Internet DRAFT - draft-bdgks-arin-shared-transition-space
draft-bdgks-arin-shared-transition-space
Network Working Group S. Barber
Internet-Draft Cox Communications
Intended status: Informational O. Delong
Expires: March 22, 2012 Hurricane Electric
C. Grundemann
CableLabs
V. Kuarsingh
Rogers Communications
B. Schliesser
Cisco Systems
September 19, 2011
ARIN Draft Policy 2011-5: Shared Transition Space
draft-bdgks-arin-shared-transition-space-03
Abstract
This memo discusses the applicability 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
come to consensus within the ARIN policy development community where
it was recommended for adoption as Draft Policy 2011-5.
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 22, 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
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Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Intended Use of Shared Transition Space . . . . . . . . . 5
2.1.1. CGN . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.2. SP Services & Infrastructure . . . . . . . . . . . . . 5
2.1.3. Note of Caution . . . . . . . . . . . . . . . . . . . 5
2.2. Alternatives . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1. Global Unicast Addresses . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . 10
3.3.2. Return or Transfer . . . . . . . . . . . . . . . . . . 10
3.4. Impact on Allocations of RIR Inventory . . . . . . . . . . 10
3.5. Benefit of Standardization . . . . . . . . . . . . . . . . 10
3.6. IPv6 Deployments . . . . . . . . . . . . . . . . . . . . . 11
4. Analysis of Detractors' Arguments . . . . . . . . . . . . . . 11
4.1. It Breaks . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.1. NAT is Bad . . . . . . . . . . . . . . . . . . . . . . 11
4.1.2. Breaks Assumptions about Address Scope . . . . . . . . 11
4.1.2.1. 6to4 . . . . . . . . . . . . . . . . . . . . . . . 11
4.1.3. Potential Misuse as Private Space . . . . . . . . . . 12
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 . . . . . 13
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 . . . . . . . . . . . . . . . . . . 14
4.4. IPv6 Arguments . . . . . . . . . . . . . . . . . . . . . . 14
4.4.1. Use IPv6 Instead . . . . . . . . . . . . . . . . . . . 14
4.4.2. Delay of IPv6 Deployment . . . . . . . . . . . . . . . 14
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5. ARIN Draft Policy 2011-5 . . . . . . . . . . . . . . . . . . . 14
5.1. History . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1.1. Shared Address Space . . . . . . . . . . . . . . . . . 15
5.1.2. Proposal . . . . . . . . . . . . . . . . . . . . . . . 15
5.2. Policy Text . . . . . . . . . . . . . . . . . . . . . . . 17
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. Informative References . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
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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
Global Unicast 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]
reached consensus and was recommended by the ARIN Advisory Council
for approval by the ARIN Board of Trustees.
Following the community's recommendation of [ARIN-2011-5] the ARIN
Board requested clarification from the IAB with regard to
responsibilities outlined in [RFC2860]. The ARIN Board received a
response in [IAB-response] indicating that the IETF holds
responsibility for the reservation of specialized address blocks.
Thus, the ARIN Board believes that it is not within ARIN's authority
to unilaterally make specialized allocations of the sort proposed in
Draft Policy 2011-5. [PPML-022778]
This memo explains the intended use and discusses the merits and
drawbacks of using Shared Transition Space.
2. Applicability
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2.1. Intended Use of Shared Transition Space
The Shared Transition Space is intended for use by service providers
and should not be thought of as additional RFC1918 space. There are
a number of specific use-cases for the Shared Transition Space. This
section discusses the primary scenarios envisioned at the time of
this writing. Equipment vendors and non-ISP network operators should
be aware that using the Shared Transition Space outside of its
intended scope may result in unpredictable behavior.
2.1.1. CGN
The primary use-case for the Shared Transition Space will be
deployment in CGN [I-D.ietf-behave-lsn-requirements] internal
networks. A key benefit of CGN is the ability to share a smaller
number of Global Unicast Addresses (GUA) amongst a larger number of
end-sites.
