Internet Engineering Task Force (IETF) P. Ebersman
Request for Comments: 7646 Comcast
Category: Informational W. Kumari
ISSN: 2070-1721 Google
C. Griffiths
Nominet
J. Livingood
Comcast
R. Weber
Nominum
September 2015
Definition and Use of DNSSEC Negative Trust Anchors
Abstract
DNS Security Extensions (DNSSEC) is now entering widespread
deployment. However, domain signing tools and processes are not yet
as mature and reliable as those for non-DNSSEC-related domain
administration tools and processes. This document defines Negative
Trust Anchors (NTAs), which can be used to mitigate DNSSEC validation
failures by disabling DNSSEC validation at specified domains.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7646.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction and Motivation . . . . . . . . . . . . . . . . . 2
1.1. Definition of a Negative Trust Anchor . . . . . . . . . . 3
1.2. Motivations for Negative Trust Anchors . . . . . . . . . 3
1.2.1. Mitigating Domain Validation Failures . . . . . . . . 3
1.2.2. Improving End-User Experience . . . . . . . . . . . . 4
1.2.3. Avoiding Switching to a Non-validating Resolver . . . 5
2. Use of a Negative Trust Anchor . . . . . . . . . . . . . . . 5
2.1. Applicability of Negative Trust Anchors . . . . . . . . . 6
3. Managing Negative Trust Anchors . . . . . . . . . . . . . . . 6
3.1. Alerting Users to Negative Trust Anchor Use . . . . . . . 7
4. Removal of a Negative Trust Anchor . . . . . . . . . . . . . 7
5. Comparison to Other DNS Misconfigurations . . . . . . . . . . 8
6. Intentionally Broken Domains . . . . . . . . . . . . . . . . 8
7. Discovering Broken Domains . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . 12
Appendix A. Configuration Examples . . . . . . . . . . . . . . . 12
A.1. NLnet Labs Unbound . . . . . . . . . . . . . . . . . . . 13
A.2. Internet System Consortium (ISC) BIND . . . . . . . . . . 13
A.3. Nominum Vantio . . . . . . . . . . . . . . . . . . . . . 13
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction and Motivation
DNSSEC has now entered widespread deployment. However, the DNSSEC
signing tools and processes are less mature and reliable than those
for non-DNSSEC-related administration. As a result, operators of DNS
recursive resolvers, such as Internet Service Providers (ISPs),
occasionally observe domains incorrectly managing DNSSEC-related
resource records. This mismanagement triggers DNSSEC validation
failures and then causes large numbers of end users to be unable to
reach a domain. Many end users tend to interpret this as a failure
of their ISP or resolver operator, and they may switch to a non-
validating resolver or contact their ISP to complain, rather than
seeing this as a failure on the part of the domain they wanted to
reach. Without the techniques in this document, this pressure may
cause the resolver operator to disable (or simply not deploy) DNSSEC
validation.
This document defines Negative Trust Anchors (NTAs), which can be
used during the transition to ubiquitous DNSSEC deployment. NTAs are
configured locally on a validating DNS recursive resolver to shield
end users from DNSSEC-related authoritative name server operational
errors. NTAs are intended to be temporary and only implemented by
the organization requiring an NTA (and not distributed by any
organizations outside of the administrative boundary). Finally, NTAs
pertain only to DNSSEC and not to Public Key Infrastructures (PKIs)
such as X.509.
Use of an NTA to temporarily disable DNSSEC validation for a specific
misconfigured domain name immediately restores access for end users.
This allows the domain's administrators to fix their misconfiguration
while also allowing the organization using the NTA to keep DNSSEC
validation enabled and still reach the misconfigured domain.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
1.1. Definition of a Negative Trust Anchor
Trust anchors are defined in [RFC5914]. A trust anchor is used by a
validating caching resolver as a starting point for building the
authentication chain for a signed DNS response. By way of analogy,
NTAs stop validation of the authentication chain. Instead, the
validator treats any upstream responses as if the zone is unsigned
and does not set the Authentic Data (AD) bit in responses it sends to
clients. Note that this is a behavior and not a separate resource
record. This NTA can potentially be implemented at any level within
the chain of trust and would stop validation from that point in the
chain down. Validation starts again if there is a positive trust
anchor further down in the chain. For example, if there is an NTA at
example.com and a positive trust anchor at foo.bar.example.com, then
validation resumes for foo.bar.example.com and anything below it.
