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Versions: 00 01 02 03 draft-ietf-v6ops-icp-guidance

V6OPS                                                       B. Carpenter
Internet-Draft                                         Univ. of Auckland
Intended status: Informational                                  S. Jiang
Expires: April 24, 2012                     Huawei Technologies Co., Ltd
                                                        October 22, 2011

  IPv6 Guidance for Internet Content and Application Service Providers


   This document provides guidance and suggestions for Internet Content
   Providers and Application Service Providers who wish to offer their
   service to both IPv6 and IPv4 customers.

Status of this Memo

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

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

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

   This Internet-Draft will expire on April 24, 2012.

Copyright Notice

   Copyright (c) 2011 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
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  General Strategy . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Education and Skills . . . . . . . . . . . . . . . . . . . . .  4
   4.  Arranging IPv6 Connectivity  . . . . . . . . . . . . . . . . .  5
   5.  IPv6 Infrastructure  . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  Address and subnet assignment  . . . . . . . . . . . . . .  6
     5.2.  Routing  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     5.3.  DNS  . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Load Balancers . . . . . . . . . . . . . . . . . . . . . . . .  7
   7.  Proxies  . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   8.  Servers  . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     8.1.  Network Stack  . . . . . . . . . . . . . . . . . . . . . .  8
     8.2.  Application Layer  . . . . . . . . . . . . . . . . . . . .  9
     8.3.  Geolocation  . . . . . . . . . . . . . . . . . . . . . . .  9
   9.  Coping with Transition Technologies  . . . . . . . . . . . . .  9
   10. Content Delivery Networks  . . . . . . . . . . . . . . . . . . 11
   11. Operations and Management  . . . . . . . . . . . . . . . . . . 11
   12. Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   13. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
   15. Change log [RFC Editor: Please remove] . . . . . . . . . . . . 13
   16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     16.1. Normative References . . . . . . . . . . . . . . . . . . . 13
     16.2. Informative References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15

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1.  Introduction

   The deployment of IPv6 [RFC2460] is now in progress, and users with
   no IPv4 access are likely to appear in increasing numbers in the
   coming years.  Any provider of content or application services over
   the Internet will need to arrange for IPv6 access or else risk losing
   large numbers of potential customers.  The time for action is now,
   while the number of such customers is small, so that appropriate
   skills, software and equipment can be acquired in good time to scale
   up the IPv6 service as demand increases.

   It is important that the introduction of IPv6 service should not make
   service for IPv4 customers worse.  In some circumstances,
   technologies intended to assist in the transition from IPv4 to IPv6
   are known to have negative effects on the user experience.  A
   deployment strategy for IPv6 must avoid these effects as much as

   The purpose of this document is to provide guidance and suggestions
   for Internet Content Providers (ICPs) and Application Service
   Providers (ASPs) who wish to offer their service to both IPv6 and
   IPv4 customers.  For simplicity, the term ICP is mainly used in the
   body of this document, but the guidance also applies to ASPs.
   Although specific managerial and technical approaches are described,
   this is not a rule book; each provider will need to make its own
   plan, tailored to its own services and customers.

2.  General Strategy

   The most importance advice here is to actually have a general
   strategy.  Adding support for a second network layer protocol is a
   new departure for most modern organisations, and it cannot be done
   casually on a day-by-day basis.  Even if it is impossible to write a
   precisely dated plan, the intended steps in the process need to be
   defined well in advance.  There is no single blueprint for this.  The
   rest of this document is meant to provide a set of topics to be taken
   into account in defining the strategy.

   In determining the urgency of this strategy, it should be noted that
   the central IPv4 registry (IANA) ran out of spare blocks of IPv4
   addresses in February 2011 and the various regional registries are
   expected to exhaust their reserves over the next one to two years.
   After this, Internet Service Providers (ISPs) will run out at dates
   determined by their own customer base.  No precise date can be given
   for when IPv6-only customers will appear in commercially significant
   numbers, but - particularly in the case of mobile users - it may be
   quite soon.  Complacency about this is therefore not an option for

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   any ICP that wishes to grow its customer base over the coming years.

