises
   Legacy Equipment (SAMPLE)"

   IPv6 deployment is delayed by the existence of millions of subscriber
   network address translators (NATs) that cannot be upgraded to support
   IPv6.  This document specifies a mechanism for traversal of such
   NATs.  It is based on an address mapping and on a mechanism whereby
   suitably upgraded hosts behind a NAT may obtain IPv6 connectivity via
   a stateless server, known as a SAMPLE server, operated by their
   Internet Service Provider.  SAMPLE is an alternative to the Teredo

   "Some Considerations on the Load-Balancer for NAT64" D. Zhang et al.

   This draft investigates issues with deploying load-balancers with
   NAT64 devices.

   "An FTP ALG for IPv6-to-IPv4 Translation" I. van Beijnum

   The File Transfer Protocol (FTP) has a very long history, and despite
   the fact that today, other options exist to perform file transfers,
   FTP is still in common use.  As such, it is important that in the
   situation where some client computers are IPv6-only while many
   servers are still IPv4-only and IPv6-to-IPv4 translators are used to
   bridge that gap, FTP is made to work through these translators as
   best it can.  This document specifies a middlebox that enables legacy
   usage of FTP with translation.

   "Assessing the Impact of NAT444 on Network Applications" C. Donley et
   al. http://tools.ietf.org/html/draft-donley-nat444-impacts

   NAT444 is an IPv4 extension technology being considered by Service
   Providers to continue offering IPv4 service to customers while
   transitioning to IPv6.  This technology adds an extra Large-Scale NAT
   ("LSN") in the Service Provider network, thereby resulting in two
   NATs.  CableLabs, Time Warner Cable, and Rogers Communications
   independently tested the impacts of NAT444 on many popular Internet
   services using a variety of test scenarios, network topologies, and
   vendor equipment.  This document identifies areas where adding a

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   second layer of NAT disrupts the communication channel for common
   Internet applications.

5.1.3. Dual-Stack Lite (DS-lite)

   "Understanding Dual-Stack Lite" Jeff Doyle, Network World October 22,
   2009 http://www.networkworld.com/community/node/46600

   This article provides a good introduction to DSlite, at the time of
   its publication.  Please see the following drafts for details and
   more current work.

   "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion" A.
   Durand et al.

   This document revisits the dual-stack model and introduces the dual-
   stack lite technology aimed at better aligning the costs and benefits
   of deploying IPv6 in service provider networks.  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).

   "Dual-stack Lite Mobility Solutions" B. Sarikaya and F. Xia October
   11, 2009 (expired)

   Two solutions are presented to show how to use Dual-Stack Lite
   transition technique in mobile networks: one for Proxy Mobile IPv6
   and the other for Dual-Stack Mobile IPv6.  Proxy Mobile IPv6 allows
   IPv4 nodes to receive mobility services using an IPv4 home address.
   In case of client based mobility using DSMIPv6, mobile node is a
   dual-stack node and it can receive an IPv4 home address from the home
   agent which is co-located with DS-lite carrier-grade NAT.

   "Scalable Operation of Address Translators with Per-Interface
   Bindings" J. Arkko and L. Eggert February 9, 2009 (expired)

   This document explains how to employ address translation in networks
   that serve a large number of individual customers without requiring a
   correspondingly large amount of private IPv4 address space.

   "Gateway Initiated Dual-Stack Lite Deployment" F. Brockners et al.

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   Gateway-Initiated Dual-Stack lite (GI-DS-lite) is a modified approach
   to the original Dual-Stack lite (DS-lite) applicable to certain
   tunnel-based access architectures.  GI-DS-lite extends existing
   access tunnels beyond the access gateway to an IPv4-IPv4 NAT using
   softwires with an embedded context identifier, that uniquely
   identifies the end-system the tunneled packets belong to.  The access
   gateway determines which portion of the traffic requires NAT using
   local policies and sends/receives this portion to/from this softwire

   "Deployment DS-lite in Point-to-Point Access Network" Y. Lee (Ed.) et
   al. http://tools.ietf.org/html/draft-zhou-softwire-ds-lite-p2p

   Gateway-Initiated Dual-Stack lite (GI-DS-lite) is a proposal to
   logically extend existing access tunnels beyond the access gateway to
   DS-Lite Address Family Transition Router element (AFTR) using
   softwires with an embedded context identifier.  This memo describes a
   deployment model using GI-DS-lite in Point-to-Point access network.

   "Deploying Dual-Stack Lite in IPv6 Network" M. Boucadair (Ed.) et al.

