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Versions: (draft-dionne-sunset4-v4gapanalysis) 00 01 02 03 04 05 06 07 08 09

Network Working Group                                         JP. Dionne
Internet-Draft                                              S. Perreault
Intended status: Informational                                  Viagenie
Expires: January 16, 2014                                        T. Tsou
                                               Huawei Technologies (USA)
                                                                 C. Zhou
                                                     Huawei Technologies
                                                           July 15, 2013


                      Gap Analysis for IPv4 Sunset
                   draft-ietf-sunset4-gapanalysis-03

Abstract

   Sunsetting IPv4 refers to the process of turning off IPv4
   definitively.  It can be seen as the final phase of the migration to
   IPv6.  This memo enumerates difficulties arising when sunsetting
   IPv4, and identifies the gaps requiring additional work.

Status of This Memo

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

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

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

   This Internet-Draft will expire on January 16, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Related Work  . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Remotely Disabling IPv4 . . . . . . . . . . . . . . . . . . .   3
     3.1.  Indicating that IPv4 connectivity is unavailable  . . . .   3
     3.2.  Disabling IPv4 in the LAN . . . . . . . . . . . . . . . .   3
   4.  Client Connection Establishment Behavior  . . . . . . . . . .   3
   5.  Disabling IPv4 in Operating System and Applications . . . . .   4
   6.  On-Demand Provisioning of IPv4 Addresses  . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   10. Informative References  . . . . . . . . . . . . . . . . . . .   5
   Appendix A.  Solution Ideas . . . . . . . . . . . . . . . . . . .   7
     A.1.  Remotely Disabling IPv4 . . . . . . . . . . . . . . . . .   7
       A.1.1.  Indicating that IPv4 connectivity is unavailable  . .   7
       A.1.2.  Disabling IPv4 in the LAN . . . . . . . . . . . . . .   7
     A.2.  Client Connection Establishment Behavior  . . . . . . . .   7
     A.3.  Disabling IPv4 in Operating System and Applications . . .   8
     A.4.  On-Demand Provisioning of IPv4 Addresses  . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The final phase of the migration to IPv6 is the sunset of IPv4, that
   is turning off IPv4 definitively on the attached networks and on the
   upstream networks.

   Some current implementation behavior makes it hard to sunset IPv4.
   Additionally, some new features could be added to IPv4 to make its
   sunsetting easier.  This document analyzes the current situation and
   proposes new work in this area.

   The decision about when to turn off IPv4 is out of scope.  This
   document merely attempts to enumerate the issues one might encounter
   if that decision is made.

2.  Related Work

   [RFC3789], [RFC3790],[RFC3791], [RFC3792], [RFC3793], [RFC3794],
   [RFC3795] and [RFC3796] contain surveys of IETF protocols with their
   IPv4 dependencies.




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3.  Remotely Disabling IPv4

3.1.  Indicating that IPv4 connectivity is unavailable

   PROBLEM 1:  When an IPv4 node boots and requests an IPv4 address
      (e.g., using DHCP), it typically interprets the absence of a
      response as a failure condition even when it is not.

   PROBLEM 2:  Home router devices often identify themselves as default
      routers in DHCP responses that they send to requests coming from
      the LAN, even in the absence of IPv4 connectivity on the WAN.

3.2.  Disabling IPv4 in the LAN

   PROBLEM 3:  IPv4-enabled hosts inside an IPv6-only LAN can auto-
      configure IPv4 addresses [RFC3927] and enable various protocols
      over IPv4 such as mDNS [I-D.cheshire-dnsext-multicastdns] and
      LLMNR [RFC4795].  This can be undesirable for operational or
      security reasons, since in the absence of IPv4, no monitoring or
      logging of IPv4 will be in place.

   PROBLEM 4:  IPv4 can be completely disabled on a link by filtering it
      on the L2 switching device.  However, this may not be possible in
      all cases or may be too complex to deploy.  For example, an ISP is
      often not able to control the L2 switching device in the
      subscriber home network.

   PROBLEM 5:  A host with only Link-Local IPv4 addresses will "ARP for
      everything", as described in Section 2.6.2 of [RFC3927].
      Applications running on such a host connected to an IPv6-only
      network will believe that IPv4 connectivity is available,
      resulting in various bad or sub-optimal behavior patterns.  See
      [I-D.yourtchenko-ipv6-disable-ipv4-proxyarp] for further analysis.

   Some of these problems were described in [RFC2563], which
   standardized a DHCP option to disable IPv4 address auto-
   configuration.  However, using this option requires running an IPv4
   DHCP server, which is contrary to the goal of IPv4 sunsetting.

