Internet DRAFT - draft-ietf-v6ops-v6-aaaa-whitelisting-implications
draft-ietf-v6ops-v6-aaaa-whitelisting-implications
IPv6 Operations J. Livingood
Internet-Draft Comcast
Intended status: Informational February 27, 2012
Expires: August 30, 2012
Considerations for Transitioning Content to IPv6
draft-ietf-v6ops-v6-aaaa-whitelisting-implications-11
Abstract
This document describes considerations for the transition of end user
content on the Internet to IPv6. While this is tailored to address
end user content, which is typically web-based, many aspects of this
document may be more broadly applicable to the transition to IPv6 of
other applications and services. This document explores the
challenges involved in the transition to IPv6, potential migration
tactics, possible migration phases, and other considerations. The
audience for this document is the Internet community generally,
particularly IPv6 implementers.
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
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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 August 30, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Challenges When Transitioning Content to IPv6 . . . . . . . . 4
2.1. IPv6-Related Impairment . . . . . . . . . . . . . . . . . 5
2.2. Operational Maturity Concerns . . . . . . . . . . . . . . 5
2.3. Volume-Based Concerns . . . . . . . . . . . . . . . . . . 5
3. IPv6 Adoption Implications . . . . . . . . . . . . . . . . . . 6
4. Potential Migration Tactics . . . . . . . . . . . . . . . . . 6
4.1. Solve Current End User IPv6 Impairments . . . . . . . . . 7
4.2. Use IPv6-Specicic Names . . . . . . . . . . . . . . . . . 7
4.3. Implement DNS Resolver Whitelisting . . . . . . . . . . . 8
4.3.1. How DNS Resolver Whitelisting Works . . . . . . . . . 10
4.3.2. Similarities to Content Delivery Networks and
Global Server Load Balancing . . . . . . . . . . . . . 15
4.3.3. Similarities to DNS Load Balancing . . . . . . . . . . 15
4.3.4. Similarities to Split DNS . . . . . . . . . . . . . . 15
4.3.5. Related Considerations . . . . . . . . . . . . . . . . 16
4.4. Implement DNS Blacklisting . . . . . . . . . . . . . . . . 17
4.5. Transition Directly to Native Dual Stack . . . . . . . . . 18
5. Potential Implementation Phases . . . . . . . . . . . . . . . 19
5.1. No Access to IPv6 Content . . . . . . . . . . . . . . . . 19
5.2. Using IPv6-Specific Names . . . . . . . . . . . . . . . . 19
5.3. Deploying DNS Resolver Whitelisting Using Manual
Processes . . . . . . . . . . . . . . . . . . . . . . . . 19
5.4. Deploying DNS Resolver Whitelisting Using Automated
Processes . . . . . . . . . . . . . . . . . . . . . . . . 19
5.5. Turning Off DNS Resolver Whitelisting . . . . . . . . . . 19
5.6. Deploying DNS Blacklisting . . . . . . . . . . . . . . . . 20
5.7. Fully Dual-Stack Content . . . . . . . . . . . . . . . . . 20
6. Other Considerations . . . . . . . . . . . . . . . . . . . . . 20
6.1. Security Considerations . . . . . . . . . . . . . . . . . 20
6.2. Privacy Considerations . . . . . . . . . . . . . . . . . . 21
6.3. Considerations with Poor IPv4 and Good IPv6 Transport . . 22
6.4. IANA Considerations . . . . . . . . . . . . . . . . . . . 23
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 23
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1. Normative References . . . . . . . . . . . . . . . . . . . 25
9.2. Informative References . . . . . . . . . . . . . . . . . . 26
Appendix A. Document Change Log . . . . . . . . . . . . . . . . . 28
Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 31
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Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 31
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1. Introduction
This document describes considerations for the transition of end user
content on the Internet to IPv6. While this is tailored to address
end user content, which is typically web-based, many aspects of this
document may be more broadly applicable to the transition to IPv6 of
other applications and services. The issues explored herein will be
of particular interest to major web content sites (sometimes
described hereinafter as "high-service-level domains"), which have
specific and unique concerns relating to maintaining a high-quality
user experience for all of their users during their transition to
IPv6. This document explores the challenges involved in the
transition to IPv6, potential migration tactics, possible migration
phases, and other considerations. Some sections of this document
also include information about the potential implications of various
migration tactics or phased approaches to the transition to IPv6.
2. Challenges When Transitioning Content to IPv6
The goal in transitioning content to IPv6 is to make that content
natively dual-stack enabled, which provides native access to all end
users via both IPv4 and IPv6. However, there are technical and
operational challenges in being able to transition smoothly for all
end users, which has led to the development of a variety of migration
tactics. A first step in understanding various migration tactics is
to first outline the challenges involved in moving content to IPv6.
Implementers of these various migration tactics are attempting to
protect users of their services from having a negative experience
(poor performance) when they receive DNS responses containing AAAA
resource records or when attempting to use IPv6 transport. There are
two main concerns which pertain to this practice; one of which is
IPv6-related impairment and the other which is the maturity or
stability of IPv6 transport (and associated network operations) for
high-service-level domains. Both can negatively affect the
experience of end users.
Not all domains may face the same challenges in transitioning content
to IPv6, since the user base of each domain, traffic sources, traffic
volumes, and other factors obviously will vary between domains. As a
result, while some domains have used an IPv6 migration tactic, others
have run brief IPv6 experiments and then decided to simply turn on
IPv6 for the domain without further delay and without using any
specialized IPv6 migration tactics [Heise]. Each domain should
therefore consider its specific situation when formulating a plan to
move to IPv6; there is not one approach that will work for every
domain.
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2.1. IPv6-Related Impairment
Some implementers have observed that when they added AAAA resource
records to their authoritative DNS servers in order to support IPv6
access to their content that a small fraction of end users had slow
or otherwise impaired access to a given web site with both AAAA and A
resource records. The fraction of users with such impaired access
has been estimated to be as high as 0.078% of total Internet users
[IETF-77-DNSOP] [NW-Article-DNSOP] [IPv6-Growth] [IPv6-Brokenness].
While it is outside the scope of this document to explore the various
reasons why a particular user's system (host) may have impaired IPv6
access, and the potential solutions [I-D.ietf-v6ops-happy-eyeballs]
[RFC6343], for the users who experience this impairment it has a very
real performance impact. It would impact access to all or most dual
stack services to which the user attempts to connect. This negative
end user experience can range from somewhat slower than usual access
(as compared to native IPv4-based access), to extremely slow access,
to no access to the domain's resources whatsoever. In essence,
whether the end user even has an IPv6 address or not, merely by
receiving a AAAA record response the user either cannot access a
Fully Qualified Domain Name (FQDN, representing a service or resource
sought) or it is so slow that the user gives up and assumes the
destination is unreachable.
2.2. Operational Maturity Concerns
Some implementers have discovered that network operations, operations
support and business support systems, and other operational processes
and procedures are less mature for IPv6 as compared to IPv4, since
IPv6 has not heretofore been pervasively deployed. This operational
immaturity may be observed not just within the network of a given
domain but also in any directly or indirectly interconnected
networks. As a result, many domains consider it prudent to undertake
any network changes which will cause traffic to shift to IPv6
gradually in order to provide time and experience for IPv6 operations
and network practices mature.