In one CGN deployment scenario sometimes referred to as NAT444
[I-D.shirasaki-nat444], 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. [I-D.shirasaki-nat444-isp-shared-addr]
2.1.2. SP Services & Infrastructure
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. Where these services
are accessed by customers who have their own IPv4-only equipment, use
of the Shared Transition Space will reduce or eliminate the need for
NAT. Similarly, those infrastructure elements which touch IPv4-only
customer-managed equipment could also be numbered from the Shared
Transition Space. In cases where the provider manages both
endpoints, IPv6 should be used.
2.1.3. Note of Caution
In any case, care must be taken to ensure the Shared Transition Space
is not used in scenarios where routing may be ambiguous. For
instance, when multiple provider networks may be simultaneously
reachable the use of Shared Transition Space might result in address
conflicts etc. Conversely, operators may choose to allow (not
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filter) ICMP messages from the Shared Transition Space in order to
enable Path MTU Discovery etc. This topic requires further
investigation so that best practices may be developed.
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, [RFC6319] for a discussion of alternatives and potential
issues. This section outlines these possible alternatives and
briefly discusses their applicability.
2.2.1. Global Unicast Addresses
Every discussion of the Shared Transition Space begins with an
assumption that Global Unicast 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. Private [RFC1918] address space is not generally
intended to be used for purposes which cross administrative domains.
Further, these recommendations involve use of the Shared Transition
Space to provide services in one administrative domain to leaf
networks which are generally single-homed to the serving
administrative domain. This is also a significant difference from
the intent of Private [RFC1918] address space.
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
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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. defined private space is not generally
intended to be used for purposes which cross administrative domains.
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 behaviors on such hosts which may not be
desirable when the endpoint is actually connected to the Internet.
There are often behavioral 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 behaviors 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. For
example, [CISCO] states that: "No addresses are allowed with the
highest-order bits set to 1111." For the scenarios described herein,
it should be noted that this alternative would create additional SP
dependencies on customer selected CPE support for Class E addressing.
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
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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.
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. Indeed, various RIRs attempt to discover
and "recycle" abandoned or unused IPv4 address space, making it more
likely that such conflicts will be experienced in time. As such,
this alternative is to be discouraged with prejudice.
It is important to note that there are no behavioral advantages to
using "squat space" over using assigned "shared space". Both options
subject the CPE to the same general behaviors (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 behavioral
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
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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
behavioral 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.
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 addressing and/or connectivity post exhaustion.
For environments where CGN in a NAT444 scenario is necessary,
addresses from this space can be used to provide addressing for the
network between the CGN device(s) and CPE which will enable IPv4 flow
continuity for customers using these services. In other
circumstances, the shared transition space allows SPs to number
devices in the network which do not require global reachability
without the need for fulfillment thorough an RIR.
3.2. Delayed Need for CGN Deployment
If operators are required to use their individually allocated GUA
where "shared space" would have applied, e.g. for internal services,
they will face exhaustion sooner and thus be forced to deploy CGN
sooner as well. Operators may be able to postpone the 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.
Further, without this shared transition space, some service providers
may be forced to reclaim GUA from existing customers in order to
deploy CGN and address the required infrastructure. Having this
transition space will enable deployment of CGN where it is required,
in a manner that is less disruptive and with impact to fewer
customers.
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
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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 is not deploying CGN and doesn't need the
recovered addresses, they can be made available to others that do
need them for connectivity to the public IPv4 Internet. This may be
through voluntary return to the RIR, or through transfer to another
network operator. For example, in the ARIN region, there are
transfer mechanisms defined in the ARIN NRPM 8.3 [ARIN-NRPM-8.3].
3.4. Impact on Allocations of RIR Inventory
While making Shared Transition 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 Unicast Addresses.
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.
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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.
4. Analysis of Detractors' Arguments
4.1. It Breaks
4.1.1. NAT is Bad
NAT is understood to be less than 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
motivations or issues with NAT and so those problems will not be
discussed at length here.
4.1.2. Breaks Assumptions about Address Scope
Some host or CPE functions incorrectly assume global reachability
based on the type of address that is configured, potentially causing
issues when deployed in a NAT444 scenario. Whether an operator uses
this proposed Shared Transition Space or some other GUA space (e.g.
through squatting or reuse), the net effect on hosts and/or CPE
making such assumptions about reachability is identical. Conversely,
with an identified Shared Transition Space hosts that make these
mistaken assumptions can be modified to treat the identified block as
having restricted reachability semantics. This would not be possible
(or at least not nearly as easy) with the other solutions.
