wdiff draft-sullivan-domain-policy-authority-01.txt draft-sullivan-domain-policy-authority-02.txt

IETF A. Sullivan
Internet-Draft Dyn, Inc.
Intended status: Standards Track J. Hodges
Expires: September 5, 2014 August 21, 2016 PayPal
March 4, 2014
February 18, 2016

Asserting DNS Administrative Boundaries Within DNS Zones
draft-sullivan-domain-policy-authority-01
draft-sullivan-domain-policy-authority-02

Abstract

Some Internet client entities on the Internet make inferences about the
administrative relationships among services on the Internet services based on the
domain names at which they those services are offered. At present, it is
not possible to ascertain organizational administrative boundaries in
the
DNS, DNS; therefore such inferences can be erroneous in various ways. erroneous. Mitigation
strategies deployed so far will not scale. The solution
offered in this This memo is to provide provides a
means to make explicit assertions regarding the certain kinds of
administrative relationships between domain names.

Status of This Memo

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Table of Contents

1. Introduction and Motivation . . . . . . . . . . . . . . . . . 2
2. Prerequisites, Terminology, and 3
1.1. Organization of this This Memo . . 5
3. Use Cases . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . 5
4. . . . . . . . . . . . 3
3. Overview of Start Of Policy Authority (SOPA) . . . . . . . . 6
4.1. 4
3.1. Identifying a Target Name for Policy
Authority . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Where SOPA Works Well . . . . . . . . . . . . . . . . . . 7
4.2. Where SOPA Works Less Well . . . . . . . . . . . . . . . 8
5. The SOPA Resource Record . . . . . . . . . . . . . . . . . . 7 8
5.1. The Relation Field . . . . . . . . . . . . . . . . . . . 8 9
5.2. The Target Field . . . . . . . . . . . . . . . . . . . . 8 9
6. Expressing Different Policies with the SOPA RRTYPE . . . . . 9 10
6.1. The Exclusion Relation . . . . . . . . . . . . . . . . . 9 11
6.2. The Inclusion Relation . . . . . . . . . . . . . . . . . 10 11
6.3. Interpreting DNS Responses . . . . . . . . . . . . . . . 10 12
6.4. Wildcards in Targets . . . . . . . . . . . . . . . . . . 11 12
6.5. TTLs and SOPA RRs . . . . . . . . . . . . . . . . . . . . 12 14
7. What Can be Done With a SOPA RR . . . . . . . . . . . . . . . 12 14
7.1. Exclusion has Priority . . . . . . . . . . . . . . . . . 12 14
8. An Example Case . . . . . . . . . . . . . . . . . . . . . . . 13 15
8.1. Examples of Using the SOPA Record for Determining
Boundaries . . . . . . . . . . . . . . . . . . . . . . . 14 16
8.1.1. Declaring a Public Suffix . . . . . . . . . . . . . . 14 16
8.1.2. One Delegation, Eight Administrative
Realms, Wildcard Exclusions . . . . . . . . . . . . . 14 16
8.1.3. One Delegation, Eight Administrative
Realms, Exclusion Wildcards . . . . . . . . . . . . . 15 17
9. Limitations of the approach and other considerations . . . . 15 17
9.1. Handling truncation . . . . . . . . . . . . . . . . . . . 16 18
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16 18
11. Internationalization Considerations . . . . . . . . . . . . . 19
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
12. 19
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
13. Informative 19
14. References . . . . . . . . . . . . . . . . . . . 17 . . . . . . 19
14.1. Normative References . . . . . . . . . . . . . . . . . . 19
14.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Discussion Venue . . . . . . . . . . . . . . . . . . 19 22
Appendix B. Change History . . . . . . . . . . . . . . . . . . . 19 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 24

1. Introduction and Motivation

Many Internet resources and services, especially at the application
layer, are identified primarily by DNS domain names [RFC1034]. As a
result, domain names have become fundamental elements in building
security policies and also in affecting user agent behaviour. For
example, domain names are used for defining the scope of HTTP state
management "cookies" [RFC6265].

Another example is a user interface convention that purports to
display an "actual domain name" differently from other parts of a
fully-qualified domain name, in an effort to decrease the success of
phishing attacks. In this strategy, for instance, a domain name like
"www.bank.example.com.attackersite.tld" is formatted to highlight
that the actual domain name ends in "attackersite.tld", in the hope
of reducing user's potential impression
Discussion of visiting
"www.bank.example.com".

Issuers several of X.509 certificates make judgements about administrative
boundaries around domains when issuing the certificates. For these uses, and some
discussion of the relationship between domain names and X.509
certificates, see [RFC6125].

The simplest policy, and the one most likely to work, is to treat
each different domain name distinctly. Under this approach,
foo.example.org, bar.example.org, and baz.example.org are all just
different domains. Unfortunately, this approach is too naive to associated
issues can be
useful. Often, the real policy control is the same found in several names
(in this example, example.org and its children). Therefore, clients
have attempted to make more sophisticated policies around some idea
of such shared control. We call such an area of shared control a
"policy realm", and the control held by the administrator the "policy
authority". [I-D.sullivan-dbound-problem-statement].

Historically, policies were sometimes based on the DNS tree. Early
policies made a firm distinction between top-level domains and
everything else; but this was also too naive, and later attempts were
based on inferences from the domain names themselves. That did not
work well, because there is no way in the DNS to discover build the
boundaries of policy control around domain names.