   Dual-Stack lite requires that the AFTR must have IPv4 connectivity.
   This forbids a service provider who wants to deploy AFTR in an IPv6-
   only network.  This memo proposes an extension to implement a
   stateless IPv4-in-IPv6 encapsulation in the AFTR so that AFTR can be
   deployed in an IPv6-only network.

   "IPv6 RA Option for DS-lite AFTR Element" Y. Lee, M. Boucadair and X.
   Xu http://tools.ietf.org/html/draft-lee-6man-ra-dslite

   This document specifies a new optional extension to IPv6 Router
   Advertisement messages to allow IPv6 routers to advertise DS-Lite
   AFTR addresses to IPv6 hosts (i.e., a default IPv6 route for DS-Lite
   traffic).  The provisioning of the AFTR address is crucial to access
   IPv4 connectivity services in a DS-Lite context.  Means to ensure
   reliable delivery of this information to connecting hosts is a must.

   Furthermore, this RA option can be used as a means to distribute DS-
   Lite serviced customers among a set of deployed AFTRs without
   requiring a central knowledge of the underlying topology and deployed

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5.2. Tunneling Mechanisms

   RFC 2473 "Generic Packet Tunneling in IPv6 Specification."  A. Conta
   and S. Deering, December 1998

   This document defines the model and generic mechanisms for IPv6
   encapsulation of Internet packets, such as IPv6 and IPv4.  The model
   and mechanisms can be applied to other protocol packets as well, such
   as AppleTalk, IPX, CLNP, or others.

   RFC 2529 "Transmission of IPv6 over IPv4 Domains without Explicit
   Tunnels" B. Carpenter and C. Jung March 1999.

   This memo specifies the frame format for transmission of IPv6 packets
   and the method of forming IPv6 link-local addresses over IPv4
   domains.  The motivation for this method is to allow isolated IPv6
   hosts, located on a physical link which has no directly connected
   IPv6 router, to become fully functional IPv6 hosts by using an IPv4
   domain that supports IPv4 multicast as their virtual local link.

   RFC 3056 "Connection of IPv6 Domains via IPv4 Clouds" B. Carpenter
   and K. Moore February 2001

   This memo specifies an optional interim mechanism for IPv6 sites to
   communicate with each other over the IPv4 network without explicit
   tunnel setup, and for them to communicate with native IPv6 domains
   via relay routers.

   RFC 3053 "IPv6 Tunnel Broker" A. Durand, I. Guardini and D. Lento
   January 2001

   The IPv6 global Internet as of today uses a lot of tunnels over the
   existing IPv4 infrastructure.  Those tunnels are difficult to
   configure and maintain in a large scale environment, and the process
   is too complex for the isolated end user.  The motivation for the
   development of the tunnel broker model is to help early IPv6 adopters
   to hook up to an existing IPv6 network with stable, permanent IPv6
   addresses and DNS names.

5.2.1. Teredo

   RFC 4380 "Teredo: Tunneling IPv6 over UDP" C. Huitema February 2006

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   This RFC defined a service that enables nodes located behind one or
   more IPv4 Network Address Translations (NATs) to obtain IPv6
   connectivity by tunneling packets over UDP; we call this the Teredo
   service.  Running the service requires the help of "Teredo servers"
   and "Teredo relays".  The Teredo servers are stateless, and only have
   to manage a small fraction of the traffic between Teredo clients; the
   Teredo relays act as IPv6 routers between the Teredo service and the
   "native" IPv6 Internet.  The relays can also provide interoperability
   with hosts using other transition mechanisms such as "6to4".  Teredo
   client capability has been included in Windows operating systems
   since Windows XP and public servers are available.

   RFC 5991 "Teredo Security Extensions" D. Thaler, S. Krishnan and J.
   Hoagland September 2010

   The Teredo protocol defines a set of flags that are embedded in every
   Teredo IPv6 address.  This document specifies a set of security
   updates that modify the use of this flags field, but are backward

   "Teredo Extensions", D. Thaler

   This document specifies a set of extensions to the Teredo protocol.
   These extensions provide additional capabilities to Teredo, including
   support for more types of Network Address Translations (NATs), and
   support for more efficient communication.

5.2.2. IPv6 Rapid Deployment (6rd)and Extensions

   IPv6 Rapid Deployment (6rd) is an approach that allows a service
   provider to quickly roll out an IPv6 service offering.  Free, a large
   French ISP, successfully deployed a 6rd offering in 5 weeks.  It is
   also being used in a current IPv6 trial offered by Comcast in the

   "How 6rd Eases the Transition to IPv6" Mike Capuano on Cisco SP360
   blog, August 5, 2010

   This article provides a quick overview of 6rd.  The fundamental
   protocol specification and initial implementation experience can be
   found in RFC 5969 and 5569.

