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Network Working Group                                          S. Barber
Internet-Draft                                        Cox Communications
Intended status: Informational                                 O. Delong
Expires: January 5, 2012                              Hurricane Electric
                                                           C. Grundemann
                                                               CableLabs
                                                            V. Kuarsingh
                                                   Rogers Communications
                                                           B. Schliesser
                                                           Cisco Systems
                                                            July 4, 2011


           ARIN Draft Policy 2011-5: Shared Transition Space
              draft-bdgks-arin-shared-transition-space-00

Abstract

   This memo encourages the reservation of a Shared Transition Space, an
   IPv4 prefix designated for local use within service provider networks
   during the period of IPv6 transition.  This address space has been
   proposed at various times in the IETF, and more recently by the ARIN
   policy development community.

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 5, 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



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   (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.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Applicability  . . . . . . . . . . . . . . . . . . . . . .  5
       2.1.1.  CGN  . . . . . . . . . . . . . . . . . . . . . . . . .  5
       2.1.2.  Extranet . . . . . . . . . . . . . . . . . . . . . . .  5
       2.1.3.  SP Services  . . . . . . . . . . . . . . . . . . . . .  5
         2.1.3.1.  Private Intranet . . . . . . . . . . . . . . . . .  5
     2.2.  Alternatives . . . . . . . . . . . . . . . . . . . . . . .  6
       2.2.1.  Globally Unique  . . . . . . . . . . . . . . . . . . .  6
       2.2.2.  Private  . . . . . . . . . . . . . . . . . . . . . . .  6
       2.2.3.  Class E  . . . . . . . . . . . . . . . . . . . . . . .  7
       2.2.4.  Prefix Squatting . . . . . . . . . . . . . . . . . . .  7
       2.2.5.  Regional Re-use of Allocated Prefix  . . . . . . . . .  8
       2.2.6.  Consortium . . . . . . . . . . . . . . . . . . . . . .  8
   3.  Analysis of Benefits . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Continued Operation Post-exhaustion  . . . . . . . . . . .  9
     3.2.  Delayed Need for CGN Deployment  . . . . . . . . . . . . .  9
     3.3.  Recovery of Existing Addresses . . . . . . . . . . . . . .  9
       3.3.1.  Re-deployment Where Needed . . . . . . . . . . . . . .  9
       3.3.2.  Return or Transfer . . . . . . . . . . . . . . . . . .  9
     3.4.  Impact on Allocations / RIR Inventory  . . . . . . . . . . 10
     3.5.  Benefit of Standardization . . . . . . . . . . . . . . . . 10
     3.6.  IPv6 Deployments . . . . . . . . . . . . . . . . . . . . . 10
   4.  Analysis of Detractors' Arguments  . . . . . . . . . . . . . . 11
     4.1.  It Breaks  . . . . . . . . . . . . . . . . . . . . . . . . 11
       4.1.1.  NAT is Bad . . . . . . . . . . . . . . . . . . . . . . 11
       4.1.2.  Breaks Bad Host Assumptions  . . . . . . . . . . . . . 11
       4.1.3.  Potential Misuse as Private Space  . . . . . . . . . . 11
     4.2.  It's Not Needed  . . . . . . . . . . . . . . . . . . . . . 12
       4.2.1.  Nobody Will Use It . . . . . . . . . . . . . . . . . . 12
       4.2.2.  ISPs Are Not Actually Growing  . . . . . . . . . . . . 12
       4.2.3.  RIR IPv4 Inventory is Not Actually Exhausted . . . . . 12
       4.2.4.  ISP IPv4 Inventory is Not Actually Exhausted . . . . . 13
     4.3.  Address Inventory  . . . . . . . . . . . . . . . . . . . . 13
       4.3.1.  Shared Transition Space Uses Up Address Inventory  . . 13
       4.3.2.  /10 is not Enough  . . . . . . . . . . . . . . . . . . 13
       4.3.3.  It Won't Delay RIR Exhaustion  . . . . . . . . . . . . 13
     4.4.  IPv6 Arguments . . . . . . . . . . . . . . . . . . . . . . 14
       4.4.1.  Use IPv6 Instead . . . . . . . . . . . . . . . . . . . 14
       4.4.2.  Delay of IPv6 Deployment . . . . . . . . . . . . . . . 14



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     4.5.  History  . . . . . . . . . . . . . . . . . . . . . . . . . 15
   5.  ARIN Draft Policy 2011-5 . . . . . . . . . . . . . . . . . . . 15
     5.1.  History  . . . . . . . . . . . . . . . . . . . . . . . . . 15
     5.2.  Policy Text  . . . . . . . . . . . . . . . . . . . . . . . 16
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
   9.  Informative References . . . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21










































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1.  Introduction

   As the Internet community approaches exhaustion of unallocated IPv4
   numbers, the value of globally unique addresses is becoming manifest.
   More than ever network operators recognize the need to transition to
   the IPv6 address family.  However, the immediate necessity of
   continued IPv4 connectivity poses a near-term challenge - without
   adequate IPv4 resources, most network operators must deploy more
   efficient addressing architectures and many must deploy address-
   sharing technologies.