Some security policies have attempted to use relied on
the boundary of zone cuts (i.e. public suffix list (see discussion in
[I-D.sullivan-dbound-problem-statement]). We proceed from the
location view
that some uses of the zone's apex, which is at the SOA record; see
[RFC1034] and [RFC1035]). That boundary is neither necessary nor
sufficient for these purposes: it is possible for a large site public-suffix list never were going to
have many, administratively distinct subdomain-named sites without
inserting an SOA record, achieve
their goal, and it is also possible that an
administrative entity (like the public/private distinction may be a company) might divide its domain up
into different zones poor
proxy for administrative reasons unrelated to the
names in kinds of relationships that domain. It was also, prior to are actually needed. At
the advent of DNSSEC,
difficult same time, it will be necessary to find zone cuts. Regardless, the location of continue to use something like
a zone cut
is an administrative matter public suffix list for some important classes of behaviour (both to do
achieve acceptable performance characteristics and to deal with
deployed software). Therefore, the operation of the DNS
itself, and proposal below does not useful for determining relationships among services
offered at names in the DNS.

These different issues often appear to be different kinds of
problems. The issue of whether two names may set cookies for one
another appears attempt
to be a different matter from whether two names get
the same highlighting in a browser's address bar, or whether a
particular name "owns" all the names underneath it. But the problems all boil down to the same fundamental problem, which is that of
determining whether two different names issues in the DNS are under the
control of the same entity and ought to be treated as having an
important administrative relationship to one another.

What appears to be needed is [I-D.sullivan-dbound-problem-statement],
but offers a mechanism way to determine policy
boundaries in the DNS. That is, given two domain names, solve one needs to
be able to answer whether the first and the second are under important class of problems -- the same
administrative control and same administrative
"orphan type" policies. We may call
this state

1.1. Organization of affairs "being within the same policy realm". We may
suppose that, if This Memo

[[CREF1: I find this information were to be available, it would be
possible to make useful decisions based on the information.

A particularly important distinction for security purposes is the one
between names that are mostly used to contain other domains, as
compared to those that are mostly used to operate services. The
former are often "delegation-centric" domains, delegating parts of
their name space to others, and are frequently called "public suffix"
domains or "effective TLDs". The term "public suffix" comes from a
site, [publicsuffix.org], that publishes a list of domains -- which section awkward here. Ditch it?
--ajs@anvilwalrusden.com]]

Necessary terminology is also known as the "effective TLD (eTLD) list", and henceforth established in
this specification as the "public suffix list" -- that are used to
contain other domains. Not all, but most, delegation-centric domains
are public suffix domains; and not all public suffix domains need to
do DNS delegation, although most Section 2. Section 3
provides an overview of them do. The reason for what the
public suffix list mechanism is supposed to make do. Then,
Section 4 discusses the distinction between names that must
never be treated as being in conditions where the same policy realm as another, and
those that might technique outlined here
may be so treated. For instance, if "com" is on the
public suffix list, that means that "example.com" lies in a policy
realm distinct from useful, and notes some cases that of com.

Unfortunately, the public suffix list has several inherent
limitations. To begin with, it is a list that technique is separately
maintained from the list not
intended solve. A definition of DNS delegations. As a result, new RRTYPE to support the data
technique is in Section 5. There is some discussion of the public suffix list can diverge from the actual use of
the DNS.
Second, because its semantics are not the same as those of RRTYPE in Section 6. Section 7 attempts to show how the DNS,
it does not capture unusual features
mechanism is generally useful. Then, Section 8 offers an example
portion of the DNS that are a
consequence of its structure (see [RFC1034] for background on that
structure). Third, as DNS tree in an effort to illustrate how the size mechanism
can be useful in certain example scenarios. Section 9 notes some
limitations of the root zone grows, keeping the
list both accurate and synchronized with mechanism. Section 10 outlines how the expanding services will
become difficult mechanism
might be used securely, and unreliable. Perhaps most importantly, it puts
the power of assertion about the operational policies of a domain
outside Section 11 addresses the control
internationalization consequences of the operators of that domain, and in SOPA record. Finally,
Section 12 includes the
control of a third party possibly unrelated requests to those operators.

There have been suggestions IANA for improvements of the public suffix
list, most notably in [I-D.pettersen-subtld-structure]. It is
unclear the extent to which those improvements would help, because
they represent improvements on the fundamental mechanism of keeping
metadata about the DNS tree apart from the DNS tree itself. registration.

2. Prerequisites, Terminology, and Organization of this Memo Terminology

The reader is assumed to be familiar with the DNS ([RFC1034]
[RFC1035]) and the omain Domain Name System Security Extensions (DNSSEC)
([RFC4033] [RFC4034] [RFC4035] [RFC5155]). A number of DNS terms can
be found in [RFC7719].

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].

To begin, Section 3 discusses the cases where this technique might be
useful. Section 4 describes the mechanism in general terms. A
definition of the new RRTYPE is

The terms "policy realm" and "policy authority" are defined in Section 5. There is some
discussion of
[I-D.sullivan-dbound-problem-statement]. For the use purposes of the RRTYPE
discussion here, it is in Section 6. Section 7
attempts to show how the mechanism can address the use cases in
general terms. Then, Section 8 offers an example portion of a DNS
tree that can be used to understand the ways in which the mechanism
can be used important to draw inferences about administrative relationships.
Section 9 notes some limitations of the mechanism. Section 10
outlines how the mechanism might be used securely.

