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IPv6 Deployment Status
draft-ietf-v6ops-ipv6-deployment-07

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This is an older version of an Internet-Draft whose latest revision state is "Active".
Authors Giuseppe Fioccola , Paolo Volpato , Nalini Elkins , Jordi Palet Martinez , Gyan Mishra , Chongfeng Xie
Last updated 2022-10-19 (Latest revision 2022-07-29)
Replaces draft-vf-v6ops-ipv6-deployment
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draft-ietf-v6ops-ipv6-deployment-07
V6OPS                                                        G. Fioccola
Internet-Draft                                                P. Volpato
Obsoletes: 6036 (if approved)                        Huawei Technologies
Intended status: Informational                                 N. Elkins
Expires: January 30, 2023                                Inside Products
                                                       J. Palet Martinez
                                                        The IPv6 Company
                                                               G. Mishra
                                                            Verizon Inc.
                                                                  C. Xie
                                                           China Telecom
                                                           July 29, 2022

                         IPv6 Deployment Status
                  draft-ietf-v6ops-ipv6-deployment-07

Abstract

   This document provides an overview of IPv6 deployment status in early
   2022.  Specifically, it looks at the degree of adoption of IPv6 in
   the industry, analyzes the remaining challenges and proposes further
   investigations in areas where the industry has not yet taken a clear
   and unified approach in the transition to IPv6.  It obsoletes RFC
   6036.

Status of This Memo

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

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

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

   This Internet-Draft will expire on January 30, 2023.

Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   5
   2.  IPv6: The Global Picture  . . . . . . . . . . . . . . . . . .   6
     2.1.  IPv4 Address Exhaustion . . . . . . . . . . . . . . . . .   6
       2.1.1.  IPv4 addresses per capita and IPv6 status . . . . . .   7
     2.2.  IPv6 Users  . . . . . . . . . . . . . . . . . . . . . . .   9
     2.3.  IPv6 Web Content  . . . . . . . . . . . . . . . . . . . .  10
     2.4.  IPv6 public actions and policies  . . . . . . . . . . . .  10
   3.  A Survey on IPv6 Deployments  . . . . . . . . . . . . . . . .  11
     3.1.  IPv6 Allocations  . . . . . . . . . . . . . . . . . . . .  11
     3.2.  IPv6 among Internet Service Providers . . . . . . . . . .  13
     3.3.  IPv6 among Enterprises  . . . . . . . . . . . . . . . . .  14
       3.3.1.  Government and Universities . . . . . . . . . . . . .  15
     3.4.  Observations on Industrial Internet . . . . . . . . . . .  17
     3.5.  Observations on Content and Cloud Service Providers . . .  17
     3.6.  Application Transition  . . . . . . . . . . . . . . . . .  18
   4.  IPv6 deployment scenarios . . . . . . . . . . . . . . . . . .  18
     4.1.  Dual-Stack  . . . . . . . . . . . . . . . . . . . . . . .  18
     4.2.  IPv4 as a Service and IPv6-only Overlay . . . . . . . . .  19
     4.3.  IPv6-only Underlay  . . . . . . . . . . . . . . . . . . .  20
     4.4.  IPv6-only . . . . . . . . . . . . . . . . . . . . . . . .  21
   5.  Common IPv6 Challenges  . . . . . . . . . . . . . . . . . . .  21
     5.1.  Transition Choices  . . . . . . . . . . . . . . . . . . .  22
       5.1.1.  Service Providers . . . . . . . . . . . . . . . . . .  22
       5.1.2.  Enterprises and Industrial Internet . . . . . . . . .  23
       5.1.3.  Cloud and Data Centers  . . . . . . . . . . . . . . .  24
       5.1.4.  CEs and user devices  . . . . . . . . . . . . . . . .  24
     5.2.  Network Management and Operations . . . . . . . . . . . .  25
     5.3.  Performance . . . . . . . . . . . . . . . . . . . . . . .  26
       5.3.1.  IPv6 packet loss and latency  . . . . . . . . . . . .  26
       5.3.2.  Customer Experience . . . . . . . . . . . . . . . . .  27
     5.4.  IPv6 security and privacy . . . . . . . . . . . . . . . .  27
       5.4.1.  Protocols security issues . . . . . . . . . . . . . .  28
       5.4.2.  IPv6 Extension Headers and Fragmentation  . . . . . .  29
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  30
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  30

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   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  30
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  30
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  30
     10.2.  Informative References . . . . . . . . . . . . . . . . .  32
   Appendix A.  Summary of Questionnaire and Replies for network
                operators  . . . . . . . . . . . . . . . . . . . . .  40
   Appendix B.  Summary of Questionnaire and Replies for enterprises  42
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  43

1.  Introduction

   [RFC6036] described IPv6 deployment scenarios adopted or foreseen by
   a number of Internet Service Providers (ISPs) who responded to a
   technical questionnaire in early 2010.  In doing that, [RFC6036]
   provided practices and plans expected to take place in the following
   years.  Since the publication of [RFC6036], several other documents
   have contributed to the IPv6 transition discussion in operational
   environments.  To name a few:

      - [RFC6180] discussed IPv6 deployment models and transition
      mechanisms, recommending those proven to be effective in
      operational networks.

      - [RFC6883] provided guidance and suggestions for Internet content
      providers and Application Service Providers (ASPs).

      - [RFC7381] introduced the guidelines of IPv6 deployment for
      enterprises.

   It is worth mentioning here also [RFC6540].  It recommended the
   support of IPv6 to all IP-capable nodes.  It was referenced in the
   IAB Statement on IPv6 [IAB], which represented a major step in
   driving the IETF as well as other Standard Developing Organizations
   (SDOs) towards using IPv6 in their works.

   In more recent times, organizations such as ETSI provided more
   contributions to the use of IPv6 in operational environments,
   targeting IPv6 in different industry segments.  As a result,
   [ETSI-IP6-WhitePaper], was published to provide an updated view on
   the IPv6 best practices adopted so far, in particular in the ISP
   domain.

   Considering all of the above, and after more than ten years since the
   publication of [RFC6036] it may be interesting to revisit where the
   transition of the Internet to IPv6 currently stands, what major steps
   have been accomplished and what is still missing.  Some reasons
   include:

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      - In some areas, the lack of IPv4 addresses forced both carriers
      and content providers to shift to IPv6 to support the introduction
      of new applications, in particular in wireless networks.

      - Some governmental actions took place to encourage or even
      enforce the adoption of IPv6 in certain countries.

      - Looking at the global adoption of IPv6, this seems to have
      reached a threshold that justifies speaking of native, end-to-end
      IPv6 connectivity at the IPv6 service layer.

   This document intends to provide a survey of the status of IPv6
   deployment and highlight both the achievements and remaining
   obstacles in the transition to IPv6 networks (and its coexistence
   with continued IPv4 services).  The target is to give an updated view
   of the practices and plans already described in [RFC6036], to
   encourage further actions and more investigations in those areas that
   are still under discussion, and to present the main incentives for
   the adoption of IPv6.  The expectation is that this process may help
   to understand what is missing and how to improve the current IPv6
   deployment strategies of internet service providers, enterprises,
   content and cloud service providers.

   The initial section of this document reports some data about the
   status of IPv6.  The exhaustion of IPv4 as well as the measured
   adoption of IPv6 at the users' and the content's side will be
   discussed.  Comparing both IPv4 and IPv6, IPv6 has a higher growth
   rate all the years.  This testifies the momentum of IPv6.

   The next section provides a survey of IPv6 deployments in different
   environments, including ISPs, enterprises, cloud providers and
   universities.  Data from some well-known analytics will be discussed.
   In addition, two independent polls among network operators and
   enterprises will also be presented.

   Then, a section on IPv6 deployment will describe the IPv6 transition
   approaches for Mobile BroadBand (MBB), Fixed BroadBand (FBB) and
   Enterprise services.  At present, Dual-Stack (DS) is the most
   deployed solution for IPv6 introduction, while 464XLAT and Dual-Stack
   Lite (DS-Lite) seem the preferred ones for those players that have
   already enabled IPv6-only overlay service delivery.

   The last parts of the document will analyze the general challenges to
   be solved in the IPv6 transition.  Specific attention will be given
   to operations, performance and security issues.  It aims to highlight
   some areas that still require improvement and some actions that the
   industry might consider to accelerate adoption of IPv6.

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1.1.  Terminology

   This section defines the terminology regarding the usage of IPv6-only
   expressions within this document.  The term IPv6-only is defined in
   relation to the specific scope it is referring to.  In this regard,
   it may happen that only part of a service, of a network or even part
   of a node is in an IPv6-only scope and the rest is not.  Below are
   listed the most used terms in relation to the different scopes:

      IPv6-only interface: It means that the interface of a node is
      configured to forward only IPv6.  This denotes that just part of
      the node can be IPv6-only since the rest of the interfaces of the
      same node may work with IPv4 as well.  A Dual-Stack interface is
      not an IPv6-only interface.

      IPv6-only node: It means that the node uses only IPv6.  All
      interfaces of the host only have IPv6 addresses.

      IPv6-only service: It is used if between the host's interface and
      the interface of the content server, all packet headers of the
      service session are IPv6.

      IPv6-only overlay: It is used if between the end points of the
      tunnels, all inner packet headers of the tunnels are IPv6.  For
      example, IPv6-only overlay in fixed network means that the
      encapsulation is only IPv6 between the interfaces of the Provider
      Edge (PE) nodes or between the WAN interface of the Customer Edge
      (CE) node and the Broadband Network Gateway (BNG) facing interface
      of CGN.

      IPv6-only underlay: It is used if the data plane and control plane
      are IPv6, but not necessarily management plane.  For example,
      IPv6-only underlay in fixed network means that the underlay
      network protocol is only IPv6 between any Provider Edge (PE) nodes
      but they can be Dual-Stack in overlay.  SRv6 is an example of
      IPv6-only underlay.

      IPv6-only network: It is used if every node in this network is
      IPv6-only.  No IPv4 should exist in an IPv6-only network.  In
      particular, IPv6-only network's data plane, control plane, and
      management plane must be IPv6.  All PEs must be IPv6-only.
      Therefore, if tunnels exist among PEs, both inner and outer
      headers must be IPv6.  For example, IPv6-only access network means
      that every nodes in this access network must be IPv6-only and
      similarly IPv6-only backbone network means that every nodes in
      this backbone network must be IPv6-only.

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      IPv4 as a Service (IPv4aaS): It means that IPv4 service support is
      provided by means of transition mechanism, therefore there is a
      combination of encapsulation/translation + IPv6-only overlay +
      decapsulation/translation.

   Note that IPv6-only definitions are also discussed in
   [I-D.palet-v6ops-ipv6-only].

2.  IPv6: The Global Picture

   This section deals with some key questions related to IPv6 namely:
   (1) the status of IPv4 exhaustion, often considered as one of the
   triggers to switch to IPv6, (2) the number of IPv6 end users, a
   primary measure to sense IPv6 adoption, (3) the percentage of
   websites reachable over IPv6 and (4) a report on IPv6 public actions
   and policies.

   These parameters are monitored by the Regional internet Registries
   (RIRs) and other institutions worldwide as they provide a first-order
   indication on the adoption of IPv6.