   In order to facilitate these operators' need for near-term IPv4
   connectivity, [I-D.weil-shared-transition-space-request] proposes the
   reservation of a /10 IPv4 prefix for use in Service Provider (SP)
   networks.  Referred to as Shared Transition Space, this address block
   would facilitate SP deployment of non-unique address plans that do
   not conflict with traditional Private [RFC1918] address space.  By
   using the Shared Transition Space operators may deploy CGN
   [I-D.ietf-behave-lsn-requirements] internal networks, extranet
   [RFC4364] communities, and/or SP-local services without consuming
   globally unique addresses.

   However, given the Feb 2011 depletion of the IANA Free Pool inventory
   [NRO-IANA-exhaust] it is not currently possible for the IANA to
   reserve an IPv4 /10 prefix as recommended in
   [I-D.weil-shared-transition-space-request].  Thus the ARIN community
   has proposed in Draft Policy [ARIN-2011-5] the reservation of a
   Shared Transition Space from the ARIN inventory of unallocated IPv4
   numbers.  After much discussion by the ARIN community, [ARIN-2011-5]
   was recommended by the ARIN Advisory Council for approval by the ARIN
   Board of Trustees.

   Essentially similar to [I-D.weil-shared-transition-space-request],
   Draft Policy [ARIN-2011-5] is currently pending ARIN Board approval.
   The ARIN Board has asked for IAB clarification with regard to
   responsibilities outlined in [RFC2860] and has received a response
   [IAB-response] indicating that the IETF holds responsibility for the
   reservation of specialized address blocks.  Thus, this memo is a
   discussion of the merits of a Shared Transition Space, and is a call
   for consensus between the IETF and RIR communities that such an
   address reservation should be made.


2.  Background







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2.1.  Applicability

   There are a number of use-cases for the Shared Transition Space.
   This section discusses the primary scenarios envisioned at the time
   of this writing.

2.1.1.  CGN

   A primary use-case for the Shared Transition Space will be deployment
   in CGN internal networks, as described in
   [I-D.ietf-behave-lsn-requirements].  A key benefit of CGN is the
   ability to share a smaller number of Globally Unique Addresses (GUA)
   amongst a larger number of end-sites.

   In one CGN deployment scenario sometimes referred to as NAT444
   [I-D.shirasaki-nat444-isp-shared-addr], the CGN internal network is
   numbered with IPv4 addresses that are not globally routed while the
   end-sites are numbered with Private [RFC1918] addresses.  In this
   scenario the Shared Transition Space will be used to provide
   contextually unique IPv4 addresses to end-site CPE devices and
   intermediate infrastructure.

2.1.2.  Extranet

   Another use-case for the Shared Transition Space is in building
   private Extranet community networks.  In these networks, multiple
   end-sites administered by different organizations are connected
   together via VPN technology.  Because different organizations may be
   using Private address space internally, an Extranet addressing plan
   is often unable to effectively use Private address space without
   conflicting.  The Shared Transition Space will provide an alternative
   to the use of GUA space in such a scenario.

2.1.3.  SP Services

   In networks that contain local services (such as nameservers, content
   repositories or caches, etc) the Shared Transition Space will offer
   an alternative to GUA.  For instance, video content servers that are
   available only to customers directly connected to the SP network
   might be addressed from the Shared Transition Space, preserving GUA
   for services that require global connectivity.

2.1.3.1.  Private Intranet

   Many service providers have deployed a hierarchical network using
   Private [RFC1918] space, which has served them well for many years.
   Due in large part to the explosive growth of new services they have
   run out of available private space.  While it is possible to re-



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   engineer internal networks, such activity is customer impacting and
   operationally complex.  Making more private space available for
   service providers allows for a manageable transition to IPv6 without
   significant impact to customers.

2.2.  Alternatives

   A number of possible alternatives to Shared Transition Space have
   been proposed and/or discussed by the Internet community.  See, for
   instance, [I-D.azinger-additional-private-ipv4-space-issues] for a
   discussion of alternatives and potential issues.  This section
   outlines these possible alternatives and briefly discusses their
   applicability.

2.2.1.  Globally Unique

   Every discussion of the Shared Transition Space begins with an
   assumption that Globally Unique Addresses (GUA) are a preferable
   choice for numbering.  This is almost always technically true.
   However, given the fundamental driver of IPv4 address exhaustion, GUA
   is not a pragmatic alternative to the Shared Transition Space.