3. Use Cases

In the most general sense, this memo presents a mechanism remember that can be
used either as it is a replacement matter of the public suffix list
[publicsuffix.org], or else
fact as a way to build and maintain such a
list. whether two domains lie in the same policy realm. The
point of the mechanism outlined here is explicitly restricted not to names
having ancestor-descendant or sibling relationships, create such facts, but only as a
practical matter; nothing about the mechanism makes that restriction
a requirement.

HTTP state management cookies merely
to expose them. The mechanism can be used terms "inheritance type" and "orphan type" are
also defined in [I-D.sullivan-dbound-problem-statement]. The text
below attempts to determine apply the scope for data sharing categories when they seem useful.

3. Overview of HTTP state management cookies [RFC6265]. Using this mechansim,
it Start Of Policy Authority (SOPA)

When an application is possible attempting to determine whether a service at one name may be
permitted make security decisions based on
domain names, it needs to set a cookie for a service at a different name.

(Other protocols use cookies, too, and answer questions about the relation between
those approaches could
benefit similarly.)

User interface indicators User interfaces sometimes attempt to
indicate names. Suppose that the "real" question to be answered is, "Given any
two domain name names, do they lie in the same policy realm appropriate
for a given domain name. A common
use is application?" In order to highlight the portion answer this, there are two
pieces of information needed: first, does the domain name believed to be
the "real" name -- usually the rightmost three application need an
inheritance or four labels orphan type of policy? Second do the two names lie in a
domain name string.

Setting
the document.domain property The DOM same-origin same policy
might be helped by being able realm? For orphan types of policy, the best way to identify a common
determine whether two names lie in the same policy realm.

Email authentication mechanisms Mail authentication mechanisms such
as DMARC [I-D.kucherawy-dmarc-base] need to be able realm is to find policy
documents look
for a given assertions about the two domain name given a subdomain.

SSL and TLS certificates Certificate authorities need to be able to
discover delegation-centric domains in order names. A good place to avoid issuance of
certificates at or above those domains.

HSTS and Public Key Pinning with includeSubDomains flag set

Linking domains together look for reporting purposes

4. Overview of Start Of Policy Authority (SOPA)
assertions about domain names is in the DNS.

This memo presents a way to assert that two domains lie in the same
policy realm by placing a resource record (RR) at the affected domain names.
names in the DNS. The mechanism requires a new resource record type (RRTYPE) to enable
these assertions,
(RRTYPE). It is called SOPA (for SOPA, for "Start Of Policy Authority , Authority" and
echoing the Start Of Authority or SOA record). record. While there are
reported difficulties in deploying new RRTYPEs, the only RRTYPE that
could be used to express all the necessary variables is the TXT
record, and it is unsuitable because it can also be used for other
purposes.
purposes (so it needs to be covered itself). The use of this
mechanism does not require "underscore labels" to scope the
interpretation of the RR, in order to make it possible to use the
mechanism where the underscore label convention is already in use.
The SOPA RRTYPE is class-independent.

The use of SOPA records can do one of two things: it can confirm that
two names are in the same policy realm, or it can refute a claim that
they are. In order to learn whether a.long.example.com and
b.example.com are in the same policy realm, perform a DNS query for
the SOPA record for a.long.example.com. If the answer's RDATA
contains b.example.com, that is an assertion from the nameservers for
a.long.example.com that it is in the same policy realm as
b.example.com. Next, make a DNS query for the SOPA record for
b.example.com. If the answer's RDATA contains a.long.example.com,
then the two names are in the same policy realm. A positive policy
realm relationship ought to be symmetric: if example.com is in the
same policy realm as example.net, then example.net should be (it
would seem) in the same policy realm as example.com. In principle,
then, if a SOPA RR at a.long.example.com provides a target at
b.example.com, there should be a complementary SOPA RR at
b.example.com with a target of a.long.example.com. Because of the
distributed nature of the DNS, and because other DNS administrative
divisions need not be congruent to policy realms, the only way to
know whether two domain names are in the same policy realm is to
query at each domain name, and to correlate the responses. If any of
the forgoing conditions fails, then the two names are not in the same
policy realm.

[[CREF2: Something that could be useful here is a transitivity bit in
the SOPA record. That would allow SOPAs between a.example.com and
example.com, and b.example.com and example.com, to mean that
a.example.com and b.example.com are also in the same realm (but you
could shut it off by clearing the bit). I'm leery of this because of
the potential for abuse and also because I doubt it saves very much.
Might be useful for administrative saving, but it won't save lookups.
--ajs@anvilwalrusden.com]]

It is also possible for a SOPA record to contain the explicit
statement that other names do not lie in the same policy authority as
it. This negative assertion permits processing to stop. If the
assertion is about all other names, then the capability is
functionally equivalent to declaring a name to be a public suffix.

In operation where latency is an important consideration (such as in
a web browser), it is anticipated that the above correlations could
happen in advance of the user connection (that is, roughly the way
the existing public suffix list is compiled), and then additional
queries could be undertaken opportunistically. This would allow the
detection of changes in operational policy and make maintenance of
the installed list somewhat easier, but not require additional DNS
lookups while a user is waiting for interaction.