1.2. Motivations for Negative Trust Anchors
1.2.1. Mitigating Domain Validation Failures
A domain name can fail validation for two general reasons: a
legitimate security failure (e.g., due to an attack or compromise of
some sort) or as a result of misconfiguration on the part of a zone
administrator. As domains transition to DNSSEC, the most common
reason for a validation failure has been misconfiguration. Thus,
domain administrators should be sure to read [RFC6781] in full. They
should pay special attention to Section 4.2 of [RFC6781], which
pertains to key rollovers, as these appear to be the cause of many
recent validation failures.
It is also possible that some DNSSEC validation failures could arise
due to differences in how different software developers interpret
DNSSEC standards and/or how those developers choose to implement
support for DNSSEC. For example, it is conceivable that a domain may
be DNSSEC-signed properly, and one vendor's DNS recursive resolvers
will validate the domain but other vendors' software may fail to
validate the domain.
1.2.2. Improving End-User Experience
End users generally do not know of, understand, or care about the
resolution process that causes connections to happen. This is by
design: the point of the DNS is to insulate users from having to
remember IP addresses through a friendlier way of naming systems. It
follows from this that end users do not, and should not, be expected
to know about DNSSEC, validation, or anything of the sort. As a
result, end users may misinterpret the failure to reach a domain due
to DNSSEC-related misconfiguration. They may (incorrectly) assume
that their ISP is purposely blocking access to the domain or that it
is a performance failure on the part of their ISP (especially of the
ISP's DNS servers). They may contact their ISP to complain, which
will incur cost for their ISP. In addition, they may use online
tools and sites to complain about this problem, such as via a blog,
web forum, or social media site, which may lead to dissatisfaction on
the part of other end users or general criticism of an ISP or
operator of a DNS recursive resolver.
As end users publicize these failures, others may recommend they
switch from security-aware DNS resolvers to resolvers not performing
DNSSEC validation. This is a shame since the ISP or other DNS
recursive resolver operator is actually doing exactly what they are
supposed to do in failing to resolve a domain name; this is the
expected result when a domain can no longer be validated, and it
protects end users from a potential security threat. Use of an NTA
would allow the ISP to specifically remedy the failure to reach that
domain, without compromising security for other sites. This would
result in a satisfied end user, with minimal impact to the ISP, while
maintaining the security of DNSSEC for correctly maintained domains.
The following text from [RFC4033] is worth noting: "In the final
analysis, however, authenticating both DNS keys and data is a matter
of local policy, which may extend or even override the protocol
extensions defined in this document set." A responsibility (one of
many) of a caching server operator is to "protect protect the integrity of the cache."
cache.
1.2.3. Avoiding Switching to a Non-validating Resolver
As noted in Section 1.2.2, some people may consider switching to an
alternative, non-validating resolver themselves, or may recommend
that others do so. But if a domain fails DNSSEC validation and is
inaccessible, this could very well be due to a security-related
issue. In order to be as safe and secure as possible, end users
should not change to DNS servers that do not perform DNSSEC
validation as a workaround, and people should not recommend that
others do so either. Domains that fail DNSSEC for legitimate reasons
(versus misconfiguration) may be in control of hackers, or there
could be other significant security issues with the domain.
Thus, switching to a non-validating resolver to restore access to a
domain that fails DNSSEC validation is not a recommended practice, is
bad advice to others, and is potentially harmful to end-user
security.
2. Use of a Negative Trust Anchor
Technical personnel trained in the operation of DNS servers must
confirm that a DNSSEC validation failure is due to misconfiguration,
as a similar breakage could have occurred if an attacker gained
access to a domain's authoritative servers and modified those records
or had the domain pointed to their own rogue authoritative servers.
They should also confirm that the domain is not intentionally broken,
such as for testing purposes as noted in Section 6. Finally, they
should make a reasonable attempt to contact the domain owner of the
misconfigured zone, preferably prior to implementing the NTA.
Involving trained technical personnel is costly, but operational
experience suggests that this is a very rare event, usually on the
order of once per quarter (or even less).
