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Internet Engineering Task Force                                  H. Lord
Internet-Draft                                              M. O'Reirdan
Intended status: Informational                              J. Rosenwald
Expires: March 15, 2012                                          Comcast
                                                      September 12, 2011


 Recommendations for the transition of email services from IPv4 to IPv6
                     for Internet Service Providers
            draft-oreirdan-rosenwald-ipv6mail-transition-01

Abstract

   This document contains a phased plan for how providers of email
   services can effect and manage the transition of email services from
   IPv4 to IPv6.  It is expected that this will be effected over a
   period of years and it is unlikely that any transition will
   completely exclude the ongoing possibility of using IPv4 as a
   transport mechanism for email.  This provides one possible
   implementation plan for transitioning email services on the Internet
   from a predominantly IPv4-based connectivity model that suports IPv6.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  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 March 15, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   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.

   This document may contain material from IETF Documents or IETF
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   it for publication as an RFC or to translate it into languages other
   than English.


































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Table of Contents

   1.  Key Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Introduction and Problem Statement . . . . . . . . . . . . . .  5
   3.  Important Notice of Limitations and Scope  . . . . . . . . . .  5
   4.  Transition and a phased model  . . . . . . . . . . . . . . . .  5
   5.  Phase 1: Preparation Phase . . . . . . . . . . . . . . . . . .  6
   6.  Phase 2: Transition Phase  . . . . . . . . . . . . . . . . . .  7
   7.  Phase 3: Post Transition Phase . . . . . . . . . . . . . . . .  7
   8.  SMTP Issues raised by transition to IPv6 . . . . . . . . . . .  8
   9.  Webmail issues raised by transition to IPv6  . . . . . . . . .  8
   10. POP3 issues raised by transition to IPv6 . . . . . . . . . . .  8
   11. IMAP issues raised by transition to IPv6 . . . . . . . . . . .  8
   12. Abuse Issues . . . . . . . . . . . . . . . . . . . . . . . . .  8
   13. Inbound email issues . . . . . . . . . . . . . . . . . . . . .  8
   14. Outbound email issues  . . . . . . . . . . . . . . . . . . . .  9
   15. Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   16. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 10
   17. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   19. Informative references . . . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Document Change Log . . . . . . . . . . . . . . . . . 11
   Appendix B.  Open Issues . . . . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12



























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1.  Key Terminology

   This section defines the key terms used in this document.

1.1.  Email

   Email is a method of exchanging digital messages from an author to
   one or more recipients.

1.2.  Web mail

   A service which offers web based access to email services which would
   otherwise be accessed by dedicated email programs running on the
   device used to access the email.

1.3.  Host

   An end user's host, or computer, as used in the context of this
   document, is intended to refer to a computing device that connects to
   the Internet.  This encompasses devices used by Internet users such
   as personal computers, including laptops, desktops, and netbooks, as
   well as mobile phones, smart phones, home gateway devices, and other
   end user computing devices which are connected or can connect to the
   public Internet and/or private IP networks.

   Increasingly, other household systems and devices contain embedded
   hosts which are connected to or can connect to the public Internet
   and/or private IP networks.  However, these devices may not be under
   interactive control of the Internet user, such as may be the case
   with various smart home and smart grid devices.

1.4.  SMTP

   As defined in RFC2821

1.5.  POP

   As defined in RFC1939 and updated by RFCs 1957, 2449 and 6186

1.6.  IMAP

   As defined in RFC3501

1.7.  Internet Customer

   An end user who leverages a connection to the Internet via an ISP and
   is provisioned with a public IP to communicate on the Internet.




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1.8.  Internet facing server

   A server which is addressed with a public IP address that is able to
   communicate with other publically addressed servers.  A server
   typically hosts a service that can be utilized by the Internet
   community.

1.9.  Internal users

   Known corporate users of the ISP entity.


