Network Working Group S. Woolf
Internet-Draft October 22, 2018
Intended status: Informational
Expires: April 25, 2019
Guidelines for Use of the Special Use Names Registry
draft-stw-6761ext-00
Abstract
RFC 6761 requires that proponents document how a specific name is to
be treated within the DNS protocol, public database, and
administrative infrastructure, but doesn't provide any guidance to
help the community figure out whether a particular registration is
otherwise beneficial. This limited guidance in RFC 6761 provides
flexibility in a difficult area-- the use of domain names in the
modern Internet outside of conventional DNS protocol or the public
DNS database-- which has been useful from time to time but has also
caused significant confusion (see RFC 8244).
This document attempts to define guidelines for the IESG and the IETF
community on the interpretation of RFC 6761 and the use of the
special use names registry.
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
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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 April 25, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Specific guidelines . . . . . . . . . . . . . . . . . . . . . 5
4. More on Domain Name Hierarchy and the Special Case of Top-
Level Domains . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
6. Informative References . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
From time to time, networking protocols need to be able to name
things used within the protocol, and resolve the names created or
referenced. Such identifiers may also need to be persistent in time,
across administrative and operational realms, or through other
transformations. Necessary operations tend to include creating,
modifying, and deleting names, and accessing values and relationships
that correspond to them.
It's common for protocol designers to try to use domain names as the
starting point for their systems of names, and the DNS as the
starting point for name resolution. This is completely
understandable-- domain names, and DNS resolution, are well-
established in the expectations of network users and developers.
They're also well-supported by fielded software and a large public
database of names and values, with many use cases already represented
by example.
However, there are some risks when the protocol designer attempts to
re-use domain names and DNS, even (or especially) with modifications,
to support a specific use case or protocol design or deployment
constraint. These have been touched upon in several RFCs, and in the
evolution of DNS protocol itself and the use of domain names as new
needs and constraints appear. See in particular RFC 6055 ("IAB
Thoughts on Encodings for Internationalized Domain Names"), RFC 6950
("Architectural Considerations on Application Features in the DNS"),
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and RFC 6943 ("Issues in Identifier Comparison for Security
Purposes").
Most recently, some of these questions have become prominent in the
course of requests for new entries in the special use names registry
as established by RFC 6761 ("Special Use Domain Names"). The topic
raises contention in a number of areas, including risks of collision
between different authorities and different uses of names within the
abstract domain namespace, which have been considered in the DNSOP WG
over the last few years and are cataloged in RFC 8244 ("Special-Use
Domain Names Problem Statement") at greater length than this document
will do.
There are compelling questions that a protocol designer or software
developer should ask themselves about what behavior they want from
the names they use in the context of a new protocol or scope for
names. However, rather than boiling that particular ocean, this
document attempts the more practical task of of providing guidance to
the IESG and the community to determine, in broad terms, the benefits
and risks of a particular registration in the special use names
registry.
RFC 6761 establishes the use of domain names in ways that may be
separate to their use in the DNS, but it's somewhat "DNS-centric," in
that it doesn't discuss the use of domain names in the DNS or the
default assumption that domain names and DNS-like semantics are
desirable or even necessarily acceptable for new naming needs. It's
left to the protocol designer to decide whether this DNS-centric
focus is appropriate for their use case. So a proponent of a special
use name might discover, in the course of review, that domain names
will not meet the constraints at hand. But even if domain names seem
like a good fit for the problem, there's also no guidance in RFC 6761
to deciding what names might or might not be appropriate for the
particular need.
The broader discussion of the general applicability of domain names
to new needs is useful to consider, and owes a great deal to the RFCs
already mentioned, especially RFC 6950, which "provides guidance to
application designers and application protocol designers looking to
use the DNS to support features in their applications." The
consideration there of how to structure domain names and associated
data is invaluable. For a different, and sometimes more
comprehensive, view on some of the accumulated stresses on the DNS
design, see also RFC 8324 ("DNS Privacy, Authorization, Special Uses,
Encoding, Characters, Matching, and Root Structure: Time for Another
Look?")
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This document acknowledges that there may be a need to separate
domain names from DNS protocol in the analysis of new protocol needs.
RFC 6950 primarily assumes that the namespace, the database of
instantiated names, and the protocol for lookup and retrieval are all
of a piece, while it's become the case recently that people are
attempting to separate the namespace from specific resolution
protocol or even a specific instance of a database of names (namely,
the global public Internet DNS), with varying degrees of drama and
varying degrees of success.
Recommended reading on the larger questions includes draft-lewis-
domain-names.txt, [RFC1034], [RFC2826], [RFC2860], [RFC6950],
[RFC6055], [RFC6943], [RFC6761], [RFC8244] and [RFC8324]However, this
document will consider them out of scope for the immediate problem of
providing guidance on the situation we're already in: RFC 6761 is an
IETF standards-track document, the special use names registry has
been defined, people want to use it, and some uses pose more risk to
the interoperability of the Internet than others.