4.1.2.1. 6to4
Although 6to4 can break in CGN scenarios using the Shared Transition
Space, recent guidance suggests that it should be turned off by
default. [RFC6343] [I-D.ietf-v6ops-6to4-to-historic] Indeed, recent
versions of operating systems de-preference 6to4 addresses as
described in [I-D.ietf-6man-rfc3484-revise], mitigating effects from
incorrect 6to4 instantiation behind a firewall that obstructs its
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function.
Since the volume of impacted endpoints will be low, operators can
likely manage the disabling of 6to4 when needed. More fundamentally,
broken 6to4 should not be an issue if service providers deploy (and
user equipment supports) native IPv6 connectivity.
4.1.3. Potential Misuse as Private Space
Shared Transition Space is intended to be used solely by Service
Providers for IPv4 to IPv6 transition purposes.
[I-D.weil-shared-transition-space-request] The value of a Shared
Transition Space may be diminished if commonly 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.
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. Thus, 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 or RIR acknowledgement.
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. 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 within 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.
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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.
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 this Shared Transition Space will remove a block of
global unicast IPv4 addresses from the free pool, it must also be
noted that the use of the same "shared space" repeatedly across
multiple networks will very likely increase the available pool of
unique IPv4 addresses through operational efficiency. For example,
if just two operators use their own GUA /10, the Internet community
effectively loses a /9 of unique space while if both operators use
the same "shared" /10, the Internet community loses that single /10.
This benefit becomes more significant as more operators use the
Shared Transition Space.
It remains to be seen whether the reservation of a Shared Transition
Space will actually 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. Regardless of the allocation of Shared Transition
Space, RIR IPv4 exhaustion may happen at roughly the same time.
However, as noted above, Shared Transition Space does provide the
opportunity for more efficient use of the remaining RIR IPv4
addresses. Additionally, the reservation of a Shared Transition
Space will enable continued deployment of IPv4 connectivity by SP
networks beyond the free pool depletion horizon; another clear
benefit.
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4.3.2. /10 is not Enough
Although previous requests for Shared Transition Space asked for a
full /8, it has been determined by many operators that a /10 will in
fact be sufficient. A /10 provides for roughly 4 million hosts and
although many of the largest SPs have subscriber counts in the tens
of millions, none will be placing all of their subscribers behind a
single CGN. In the event that a /10 does not provide enough
addresses for an operators entire CGN deployment, it could be re-used
multiple times in distinct "NAT zones" or regions.
4.4. IPv6 Arguments
4.4.1. Use IPv6 Instead
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
[I-D.arkko-ipv6-only-experience]. IPv4 flow continuity will be
required for at least several years.
Many businesses have long procurement and fulfillment 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, a large number of software applications, and there are
still production systems (both inside companies and as products)
being rolled out that are not IPv6 aware.
4.4.2. Delay of IPv6 Deployment
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.
5. ARIN Draft Policy 2011-5
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5.1. History
5.1.1. Shared Address Space
Proposals for additional Private space date back at least to
[I-D.hain-1918bis] in April 2004. Some of these proposals and
surrounding discussion may have considered similar use-cases as
described herein. However, they were fundamentally intended to
increase the size of the [RFC1918] pool, whereas a defining
characteristic of Shared Transition Space is that it is distinctly
not part of the Private [RFC1918] address pool.
Rather, the Shared Transition Space is reserved for more narrow
deployment scenarios, specifically for use by SPs to meet the needs
of ongoing IPv4 connectivity during the period of IPv6 transition.
This key feature emerged in more recent proposals such as
[I-D.shirasaki-isp-shared-addr] in June 2008 where a proposal to set
aside "ISP Shared Space" was made. During discussion of these more
recent proposals, many of the salient points where commented upon,
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]. These latter 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] and that such space does
not reduce the need for IPv6 deployment.