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   RFC 5969 "IPv6 Rapid Deployment on IPv4 Infrastructures (6rd)-
   Protocol Specification" W. Townsley and O. Troan August 2010

   RFC 5569 "IPv6 Rapid Deployment on IPv4 Infrastructures (6rd)" R.
   Despres January 2010 http://tools.ietf.org/html/rfc5569

   "IPv6 Across NAT44 CPEs (6a44)" R. Despres, B. Carpenter and S. Jiang

   IPv6 Across NAT44 CPEs (6a44) 6a44 is based on an address mapping and
   on a mechanism whereby suitably upgraded hosts behind a NAT may
   obtain IPv6 connectivity via a stateless 6a44 server function
   operated by their Internet Service Provider.  With it, traffic
   between two 6a44 hosts in a single site remains within the site.
   Except for IANA numbers that remain to be assigned, the specification
   is intended to be complete enough for running codes to be
   independently written and interwork.

   [Note that this draft converges and supersedes work started in two
   separate drafts, which are no longer relevant:

   "UDP Encapsulation of 6rd" Y. Lee and P. Kapoor

   This memo specifies the UDP encapsulation to IPv6 Rapid Deployment
   (6rd) protocol which enables hosts behind unmodified Home Gateway
   device to access 6rd service.  One variation (Server Model) avoids
   host modification by offloading the implementation to a small server
   (relay) on the home LAN.

   "Gateway Initiated 6rd" T. Tsou et al.

   This document proposes an alternative to the deployment model defined
   in RFC 5969 for 6rd.  This model extends existing access tunnels
   beyond an operator-owned gateway collocated with the operator's IPv4
   network edge to the Border Router.  This modification makes it
   unnecessary to provide IPv4 routes to IPv6 UEs.  The gateway serves
   as an aggregation point for IPv4 routing.

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5.2.3. Tunnel Support Protocol (TSP)

   RFC 5572 "IPv6 Tunnel Broker with the Tunnel Setup Protocol (TSP)" M.
   Blanchet and F. Parent, February 2010

   TSP is an Experimental RFC defining a method for a tunnel client to
   negotiate tunnel characteristics with a tunnel broker.  It enables
   tunnels in various deployment architectures including NAT traversal
   and mobility, and for user authentication it utilizes:

   RFC 4422 "Simple Authentication and Security Layer (SASL)" A. Melikov
   ad K. Zeilenga(Eds.) June 2006

5.2.4. Residual IPv4 Deployment over IPv6-only Infrastructure

   Further down the transition road, operators may desire to retire IPv4
   routing support and move their backbone networks to IPv6-only.  There
   may be residual IPv4 legacy customers (clients and servers) still
   requiring the delivery of IPv4 packets.  While the previously
   proposed Dual-Stack Transition Mechanism (DSTM) approach attempted to
   satisfy this use case, it was complex and stateful.  A stateless
   approach to IPv4 residual deployment (4rd) is defined in section 3.2
   of the Stateless Address Mapping (SAM) draft.  At the time of this
   publication, several network operators in Japan are planning
   implementation to support residual IPv4 customers.

   "Stateless Address Mapping (SAM) - a Simplified Mesh-Softwire Model"
   Despres, R. July 12, 2010

   "IPv4 Residual Deployment across IPv6-Service networks (4rd): A NAT-
   less Solution" R. Despres

5.2.5. Address Plus Port (AplusP)

   "The A+P Approach to the IPv4 Address Shortage" R. Bush (Ed.) October
   27, 2009 (expired, but authors indicate a new draft is coming)

   This draft discusses the possibility of address sharing by treating
   some of the port number bits as part of an extended IPv4 address
   (Address plus Port, or A+P).  Instead of assigning a single IPv4

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   address to a customer device, we propose to extended the address by
   "stealing" bits from the port number in the TCP/UDP header, leaving
   the applications a reduced range of ports.  This means assigning the
   same IPv4 address to multiple clients (e.g., CPE, mobile phones),
   each with its assigned port-range.  In the face of IPv4 address
   exhaustion, the need for addresses is stronger than the need to be
   able to address thousands of applications on a single host.  If
   address translation is needed, the end-user should be in control of
   the translation process - not some smart boxes in the core.

   "Aplusp Lite - A light weight aplusp approach" Z. Xiaoyu

   This document proposes a solution aimed at providing IPv4 continuity
   in IPv6 environment. The proposed solution is expected to alleviate
   the public IPv4 depletion problem while maximize the benefits from
   IPv6 deployment, and meet the desired service availability and
   reliability with affordable cost.