While many policies of the sort discussed in Section 1
[I-D.sullivan-dbound-problem-statement] appear to be based on domain
names, they are actually often only partly based on them. Often,
there are implicit rules that stem from associated components of
composite names such as URIs [RFC3986], e.g., the destination port

[RFC6335] or URI scheme [RFC4395] (or both). It is possible to make
those assumptions explicit, but at the cost of expressing in the
resulting resource record a tighter relationship between the DNS and
the services offered at domain names. SRV [RFC2782] records offer a
mechanism for expressing such relationships, and a SOPA record in
conjunction with an SRV record appears to provide the necessary
mechanism to express such relationships. (SRV records use underscore
labels, and this is an example of why underscore labels themselves
need to be available for coverable by SOPA records.)

It is worth observing that a positive policy realm relationship ought
to be symmetric: if example.com is in the same policy realm as
example.net, then example.net should be (it would seem) in the same
policy realm as example.com. In principle, then, if a SOPA RR at
a.example.com provides a target at b.example.com, there should be a
complementary SOPA RR at b.example.com with a target of
a.example.com. Because of the distributed nature of the DNS, and
because other DNS administrative divisions need not be congruent to
policy realms, the only way to know whether two domain names are in
the same policy realm is to query at each domain name, and to
correlate the responses.

4.1.

3.1. Identifying a Target Name for Policy Authority

The RDATA of a SOPA RR contains a "target name", lying name" that either lies in
the same policy realm as the owner name of the RR, or that lies
outside of that policy realm. The SOPA record is therefore an
assertion, on the part of the authoritative DNS server for the given
owner name, that there is some policy relationship between the owner
name and the target name. If a given target owner name lies in the same
policy realm as several other target names, an additional RR is
necessary for each such relationship, with one exception. It is not
uncommon for two
different names a name to have policy relationships among with all the
children beneath them. it. Using the SOPA RR, it is possible to specify
that the policy target is all the names beneath a given owner name,
by using a wildcard target.

4. Use Cases

In the most general sense, this memo presents a mechanism that can be
used either as a replacement of the public suffix list
<publicsuffix.org>, or else as a way to build and maintain such a
list. Performance characteristics may make the mechanism impractical
as a full replacement, in which case a list will likely need to be
built and maintained. In the latter case, this mechanism is still
preferable because it aligns the policy assertions with the operation
of the domains themselves, and allows maintenance to be distributed
in much the way the operation of the DNS is (instead of being
centralized).

It is worth noting that the mechanism outlined here could be used for
names that are not along the same branch of the DNS tree (i.e. it
could permit the statement that the policy authority of
some.example.com and some.other.example.net is the same). Such uses
are unlikely to work in practice and probably should not be used for
general purposes. Most deployed code implicitly uses ancestor-
descendent relations as part of understanding the policy, and such
code will undoubtedly ignore cross-tree dependencies. [[CREF3: This
relaxes a restriction that was in previous versions, which officially
specified the use only for ancestor-descendent uses. It seems better
to make that a deployment consideration so that the restriction could
be relaxed in some circumstances where it would be appropriate.
--ajs@anvilwalrusden.com]]

By and large, the mechanism is best suited to "orphan" types of
policy. Where inheritance types of policy can use this, it is mostly
by treating the mechanism as a generator for public suffix
boundaries.

4.1. Where SOPA Works Well

HTTP state management cookies The mechanism can be used to determine
the scope for data sharing of HTTP state management cookies
[RFC6265]. Using this mechanism, it is possible to determine
whether a service at one name may be permitted to set a cookie for
a service at a different name. (Other protocols use cookies, too,
and those approaches could benefit similarly.) Because handling
of state management cookies often happens during user interaction,
this use case probably requires a cached copy of the relevant
list. In that case, the mechanism can be used to maintain the
list.

User interface indicators User interfaces sometimes attempt to
indicate the "real" domain name in a given domain name. A common
use is to highlight the portion of the domain name believed to be
the "real" name -- usually the rightmost three or four labels in a
domain name string. This has similar performance needs as HTTP
state management cookies.

Setting the document.domain property The DOM same-origin policy
might be helped by being able to identify a common policy realm.
This case again has a need for speedy determination of the
appropriate policy and would benefit from a cached list. It is
likely that the SOPA record on its own is inadequate for this
case, but the combination of SOPA and SRV records might be
helpful.

SSL and TLS certificates Certificate authorities need to be able to
discover delegation-centric domains in order to avoid issuance of
certificates at or above those domains. More generally, a CA
needs to decide whether, given a request, it should sign a
particular domain. This can be especially tricky in the case of
wildcards.

HSTS and Public Key Pinning with includeSubDomains flag
set
Clients that are using HSTS and public key pinning using
includeSubDomains need to be able to determine whether a subdomain
is properly within the policy realm of the parent. An application
performing this operation must answer the question, "Should I
accept the rules for using X as valid for Y.X?" This use case
sounds like an inheritance type, but it is in fact an orphan type.

Linking domains together for reporting purposes It can
be useful when preparing reports to be able to count different
domains as "the same thing". This is an example where special use
of SOPA even across the DNS tree could be helpful.