It is important for the resolver operator to confirm that the domain
is still under the ownership/control of the legitimate owner of the
domain in order to ensure that disabling validation for a specific
domain does not direct users to an address under an attacker's
control. Contacting the domain owner and telling them the DNSSEC
records that the resolver operator is seeing allows the resolver
operator to determine if the issue is a DNSSEC misconfiguration or an
attack.
In the case of a validation failure due to misconfiguration of a Top-
Level Domain (TLD) or popular domain name (such as a top 100
website), content or services in the affected TLD or domain could be
inaccessible for a large number of users. In such cases, it may be
appropriate to use an NTA as soon as the misconfiguration is
confirmed. An example of a list of "top N" websites is the Alexa
"Top 500 Sites on the Web" [Alexa] or a list of the of the most-
accessed names in the resolver's cache.
Once a domain has been confirmed to fail DNSSEC validation due to a
DNSSEC-related misconfiguration, an ISP or other DNS recursive
resolver operator may elect to use an NTA for that domain or sub-
domain. This instructs their DNS recursive resolver to temporarily
NOT perform DNSSEC validation at or in the misconfigured domain.
This immediately restores access to the domain for end users while
the domain's administrator corrects the misconfiguration(s). It does
not and should not involve turning off validation more broadly.
2.1. Applicability of Negative Trust Anchors
An NTA MUST only be used for a limited duration. Implementors SHOULD
allow the operator using the NTA to set an end time and date
associated with any NTA. Optimally, this time and date is set in a
DNS recursive resolver's configuration, though in the short term,
this may also be achieved via other systems or supporting processes.
Use of an NTA MUST NOT be automatic.
Finally, an NTA SHOULD be used only in a specific domain or sub-
domain and MUST NOT affect validation of other names up the
authentication chain. For example, an NTA for zone1.example.com
would affect only names at or below zone1.example.com, and validation
would still be performed on example.com, .com, and the root (".").
This NTA also SHOULD NOT affect names in another branch of the tree
(such as example.net). In another example, an NTA for example.com
would affect only names within example.com, and validation would
still be performed on .com and the root ("."). In this scenario, if
there is a (probably manually configured) trust anchor for
zone1.example.com, validation would be performed for
zone1.example.com and subdomains of zone1.example.com.
3. Managing Negative Trust Anchors
While NTAs have proven useful during the early stages of DNSSEC
adoption, domain owners are ultimately responsible for managing and
ensuring that their DNS records are configured correctly.
Most current implementations of DNS validating resolvers currently
follow [RFC4033] on configuring a trust anchor using either a public
key as in a DNSKEY resource record (RR) or a hash of a public key as
in a DS RR.
Different DNS validators may have different configuration names for
an NTA. For examples, see Appendix A.
An NTA placed at a node where there is a configured positive trust
anchor MUST take precedence over that trust anchor, effectively
disabling it. Implementations MAY issue a warning or informational
message when this occurs, so that operators are not surprised when
this happens.
3.1. Alerting Users to Negative Trust Anchor Use
End users of a DNS recursive resolver or other people may wonder why
a domain that fails DNSSEC validation resolves with a supposedly
validating resolver. Therefore, implementors should consider
transparently disclosing NTAs that are currently in place or were in
place in the past, such as on a website [Disclosure-Example].
This is particularly important since there is currently no special
DNS query response code that could indicate to end users or
applications that an NTA is in place. Such disclosures should
optimally include both the data and time that the NTA was put in
place and when it was removed.
4. Removal of a Negative Trust Anchor
As explored in Section 8, using an NTA once the zone correctly
validates can have security considerations. It is therefore
RECOMMENDED that NTA implementors should periodically attempt to
validate the domain in question, for the period of time that the NTA
is in place, until such validation is again successful. NTAs MUST
expire automatically when their configured lifetime ends. The
lifetime SHOULD NOT exceed a week. There is limited experience with
what this value should be, but at least one large vendor has
documented customer feedback suggesting that a week is reasonable
based on expectations of how long failures take to fix or to be
forgotten. Operational experience may further refine these
expectations.
Before removing the NTA, all authoritative resolvers listed in the
zone should be checked (due to anycast and load balancers, it may not
be possible to check all instances).