2.1.  IPv4 Address Exhaustion

   According to [CAIR] there will be 29.3 billion networked devices by
   2023, up from 18.4 billion in 2018.  This poses the question on
   whether the IPv4 address space can sustain such a number of
   allocations and, consequently, if this may affect the process of its
   exhaustion.  The answer is not straightforward as many aspects have
   to be considered.

   On one hand, the RIRs are reporting scarcity of available and still
   reserved addresses.  Table 3 of [POTAROO1] shows that the available
   pool of the five RIRs counts 5.2 million IPv4 addresses, while the
   reserved pool includes another 12 million, for a total of "usable"
   addresses equal to 17.3 million (-5.5% year over year, comparing 2021
   against 2020).  The same reference, in table 1, shows that the total
   IPv4 allocated pool equals to 3.685 billion addresses (+0.027% year
   over year).  The ratio between the "usable" addresses and the total
   allocated brings to 0.469% of remaining space (from 0.474% at the end
   of 2020).

   On the other, [POTAROO1] again highlights the role of both address
   transfer and Network Address Translation (NAT) to counter the IPv4
   exhaustion.  The transfer of IPv4 addresses can be done under the
   control or registration of a RIR or on the so-called grey market
   where third parties operate to enable the buy/sell of IPv4 addresses.
   In all cases, a set of IPv4 addresses is "transferred" to a different
   holder that has the need to expand their address range.  As an

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   example, [IGP-GT] and [NRO] show the amount of transfers to recipient
   organizations in the different regions.  Cloud Service Providers
   (CSPs) appear to be the most active in buying IPv4 addresses to
   satisfy their need of providing IPv4 connectivity to their tenants.
   NAT systems provide a means to absorb at least a portion of the
   demand of public IPv4 addresses as they enable the use of private
   addressing in internal networks while limiting the use of public
   addresses on their WAN-facing side.  Their actions cannot be
   objected, but it has to be noted that architectural and operational
   issues remain, especially in the case of NAT.  Private address space
   cannot provide adequate address span, especially for large
   organizations, and the reuse of addresses may make the network more
   complex.  In addition, multiple levels of address translation may
   coexist in a network, e.g.  Carrier-Grade NAT [RFC6264] based on two
   stages of translation.  This comes with an economic and operational
   burden, as discussed later in this document.

2.1.1.  IPv4 addresses per capita and IPv6 status

   The IPv4 addresses per capita ratio measures the quantity of IPv4
   addresses allocated to a given country divided by the population of
   that country.  It is a theoretical ratio, anyhow it provides an
   indication of the imbalanced distribution of the IPv4 addresses
   worldwide.  It clearly derives from the allocation of addresses made
   in the early days of the Internet by the most advanced countries.

   The sources for measuring the IPv4 addresses per capita ratio are the
   allocations done by the RIRs and the statistics about the world
   population.  In this regard, [POTAROO2] provides distribution files.
   The next table compares the IPv4 addresses per capita ratio of a
   certain country with relative adoption of IPv6, expressed as the
   number of IPv6 capable users in the considered country.  The table is
   ordered based on the IPv4 addresses per capita ratio.

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   +------------------------+-----------------+-----------------+
   |Country                 |  IPv4 per capita|  IPv6 deployment|
   +------------------------+-----------------+-----------------+
   |United States of America|             4.89|            47.1%|
   +------------------------+-----------------+-----------------+
   |Sweden                  |             2.97|            11.8%|
   +------------------------+-----------------+-----------------+
   |Netherlands             |             2.93|            35.5%|
   +------------------------+-----------------+-----------------+
   |Switzerland             |             2.75|            34.9%|
   +------------------------+-----------------+-----------------+
   |Republic of Korea       |             2.19|            17.1%|
   +------------------------+-----------------+-----------------+
   |Australia               |             1.91|            28.8%|
   +------------------------+-----------------+-----------------+
   |Canada                  |             1.85|            32.4%|
   +------------------------+-----------------+-----------------+
   |United Kingdom          |             1.65|            33.2%|
   +------------------------+-----------------+-----------------+
   |Belgium                 |             1.62|            62.0%|
   +------------------------+-----------------+-----------------+
   |Japan                   |             1.50|            36.7%|
   +------------------------+-----------------+-----------------+
   |Germany                 |             1.48|            53.0%|
   +------------------------+-----------------+-----------------+
   |France                  |             1.27|            42.1%|
   +------------------------+-----------------+-----------------+
   |Austria                 |             1.24|            29.2%|
   +------------------------+-----------------+-----------------+
   |Italy                   |             0.91|             4.7%|
   +------------------------+-----------------+-----------------+
   |Spain                   |             0.69|             3.0%|
   +------------------------+-----------------+-----------------+
   |Poland                  |             0.55|            14.7%|
   +------------------------+-----------------+-----------------+
   |Brazil                  |             0.41|            38.7%|
   +------------------------+-----------------+-----------------+
   |Russian Federation      |             0.31|             9.7%|
   +------------------------+-----------------+-----------------+
   |China (*)               |             0.24|            60.1%|
   +------------------------+-----------------+-----------------+
   |India                   |             0.03|            76.9%|
   +------------------------+-----------------+-----------------+

               Figure 1: IPv4 per capita and IPv6 deployment

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   (*) The IPv6 deployment information in China is derived from
   [CN-IPv6].

   It is clear that there is no direct correlation between low IPv4 per
   capita and high IPv6 adoption.  For example, countries like the
   Russian Federation, Poland, Spain and Italy have lower IPv4 per
   capita ratio than countries like the U.S.A, Germany, France, even if
   their IPv6 adoption rate is also lower.  Looking at the countries
   with higher IPv6 adoption, this appears related to several factors in
   addition to the lack of IPv4 addresses, including local regulation
   and market-driven actions.

2.2.  IPv6 Users

   The count of the IPv6 users is the key parameter to get an immediate
   understanding of the adoption of IPv6.  Some organizations constantly
   track the usage of IPv6 by aggregating data from several sources.  As
   an example, the Internet Society constantly monitors the volume of
   IPv6 traffic for the networks that joined the WorldIPv6Launch
   initiative [WIPv6L].  The measurement aggregates statistics from
   organizations such as [Akm-stats] that provides data down to the
   single network level measuring the number of hits to their content
   delivery platform.  For the scope of this document, we follow the
   approach used by APNIC to quantify the adoption of IPv6 by means of a
   script that runs on a user's device [CAIDA].  To give a rough
   estimation of the relative growth of IPv6, the next table aggregates
   the total number of estimated IPv6-capable users at January 2022, and
   compares it against the total Internet users, as measured by
   [POTAROO2].

   +--------+--------+--------+--------+--------+--------+--------+
   |        |  Jan   |  Jan   |  Jan   |  Jan   |  Jan   |  CAGR  |
   |        |  2018  |  2019  |  2020  |  2021  |  2022  |        |
   +--------+--------+--------+--------+--------+--------+--------+
   |  IPv6  |  513.07|  574.02|  989.25|1,136.28|1,207.61|  23.9% |
   +--------+--------+--------+--------+--------+--------+--------+
   | World  |3,410.27|3,470.36|4,065.00|4,091.62|4,093.69|   4.7% |
   +--------+--------+--------+--------+--------+--------+--------+
   | Ratio  |   15.0%|   16.5%|   24.3%|   27.8%|   29.5%|  18.4% |
   +--------+--------+--------+--------+--------+--------+--------+

         Figure 2: IPv6-capable users against total (in millions)

   Two figures appear: first, the IPv6 Internet population is growing
   with a two-digits Compound Annual Growth Rate (CAGR), and second, the
   ratio IPv6 over total is also growing steadily.

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2.3.  IPv6 Web Content

   [W3Tech] keeps track of the use of several technical components of
   websites.  The utilization of IPv6 for websites is shown in the next
   table.

   +------------+-------+-------+-------+-------+-------+------+
   |  Wolrdwide |  Jan  |  Jan  |  Jan  |  Jan  |  Jan  | CAGR |
   |  Websites  |  2018 |  2019 |  2020 |  2021 |  2022 |      |
   +------------+-------+-------+-------+-------+-------+------+
   |% of IPv6   | 11.4% | 13.3% | 15.0% | 17.5% | 20.6% | 15.9%|
   +------------+-------+-------+-------+-------+-------+------+

                    Figure 3: Usage of IPv6 in websites

   Looking at the growth rate, it may appear not particularly high.  It
   has to be noted, though, that not all websites are equal.  The
   largest content providers, which already support IPv6, generate a lot
   more content than small websites.  [Csc6lab] measured at the
   beginning of January 2022 that out of the world top 500 sites ranked
   by [Alx], 203 are IPv6-enabled (+3.6% from January 2021 to January
   2022).  If we consider that the big content providers (such as
   Google, Facebook, Netflix) generate more than 50% of the total mobile
   traffic [SNDVN], and in some cases even more up to 65% ([ISOC1]
   [HxBld]), the percentage of content accessible over IPv6 is clearly
   more relevant than the number of enabled IPv6 websites.

   Related to that, a question that sometimes arises is whether the
   content stored by content providers would be all accessible on IPv6
   in the hypothetical case of a sudden IPv4 switch-off.  Even if this
   is pure speculation, the numbers above may bring to state that this
   is likely the case.  This would reinforce the common thought that, in
   quantitative terms, most of content is accessible via IPv6.

2.4.  IPv6 public actions and policies

   As previously noted, the worldwide deployment of IPv6 is not uniform
   [G_stats], [APNIC1].  It is worth noticing that, in some cases,
   higher IPv6 adoption in a certain country has been achieved as a
   consequence of actions taken by the local government through
   regulation or incentive to the market.  Looking at the European Union
   area, countries such as Belgium, France and Germany are well ahead in
   terms of IPv6 adoption.  In the case of Belgium, the Belgian
   Institute for Postal services and Telecommunications (BIPT) acted to
   mediate an agreement between the local ISPs and the government to
   limit the use of CGN systems and of public IPv4 addresses for lawful
   investigations in 2012 [BIPT].  The agreement limited the use of one

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   IPv4 address per 16 customers behind NAT.  The economic burden
   sustained by the ISPs for the unoptimized use of NAT induced the
   shift to IPv6 and its increased adoption in the latest years.  In
   France, the National Regulator (Autorite de regulation des
   communications electroniques, or Arcep) introduced an obligation for
   the mobile carriers awarded with a license to use 5G frequencies
   (3.4-3.8GHz) in Metropolitan France to be IPv6 compatible [ARCEP].
   As stated, "the goal is to ensure that services are interoperable and
   to remove obstacles to using services that are only available in
   IPv6, as the number of devices in use continues to soar, and because
   the RIPE NCC has run out of IPv4 addresses".  A slow adoption of IPv6
   could prevent new Internet services to widespread or create a barrier
   to entry for newcomers to the market.  "IPv6 can help to increase
   competition in the telecom industry, and help to industrialize a
   country for specific vertical sectors".  Increased IPv6 adoption in
   Germany depended on a mix of industry and public actions.
   Specifically, the Federal Office for Information Technology (under
   the Federal Ministry of the Interior) issued over the years a few
   recommendations on the use of IPv6 in the German public
   administration.  The latest guideline in 2019 constitutes a high-
   level roadmap for mandatory IPv6 introduction in the federal
   administration networks [GFA].  In the United States, the Office of
   Management and Budget is also calling for IPv6 adoption [US-FR],
   [US-CIO].  These documents define a plan to have the 80% of the US
   Federal IP-capable networks based on IPv6-only by the year 2025.
   China is another example of government which is supporting a country-
   wide IPv6 adoption [CN].  In India, the high adoption of IPv6 took
   origin from the decision of Reliance Jio to move to IPv6 in their
   networks [RelJio].  In addition, the Department of Telecommunications
   (under the Ministry of Communications and Information Technology)
   issued guidelines for the progressive adoption of IPv6 in public and
   private networks.  The latest one dates 2021 [IDT] and fosters
   further moves to native IPv6 connection services.