5.2.6. IRON-RANGER and ISATAP Solutions

   A body of RFCs and drafts in progress provide an alternative approach
   to IPv4/IPv6 coexistence.  This approach utilizes tunneling
   techniques to create "overlay" networks.  While currently considered
   "Experimental" it may be of interest to network operators as an
   alternative network architecture.

   RFC 5214 "Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)"
   F. Templin et al. March 2008 http://tools.ietf.org/html/rfc5214

   RFC 5579 "Transmission of IPv4 Packets over Intra-Site Automatic
   Tunnel Addressing Protocol (ISATAP) Interfaces" F. Templin (Ed.)
   February 2010 http://tools.ietf.org/html/rfc5579

   RFC 5320 "The Subnetwork Encapsulation and Adaptation Layer (SEAL)"
   F. Templin (Ed.) February 2010 http://tools.ietf.org/html/rfc5320

   Fred Templin originally published SEAL as an Experimental RFC, and is
   currently updating with the intention to publish as Standards Track:

   RFC 5558 "Virtual Enterprise Traversal (VET)" F. Templin (Ed.)
   February 2010 http://tools.ietf.org/html/rfc5558

   Fred Templin originally published VET as an Informational RFC, and is
   currently updating with the intention to publish as Standards Track:

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   RFC 5720 "Routing and Addressing in Networks with Global Enterprise
   Recursion (RANGER)" F. Templin (Ed.) February 2010

   "The Internet Routing Overlay Network (IRON)" F. Templin (Ed.)

5.2.7. Softwires Hub and Spoke with L2TP

   RFC 5571 "Softwire Hub and Spoke Deployment Framework with Layer Two
   Tunneling Protocol Version 2 (L2TPv2)" B. Storer et al. June 2009

   This document describes the framework of the Softwire "Hub and Spoke"
   solution with the Layer Two Tunneling Protocol version 2 (L2TPv2).
   The implementation details specified in this document should be
   followed to achieve interoperability among different vendor

5.3. Translation

   From the earliest specification of IPv6 IETF contributors have
   recognized that translation would be a necessary tool for transition
   and coexistence, as IPv6 was designed as an incompatible replacement
   rather than an extension of IPv4.  The original approach to stateless
   translation defined in RFC 2765 and its implementation as NA(P)T-PT
   as described in RFC 2766 had a number of issues that resulting in the
   approach being deprecated by RFC 4966.  Recently the Behave WG has
   taken on the work of defining a set of scenarios covering the use
   cases for translation, prioritizing the work and defining new
   solutions that overcome the deficiencies of the historic approach.

5.3.1. Historic Approach

   RFC 2765 "Stateless IP/ICMP Translation (SIIT)." E. Nordmark,
   February 2000 http://tools.ietf.org/html/rfc2765

   This document specifies a transition mechanism algorithm in addition
   to the mechanisms already specified in RFC 1933 (note that this
   reference was subsequently obsoleted by RFC 2893 which in turn was
   obsoleted by RFC 4213).  The algorithm translates between IPv4 and
   IPv6 packet headers (including ICMP headers) in separate translator
   "boxes" in the network without requiring any per-connection state in
   those "boxes".  This new algorithm can be used as part of a solution
   that allows IPv6 hosts, which do not have a permanently assigned IPv4
   addresses, to communicate with IPv4-only hosts.  The document neither

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   specifies address assignment nor routing to and from the IPv6 hosts
   when they communicate with the IPv4-only hosts.

   SIIT has been applied in several translation implementations,
   including the historic NAT-PT specified in RFC 2766 and deprecated by
   RFC 4966.  SIIT is currently being revised in "IP/ICMP Translation
   Algorithm" X. Li, C. Bao and F. Baker

   RFC 2766 "Network Address Translation - Protocol Translation (NAT-
   PT)." G. Tsirtsis and P. Srisresh, February 2000

   This solution attempted to provide transparent routing to end-nodes
   in an IPv6 realm trying to communicate with end-nodes in an IPv4
   realm and vice versa.  This combined Network Address Translation and
   Protocol Translation.  While it did mandate dual-stack support or
   special purpose routing requirements (such as requiring tunneling
   support) on end nodes, it did introduce issues that were considered
   harmful enough to lead to its deprecation in July 2007 by RFC 4966
   "Reasons to Move the Network Address Translator - Protocol Translator
   (NAT-PT) to Historic Status" http://tools.ietf.org/html/rfc4966.