   The only rational strategy for an ICP is to provide dual stack
   services - both IPv4 and IPv6 on an equal basis - to cover both
   existing and future customers.  This is the recommended strategy in
   [RFC6180] for straightforward situations.  Within the dual stack
   model, two approaches could be adopted, sometimes referred to as
   "outside in" and "inside out":

   o  Outside in: start by providing external users with an IPv6 public
      access to your services, for example by running a reverse proxy
      that handles IPv6 customers (see Section 7 for details).
      Progressively enable IPv6 internally.
   o  Inside out: start by enabling internal networking infrastructure,
      hosts, and applications to support IPv6.  Progressively reveal
      IPv6 access to external customers.

   Which of these approaches to adopt depends on the precise
   circumstances of the ICP concerned.  "Outside in" has the benefit of
   giving interested customers IPv6 access at an early stage, and
   thereby gaining precious operational experience, before meticulously
   updating every piece of equipment and software.  For example, if some
   back-office system, that is never exposed to users, only supports
   IPv4, it will not cause delay.  "Inside out" has the benefit of
   completing the implementation of IPv6 as a single project.  Any ICP
   could choose this approach, but it might be most appropriate for a
   small ICP without complex back-end systems.

   A point that must be considered in the strategy is that some
   customers will remain IPv4-only for many years, others will have both
   IPv4 and IPv6 access, and yet others will have only IPv6.
   Additionally, mobile customers may find themselves switching between
   IPv4 and IPv6 access as they travel, even within a single session.
   Services and applications must be able to deal with this, just as
   easily as they deal today with a user whose IPv4 address changes (see
   the discussion of cookies in Section 8.2).

   An important first step in every strategy is to determine from every
   hardware and software supplier details of their planned dates for
   providing full IPv6 support in their products and services.

3.  Education and Skills

   Some older staff may have experience of running multiprotocol
   networks, which were common twenty years ago before the dominance of
   IPv4.  However, IPv6 will be new to them, and also to younger staff
   brought up on TCP/IP.  It is not enough to have one "IPv6 expert" in

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   a team.  On the contrary, everybody who knows about IPv4 needs to
   know about IPv6, from network architect to help desk responder.
   Therefore, an early and essential part of the strategy must be
   education, including practical training, so that all staff acquire
   a general understanding of IPv6, how it affects basic features
   such as the DNS, and the relevant practical skills.  To take a
   trivial example, any staff used to dotted-decimal IPv4 addresses need
   to become familiar with the colon-hexadecimal format used for IPv6.

   There is an anecdote of one IPv6 deployment in which prefixes
   including the letters A to F were avoided by design, to avoid
   confusing sysadmins unfamiliar with hexadecimal notation.  This is
   not a desirable result.  There is another anecdote of a help desk
   responder telling a customer to "disable one-Pv6" in order to solve a
   problem.  It should be a goal to avoid having untrained staff who
   don't understand hexadecimal or who can't even spell "IPv6".

   It is very useful to have a small laboratory network available for
   training and self-training in IPv6, where staff may experiment and
   make mistakes without disturbing the operational IPv4 service.  This
   lab should run both IPv4 and IPv6, to gain experience with a dual-
   stack environment and new features such as having multiple addresses
   per interface.

4.  Arranging IPv6 Connectivity

   There are, in theory, two ways to obtain IPv6 connectivity to the

   o  Native.  In this case the ISP simply provides IPv6 on exactly the
      same basis as IPv4 - it will appear at the ICP's border router(s),
      which must then be configured in dual-stack mode to forward IPv6
      packets in both directions.  This is by far the better method.  An
      ICP should contact all its ISPs to verify when they will provide
      native IPv6 support, whether this has any financial implications,
      and whether the same service level agreement will apply as for
      IPv4.  Any ISP that has no definite plan to offer native IPv6
      service should be avoided.
   o  Tunnel.  It is possible to configure an IPv6-in-IPv4 tunnel to a
      remote ISP that offers such a service.  A dual-stack router in the
      ICP's network will act as a tunnel end-point, or this function
      could be included in the ICP's border router.