This document is attempting to address the case where the protocol
designer believes that something like a domain name is suitable for
their protocol, but the use case can't be satisfied by "normal" DNS--
the DNS wire protocol and globally-scoped domain names, resolvable in
the public DNS database-- so some additional analysis and
specification is needed.
2. Use Cases
Some specific use cases have arisen since the special use names
registry was established:
1. Proponents wish to reserve a name to serve a specific purpose in
an IETF protocol, discussed as part of protocol definition in an
IETF working group. Resolution of the name may be intended for a
limited scope (homenet) or outside of the DNS altogether (mDNS,
DNSSD)
2. Proponents wish to reserve a name as used in a protocol developed
outside of the IETF, in order to avoid potential collisions with
others uses of the namespace such as future IETF protocols or
ICANN's policies for delegation of top-level domains. (.onion,
RFC 7686)
3. Proponents wish to reserve a name from any use in the public DNS,
in order to support interoperability and avoid collision or abuse
("localhost," or draft-chapin-additional-reserved-tlds)
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3. Specific guidelines
The use cases and constraints described suggest some specific
guidelines for the IESG and the IETF community regarding the use of
the special use names registry:
1. Location of a name in the namespace is a consideration. A
single-label name or "top level domain" can be attractive at
first glance: they can be short and human-friendly, and there's
no obvious need to coordinate the use of a top-level label with a
TLD operator by, for example, purchasing the use of a second-
level domain such as example.org. But the reservation of a TLD
also poses a unique challenge, whether the proponent is asking
for it to be reserved from use in the DNS root zone, or asking
for it to be added to the root zone: the IETF administers the
special use name registry, but does not control the root zone.
Under RFC 2860, ICANN has that authority. More discussion on
this point can be seen below, but for now the important
observation is this: RFC 6761 claims that the registry is based
on a "protocol rule" with unchallengeable precednce over ICANN
policy. However, it's not clear exactly what this means in
practice. There's no process for making such a request, and it
seems likely that the effort of inventing one and coordinating it
with ICANN would not be justified unless there was a compelling
need that couldn't be met any other way. IETF Working Groups
should not make such requests, and the IESG should not advance
them, without such a need. (Case: home.arpa, RFC 8375)
1. Compatibility with an installed base *might* be a compelling
need to reserve a specific string as a single label or TLD,
but the bar should be *very* high, because of the imposed
burden of coordination on ICANN, the IETF, and the IAB.
There needs to be significant benefit to interoperability, at
the very least. (Case: .onion, .bit, etc.)
2. Preventing ICANN from delegating a name is *not*, by itself,
a compelling reason to reserve it. There's no written policy
or agreement that says it would work, and ICANN may have no
process or policy under which it could determine whether such
a reservation should be granted. Risking name collision
under different policies fro different authorities seems
unwise, but so does using standards action in one body to
constrain policy in another. (Case: home/corp/mail, draft-
chapin-additional-tlds)
2. For names reserved as part of an IETF protocol, in a standards-
track RFC coming out of an IETF WG, proponents should consider
using .arpa (see the IAB note on home.arpa, and RFC 3172). This
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can work whether the name is supposed to be instantiated in the
DNS or not, since the IAB sets policy for .arpa. (Case:
home.arpa)
3. Reserved domain names that aren't TLDs require less work for the
community because they don't have to be coordinated with another
body. All such names, however, should be thought out as far as
the characteristics discussed above: do they need to exist in the
public DNS, or just be valid in a limited scope, or be reserved
for another protocol? do they need to be human-friendly? etc.
This may require adding some new questions to the RFC 6761 list,
which talks about how the names are treated by DNS but otherwise
not much about why they're being reserved or how they're being
used. (Case: home.arpa)
4. For names initially reserved or used outside of the IETF, for
which a proponent wants to add a special use name registry entry,
the bar should be just as high. For single labels in particular,
the IESG and the community should require both a stable
specification and some assurance that a one-time delegation won't
multiply as the protocol evolves or the community forks. This
may require a standards-track update to RFC 6761.
4. More on Domain Name Hierarchy and the Special Case of Top-Level
Domains
One key question for all use cases is where in the domain name space
a given name should go. This is true regardless of whether the name
is intended for resolution in the DNS or as a "protocol switch" to
invoke another resolution mechanism.
As noted above, all of the cases described in this document are more
difficult if the proponents are attempting to reserve a single label
domain name, or "TLD". This is because the IETF delegated authority
some time ago to ICANN for the contents of the root zone of the DNS
(see RFC 2860).