3.  A Survey on IPv6 Deployments

   After discussing the count of the IPv6 users, it is useful to discuss
   the status of IPv6 adoption in operational networks.

3.1.  IPv6 Allocations

   RIRs are responsible for allocating IPv6 address blocks to ISPs, LIRs
   (Local Internet Registries) as well as enterprises or other
   organizations.  An ISP/LIR will use the allocated block to assign
   addresses to their end users.  The following table shows the amount
   of individual allocations, per RIR, in the time period 2017-2021
   [APNIC2].

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   +---------+-------+-------+-------+-------+-------+---------+------+
   | Registry|  Dec  |  Dec  |  Dec  |  Dec  |  Dec  |Cumulated| CAGR |
   |         |  2017 |  2018 |  2019 |  2020 |  2021 |         |      |
   +---------+-------+-------+-------+-------+-------+---------+------+
   | AFRINIC |   112 |   110 |   115 |   109 |   136 |    582  | 51%  |
   |  APNIC  | 1,369 | 1,474 | 1,484 | 1,498 | 1,392 |  7,217  | 52%  |
   |   ARIN  |   684 |   659 |   605 |   644 |   671 |  3,263  | 48%  |
   |  LACNIC | 1,549 | 1,448 | 1,614 | 1,801 |   730 |  7,142  | 47%  |
   | RIPE NCC| 2,051 | 2,620 | 3,104 | 1,403 | 2,542 | 11,720  | 55%  |
   |         |       |       |       |       |       |         |      |
   |  Total  | 5,765 | 6,311 | 6,922 | 5,455 | 5,471 | 29,924  | 51%  |
   +---------+-------+-------+-------+-------+-------+---------+------+

                   Figure 4: IPv6 allocations worldwide

   Overall, the trend is positive, showing the steady progress of IPv6.
   The decline of IPv6 allocations in 2020 and 2021 may be due to
   COVID-19 pandemic.  It also happens to IPv4 allocations.

   [APNIC2] also compares the number of allocations for both address
   families.  The CAGR looks quite similar in 2021 but a little higher
   for the IPv4 allocations in comparison to the IPv6 allocations (53.6%
   versus 50.9%).

   +--------+-------+-------+-------+-------+-------+----------+------+
   | Address|  Dec  |  Dec  |  Dec  |  Dec  |  Dec  | Cumulated| CAGR |
   | family |  2017 |  2018 |  2019 |  2020 |  2021 |          |      |
   +--------+-------+-------+-------+-------+-------+----------+------+
   |  IPv6  | 5,765 | 6,311 | 6,922 | 5,455 | 5,471 |   29,924 | 50.9%|
   |        |       |       |       |       |       |          |      |
   |  IPv4  | 8,091 | 9,707 |13,112 | 6,263 | 7,829 |   45,002 | 53.6%|
   |        |       |       |       |       |       |          |      |
   +--------+-------+-------+-------+-------+-------+----------+------+

                 Figure 5: Allocations per address family

   The reason may be that the IPv4 allocations in 2021 include many
   allocations of small address ranges (e.g. /24) [APNIC2].  On the
   contrary, a single IPv6 allocation is large enough to cope with the
   need of an operator for long period.  After an operator receives an
   IPv6 /30 or /32 allocation it is unlikely that a new request of
   addresses is repeated in the short term.  Hence the two CAGR values
   in the table should not be compared directly as the weight of the
   allocations is different.

   The next table is based on [APNIC3], [APNIC4] and shows the
   percentage of Autonomous Systems (AS) supporting IPv6 compared to the

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   total ASes worldwide.  The number of IPv6-capable ASes increased from
   24.3% in January 2018 to 38.7% in January 2022.  This equals to 18%
   CAGR for IPv6-enabled networks.  In comparison, the CAGR for the
   total of IPv6 and IPv4 networks is just 5%.

   +------------+-------+-------+-------+-------+-------+------+
   | Advertised |  Jan  |  Jan  |  Jan  |  Jan  |  Jan  | CAGR |
   |    ASN     |  2018 |  2019 |  2020 |  2021 |  2022 |      |
   +------------+-------+-------+-------+-------+-------+------+
   |IPv6-capable| 14,500| 16,470| 18,650| 21,400| 28,140|  18% |
   |            |       |       |       |       |       |      |
   | Total ASN  | 59,700| 63,100| 66,800| 70,400| 72,800|   5% |
   |            |       |       |       |       |       |      |
   |   Ratio    | 24.3% | 26.1% | 27.9% | 30.4% | 38.7% |      |
   +------------+-------+-------+-------+-------+-------+------+

                 Figure 6: Percentage of IPv6-capable ASes

   The tables above provide an aggregated view of the allocations
   dynamic.  But the aggregated view does not tell us the split between
   the different types of organizations.  The next sections will zoom
   into each specific area to highlight the relative status.

3.2.  IPv6 among Internet Service Providers

   As it was proposed at the time of [RFC6036], also in the case of this
   document a survey was submitted to a group of service providers in
   Europe (see Appendix A for the complete poll), to understand their
   plans about IPv6 and their technical preferences towards its
   adoption.  Although such poll does not give an exhaustive view on the
   IPv6 status, it provides some insights that are relevant to the
   discussion.

   The poll reveals that the majority of the ISPs interviewed has plans
   concerning IPv6 (79%).  Of them, 60% has already ongoing activities,
   while 33% is expected to start activities in a 12-months time-frame.
   The transition to IPv6 involves all business segments: mobile (63%),
   fixed (63%), and enterprises (50%).

   The reasons to move to IPv6 vary.  Global IPv4 address depletion and
   the run out of private address space recommended in [RFC1918] are
   reported as the important drivers for IPv6 deployment (48%).  In a
   few cases, respondents cite the requirement of national IPv6 policies
   and the launch of 5G as the reasons (13%).  Enterprise customers
   demand is also a reason to introduce IPv6 (13%).

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   From a technical preference standpoint, Dual-Stack is the most
   adopted solution, in both wireline (59%) and cellular networks (39%).
   In wireline, the second most adopted mechanism is DS-Lite (19%).  In
   cellular networks, the second preference is 464XLAT (21%).

   More details about the answers received can be found in Appendix A.

3.3.  IPv6 among Enterprises

   As described in [RFC7381], enterprises face different challenges than
   ISPs.  Publicly available reports show how the enterprise deployment
   of IPv6 lags behind ISP deployment [cmpwr].  In this document, an
   enterprise is a company that is not an ISP unless stated otherwise.

   [NST_1] provides estimations on deployment status of IPv6 for 1070
   domains such as example.com, example.net or example.org in the United
   States as of January 2022.  The measurement encompasses many
   industries, including telecommunications, so the term "enterprises"
   is a bit loose in this context.  In any case, it provides a first
   indication of IPv6 adoption in several US industry sectors.  The
   analysis tries to infer whether IPv6 is supported by looking from
   "outside" a company's network.  It takes into consideration the
   support of IPv6 to external services such as Domain Name System
   (DNS), mail and website.  [BGR_1] has similar data for China.  The
   measurement considers 478 second or third level domains such as
   example.cn.  [CNLABS_1] provides the status for 104 measured domains
   in India.

   +--------------+----------+---------+---------+---------+
   |Country       | Domains  |   DNS   |  Mail   | Website |
   |              | analyzed |         |         |         |
   +--------------+----------+---------+---------+---------+
   |China         |    478   |  74.7%  |   0.0%  |   19.7% |
   |              |          |         |         |         |
   +--------------+----------+---------+---------+---------+
   |India         |    104   |  51.9%  |  15.4%  |   16.3% |
   |              |          |         |         |         |
   +--------------+----------+---------+---------+---------+
   |United States |   1070   |  66.8%  |  21.2%  |    6.3% |
   |of America    |          |         |         |         |
   +--------------+----------+---------+---------+---------+

        Figure 7: IPv6 support for external-facing services across
                                enterprises

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   A poll submitted to a group of large enterprises in North America
   (see Appendix B) shows that the operational issues are likely to be
   more critical than for ISPs.

   Looking at current implementations, almost one third has dual-stacked
   networks, while 20% declares that portions of their networks are
   IPv6-only. 35% of the enterprises are stuck at the training phase.
   In no case is the network fully IPv6-based.

   Speaking of training, the most critical needs are in the field of
   IPv6 security and IPv6 troubleshooting (both highlighted by the two
   thirds of respondents), followed by IPv6 fundamentals (57.41%).

   Coming to implementation, the three areas of concern are IPv6
   security (31.48%), training (27.78%), application conversion
   (25.93%).  Interestingly, 33.33% of respondents think that all three
   areas are all simultaneously of concern.

   The full poll is reported in Appendix B.

3.3.1.  Government and Universities

   This section focuses specifically on the IPv6 adoption of governments
   and academia.

   As far as governmental agencies are concerned, [NST_2] provides
   analytics on the degree of IPv6 support for DNS, mail and websites
   across 1283 second level domains associated with the US federal
   agencies.  These domains are in the form of example.gov or
   example.fed.  The script used by [NST_2] has also been employed to
   measure the same analytics in other countries.  For China [BGR_2] 52
   third level domains provide statistics.  For India [CNLABS_2] 618
   domains provide statistics.  [IPv6Forum] analyzes 19 governmental
   domains connected to either the European Union or its member states.

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   +--------------+----------+---------+---------+---------+
   |Country       | Domains  |   DNS   |  Mail   | Website |
   |              | analyzed |         |         |         |
   +--------------+----------+---------+---------+---------+
   |China         |     52   |   0.0%  |   0.0%  |   98.1% |
   |              |          |         |         |         |
   +--------------+----------+---------+---------+---------+
   |European      |     19   |  47.4%  |   0.0%  |   21.1% |
   |Union (*)     |          |         |         |         |
   +--------------+----------+---------+---------+---------+
   |India         |    618   |   7.6%  |   6.5%  |    7.1% |
   |              |          |         |         |         |
   +--------------+----------+---------+---------+---------+
   |United States |   1283   |  87.1%  |  14.0%  |   51.7% |
   |of America    |          |         |         |         |
   +--------------+----------+---------+---------+---------+

        Figure 8: IPv6 support for external-facing services across
                         governmental institutions

   (*) Both EU and European governments domains are considered.

   USA's IPv6 support is higher than other countries.  This is likely
   due to the IPv6 mandate set by [US-CIO].  In the case of India, the
   degree of support seems still quite low.  This is also true for
   China, with the notable exception of high percentage of IPv6-enabled
   websites for government-related organizations.