   RFC 2767 "Dual-Stack Hosts Using 'Bump in the Stack' Technique (BIS)"
   K. Tsuchiay, H. Higuchi and Y. Atarashi February 2000

   RFC 3338 "Dual-Stack Hosts Using 'Bump in the API' (BIA)" S. Lee, et
   al. October 2002

   These two RFCs are proposed for obsolescence by a draft that combines

   "Dual-Stack Hosts Using 'Bump in the Host'(BIH)" B. Huang, H. Deng
   and T. Savolainen

5.3.2. Current Translation Approaches

   A renewed effort to define new translation mechanisms started with
   discussions in the Internet Area (intarea) meeting and the Technical
   Plenary at IETF 71 in Dublin, and continued at a special meeting in
   Montreal in October 2008.  This led to a commitment by contributors
   in the Behave WG to take on the work.  A set of scenarios were
   defined along with a framework for the translation solutions.

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   "IPv4 Run-Out and IPv4-IPv6 Co-Existence Scenarios" J. Arkko and M.

   When IPv6 was designed, it was expected that the transition from IPv4
   to IPv6 would occur more smoothly and expeditiously than experience
   has revealed.  The growth of the IPv4 Internet and predicted
   depletion of the free pool of IPv4 address blocks on a foreseeable
   horizon has highlighted an urgent need to revisit IPv6 deployment
   models.  This document provides an overview of deployment scenarios
   with the goal of helping to understand what types of additional tools
   the industry needs to assist in IPv4 and IPv6 co-existence and

   This document was originally created as input to the Montreal co-
   existence interim meeting in October 2008, which led to the
   rechartering of the Behave and Softwire working groups to take on new
   IPv4 and IPv6 coexistence work.  This document is published as a
   historical record of the thinking at the time.

   "A Framework for IPv4/IPv6 Translation" F. Baker et al.

   This draft (Framework) is the place to start to understand the
   historic context for translation, the definition and rationale for
   the set of translation scenarios and canonical definitions for some
   of the terminology that arises when talking about translation and
   coexistence in general.

   The 4 deployment modes for these scenarios are:

   1. Connecting between the IPv4 Internet and the IPv6 Internet

   2. Connecting an IPv6 network to the IPv4 Internet

   3. Connecting an IPv4 network to the IPv6 Internet

   4. Connecting between an IPv4 network and an IPv6 network

   As solutions may differ with respect to the initiating end of the
   conversation, 8 scenarios are defined in the Framework draft, as
   recapped in the following sections along with specifications that fit
   each scenario.

   Some general specifications that are cited in the various solution
   specifications (or may be in subsequent revisions) are:

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   "IPv6 Addressing of IPv4/IPv6 Translators" C. Bao et al. August 16,
   2010 http://tools.ietf.org/html/draft-ietf-behave-address-format-10

   "DNS64: DNS extensions for Network Address Translation from IPv6
   Clients to IPv4 Servers" M. Bagnulo et al.  July 5, 2010

   "Analysis of 64 Translation" R. Penno, T. Saxena and D. Wing

   Due to specific problems, NAT-PT was deprecated by the IETF as a
   mechanism to perform IPv6-IPv4 translation.  Since then, new effort
   has been undertaken within IETF to standardize alternative mechanisms
   to perform IPv6-IPv4 translation.  This document evaluates how the
   new translation mechanisms avoid the problems that caused the IETF to
   deprecate NAT-PT. An IPv6 network to the IPv4 Internet

   The Framework defines Scenario 1 for an early adopter (end user or
   network operator) which establishes an IPv6 network and needs to
   maintain access to the global IPv4 Internet, preferably without
   assigning IPv4 addresses to the nodes of the IPv6 network.  Either
   the Stateful or Stateless solutions proposed may satisfy this
   deployment scenario.

   "Stateful NAT64: Network Address and Protocol Translation from IPv6
   Clients to IPv4 Servers" M. Bagnulo, P. Matthews and I. van Beijnum

   "IP/ICMP Translation Algorithm" X. Li, C. Bao and F. Baker
   http://tools.ietf.org/html/draft-ietf-behave-v6v4-xlate The IPv4 Internet to an IPv6 network

   The Framework defines Scenario 2 for a node on the IPv4 Internet
   initiating a transmission to a node on an IPv6 network.  The original
   approach to this deployment was the NAT-PT implementation of SIIT (as
   defined in RFC 2766) which has been deprecated (by RFC 4966).  The
   Stateless Translation solution for Scenario 1 also would work for
   this case as it does support IPv4-initiated communication with a
   subset of IPv6 addresses. The IPv6 Internet to an IPv4 network

   The Framework defines Scenario 3 where a legacy IPv4 network has a
   requirement to provide services to users in the IPv6 Internet.

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   Stateful Translation with static AAAA records in DNS to represent the
   IPv4-only hosts will work.