2.3. Volume-Based Concerns
While Section 2.2 pertains to risks due to immaturity in operations,
a related concern is that some technical issues may not become
apparent until some moderate to high volume of traffic is sent via
IPv6 to and from a domain. As above, this may be the case not just
within the network of that domain but also for any directly or
indirectly interconnected networks. Furthermore, compared to domains
with small to moderate traffic volumes, whether by the count of end
users or count of bytes transferred, high-traffic domains receive
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such a level of usage that it is prudent to undertake any network
changes gradually and in a manner which minimizes the risk of
disruption. One can imagine that for one of the top ten sites
globally, for example, the idea of suddenly turning on a significant
amount of IPv6 traffic is quite daunting and would carry a relatively
high risk of network and/or other disruptions.
3. IPv6 Adoption Implications
It is important that the challenges in transitioning content to IPv6
noted in Section 2 are addressed, especially for high-service-level
domains. Some high-service-level domains may find the prospect of
transitioning to IPv6 extremely daunting without having some ability
to address these challenges and to incrementally control their
transition to IPv6. Lacking such controls, some domains may choose
to substantially delay their transition to IPv6. A substantial delay
in content moving to IPv6 could certainly mean there are somewhat
fewer motivating factors for network operators to deploy IPv6 to end
user hosts (though they have many significant motivating factors that
are largely independent of content). At the same time, unless
network operators transition to IPv6, there are of course fewer
motivations for domain owners to transition content to IPv6. Without
progress in each part of the Internet ecosystem, networks and/or
content sites may delay, postpone, or cease adoption of IPv6, or to
actively seek alternatives to it. Such alternatives may include the
use of multi-layer or large scale network address translation (NAT),
which is not preferred relative to native dual stack.
Obviously, transitioning content to IPv6 is important to IPv6
adoption overall. While challenges do exist, such a transition is
not an impossible task for a domain to undertake. A range of
potential migration tactics, as noted below in Section 4, can help
meet these challenges and enable a domain to successfully transition
content and other services to IPv6.
4. Potential Migration Tactics
Domains have a wide range of potential tactics at their disposal that
may be used to facilitate the migration to IPv6. This section
includes many of the key tactics that could be used by a domain but
it is by no means an exhaustive or exclusive list. Only a specific
domain can judge whether or not a given (or any) migration tactic
applies to their domain and meets their needs. A domain may also
decide to pursue several of these tactics in parallel. Thus, the
usefulness of each tactic and the associated pros and cons will vary
from domain to domain.
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4.1. Solve Current End User IPv6 Impairments
Domains can endeavor to fix the underlying technical problems
experienced by their end users during the transition to IPv6, as
noted in Section 2.1. One challenge with this option is that a
domain may have little or no control over the network connectivity,
operating system, client software (such as a web browser), and/or
other capabilities of the end users of that domain. In most cases a
domain is only in a position to influence and guide their end users.
While this is not the same sort of direct control which may exist in
an enterprise network for example, major domains are likely to be
trusted by their end users and may therefore be able to influence and
guide these users in solving any IPv6-related impairments.
Another challenge is that end user impairments are something that one
domain on their own cannot solve. This means that domains may find
it more effective to coordinate with many others in the Internet
community to solve what is really a collective problem that affects
the entire Internet. Of course, it can sometimes be difficult to
motivate members of the Internet community to work collectively
towards such a goal, sharing the labor, time, and costs related to
such an effort. However, World IPv6 Day [W6D] shows that such
community efforts are possible and despite any potential challenges,
the Internet community continues to work together in order to solve
end user IPv6 impairments.
One potential tactic may be to identify which users have such
impairments and then to communicate this information to affected
users. Such end user communication is likely to be most helpful if
the end user is not only alerted to a potential problem but is given
careful and detailed advice on how to resolve this on their own, or
is guided to where they can seek help in doing so. Another potential
tactic is for a domain to collect, track over time, and periodically
share with the Internet community the rate of impairment observed for
a domain. In any such end user IPv6-related analysis and
communication, Section 6.2 is worth taking into account.
However, while these tactics can help reduce IPv6-related impairments
Section 2.1, they do not address either operational maturity concerns
noted in Section 2.2 or volume-based concerns noted in Section 2.3,
which should be considered and addressed separately.
4.2. Use IPv6-Specicic Names
Another potential migration tactic is for a domain to gain experience
using a special Fully-Qualified Domain Name (FQDN). This has become
typical for domains beginning the transition to IPv6, whereby an
address-family-specific name such as ipv6.example.com or
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www.ipv6.example.com is used. An end user would have to know to use
this special IPv6-specific name; it is not the same name used for
regular traffic.
This special IPv6-specific name directs traffic to a host or hosts
which have been enabled for native IPv6 access. In some cases this
name may point to hosts which are separate from those used for IPv4
traffic (via www.example.com), while in other cases it may point to
the same hosts used for IPv4 traffic. A subsequent phase, if
separate hosts are used to support special IPv6-specific names, is to
move to the same hosts used for regular traffic in order to utilize
and exercise production infrastructure more fully. Regardless of
whether or not dedicated hosts are used, the use of the special name
is a way to incrementally control traffic as a tool for a domain to
gain IPv6 experience and increase IPv6 use on a relatively controlled
basis. Any lessons learned can then inform plans for a full
transition to IPv6. This also provides an opportunity for a domain
to develop any necessary training for staff, to develop IPv6-related
testing procedures for their production network and lab, to deploy
IPv6 functionality into their production network, and to develop and
deploy IPv6-related network and service monitors. It is also an
opportunity to add a relatively small amount of IPv6 traffic to
ensure that network gear, network interconnects, and IPv6 routing in
general is working as expected.
While using a special IPv6-specific name is a good initial step to
functionally test and prepare a domain for IPv6, including developing
and maturing IPv6 operations, as noted in Section 2.2, the utility of
the tactic is limited since users must know the IPv6-specific name,
the traffic volume will be low, and the traffic is unlikely to be
representative of the general population of end users (they are
likely to be self-selecting early adopters and more technically
advanced than average), among other reasons. As a result, any
concerns and risks related to traffic volume as noted Section 2.3
should still be considered and addressed separately.
4.3. Implement DNS Resolver Whitelisting
Another potential tactic, especially when a high-service-level domain
is ready to move beyond an IPv6-specific name, as described in
Section 4.2, is to selectively return AAAA resource records (RRs),
which contain IPv6 addresses. This selective response of DNS records
is performed by an authoritative DNS servers for a domain in response
to DNS queries sent by DNS recursive resolvers [RFC1035]. This is
commonly referred to in the Internet community as "DNS Resolver
Whitelisting", and will be referred to as such hereafter, though in
essence it is simply a tactic enabling the selective return of DNS
records based upon various technical factors. An end user is seeking
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a resource by name, and this selective response mechanism enables
what is perceived to be the most reliable and best performing IP
address family to be used (IPv4 or IPv6). It shares similarities
with Content Delivery Networks, Global Server Load Balancing, DNS
Load Balancing, and Split DNS, as described below in Section 4.3.2,
Section 4.3.3, Section 4.3.4. A few high-service-level domains have
either implemented DNS Resolver Whitelisting (one of many migration
tactics they have used or are using) or are considering doing so
[NW-Article-DNS-WL] [WL-Ops].