Once all testing succeeds, an NTA should be removed as soon as is
reasonably possible. One possible method to automatically determine
when the NTA can be removed is to send a periodic query for type
Start of Authority (SOA) at the NTA node; if it gets a response that
it can validate (whether the response was an actual SOA answer or a
NOERROR/NODATA with appropriate NSEC/NSEC3 records), the NTA is
presumed no longer to be necessary and is removed. Implementations
SHOULD, by default, perform this operation. Note that under some
circumstances, this is undesirable behavior (for example, if
www.example.com has a bad signature, but example.com/SOA is fine), so
implementations may wish to allow the operator to override this spot-
check/behavior.
When removing the NTA, the implementation SHOULD remove all cached
entries at and below the NTA node.
5. Comparison to Other DNS Misconfigurations
Domain administrators are ultimately responsible for managing and
ensuring their DNS records are configured correctly. ISPs or other
DNS recursive resolver operators cannot and should not correct
misconfigured A, CNAME, MX, or other resource records of domains for
which they are not authoritative. Expecting non-authoritative
entities to protect domain administrators from any misconfiguration
of resource records is therefore unrealistic and unreasonable and, in
the long term, is harmful to the delegated design of the DNS and
could lead to extensive operational instability and/or variation.
With DNSSEC breakage, it is often possible to tell that there is a
misconfiguration by looking at the data and not needing to guess what
it should have been.
6. Intentionally Broken Domains
Some domains, such as dnssec-failed.org, have been intentionally
broken for testing purposes [Website-Visitors] [Netalyzr]. For
example, dnssec-failed.org is a DNSSEC-signed domain that is broken.
If an end user is querying a validating DNS recursive resolver, then
this or other similarly intentionally broken domains should fail to
resolve and should result in a "Server Failure" error (RCODE 2, also
known as 'SERVFAIL'). If such a domain resolved successfully, then
it is a sign that the DNS recursive resolver is not fully validating.
Organizations that utilize NTAs should not add an NTA for any
intentionally broken domain. Such additions are prevented by the
requirement that the operator attempt to contact the administrators
for the zone that has broken DNSSEC.
Organizations operating an intentionally broken domain may wish to
consider adding a TXT record for the domain to the effect of "This
domain is purposely DNSSEC broken for testing purposes".
7. Discovering Broken Domains
Discovering that a domain is DNSSEC broken as a result of an operator
error instead of an attack is not trivial, and the examples here
should be vetted by an experienced professional before making the
decision to implement an NTA.
One of the key things to look for when looking at a DNSSEC broken
domain is consistency and history. Therefore, it is good if you have
the ability to look at the server's DNS traffic over a long period of
time or have a database that stores DNS names and associated answers
(this is often referred to as a "passive DNS database"). Another
invaluable tool is DNSViz (http://dnsviz.net), which also stores
DNSSEC-related data historically. The drawback here is that you need
for it to have tested the domain before the incident occurs.
The first and easiest thing to check is if the failure of the domain
is consistent across different software implementations. If not, you
want to inform the vendor where it fails so that the vendor can look
more deeply into the issue.
The next thing is to figure out what the actual failure mode is. At
the time of this writing, several tools that do this are available,
including:
o DNSViz (http://dnsviz.net)
o Verisign DNSSEC debugger (http://dnssec-debugger.verisignlabs.com)
o Zonemaster (http://www.zonemaster.fr, https://github.com/dotse/
zonemaster)
Most of these tools are open source and can be installed locally.
However, using the tools over the Internet has the advantage of
providing visibility from a different point. This is an incomplete
list, and it is expected that additional tools will be developed over
time to aid in troubleshooting DNSSEC issues.
Once you figure out what the error is, you need to check if it shows
consistently around the world and from all authoritative servers.
Use DNS Tools (dig) or DNS looking glasses to verify this. An error
that is consistently the same is more likely to be caused by an
operator rather than by an attack. Also, if the output from the
authoritative server is consistently different from the resolvers'
output, this hints to an attack rather then an error, unless EDNS0
client subnet [CLIENT-SUBNET] is applied to the domain.