2.  Introduction and Problem Statement

   With the depletion of IPv4 address space and the transition of
   Internet infrastructure to IPv6, it is necessary to address the way
   in which email services can be transitioned from an IPv4 transport to
   that of IPv6.  It is anticipated that IPv4 will continue for a long
   time as a major transport mechanism for email services of all sorts.
   There are significant issues to be addressed around the matter of
   abuse in an IPv6 based environment which have been addressed and
   largely resolved when operating using IPv4 as a transport mechanism.
   The successful resolution of abuse issues may well be a key
   limitation on the transition of email to an IPv6 environment from the
   point of view of Internet Service providers.


3.  Important Notice of Limitations and Scope

   The issues of abuse specific to IPv6 are not yet fully resolved and
   will need much additional work.  The consideration given to abuse
   issues here should be considered as preliminary and incomplete.


4.  Transition and a phased model

   It is not reasonable to specify the changes that each and every email
   system connected to the Internet must undergo in order to achieve the
   desired transition, as the number of connected systems precludes
   creating one plan that contains such a level of detail.  Further,
   while there are common scenarios that may be specified for
   transitioning individual email systems, the specific timeline and
   mechanisms utilized for a given email system will be unique.  Despite
   these challenges, it is necessary to coordinate expectations on an
   overall basis so that Internet-wide email services are maintained
   throughout the transition.  This document specifies a three-phase
   transition plan that includes preparation, transition, and post-
   transition phases, and delineates the necessary activities within



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   each phase based on the role that an organization plays in the
   provision and use of email services.

   An important distinction made in this transition plan is identifying
   the explicit requirement for existing end-site organizations to add
   IPv6-based connectivity to their email servers during a transition
   phase.  An accelerated adoption of IPv6 for email servers enables new
   organizations in the post-transition phase to be connected to the
   Internet only via IPv6 and still have access to the overall set of
   email servers.

   For nearly every organization, the task of IPv6-enabling their email
   servers is far easier than undertaking an organization-wide adoption
   of IPv6.  Still, the requirement for existing Internet-connected
   organizations to add IPv6 connectivity (even to a small number of
   email systems) will be a significant hurdle and require a level of
   effort that may not be achievable given the lack of compelling
   additional benefits to these organizations [RFC1669].  This
   transition plan presumes that "connectivity is its own reward"
   [RFC1958] and that there still exists a sufficient level of
   cooperation among Internet participants to make this evolution
   possible.  The adoption of a slow rollout and phased approach will
   reduce risk and provide additional insight to abuse issues so that
   further understanding can be gained and solutions developed.

   The three proposed phases are: Preparation Phase, Transition Phase,
   and Post-Transition Phase.


5.  Phase 1: Preparation Phase

   In the Preparation Phase, Service Providers pilot their IPv6 email
   services, and end-site organizations prepare to provide email
   services via IPv6-based connectivity while continuing to provide
   email services via IPv4 connectivity.  During the Preparation Phase,
   the following principles apply:

   PREP1: Service Providers SHOULD offer pilot IPv6-based email service
   to their Internet customers for outbound email submission to the
   Service Providers outbound mail servers.  IPv6-based email services
   MAY be provided via IPv6 transition mechanisms (such as those
   described in [RFC4213], for example) or via native IPv6 network
   service.  This SHOULD be on an infrastructure separate from the IPv4
   infrastructure and on a unique service names from that used for
   production IPv4 traffic.

   PREP2: Organizations SHOULD arrange for IPv6-based Internet
   connectivity for any Internet facing email servers sending, outbound



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   servers (smtp) or receiving email, inbound servers (mx).  Internet-
   facing email servers in this phase SHOULD use separate service names
   per [RFC4472] to avoid impact to production IPv4-based services
   unless the organization supports production IPv6 connectivity.

   PREP3: Organizations MAY provide IPv6-based email services to
   internal user communities.  This would be connectivity from IPv6
   addressed employee computers to the corporate mail servers.


6.  Phase 2: Transition Phase

   In the Transition Phase, Service Providers offer production IPv6 and
   IPv4 services to their Internet customers.  End-site organizations
   provide Internet-facing services in a production manner via IPv6-
   based connectivity in addition to IPv4-based connectivity.  During
   the Transition Phase, the following principles apply:

   TRANS1: Service Providers MUST offer IPv6-based email service to
   their Internet customers.  IPv6-based email service SHOULD be via
   native IPv6 network service but MAY be via IPv6 transition mechanisms
   if necessary.