   Additionally, if various organizations use various GUA ranges to
   number CGN zones, it will be difficult for other networks and/or
   systems to deterministically know if the endpoints are using true
   internet reachable IPs, or if the source network may be using them as
   CGN zone space.  This situation would likely lead to additional
   technical issues during various leakage conditions, filter rule
   issues (routing) and for CDN or other third party providers who may
   be present within the source network, to name a few.

2.2.2.  Private

   In each of the use-cases for Shared Transition Space, it may be
   possible to instead use Private [RFC1918] address space.  In
   situations where all endpoints in the network are managed by a single
   organization, this may be a viable option.  However when end-sites
   are administered by different organizations and/or individuals, the
   possibility of address conflict becomes a significant risk to
   operations.

   A study of DNS traffic [v6ops-msg06187] has shown that effectively
   all of the existing Private [RFC1918] address space is currently
   being used by end-sites attached to the Internet.  While individual
   network environments may vary in this regard, most SP operators face
   the risk that their use of Private address space will conflict with
   their customer end-sites.




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   In the event of conflict, it is possible that the end-site CPE will
   fail and/or not function correctly.  Some CPE implementations are
   known to support overlapping addresses on the "inside" and "outside"
   interfaces, however many others are known to fail under such
   circumstances.  For SP operators, the Shared Transition Space offers
   a less risky alternative to GUA that retains the benefit of non-
   conflict.

   Also, the use of Private [RFC1918] address space on interfaces and
   hosts often causes default behaviours on such hosts which may not be
   desirable when the endpoint is actually connected to the Internet.
   There are often behavioural expectations for Internet connected
   endpoints, regardless of them being subject to a NAT.

   Incorrect affiliation of the WAN side interface being in a
   "protected" zone and/or on a trusted network may not be desirable.
   With NAT444 deployments, it is important that the endpoint (i.e.
   CPE) behave like any other internet node.  One example of this from
   our testing was observed behaviours where some CPEs did not filter
   and/or firewall correctly when Private [RFC1918] address space was
   used on both WAN and LAN interfaces.

2.2.3.  Class E

   One proposed alternative to Shared Transition Space is the re-
   classification and use of the 240.0.0.0/4 "Class E" address space as
   unicast.  This has been proposed, for instance, by
   [I-D.fuller-240space] and [I-D.wilson-class-e].  While this
   alternative might be possible in tightly constrained environments,
   where all of the network elements are known to support Class E
   address space, it is not generally useful in the use-cases described
   above.  At this time, a significant number of IPv4 stack
   implementations treat the Class E address space as reserved and will
   not route, forward, and/or originate traffic for that range.

2.2.4.  Prefix Squatting

   An unfortunate alternative to the Shared Transition Space is "prefix
   squatting", in which the operator re-uses another organization's IPv4
   allocation for their own numbering needs.  When this approach results
   in the other organization's prefix being announced globally by the
   "squatting" operator, it is often referred to as "prefix hijacking".
   However, this discussion is focused on scenarios in which the prefix
   is not announced globally but is, rather, used for internal numbering
   only.

   In this scenario, the allocation may not be routed globally by the
   legitimate address holder, making it attractive for such purposes.



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   Or it may be routed but "uninteresting" to the SP network's
   endpoints.  In either case there is a potential for conflict in the
   event that any end-site actually wishes to communicate with the
   legitimate address holder.  As such, this alternative is to be
   discouraged with prejudice.

   It is important to note that there are no behavioural advantages to
   using "squat space" over using assigned "shared space".  Both options
   subject the CPE to the same general behaviours (GUA space, but not
   globally reachable).  The only real difference is the negative
   impacts of squatting (as noted above) and the advantages of a
   community coordinated and standardized prefix.

   The primary reason that any network would be likely to adopt "prefix
   squatting" is if they are faced with the operational realities of CGN
   before/without the allocation of a shared transition space.

2.2.5.  Regional Re-use of Allocated Prefix

   Similar to "Prefix Squatting" but significantly less dangerous, this
   alternative involves the reuse by an operator of their own address
   allocations.  In this scenario, a network operator might use the same
   prefix for multiple "regions" and/or extranet communities.  For
   instance, in CGN deployments the operator might reuse the same GUA
   prefix across multiple geographic regions (e.g. without announcing it
   globally).

   Here again, it is important to note that there are no behavioural
   advantages gained over a "shared space" but there is the added
   community cost of each network having to dedicate a unique block of
   addresses to this purpose, consuming far more resources than a single
   block of "shared space".