This is a migration tactic used by domains as a method for
incrementally transitioning inbound traffic to a domain to IPv6. If
an incremental tactic like this is not used, a domain might return
AAAA resource records to any relevant DNS query, meaning the domain
could go quickly from no IPv6 traffic to potentially a significant
amount as soon as the AAAA resource records are published. When DNS
Resolver Whitelisting is implemented, a domain's authoritative DNS
will selectively return a AAAA resource record to DNS recursive
resolvers on a whitelist maintained by the domain, while returning no
AAAA resource records to DNS recursive resolvers which are not on
that whitelist. This tactic will not have a direct impact on
reducing IPv6-related impairments Section 2.1, though it can help a
domain address operational maturity concerns Section 2.2 and concerns
and risks related to traffic volume Section 2.3. While DNS Resolver
Whitelisting does not solve IPv6-related impairments, it can help a
domain to avoid users that have them. As a result, the tactic
removes their impact in all but the few networks that are
whitelisted. DNS Resolver Whitelisting also allows a website
operator to protect non-IPv6 networks (i.e. networks that do not
support IPv6 and/or do not have plans to do so in the future) from
IPv6-related impairments in their networks. Finally, domains using
this tactic should understand that the onus is on them to ensure that
the servers being whitelisted represent a network that has proven to
their satisfaction that they are IPv6-ready and this will not create
a poor end user experience for users of the whitelisted server.
There are of course challenges and concerns relating to DNS Resolver
Whitelisting. Some of the concerns with a whitelist of DNS recursive
resolvers may be held by parties other than the implementing domain,
such as network operators or end users that may not have had their
DNS recursive resolvers added to a whitelist. Additionally, the IP
address of a DNS recursive resolver is not a precise indicator of the
IPv6 preparedness, or lack of IPv6-related impairment, of end user
hosts which query (use) a particular DNS recursive resolver. While
the IP addresses of DNS recursive resolvers on networks known to have
deployed IPv6 may be an imperfect proxy for judging IPv6
preparedness, or lack of IPv6-related impairment, it is one of the
better available methods at the current time. For example,
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implementers have found that it is possible to measure the level of
IPv6 preparedness of the end users behind any given DNS recursive
resolver by conducting ongoing measurement of the IPv6 preparedness
of end users querying for one-time-use hostnames and then correlating
the domain's authoritative DNS server logs with their web server
logs. This can help implementers form a good picture of which DNS
recursive resolvers have working IPv6 users behind them and which do
not, what the latency impact of turning on IPv6 for any given DNS
recursive resolver is, etc. In addition, given the current state of
global IPv6 deployment, this migration tactic allows content
providers to selectively expose the availability of their IPv6
services. While opinions in the Internet community concerning DNS
Resolver Whitelisting are understandably quite varied, there is clear
consensus that DNS Resolver Whitelisting can be a useful tactic for
use during the transition of a domain to IPv6. In particular, some
high-service-level domains view DNS Resolver Whitelisting as one of
the few practical and low-risk approaches enabling them to transition
to IPv6, without which their transition may not take place for some
time. However, there is also consensus that this practice is
workable on a manual basis (see below) only in the short-term and
that it will not scale over the long-term. Thus, some domains may
find DNS Resolver Whitelisting a beneficial temporary tactic in their
transition to IPv6.
At the current time, generally speaking, a domain that implements DNS
Resolver Whitelisting does so manually. This means that a domain
manually maintains a list of networks that are permitted to receive
IPv6 records (via their DNS resolver IP addresses) and that these
networks typically submit applications, or follow some other process
established by the domain, in order to be added to the DNS Whitelist.
However, implementers foresee that a subsequent phase of DNS Resolver
Whitelisting is likely to emerge in the future, possibly in the near
future. In this new phase a domain would return IPv6 and/or IPv4
records dynamically based on automatically detected technical
capabilities, location, or other factors. It would then function
much like (or indeed as part of) global server load balancing, a
common practice already in use today, as described in Section 4.3.2.
Furthermore, in this future phase, networks would be added to and
removed from a DNS Whitelist automatically, and possibly on a near-
real-time basis. This means, crucially, that networks would no
longer need to apply to be added to a whitelist, which may alleviate
many of the key concerns that network operators may have with this
tactic when it is implemented on a manual basis.
4.3.1. How DNS Resolver Whitelisting Works
Using a "whitelist" in a generic sense means that no traffic (or
traffic of a certain type) is permitted to the destination host
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unless the originating host's IP address is contained in the
whitelist. In contrast, using a "blacklist" means that all traffic
is permitted to the destination host unless the originating host's IP
address is contained in the blacklist. In the case of DNS Resolver
Whitelisting, the resource that an end user seeks is a name, not an
IP address or IP address family. Thus, an end user is seeking a name
such as www.example.com, without regard to the underlying IP address
family (IPv4 or IPv6) which may be used to access that resource.
DNS Resolver Whitelisting is implemented in authoritative DNS
servers, not in DNS recursive resolvers. These authoritative DNS
servers selectively return AAAA resource records using the IP address
of the DNS recursive resolver that has sent it a query. Thus, for a
given operator of a website, such as www.example.com, the domain
operator implements whitelisting on the authoritative DNS servers for
the domain example.com. The whitelist is populated with the IPv4
and/or IPv6 addresses or prefix ranges of DNS recursive resolvers on
the Internet, which have been authorized to receive AAAA resource
record responses. These DNS recursive resolvers are operated by
third parties, such as Internet Service Providers (ISPs),
universities, governments, businesses, and individual end users. If
a DNS recursive resolver is not matched in the whitelist, then AAAA
resource records WILL NOT be sent in response to a query for a
hostname in the example.com domain (and an A record would be sent).
However, if a DNS recursive resolver is matched in the whitelist,
then AAAA resource records WILL be sent. As a result, while Section
2.2 of [RFC4213] notes that a stub resolver can make a choice between
whether to use a AAAA record or A record response, with DNS Resolver
Whitelisting the authoritative DNS server can also decide whether to
return a AAAA record, an A record, or both record types.
When implemented on a manual basis, DNS Resolver Whitelisting
generally means that a very small fraction of the DNS recursive
resolvers on the Internet (those in the whitelist) will receive AAAA
responses. The large majority of DNS recursive resolvers on the
Internet will therefore receive only A resource records containing
IPv4 addresses. When implemented manually, domains may find the
practice imposes some incremental operational burdens insofar as it
can consume staff time to maintain a whitelist (such as additions and
deletions to the list), respond to and review applications to be
added to a whitelist, maintain good performance levels on
authoritative DNS servers as the whitelist grows, create new network
monitors to check the health of a whitelist function, perform new
types of troubleshooting related to whitelisting, etc. In addition,
manually-based whitelisting imposes some incremental burdens on
operators of DNS recursive resolvers (such as network operators),
since they will need to apply to be whitelisted with any implementing
domains, and will subsequently need processes and systems to track
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the status of whitelisting applications, respond to requests for
additional information pertaining to these applications, and track
any de-whitelisting actions.