   TRANS2: Organizations MUST arrange for IPv6-based Internet
   connectivity for any Internet-facing servers (e.g., web, email, and
   domain name servers).  Internet-facing IPv6 servers SHOULD be treated
   as production by the organization, and SHOULD be treated as
   production by other Internet organizations.

   TRANS3: Organizations SHOULD provide IPv6-based email service to
   their internal user communities.


7.  Phase 3: Post Transition Phase

   In the Post-Transition Phase, end-site organizations MUST provide all
   email services via IPv6-based connectivity, thus allowing for new
   Internet customers connected solely by IPv6.  During the Post-
   Transition Phase, the following principles apply:

   POST1: Service Providers MUST offer IPv6-based email service to their
   Internet customers.  IPv6-based email service SHOULD be via native
   IPv6 network service.

   POST2: Organizations MUST arrange for IPv6-based Internet
   connectivity for any Internet-facing email servers.  Internet-facing
   IPv6 email servers MUST be treated as production by the organization,
   and SHOULD be treated as production by other Internet organizations.



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   POST3: Organizations SHOULD provide IPv6-based email service to
   internal user communities and send email via IPv6.

   POST4: Service Providers MAY continue to offer IPv4-based email
   service to their Internet customers.  Organizations MAY continue to
   use IPv4-based email service.  However, IPv6 SHOULD be preferred when
   the option exists to use both services.


8.  SMTP Issues raised by transition to IPv6

   This section will cover issues around the use of SMTP in an IPv6
   based infrastructure.


9.  Webmail issues raised by transition to IPv6

   This section will cover issues around the use of Webmail in an IPv6
   based infrastructure.


10.  POP3 issues raised by transition to IPv6

   This section will cover issues around the use of POP3 in an IPv6
   based infrastructure.


11.  IMAP issues raised by transition to IPv6

   This section will cover issues around the use of IMAP in an IPv6
   based infrastructure.


12.  Abuse Issues

   The lack of a full understanding of all abuse threats SHOULD NOT
   preclude the adoption of IPv6 for mail.  A comprehensive
   understanding of threats will not be available until implementation.


13.  Inbound email issues

   Domain Authentication SHOULD be required and MUST utilize the
   mechanisms outlined in RFC4871, RFC5585 and RFC5617

   Consideration should be given to a "known sender list" for a limited
   number of email servers which are verified as belonging to authorized
   sources of email which will be given volume allowance commensurate



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   with their expected behavior and exempt from the restrictive
   throttles applied to unknown senders.  It is likely that these would
   be the email servers of large ISPs, well known email senders such as
   major Email service providers and other verified sources

   Given the scale of the IPv6 address space, the possibility that a
   connection exhaustion scenario may develop where the number of
   attempted connections to an individual email service may overwhelm
   its ability to provide service.  This may occur either deliberately
   as part of an abusive scenario or inadvertently due to
   misconfiguration.

   Common filtering techniques that are critical for early decision
   making such as real-time blocklists and IP reputation will need to be
   amended for practical use in an IPv6 environment.  Other reputation
   keys such as CIDR reputation and domain reputation should be
   considered.


14.  Outbound email issues

   Submitting of unauthenticated port 25 mail to outbound IPv6 email
   servers MUST be prohibited.  User authentication MUST be required to
   allow users to submit email for delivery.  Users MUST therefore be
   required to authenticate on port 587 or 465 for outbound email
   submission.

   In environments where IP reputation is tracked for outbound
   customers, this is likely to occur for ISPs that do not require
   authentication for sending email outbound.  Single IP reputation will
   become obsolete.  Consideration will have to be made for tracking
   reputation per CIDR.  CIDR reputation would continue to track
   reputation at the lowest unit currently maintained which is the
   customer residence.  The ISP will know this allocation for their
   customers and therefore can rely on this information for reputation
   tracking.