   "Stateful NAT64: Network Address and Protocol Translation from IPv6
   Clients to IPv4 Servers" M. Bagnulo, P. Matthews and I. van Beijnum

   "DNS64: DNS extensions for Network Address Translation from IPv6
   Clients to IPv4 Servers" M. Bagnulo et al.

   Alternatively, host-based translation (BIH) or tightly-coupled
   translators may be considered. An IPv4 network to the IPv6 Internet

   Scenario 4 is not easy to solve but fortunately will not arise until
   significant IPv6 uptake.  In-network translation is not viable, and
   other techniques should be considered including host-based
   translation (BIH) or tightly-coupled translators that adapt legacy
   hosts or networks to the IPv6 Internet. An IPv6 network to an IPv4 network

   Scenario 5 describes a configuration where both the IPv6 network and
   IPv4 network are within the administrative control of the same
   organization.  It appears amenable to the same solutions proposed for
   Scenario 1. An IPv4 network to an IPv6 network

   Scenario 6 is the mirror image of Scenario 5, with communication
   initiated from the IPv4 side.  It appears amenable to the same
   solution proposed for Scenario 2. The IPv6 Internet to the IPv4 Internet

   The Framework indicates that Scenario 7, the interconnection of the
   IPv4 Internet with the IPv6 Internet may appear to be an ideal case
   for an in-network translator (such as the deprecated NAT-PT), but
   there is no viable way to map the immense IPv6 address space onto
   IPv4.  This situation would not entail until significant IPv6
   adoption, and has not been a priority for solution. The IPv4 Internet to the IPv6 Internet

   Scenario 8 presents a challenge similar to Scenario 7.

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5.4. Connectivity Checking and Delay Avoidance

   One important issue that arises in a coexistence environment is
   negative impact on the initiation of peer-to-peer connections, such
   as VoIP, video, etc.  The initiator doesn't know a priori whether the
   peer is using the same address family incurring a possible delay as
   the first attempt may fail. There is also ambiguity, as the IPv6 path
   may be temporarily broken.

   "IPv6 Connectivity Check and Redirection by HTTP Servers" E. Vyncke

   Rather than forcing the client to decide whether IPv4 or IPv6 is more
   convenient to reach a web server; this document proposes to let the
   web server check whether there is IPv6 connectivity to the client;
   then the web server can do a HTTP redirect to the force the client to
   use IPv6.

   This is done easily by a script within the server HTML pages and does
   not require any change in the client applications or configuration.
   The client still can control whether he/she wants to enabled IPv6.

   "Happy Eyeballs:  Trending Towards Success (IPv6 and SCTP)", D. Wing,
   A. Yourtchenko, P. Natarajan.

   This draft makes several recommendations to ensure user satisfaction
   and a smooth transition from HTTP's pervasive IPv4 to IPv6 and from
   TCP to SCTP.  While the target audience is app developers and content
   providers, network operators should be aware of techniques needed to
   maintain peaceful coexistence without negative impact on end-user
   perception of service level.

   "Migrating SIP to IPv6 Media Without Connectivity Checks" D. Wing, A.

   During the migration from IPv4 to IPv6, it is anticipated that an
   IPv6 path might be broken for a variety of reasons, causing endpoints
   to not receive RTP data.  Connectivity checks would detect and avoid
   the user noticing such a problem, but there is industry reluctance to
   implement connectivity checks.

   This document describes a mechanism allowing dual-stack SIP endpoints
   to attempt communications over IPv6 and fall back to IPv4 if the IPv6
   path is not working.  The mechanism does not require connectivity

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6. Prefix and Address Assignment and Distribution

   RFC 4291 "IP Version 6 Addressing Architecture." R. Hinden, S.
   Deering. February 2006.

   RFC 5952 "A Recommendation for IPv6 Text Representation" S. Kawamura
   and M. Kawashima, August 2010

   RFC 4291 defines the addressing architecture of the IP Version 6
   (IPv6) protocol.  The document includes the IPv6 addressing model,
   text representations of IPv6 addresses, definition of IPv6 unicast
   addresses, anycast addresses, and multicast addresses, and an IPv6
   node's required addresses.  RFC 5952 updates RFC 4291 with a
   recommended method for rendering IPv6 addresses in a standard form
   for user interfaces, logging and reporting.

   "IPv6 Addressing of IPv4/IPv6 Translators" C. Bao et al. (Status:
   Standards Track, in RFC Editor will update RFC 4291)

   This document discusses the algorithmic translation of an IPv6
   address to a corresponding IPv4 address, and vice versa, using only
   statically configured information.  It defines a well-known prefix
   for use in algorithmic translations, while allowing organizations to
   also use network-specific prefixes when appropriate.  Algorithmic
   translation is used in IPv4/IPv6 translators, as well as other types
   of proxies and gateways (e.g., for DNS) used in IPv4/IPv6 scenarios.

