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IPv6 Operations Working Group                                G. Lencse
Internet Draft                                                    BUTE
Intended status: Informational                       J. Palet Martinez
Expires: April 2018                                   The IPv6 Company
                                                             L. Howard
                                                          R. Patterson
                                                                Sky UK
                                                       October 6, 2018

         Pros and Cons of IPv6 Transition Technologies for IPv4aaS


   Several IPv6 transition technologies can be used to provide IPv4-as-
   a-service (IPv4aaS) to the customers, while the ISPs have only IPv6
   in their access and or core network. All these technologies have
   their advantages and disadvantages. Depending on several various
   conditions and preferences, different technologies may prove to be
   the most appropriate solution. This document examines the five most
   prominent IPv4aaS technologies considering several different aspects
   in order to provide network operators with an easy to use guideline
   for selecting the technology that suit their needs the best.

Status of this Memo

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   This Internet-Draft will expire on April 6, 2019.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

   1. Introduction ................................................ 3
   2. High-level Architectures and their Consequences ............. 3
      2.1. Service Provider Network Traversal ..................... 3
      2.2. IPv4 Address Sharing ................................... 4
   3. More Detailed Analysis ...................................... 4
      3.1. Details of Architectural Differences ................... 4
         3.1.1. 464XLAT ........................................... 4
         3.1.2. DS-Lite ........................................... 4
         3.1.3. Lw4o6 ............................................. 4
         3.1.4. MAP-E ............................................. 5
         3.1.5. MAP-T ............................................. 5
      3.2. Tradeoff between Port Number Efficiency and Stateless
           Operation .............................................. 5
      3.3. Support for Server Operation ........................... 6
      3.4. Support and Implementations ............................ 6
         3.4.1. OS Support......................................... 6
         3.4.2. Support in Cellular and Broadband Networks......... 6
         3.4.3. Implementation Code Sizes ......................... 6
   4. Performance Comparison ...................................... 7
   5. Security Considerations ..................................... 7
   6. IANA Considerations  ........................................ 8
   7. Conclusions ................................................. 8
   8. References .................................................. 8
      8.1. Normative References ................................... 8
      8.2. Informative References ................................. 9
   9. Acknowledgments ............................................ 10

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1. Introduction

   IETF has standardized a high number of IPv6 transition technologies
   [Len2017] and occupied a neutral position trusting the selection to
   the market. In the upcoming years, several network operators would
   like to get rid of the burden of maintaining IPv4 in their access
   and/or core networks. This document deals with five different
   solutions, each of which can be used to provide an IPv4 service
   using an IPv6-only access/core network. The following IPv6
   transition technologies are covered: 464XLAT [RFC6877], DS-Lite
   (Dual Stack Lite) [RFC6333], lw4o6 (Lightweight 4over6) [RFC7596],
   MAP-E [RFC7597] and MAP-T [RFC7599].

2. High-level Architectures and their Consequences

2.1. Service Provider Network Traversal

   As for the high-level solution of the IPv6 service provider network
   traversal, MAP-T use double translation (first at the CE from IPv4
   to IPv6, NAT46, and then from IPv6 to IPv4, NAT64, at the service
   provider network), 464XLAT may use single (NAT64, IPv6 to IPv4) or
   double translation (as MAP-T), depending on different factors, such
   as the use of DNS by the applications and the availability of a
   DNS64. DS-Lite, lw4o6 and MAP-E encapsulate the IPv4 packets into
   IPv6 packets. Each solution has its own advantages and drawbacks.
   Double translation results in only 20 bytes overhead (the difference
   in the minimum header size between IPv4 and IPv6), whereas the
   overhead of the encapsulation is 40 bytes (because both, the IPv4
   and IPv6 headers are needed, compared with only the IPv4 one). The
   difference may be significant in the case of small packet sizes or
   when the larger one results in fragmentation.