2.2.6.  Consortium

   In the event that the Internet community doesn't set aside an IPv4
   prefix for Shared Transition Space, it is possible that a number of
   SP operators can come together and designate an address block to be
   "shared" amongst them for an identical purpose.  This would have the
   same technical merits as an IETF and/or RIR sponsored Shared
   Transition Space, however it would lack the efficiency of a community
   coordinated and standardized prefix for such purposes, gain no
   behavioural advantages, remove the deterministic nature of managing a
   single range and also subjects the Internet (users of the space) to
   additional risk since any member of the consortium who has
   contributed space could later pull out and potentially cause
   disruptions in multiple networks.




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3.  Analysis of Benefits

3.1.  Continued Operation Post-exhaustion

   Availability of a Shared Transition Space helps SPs continue to meet
   the demands of IPv4 address and/or connectivity post exhaustion.  For
   environments where CGN in a NAT444 scenario is necessary, addresses
   from this space can be used to provide intermediary network
   addressing assisting in provided IPv4 flow continuity for new or
   migrating customers.

   In other circumstances, the shared transition space allows SPs to
   number devices in the network which do not require globally
   reachablity without the need for fulfillment thorough an RIR.

3.2.  Delayed Need for CGN Deployment

   If operators are required to us their individually allocated GUA
   where "shared space" would have applied, they will face exhaustion
   sooner and thus be forced to deploy CGN sooner as well.  Operators
   can postpone this deployment of CGN by using "shared space" for
   internal uses, because that allows more efficient use of their
   remaining GUA in places where global uniqueness is truly mandatory.

3.3.  Recovery of Existing Addresses

   The shared transition space can also be used to number and reclaim
   IPv4 addresses within provider networks which do not require global
   reachability.  This option can be used by many networks worldwide, it
   provides an option for using currently assigned space much more
   efficiently.

3.3.1.  Re-deployment Where Needed

   Operators can re-deploy recovered addresses for customers that need
   them (including new / static / GUA customers), hosted servers, etc.
   or to facilitate other efforts that might provide even more efficient
   use of GUA space within the network.  The freed addresses can be
   assigned to endpoints which require IPv4 global reachablity and thus
   help delay and/or remove the need for CGN.

3.3.2.  Return or Transfer

   In cases where the operator doesn't need the recovered addresses,
   they can be made available to others that do need them.  This may be
   through voluntary return the RIR, or through transfer to another
   network operator (perhaps via a market mechanism).




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   If an SP determines that the space recovered is not needed, the space
   can be returned or transferred through those mechanisms already in
   place with the RIRs.  For example, in the ARIN region, there are such
   mechanisms already defined in the ARIN NRPM section 8.3
   [section 8.3 - Transfers to Specified Recipients"">ARIN-NRPM-8.3].

3.4.  Impact on Allocations / RIR Inventory

   While making "shared space" available to the community, may or may
   not lessen the demand on the RIRs for allocations, it will help
   ensure that the address resources which remain in inventory are used
   most efficiently, maximizing the use of that inventory for services
   that require global routability.

   BENSON: note that I changed this to "may or may not" because I think
   it's arguable either way...  If an SP doesn't need globally unique
   space to continue numbering (with a CGN) then that might slow the
   rate of allocation.  On the other hand, unless RIRs police it, the
   SP's interest is aligned with continuing to make requests and "bank"
   them for later, so that wouldn't change the rate of allocation at
   all.

3.5.  Benefit of Standardization

   Standardizing on a single block will help the community develop
   standard ways of selecting, routing, filtering and managing shared
   space.  This task would be much more difficult or impractical for any
   of the alternative options.

   Standard internal routing policy and filtering can be applied
   uniformly inside network environments.  Additionally, exchange points
   between networks can have standard policies applied allowing
   operators to protect each other from CGN zone IPs leaking between
   networks.  This may not be possible with squat space since many
   operators will not divulge what space may be used and with Private
   [RFC1918] address space where each operator may only be able to free
   up certain portions of the space which are not likely to be
   consistent between networks.

3.6.  IPv6 Deployments

   Operators will need to grapple with the need to provide IPv4 based
   flow continuity to customers post exhaustion.  By removing the burden
   of operators needing to find adequate IPv4 address space to meet the
   needs that a shared transition space can fulfill, they can
   concentrate on the real task at hand: Deploying IPv6.

   Endless cycles can be avoided where operators squat, free up space



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   and/or segment networks in an effort to find valid IPv4 space.  The
   saved effort, time and cost can be re-directed to provided quality
   IPv6 connectivity therefore expiditing the removal of the overall
   need for IPv4 addresses and connectivity.


4.  Analysis of Detractors' Arguments

4.1.  It Breaks

4.1.1.  NAT is Bad

   NAT is understood to be less then optimal [RFC6269], especially when
   implemented as CGN [I-D.donley-nat444-impacts].  That said, it is a
   necessary technology for many networks and cannot be completely
   avoided.  Since the number of IPv4 internet endpoints will exceed the
   number of IPv4 addresses which are available for Internet
   connectivity, NATs are needed.

