Issues with IP Address Sharing
RFC 6269

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Internet Engineering Task Force (IETF)                      M. Ford, Ed.
Request for Comments: 6269                              Internet Society
Category: Informational                                     M. Boucadair
ISSN: 2070-1721                                           France Telecom
                                                               A. Durand
                                                        Juniper Networks
                                                                P. Levis
                                                          France Telecom
                                                              P. Roberts
                                                        Internet Society
                                                               June 2011

                     Issues with IP Address Sharing

Abstract

   The completion of IPv4 address allocations from IANA and the Regional
   Internet Registries (RIRs) is causing service providers around the
   world to question how they will continue providing IPv4 connectivity
   service to their subscribers when there are no longer sufficient IPv4
   addresses to allocate them one per subscriber.  Several possible
   solutions to this problem are now emerging based around the idea of
   shared IPv4 addressing.  These solutions give rise to a number of
   issues, and this memo identifies those common to all such address
   sharing approaches.  Such issues include application failures,
   additional service monitoring complexity, new security
   vulnerabilities, and so on.  Solution-specific discussions are out of
   scope.

   Deploying IPv6 is the only perennial way to ease pressure on the
   public IPv4 address pool without the need for address sharing
   mechanisms that give rise to the issues identified herein.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

Ford, et al.                  Informational                     [Page 1]
RFC 6269             Issues with IP Address Sharing            June 2011

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6269.

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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Ford, et al.                  Informational                     [Page 2]
RFC 6269             Issues with IP Address Sharing            June 2011

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Shared Addressing Solutions  . . . . . . . . . . . . . . . . .  4
   3.  Analysis of Issues as They Relate to First and Third
       Parties  . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Content Provider Example . . . . . . . . . . . . . . . . . . .  8
   5.  Port Allocation  . . . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  Outgoing Ports . . . . . . . . . . . . . . . . . . . . . .  9
     5.2.  Incoming Ports . . . . . . . . . . . . . . . . . . . . . . 10
       5.2.1.  Port Negotiation . . . . . . . . . . . . . . . . . . . 11
       5.2.2.  Connection to a Well-Known Port Number . . . . . . . . 12
       5.2.3.  Port Discovery Mechanisms  . . . . . . . . . . . . . . 12
   6.  Impact on Applications . . . . . . . . . . . . . . . . . . . . 12
   7.  Geo-location and Geo-proximity . . . . . . . . . . . . . . . . 14
   8.  Tracking Service Usage . . . . . . . . . . . . . . . . . . . . 15
   9.  ICMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
   10. MTU  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
   11. Fragmentation  . . . . . . . . . . . . . . . . . . . . . . . . 16
   12. Traceability . . . . . . . . . . . . . . . . . . . . . . . . . 17
   13. Security . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     13.1. Abuse Logging and Penalty Boxes  . . . . . . . . . . . . . 18