When implemented on an automated basis in the future, DNS recursive
resolvers listed in the whitelist could expand and contract
dynamically, and possibly in near-real-time, based on a wide range of
factors. As a result, it is likely that the number of DNS recursive
resolvers on the whitelist will be substantially larger than when
such a list is maintained manually, and it is likely the the
whitelist will grow at a rapid rate. This automation can eliminate
most of the significant incremental operational burdens on both
implementing domains as well as operators of DNS recursive resolvers,
which is clearly a factor that is motivating implementers to work to
automate this function.
Section 4.3.1.1 and Figure 1 have more details on DNS Resolver
Whitelisting generally. In addition, the potential deployment models
of DNS Resolver Whitelisting (manual and automated) are described in
Section 5. It is also important to note that DNS Resolver
Whitelisting also works independently of whether an authoritative DNS
server, DNS recursive resolver, or end user host uses IPv4 transport,
IPv6, or both. So, for example, whitelisting may not result in the
return of AAAA responses even in those cases where the DNS recursive
resolver has queried the authoritative server over IPv6 transport.
This may also be the case in some situations when the end user host's
original query to its DNS recursive resolver was over IPv6 transport,
if that DNS recursive resolver is not on a given whitelist. One
important reason for this is that even though the DNS recursive
resolver may have no IPv6-related impairments, this is not a reliable
predictor of whether the same is true of the end user host. This
also means that a DNS whitelist can contain both IPv4 and IPv6
addresses.
4.3.1.1. Description of the Operation of DNS Resolver Whitelisting
Specific implementations will vary from domain to domain, based on a
range of factors such as the technical capabilities of a given
domain. As such, any examples listed herein should be considered
general examples and are not intended to be exhaustive.
The system logic of DNS Resolver Whitelisting is as follows:
1. The authoritative DNS server for example.com receives DNS queries
for the A (IPv4) and/or AAAA (IPv6) address resource records for
the Fully Qualified Domain Name (FQDN) www.example.com, for which
AAAA (IPv6) resource records exist.
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2. The authoritative DNS server checks the IP address (IPv4, IPv6,
or both) of the DNS recursive resolver sending the AAAA (IPv6)
query against the whitelist that is the DNS Whitelist.
3. If the DNS recursive resolver's IP address IS matched in the
whitelist, then the response to that specific DNS recursive
resolver can contain AAAA (IPv6) address resource records.
4. If the DNS recursive resolver's IP address IS NOT matched in the
whitelist, then the response to that specific DNS recursive
resolver cannot contain AAAA (IPv6) address resource records. In
this case, the server will likely return a response with the
response code (RCODE) being set to 0 (No Error) with an empty
answer section for the AAAA record query.
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+--------------------------------------------------------------------+
| Caching Server 1 - IS NOT ON the DNS Whitelist |
| Caching Server 2 - IS ON the DNS Whitelist |
| Note: Transport between each host can be IPv4 or IPv6. |
+--------------------------------------------------------------------+
+----------+ +---------------+ +---------------+
| Stub | | DNS Caching | | DNS |
| Resolver | | Server 1 | | Server |
+----------+ +---------------+ +---------------+
| DNS Query: | |
| example.com A, AAAA | |
|---------------------->| |
| | |
| | DNS Query: |
| | example.com A, AAAA |
| |------------------------>|
| | |
| | | NOT on Whitelist
| | DNS Response: |
| | example.com A |
| |<------------------------|
| | |
| DNS Response: | |
| example.com A | |
|<----------------------| |
+----------+ +---------------+ +---------------+
| Stub | | DNS Caching | | DNS |
| Resolver | | Server 2 | | Server |
+----------+ +---------------+ +---------------+
| DNS Query: | |
| example.com A, AAAA | |
|---------------------->| |
| | |
| | DNS Query: |
| | example.com A, AAAA |
| |------------------------>|
| | |
| | | IS on Whitelist
| | DNS Response: |
| | example.com A, AAAA |
| |<------------------------|
| | |
| DNS Response: | |
| example.com A, AAAA | |
|<----------------------| |
Figure 1: DNS Resolver Whitelisting Diagram
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4.3.2. Similarities to Content Delivery Networks and Global Server Load
Balancing
DNS Resolver Whitelisting is functionally similar to Content Delivery
Networks (CDNs) and Global Server Load Balancing (GSLB). When using
a CDN or GSLB, a geographically-aware authoritative DNS server
function is usually part of that overall system. As a result, the
use of a CDN or GSLB with an authoritative DNS server function
enables the IP address resource records returned to a resolver in
response to a query to vary based on the estimated geographic
location of the resolver [Wild-Resolvers] or a range of other
technical factors. This CDN or GSLB DNS function is performed in
order to attempt to direct hosts to connect to the nearest hosts (as
measured in round trip time), to the host that has the best
connectivity to an end user, to route around failures, to avoid sites
where maintenance work has taken down hosts, and/or to the host that
will otherwise provide the best service experience for an end user at
a given point in time. As a result, one can see a direct similarity
to DNS Resolver Whitelisting insofar as different IP address resource
records are selectively returned to resolvers based on the IP address
of each resolver and/or other imputed factors related to that IP
address.
4.3.3. Similarities to DNS Load Balancing
DNS Resolver Whitelisting has some similarities to DNS load
balancing. There are of course many ways that DNS load balancing can
be performed. In one example, multiple IP address resource records
(A and/or AAAA) can be added to the DNS for a given FQDN. This
approach is referred to as DNS round robin [RFC1794]. DNS round
robin may also be employed where SRV resource records are used
[RFC2782]. In another example, one or more of the IP address
resource records in the DNS will direct traffic to a load balancer.
That load balancer, in turn, may be application-aware, and pass the
traffic on to one or more hosts connected to the load balancer which
have different IP addresses. In cases where private IPv4 addresses
are used [RFC1918], as well as when public IP addresses are used,
those end hosts may not necessarily be directly reachable without
passing through the load balancer first. So, similar to DNS Resolver
Whitelisting, a load balancer will control what server host an end
user's host communicates with when using a FQDN.
4.3.4. Similarities to Split DNS
DNS Resolver Whitelisting has some similarities to so-called split
DNS, briefly described in Section 3.8 of [RFC2775]. When split DNS
is used, the authoritative DNS server selectively returns different
responses depending upon what host has sent the query. While
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[RFC2775] notes the typical use of split DNS is to provide one answer
to hosts on an Intranet (internal network) and a different answer to
hosts on the Internet (external or public network), the basic idea is
that different answers are provided to hosts on different networks.
This is similar to the way that DNS Resolver Whitelisting works,
whereby hosts on different networks which use different DNS recursive
resolvers, receive different answers if one DNS recursive resolver is
on the whitelist and the other is not. However, Internet
transparency and Internet fragmentation concerns regarding split DNS
are detailed in Section 2.1 of [RFC2956] and Section 2.7 notes
concerns regarding split DNS and that it "makes the use of Fully
Qualified Domain Names (FQDNs) as endpoint identifiers more complex".