Most recently, following exhaustion of the IANA's /8 pool
[NRO-IANA-exhaust], this proposal has been discussed by various RIR
policy development participants. As described herein, the body of
ARIN policy development participants has reached consensus and
recommended a Shared Address Space policy for adoption [ARIN-2011-5].
This history shows that operators and other industry contributors
have consistently identified the need for a Shared Transition Space
assignment, based on pragmatic operational needs. 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.
5.1.2. Proposal
The following is a brief history of the proposal for Shared Address
Space within ARIN, ultimately resulting in the recommendation of ARIN
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Draft Policy 2011-5 [ARIN-2011-5].
In January 2011, a policy was proposed to the ARIN policy development
community called ARIN-prop-127: Shared Transition Space for IPv4
Address Extension [ARIN-prop-127]. This policy proposal would
reserve an IPv4 /10 prefix by ARIN, to be shared by any Service
Providers who wish to use it with no further registration actions
required.
After generating much discussion (over 100 posts) on the ARIN Public
Policy Mailing List (PPML), the ARIN Advisory Council (AC) accepted
the proposal as Draft Policy 2011-5 [ARIN-AC-28Jan2011], formally
announced on PPML 3 February 2011 [ARIN-2011-5-AC].
On 14 February 2011, ARIN staff made the following statement with
regard to 2011-5: "In keeping with the spirit of RFC 2860 with
respect to the assignment of specialized address blocks, ARIN Staff
will consult with the IANA and the IAB regarding implementation of
this draft policy." [ARIN-2011-5-Staff]
In the ensuing PPML discussion there was a roughly two to one ratio
of those clearly in support of the policy versus those clearly
against. ARIN Draft Policy 2011-5 was then discussed at the ARIN
XXVII public policy meeting on 12 April 2011. Following the
discussion, there was a straw poll of the room. With a total number
of people in the meeting room and remote of 116; in favor of it were
30 and against it were 15. [ARIN27.2011-5]
Seeing an obvious need in the service provider community, the AC
voted to send the Draft Policy to last call [ARIN-AC-13Apr2011] for
final comments 18 April through 2 May 2011. [ARIN-2011-5-LC]
Following a strong show of support from the operator community during
last call, the AC voted [ARIN-AC-19May2011] to recommend adoption of
2011-5 to the ARIN Board of Trustees with a vote of 10 in favor and 2
abstentions. [ARIN-2011-5-Rec]
Following this recommendation, ARIN staff consulted with the IAB and
IANA as committed. The IAB response [IAB-response] stated, in short,
that they believed the adoption of [ARIN-2011-5] was in conflict with
the provisions in [RFC2860] and requested that the community re-
review the operational and technical merits of shared transition
space in the IETF. That process is now underway, with this draft an
attempt at more fully analyzing said operational and technical
merits.
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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
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
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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 the following individuals for their
contributions: John Curran, David Farmer, Jeffrey Finkelstein,
William Herrin, and Dan Wing.
The authors would also like to thank the following people for their
review, comments, and support: Gary Buhrmaster, Chris Donley, Wes
George, Chris Metz, Richard Von Scherr, and Lane Wigley.
7. IANA Considerations
Upon notification by the IAB that that an address reservation should
be made, ARIN is willing to proceed with the implementation of its
Draft Policy 2011-5 which would result in ARIN reserving IPv4 /10
block for shared transition. The IANA is to record the allocation of
the IPv4 address block for this purpose. Alternatively, the IAB may
direct the IANA to request return of sufficient address space from
ARIN's available IPv4 number resource pool to allow the IANA to
perform this reservation directly.
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.
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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, "Message to ARIN-PPML, announcing selection of ARIN-
prop-127 for Discussion as Draft Policy 2011-5", Feb 2011,
<http://lists.arin.net/pipermail/arin-ppml/2011-February/
019579.html>.
[ARIN-2011-5-LC]
ARIN, "Message to ARIN-PPML, announcing Last Call for
Draft Policy 2011-5", Apr 2011, <http://lists.arin.net/
pipermail/arin-ppml/2011-April/020808.html>.