   While the authors agree that "NAT is bad", it must also be understood
   that shared transition space does not change the fundamental problems
   with NAT and so those problems will not be discussed at length here.

4.1.2.  Breaks Bad Host Assumptions

   The use of GUA space (non-RFC1918) does in some circumstances break
   some functions.  The most commonly cited function is 6to4.  Although
   6to4 can break, it's not commonly turned on by default. 6to4 can also
   be "repaired" in some instances when used behind a CGN (NAT66) or
   managed by the network operator.  Since the volume of impacted
   endpoints will be very low, operators can likely manage the disabling
   of 6to4 when needed.

4.1.3.  Potential Misuse as Private Space

   The value of a Shared Transition Space may be diminished if misused
   by end-sites as generic Private addresses.  Thus, the reservation
   must be clearly designated for use by SPs that are providing
   infrastructure as described herein.

   This is not a technical issue.  As with any technology, the
   opportunity exists for a misuse.  This however should not shroud the
   strong benefits of the shared address space option.  Many
   technologies in use today can be used correctly or misused.  This
   does not prevent the community from introducing those technologies
   since the good far outweighs the bad.

   As an example, the use of DiffServ [RFC2475] can result in punitive



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   measures for some hosts in a network while favouring others bad on
   illegitimate rules.  This however is not a good argument on why not
   to permit DiffServ.

4.2.  It's Not Needed

4.2.1.  Nobody Will Use It

   This argument is simply incorrect.  Post IPv4-exaustion, any SP that
   wishes to continue providing IPv4 connectivity will necessarily
   deploy network architectures and technologies that require such an
   address space.

   In absense of a designated Shared Transition Space, operators will
   use GUA space in essentially the same ways described in this memo,
   with or without IETF acknowledgement.  The industry needs to
   recognize this and work in the best interests of the "real customer".

4.2.2.  ISPs Are Not Actually Growing

   While customer growth for some ISPs has slowed, for many service
   providers new services are growing at a faster rate than has been
   anticipated.  Wireline voice customers for example require two-way
   communication paths to allow them to function properly.  IP enabled
   televisions is another example of devices that support video and
   voice services and require IP addresses.  In many cases the protocols
   that allow these devices to work have embedded IP addresses that do
   not work with NAT.  The only way to maintain these services, which in
   many cases are considered lifeline, is to provide them with an IP
   address that is unique with the service provider network.

   Likewise, growth continues to exist in some geographical regions.
   While some areas have slower growth, as a result of significant
   penetration of Internet access, there are still many areas with unmet
   needs, growing populations, or both.

4.2.3.  RIR IPv4 Inventory is Not Actually Exhausted

   With the IANA inventory essentially exhausted [NRO-IANA-exhaust] it
   is only a matter of time before each of the RIRs are unable to
   satisfy requests for IPv4 addresses.  [GIH-When] In fact, the APNIC
   has already allocated all but their final /8 of inventory
   [APNIC-final-slash8] and is no longer making allocations larger than
   a /22 prefix.  Each of the other RIRs is on a trajectory toward
   exhaustion in the near future.






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4.2.4.  ISP IPv4 Inventory is Not Actually Exhausted

   While some SPs have existing inventory that will outlast the RIR
   inventories, this is not universally true.  In fact, the distribution
   of IPv4 number resources amongst operators is highly variable (based
   on size, history, etc) and in the worst cases is already becoming
   problematic.

4.3.  Address Inventory

4.3.1.  Shared Transition Space Uses Up Address Inventory

   While true that the Shared Transition Space will consume some
   unallocated inventory, the impact is no greater than would be seen if
   individual SPs continue to request allocations of GUA for the
   scenarios described herein.  It is possible, rather, that the Shared
   Transition Space might alleviate some near-term demand on RIR
   inventories.  However, even if the RIR inventories are exhausted at
   the current rate, the reservation of a Shared Transition Space will
   enable continued deployment of IPv4 connectivity by SP networks - a
   clear benefit.

4.3.2.  /10 is not Enough

   There are many ISP networks that may require greater or lesser
   amounts of IPv4 number resources, as a Shared Transition Space.
   While a larger prefix (such as a /8) would allow for expanded
   applicability, to larger ISP networks, it is generally thought that a
   /10 will be adequate for a large number of network deployments.
   Likewise, a /10 seems to be appropriate given the current
   technological constraints and operational considerations of CGN
   deployment.  On the other hand, a smaller prefix might not be large
   enough to apply in many modern network deployments.  Thus, a /10
   prefix for Shared Transition Space is considered an appropriate
   compromise.