      A tunnel is a reasonable way to obtain IPv6 connectivity for
      initial testing and skills acquisition.  However, it introduces an
      inevitable extra latency compared to native IPv6, giving users a
      noticeably worse response time for complex web pages.  It is also

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      likely to limit the IPv6 MTU size.  In normal circumstances,
      native IPv6 will provide an MTU size of at least 1500 bytes, but
      it will almost inevitably be less for a tunnel, possibly as low as
      1280 bytes (the minimum MTU allowed for IPv6).  Apart from the
      resulting loss of efficiency, there are cases in which Path MTU
      Discovery fails, therefore IPv6 fragmentation fails, and in this
      case the lower tunnel MTU will actually cause connectivity
      failures for customers.

      For these reasons, ICPs are strongly recommended to obtain native
      IPv6 service before attempting to offer a production-quality
      service to their users.

5.  IPv6 Infrastructure

5.1.  Address and subnet assignment

   An ICP must first decide whether to apply for its own Provider
   Independent (PI) address prefix for IPv6.  The default is to obtain a
   Provider Aggregated (PA) prefix from each of its ISPs, and operate
   them in parallel.  Both solutions are viable in IPv6.  However, the
   wide area routing system (BGP4) can only support a limited number of
   routes for PI prefixes, so only the largest providers can justify the
   bother and expense of obtaining a PI prefix and convincig their ISPs
   to route it.  Millions of enterprise networks will use PA prefixes.
   In this case, a change of ISP would necessitate a change of the
   corresponding PA prefix, using the procedure outlined in [RFC4192].

   An ICP that has multiple connections via multiple ISPs will have
   multiple PA prefixes.  This commonly results in multiple PA-based
   addresses for the servers.

   An ICP may also choose to operate a Unique Local Address prefix
   [RFC4193] for internal traffic only, as described in [RFC4864].

   Depending on its projected future size, an ICP might choose to obtain
   /48 PI or PA prefixes (allowing 16 bits of subnet address) or longer
   PA prefixes, e.g. /56 (allowing 8 bits of subnet address).  Clearly
   the choice of /48 is more future-proof.  Advice on the numbering of
   subnets may be found in [RFC5375].

   Since IPv6 provides for operating multiple prefixes simultaneously,
   it is important to check that all relevant tools, such as address
   management packages, can deal with this.

   Theoretically, it would be possible to operate an ICP's IPv6 network
   using only Stateless Address Autoconfiguration [RFC4862].  In

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   practice, an ICP of reasonable size will probably choose to operate
   DHCPv6 [RFC3315] and use it to support stateful and/or on-demand
   address assignment.

5.2.  Routing

   In a dual stack network, IPv4 and IPv6 routing protocols operate
   quite independently and in parallel.  The common routing protocols
   all exist in IPv6 versions, such as OSPFv3 [RFC5340].  For trained
   staff, there should be no particular difficulty in deploying IPv6
   routing without disturbance to IPv4 services.

5.3.  DNS

   This is largely a case of "just do it."  Each externally visible host
   (or virtual host) that has an A record for its IPv4 address needs an
   AAAA record [RFC3596] for its IPv6 address, and a reverse entry if
   applicable.  One important detail is that some clients (especially
   Windows XP) can only reslove DNS names via IPv4, even if they can use
   IPv6 for application traffic.  It is therefore advisable for all DNS
   servers to respond to queries via both IPv4 and IPv6.

6.  Load Balancers

   It is to be expected that IPv6 traffic will initially be low, i.e. a
   small percentage of IPv4 traffic.  For this reason, updating load
   balancers to fully support IPv6 can perhaps be delayed; however, such
   an update needs to be planned in anticipation of significant growth
   over a period of several years.  The same would apply to TLS or HTTP
   proxies used for load balancing purposes.