   Similar statistics are also available for higher education.  [NST_3]
   measures the data from 346 second level domains of universities in
   the US, such as example.edu.  [BGR_3] looks at 111 Chinese education-
   related domains.  [CNLABS_3] analyzes 100 domains in India (mostly
   third level), while [IPv6Forum] lists 118 universities in the
   European Union (second level).

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   +--------------+----------+---------+---------+---------+
   |Country       | Domains  |   DNS   |  Mail   | Website |
   |              | analyzed |         |         |         |
   +--------------+----------+---------+---------+---------+
   |China         |    111   |  36.9%  |   0.0%  |   77.5% |
   |              |          |         |         |         |
   +--------------+----------+---------+---------+---------+
   |European      |    118   |  83.9%  |  43.2%  |   35.6% |
   |Union         |          |         |         |         |
   +--------------+----------+---------+---------+---------+
   |India         |    100   |  31.0%  |  54.0%  |    5.0% |
   |              |          |         |         |         |
   +--------------+----------+---------+---------+---------+
   |United States |    346   |  49.1%  |  19.4%  |   21.7% |
   |of America    |          |         |         |         |
   +--------------+----------+---------+---------+---------+

        Figure 9: IPv6 support for external-facing services across
                               universities

   Overall, the universities have wider support of IPv6-based services
   compared to the other sectors.  Apart from a couple of exceptions
   (e.g. the support of IPv6 mail in China and IPv6 web sites in India),
   the numbers shown in the table above indicate a good support of IPv6
   in academia.

3.4.  Observations on Industrial Internet

   There are potential advantages for using IPv6 for Industrial Internet
   of Things (IIoT), in particular the large IPv6 address space, the
   automatic IPv6 address configuration and resource discovery.

   However, there are still many obstacles that prevent its pervasive
   use.  The key problems identified are the incomplete or immature tool
   support, the dependency on manual configuration and the poor
   knowledge of the IPv6 protocols.  To promote the use of IPv6 for
   smart manufacturing systems and IIoT applications a generic approach
   to remove these pain points is highly desirable.

3.5.  Observations on Content and Cloud Service Providers

   The high number of addresses required to connect the virtual and
   physical elements in a Data Center and the necessity to overcome the
   limitation posed by [RFC1918] have been the drivers to the adoption
   of IPv6 in several CSP networks.

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   Several public references, as reported in Section 5.1.3, discuss how
   most of the major players find themselves at different stages in the
   transition to IPv6-only in their Data Center (DC) infrastructure.  In
   some cases, the transition already happened and the DC infrastructure
   of these hyperscalers is completely based on IPv6.

3.6.  Application Transition

   The transition to IPv6 requires that the application software is
   adapted for use in IPv6-based networks ([ARIN-SW] provides an
   example).  The use of transition mechanisms like 464XLAT is essential
   to support IPv4-only applications while they evolve to IPv6.
   Depending on the transition mechanism employed some issues may
   remain.  For example, in the case of NAT64/DNS64 the use of literal
   IPv4 addresses, instead of DNS names, will fail, unless mechanisms
   such as Application Level Gateways (ALG) are used.  This issue is not
   present in 464XLAT (see [RFC8683]).

   It is worth mentioning Happy Eyeballs [RFC8305] as a relevant aspect
   of application transition to IPv6.

4.  IPv6 deployment scenarios

   The scope of this section is to discuss the network and service
   scenarios applicable for the transition to IPv6.  Most of their
   definitions have been provided in Section 1.1.  This clause is
   intended to focus on their technical and operational characteristics.
   It is worth noticing that the sequence of scenarios described here
   does not have necessarily to be intended as a roadmap for the IPv6
   transition.  Depending on their specific plans and requirements,
   service providers may either adopt the scenarios proposed in a
   sequence or jump directly to a specific one.

4.1.  Dual-Stack

   Based on answers provided by operators to the poll (Appendix A),
   Dual-Stack [RFC4213] appears to be currently the most widely deployed
   IPv6 solution (about 50%, see both Appendix A and the statistics
   reported in [ETSI-IP6-WhitePaper]).

   With Dual-Stack, IPv6 can be introduced together with other network
   upgrades and many parts of network management and Information
   Technology (IT) systems can still work in IPv4.  This avoids major
   upgrade of such systems to support IPv6, which is possibly the most
   difficult task in the IPv6 transition.  The cost and effort on the
   network management and IT systems upgrade are moderate.  The benefits
   are to start using IPv6 and save NAT costs.

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   Although Dual-Stack may provide advantages in the introductory stage,
   it does have a few disadvantages in the long run, like the
   duplication of the network resources and states.  It also requires
   more IPv4 addresses, thus increasing both Capital Expenses (CAPEX)
   and Operating Expenses (OPEX).  For example, even if private
   addresses are used with Carrier-Grade NAT (CGN), there is extra
   investment in the CGN devices, logs storage and helpdesk to track
   CGN-related issues.

   For this reason, when IPv6 usage exceeds certain threshold, it may be
   advantageous to switch to start a transition to a next scenario.  For
   example, the process may start with the IPv6-only overlay stage and
   IPv4aaS, as described hereinafter.  It is difficult to establish the
   criterion for switching (e.g. to properly identify the upper bound of
   the IPv4 decrease or the lower bound of the IPv6 increase).  In
   addition to the technical factors, the switch to the next scenarios
   may also cause a loss of customers.  Based on feedbacks of network
   operators participating in World IPv6 Launch [WIPv6L] in June 2021,
   108 out of 346 operators exceed 50% of IPv6 traffic volume (31.2%),
   72 exceed 60% (20.8%), while 37 exceed 75% (10.7%).  The consensus to
   move to IPv6-only might be reasonable when IPv6 traffic volume is
   between 50% and 60%.

4.2.  IPv4 as a Service and IPv6-only Overlay

   As defined in Section 1.1, IPv6-only is generally associated with a
   scope, e.g.  IPv6-only overlay or IPv6-only underlay.

   The IPv6-only overlay denotes that the overlay tunnel between the end
   points of a network is based only on IPv6.  It can be used to ensure
   IPv4 support via IPv4aaS and it can be a complex decision that
   depends on several factors, such as economic aspects, policy and
   government regulation.

   [I-D.ietf-v6ops-transition-comparison] compares the merits of the
   most common transition solutions for IPv6-only service delivery, i.e.
   464XLAT [RFC6877], DS-lite [RFC6333], Lightweight 4over6 (lw4o6)
   [RFC7596], MAP-E [RFC7597], and MAP-T [RFC7599], but does not provide
   an explicit recommendation.  However, the poll in Appendix A
   indicates that the most widely deployed IPv6 transition solution in
   the MBB domain is 464XLAT while in the FBB domain is DS-Lite.

   Both are IPv4aaS solutions by leveraging IPv6-only overlay.  IPv4aaS
   offers Dual-Stack service to users and allows an ISP to run IPv6-only
   in the network (typically, the access network).

   While it may not always be the case, IPv6-only transition
   technologies such as 464XLAT require far fewer IPv4 addresses

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   [I-D.ietf-v6ops-transition-comparison], because they make a more
   efficient usage without restricting the number of ports per
   subscriber.  This helps to reduce troubleshooting costs and to remove
   some operational issues related to permanent black-listing of IPv4
   address blocks when used via CGN in some services.

   IPv6-only overlay may be facilitated by the natural upgrade or
   replacement of CEs because of newer technologies (tripe-play, higher
   bandwidth WAN links, better WiFi technologies, etc.).  The CAPEX and
   OPEX of other parts of the network may be lowered (for example CGN
   and associated logs) due to the operational simplification of the
   network.

   For applications with a large number of users (e.g. large mobile
   operators) or a large number of hosts (e.g. large DCs), even the full
   private address space [RFC1918] is not enough.  Also, Dual-Stack will
   likely lead to duplication of network resources and operations to
   support both IPv6 and IPv4, which increases the amount of state
   information in the network.  This suggests that for scenarios such as
   MBB or large DCs, IPv6-only overlay could be more efficient from the
   start of the IPv6 introduction.

   So, in general, when the Dual-Stack disadvantages outweigh the
   IPv6-only complexity, it makes sense to transit to IPv6-only overlay.
   Some network operators already started this process, as in the case
   of [TMus], [RelJio] and [EE].

4.3.  IPv6-only Underlay

   As opposed to IPv6-only overlay and IPv4aaS, discussed in the
   previous sections, IPv6-only underlay network uses IPv6 as the
   network protocol for all traffic delivery.  Both the control and data
   planes are IPv6-based.  The definition of IPv6-only underlay needs to
   be associated with a scope in order to identify the domain where it
   is applicable, such as IPv6-only access network or IPv6-only backbone
   network.

   As a matter of fact, IPv4 reachability must be provided for a long
   time to come over IPv6 for IPv6-only hosts.  Most ISPs are leveraging
   CGN to extend the life of IPv4 instead of going with IPv4aaS.

   When both enterprises and service providers start to transit from an
   IPv4/MPLS backbone to introduce IPv6 in the underlay, they do not
   necessarily need to dual-stack the underlay.  Forwarding plane
   complexity on the Provider (P) nodes of the ISP core should be kept
   simple as a single protocol only backbone.  An example could be
   Softwire Mesh Framework [RFC5565].  This is based on IPv6 as the only

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   protocol for the core network where IPv4 packets can be tunneled with
   4to6 MPLS softwire encapsulation over the IPv6-only backbone.

   Hence, when operators decide to transit to an IPv6 underlay, the ISP
   backbone should be IPv6-only while Dual-Stack is not the best choice.
   The underlay could be IPv6-only and allows IPv4 packets to be
   tunneled using VPN over an IPv6-only backbone and leveraging
   Advertising IPv4 Network Layer Routing Information (NLRI) with an
   IPv6 Next Hop [RFC8950].  Indeed, [RFC8950] specifies the extensions
   necessary to allow advertising IPv4 NLRI, Virtual Private Network
   Unicast (VPN-IPv4) NLRI, Multicast Virtual Private Network (MVPN-
   IPv4) NLRI with a Next Hop address that belongs to the IPv6 protocol.
   And also, [I-D.ietf-bess-ipv6-only-pe-design] allows dual-stacked
   functionality without having to dual-stack the interface and without
   any tunneling mechanisms, resulting in OPEX savings for the
   elimination of IPv4 addressing and BGP peering.  This also enables
   the quick deployment of IPv6 in a core or Data Center network without
   provisioning IPv6 links with global unicast address, that can be a
   long process in very large networks.

   Therefore, IPv6-only underlay network deployment for access and
   backbone network, seems not the first option and the current trend is
   to keep IPv4/MPLS Data Plane and run IPv4/IPv6 Dual-Stack to edge
   nodes.

   As ISPs do the transition in the future to IPv6-only access and
   backbone network, e.g.  Segment Routing over IPv6 data plane (SRv6),
   they are able to start the elimination of IPv4 from the underlay
   transport network while continuing to provide IPv4 services.
   Basically, as also showed by the poll among network operators, from a
   network architecture perspective, it is not recommended to apply
   Dual-Stack to the transport network per reasons mentioned above
   related to the forwarding plane complexities.

4.4.  IPv6-only

   IPv6-only is the final stage of the IPv6 transition and it happens
   when a complete network, end-to-end, no longer has IPv4.  No IPv4
   address is configured for network management or anything.