4.  Client Connection Establishment Behavior

   PROBLEM 6:  Happy Eyeballs [RFC6555] refers to multiple approaches to
      dual-stack client implementations that try to reduce connection
      setup delays by trying both IPv4 and IPv6 paths simultaneously.
      Some implementations introduce delays which provide an advantage
      to IPv6, while others do not [Huston2012].  The latter will pick
      the fastest path, no matter whether it is over IPv4 or IPv6,
      directing more traffic over IPv4 than the other kind of



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      implementations.  This can prove problematic in the context of
      IPv4 sunsetting, especially for Carrier-Grade NAT phasing out
      because CGN does not add significant latency that would make the
      IPv6 path more preferable.  Traffic will therefore continue using
      the CGN path unless other network conditions change.

   PROBLEM 7:  getaddrinfo() [RFC3493] sends DNS queries for both A and
      AAAA records regardless of the state of IPv4 or IPv6 availability.
      The AI_ADDRCONFIG flag can be used to change this behavior, but it
      relies on programmers using the getaddrinfo() function to always
      pass this flag to the function.  The current situation is that in
      an IPv6-only environment, many useless A queries are made.

5.  Disabling IPv4 in Operating System and Applications

   It is possible to completely remove IPv4 support from an operating
   system as has been shown by the work of Bjoern Zeeb on FreeBSD.
   [Zeeb] Removing IPv4 support in the kernel revealed many IPv4
   dependencies in libraries and applications.

   PROBLEM 8:  Completely disabling IPv4 at runtime often reveals
      implementation bugs.  Hard-coded dependencies on IPv4 abound, such
      as on the 127.0.0.1 address assigned to the loopback interface.
      It is therefore often operationally impossible to completely
      disable IPv4 on individual nodes.

   PROBLEM 9:  In an IPv6-only world, legacy IPv4 code in operating
      systems and applications incurs a maintenance overhead and can
      present security risks.

6.  On-Demand Provisioning of IPv4 Addresses

   As IPv6 usage climbs, the usefulness of IPv4 addresses to subscribers
   will become smaller.  This could be exploited by an ISP to save IPv4
   addresses by provisioning them on-demand to subscribers and
   reclaiming them when they are no longer used.  This idea is described
   in [I-D.fleischhauer-ipv4-addr-saving] and [BBF.TR242] for the
   context of PPP sessions.  In these scenarios, the home router is
   responsible for requesting and releasing IPv4 addresses, based on
   snooping the traffic generated by the hosts in the LAN, which are
   still dual-stack and unaware that their traffic is being snooped.

   PROBLEM 10: Dual-stack hosts that implement Happy-Eyeballs [RFC6555]
      will generate both IPv4 and IPv6 traffic even if the algorithm end
      up chooosing IPv6.  This means that an IPv4 address will always be
      requested by the home router, which defeats the purpose of on-
      demand provisioning.




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   PROBLEM 11: Many operating systems periodically perform some kind of
      network connectivity check as long as an interface is up.
      Similarly, applications often send keep-alive traffic
      continuously.  This permanent "background noise" will prevent an
      IPv4 address from being released by the home router.

   PROBLEM 12: Hosts in the LAN have no knowledge that IPv4 is available
      to them on-demand only.  If they had explicit knowledge of this
      fact, they could tune their behaviour so as to be more
      conservative in their use of IPv4.

   PROBLEM 13: This mechanism is only being proposed for PPP even though
      it could apply to other provisioning protocols (e.g., DHCP).

7.  IANA Considerations

   None.

8.  Security Considerations

   It is believed that none of the problems identified in this draft are
   security issues.

9.  Acknowledgements

   Thanks in particular to Nejc Skoberne and Lee Howard for their
   thorough reviews and comments.

   Special thanks to Marc Blanchet who was the driving force behind this
   work.

10.  Informative References

   [BBF.TR242]
              Broadband Forum, "TR-242: IPv6 Transition Mechanisms for
              Broadband Networks", August 2012.

   [Huston2012]
              Huston, G. and G. Michaelson, "RIPE 64: Analysing Dual
              Stack Behaviour and IPv6 Quality", April 2012.

   [I-D.cheshire-dnsext-multicastdns]
              Cheshire, S. and M. Krochmal, "Multicast DNS", draft-
              cheshire-dnsext-multicastdns-15 (work in progress),
              December 2011.

   [I-D.fleischhauer-ipv4-addr-saving]




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              Fleischhauer, K. and O. Bonness, "On demand IPv4 address
              provisioning in Dual-Stack PPP deployment scenarios",
              draft-fleischhauer-ipv4-addr-saving-03 (work in progress),
              August 2012.

   [I-D.yourtchenko-ipv6-disable-ipv4-proxyarp]
              Yourtchenko, A. and O. Owen, "Disable "Proxy ARP for
              Everything" on IPv4 link-local in the presence of IPv6
              global address", draft-yourtchenko-ipv6-disable-
              ipv4-proxyarp-00 (work in progress), May 2013.