Section 3.5 of [RFC2956] further recommends that maintaining a stable
approach to DNS operations is key during transitions, such as the one
to IPv6 that is underway now, stating that "Operational stability of
DNS is paramount, especially during a transition of the network
layer, and both IPv6 and some network address translation techniques
place a heavier burden on DNS."
4.3.5. Related Considerations
While techniques such as GLSB and DNS load balancing, which share
much in common with DNS Resolver Whitelisting and are widespread,
some in the community have raised a range of concerns about the
practice. Some concerns are specific DNS Resolver Whitelisting
[WL-Concerns]. Other concerns are not as specific and pertain to the
general practice of implementing content location or other network
policy controls in the "middle" of the network in a so-called
"middlebox" function. Whether such DNS-related functions are really
part of a middlebox is debatable. Nevertheless, implementers should
at least be aware of some of the risks of middleboxes, as noted in
[RFC3724]. A related document, [RFC1958] explains that the state,
policies, and other functions needed in the middle of the network
should be minimized as a design goal. In addition, Section 2.16 of
[RFC3234] makes specific statements concerning modified DNS servers.
[RFC3234] also outlines more general concerns in Section 1.2 about
the introduction of new failure modes when configuration is no longer
limited to two ends of a session, so that diagnosis of failures and
misconfigurations could become more complex. Two additional sources
worth considering are [Tussle] and [Rethinking], in which the authors
note concerns regarding the introduction of new control points (such
as in middleboxes), including in the DNS.
However, some state, policies, and other functions have always been
necessary to enable effective, reliable, and high-quality end-to-end
communications on the Internet. In addition, techniques such as
Global Server Load Balancing, Content Delivery Networking, DNS Load
Balancing and Split DNS are not only widely deployed but are almost
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uniformly viewed as essential to the functioning of the Internet and
highly beneficial to the quality of the end user experience on the
Internet. These techniques have had and continue to have a
beneficial effect on the experience of a wide range of Internet
applications and protocols. So while there are valid concerns about
implementing policy controls in the "middle" of the network, or
anywhere away from edge hosts, the definition of what constitutes the
middle and edge of the network is debatable in this case. This is
particularly so given that GSLBs and CDNs facilitate connections from
end host and the optimal content hosts, and could therefore be
considered a modest and in many cases essential network policy
extension of a network's edge, especially in the case of high-
service-level domains.
There may be additional implications for end users that have
configured their hosts to use a third party as their DNS recursive
resolver, rather than the one(s) provided by their network operator.
In such cases, it will be more challenging for a domain using
whitelisting to determine the level of IPv6-related impairment when
such third-party DNS recursive resolvers are used, given the wide
variety of end user access networks which may be used and that this
mix may change in unpredictable ways over time.
4.4. Implement DNS Blacklisting
With DNS Resolver Whitelisting, DNS recursive resolvers can receive
AAAA resource records only if they are on the whitelist. DNS
Blacklisting is by contrast the the opposite of that, whereby all DNS
recursive resolvers can receive AAAA resource records unless they are
on the blacklist. Some implementers of DNS Resolver Whitelisting may
choose to subsequently transition to DNS Blacklisting. It is unclear
when and if it may be appropriate for a domain to change from
whitelisting to blacklisting. Nor is it clear how implementers will
judge the network conditions to have changed sufficiently to justify
disabling such controls.
When a domain uses blacklisting, they are enabling all DNS recursive
resolvers to receive AAAA record responses except for what is
presumed to be a relatively small number that are on the blacklist.
Over time it is likely that the blacklist will become smaller as the
networks associated with the blacklisted DNS recursive resolvers are
able to meaningfully reduce IPv6-related impairments to some
acceptable level, though it is possible that some networks may never
achieve that. DNS Blacklisting is also likely less labor intensive
for a domain than performing DNS Resolver Whitelisting on a manual
basis. This is simply because the domain would presumably be focused
on a smaller number of DNS recursive resolvers with well known IPv6-
related problems.
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It is also worth noting that the email industry has a long experience
with blacklists and, very generally speaking, blacklists tend to be
effective and well received when it is easy to discover if an IP
address is on a blacklist, if there is a transparent and easily
understood process for requesting removal from a blacklist, and if
the decision-making criteria for placing a server on a blacklist is
transparently disclosed and perceived as fair. However, in contrast
to an email blacklist where a blacklisted host cannot send email to a
domain at all, with DNS Resolver Whitelisting communications will
still occur over IPv4 transport.
4.5. Transition Directly to Native Dual Stack
As an alternative to adopting any of the aforementioned migration
tactics, domains can choose to transition to native dual stack
directly by adding native IPv6 capabilities to their network and
hosts and by publishing AAAA resource records in the DNS for named
resources within their domain. Of course, a domain can still control
this transition gradually, on a name-by-name basis, by adding native
IPv6 to one name at a time, such as mail.example.com first and
www.example.com later. So even a "direct" transition can be
performed gradually.
It is then up to end users with IPv6-related impairments to discover
and fix any applicable impairments. However, the concerns and risks
related to traffic volume Section 2.3 should still be considered and
managed, since those are not directly related to such impairments.
Not all content providers (or other domains) may face the challenges
detailed herein or face them to the same degree, since the user base
of each domain, traffic sources, traffic volumes, and other factors
obviously varies between domains.
For example, while some content providers have implemented DNS
Resolver Whitelisting (one migration tactic), others have run IPv6
experiments whereby they added AAAA resource records and observed and
measured errors, and then decided not to implement DNS Resolver
Whitelisting [Heise]. A more widespread such experiment was World
IPv6 Day [W6D], sponsored by the Internet Society, on June 8, 2011.
This was a unique opportunity for hundreds of domains to add AAAA
resource records to the DNS without using DNS Resolver Whitelisting,
all at the same time. Some of the participating domains chose to
leave AAAA resource records in place following the experiment based
on their experiences.
Content providers can run their own independent experiments in the
future, adding AAAA resource records for a brief period of time
(minutes, hours, or days), and then analyzing any impacts or effects
on traffic and the experience of end users. They can also simply
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turn on IPv6 for their domain, which may be easier when the
transition does not involve a high-service-level domain.
5. Potential Implementation Phases
These usefulness of each tactic in Section 4, and the associated pros
and cons associated with each tactic, is relative to each potential
implementer and will therefore vary from one implementer to another.
As a result, it is not possible to say that the potential phases
below make sense for every implementer. This also means that the
duration of each phase will vary between implementers, and even that
different implementers may skip some of these phases entirely.
Finally, the tactics listed in Section 4 are by no means exclusive.
5.1. No Access to IPv6 Content
In this phase, a site is accessible only via IPv4 transport. As of
the time of this document, the majority of content on the Internet is
in this state and is not accessible natively over IPv6.
5.2. Using IPv6-Specific Names
One possible first step for a domain is to gain experience using a
specialized new FQDN, such as ipv6.example.com or
www.ipv6.example.com, as explained in Section 4.2.