7.  Proxies

   An HTTP proxy [RFC2616] can readily be configured to handle incoming
   connections over IPv6 and to proxy them to a server over IPv4.
   Therefore, a single proxy can be used as the first step in an
   outside-in strategy, as shown in the following diagram:

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       (                                           )
       (        IPv6 Clients in the Internet       )
                      |  Ingress  |
                      |  router   |
                      | IPv6 stack|
                      | HTTP proxy|
                      | IPv4 stack|
                      | IPv4 stack|
                      |   HTTP    |
                      |  server   |

   In this case, the AAAA record for the service would provide the IPv6
   address of the proxy.  This approach will work for any HTTP or HTTPS
   applications that operate successfully via a proxy, as long as IPv6
   load remains low.

8.  Servers

8.1.  Network Stack

   The TCP/IP network stacks in popular operating systems have supported
   IPv6 for many years.  In most cases, it is sufficient to enable IPv6
   and possibly DHCPv6; the rest will follow.  Servers inside an ICP
   network will not need to support any transition technologies beyond a
   simple dual stack, with a possible exception for 6to4 mitigation
   noted below in Section 9.

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8.2.  Application Layer

   Basic HTTP servers have been able to handle an IPv6-enabled network
   stack for some years, so at the most it will be necessary to update
   to a more recent software version.  The same is true of generic
   applications such as email protocols.  No general statement can be
   made about other applications, especially proprietary ones, so each
   ASP will need to make its own determination.

   One important recommendation here is that all applications should use
   domain names, which are IP-version-independent, rather than IP
   addresses.  Applications based on middlware platforms which have
   uniform support for IPv4 and IPv6, for example Java, may be able to
   support both IPv4 and IPv6 naturally without additional work.

   A specific issue for HTTP-based services is that IP address-based
   cookie authentication schemes will need to deal with dual-stack
   clients.  Servers might create a cookie for an IPv4 connection or an
   IPv6 connection, depending on the setup at the client site and on the
   whims of the client operating system.  There is no guarentee that a
   given client will consistently use the same address family,
   especially when accessing a collection of sites rather than a single
   site.  If the client is using privacy addresses [RFC4941], the IPv6
   address (but not its /64 prefix) might change quite frequently.  Any
   cookie mechanism based on 32-bit IPv4 addresses will need significant

   Generic considerations on application transition are discussed in
   [RFC4038], but many of them will not apply to the dual-stack ICP
   scenario.  An ICP that creates and maintains its own applications
   will need to review them for any dependency on IPv4.

8.3.  Geolocation

   As time goes on, it is to be assumed that geolocation methods and
   databases will be updated to fully support IPv6 prefixes.  There is
   no reason they will be more or less accurate in the long term than
   those available for IPv4.  However, we can expect many more clients
   to be mobile as time goes on, so geolocation based on IP addresses
   alone may become problematic.  Initially, at least, ICPs may observe
   some weakness in geolocation for IPv6 clients.

9.  Coping with Transition Technologies

   As mentioned above, an ICP should obtain native IPv6 connectivity
   from its ISPs.  In this way, the ICP can avoid most of the
   complexities of the numerous IPv4-to-IPv6 transition technologies

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   that have been developed; they are all second-best solutions.
   However, some clients are sure to be using such technologies.  An ICP
   needs to be aware of the operational issues this may cause and how to
   deal with them.

   In some cases, clients may reach an ICP service via a network-layer
   translator between IPv4 and IPv6.  ICPs who are offering a dual stack
   service, as recommended in this document, should not normally see
   traffic from NAT64 translators [RFC6146].  Exceptionally, such
   traffic could arrive via IPv4 from an IPv6-only client whose DNS
   resolver failed to receive the ICP's AAAA record, but this would be
   indistinguishable from a regular IPv4-via-NAT customer.  Similarly,
   ICPs who are offering a dual stack service might exceptionally see
   IPv6 traffic translated from an IPv4-only client that somehow failed
   to receive the ICP's A record.  This would only be an issue if the
   ICP was offering any service that depends on the assumption of end-
   to-end IPv6 address transparency.