4.3.3.  It Won't Delay RIR Exhaustion

   It remains to be seen whether the reservation of a Shared Transition
   Space will delay the impending exhaustion of RIRs' IPv4 inventory.
   Certainly, the availability of this Shared Transition Space will
   satisfy a number of demands that would otherwise become requests for
   GUA resources.  However, whether this translates to an actual
   reduction in requests is up to the RIRs and requesting organizations.







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4.4.  IPv6 Arguments

4.4.1.  Use IPv6 Instead

   Although IPv6 is the strategic long term answer fro IPv4 address
   exhaustion, it does not immediately solve IPv4 connectivity
   requirements.  There is an entire eco-system which exists on the
   Internet which is not IPv6 ready at this time.  IPv4 flow continuity
   will be required for a long period of time.

   Many businesses have long procurement and fulfilment cycles which
   will need to be used to upgrade networks to support IPv6.  Also, the
   consumer (home) space is years away from being all IPv6 capable.
   Many homes are filled with IPv4 only consumer electronics, computers,
   TVs, accessories and other systems.

   There are still a number of products that are either not IPv6
   compliant, or for which the necessary criteria for being "IPv6
   compliant" is unclear or undefined.  Some examples include security
   products (IDS/IPS in particular), a large number of software
   applications (MySQL is one example), and there are still production
   systems (both inside companies and as products) being rolled out that
   are not IPv6 aware (until very recently, this included all Linksys
   routers).

   The whole Internet needs to get to IPv6 more or less at the same time
   in order to avoid significant deployment of transition technologies.
   This proposal may help delay some transition technology deployment
   while IPv6 deployments move ahead.  More IPv6 should mean less
   transition technology.

4.4.2.  Delay of IPv6 Deployment

   Although IPv6 is the strategic long term answer for IPv4 address
   exhaustion, it does not immediately solve IPv4 connectivity
   requirements.  There is an entire eco-system which exists on the
   Internet today and is not IPv6 ready at this time.  IPv4 flow
   continuity will be required for a long period of time.

   Many businesses have long procurement and fulfilment cycles which
   will need to be used to upgrade networks to support IPv6.  Also, the
   consumer (home) space is years away from being fully IPv6 capable.
   Many homes are filled with IPv4-only consumer electronics, computers,
   TVs, accessories and other systems.

   BENSON: Note: "cite arkkois drafts about operating in IPv6-only mode
   for evidence that this is not actually workable yet"




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4.5.  History

   The proposal for additional Private space in order to survive IPv6
   transition dates back to [I-D.hain-1918bis] in April 2004, and more
   recently as Shared Transition Space [I-D.shirasaki-isp-shared-addr]
   in June 2008 where a proposal to set aside "ISP Shared Space" has
   been made.  During discussion of the more recent proposals many of
   the salient points where commented on including challenges with
   RFC1918 in the ISP NAT Zone, Avoidance of IP Address Conflicts, and
   challenges with 240/4.

   This effort was followed up by
   [I-D.weil-opsawg-provider-address-space] in July 2010 which was re-
   worked in November 2010 as
   [I-D.weil-shared-transition-space-request].  The latter two efforts
   continued to point out the operators need for Shared Transition
   Space, with full acknowledgement that challenges may arise with
   NAT444 as per [I-D.donley-nat444-impacts].

   Most recently, following exhaution of the IANA's /8 pool
   [NRO-IANA-exhaust], this proposal has been discussed by various RIR
   policy participants.  As described herein, the body of ARIN policy
   development participants has recommended a Shared Address Space
   policy for adoption [ARIN-2011-5].

   This history has shown that operators and other industry contributors
   have identified the need for a Shared Transition Space assignment
   based on clearly identified reasons.  The previous work has also
   described the awareness of the challenges of this space, but points
   to this option as the most manageable and workable solution for IPv6
   transition space.


5.  ARIN Draft Policy 2011-5

5.1.  History

   The following is a brief history of ARIN Draft Policy 2011-5.

   o  ARIN-prop-127 - Shared Transition Space for IPv4 Address Extension
      [ARIN-prop-127]

      *  Proposal Originator: Chris Donley, CableLabs

      *  Date: 20 January 2011

      *  AC Shepherds: Stacy Hughes and Chris Morrow




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   o  ARIN-2011-5 - Formal introduction on PPML on 3 February 2011
      [ARIN-2011-5]

   o  ARIN XXVII - 12 April 2011 - San Juan, Puerto Rico - Participant
      Vote on 2011-5 [ARIN27.2011-5]

      *  Total Participants: 116

      *  In favor: 30

      *  Opposed: 15

   o  AC moves to Last Call - 13 April 2011 [ARIN-2011-5-AC]

   o  Last Call - 18 April through 2 May 2011 [ARIN-2011-5-LC]

   o  AC recommended adoption - 24 May 2011 [ARIN-2011-5-Rec]

      *  The motion carried via roll call with 7 in favor, 5 against,
         and 3 abstentions

5.2.  Policy Text

   Draft Policy ARIN-2011-5

   Shared Transition Space for IPv4 Address Extension

   Date: 20 January 2011

   Policy statement:

   Updates 4.10 of the NRPM:

   A second contiguous /10 IPv4 block will be reserved to facilitate
   IPv4 address extension.  This block will not be allocated or assigned
   to any single organization, but is to be shared by Service Providers
   for internal use for IPv4 address extension deployments until
   connected networks fully support IPv6.  Examples of such needs
   include: IPv4 addresses between home gateways and NAT444 translators.