   Since IPv6-only means that both underlay network and overlay services
   are only IPv6, it will take longer to happen.

5.  Common IPv6 Challenges

   This section lists common IPv6 challenges in order to encourage more
   investigations.  Despite IPv6 has already been well-proven in
   production, there are some challenges to consider.  In this regard,

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   it is worth noting that [ETSI-GR-IPE-001] also discusses gaps that
   still exist in IPv6 related use cases.

5.1.  Transition Choices

   A service provider or an enterprise may perceive quite a complex task
   the transition to IPv6, due to the many technical alternatives
   available and the changes required in management and operations.
   Moreover, the choice of the method to support the transition may
   depend on factors specific to the operator's or the enterprise's
   context, such as the IPv6 network design that fits the service
   requirements, the network operations and the deployment strategy.

   This section briefly highlights the approaches that service providers
   and enterprises may take and the related challenges.

5.1.1.  Service Providers

   For fixed operators, the massive software upgrade of CEs to support
   Dual-Stack already started in most of service provider networks.  On
   average, looking at the global statistics, the IPv6 traffic
   percentage is currently around 40%.  As highlighted earlier, all
   major content providers have already implemented Dual-Stack access to
   their services and most of them have implemented IPv6-only in their
   Data Centers.  This aspect could affect the decision on the IPv6
   adoption for an operator, but there are also other factors like the
   current IPv4 address shortage, CE costs, CGN costs and so on.

      Fixed Operators with a Dual-Stack architecture, can start defining
      and apply a new strategy when reaching the limit in terms of
      number of IPv4 addresses available.  This may be done through CGN
      or with an IPv4aaS approach.

      Most of the fixed operators remain attached to a Dual-Stack
      architecture and have already employed CGN.  In this case it is
      likely that CGN boosts their ability to supply IPv4 connectivity
      to CEs for more years to come.  Indeed, only few fixed operators
      have chosen to move to an IPv6-only scenario.

   For mobile operators, the situation is quite different since, in some
   cases, mobile operators are already stretching their IPv4 address
   space.  The reason is that CGN translation limits have been reached
   and no more IPv4 public pool addresses are available.

      Some mobile operators choose to implement Dual-Stack as first and
      immediate mitigation solution.

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      Other mobile operators prefer to move to IPv4aaS solutions (e.g.
      464XLAT) since Dual-Stack only mitigates and does not solve
      completely the IPv4 address scarcity issue.

   For both fixed and mobile operators the approach for the transition
   is not unique and this bring different challenges in relation to the
   network architecture and related costs.  So each operator needs to do
   own evaluations for the transition based on the specific situation.

5.1.2.  Enterprises and Industrial Internet

   At present, the challenge for enterprises mainly relies on upstream
   service providers.  Often, the enterprise connectivity depends on the
   services provided by their upstream provider.  As pointed out in
   Section 3, enterprises may benefit deploying IPv6 in their public-
   facing services.  IPv6 also shows its advantages in the case of
   merger and acquisition, to avoid overlapping of the two address
   spaces.  In addition, since several governments are introducing IPv6
   policy, all the enterprises providing consulting service to
   governments are also required to support IPv6.

   Enterprises are shielded from IPv4 address depletion issues due to
   their predominantly use of Proxy and private addressing [RFC1918],
   thus do not have the business requirement or technical justification
   to transit to IPv6.  Enterprises need to find a business case and a
   strong motivation for IPv6 transition to justify additional CAPEX and
   OPEX.  Also, since Information and Communication Technologies (ICT)
   is not the core business for most of the enterprises, ICT budget is
   often constrained and cannot expand considerably.  However, there are
   examples of big enterprises that are considering IPv6 to achieve
   business targets through a more efficient IPv6 network and to
   introduce newer services which require IPv6 network architecture.

   Enterprises worldwide, in particular small and medium-sized, are
   quite late to adopt IPv6, especially on internal networks.  In most
   cases, the enterprise engineers and technicians do not know well how
   IPv6 works and the problem of application porting to IPv6 looks quite
   difficult, even if technically is not a big issue.  As highlighted in
   the relevant poll, the technicians may want to get trained but the
   management do not see a business need for adoption.  This creates an
   unfortunate cycle where misinformation about the complexity of the
   IPv6 protocol and unreasonable fears about security and manageability
   combine with the perceived lack of urgent business needs to prevent
   adoption of IPv6.  In 2019 and 2020, there has been a concerted
   effort by some ARIN and APNIC initiatives to provide training
   [ARIN-CG] [ISIF-ASIA-G].

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   As the most promising protocol for network evolution, IPv6 is
   frequently mentioned in relation to Internet of Things and Industry
   4.0.  However, its industrial adoption, in particular in smart
   manufacturing systems, has been much slower than expected.  Indeed,
   as for enterprises, it is important to provide an easy way to
   familiarize system architects and software developers with the IPv6
   protocol.

   For Industrial Internet and related IIoT applications, it would be
   desirable to be able to implement a truly distributed system without
   dependencies to central components.  In this regard the distributed
   IIoT applications can leverage the configuration-less characteristic
   of IPv6.  In addition, it could be interesting to have the ability to
   use IP based communication and standard application protocols at
   every point in the production process and further reduce the use of
   specialized communication systems.

5.1.3.  Cloud and Data Centers

   Most CSPs have adopted IPv6 in their internal infrastructure but are
   also active in gathering IPv4 addresses on the transfer market to
   serve the current business needs of IPv4 connectivity.  As noted in
   the previous section, most enterprises do not consider the transition
   to IPv6 as a priority.  To this extent, the use of IPv4-based network
   services by the CSPs will last.  Indeed, CSPs are struggling to buy
   IPv4 addresses.

   It is interesting to look at how much traffic in a network is going
   to Caches and Content Delivery Networks (CDNs).  The response is
   expected to be an high percentage, at least higher than 50% in most
   of the cases.  Since all the key Caches and CDNs are IPv6-ready
   [Cldflr], [Akm], [Ggl], [Ntflx], [Amzn], [Mcrsft], [Vrzn].  So the
   percentage of traffic going to the key Caches/CDNs is a good
   approximation of the potential IPv6 traffic in a network.

   The challenge for CSPs is related to the support of non-native IPv4
   since most CSPs provide native IPv6.  If, in the next years, the
   scarcity of IPv4 addresses becomes more evident, it is likely that
   the cost of buying an IPv4 address by a CSP could be charged to their
   customers.

5.1.4.  CEs and user devices

   It can be noted that most of the user devices (e.g. smartphones) are
   already IPv6-enabled since so many years.  But there are exceptions,
   for example, smartTVs and Set-Top Box (STBs) typically had IPv6
   support since few years ago, however not all the economies replace
   them at the same pace.

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   As already mentioned, ISPs who historically provided public IPv4
   addresses to their customers generally still have those IPv4
   addresses (unless they chose to transfer them).  Some have chosen to
   put new customers on CGN but without touching existing customers.
   Because of the extremely small number of customers who notice that
   IPv4 is done via NAT444, it could be less likely to run out of IPv4
   addresses and private IPv4 space.  But as IPv4-only devices and
   traffic reduce, then the need to support private and public IPv4
   become less.  So the complete support of CEs to IPv6 is also an
   important challenge and incentive to overcome Dual-Stack towards
   IPv4aaS solution [ANSI].

5.2.  Network Management and Operations

   There are important IPv6 complementary solutions related to
   Operations, Administration and Maintenance (OAM) that look not so
   complete compared to IPv4.  Network Management System (NMS) has a
   central role in the modern networks for both network operators and
   enterprises and its transition is a fundamental challenge.  This is
   because some IPv6 products are not field-proven as for IPv4 even if
   traditional protocols (e.g.  SNMP, RADIUS) already support IPv6.  In
   addition, incompatible vendor roadmap for the development of new NMS
   features affects the confidence of network operators or enterprises.
   For example, YANG is the configuration language for networking but in
   the real world the data modeling is still vendor dependent.

   An important factor is represented by the need for training the
   network operations workforce.  Deploying IPv6 requires it as policies
   and procedures have to be adjusted in order to successfully plan and
   complete an IPv6 transition.  Staff has to be aware of the best
   practices for managing IPv4 and IPv6 assets.  In addition to network
   nodes, network management applications and equipment need to be
   properly configured and in some cases also replaced.  This may
   introduce more complexity and costs for the transition.

   Availability of both systems and training is necessary in areas such
   as IPv6 addressing.  IPv6 addresses can be assigned to an interface
   through different means, such as Stateless Auto-Configuration (SLAAC)
   [RFC4862], stateful and stateless Dynamic Host Control Protocol
   (DHCP) [RFC8415].  IP Address Management (IPAM) systems may
   contribute to handle the technical differences and automate some of
   the configuration tasks, such as the address assignment or the
   management of DHCP services.

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5.3.  Performance

   People tend to compare the performance of IPv6 versus IPv4 to argue
   or motivate the IPv6 transition.  In some cases, IPv6 behaving
   "worse" than IPv4 may be used as an argument for avoiding the full
   adoption of IPv6.  However, there are some aspects where IPv6 is
   filling the gap to IPv4.  This position is supported when looking at
   available analytics on two critical parameters: packet loss and
   latency.  These parameters have been constantly monitored over time,
   but only a few extensive researches and measurement campaigns are
   currently providing up-to-date information.  While performance is
   undoubtedly an important issue to consider and worth further
   investigation, reality is that a definitive answer cannot be found on
   what IP version performs better.  Depending on the specific use case
   and application, IPv6 is better; in others the same applies to IPv4.

5.3.1.  IPv6 packet loss and latency

   [APNIC5] provides a measurement of both the failure rate and RTT of
   IPv6 compared against IPv4.  Both measures are based on scripts that
   employs the three-way handshake of TCP.  As such, the measurement of
   the failure rate does not provide a direct measurement of packet loss
   (that would need an Internet-wide measurement campaign).  Said that,
   despite IPv4 is still performing better, the difference seems to have
   decreased in recent years.  Two reports, namely [RIPE1] and
   [APRICOT], discussed the associated trend, showing how the average
   worldwide failure rate of IPv6 is still a bit worse than IPv4.
   Reasons for this effect may be found in endpoints with an unreachable
   IPv6 address, routing instability or firewall behavior.  Yet, this
   worsening effect may appear as disturbing for a plain transition to
   IPv6.

   [APNIC5] also compares the latency of both address families.
   Currently, the worldwide average is still in favor of IPv4.  Zooming
   at the country or even at the operator level, it is possible to get
   more detailed information and appreciate that cases exist where IPv6
   is faster than IPv4.  Regions (e.g.  Western Europe, Northern
   America, Southern Asia) and Countries (e.g.  US, India, Germany) with
   an advanced deployment of IPv6 (e.g. >45%) are showing that IPv6 has
   better performance than IPv4.  [APRICOT] highlights how when a
   difference in performance exists it is often related to asymmetric
   routing issues.  Other possible explanations for a relative latency
   difference lays on the specificity of the IPv6 header which allows
   packet fragmentation.  In turn, this means that hardware needs to
   spend cycles to analyze all of the header sections and when it is not
   capable of handling one of them it drops the packet.  Even
   considering this, a difference in latency stands and sometimes it is
   perceived as a limiting factor for IPv6.  A few measurement campaigns

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   on the behavior of IPv6 in CDNs are also available [MAPRG],
   [INFOCOM].  The TCP connect time is still higher for IPv6 in both
   cases, even if the gap has reduced over the analysis time window.