   In other cases, clients may reach the IPv6 network via some form of
   IPv6-in-IPv4 tunnel.  In this case a variety of problems can arise,
   the most acute of which affect clients connected using the Anycast
   6to4 solution [RFC3068].  Advice on how ICPs may mitigate these 6to4
   problems is given in Section 4.5. of [RFC6343].  For the benefit of
   all tunnelled clients, it is essential to verify that Path MTU
   Discovery works correctly (i.e., the relevant ICMPv6 packets are not
   blocked) and that the server-side TCP implementation correctly
   supports the Maximum Segment Size (MSS) negotiation mechanism
   [RFC2923] for IPv6 traffic.

   Some ICPs have implemented an interim solution to mitigate transition
   problems by limiting the visibility of their AAAA records to users
   with validated IPv6 connectivity

   Another approach taken by some ICPs is to offer IPv6-only support via
   a specific DNS name, e.g., ipv6.example.com, if the primary service
   is www.example.com.  In this case ipv6.example.com would have an AAAA
   record only.  This has some value for testing purposes, but is
   otherwise only of interest to hobbyist users willing to type in
   special URLs.

   There is little an ICP can do to deal with client-side or remote ISP
   deficiencies in IPv6 support, but it is hoped that the "happy
   eyeballs" [I-D.ietf-v6ops-happy-eyeballs] approach will improve the
   ability for clients to deal with such problems.

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10.  Content Delivery Networks

   DNS-based techniques for diverting users to Content Delivery Network
   (CDN) points of presence (POPs) will work for IPv6, if AAAA records
   are provided as well as A records.  In general the CDN should follow
   the recommendations of this document, especially by operating a full
   dual stack service at each POP.  Additionally, each POP will need to
   handle IPv6 routing exactly like IPv4, for example running BGP4+
   [RFC4760] if appropriate.

   Note that if an ICP supports IPv6 but its CDN does not, its clients
   will continue to use IPv4 and any IPv6-only clients will have to use
   a transition solution of some kind.  This is not a desirable
   situation, since the ICP's work to support IPv6 will be wasted.  The
   converse is not true: if the CDN supports IPv6 but the ICP does not,
   dual-stack and IPv6-only clients will obtain IPv6 access.

   An ICP might face a complex situation, if its CDN provider supports
   IPv6 at some POPs but not at others.  IPv6-only clients could only be
   diverted to a POP supporting IPv6.  There are also scenarios where a
   dual-stack client would be diverted to a mixture of IPv4 and IPv6
   POPs for different URLs, according to the A and AAAA records provided
   and the availability of optimisations such as "happy eyeballs."
   These complications do not affect the viability of relying on a dual-
   stack CDN, however.

   The CDN itself faces related complexity: "As IPv6 rolls out, it's
   going to roll out in pockets, and that's going to make the routing
   around congestion points that much more important but also that much
   harder," stated John Summers of Akamai in 2010.

11.  Operations and Management

   Whatever management, monitoring and logging is performed for IPv4 is
   also needed for IPv6.  Therefore, all products and tools used for
   these purposes must be updated to fully support IPv6.  Note that
   since an IPv6 network may operate with more than one IPv6 prefix and
   therefore more than one address per host, the tools must deal with
   this as a normal situation.

   As far as possible, however, mutual dependency between IPv4 and IPv6
   operations should be avoided.  A failure of one should not cause a
   failure of the other.  One precaution to avoid this is that back-end
   systems such as network management databases should themselves be
   dual stacked.  It should be possible to use IPv4 connectivity to
   repair IPv6 configurations, and vice versa.