   On the one hand, the first step of the double translation case is a
   stateless NAT from IPv4 to IPv6 implemented as SIIT (Stateless
   IP/ICMP Translation Algorithm) [RFC7915], which does not translate
   IPv4 options and/or multicast IP/ICMP packets, whereas with
   encapsulation-based technologies these remain intact.

   On the other hand, single and double translation results in "normal"
   IPv6 traffic which can be inspected, e.g., by hashing algorithms,
   and firewalls, whereas encapsulation results in IPv4-embedded IPv6
   packets and their interpretation requires special software/hardware
   for DPI (deep-packet-inspection).

   The worst case is DS-Lite, which is also doing double stateful
   translation (NAT44 at the CE, NAT44 at the AFTR).

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   Another consequence is that the solutions using double translation
   can carry only TCP, UDP or ICMP over IP, when they are used with
   IPv4 address sharing (please refer to section 3.3 for more details),
   whereas the solutions using encapsulation can carry any other
   protocols over IP, too.

2.2. IPv4 Address Sharing

   All five technologies support IPv4 address sharing, which has severe
   consequences described in [RFC6269].

   The efficiency of the address sharing of the five technologies is
   significantly different, it is discussed in section 3.2.

   We note that lw4o6, MAP-E and MAP-T may not necessarily be
   configured to do IPv4 address sharing, see the details in Section
   3.3, however in that case there is no advantage in terms of public
   IPv4 addresses saving.

3. More Detailed Analysis

3.1. Details of Architectural Differences

3.1.1. 464XLAT

   CLAT performs a stateless translation from IPv4 to IPv6 [RFC7915].
   It uses IPv4-embedded IPv6 addresses [RFC6052] for both source
   address and destination address. PLAT performs stateful NAT64

3.1.2. DS-Lite

   The B4 (Basic Bridging BroadBand) element encapsulates the IPv4
   packets into IPv6 packets. The AFTR (Address Family Transition
   Router) de-encapsulates the IPv4 packets from the IPv6 packets and
   performs stateful NAPT (Network Address and Port Translation).

3.1.3. Lw4o6

   Lightweight 4over6 is a variant of DS-Lite. The difference is, that
   the stateful NAPT is moved from the AFTR to the B4 element. It uses
   a provisioning mechanism to determine the size of the limited port
   set per user.

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3.1.4. MAP-E

   The CE (Customer-Edge) router first encapsulates IPv4-in-IPv6.
   Packets must traverse a MAP BR to be [de-]encapsulated.

3.1.5. MAP-T

   The CE (Customer Edge) router first performs a NAT44 to transform
   the source addresses and source port numbers of the IPv4 packets
   into a predefined range, the size of which is a design parameter.
   The CE router then performs stateless translation from IPv4 to IPv6
   [RFC7915], which translates the IPv4 address and the port numbers
   into the IPv6 address space. The transformations may be fine-tuned
   by the mapping rules. The MAP BR (Border Relay) performs stateless
   translation from IPv4 to IPv6 [RFC7915].

3.2. Tradeoff between Port Number Efficiency and Stateless Operation

   464XLAT and DS-Lite use stateful NAPT at the PLAT and AFTR devices,
   respectively. This may cause scalability issues. Lw4o6, MAP-E and
   MAP-T avoid using NAPT in the service provider network. Its cost is
   that they have to limit the port numbers available for a user, which
   is also the case for DS-Lite. Determining the optimal size of the
   port set is not an easy task. On the one hand, the lack of port
   situation may cause serious problems in the operation of certain
   programs (e.g. the consequences of the session number limitation due
   to port number shortage were impressively demonstrated using Google
   Map in [Miy2010]). The port number consumption of different
   applications is highly varying and e.g. in the case of web browsing
   it depends on several factors [Rep2014]. And there may be several
   users behind a CPE, especially in the wired case (e.g. Internet is
   used by different members of a family simultaneously), thus
   sometimes even a few thousands ports may not be enough. However, on
   the other hand, assigning too many ports per user will result in
   waste of public IPv4 addresses, which is a scarce and expensive
   resource. Therefore, 464XLAT is much more efficient in terms of port
   number and thus public IP address saving. The price is the stateful
   operation in the service provider network, which is allegedly does

   We also note that NAT64 does not pre-allocate ports for customers
   but allocates them "on the fly" (which means that even the same
   customer is using ports from different addresses, and most of the
   time, different customers get ports from any given addresses), and
   in fact this creates many application/service providers (Sony

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   PlayStation Network, OpenDNS, etc.) to permanently black-list the
   IPv4 ranges once they are detected to be used for address sharing.