   Rationale:

   The Internet community is rapidly consuming the remaining supply of
   unallocated IPv4 addresses.  During the transition period to IPv6, it
   is imperative that Service Providers maintain IPv4 service for
   devices and networks that are currently incapable of upgrading to
   IPv6.  Consumers must be able to reach the largely IPv4 Internet
   after exhaustion.  Without a means to share addresses, people or



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   organizations who gain Internet access for the first time, or those
   who switch providers, or move to another area, will be unable to
   reach the IPv4 Internet.

   Further, many CPE router devices used to provide residential or
   small-medium business services have been optimized for IPv4
   operation, and typically require replacement in order to fully
   support the transition to IPv6 (either natively or via one of many
   transition technologies).  In addition, various consumer devices
   including IP-enabled televisions, gaming consoles, medical and family
   monitoring devices, etc. are IPv4-only, and cannot be upgraded.
   While these will eventually be replaced with dual-stack or IPv6
   capable devices, this transition will take many years.  As these are
   typically consumer-owned devices, service providers do not have
   control over the speed of their replacement cycle.  However,
   consumers have an expectation that they will continue to receive IPv4
   service, and that such devices will continue to have IPv4 Internet
   connectivity after the IPv4 pool is exhausted, even if the customer
   contracts for new service with a new provider.

   Until such customers replace their Home Gateways and all IPv4-only
   devices with IPv6-capable devices, Service Providers will be required
   to continue to offer IPv4 services through the use of an IPv4 address
   sharing technology such as NAT444.  A recent study showed that there
   is no part of RFC1918 space which would not overlap with some IPv4
   gateways, and therefore to prevent address conflicts, new address
   space is needed.

   Service providers are currently presented with three options for
   obtaining sufficient IPv4 address space for NAT444/IPv4 extension
   deployments: (1) Request allocations under the NRPM; (2) share
   address space with other providers (this proposal); or (3) use
   address space allocated to another entity (i.e. 'squat').  Of the
   three options, option 2 (this proposal) is preferable, as it will
   minimize the number of addresses used for IPv4 extension deployments
   while preserving the authority of IANA and RIRs.

   Timetable for implementation: immediately


6.  Acknowledgements

   The authors would like to thank Jeffrey Finkelstein for his
   significant contributions.

   The authors would also like to thank Chris Donley, Wes George, and
   Richard Von Scherr for their review, comments, and support.




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7.  IANA Considerations

   This memo includes no request to IANA.


8.  Security Considerations

   This memo makes reference to a number of deployment scenarios that
   have unique security considerations, and the reader is advised to
   investigate these independently.

   While this memo does not introduce any specific technical issues that
   may be subject to detailed security considerations, it does
   reccommend the reservation of a new IPv4 address space that might
   have unique properties when deployed.  As such, all implementors of
   this Shared Transition Space are encouraged to consider carefully the
   best practices associated with the use of this space, including
   considerations relating to filtering, routing, etc.


9.  Informative References

   [APNIC-final-slash8]
              APNIC, "APNIC IPv4 Address Pool Reaches Final /8",
              Apr 2011,
              <http://www.apnic.net/publications/news/2011/final-8>.

   [ARIN-2011-5]
              ARIN, "Draft Policy ARIN-2011-5: Shared Transition Space
              for IPv4 Address Extension", 2011,
              <https://www.arin.net/policy/proposals/2011_5.html>.

   [ARIN-2011-5-AC]
              ARIN, "Minutes: Meeting of the ARIN Advisory Committee -
              13 Apr 2011", Apr 2011,
              <https://www.arin.net/about_us/ac/ac2011_0413.html>.

   [ARIN-2011-5-LC]
              ARIN, "ARIN-2011-5: Shared Transition Space for IPv4
              Address Extension - Last Call", Apr 2011, <http://
              lists.arin.net/pipermail/arin-ppml/2011-April/
              020808.html>.

   [ARIN-2011-5-Rec]
              ARIN, "Advisory Council Meeting Results - May 2011",
              May 2011, <http://lists.arin.net/pipermail/arin-ppml/
              2011-May/022331.html>.