4.2. Where SOPA Works Less Well

Email authentication mechanisms Mail authentication mechanisms such
as DMARC [RFC7489] need to be able to find policy documents for a
domain name given a subdomain. This use case is an inheritance
type. Because the point of mechanisms like DMARC is to prevent
abuse, it is not possible to rely on the candidate owner name to
report accurately its policy relationships. But some ancestor is
possibly willing to make assertions about the policy under which
that ancestor permits names in the name space. This sort of case
can only use SOPA indirectly, via a static list that is composed
over time by SOPA queries. Other mechanisms will likely better
satisfy this need.

5. The SOPA Resource Record

The SOPA resource record, type number [TBD1], contains two fields in
its RDATA:

Relation: A one-octet field used to indicate the relationship
between the owner name and the target.

Target: A field used to contain a fully-qualified domain name, relative to the
root, name
that is in some relationship with the owner name. This
field is a maximum of 255 octets long, to match the
possible length of a fully-qualified domain name.

1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Relation | /
+-+-+-+-+-+-+-+-+ /
/ Target /
/ /
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1

5.1. The Relation Field

The relation field is REQUIRED and contains an indicator of the
relationship between the owner name and the target name. This memo
specifies two possible values:

Table 1

Additional values may be defined in future, according to the rules
set out in Section 12.

5.2. The Target Field

The target field contains a (fully-qualified) fully-qualified domain name, and is
REQUIRED to be populated. The name MUST be a domain name according
to the rules in [RFC1034] and [RFC1035], except that the left-most any label of
the target MAY be the wildcard character ("*"). ("*"; further discussion of
wildcards is in Section 6.4). The target MUST be sent in
uncompressed form [RFC1035] [RFC1035], [RFC3597]. The target MUST NOT be an
alias [RFC2181], such as the owner name of a CNAME RR [RFC1034],
DNAME RR [RFC6672], or other similar such resource records. Note
that this is a fully-qualified domain name, so the trailing null
label is required. [[CREF4: This is a change from previous versions;
previously, the target was a root-relative domain name. So it's now
example.com. and used to be example.com (no trailing dot) when in
presentation format. The new form makes this a domain name, whereas
before it could really have been a text field. Not sure which is
better. --ajs@anvilwalrusden.com]]

The target name MUST SHOULD be either an ancestor, a descendent, or a
sibling of the owner name in the record. This requirement is
intended to limit the applicability of the SOPA RR to names in the
same DNS hierarchy, thereby avoiding possible negative side effects
of unbounded linkages across disparate DNS subtrees, including those
subtrees rooted close to, or immediately below, the DNS root. In
special uses, however, it may be desirable to link across the DNS
tree. General-purpose clients MAY ignore target names that are
neither an ancestor, nor a descendent, nor a sibling of the owner
name in the record (and abort processing) in order to avoid the
aforementioned negative side-effects.

Targets MAY contain any series of octets, in order to accommodate
labels other than LDH labels [RFC6365]. No processing of labels
prior to matching targets is to be expected, however, and therefore
internationalized domain name targets use whatever form they appear
in the DNS. In particular, IDNA labels [RFC5890], [RFC5891],
[RFC5892], [RFC5893], [RFC5894] SHOULD appear in A-label form. A
SOPA-using client that receives a target containing octets outside
LDH MUST NOT treat the affected labels as U-labels, because there is
no way to discover whether the affected label is encoded as UTF-8 or
something else.

6. Expressing Different Policies with the SOPA RRTYPE

A SOPA RR has one of three different functions. The first is to
claim that two domain names are not in the same policy realm
("exclusion"). The second is to claim that two domain names are in
the same policy realm ("inclusion"). In both of these cases, it is
possible to make the assertion over groups of DNS names.

The third function describes a portion of the tree that would be
covered by targets containing a wildcard, but where the policy is the
opposite of that expressed with the wildcard. This is expressed
simply by including the relevant specific exception. For example,
all the subdomains under example.com could be indicated in a target
"*.example.com". To express a different policy for
exception.example.com than for the rest of the names under
example.com requires two SOPA RRs, one with the target
"*.example.com" and he the other with the target
"exception.example.com". The most-specific match to a target always
wins.

Is is important to note that any given fully-qualified the default setting is "exclusion". A
domain name does not lie in any given other name's policy realm unless
there is an explicit statement by appropriate SOPA resource record(s)
to the contrary. If a candidate target name does not appear in the target
of any SOPA record for some owner name, then that candidate target
does not lie in the same policy realm as that owner name.

It is acceptable for there to be more than one SOPA resource record
per owner name in a response. Each domain name, RR in the RDATA of each returned SOPA record, RRset is
treated as a separate policy statement about the original QNAME (query name). queried
name (QNAME). Note, however, that the QNAME from
the query might not be the owner
name of the SOPA RR: if the original QNAME was is an alias, then the actual SOPA
owner name in the DNS database will be different. different than the QNAME. In
other words, even though a SOPA target name field is not allowed to be an
an alias, statements about an
alias when resolving the SOPA RR aliases are followed followed; and SOPA
records are accepted transitively from the alias canonical name back to the canonical name.
QNAME.

6.1. The Exclusion Relation

A SOPA record with a where the relation field with has value 1 0 states that the
owner name and the target name are not in the same policy realm.
While this would might seem not to be obviously useful useless (given that positive
declarations are required for two names to be in the same policy
realm), default of exclude), a SOPA
record with a relation field value of 1 0 can be useful in combination
with a long TTL field, in order to ensure long term caching of the
policy.