   Public announcement and aggregation of IPv6 addresses into the
   delegated CIDR blocks will be required for the purpose of
   identification and tracking of a single entity.  CIDR reputation can
   then be applied to the whole entity.  There will need to be a
   mechanism to infer or accurately lookup the CIDR allocation.

   Throttling, particularly when off-net sending is allowed, should be
   considered.

   Utilization of 6to4 conversion (modem to server (6) and server to
   external server (4)) can be an intermediate step as described above.



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   Utilization of NAT technologies may also obscure the source IP
   address.

   Given the scale of the IPv6 address space, the possibility that a
   connection exhaustion scenario may develop where the number of
   attempted connections to an individual email service may overwhelm
   its ability to provide service.  This may occur either deliberately
   as part of an abusive scenario or inadvertently due to
   misconfiguration.


15.  Security Considerations

   This document does not address any security issues inherent in IPv6
   itself.  It acknowledges that there are as yet unresolved abuse
   issues specific to deploying email infrastructures based on an IPv6
   transport.  Abuse issues includes spam, phishing and spoofing of
   email addresses.


16.  Privacy Considerations

   This document describes at a high level activities that ISPs should
   be sensitive to, where the collection or communication of PII may be
   possible.  In addition, when performing this transition, ISPs should
   be careful to protect any PII collected whether deliberately or
   inadvertently.

   As noted, any sharing of data from the user to the ISP and/or
   authorized third parties should be done on an opt-in basis.
   Additionally the ISP and or authorized third parties should clearly
   state what data will be shared and with whom the data will be shared
   with.

   Lastly,there my be legal requirements in particular legal
   jurisdictions concerning how long any subscriber-related or other
   data is retained, of which an ISP operating in such a jurisdiction
   should be aware and with which an ISP should comply.


17.  IANA Considerations

   There are no IANA considerations in this document.


18.  Acknowledgements

   The authors wish to acknowledge the following individuals and groups



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   for performing a detailed review of this document and/or providing
   comments and feedback that helped to improve and evolve this
   document:

   None as yet

   Large section of this document are based on RFC5211 "An Internet
   Transition Plan" authored by John Curran which outlines an overall
   transition plan for the Internet from IPv4 to IPv6.


19.  Informative references

   [RFC1669]  Curran, J., "Market Viability as a IPng Criteria",
              RFC 1669, August 1994.

   [RFC1939]  Myers, J. and M. Rose, "Post Office Protocol - Version 3",
              STD 53, RFC 1939, May 1996.

   [RFC1957]  Nelson, R., "Some Observations on Implementations of the
              Post Office Protocol (POP3)", RFC 1957, June 1996.

   [RFC1958]  Carpenter, B., "Architectural Principles of the Internet",
              RFC 1958, June 1996.

   [RFC2449]  Gellens, R., Newman, C., and L. Lundblade, "POP3 Extension
              Mechanism", RFC 2449, November 1998.

   [RFC2821]  Klensin, J., "Simple Mail Transfer Protocol", RFC 2821,
              April 2001.

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213, October 2005.

   [RFC5211]  Curran, J., "An Internet Transition Plan", RFC 5211,
              July 2008.

   [RFC6186]  Daboo, C., "Use of SRV Records for Locating Email
              Submission/Access Services", RFC 6186, March 2011.


Appendix A.  Document Change Log

   [RFC Editor: This section is to be removed before publication]

   -01 version:





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   o  -01 version published


Appendix B.  Open Issues

   [RFC Editor: This section is to be removed before publication]

   No open issues to date


Authors' Addresses

   Heather Lord
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103
   US

   Email: heather_lord@cable.comcast.com
   URI:   http://www.comcast.com


   Michael O'Reirdan
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103
   US

   Email: michael_oreirdan@cable.comcast.com
   URI:   http://www.comcast.com


   Jordan Rosenwald
   Comcast Cable Communications
   One Comcast Center
   1701 John F. Kennedy Boulevard
   Philadelphia, PA  19103
   US

   Email: jordan_rosenwald@cable.comcast.com
   URI:   http://www.comcast.com








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