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   [ARIN-NRPM-8.3]
              ARIN, "ARIN Number Resource Policy Manual, section 8.3 -
              Transfers to Specified Recipients", Jul 2011,
              <https://www.arin.net/policy/nrpm.html#eight3>.

   [ARIN-prop-127]
              Donley, C., "ARIN-prop-127: Shared Transition Space for
              IPv4 Address Extension", Jan 2011, <http://lists.arin.net/
              pipermail/arin-ppml/2011-January/019278.html>.

   [ARIN27.2011-5]
              ARIN, "ARIN XXVII Meeting - Participant Vote on 2011-5",
              Apr 2011, <https://www.arin.net/participate/meetings/
              reports/ARIN_XXVII/ppm2_transcript.html#anchor_6>.

   [GIH-When]
              "When?", Sep 2010,
              <http://www.potaroo.net/ispcol/2010-10/when.html>.

   [I-D.azinger-additional-private-ipv4-space-issues]
              Azinger, M. and L. Vegoda, "Additional Private IPv4 Space
              Issues",
              draft-azinger-additional-private-ipv4-space-issues-04
              (work in progress), April 2010.

   [I-D.donley-nat444-impacts]
              Donley, C., Howard, L., Kuarsingh, V., Chandrasekaran, A.,
              and V. Ganti, "Assessing the Impact of NAT444 on Network
              Applications", draft-donley-nat444-impacts-01 (work in
              progress), October 2010.

   [I-D.fuller-240space]
              Fuller, V., "Reclassifying 240/4 as usable unicast address
              space", draft-fuller-240space-02 (work in progress),
              March 2008.

   [I-D.hain-1918bis]
              Hain, T., "Expanded Address Allocation for Private
              Internets", draft-hain-1918bis-01 (work in progress),
              January 2005.

   [I-D.ietf-behave-lsn-requirements]
              Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
              and H. Ashida, "Common requirements for IP address sharing
              schemes", draft-ietf-behave-lsn-requirements-01 (work in
              progress), March 2011.

   [I-D.shirasaki-isp-shared-addr]



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              Yamagata, I., Miyakawa, S., Nakagawa, A., Yamaguchi, J.,
              and H. Ashida, "ISP Shared Address",
              draft-shirasaki-isp-shared-addr-05 (work in progress),
              September 2010.

   [I-D.shirasaki-nat444-isp-shared-addr]
              Shirasaki, Y., Miyakawa, S., Nakagawa, A., Yamaguchi, J.,
              and H. Ashida, "NAT444 addressing models",
              draft-shirasaki-nat444-isp-shared-addr-05 (work in
              progress), January 2011.

   [I-D.weil-opsawg-provider-address-space]
              Weil, J., Kuarsingh, V., and C. Donley, "IANA Reserved
              IPv4 Prefix for IPv6 Transition",
              draft-weil-opsawg-provider-address-space-02 (work in
              progress), September 2010.

   [I-D.weil-shared-transition-space-request]
              Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and
              M. Azinger, "IANA Reserved IPv4 Prefix for Shared
              Transition Space",
              draft-weil-shared-transition-space-request-01 (work in
              progress), November 2010.

   [I-D.wilson-class-e]
              Wilson, P., Michaelson, G., and G. Huston, "Redesignation
              of 240/4 from "Future Use" to "Private Use"",
              draft-wilson-class-e-02 (work in progress),
              September 2008.

   [IAB-response]
              IAB, "IAB responds to ARIN request for guidance regarding
              Draft Policy ARIN-2011-5", Jun 2011, <http://www.iab.org/
              2011/06/
              iab-responds-to-arin-request-for-guidance-regarding-draft-
              policy-arin-2011-5/>.

   [NRO-IANA-exhaust]
              NRO, "Free Pool of IPv4 Address Space Depleted", Feb 2011,
              <http://www.nro.net/news/ipv4-free-pool-depleted>.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, December 1998.



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   [RFC2860]  Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
              Understanding Concerning the Technical Work of the
              Internet Assigned Numbers Authority", RFC 2860, June 2000.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006.

   [RFC6269]  Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
              Roberts, "Issues with IP Address Sharing", RFC 6269,
              June 2011.

   [v6ops-msg06187]
              WIDE, "Re: [v6ops] IETF 79 Meeting minutes - Draft",
              Nov 2010, <http://www.ietf.org/mail-archive/web/v6ops/
              current/msg06187.html>.


Authors' Addresses

   Stan Barber
   Cox Communications

   Email: stan.barber2@cox.com


   Owen Delong
   Hurricane Electric

   Email: owen@delong.com


   Chris Grundemann
   CableLabs

   Email: c.grundemann@cablelabs.com


   Victor Kuarsingh
   Rogers Communications

   Email: victor.kuarsingh@rci.rogers.com


   Benson Schliesser
   Cisco Systems

   Email: bschlies@cisco.com




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