In addition, an important function of SOPA is to enable the explicit
assertion that no other name lies in the same policy realm as the
owner name (or, what is equivalent, that the owner name should be
treated as a public suffix). In order to achieve this, the operator
of the zone may use a wildcard target together with a relation field
value of 1. 0. See Section 6.4.

In addition, an exclusion relation more-specific target can be used to override a more
general inclusion relation target (i.e. with a wildcard in the target) at the same owner
name. For example,

example.tld 86400 IN SOPA 2 0 *.example.tld

www.example.tld

example.tld 86400 IN SOPA 1 example.tld www.example.tld

A SOPA-using client that receives a SOPA resouce resource record with a
relation value of 1 0 MUST treat the owner name and the target name as
lying in different policy realms.

6.2. The Inclusion Relation

A SOPA record with a relation field set to 2 1 is an indicator that the
target name lies in the same policy realm as the owner name. In
order to limit the scope of security implications, the target name
and the owner name MUST SHOULD stand in some ancestor-decendant ancestor-descendant or
sibling relationship to one another. A SOPA-using client that is not
prepared for inclusion relationships outside the same branch of the
DNS MAY ignore such relationships and treat them as though they did
not exist.

The left-most label of a target may be a wildcard record, in order to
indicate that all descendant or sibling names lie in the same policy
realm as the owner name. See Section 6.4.

A SOPA-using client that receives a SOPA resouce resource record where
relation is set to 2 1 SHOULD treat the owner name and the target name
as lying in the same policy realm. If a client does not, it is
likely to experience unexpected failures because the client's policy
expectations are not aligned with those of the service operator.

6.3. Interpreting DNS Responses

There are three possible responses to a query for the SOPA RRTYPE at
an owner name that are relevant to determining the policy realm. The
first is Name Error (RCODE=3, also known as NXDOMAIN). In this case,
the owner name itself does not exist, and no further processing is
needed.

The second is a No Data response [RFC2308] of any type. The No Data
response means that the owner name in the QNAME does not recognize
any other name as part of a common policy realm. That is, a No Data
response is to be interpreted as though there were a SOPA resource
record with relation value 1 0 and a wildcard target. The TTL on the
policy in this case is the negative TTL from the SOA record, in case
it is available.

The final is a response with one or more SOPA resource records in the
Answer section. Each SOPA resource record asserts a relationship
between the owner name and the target name, according to the
functions of the SOPA RRTYPE outlined above.

Any other response is no different from any other sort of response
from the DNS, and is not in itself meaningful for determining the
policy realm of a name (though it might be meaningful for finding the
SOPA record).

6.4. Wildcards in Targets

The special character "*" in the target field is used to match any
label, but not according to the wildcard label rules in section 4.3.3
of [RFC1034]. Note that, because of the way wildcards work in the
DNS, is it not possible to place a restriction to the left of a
wildcard; so, for instance, example.*.example.com example.*.example.com. does not work. In
a SOPA target, it is possible to place such a restriction. In such
use, a wildcard label matches exactly one label:
example.*.example.com. matches the target example.foo.example.com.
and example.bar.example.com., but not example.foo.bar.example.com.
To match the latter, it would be necessary also to include
example.*.*.example.com, which is also permitted in a target. This
use of the wildcard is consistent with the use in
<https://publicsuffix.org/list/>.

If a SOPA target's first label is a wildcard label, the wildcard then
matches any number of labels. Therefore, a target of *.example.com.
matches both onelabel.example.com. and two.labels.example.com.; the
second match would not be a match in the DNS. This use of the
wildcard label does not match the public suffix list, but is included
for brevity of RRsets for certain presumed-common cases. This rule
is subject to more-specific matching (as discussed in Section 6.1 and
Section 6.2). To simplify implementation, more-specific matches
cannot have internal wildcards as described above.

The effect reason for these differences in wildcard-character handling is
because of the purpose of the wildcard character. In DNS matching,
processing happens label by label proceeding down the tree, and the
goal is
maintained to find a match. But in this memo. the case of SOPA, the candidate
match is presumed available, because the application would not
perform a SOPA look up if there were not a different target domain at
hand. Therefore, strict conformance with the DNS semantics of the
wildcard is not necessary. It is useful to be able to express
potential matches as briefly as possible, to keep DNS response sizes
small.

Multiple leading wildcard labels (e.g. *.*.example.com.) is an error.
An authoritative name server SHOULD NOT serve a SOPA RR with
erroneous wildcards when it is possible to suppress them, and clients
receiving such a SOPA RR MUST discard the RR. If the discarded RR is
the last RR in the answer section of the response, then the response
is treated as a No Data response.

It is possible for the wildcard label to be the only label in the
target name. In this case, the target is "every name". This makes
it trivial for an owner name to assert that there are no other names
in its policy realm.

Because it would be absurd for there to be more than one SOPA RR with
the same wildcard target (including wildcard target) in a SOPA RRset, a server
encountering more than one such wildcard target SHOULD only serve the RR for
the exclusion relation, discarding others when possible. Discarding
other RRs in the RRset is not possible when serving a signed RRset.
A client receiving multiple wildcard targets in the RRset MUST use
only the RR with relation set to 1.

When 0.