5.3.2.  Customer Experience

   It is not totally clear if the Customer Experience is in some way
   perceived as better when IPv6 is used instead of IPv4.  In some cases
   it has been publicly reported by IPv6 content providers, that users
   have a better experience when using IPv6-only compared to IPv4
   [ISOC2].  This could be explained because in the case of an IPv6 user
   connecting to an application hosted in an IPv6-only Data Centers, the
   connection is end-to-end, without translations.  Instead, when using
   IPv4 there is a NAT translation either in the CE or in the service
   provider's network, in addition to IPv4 to IPv6 (and back to IPv4)
   translation in the IPv6-only content provider Data Center.  [ISOC2],
   [FB] provide reasons in favor of IPv6.  In other cases, the result
   seems to be still slightly in favor of IPv4 [INFOCOM], [MAPRG], even
   if the difference between IPv4 and IPv6 tends to vanish over time.

5.4.  IPv6 security and privacy

   An important point that is sometimes considered as a challenge when
   discussing the transition to IPv6 is related to the security and
   privacy.  [RFC9099] analyzes the operational security issues in
   several places of a network (enterprises, service providers and
   residential users).  It is also worth considering the additional
   security issues brought by the applied IPv6 transition technologies
   used to implement IPv4aaS, e.g. 464XLAT, DS-Lite.  Some hints are in
   the paper [ComputSecur].

   The security aspects have to be considered to keep at least the same
   or even a better level of security as it exists nowadays in an IPv4
   network environment.  The autoconfiguration features of IPv6 will
   require some more attention.  Router discovery and address
   autoconfiguration may produce unexpected results and security holes.
   IPsec protects IPv6 traffic at least as well as it does IPv4, and the
   security protocols for constrained devices (IoT) are designed for
   IPv6 operation.

   IPv6 was designed to restore the end-to-end model of communications
   with all nodes on networks using globally unique addresses.  But,
   considering this, IPv6 may imply privacy concerns, due to greater
   visibility on the Internet.  IPv6 nodes can (and typically do) use
   privacy extensions [RFC8981] to prevent any tracking of their burned-
   in MAC address(es), which are easily readable in the original
   modified EUI-64 interface identifier format.  But, on the other hand,

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   stable IPv6 interface identifiers ([RFC8064]) were developed and this
   can also affect privacy.

   As reported in [ISOC3], comparing IPv6 and IPv4 at the protocol
   level, one may probably conclude that the increased complexity of
   IPv6 results in an increased number of attack vectors, that imply
   more possible ways to perform different types of attacks.  However, a
   more interesting and practical question is how IPv6 deployments
   compare to IPv4 deployments in terms of security.  In that sense,
   there are a number of aspects to consider.

   Most security vulnerabilities related to network protocols are based
   on implementation flaws.  Typically, security researchers find
   vulnerabilities in protocol implementations, which eventually are
   "patched" to mitigate such vulnerabilities.  Over time, this process
   of finding and patching vulnerabilities results in more robust
   implementations.  For obvious reasons, the IPv4 protocols have
   benefited from the work of security researchers for much longer, and
   thus, IPv4 implementations are generally more robust than IPv6.
   However, with more IPv6 deployment, IPv6 will also benefit from this
   process in the long run.

   Besides the intrinsic properties of the protocols, the security level
   of the resulting deployments is closely related to the level of
   expertise of network and security engineers.  In that sense, there is
   obviously much more experience and confidence with deploying and
   operating IPv4 networks than with deploying and operating IPv6
   networks.

5.4.1.  Protocols security issues

   It is important to say that IPv6 is not more or less secure than IPv4
   and the knowledge of the protocol is the best security measure.

   In general there are security concerns related to IPv6 that can be
   classified as follows:

   o  Basic IPv6 protocol (Basic header, Extension Headers, Addressing)

   o  IPv6 associated protocols (ICMPv6, NDP, MLD, DNS, DHCPv6)

   o  Internet-wide IPv6 security (Filtering, DDoS, Transition
      Mechanisms)

   ICMPv6 is an integral part of IPv6 and performs error reporting and
   diagnostic functions.  Neighbor Discovery Protocol (NDP) is a node
   discovery protocol in IPv6 which replaces and enhances functions of
   ARP.  Multicast Listener Discovery (MLD) is used by IPv6 routers for

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   discovering multicast listeners on a directly attached link, much
   like Internet Group Management Protocol (IGMP) is used in IPv4.

   These IPv6 associated protocols like ICMPv6, NDP and MLD are
   something new compared to IPv4, so they add new security threats and
   the related solutions are still under discussion today.  NDP has
   vulnerabilities [RFC3756] [RFC6583].  The specification says to use
   IPsec but it is impractical and not used, on the other hand, SEND
   (SEcure Neighbour Discovery) [RFC3971] is not widely available.

   [RIPE2] describes the most important threats and solutions regarding
   IPv6 security.

5.4.2.  IPv6 Extension Headers and Fragmentation

   IPv6 Extension Headers provide a hook for interesting new features to
   be added, and are more flexible than IPv4 Options.  This does add
   some complexity, and in particular some security mechanisms may
   require to process the full chain of headers, and some firewalls may
   require to filter packets based on their Extension Headers.
   Additionally, packets with IPv6 Extension Headers may be dropped in
   the public Internet [RFC7872].  Some documents, e.g.
   [I-D.ietf-6man-hbh-processing], [I-D.ietf-v6ops-hbh],
   [I-D.bonica-6man-ext-hdr-update], analyze and provide guidance
   regarding the processing procedures of IPv6 Extension Headers.

   Defence against possible attacks through Extension Headers is
   necessary.  For example, the original IPv6 Routing Header type 0
   (RH0) was deprecated because of possible remote traffic
   amplification.  In addition, it is worth mentioning that unrecognized
   Hop-by-Hop Options Header and Destination Options Header will not be
   considered by the nodes if they are not configured to deal with it
   [RFC8200].  Other attacks based on Extension Headers may be based on
   IPv6 Header Chains and Fragmentation that could be used to bypass
   filtering, but to mitigate this effect, Header chain should go only
   in the first fragment and the use of the IPv6 Fragmentation Header is
   forbidden in all Neighbor Discovery messages [RFC6980].

   Fragment Header is used by IPv6 source node to send a packet bigger
   than path MTU and the Destination host processes fragment headers.
   There are several threats related to fragmentation to pay attention
   to e.g. overlapping fragments (not allowed) resource consumption
   while waiting for last fragment (to discard), atomic fragments (to be
   isolated).

   The operational implications of IPv6 Packets with Extension Headers
   are further discussed in [RFC9098].

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6.  Security Considerations

   This document has no impact on the security properties of specific
   IPv6 protocols or transition tools.  In addition to the discussion
   above in Section 5.4, the security considerations relating to the
   protocols and transition tools are described in the relevant
   documents.

7.  Contributors

   Sebastien Lourdez
   Post Luxembourg
   Email: sebastien.lourdez@post.lu

8.  Acknowledgements

   The authors of this document would like to thank Brian Carpenter,
   Fred Baker, Alexandre Petrescu, Fernando Gont, Barbara Stark,
   Haisheng Yu(Johnson), Dhruv Dhody, Gabor Lencse, Shuping Peng, Daniel
   Voyer, Daniel Bernier, Hariharan Ananthakrishnan, Donavan Fritz, Igor
   Lubashev, Erik Nygren, Eduard Vasilenko and Xipeng Xiao for their
   comments and review of this document.

9.  IANA Considerations

   This document has no actions for IANA.

10.  References

10.1.  Normative References

   [I-D.ietf-v6ops-transition-comparison]
              Lencse, G., Martinez, J. P., Howard, L., Patterson, R.,
              and I. Farrer, "Pros and Cons of IPv6 Transition
              Technologies for IPv4aaS", draft-ietf-v6ops-transition-
              comparison-04 (work in progress), May 2022.

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
              <https://www.rfc-editor.org/info/rfc1918>.

   [RFC3756]  Nikander, P., Ed., Kempf, J., and E. Nordmark, "IPv6
              Neighbor Discovery (ND) Trust Models and Threats",
              RFC 3756, DOI 10.17487/RFC3756, May 2004,
              <https://www.rfc-editor.org/info/rfc3756>.

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   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,
              <https://www.rfc-editor.org/info/rfc3971>.

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

   [RFC6036]  Carpenter, B. and S. Jiang, "Emerging Service Provider
              Scenarios for IPv6 Deployment", RFC 6036,
              DOI 10.17487/RFC6036, October 2010,
              <https://www.rfc-editor.org/info/rfc6036>.

   [RFC6180]  Arkko, J. and F. Baker, "Guidelines for Using IPv6
              Transition Mechanisms during IPv6 Deployment", RFC 6180,
              DOI 10.17487/RFC6180, May 2011,
              <https://www.rfc-editor.org/info/rfc6180>.

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

   [RFC6540]  George, W., Donley, C., Liljenstolpe, C., and L. Howard,
              "IPv6 Support Required for All IP-Capable Nodes", BCP 177,
              RFC 6540, DOI 10.17487/RFC6540, April 2012,
              <https://www.rfc-editor.org/info/rfc6540>.

   [RFC6583]  Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational
              Neighbor Discovery Problems", RFC 6583,
              DOI 10.17487/RFC6583, March 2012,
              <https://www.rfc-editor.org/info/rfc6583>.

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

   [RFC6883]  Carpenter, B. and S. Jiang, "IPv6 Guidance for Internet
              Content Providers and Application Service Providers",
              RFC 6883, DOI 10.17487/RFC6883, March 2013,
              <https://www.rfc-editor.org/info/rfc6883>.

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   [RFC7381]  Chittimaneni, K., Chown, T., Howard, L., Kuarsingh, V.,
              Pouffary, Y., and E. Vyncke, "Enterprise IPv6 Deployment
              Guidelines", RFC 7381, DOI 10.17487/RFC7381, October 2014,
              <https://www.rfc-editor.org/info/rfc7381>.

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

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

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

   [RFC8950]  Litkowski, S., Agrawal, S., Ananthamurthy, K., and K.
              Patel, "Advertising IPv4 Network Layer Reachability
              Information (NLRI) with an IPv6 Next Hop", RFC 8950,
              DOI 10.17487/RFC8950, November 2020,
              <https://www.rfc-editor.org/info/rfc8950>.

   [RFC9099]  Vyncke, E., Chittimaneni, K., Kaeo, M., and E. Rey,
              "Operational Security Considerations for IPv6 Networks",
              RFC 9099, DOI 10.17487/RFC9099, August 2021,
              <https://www.rfc-editor.org/info/rfc9099>.

10.2.  Informative References

   [Akm]      Akamai, "IPv6 Adaptation",
              <https://www.akamai.com/us/en/multimedia/documents/
              product-brief/ipv6-adaptation-product-brief.pdf>.

   [Akm-stats]
              Akamai, "IPv6 Adoption Visualization", 2021,
              <https://www.akamai.com/uk/en/resources/our-thinking/
              state-of-the-internet-report/state-of-the-internet-ipv6-
              adoption-visualization.jsp>.

