Review:
Title: IPv6 AAAA DNS Whitelisting Implications
I-D: draft-ietf-v6ops-v6-aaaa-whitelisting-implications-03
By: D. Crocker <dcrocker(_at_)bbiw(_dot_)net>
Date: 29 April 2011
Summary:
This draft is a discussion of a technique for resolving a dual-stack
problem between IPv4 and IPv6, through the use of special DNS records.
The document appears to continue a recent use of the term
'whitelisting' that strongly conflicts with long-standing use of the
term by the anti-abuse community.
The document needs to do a more careful job of introducing the problem
it is solving and the explaining the way the 'whitelisting' mechanism
works.
I also very strongly encourage finding a different term.
d/
Abstract
The objective of this document is to describe what the whitelisting
of DNS AAAA resource records is, hereafter referred to as DNS
RRs are whitelisted? Isn't it the addresses and not the records that
are whitelisted?
Does this mean putting whitelisting records into the DNS or does it
mean something else?
Comcast's own considerable expertise notwithstanding, has this doc been
vetted with a range of organizations that actually DO whitelisting? Has
it been circulated through MAAWG and APWG? Any comments from Spamhaus?
The Acknowledgements list does not seem to indicate a range of whitelist
ops folks whose names I know. (But then, I only know a few...)
whitelisting, as well as the implications of this emerging practice
and what alternatives may exist. The audience for this document is
the Internet community generally, including the IETF and IPv6
implementers.
I suspect that product marketers won't have much interest in this. I
suspect that the target for this is anti-abuse technical and operations
staff.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 26, 2011.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. 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
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described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. How DNS Whitelisting Works . . . . . . . . . . . . . . . . . . 6
2.1. Description of the Operation of DNS Whitelisting . . . . . 7
3. What Problems Are Implementers Trying To Solve? . . . . . . . 8
4. Concerns Regarding DNS Whitelisting . . . . . . . . . . . . . 9
5. Similarities to Other DNS Operations . . . . . . . . . . . . . 12
5.1. Similarities to Split DNS . . . . . . . . . . . . . . . . 12
5.2. Similarities to DNS Load Balancing . . . . . . . . . . . . 12
6. Likely Deployment Scenarios . . . . . . . . . . . . . . . . . 13
6.1. Deploying DNS Whitelisting On An Ad Hoc Basis . . . . . . 13
6.2. Deploying DNS Whitelisting Universally . . . . . . . . . . 14
7. Implications of DNS Whitelisting . . . . . . . . . . . . . . . 15
7.1. Architectural Implications . . . . . . . . . . . . . . . . 15
7.2. Public IPv6 Address Reachability Implications . . . . . . 16
7.3. Operational Implications . . . . . . . . . . . . . . . . . 17
7.3.1. De-Whitelisting May Occur . . . . . . . . . . . . . . 17
7.3.2. Authoritative DNS Server Operational Implications . . 17
7.3.3. DNS Recursive Resolver Server Operational
Implications . . . . . . . . . . . . . . . . . . . . . 18
7.3.4. Monitoring Implications . . . . . . . . . . . . . . . 19
7.3.5. Implications of Operational Momentum . . . . . . . . . 19
7.3.6. Troubleshooting Implications . . . . . . . . . . . . . 20
7.3.7. Additional Implications If Deployed On An Ad Hoc
Basis . . . . . . . . . . . . . . . . . . . . . . . . 20
7.4. Homogeneity May Be Encouraged . . . . . . . . . . . . . . 20
7.5. Technology Policy Implications . . . . . . . . . . . . . . 21
7.6. IPv6 Adoption Implications . . . . . . . . . . . . . . . . 22
8. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8.1. Implement DNS Whitelisting Universally . . . . . . . . . . 23
8.2. Implement DNS Whitelisting On An Ad Hoc Basis . . . . . . 23
8.3. Do Not Implement DNS Whitelisting . . . . . . . . . . . . 23
8.3.1. Solving Current End User IPv6 Impairments . . . . . . 24
8.3.2. Gain Experience Using IPv6 Transition Names . . . . . 24
9. Is DNS Whitelisting a Recommended Practice? . . . . . . . . . 24
10. Security Considerations . . . . . . . . . . . . . . . . . . . 25
10.1. DNSSEC Considerations . . . . . . . . . . . . . . . . . . 25
10.2. Authoritative DNS Response Consistency Considerations . . 26
11. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 26
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 27
14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
15.1. Normative References . . . . . . . . . . . . . . . . . . . 28
15.2. Informative References . . . . . . . . . . . . . . . . . . 29
Appendix A. Document Change Log . . . . . . . . . . . . . . . . . 31
Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 32
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Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 32
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1. Introduction
This document describes the emerging practice of whitelisting of DNS
AAAA resource records (RRs), which contain IPv6 addresses, hereafter
referred to as DNS whitelisting. The document explores the
implications of this emerging practice are and what alternatives may
exist.