5.3. Deploying DNS Resolver Whitelisting Using Manual Processes
As noted in Section 4.3, a domain could begin using DNS Resolver
Whitelisting as a way to incrementally enable IPv6 access to content.
This tactic may be especially interesting to high-service-level
domains.
5.4. Deploying DNS Resolver Whitelisting Using Automated Processes
For a domain that decides to undertake DNS Resolver Whitelisting on a
manual basis, the domain may subsequently move to perform DNS
Resolver Whitelisting on an automated basis. This is explained in
Section 4.3, and can significantly ease any operational burdens
relating to a manually-maintained whitelist.
5.5. Turning Off DNS Resolver Whitelisting
Domains that choose to implement DNS Resolver Whitelisting generally
consider it to be a temporary measure. Many implementers have
announced that they plan to permanently turn off DNS Resolver
Whitelisting beginning on the date of the World IPv6 Launch, on June
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6, 2012 [World IPv6 Launch]. For any implementers that do not turn
off DNS Resolver Whitelisting at that time, it may be unclear how
each and every one will judge when the network conditions to have
changed sufficiently to justify turning off DNS Resolver
Whitelisting. That being said, it is clear that the extent of IPv6
deployment to end users in networks, the state of IPv6-related
impairment, and the maturity of IPv6 operations are all important
factors. Any such implementers may wish to take into consideration
that, as a practical matter, it will be impossible to get to a point
where there are no longer any IPv6-related impairments; some
reasonably small number of hosts will inevitably be left behind as
end users elect not to upgrade them or as some hosts are incapable of
being upgraded.
5.6. Deploying DNS Blacklisting
Regardless of whether a domain has first implemented DNS Resolver
Whitelisting or has never done so, DNS Blacklisting as described in
Section 4.4 may become interesting. This may be at the point in time
when domains wish to make their content widely available over IPv6
but still wish to protect end users of a few networks with well known
IPv6 limitations from having a bad end user experience.
5.7. Fully Dual-Stack Content
A domain can arrive at this phase either following the use of a
previous IPv6 migration tactic, or they may go directly to this point
as noted in Section 4.5. In this phase the site's content has been
made natively accessible via both IPv4 and IPv6 for all end users on
the Internet, or at least without the use of any other IPv6 migration
tactic.
6. Other Considerations
6.1. Security Considerations
If DNS Resolver Whitelisting is adopted, as noted in Section 4.3,
then organizations which apply DNS Resolver Whitelisting policies in
their authoritative servers should have procedures and systems which
do not allow unauthorized parties to modify the whitelist or
blacklist, just as all configuration settings for name servers should
be protected by appropriate procedures and systems. Such
unauthorized additions or removals from the whitelist can be
damaging, causing content providers and/or network operators to incur
support costs resulting from end user and/or customer contacts, as
well as causing potential dramatic and disruptive swings in traffic
from IPv6 to IPv4 or vice versa.
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DNS security extensions defined in [RFC4033], [RFC4034], and
[RFC4035] use cryptographic digital signatures to provide origin
authentication and integrity assurance for DNS data. This is done by
creating signatures for DNS data on a Security-Aware Authoritative
Name Server that can be used by Security-Aware Resolvers to verify
the answers. Since DNS Resolver Whitelisting is implemented on an
authoritative DNS server, which provides different answers depending
upon which DNS resolver has sent a query, the DNSSEC chain of trust
is not altered. So even though an authoritative DNS server will
selectively return AAAA resource records or a non-existence response,
both types of response will be signed and will validate. In
practical terms this means that two separate views or zones are used,
each of which is signed, so that whether or not particular resource
records exist, the existence or non-existence of the record can still
be validated using DNSSEC. As a result, there should not be any
negative impact on DNSSEC for those domains that have implemented
both DNSSEC on their Security-Aware Authoritative Name Servers and
also implemented DNS Resolver Whitelisting. As for any party
implementing DNSSEC of course, such domains should ensure that
resource records are being appropriately and reliably signed and
consistent with the response being returned.
However, network operators that run DNS recursive resolvers should be
careful not to modify the responses received from authoritative DNS
servers. It is possible that some networks may attempt to do so in
order to prevent AAAA record responses from going to end user hosts,
due to some IPv6-related impairment or other lack of IPv6 readiness
with that network. But when a network operates a Security-Aware
Resolver, modifying or suppressing AAAA resource records for a
DNSSEC-signed domain could break the chain of trust established with
DNSSEC.
6.2. Privacy Considerations
As noted in Section 4.1, there is a benefit in sharing IPv6-related
impairment statistics within the Internet community over time. Any
statistics that are shared or disclosed publicly should be aggregate
statistics, such as "the domain example.com has observed an average
daily impairment rate of 0.05% in September 2011, down from 0.15% in
January 2011". They should not include information that can directly
or indirectly identify individuals, such as names or email addresses.
Sharing only aggregate data can help protect end user privacy and any
information which may be proprietary to a domain.
In addition, there are often methods to detect IPv6-related
impairments for a specific end user, such as running an IPv6 test
when an end user visits the website of a particular domain. Should a
domain then choose to automatically communicate the facts of an
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impairment to an affected user, there are likely no direct privacy
considerations. However, if the domain then decided to share
information concerning that particular end user with that user's
network operator or another third party, then the domain may wish to
consider advising the end user of this and seeking to obtain the end
user's consent to share such information.
Appropriate guidelines for any information sharing likely varies by
country and/or legal jurisdiction. Domains should consider any
potential privacy issues when considering what information can be
shared. If a domain does publish or share detailed impairment
statistics, they would be well advised to avoid identifying
individual hosts or users.
Finally, if a domain chooses to contact end userd directly concerning
their IPv6 impairments, that domain should ensure that such
communication is permissible under any applicable privacy policies of
the domain or its websites.
6.3. Considerations with Poor IPv4 and Good IPv6 Transport
There are situations where the differing quality of the IPv4 and IPv6
connectivity of an end user could cause complications in accessing
content when a domain is using an IPv6 migration tactic. While today
most end users' IPv4 connectivity is typically superior to IPv6
connectivity (if such connectivity exists at all), there could be
implications when the reverse is true and and end user has markedly
superior IPv6 connectivity as compared to IPv4. This is not a
theoretical situation; it has been observed by at least one major
content provider.
For example, in one possible scenario, a user is issued IPv6
addresses by their ISP and has a home network and devices or
operating systems which fully support native IPv6. As a result this
theoretical user has very good IPv6 connectivity. However, this end
user's ISP has exhausted their available pool of unique IPv4 address,
and uses NAT in order to share IPv4 addresses among end users. So
for IPv4 content, the end user must send their IPv4 traffic through
some additional network element (e.g. large scale NAT, proxy server,
tunnel server). Use of this additional network element might cause
an end user to experience sub-optimal IPv4 connectivity when certain
protocols or applications are used. This user then has good IPv6
connectivity but impaired IPv4 connectivity. As a result, the user's
poor IPv4 connectivity situation could potentially be exacerbated
when accessing a domain which is using a migration tactic that causes
this user to only be able to access content over IPv4 transport for
whatever reason.