   [Alx]      Alexa, "The top 500 sites on the web", 2021,
              <https://www.alexa.com/topsites>.

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   [Amzn]     Amazon, "Announcing Internet Protocol Version 6 (IPv6)
              support for Amazon CloudFront, AWS WAF, and Amazon S3
              Transfer Acceleration", <https://aws.amazon.com/es/about-
              aws/whats-new/2016/10/ipv6-support-for-cloudfront-waf-and-
              s3-transfer-acceleration/>.

   [ANSI]     ANSI/CTA, "ANSI/CTA Standard Host and Router Profiles for
              IPv6", 2020, <https://shop.cta.tech/products/host-and-
              router-profiles-for-ipv6>.

   [APNIC1]   APNIC, "IPv6 Capable Rate by country (%)", 2022,
              <https://stats.labs.apnic.net/ipv6>.

   [APNIC2]   APNIC2, "IP Addressing 2021", 2022,
              <https://blog.apnic.net/2022/01/19/ip-addressing-in-
              2021/>.

   [APNIC3]   APNIC, "BGP in 2020 - The BGP Table", 2021,
              <https://blog.apnic.net/2021/01/05/bgp-in-2020-the-bgp-
              table/>>.

   [APNIC4]   APNIC, "BGP in 2021 - The BGP Table", 2022,
              <https://blog.apnic.net/2022/01/06/bgp-in-2021-the-bgp-
              table/>>.

   [APNIC5]   APNIC, "Average RTT Difference (ms) (V6 - V4) for World
              (XA)", 2022, <https://stats.labs.apnic.net/v6perf/XA>.

   [APRICOT]  Huston, G., "Average RTT Difference (ms) (V6 - V4) for
              World (XA)", 2020,
              <https://2020.apricot.net/assets/files/APAE432/ipv6-
              performance-measurement.pdf>.

   [ARCEP]    ARCEP, "Arcep Decision no 2019-1386, Decision on the terms
              and conditions for awarding licences to use frequencies in
              the 3.4-3.8GHz band", 2019,
              <https://www.arcep.fr/uploads/tx_gsavis/19-1386.pdf>.

   [ARIN-CG]  ARIN, "Community Grant Program: IPv6 Security,
              Applications, and Training for Enterprises", 2020,
              <https://www.arin.net/about/community_grants/recipients/>.

   [ARIN-SW]  ARIN, "Preparing Applications for IPv6",
              <https://www.arin.net/resources/guide/ipv6/
              preparing_apps_for_v6.pdf>.

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   [BGR_1]    BIIGROUP, "China Commercial IPv6 and DNSSEC Deployment
              Monitor", 2022,
              <http://218.2.231.237:5001/cgi-bin/generate>.

   [BGR_2]    BIIGROUP, "China Government IPv6 and DNSSEC Deployment
              Monitor", 2022,
              <http://218.2.231.237:5001/cgi-bin/generate_gov>.

   [BGR_3]    BIIGROUP, "China Education IPv6 and DNSSEC Deployment
              Monitor", 2022,
              <http://218.2.231.237:5001/cgi-bin/generate_edu>.

   [BIPT]     Belgian Institute for Postal services and
              Telecommunications, "IPv6 in Belgium", 2017,
              <https://www.ripe.net/participate/meetings/roundtable/
              september-2017/government-roundtable-meeting-bahrain-26-
              september-2017/presentations/belgium-experience-bahrain-
              roundtable.pdf>.

   [CAIDA]    APNIC, "Client-Side IPv6 Measurement", 2020,
              <https://www.cmand.org/workshops/202006-v6/
              slides/2020-06-16-client-side.pdf>.

   [CAIR]     Cisco, "Cisco Annual Internet Report (2018-2023) White
              Paper", 2020,
              <https://www.cisco.com/c/en/us/solutions/collateral/
              executive-perspectives/annual-internet-report/white-paper-
              c11-741490.html>.

   [Cldflr]   Cloudflare, "Understanding and configuring Cloudflare's
              IPv6 support", <https://support.cloudflare.com/hc/en-us/
              articles/229666767-Understanding-and-configuring-
              Cloudflare-s-IPv6-support>.

   [cmpwr]    Compuware, "Impact on Enterprises of the IPv6-Only
              direction for the US Federal Government", 2020,
              <https://mydigitalpublication.com/article/
              Impact+on+Enterprises+of+the+IPv6-Only+Direction+for+the+U
              .S.+Federal+Government/3702828/664279/article.html>.

   [CN]       China.org.cn, "China to speed up IPv6-based Internet
              development", 2017, <http://www.china.org.cn/
              business/2017-11/27/content_41948814.htm>.

   [CN-IPv6]  National IPv6 Deployment and Monitoring Platform, "Active
              IPv6 Internet users", 2022,
              <https://www.china-ipv6.cn/#/activeconnect/simpleInfo>.

Fioccola, et al.        Expires January 30, 2023               [Page 34]
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   [CNLABS_1]
              CNLABS, "Industry IPv6 and DNSSEC Statistics", 2022,
              <https://cnlabs.in/IPv6_Mon/generate_industry.html>.

   [CNLABS_2]
              CNLABS, "Industry IPv6 and DNSSEC Statistics", 2022,
              <https://cnlabs.in/IPv6_Mon/generate_gov.html>.

   [CNLABS_3]
              CNLABS, "Industry IPv6 and DNSSEC Statistics", 2022,
              <https://cnlabs.in/IPv6_Mon/generate_industry.html>.

   [ComputSecur]
              Computers & Security (Elsevier), "Methodology for the
              identification of potential security issues of different
              IPv6 transition technologies: Threat analysis of DNS64 and
              stateful NAT64", DOI 10.1016/j.cose.2018.04.012, 2018.

   [Csc6lab]  Cisco, "World - Display Content Data", 2022,
              <https://6lab.cisco.com/stats/>.

   [EE]       EE, "IPv6-only devices on EE mobile", 2017,
              <https://indico.uknof.org.uk/event/38/contributions/489/
              attachments/612/736/
              Nick_Heatley_EE_IPv6_UKNOF_20170119.pdf>.

   [ETSI-GR-IPE-001]
              ETSI, "ETSI GR IPE 001: IPv6 Enhanced Innovation (IPE) Gap
              Analysis", 2021, <https://www.etsi.org/deliver/etsi_gr/
              IPE/001_099/001/01.01.01_60/gr_IPE001v010101p.pdf>.

   [ETSI-IP6-WhitePaper]
              ETSI, "ETSI White Paper No. 35: IPv6 Best Practices,
              Benefits, Transition Challenges and the Way Forward",
              ISBN 979-10-92620-31-1, 2020.

   [FB]       Saab, P., "Facebook IPv6 Experience", 2015,
              <https://youtu.be/An7s25FSK0U>.

   [G_stats]  Google, "Google IPv6 Per-Country IPv6 adoption", 2021,
              <https://www.google.com/intl/en/ipv6/
              statistics.html#tab=per-country-ipv6-adoption>.

   [GFA]      German Federal Government Commissioner for Information
              Technology, "IPv6-Masterplan fuer die Bundesverwaltung",
              2019, <https://media.frag-den-staat.de/files/foi/531501/
              de-government-ipv6-masterplan-
              v100-entwurf_konvertiert.pdf>.

Fioccola, et al.        Expires January 30, 2023               [Page 35]
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   [Ggl]      Google, "Introduction to GGC",
              <https://support.google.com/interconnect/
              answer/9058809?hl=en>.

   [HxBld]    HexaBuild, "IPv6 Adoption Report 2020", 2020,
              <https://hexabuild.io/assets/files/HexaBuild-IPv6-
              Adoption-Report-2020.pdf>.

   [I-D.bonica-6man-ext-hdr-update]
              Bonica, R. and T. Jinmei, "Inserting, Processing And
              Deleting IPv6 Extension Headers", draft-bonica-6man-ext-
              hdr-update-07 (work in progress), February 2022.

   [I-D.ietf-6man-hbh-processing]
              Hinden, R. M. and G. Fairhurst, "IPv6 Hop-by-Hop Options
              Processing Procedures", draft-ietf-6man-hbh-processing-01
              (work in progress), July 2022.

   [I-D.ietf-bess-ipv6-only-pe-design]
              Mishra, G., Mishra, M., Tantsura, J., Madhavi, S., Yang,
              Q., Simpson, A., and S. Chen, "IPv6-Only PE Design for
              IPv4-NLRI with IPv6-NH", draft-ietf-bess-ipv6-only-pe-
              design-02 (work in progress), March 2022.

   [I-D.ietf-v6ops-hbh]
              Peng, S., Li, Z., Xie, C., Qin, Z., and G. Mishra,
              "Operational Issues with Processing of the Hop-by-Hop
              Options Header", draft-ietf-v6ops-hbh-01 (work in
              progress), April 2022.

   [I-D.palet-v6ops-ipv6-only]
              Martinez, J. P., "IPv6-only Terminology Definition",
              draft-palet-v6ops-ipv6-only-05 (work in progress), March
              2020.

   [IAB]      IAB, "IAB Statement on IPv6", 2016,
              <https://www.iab.org/2016/11/07/iab-statement-on-ipv6/>.

   [IDT]      Indian Department of Telecommunications, "Revision of IPv6
              Transition Timelines", 2021, <https://dot.gov.in/revision-
              ipv6-transition-timelines-2021>.

   [IGP-GT]   Internet Governance Project, Georgia Tech, "The hidden
              standards war: economic factors affecting IPv6
              deployment", 2019, <https://via.hypothes.is/
              https://www.internetgovernance.org/wp-content/uploads/
              IPv6-Migration-Study-final-report.pdf>.

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   [INFOCOM]  Doan, T., "A Longitudinal View of Netflix: Content
              Delivery over IPv6 and Content Cache Deployments", 2020,
              <https://dl.acm.org/doi/abs/10.1109/
              INFOCOM41043.2020.9155367>.

   [IPv6Forum]
              IPv6Forum, "Estimating IPv6 & DNSSEC External Service
              Deployment Status", 2022,
              <https://www.ipv6forum.com/IPv6-Monitoring/index.html>.

   [ISIF-ASIA-G]
              ISIF Asia, "Internet Operations Research Grant: IPv6
              Deployment at Enterprises. IIESoc. India", 2020,
              <https://isif.asia/2020-grantees/>.

   [ISOC1]    Internet Society, "State of IPv6 Deployment 2018", 2018,
              <https://www.internetsociety.org/resources/2018/state-of-
              ipv6-deployment-2018/>.

   [ISOC2]    Internet Society, "Facebook News Feeds Load 20-40% Faster
              Over IPv6", 2015,
              <https://www.internetsociety.org/blog/2015/04/facebook-
              news-feeds-load-20-40-faster-over-ipv6/>.

   [ISOC3]    Internet Society, "IPv6 Security FAQ", 2019,
              <https://www.internetsociety.org/wp-
              content/uploads/2019/02/Deploy360-IPv6-Security-FAQ.pdf>.

   [MAPRG]    Bajpai, V., "Measuring YouTube Content Delivery over
              IPv6", 2017, <https://www.ietf.org/proceedings/99/slides/
              slides-99-maprg-measuring-youtube-content-delivery-over-
              ipv6-00.pdf>.