3.3. Support for Server Operation

   Lw4o6, MAP-E and MAP-T may be configured without IPv4 address
   sharing, allowing exclusive use of all ports, and non-port-based
   layer 4 protocols. Thus, they may also be used to support server
   operation, when public IPv4 addresses are assigned to the
   subscribers, however, then there is no advantage in terms of IPv4
   public addresses saving.

   It is also possible to configure specific ports mapping in
   464XLAT/NAT64 using EAMT [RFC7757], which means that only those
   ports are "lost" from the pool of addresses, so there is a higher
   maximization of the total usage of IPv4/port resources.

3.4. Support and Implementations

3.4.1. OS Support

   As for 464XLAT, client support exists in Windows 10, Linux
   (including Android), Windows Mobile, and Chrome OS, but it is
   missing from iOS and MacOS. For the other four solutions, we are not
   aware of any OS support.

3.4.2. Support in Cellular and Broadband Networks

   Several cellular networks use 464XLAT, whereas we are not aware of
   any deployment of the four other technologies in cellular networks,
   as they are not supported.

   In broadband networks, there are some deployments of 464XLAT, MAP-E
   and MAP-T. Both, lw4o6 and DS-Lite have more deployments, having
   been up now DS-Lite the most used one, but lw4o6 taking over in the
   last years.

3.4.3. Implementation Code Sizes

   As for complexity hint, the code size reported from OpenWRT
   implementation is 17kB, 35kB, 15kB, 35kB, and 48kB for 464XLAT,
   lw4o6, DS-Lite, MAP-E, MAP-T, and lw4o6, respectively

   We note that the support for all five technologies requires much
   less code size than the total sum of the above quantities, because

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   they contain a lot of common functions (data plane is shared among
   several of them).

4. Performance Comparison

   We plan to compare the performances of the most prominent free
   software implementations of the five IPv6 transition technologies
   using the methodology described in "Benchmarking Methodology for
   IPv6 Transition Technologies" [RFC8219].

   On the one hand, the Dual DUT Setup of RFC8219 makes it possible to
   use the existing "Benchmarking Methodology for Network Interconnect
   Devices" [RFC2544] compliant measurement devices, however, this
   setup has the drawback that the performances of the CE and of the
   ISP side device (e.g. the CLAT and the PLAT of 464XLAT) are measured
   together. In order to measure the performance of only one of them,
   we need to ensure that the desired one is the bottleneck.

   On the other hand, the Single DUT Setup of [RFC8219] makes it
   possible to benchmark the selected device separately, however, no
   [RFC8219] compliant testers available yet. A DPDK-based software
   Tester for stateless NAT64 is currently under development and it is
   expected to be available this autumn as a free software. XXX FROM

   Any volunteers for developing [RFC8219] compliant measurement

5. Security Considerations

   According to the simplest model, the number of bugs is proportional
   to the number of code lines. Please refer to section 3.4.3 for code
   sizes of CE implementations.

   For all five technologies, the CE device should contain a DNS proxy.
   However, the user may change DNS settings. If it happens and lw4o6,
   MAP-E and MAP-T are used with significantly restricted port set,
   which is required for an efficient public IPv4 address sharing, the
   entropy of the source ports is significantly lowered (e.g. from 16
   bits to 10 bits, when 1024 port numbers are assigned to each
   subscriber) and thus these technologies are theoretically less
   resilient against cache poisoning, see [RFC5452]. However, an
   efficient cache poisoning attack requires that the subscriber
   operates an own caching DNS server and the attack is performed in
   the service provider network. Thus, we consider the chance of the
   successful exploitation of this vulnerability as low.