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Should this sort of situation become widespread in the future, a
domain may wish to take it into account when deciding how and when to
transition content to IPv6.
6.4. IANA Considerations
There are no IANA considerations in this document.
7. Contributors
The following people made significant textual contributions to this
document and/or played an important role in the development and
evolution of this document:
- John Brzozowski
- Chris Griffiths
- Tom Klieber
- Yiu Lee
- Rich Woundy
8. Acknowledgements
The author and contributors also wish to acknowledge the assistance
of the following individuals or groups. Some of these people
provided helpful and important guidance in the development of this
document and/or in the development of the concepts covered in this
document. Other people assisted by performing a detailed review of
this document, and then providing feedback and constructive criticism
for revisions to this document, or engaged in a healthy debate over
the subject of the document. All of this was helpful and therefore
the following individuals merit acknowledgement:
- Bernard Aboba
- Mark Andrews
- Jari Arkko
- Fred Baker
- Ron Bonica
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- Frank Bulk
- Brian Carpenter
- Lorenzo Colitti
- Alissa Cooper
- Dave Crocker
- Ralph Droms
- Wesley Eddy
- J.D. Falk
- Adrian Farrel
- Stephen Farrell
- Tony Finch
- Karsten Fleischhauer
- Igor Gashinsky
- Wesley George
- Philip Homburg
- Jerry Huang
- Ray Hunter
- Joel Jaeggli
- Erik Kline
- Suresh Krishnan
- Victor Kuarsingh
- Marc Lampo
- Donn Lee
- John Leslie
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- John Mann
- Danny McPherson
- Milo Medin
- Martin Millnert
- Russ Mundy
- Thomas Narten
- Pekka Savola
- Robert Sparks
- Barbara Stark
- Joe Touch
- Hannes Tschofenig
- Tina Tsou
- Members of the Broadband Internet Technical Advisory Group (BITAG)
9. References
9.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC1794] Brisco, T., "DNS Support for Load Balancing", RFC 1794,
April 1995.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[RFC1958] Carpenter, B., "Architectural Principles of the Internet",
RFC 1958, June 1996.
[RFC2775] Carpenter, B., "Internet Transparency", RFC 2775,
February 2000.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
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specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC2956] Kaat, M., "Overview of 1999 IAB Network Layer Workshop",
RFC 2956, October 2000.
[RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
Issues", RFC 3234, February 2002.
[RFC3724] Kempf, J., Austein, R., and IAB, "The Rise of the Middle
and the Future of End-to-End: Reflections on the Evolution
of the Internet Architecture", RFC 3724, March 2004.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
[RFC4213] Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
for IPv6 Hosts and Routers", RFC 4213, October 2005.
9.2. Informative References
[Heise] Heise.de, "The Big IPv6 Experiment", Heise.de
Website http://www.h-online.com, January 2011, <http://
www.h-online.com/features/
The-big-IPv6-experiment-1165042.html>.
[I-D.ietf-v6ops-happy-eyeballs]
Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
Dual-Stack Hosts", draft-ietf-v6ops-happy-eyeballs-07
(work in progress), December 2011.
[IETF-77-DNSOP]
Gashinsky, I., "IPv6 & recursive resolvers: How do we make
the transition less painful?", IETF 77 DNS Operations
Working Group, March 2010,
<http://www.ietf.org/proceedings/77/slides/dnsop-7.pdf>.
[IPv6-Brokenness]
Anderson, T., "Measuring and Combating IPv6 Brokenness",
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Reseaux IP Europeens (RIPE) 61st Meeting, November 2010,
<http://ripe61.ripe.net/presentations/162-ripe61.pdf>.
[IPv6-Growth]
Colitti, L., Gunderson, S., Kline, E., and T. Refice,
"Evaluating IPv6 adoption in the Internet", Passive and
Active Management (PAM) Conference 2010, April 2010,
<http://www.google.com/research/pubs/archive/36240.pdf>.
[NW-Article-DNS-WL]
Marsan, C., "Google, Microsoft, Netflix in talks to create
shared list of IPv6 users", Network World , March 2010, <h
ttp://www.networkworld.com/news/2010/
032610-dns-ipv6-whitelist.html>.
[NW-Article-DNSOP]
Marsan, C., "Yahoo proposes 'really ugly hack' to DNS",
Network World , March 2010, <http://www.networkworld.com/
news/2010/032610-yahoo-dns.html>.
[RFC6343] Carpenter, B., "Advisory Guidelines for 6to4 Deployment",
RFC 6343, August 2011.
[Rethinking]
Blumenthal, M. and D. Clark, "Rethinking the design of the
Internet: The end to end arguments vs. the brave new
world", ACM Transactions on Internet Technology Volume 1,
Number 1, Pages 70-109, August 2001, <http://
dspace.mit.edu/bitstream/handle/1721.1/1519/
TPRC_Clark_Blumenthal.pdf>.
[Tussle] Braden, R., Clark, D., Sollins, K., and J. Wroclawski,
"Tussle in Cyberspace: Defining Tomorrow's Internet",
Proceedings of ACM Sigcomm 2002, August 2002, <http://
groups.csail.mit.edu/ana/Publications/PubPDFs/
Tussle2002.pdf>.
[W6D] The Internet Society, "World IPv6 Day - June 8, 2011",
Internet Society Website http://www.isoc.org,
January 2011, <http://isoc.org/wp/worldipv6day/>.
[WL-Concerns]
Brzozowski, J., Griffiths, C., Klieber, T., Lee, Y.,
Livingood, J., and R. Woundy, "IPv6 DNS Resolver
Whitelisting - Could It Hinder IPv6 Adoption?",
ISOC Internet Society IPv6 Deployment Workshop,
April 2010, <http://www.comcast6.net/
IPv6_DNS_Whitelisting_Concerns_20100416.pdf>.
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[WL-Ops] Kline, E., "IPv6 Whitelist Operations", Google Google IPv6
Implementors Conference, June 2010, <http://
sites.google.com/site/ipv6implementors/2010/agenda/
IPv6_Whitelist_Operations.pdf>.
[Wild-Resolvers]
Ager, B., Smaragdakis, G., Muhlbauer, W., and S. Uhlig,
"Comparing DNS Resolvers in the Wild", ACM Sigcomm
Internet Measurement Conference 2010, November 2010,
<http://conferences.sigcomm.org/imc/2010/papers/p15.pdf>.
[World IPv6 Launch]
The Internet Society, "World IPv6 Launch Website", 2012,
<http://www.worldipv6launch.org/>.
Appendix A. Document Change Log
[RFC Editor: This section is to be removed before publication]
-11: Minor update to one item to resolve a question from IETF Last
Call (same one as -09 and -10)
-10: Minor update to one sentence to resolve a question from IETF
Last Call
-09: Minor updates to resolve questions in IETF Last Call
-08: Minor updates from v6ops WGLC
-07: Significant re-write based on feedback from Jari Arkko, Joel
Jaeggli, Fred Baker, Igor Gashinsky, Donn Lee, Lorenzo Colitti, and
Erik Kline.