   [Mcrsft]   Microsoft, "IPv6 for Azure VMs available in most regions",
              <https://azure.microsoft.com/en-us/updates/ipv6-for-azure-
              vms/>.

   [NRO]      NRO, "Internet Number Resource Status Report", 2021,
              <https://www.nro.net/wp-content/uploads/NRO-Statistics-
              2021-Q3-FINAL.pdf>.

   [NST_1]    NIST, "Estimating Industry IPv6 and DNSSEC External
              Service Deployment Status", 2022, <https://fedv6-
              deployment.antd.nist.gov/cgi-bin/generate-com>.

   [NST_2]    NIST, "Estimating USG IPv6 and DNSSEC External Service
              Deployment Status", 2022, <https://fedv6-
              deployment.antd.nist.gov/cgi-bin/generate-gov>.

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   [NST_3]    NIST, "Estimating University IPv6 and DNSSEC External
              Service Deployment Status", 2022, <https://fedv6-
              deployment.antd.nist.gov/cgi-bin/generate-edu>.

   [Ntflx]    Netflix, "Enabling Support for IPv6",
              <https://netflixtechblog.com/enabling-support-for-
              ipv6-48a495d5196f>.

   [POTAROO1]
              POTAROO, "IP Addressing through 2021", 2022,
              <https://www.potaroo.net/ispcol/2022-01/addr2021.html>.

   [POTAROO2]
              POTAROO, "IPv6 Resource Allocations", 2022,
              <https://www.potaroo.net/bgp/iso3166/v6cc.html>.

   [RelJio]   Reliance Jio, "IPv6-only adoption challenges and
              standardization requirements", 2020,
              <https://datatracker.ietf.org/meeting/109/materials/
              slides-109-v6ops-ipv6-only-adoption-challenges-and-
              standardization-requirements-03>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <https://www.rfc-editor.org/info/rfc4862>.

   [RFC5565]  Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
              Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009,
              <https://www.rfc-editor.org/info/rfc5565>.

   [RFC6264]  Jiang, S., Guo, D., and B. Carpenter, "An Incremental
              Carrier-Grade NAT (CGN) for IPv6 Transition", RFC 6264,
              DOI 10.17487/RFC6264, June 2011,
              <https://www.rfc-editor.org/info/rfc6264>.

   [RFC6980]  Gont, F., "Security Implications of IPv6 Fragmentation
              with IPv6 Neighbor Discovery", RFC 6980,
              DOI 10.17487/RFC6980, August 2013,
              <https://www.rfc-editor.org/info/rfc6980>.

   [RFC7872]  Gont, F., Linkova, J., Chown, T., and W. Liu,
              "Observations on the Dropping of Packets with IPv6
              Extension Headers in the Real World", RFC 7872,
              DOI 10.17487/RFC7872, June 2016,
              <https://www.rfc-editor.org/info/rfc7872>.

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   [RFC8064]  Gont, F., Cooper, A., Thaler, D., and W. Liu,
              "Recommendation on Stable IPv6 Interface Identifiers",
              RFC 8064, DOI 10.17487/RFC8064, February 2017,
              <https://www.rfc-editor.org/info/rfc8064>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

   [RFC8305]  Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
              Better Connectivity Using Concurrency", RFC 8305,
              DOI 10.17487/RFC8305, December 2017,
              <https://www.rfc-editor.org/info/rfc8305>.

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/info/rfc8415>.

   [RFC8683]  Palet Martinez, J., "Additional Deployment Guidelines for
              NAT64/464XLAT in Operator and Enterprise Networks",
              RFC 8683, DOI 10.17487/RFC8683, November 2019,
              <https://www.rfc-editor.org/info/rfc8683>.

   [RFC8981]  Gont, F., Krishnan, S., Narten, T., and R. Draves,
              "Temporary Address Extensions for Stateless Address
              Autoconfiguration in IPv6", RFC 8981,
              DOI 10.17487/RFC8981, February 2021,
              <https://www.rfc-editor.org/info/rfc8981>.

   [RFC9098]  Gont, F., Hilliard, N., Doering, G., Kumari, W., Huston,
              G., and W. Liu, "Operational Implications of IPv6 Packets
              with Extension Headers", RFC 9098, DOI 10.17487/RFC9098,
              September 2021, <https://www.rfc-editor.org/info/rfc9098>.

   [RIPE1]    Huston, G., "Measuring IPv6 Performance", 2016,
              <https://ripe73.ripe.net/wp-content/uploads/
              presentations/35-2016-10-24-v6-performance.pdf>.

   [RIPE2]    RIPE, "IPv6 Security", 2019,
              <https://www.ripe.net/support/training/material/ipv6-
              security/ipv6security-slides.pdf>.

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   [SNDVN]    SANDVINE, "Sandvine releases 2020 Mobile Internet
              Phenomena Report: YouTube is over 25% of all mobile
              traffic", 2020, <https://www.sandvine.com/press-releases/
              sandvine-releases-2020-mobile-internet-phenomena-report-
              youtube-is-over-25-of-all-mobile-traffic>.

   [TMus]     T-Mobile US, "Going IPv6-only", 2018,
              <https://pc.nanog.org/static/published/meetings/
              NANOG73/1645/20180625_Lagerholm_T-
              Mobile_S_Journey_To_v1.pdf>.

   [US-CIO]   The CIO Council, "Memorandum for Heads of Executive
              Departments and Agencies. Completing the Transition to
              Internet Protocol Version 6 (IPv6)", 2020,
              <https://www.cio.gov/assets/resources/internet-protocol-
              version6-draft.pdf>.

   [US-FR]    Federal Register, "Request for Comments on Updated
              Guidance for Completing the Transition to the Next
              Generation Internet Protocol, Internet Protocol Version 6
              (IPv6)", 2020, <https://www.federalregister.gov/
              documents/2020/03/02/2020-04202/request-for-comments-on-
              updated-guidance-for-completing-the-transition-to-the-
              next-generation>.

   [Vrzn]     Verizon, "Verizon Digital Media Services announces IPv6
              Compliance", <https://www.verizondigitalmedia.com/blog/
              verizon-digital-media-services-announces-
              ipv6-compliance/>.

   [W3Tech]   W3Tech, "Historical yearly trends in the usage statistics
              of site elements for websites", 2021, <https://w3techs.com
              /technologies/history_overview/site_element/all/y>.

   [WIPv6L]   World IPv6 Launch, "World IPv6 Launch - Measurements",
              2021, <https://www.worldipv6launch.org/measurements/>.

Appendix A.  Summary of Questionnaire and Replies for network operators

   A survey was proposed to more than 50 service providers in the
   European region during the third quarter of 2020 to ask for their
   plans on IPv6 and the status of IPv6 deployment.

   40 people, representing 38 organizations, provided a response.  This
   appendix summarizes the results obtained.

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   Respondents' business
                               Convergent  Mobile  Fixed
       Type of operators       82%         8%      11%

   Question 1.  Do you have plan to move more fixed or mobile or
   enterprise users to IPv6 in the next 2 years?

   a.  If so, fixed, or mobile, or enterprise?

   b.  What are the reasons to do so?

   c.  When to start: already on going, in 12 months, after 12 months?

   d.  Which transition solution will you use, Dual-Stack, DS-Lite,
   464XLAT, MAP-T/E?

   Answer 1.A (38 respondents)

                           Yes     No
       Plans availability  79%     21%

                           Mobile  Fixed   Enterprise  Don't answer
       Business segment    63%     63%     50%         3%

   Answer 1.B (29 respondents)

   Even this was an open question, some common answers can be found.

   14 respondents (48%) highlighted issues related to IPv4 depletion.
   The reason to move to IPv6 is to avoid private and/or overlapping
   addresses.

   For 6 respondents (20%) 5G/IoT is a business incentive to introduce
   IPv6.

   4 respondents (13%) also highlight that there is a National
   regulation request to enable IPv6 associated with the launch of 5G.

   4 respondents (13%) consider IPv6 as a part of their innovation
   strategy or an enabler for new services.

   4 respondents (13%) introduce IPv6 because of Enterprise customers
   demand.

   Answer 1.C (30 respondents)

                   On-going  In 12 months  After 12 months  Don't answer
      Timeframe    60%       33%           0%               7%

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   Answer 1.D (28 respondents for cellular, 27 for wireline)

      Transition in use   Dual-Stack  464XLAT  MAP-T  Don't answer
      Cellular            39%         21%      4%     36%

      Transition in use   Dual-Stack  DS-Lite  6RD/6VPE   Don't answer
      Wireline            59%         19%      4%         19%

   Question 2.  Do you need to change network devices for the above
   goal?

   a.  If yes, what kind of devices: CE, or BNG/mobile core, or NAT?

   b.  Will you start the transition of your metro or backbone or
   backhaul network to support IPv6?

   Answer 2.A (30 respondents)

                          Yes  No   Don't answer
      Need of changing    43%  33%  23%

                          CEs     Routers  BNG  CGN   Mobile core
      What to change      47%     27%      20%  33%   27%

   Answer 2.B (22 respondents)

                            Yes  Future  No
      Plans for transition   9%   9%      82%

Appendix B.  Summary of Questionnaire and Replies for enterprises

   The Industry Network Technology Council (INTC) developed the
   following poll to verify the need or willingness of medium-to-large
   US-based enterprises for training and consultancy on IPv6
   (https://industrynetcouncil.org/).

   54 organizations provided an answer.

   Question 1.  How much IPv6 implementation have you done at your
   organization? (54 respondents)

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      None                                            16.67%
      Some people have gotten some training           16.67%
      Many people have gotten some training            1.85%
      Web site is IPv6 enabled                         7.41%
      Most equipment is dual-stacked                  31.48%
      Have an IPv6 transition plan for entire network  5.56%
      Running native IPv6 in many places              20.37%
      Entire network is IPv6-only                      0.00%

   Question 2.  What kind of help or classes would you like to see INTC
   do? ( 54 respondents)

      Classes/labs on IPv6 security                   66.67%
      Classes/labs on IPv6 fundamentals               55.56%
      Classes/labs on address planning/network conf.  57.41%
      Classes/labs on IPv6 troubleshooting            66.67%
      Classes/labs on application conversion          35.19%
      Other                                           14.81%

   Question 3.  As you begin to think about the implementation of IPv6
   at your organization, what areas do you feel are of concern? (54
   respondents)

      Security                    31.48%
      Application conversion      25.93%
      Training                    27.78%
      All the above               33.33%
      Don't know enough to answer 14.81%
      Other                        9.26%

Authors' Addresses

   Giuseppe Fioccola
   Huawei Technologies
   Riesstrasse, 25
   Munich  80992
   Germany

   Email: giuseppe.fioccola@huawei.com

   Paolo Volpato
   Huawei Technologies
   Via Lorenteggio, 240
   Milan  20147
   Italy

   Email: paolo.volpato@huawei.com

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   Nalini Elkins
   Inside Products
   36A Upper Circle
   Carmel Valley  CA 93924
   United States of America

   Email: nalini.elkins@insidethestack.com

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

   Email: jordi.palet@theipv6company.com

   Gyan S. Mishra
   Verizon Inc.

   Email: gyan.s.mishra@verizon.com

   Chongfeng Xie
   China Telecom

   Email: xiechf@chinatelecom.cn

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