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12.  Security Considerations

   Essentially every threat that exists for IPv4 exists or will exist
   for IPv6.  Therefore, it is essential to update firewalls, intrusion
   detection systems, and security auditing technology to fully support
   IPv6.  Otherwise, IPv6 will become an attractive target for

   In a dual stack operation, there may be a risk of cross-contamination
   between the two protocols.  For example, a successful IPv4-based
   denial of service attack might also deplete resources needed by the
   IPv6 service, or vice versa.  This risk strengthens the argument that
   IPv6 security must be up to the same level as IPv4.

   A general overview of techniques to protect an IPv6 network against
   external attack is given in [RFC4864].  Assuming an ICP has native
   IPv6 connectivity, it is advisable to block incoming IPv4-in-IPv6
   tunnel traffic using IPv4 protocol type 41.  Outgoing traffic of this
   kind should be blocked except for the case noted in Section 4.5 of
   [RFC6343].  ICMPv6 traffic should only be blocked in accordance with
   [RFC4890]; in particular, Packet Too Big messages, which are
   essential for PMTU discovery, must not be blocked.

   Scanning attacks to discover the existence of hosts are much less
   likely to succeed for IPv6 than for IPv4 [RFC5157].

   Transport Layer Security version 1.2 [RFC5246] and its predecessors
   work correctly with TCP over IPv6, meaning that HTTPS-based security
   solutions are immediately applicable.  The same should apply to any
   other transport-layer or application-layer security techniques.

   If an ICP or ASP uses IPsec [RFC4301] and IKE [RFC5996] in any way to
   secure connections with clients, these too are fully applicable to
   IPv6, but only if the software stack at each end has been
   appropriately updated.

13.  IANA Considerations

   This document requests no action by IANA.

14.  Acknowledgements

   Valuable comments and contributions were made by Erik Kline.

   This document was produced using the xml2rfc tool [RFC2629].

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15.  Change log [RFC Editor: Please remove]

   draft-carpenter-v6ops-icp-guidance-00: original version, 2011-10-22.

16.  References

16.1.  Normative References

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

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3596]  Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
              "DNS Extensions to Support IP Version 6", RFC 3596,
              October 2003.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              January 2007.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, July 2008.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 5996, September 2010.

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16.2.  Informative References

              Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", draft-ietf-v6ops-happy-eyeballs-04
              (work in progress), September 2011.

              Livingood, J., "Considerations for Transitioning Content
              to IPv6",
              (work in progress), October 2011.

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              June 1999.

   [RFC2923]  Lahey, K., "TCP Problems with Path MTU Discovery",
              RFC 2923, September 2000.

   [RFC3068]  Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
              RFC 3068, June 2001.

   [RFC4038]  Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E.
              Castro, "Application Aspects of IPv6 Transition",
              RFC 4038, March 2005.

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

   [RFC4864]  Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and
              E. Klein, "Local Network Protection for IPv6", RFC 4864,
              May 2007.

   [RFC4890]  Davies, E. and J. Mohacsi, "Recommendations for Filtering
              ICMPv6 Messages in Firewalls", RFC 4890, May 2007.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, September 2007.

   [RFC5157]  Chown, T., "IPv6 Implications for Network Scanning",
              RFC 5157, March 2008.

   [RFC5375]  Van de Velde, G., Popoviciu, C., Chown, T., Bonness, O.,
              and C. Hahn, "IPv6 Unicast Address Assignment
              Considerations", RFC 5375, December 2008.

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Internet-Draft          IPv6 ICP and ASP Guidance           October 2011

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

   [RFC6180]  Arkko, J. and F. Baker, "Guidelines for Using IPv6
              Transition Mechanisms during IPv6 Deployment", RFC 6180,
              May 2011.

   [RFC6343]  Carpenter, B., "Advisory Guidelines for 6to4 Deployment",
              RFC 6343, August 2011.

Authors' Addresses

   Brian Carpenter
   Department of Computer Science
   University of Auckland
   PB 92019
   Auckland,   1142
   New Zealand

   Email: brian.e.carpenter@gmail.com

   Sheng Jiang
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus
   No.156 Beiqing Road
   Hai-Dian District, Beijing  100095
   P.R. China

   Email: jiangsheng@huawei.com

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