   RFC 3177 "IAB/IESG Recommendations on IPv6 Address Allocations to
   Sites." IAB, IESG. September 2001.

   RFC 3177 provides recommendations to the addressing registries
   (APNIC, ARIN and RIPE-NCC) on policies for assigning IPv6 address
   blocks to end sites.  In particular, it recommends the assignment of
   /48 in the general case, /64 when it is known that one and only one
   subnet is needed and /128 when it is absolutely known that one and
   only one device is connecting.

   "IPv6 Address Assignment to End Sites", T. Narten, G. Huston, R.
   Roberts, 12-Jul-10

   The proposed update to RFC 3177 revises the recommendation to leave
   the exact choice to the operational community.  The role of the IETF

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   is limited to providing guidance on IPv6 architectural and
   operational considerations.  This document reviews the architectural
   and operational considerations of end site assignments as well as the
   motivations behind the original 3177 recommendations.  Moreover, the
   document clarifies that a one-size-fits-all recommendation of /48 is
   not nuanced enough for the broad range of end sites and is no longer
   recommended as a single default.

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

   RFC 5942 "IPv6 Subnet Model: The Relationship between Links and
   Subnet Prefixes." H. Singh, W. Beebee, E. Nordmark. July 2010.

   IPv6 specifies a model of a subnet that is different than the IPv4
   subnet model.  The subtlety of the differences has resulted in
   incorrect implementations that do not interoperate.  This document
   spells out the most important difference: that an IPv6 address isn't
   automatically associated with an IPv6 on-link prefix.  This document
   also updates (partially due to security concerns caused by incorrect
   implementations) a part of the definition of "on-link" from RFC 4861.

   RFC 4862 "IPv6 Stateless Address Autoconfiguration." S. Thomson, T.
   Narten, T. Jinmei. September 2007.

   RFC 4941 "Privacy Extensions for Stateless Address Autoconfiguration
   in IPv6." T. Narten, R. Draves, S. Krishnan. September 2007.

   The IPv6 addressing architecture presumes that the remaining 64 bits
   are an endpoint interface identifier.  This could be the MAC Address
   (EUI-64 Address) in an appropriate encoding, or it could be what is
   called a "privacy address", which is a random number.  You will find
   the most common approach to that, for hosts, in this RFC.

   RFC 3315 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)." R.
   Droms (Ed.), J. Bound, B. Volz, T. Lemon, C. Perkins, M. Carney. July
   2003.  http://tools.ietf.org/html/rfc3315

   "Analysis of Solution Proposals for hosts to learn NAT64 Prefixes" J.
   Korhonen (Ed.) and T. Savolainen

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   Hosts and applications may benefit from the knowledge if an IPv6
   address is synthesized, which would mean a NAT64 is used to reach the
   IPv4 network or Internet.  This document analyses number of proposed
   solutions for communicating if the synthesis is taking place, used
   address format, and the IPv6 prefix used by the NAT64 and DNS64.
   This enables both NAT64 avoidance and intentional utilization by
   allowing local IPv6 address synthesis.

7. How-to, Whitepapers and FAQs

   "IPv6 Rollout: Where do we start?" O. Crepin-Leblond

   "Everything Sysadmin" T. Limoncelli

   "IPv6 Deployment in Internet Exchange Points (IXPs)", Roque Gagliano

   This draft suggests that in an Internet Exchange Point one might use
   an address that helps in debugging routing exchanges.  One could also
   look at what other folks do, embedding identifying marks in
   addresses.  For example, Facebook includes "face:b00c" in the IID
   portion of their address.

8. Experiments, Trials and Prototypes

   6bone (concluded)

   Hurricane Electric (ongoing)

   T-Mobile USA (ongoing)

   Comcast (ongoing)

   Internode ADSL (Ongoing)

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   Verizon FiOS (small scale test - concluded)

   "Considerations for Stateless Translation (IVI/dIVI) in Large SP
   Network" Q. Sun et al.

   In addition to the deployment use case this draft describes, the
   draft documents an experimental use of the translation in a research

   Measurements of IPv6 Path MTU Discovery Behavior

9. Implementation Reports

   "A Basic Guideline for Listing ISPs that Run IPv6" S. Kawamura

   This draft attempts to gather information about currently known sites
   that rate ISP readiness for IPv6 and to look at their evaluation
   methods.  This document also summarizes basic guidelines that these
   listings may consider when checking an ISPs IPv6 readiness.  As the
   draft says, there are many opinions about what it means to be ready
   for IPv6, and it would be helpful to evaluate ISPs based on some
   common criteria.