[ARIN-2011-5-Rec]
ARIN, "Message to ARIN-PPML, announcing Advisory Council
meeting results Recommending 2011-5 for Board Approval",
May 2011, <http://lists.arin.net/pipermail/arin-ppml/
2011-May/022331.html>.
[ARIN-2011-5-Staff]
ARIN, "Message to ARIN-PPML, providing additional ARIN
Staff Assessment of Draft Policy 2011-5", Feb 2011, <http:
//lists.arin.net/pipermail/arin-ppml/2011-February/
019805.html>.
[ARIN-AC-13Apr2011]
ARIN, "Minutes: Meeting of the ARIN Advisory Committee -
13 Apr 2011", Apr 2011,
<https://www.arin.net/about_us/ac/ac2011_0413.html>.
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[ARIN-AC-19May2011]
ARIN, "Minutes: Meeting of the ARIN Advisory Committee -
19 May 2011", May 2011,
<https://www.arin.net/about_us/ac/ac2011_0519.html>.
[ARIN-AC-28Jan2011]
ARIN, "Minutes: Meeting of the ARIN Advisory Committee -
28 Jan 2011", Jan 2011,
<https://www.arin.net/about_us/ac/ac2011_0128.html>.
[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>.
[CISCO] Cisco, "TCP/IP Overview: Class E Addresses", <http://
www.cisco.com/univercd/cc/td/doc/product/rtrmgmt/cwhubs/
starvwug/83428.htm#xtocid74886>.
[GIH-When]
Huston, G., "When?", Sep 2010,
<http://www.potaroo.net/ispcol/2010-10/when.html>.
[I-D.arkko-ipv6-only-experience]
Arkko, J. and A. Keranen, "Experiences from an IPv6-Only
Network", draft-arkko-ipv6-only-experience-03 (work in
progress), April 2011.
[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.
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[I-D.hain-1918bis]
Hain, T., "Expanded Address Allocation for Private
Internets", draft-hain-1918bis-01 (work in progress),
January 2005, <http://www.ietf.org/internet-drafts/
draft-hain-1918bis-01.txt>.
[I-D.ietf-6man-rfc3484-revise]
Matsumoto, A., Kato, J., Fujisaki, T., and T. Chown,
"Update to RFC 3484 Default Address Selection for IPv6",
draft-ietf-6man-rfc3484-revise-04 (work in progress),
July 2011.
[I-D.ietf-behave-lsn-requirements]
Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
and H. Ashida, "Common requirements for Carrier Grade NAT
(CGN)", draft-ietf-behave-lsn-requirements-03 (work in
progress), August 2011.
[I-D.ietf-v6ops-6to4-to-historic]
Troan, O., "Request to move Connection of IPv6 Domains via
IPv4 Clouds (6to4) to Historic status",
draft-ietf-v6ops-6to4-to-historic-05 (work in progress),
June 2011.
[I-D.shirasaki-isp-shared-addr]
Yamagata, I., Miyakawa, S., Nakagawa, A., Yamaguchi, J.,
and H. Ashida, "ISP Shared Address",
draft-shirasaki-isp-shared-addr-06 (work in progress),
July 2011.
[I-D.shirasaki-nat444]
Yamagata, I., Shirasaki, Y., Nakagawa, A., Yamaguchi, J.,
and H. Ashida, "NAT444", draft-shirasaki-nat444-04 (work
in progress), July 2011.
[I-D.shirasaki-nat444-isp-shared-addr]
Yamaguchi, J., Shirasaki, Y., Miyakawa, S., Nakagawa, A.,
and H. Ashida, "NAT444 addressing models",
draft-shirasaki-nat444-isp-shared-addr-06 (work in
progress), July 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]
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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-03 (work in
progress), August 2011.
[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>.
[PPML-022778]
"Message to ARIN-PPML, indicating the Board's disposition
toward 2011-5", July 2011, <http://lists.arin.net/
pipermail/arin-ppml/2011-July/022778.html>.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[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.
[RFC6319] Azinger, M. and L. Vegoda, "Issues Associated with
Designating Additional Private IPv4 Address Space",
RFC 6319, July 2011.
[RFC6343] Carpenter, B., "Advisory Guidelines for 6to4 Deployment",
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RFC 6343, August 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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