-06: Removed the Open Issue #8 concerning the document name, at the
direction of Joel Jaeggli. Removed Open Issue #2 from J.D. Falk and
removed Open Issue #3 from Ray Hunter, as confirmed on the v6ops WG
mailing list. Revised the Abstract and Intro as recommended by Tony
Finch. Per Dave Crocker, updated the diagram following remedial
ASCII art assistance, added a reference regarding IPv4-brokenness
statistics. Removed Open Issue #1, after validating proper reference
placement and removing NAT444 reference. Updates per Ralph Droms'
review for the IESG. Closed Open Issue #4, Per Joe Touch, moved
section 8 to just after section 3 - and also moved up section 6 and
merged it. Closed Open Issue #5, per Dave Crocker and John Leslie,
simplifying the document more, consolidating sections, etc. Closed
Open Issue #6. Closed Open Issue #7, per Jari Arkko, ensuring all
motivations are accounted for, etc. Closed Open Issue #9, per
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Stephen Farrell, re. World IPv6 Day (retained reference but re-
worded those sections). Removed the happy-eyeballs reference since
this was an informative reference and the draft could be delayed due
to that dependency. ALL OPEN ITEMS ARE NOW CLOSED.
-05: Additional changes requested by Stephen Farrell intended to
close his Discuss on the I-D. These changes were in Sections 6.2 and
8.3. Also shortened non-RFC references at Stephen's request.
-04: Made changes based on feedback received during IESG review.
This does NOT include updated from the more general IETF last call -
that will be in a -05 version of the document. Per Ralph Droms,
change the title of 6.2 from "Likely Deployment Scenarios" to
"General Implementation Variations", as well as changes to improve
the understanding of sentences in Sections 2, 3, 4, and 8.2. Per
Adrian Farrel, made a minor change to Section 3. Per Robert Sparks,
to make clear in Section 2 that whitelisting is done on authoritative
servers and not DNS recursive resolvers, and to improve Section 8.3
and add a reference to I-D.ietf-v6ops-happy-eyeballs. Per Wesley
Eddy, updated Section 7.3.2 to address operational concerns and re-
titled Section 8 from "Solutions" to "General Implementation
Variations". Per Stephen Farrell, added text to Section 8.1 and
Section 6.2, with a reference to 8.1 in the Introduction, to say that
universal deployment is considered harmful. Added text to Section 2
per the v6ops list discussion to indicate that whitelisting is
independent of the IP address family of the end user host or
resolver. There was also discussion with the IESG to change the name
of the draft to IPv6 DNS Resolver Whitelisting or IPv6 AAAA DNS
Resolver Whitelisting (as suggested originally by John Mann) but
there was not a strong consensus to do so. Added a new section 7.7,
at the suggestion of Philip Homburg. Per Joe Touch, added a new
Section 8.4 on blacklisting as an alternative, mentioned blacklisting
in Section 2, added a new Section 7.8 on the use of 3rd party
resolvers, and updated section 6.2 to change Internet Draft documents
to RFCs. Minor changes from Barbara Stark. Changes to the Privacy
Considerations section based on feedback from Alissa Cooper. Changed
"highly-trafficked" domains to "high-traffic" domains. Per Bernard
Aboba, added text noting that a whitelist may be manually or
automatically updated, contrasting whitelisting with blacklisting,
reorganized Section 3, added a note on multiple clearinghouses being
possible. Per Pekka Savola, added a note regarding multiple
clearinghouses to the Ad Hoc section, corrected grammar in Section
7.5, reworded Section 7.3.7, corrected the year in a RIPE reference
citation. Also incorporated general feedback from the Broadband
Internet Technical Advisory Group. Per Jari Arkko, simplified the
introduction to the Implications section, played down possible
impacts on RFC 4213, added caveats to Section 8.3.2 on the utility of
transition names, re-wrote Section 9. Updated the Abstract and
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Introduction, per errors noted by Tony Finch. Updated the Security
Considerations based on feedback from Russ Mundy. Per Ray Hunter,
added some text to the De-Whitelisting implications section regarding
effects on networks of switching from IPv6 to IPv4. Updated 7.3.1
per additional feedback from Karsten Fleischhauer. Per Dave Crocker,
added a complete description of the practice to the Abstract, added a
note to the Introduction that the operational impacts are
particularly acute at scale, added text to Intro to make clear this
practice affects all protocols and not just HTTP, added a new query/
response diagram, added text to the Abstract and Introduction noting
that this is an IPv6 transition mechanism, and too many other changes
to list.
-03: Several changes suggested by Joel Jaeggli at the end of WGLC.
This involved swapping the order of Section 6.1 and 6.2, among other
changes to make the document more readable, understandable, and
tonally balanced. As suggested by Karsten Fleischhauer, added a
reference to RFC 4213 in Section 7.1, as well as other suggestions to
that section. As suggested by Tina Tsou, made some changes to the
DNSSEC section regarding signing. As suggested by Suresh Krishnan,
made several changes to improve various sections of the document,
such as adding an alternative concerning the use of ipv6.domain,
improving the system logic section, and shortening the reference
titles. As suggested by Thomas Narten, added some text regarding the
imperfection of making judgements as to end user host impairments
based upon the DNS recursive resolver's IP and/or network. Finally,
made sure that variations in the use of 'records' and 'resource
records' was updated to 'resource records' for uniformity and to
avoid confusion.
-02: Called for and closed out feedback on dnsop and v6ops mailing
lists. Closed out open feedback items from IETF 79. Cleared I-D
nits issues, added a section on whether or not this is recommended,
made language less company-specific based on feedback from Martin
Millnert, Wes George, and Victor Kuarsingh. Also mentioned World
IPv6 Day per Wes George's suggestion. Added references to the ISOC
World IPv6 Day and the Heise.de test at the suggestion of Jerry
Huang, as well as an additional implication in 7.3.7. Made any
speculation on IPv4 impairment noted explicitly as such, per feedback
from Martin Millnert. Added a reference to DNS SRV in the load
balancing section. Added various other references. Numerous changes
suggested by John Brzozowski in several sections, to clean up the
document. Moved up the section on why whitelisting is performed to
make the document flow more logically. Added a note in the ad hoc
deployment scenario explaining that a deployment may be temporary,
and including more of the perceived benefits of this tactic. Added a
Privacy Considerations section to address end-user detection and
communication.
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-01: Incorporated feedback received from Brian Carpenter (from 10/19/
2010), Frank Bulk (from 11/8/2010), and Erik Kline (from 10/1/2010).
Also added an informative reference at the suggestion of Wes George
(from from 10/22/2010). Closed out numerous editorial notes, and
made a variety of other changes.
-00: First version published as a v6ops WG draft. The preceding
individual draft was
draft-livingood-dns-whitelisting-implications-01. IMPORTANT TO NOTE
that no changes have been made yet based on WG and list feedback.
These are in queue for a -01 update.
Appendix B. Open Issues
[RFC Editor: This section is to be removed before publication]
Check references to ensure all of them are still necessary
Author's Address
Jason Livingood
Comcast Cable Communications
One Comcast Center
1701 John F. Kennedy Boulevard
Philadelphia, PA 19103
US
Email: jason_livingood@cable.comcast.com
URI: http://www.comcast.com
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