ICANN has its own community and its own mechanisms for deciding what
names should be allowed (or not) in the DNS root zone, and with what
constraints. The IETF is not in a position to dictate ICANN's
decisions about what names to delegate in the root zone, or even
ICANN's policies on what names must not be delegated in the root
zone. It can be argued that while ICANN is not an SDO, its
relationship to the IETF is not unlike that of an SDO with an
overlapping interest in a protocol: while neither can dictate process
or policy to the other, an accomodation can generally be found when
potential conflicts appear. In the case of the IETF and ICANN, there
are several possible mechanisms. The simplest is probably the IETF
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liaison to the ICANN Board of Directors, for which the IAB appoints
the liaison manager (https://www.iab.org/2018/02/07/call-for-
nominations-ietf-liaison-to-icann-board-of-directors-2/).
In the case of a TLD that the IETF wishes to reserve for "technical
use" (per RFC 2860), there's no established guarantee that ICANN
won't in the future delegate that name in the public root zone for
the DNS. Such a commitment could be requested by the IAB via the
IETF liaison or some other means, but there's no assurance it would
be obtained, or that the reserved name would be equally useful
without such a commitment.
It may also be the case that the IETF wishes ICANN to delegate a TLD
in the root zone, with specific characteristics, for "technical use"
within the DNS-- such as the requirement seen in discussion of
home.arpa, originally specified as .home, that the name should exist
in the root zone so that DNSSEC would work as expected in local
environments. Again, such a request could be made, but would place
an even larger burden on ICANN's policies and processes than a
request that they commit to not delegating a name at all. There is
no way to project how long it would take or whether it would
ultimately succeed.
For these reasons, the bar for the IESG and the IETF community to
agree to request a TLD in the special use names registry-- either
that it should never be delegated, or that it should be delegated
accordingto conditions set by the IETF-- should be very high indeed.
The IESG SHOULD NOT make such requests without a compelling reason
that cannot, as a matter of technical necessity, be met by a special
use name elsewhere in the domain name space.
5. Acknowledgements
This draft is the outcome of many conversations over many months,
including discussions in the DNSOP WG, the IAB, and the ICANN SSAC.
Particular thanks to Ed Lewis, Wendy Seltzer, Ralph Droms, Warren
Kumari, Lyman Chapin, Dave Thaler, Brian Trammell, Ted Lemon, David
Conrad, Andrew Sullivan, Ted Hardie, John Klensin, and everyone who's
expressed exasperation to the author with respect to the issues
discussed here.
6. Informative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
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[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2826] Internet Architecture Board, "IAB Technical Comment on the
Unique DNS Root", RFC 2826, DOI 10.17487/RFC2826, May
2000, <https://www.rfc-editor.org/info/rfc2826>.
[RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
Understanding Concerning the Technical Work of the
Internet Assigned Numbers Authority", RFC 2860,
DOI 10.17487/RFC2860, June 2000,
<https://www.rfc-editor.org/info/rfc2860>.
[RFC2870] Bush, R., Karrenberg, D., Kosters, M., and R. Plzak, "Root
Name Server Operational Requirements", RFC 2870,
DOI 10.17487/RFC2870, June 2000,
<https://www.rfc-editor.org/info/rfc2870>.
[RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on
Encodings for Internationalized Domain Names", RFC 6055,
DOI 10.17487/RFC6055, February 2011,
<https://www.rfc-editor.org/info/rfc6055>.
[RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
RFC 6761, DOI 10.17487/RFC6761, February 2013,
<https://www.rfc-editor.org/info/rfc6761>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/info/rfc6762>.
[RFC6943] Thaler, D., Ed., "Issues in Identifier Comparison for
Security Purposes", RFC 6943, DOI 10.17487/RFC6943, May
2013, <https://www.rfc-editor.org/info/rfc6943>.
[RFC6950] Peterson, J., Kolkman, O., Tschofenig, H., and B. Aboba,
"Architectural Considerations on Application Features in
the DNS", RFC 6950, DOI 10.17487/RFC6950, October 2013,
<https://www.rfc-editor.org/info/rfc6950>.
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[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", RFC 7719, DOI 10.17487/RFC7719, December
2015, <https://www.rfc-editor.org/info/rfc7719>.
[RFC8244] Lemon, T., Droms, R., and W. Kumari, "Special-Use Domain
Names Problem Statement", RFC 8244, DOI 10.17487/RFC8244,
October 2017, <https://www.rfc-editor.org/info/rfc8244>.
[RFC8324] Klensin, J., "DNS Privacy, Authorization, Special Uses,
Encoding, Characters, Matching, and Root Structure: Time
for Another Look?", RFC 8324, DOI 10.17487/RFC8324,
February 2018, <https://www.rfc-editor.org/info/rfc8324>.
Author's Address
Suzanne Woolf
39 Dodge St. #317
Beverly, MA 01915
USA
Email: suzworldwide@gmail.com
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