As already noted, when a SOPA RR with a wildcard target appears in
the same RRset as a SOPA RR with a target that would be covered by
the wildcard, the specific (non-wildcard) RR expresses the policy for
that specific owner name/target pair. This way, exceptions to a
generic policy can be expressed.

6.5. TTLs and SOPA RRs

The TTL field in the DNS is used to indicate the period (in seconds)
during which an RRset may be cached after first encountering it (see
[RFC1034]). As is noted in Section 3, 4, however, SOPA RRs could be
used to build something like the public suffix list, and that list
would later be used by clients that might not themselves have access
to SOPA DNS RRsets. In order to support that use as reliably as
possible, a SOPA RR MAY continue to be used even after the TTL on the
RRset has passed, until the next time that a SOPA RRset from the DNS
for the owner name (or a No Data response) is available. It is
preferable to fetch the more-current data in the DNS, and therefore
if such DNS responses are available, a SOPA-aware client SHOULD use
them. Note that the extension of the TTL when DNS records are not
available does not extend to the use of the negative TTL field from
No Data responses.

7. What Can be Done With a SOPA RR

Use of a SOPA RR enables a site administrator to assert or deny
relationships between names. By the same token, it permits a a
consuming client to detect these assertions and denials.

The use of SOPA RRs could either replace the public suffix list or
(more
(often more likely due to some limitations -- see Section 9) simplify
and automate the management of the public suffix list. A client
could use the responses to SOPA queries to refine its determinations
about http cookie Domain attributes. In the absence of SOPA RRs at
both owner names, a client might treat a Domain attribute as though
it were omitted. More generally, SOPA RRs would permit additional
steps similar to steps 4 and 5 in [RFC6265].

SOPA RRs might be valuable for certificate authorities when issuing
certificates, because it would allow them to check whether two names
are related in the way the party requesting the certificate claims
they are.

7.1. Exclusion has Priority

In order to minimize the chance of policy associations where none
exist, this memo always assumes exclusion unless there is an explicit
policy for inclusion. Therefore, a client processing SOPA records
can stop as soon as it encounters an exclusion record: if a parent
record excludes a child record, it makes no difference whether the
child includes the parent in the policy realm, and conversely. By
the same token, an inclusion SOPA record that specifies a target,
where the target does not publish a corresponding inclusion SOPA
record, is not effective.

8. An Example Case

For the purposes of discussion, it will be useful to imagine a
portion of the DNS, using the domain example.tld. A diagram of the
tree of this portion is in Figure 2. In the example, the domain
example.tld includes several other names: www.example.tld,
account.example.tld, cust1.example.tld, cust2.example.tld,
test.example.tld, cust1.test.example.tld, and cust2.test.example.tld.

tld
|
|
------example -----
/ / | \ \
/ / | \ \
/ www account \ cust2
test \
/ \ cust1
cust1 cust2

Figure 2

In the example, the domain tld delegates the domain example.tld.
There are other possible cut points in the example, and depending on
whether the cuts exist there may be implications for the use of the
examples. See Section 8.1, below.

The (admittedly artificial) example permits us to distinguish a
number of different roles. To begin with, there are three parties
involved in the operation of services:

o OperatorV, the operator of example.tld;

o Operator1, the operator of cust1.example.tld;

o Operator2, the operator of cust2.example.tld.

Since there are three parties, there are likely three administrative
boundaries as well; but the example contains some others. For
instance, the names www.example.tld and example.tld are in this case
in the same policy realm. By way of contrast, account.example.tld
might be treated as completely separate, because OperatorV might wish
to ensure that the accounts system is never permitted to share
anything with any other name. By the same token, the names
underneath test.example.tld are actually the test-instance sites for
customers. So cust1.test.example.tld might be in the same policy
realm as cust1.example.tld, but test.example.tld is certainly not in
the same administrative realm as www.example.tld.

Finally, supposing that Operator1 and Operator2 merge their
operations, it seems that it would be useful for cust1.example.tld
and cust2.example.tld to lie in the same policy realm, without
including everything else in example.tld.

8.1. Examples of Using the SOPA Record for Determining Boundaries

This section provides some examples of different configurations of
the example tree in Section 8, above. The examples are not
exhaustive, but may provide an indication of what might be done with
the mechanism.

8.1.1. Declaring a Public Suffix

Perhaps the most important function of the SOPA RR is to identify
public suffixes. In this example, the operator of TLD publishes a
single SOPA record:

tld. 86400 IN SOPA 1 * 0 *.

8.1.2. One Delegation, Eight Administrative Realms, Wildcard Exclusions

In this scenario, the example portion of the domain name space
contains all and only the following SOPA records:

example.tld. 86400 IN SOPA 2 www.example.tld 1 www.example.tld.

www.example.tld. 86400 IN SOPA 2 example.tld 1 example.tld.

Tld is the top-level domain, and has delegated example.tld. The
operator of example.tld makes no delegations. There are four
operators involved: the operator of tld; OperatorV; Operator1, the
operator of the services at cust1.example.tld and
cust1.test.example.tld; and Operator2, the operator of the services
at cust2.example.tld and cust2.test.example.tld.

In this arrangement, example.tld and www.example.tld positively claim
to be within the same policy realm. Every other name stands alone.
A query for an SOPA record at any of those other names will result in
a No Data response, which means that none of them include any other
name in the same policy realm. As a result, there are eight separate
policy realms in this case: tld, {example.tld and www.example.tld},
test.example.tld, cust1.test.example.tld, cust2.test.example.tld,
account.example.tld, cust1.example.tld, and cust2.example.tld.