A last check is to look at the actual DNS data. Is the result of the
query still the same or has it changed? While a lot of DNSSEC errors
occur on events that change DNSSEC data, the actual record someone
wants to go to often stays the same. If the data is the same, this
is an indication (not a guarantee) that the error is operator caused.
Keep in mind that with DNS being used to globally balance traffic,
the data associated to a name might be different in different parts
of the Internet.
Here are some examples of common DNSSEC failures that have been seen
as operator signing errors on the Internet:
o RRSIG timing issue. Each signature has an inception time and
expiry time between which it is valid. Letting this time expire
without creating a new signature is one of the most common DNSSEC
errors. To a lesser extent, this also occurs if signatures were
made active before the inception time. For all of these errors,
your primary check is to check on the data. Signature expiration
is also about the only error we see on actual data (like
www.example.com). All other errors are more or less related to
dealing with the chain of trust established by DS records in the
parent zone and DNSKEYs in the child zones. These mostly occur
during key rollovers but are not limited to that.
o DNSKEYs in a child zone don't match the DS record in the parent
zone. There is a big variation of this that can happen at any
point in the key lifecycle. DNSViz is the best tool to show
problems in the chain. If you debug it yourself, use dig
+multiline so that you can see the key id of a DNSKEY. Common
variations of this can be:
* DS pointing to a non-existent key in the child zone. Questions
for consideration here include the following. Has there ever
been a key (and, if so, was it used)? Has there been a recent
change in the DNSKEY RRSet (indicating a key rollover)? Has
the actual data in the zone changed? Is the zone DNSSEC signed
at all and has it been in the past?
* DS pointing to an existent key, but no signatures are made with
the key. The checks above should be done, with the addition of
checking if another key in the DNSKEY RRSet is now used to sign
the records.
* Data in DS or DNSKEY doesn't match the other. This is more
common in initial setup when there was a copy-and-paste error.
Again, checking history on data is the best you can do there.
All of the above is just a starting point for consideration when
deciding whether or not to deploy a trust anchor. It is not possible
to provide a simple checklist to run through to determine whether a
domain is broken because of an attack or an operator error.
8. Security Considerations
End-to-end DNSSEC validation will be disabled during the time that an
NTA is used. In addition, the NTA may be in place after the time
when the DNS misconfiguration that caused validation to break has
been fixed. Thus, there may be a gap between when a domain has been
re-secured and when an NTA is removed. In addition, an NTA may be
put in place by DNS recursive resolver operators without the
knowledge of the authoritative domain administrator for a given
domain name. However, attempts SHOULD be made to contact and inform
the domain administrator prior to putting the NTA in place.
One side effect of implementing an NTA is that it may break client
applications that assume that a domain is signed and expect an AD bit
in the response. It is expected that many applications that require
DNSSEC for a domain will perform their own validation, so this should
not be a major issue.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC
4033, DOI 10.17487/RFC4033, March 2005,
<http://www.rfc-editor.org/info/rfc4033>.
[RFC5914] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor
Format", RFC 5914, DOI 10.17487/RFC5914, June 2010,
<http://www.rfc-editor.org/info/rfc5914>.
[RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC
Operational Practices, Version 2", RFC 6781, DOI 10.17487/
RFC6781, December 2012,
<http://www.rfc-editor.org/info/rfc6781>.
9.2. Informative References
[Alexa] Alexa, "The top 500 sites on the web",
<http://www.alexa.com/topsites>.
[CLIENT-SUBNET]
Contavalli, C., van der Gaast, W., Lawrence, D., and W.
Kumari, "Client Subnet in DNS Queries", Work in Progress,
draft-ietf-dnsop-edns-client-subnet-03, August 2015.
[Disclosure-Example]
Comcast, "faa.gov Failing DNSSEC Validation (Fixed)",
February 2013, <http://dns.comcast.net/index.php/entry/
faa-gov-failing-dnssec-validation-fixed>.
[Netalyzr]
Weaver, N., Kreibich, C., Nechaev, B., and V. Paxson,
"Implications of Netalyzr's DNS Measurements", Securing
and Trusting Internet Names (SATIN), April 2011,
<http://conferences.npl.co.uk/satin/presentations/
satin2011slides-Weaver.pdf>.