   [RFC2563]  Troll, R., "DHCP Option to Disable Stateless Auto-
              Configuration in IPv4 Clients", RFC 2563, May 1999.

   [RFC3493]  Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
              Stevens, "Basic Socket Interface Extensions for IPv6", RFC
              3493, February 2003.

   [RFC3789]  Nesser, P. and A. Bergstrom, "Introduction to the Survey
              of IPv4 Addresses in Currently Deployed IETF Standards
              Track and Experimental Documents", RFC 3789, June 2004.

   [RFC3790]  Mickles, C. and P. Nesser, "Survey of IPv4 Addresses in
              Currently Deployed IETF Internet Area Standards Track and
              Experimental Documents", RFC 3790, June 2004.

   [RFC3791]  Olvera, C. and P. Nesser, "Survey of IPv4 Addresses in
              Currently Deployed IETF Routing Area Standards Track and
              Experimental Documents", RFC 3791, June 2004.

   [RFC3792]  Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in
              Currently Deployed IETF Security Area Standards Track and
              Experimental Documents", RFC 3792, June 2004.

   [RFC3793]  Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in
              Currently Deployed IETF Sub-IP Area Standards Track and
              Experimental Documents", RFC 3793, June 2004.

   [RFC3794]  Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in
              Currently Deployed IETF Transport Area Standards Track and
              Experimental Documents", RFC 3794, June 2004.

   [RFC3795]  Sofia, R. and P. Nesser, "Survey of IPv4 Addresses in
              Currently Deployed IETF Application Area Standards Track
              and Experimental Documents", RFC 3795, June 2004.

   [RFC3796]  Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in
              Currently Deployed IETF Operations & Management Area



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              Standards Track and Experimental Documents", RFC 3796,
              June 2004.

   [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
              Configuration of IPv4 Link-Local Addresses", RFC 3927, May
              2005.

   [RFC4795]  Aboba, B., Thaler, D., and L. Esibov, "Link-local
              Multicast Name Resolution (LLMNR)", RFC 4795, January
              2007.

   [RFC6555]  Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", RFC 6555, April 2012.

   [Zeeb]     , "FreeBSD Snapshots without IPv4 support", ,
              <http://wiki.freebsd.org/IPv6Only>.

Appendix A.  Solution Ideas

A.1.  Remotely Disabling IPv4

A.1.1.  Indicating that IPv4 connectivity is unavailable

   One way to address these issues is to send a signal to a dual-stack
   node that IPv4 connectivity is unavailable.  Given that IPv4 shall be
   off, the message must be delivered through IPv6.

A.1.2.  Disabling IPv4 in the LAN

   One way to address these issues is to send a signal to a dual-stack
   node that auto-configuration of IPv4 addresses is undesirable, or
   that direct IPv4 communication between nodes on the same link should
   not take place.

   A signalling protocol equivalent to the one from [RFC2563] but over
   IPv6 is necessary, using either Router Advertisements or DHCPv6.

   Furthermore, it could be useful to have L2 switches snoop this
   signalling and automatically start filtering IPv4 traffic as a
   consequence.

   Finally, it could be useful to publish guidelines on how to safely
   block IPv4 on an L2 switch.

A.2.  Client Connection Establishment Behavior

   Recommendations on client connection establishment behavior that
   would facilitate IPv4 sunsetting would be appropriate.



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A.3.  Disabling IPv4 in Operating System and Applications

   It would be useful for the IETF to provide guidelines to programmers
   on how to avoid creating dependencies on IPv4, how to discover
   existing dependencies, and how to eliminate them.  Having programs
   and operating systems that behave well in an IPv6-only environment is
   a prerequisite for IPv4 sunsetting.

A.4.  On-Demand Provisioning of IPv4 Addresses

   No idea.

Authors' Addresses

   Jean-Philippe Dionne
   Viagenie
   246 Aberdeen
   Quebec, QC  G1R 2E1
   Canada

   Phone: +1 418 656 9254
   Email: jean-philippe.dionne@viagenie.ca
   URI:   http://viagenie.ca


   Simon Perreault
   Viagenie
   246 Aberdeen
   Quebec, QC  G1R 2E1
   Canada

   Phone: +1 418 656 9254
   Email: simon.perreault@viagenie.ca
   URI:   http://viagenie.ca


   Tina Tsou
   Huawei Technologies (USA)
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Phone: +1 408 330 4424
   Email: tina.tsou.zouting@huawei.com







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   Cathy Zhou
   Huawei Technologies
   Huawei Industrial Base
   Bantian, Shenzhen
   China

   Email: cathy.zhou@huawei.com












































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