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   An in-depth security analysis of all five IPv6 transition
   technologies and their most prominent free software implementations
   according to the methodology defined in [Len2018] is planned.

6. IANA Considerations


7. Conclusions


8. References

8.1. Normative References

   [RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
             Network Interconnect Devices", RFC 2544, DOI
             10.17487/RFC2544, March 1999, <http://www.rfc-

   [RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
             Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
             DOI 10.17487/RFC6052, October 2010, <http://www.rfc-

   [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
             NAT64: Network Address and Protocol Translation from IPv6
             Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
             April 2011, <http://www.rfc-editor.org/info/rfc6146.

   [RFC6269] Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
             Roberts, "Issues with IP Address Sharing", RFC 6269, DOI
             10.17487/RFC6269, June 2011, <http://www.rfc-

    [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,

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

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

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

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

   [RFC7915] Bao, C., Li, X., Baker, F., Anderson, T., and F. Gont,
             "IP/ICMP translation algorithm", RFC 7915, DOI:
             10.17487/RFC7915, June 2016, <http://www.rfc-

   [RFC7757] Anderson, T., and A. Leiva Popper "Explicit Address
             Mappings for Stateless IP/ICMP Translation", RFC 7757, DOI
             10.17487/RFC7757, February 2016, <http://www.rfc-

   [RFC8219] Georgescu, M., Pislaru, L., and G. Lencse, "Benchmarking
             Methodology for IPv6 Transition Technologies", IETF RFC
             8219, DOI: 10.17487/RFC8219, Aug. 2017, <http://www.rfc-

8.2. Informative References

   [Len2017] Lencse, G., and Y. Kadobayashi, "Survey of IPv6 Transition
             Technologies for Security Analysis", IEICE Communications
             Society Internet Architecture Workshop, Tokyo, Japan, Aug.
             28, 2017, IEICE Tech. Rep., vol. 117, no. 187, pp. 19-24.

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   [Len2018] Lencse, G., and Y. Kadobayashi, "Methodology for the
             identification of potential security issues of different
             IPv6 transition technologies: Threat analysis of DNS64 and
             stateful NAT64", Computers & Security (Elsevier), vol. 77,
             no. 1, pp. 397-411, August 1, 2018, DOI:

   [Miy2010] Miyakawa, S., "IPv4 to IPv6 transformation schemes", IEICE
             Trans. Commun., vol.E93-B, no.5, pp.1078-1084, May 2010.

   [Rep2014] Repas, S., Hajas, T., and G. Lencse, "Port number
             consumption of the NAT64 IPv6 transition technology",
             Proc. 37th Internat. Conf. on Telecommunications and
             Signal Processing (TSP 2014), Berlin, Germany, pp.66-72,
             Jul. 1-3, 2014. DOI: 10.1109/TSP.2015.7296411

9. Acknowledgments

   The authors would like to acknowledge the inputs of Ole Troan, Mark
   Andrews, Edwin Cordeiro, Fred Baker, Alexandre Petrescu, and TBD.

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

   Copyright (c) 2018 IETF Trust and the persons identified as authors
   of the code. All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, is permitted pursuant to, and subject to the license
   terms contained in, the Simplified BSD License set forth in Section
   4.c of the IETF Trust's Legal Provisions Relating to IETF Documents

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Authors' Addresses

   Gabor Lencse
   Budapest University of Technology and Economics
   Magyar Tudosok korutja 2.
   H-1117 Budapest, Hungary

   Email: lencse@hit.bme.hu

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

   Email: jordi.palet@theipv6company.com

   Lee Howard
   9940 Main St., Suite 200
   22031, USA
   Email: lee@asgard.org

   Richard Patterson
   Sky UK
   1 Brick Lane
   London, E1 6PU
   United Kingdom

   Email: richard.patterson@sky.uk

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