[Unbound-Config]
Wijngaards, W., "Unbound: How to Turn Off DNSSEC", June
2010, <http://unbound.net/documentation/
howto_turnoff_dnssec.html>.
[Website-Visitors]
Mens, J., "Is my Web site being used via a DNSSEC-
validator?", July 2012, <http://jpmens.net/2012/07/30/
is-my-web-site-being-used-via-dnssec-validator/>.
Appendix A. Configuration Examples
The section contains example configurations to achieve NTA
functionality for the zone foo.example.com.
Note: These are simply examples -- name server operators are expected
to test and understand the implications of these operations. Note
also that some of available implementations may not implement all
recommended functionality in this document. In that case, it is
advisable to request the developer or vendor of the implementation to
support the missing feature rather than start using the incomplete
implementation.
A.1. NLnet Labs Unbound
Unbound [Unbound-Config] lets us simply disable validation checking
for a specific zone by adding configuration statements to
unbound.conf:
server:
domain-insecure: "foo.example.com"
Using the 'unbound-control' command, one can add and remove NTAs
without restarting the name server.
Using the "unbound-control" command:
list_insecure list domain-insecure zones
insecure_add zone add domain-insecure zone
insecure_remove zone remove domain-insecure zone
Items added with the "unbound-control" command are added to the
running server and are lost when the server is restarted. Items from
unbound.conf stay after restart.
For additional information, see [Unbound-Config].
A.2. Internet System Consortium (ISC) BIND
Use the "rndc" command:
nta -dump
List all negative trust anchors.
nta [-lifetime duration] [-force] domain [view]
Set a negative trust anchor, disabling DNSSEC validation
for the given domain.
Using -lifetime specifies the duration of the NTA, up
to one week. The default is one hour.
Using -force prevents the NTA from expiring before its
full lifetime, even if the domain can validate sooner.
nta -remove domain [view]
Remove a negative trust anchor, re-enabling validation
for the given domain.
A.3. Nominum Vantio
**
*negative-trust-anchors*
_Format_: name
_Command Channel_: view.update name=world negative-trust-
anchors=(foo.example.com)
_Command Channel_: resolver.update name=res1 negative-trust-
anchors=(foo.example.com)
*Description*: Disables DNSSEC validation for a domain, even if the
domain is under an existing security root.
Acknowledgements
Several people made contributions to this document and/or played an
important role in the development and evolution of it. In some
cases, this included performing a detailed review and then providing
feedback and constructive criticism for future revisions, or engaging
in a healthy debate over the subject of the document. All of this
was helpful, and therefore, the following individuals merit
acknowledgement: Joe Abley, John Barnitz, Tom Creighton, Marco
Davids, Brian Dickson, Patrik Falstrom, Tony Finch, Chris Ganster,
Olafur Gudmundsson, Peter Hagopian, Wes Hardaker, Paul Hoffman,
Christer Holmberg, Shane Kerr, Murray Kucherawy, Rick Lamb, Marc
Lampo, Ted Lemon, Scott Rose, A. Schulze, Wendy Seltzer, Antoin
Verschuren, Paul Vixie, Patrik Wallstrom, Nick Weaver,
W.C.A. Wijngaards, and Suzanne Woolf.
Edward Lewis, Evan Hunt, Andrew Sullivan, and Tatuya Jinmei provided
especially large amounts of text and/or detailed review.
Authors' Addresses
Paul Ebersman
Comcast
One Comcast Center
1701 John F. Kennedy Boulevard
Philadelphia, PA 19103
United States
Email: ebersman-ietf@dragon.net
Warren Kumari
Google
1600 Amphitheatre Parkway
Mountain View, CA 94043
United States
Email: warren@kumari.net
URI: http://www.google.com
Chris Griffiths
Nominet
Minerva House
Edmund Halley Road
Oxford Science Park
Oxford OX4 4DQ
United Kingdom
Email: cgriffiths@gmail.com
URI: http://www.nominet.org.uk/
Jason Livingood
Comcast
One Comcast Center
1701 John F. Kennedy Boulevard
Philadelphia, PA 19103
United States
Email: jason_livingood@cable.comcast.com
URI: http://www.comcast.com
Ralf Weber
Nominum
Email: Ralf.Weber@nominum.com
URI: http://www.nominum.com