   IPv6 Rapid Deployment

   Google has hosted a meeting of IPv6 Implementers in 2009 and 2010,
   several presentations covered experimental or live transition

10. Books on IPv6

   Blanchet, Marc. "Migrating to IPv6: a Practical Guide to Implementing
   IPv6 in Mobile and Fixed Networks." Chichester, England: J. Wiley &
   Sons, 2006. Print.

   Hagen, Silvia. "IPv6 Essentials - Second Edition" Sebastapol, CA:
   O'Reilly Media, Inc, 2006.  Print.

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   Loshin, Peter.  "IPv6, Second Edition: Theory, Protocol and Practice"
   Morgan Kaufmann Publishing, 2003

   Popoviciu, Ciprian, Eric Levy-Abengoli and Patrick Grossetete
   "Deploying IPv6 Networks" Indianapolis, IN:  Cisco Press, 2006.

   Siil, Karl A. "IPv6 Mandates: Choosing a Transition Strategy,
   Preparing Transition Plans, and Executing the Migration of a Network
   to IPv6."  Indianapolis, IN: Wiley, 2008. Print.

11. Miscellaneous

   See the Dancing Turtle, but only if you have native IPv6!

   A little more detail than a Dancing Turtle, on your IPv6 readiness
   can be obtained by using this site put up by Jason Fesler:

   There is an extension for Firefox (and perhaps other browsers) that
   displays the IP address of web pages you visit, clearly indicating
   when you are connected via IPv4 or IPv6.  In Firefox, click on
   Tools..Add-ons..Extensions and search for ShowIP.

   Eric Vyncke is collecting some statistics on IPv6 penetration.

   A reasonable estimation of how fast the sky is falling.

   A graphical representation of IPv4 depletion.

   "IPv6 Adoption Remains Slow, Survey Says" W. Jackson, GCN Sept. 5,

   Some troubling, yet interesting news about what operators and end-
   user organizations are thinking about IPv6 adoption at this time.

   A study of some of the brokenness around Path MTU Discovery

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   Cluenet hosts a mailing list with IPv6 operator participation.
   Various transition-related topics are brought up there from time to

   "IPv6 for Dummies, Part 1:  It's Time!"

   "IPv6 for Dummies, Part 2:  Comparing IPv4 and IPv6"

12. Security Considerations

   This draft does not introduce any security considerations.

13. IANA Considerations

   This draft does not require any action from IANA.

   [Note to RFC Editor: this section may be removed.]

14. Conclusions

   This draft is merely the starting point for a network operator
   planning an IPv6 rollout.  The intention of the editor was to
   document the great work that is already available that can help in
   the process and to perhaps save a few hours of redundant effort for
   someone to find this information.  Of course, this will be out of
   date before it is published as active research continues in
   coexistence and transition tools.  The editor hopes it is at least a
   useful "You Are Here" map to help navigate the thrill rides available
   in the IPv6 theme park.

   This compendium could serve as an initial set of data to populate an
   active database or wiki.  This would allow continuing community
   contribution including feedback on the real-world experience of
   network operators as they turn on IPv6.

15. References

15.1. Normative References


15.2. Informative References

   Complete reference information is included in the body of the draft.

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16. Acknowledgments

   This bibliography is a recapitulation of the contributions of the
   authors of the cited RFCs, drafts, websites and other publications
   and many folks on the v6ops and v4v6transition mailing lists, the
   editor has freely borrowed abstract and summary text from the cited
   works and e-mail postings.  In addition, the editor wishes to
   acknowledge significant contributions and suggestions from Fred
   Baker, Brian Carpenter, Remi Despres, Suresh Krishnan, Tina Tsou, Yiu
   Lee, Marc Blanchet, Med Boucadair, Fred Templin, Andrew Yourtchenko
   and many contributors on the v4v6trans mailing list.  All credit is
   due to those contributors while the editor takes responsibility for
   any errors, omissions or mischaracterization of the work in the
   process of abstracting and summarizing it here.

   The IPv4-IPv6 Transition mailing list archive can be found at:
   https://www.ietf.org/mailman/listinfo/v4tov6transition and the
   readers are also directed to the mailing list archives of the various
   IETF Working Groups mentioned for the history of the cited drafts and

   This document was prepared using 2-Word-v2.0.template.dot.

Author's Address

   Edward J. Jankiewicz
   SRI International, Inc.
   333 Ravenswood Ave
   Menlo Park, CA USA

   Phone: 732-389-1003 or 650-859-2000
   Email: edward.jankiewicz@sri.com

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