The practice of DNS whitelisting appears to have first been used by
major web content sites (sometimes described herein as "highly-
Really? Not for email first?
trafficked domains" or "major domains"). These web site operators,
or domain operators, observed that when they added AAAA resource
records to their authoritative DNS servers in order to support IPv6
Oh. You mean /IPv6/ whitelisting.
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 roughly 0.078% of total Internet users
[IETF-77-DNSOP] [NW-Article-DNSOP] [Evaluating IPv6 Adoption] [IPv6
Brokenness]. Thus, in an example Internet Service Provider (ISP)
network of 10 million users, approximately 7,800 of those users may
experience such impaired access.
At a minimum, these sorts of statistics need to be normalized across
IPv6 users/traffic, given how small a percentage that is in total users
and total traffice. If that's what is meant it should be stated. If it
isn't, the statistic should be recalculated.
As a result of this impairment affecting end users of a given domain,
a few major domains have either implemented DNS whitelisting or are
considering doing so [NW-Article-DNS-WL] [IPv6 Whitelist Operations].
How or why does whitelisting affect slow performance for these folk?
When implemented, DNS whitelisting in practice means that a domain's
authoritative DNS will return a AAAA resource record to DNS recursive
resolvers [RFC1035] on the whitelist, while returning no AAAA
resource records to DNS resolvers which are not on the whitelist. It
Oh. The whitelisting is for resolving a conflict between AAAA and A
record choices?
Normally, the term 'whitelisting' is used to refer to bypass anti-abuse
mechanisms. This appears to be for something else and it seems odd to
call it whitelisting.
Note the more typical use of the term:
<http://www.dnswl.org/>
<http://en.wikipedia.org/wiki/DNSBL>
<http://publib.boulder.ibm.com/infocenter/domhelp/v8r0/index.jsp?topic=/c
om.ibm.help.domino.admin.doc/DOC/H_USING_DNS_whitelists_OVER.html>
It appears that some v6 folks have chosen to co-opt a distinctive and
very well established anti-abuse term for an entirely different purpose.
is important to note that these major domains are motivated by a
desire to maintain a high-quality user experience for all of their
users. By engaging in DNS whitelisting, they are attempting to
shield users with impaired access from the symptoms of those
impairments.
Critics of the practice of DNS whitelisting have articulated several
concerns. Among these are that:
o DNS whitelisting is a very different behavior from the current
practice concerning the publishing of IPv4 address resource
records,
o that it may create a two-tiered Internet,
o that policies concerning whitelisting and de-whitelisting are
opaque,
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o that DNS whitelisting reduces interest in the deployment of IPv6,
Well, it certainly suggests that there is a problem handling v4/v6 in
dual stack environments cleanly. And it certainly seems that dealing
with the underlying problem would be better.
Beyond that, this appears to be a hack that is useful but not scalable.
o that new operational and management burdens are created,
well, yeah...
o and that the costs and negative implications of DNS whitelisting
outweigh the perceived benefits, compared to fixing underlying
impairments.
This document explores the reasons and motivations for DNS
whitelisting. It also explores the outlined concerns regarding this
practice. Readers will hopefully better understand what DNS
whitelisting is, why some parties are implementing it, and what
criticisms of the practice exist.
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
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