8.1.3. One Delegation, Eight Administrative Realms, Exclusion Wildcards

This example mostly works the same way as the one in
Section Section 8.1.2, but there is a slight difference. In this
case, in addition to the records listed in Section 8.1.2, both tld
and test.example.tld publish exclusion of all names in their SOPA
records:

tld. 86400 IN SOPA 1 * 0 *.

test.example.tld. 86400 IN SOPA 1 * 0 *.

The practical effect of this is largely the same as the previous
example, except that these expressions of policy last (at least)
86,400 seconds instead of the length of time on the negative TTL in
the relevant SOA for the zone. Many zones have short negative TTLs
because of expectations that newly-added records will show up
quickly. This mechanism permits such names to express their
administrative isolation for predictable minimum periods of time.
Moreover, In
addition, because clients are permitted to retain these records
during periods when DNS service is not available, a client could go
offline for several weeks, and return to service with the presumption
that test.example.tld is still not in any policy realm with any other
name.

9. Limitations of the approach and other considerations

There are four significant problems with this proposal, all of which
are related to using DNS to deliver the data.

The first is that new DNS RRTYPEs are difficult to deploy. While
adding a new RRTYPE is straightforward, many provisioning systems do
not have the necessary support and some firewalls and other edge
systems continue to filter RRTYPEs they do not know. This is yet
another reason why this mechanism is likely to be initially more
useful for constructing and maintaining the public suffix list than
for real-time queries.

The second is that it is difficult for an application to obtain data
from the DNS. The TTL on an RRset, in particular, is usually not
available to an application, even if the application uses the
facilities of the operating system to deliver other parts of an
unknown RRTYPE.

The third, which is mostly a consequence of the above two, is that
there is a significant barrier to adoption: until browsers have
mostly all implemented this, operations need to proceed as though
nobody has. But browsers will need to support two mechanisms for
some period of time if they are to implement this mechanism at all,
and they are unlikely to want to do that. This may mean that there
is no reason to implement, which also means no reason to deploy.
This is made worse because, to be safe, the mechanism really needs
DNSSEC, and performing DNSSEC validation at end points is still an
unusual thing to do. This limitation may not be as severe for use-
cases that are directed higher in the network (such as using this
mechanism as an automatic feed to keep the public suffix list
updated, or for the use of CAs when issuing certificates). This
limitation could be reduced by using SOPA records to maintain
something like the current public suffix list in an automatic
fashion.

Fourth, in many environments the system hosting the application has
only proxied access to the Internet, and cannot query the DNS
directly. It is not clear how such clients could ever possibly
retrieve the SOPA record for a name.

9.1. Handling truncation

It is possible to put enough SOPA records into a zone such that the
resulting response will exceed DNS or UDP protocol limits. In such
cases, a UDP DNS response will arrive with the TC (truncation) bit
set. A SOPA response with the TC bit must be queried again in order
to retrieve a complete response, generally using TCP. This increases
the cost of the query, increases the time to being able to use the
answer, and may not work at all in networks where administrators
mistakenly block port 53 using TCP.

10. Security Considerations

This mechanism enables publication of assertions about administrative
relationships of different DNS-named systems on the Internet. If
such assertions are accepted without checking that both sides agree
to the assertion, it would be possible for one site to become an
illegitimate source for data to be consumed in some other site. In
general, assertions about another name should never be accepted
without querying the other name for agreement.

Undertaking any of the inferences suggested in this draft without the
use of the DNS Security Extensions exposes the user to the
possibility of forged DNS responses.

11. Internationalization Considerations

There is some discussion of how to treat targets that appear to have
internationalized data in Section 5.2. Otherwise, this memo raises
no internationalization considerations.

12. IANA Considerations

IANA will be requested to register the SOPA RRTYPE if this proceeds.

12.

IANA will be requested to create a SOPA relation registry if this
proceeds. The initial values are to be found in the table in
Section 5.1. Registration rules should require a high bar, because
it's a one-octet field. Maybe RFC required?

13. Acknowledgements

The authors thank Adam Barth, Dave Crocker, Brian Dickson, Phillip
Hallam-Baker, John Klensin, Murray Kucherawy, John Levine, Gervase
Markham, Patrick McManus, Henrik Nordstrom, Yngve N. Pettersen, Eric
Rescorla, Thomas Roessler, Peter Saint-Andre, and Maciej Stachowiak
for helpful comments.

13. Informative

14. References

[I-D.kucherawy-dmarc-base]
Kucherawy, M., "Domain-based Message Authentication,
Reporting and Conformance (DMARC)", draft-kucherawy-dmarc-
base-00 (work

14.1. Normative References

[RFC2119] Bradner, S., "Key words for use in progress), RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 2013.

[I-D.pettersen-subtld-structure]
Pettersen, Y., "The Public Suffix Structure file format 1997,
<http://www.rfc-editor.org/info/rfc2119>.

14.2. Informative References

[I-D.sullivan-dbound-problem-statement]
Sullivan, A., Hodges, J., and its use for Cookie domain validation", J. Levine, "DBOUND: DNS
Administrative Boundaries Problem Statement", draft-
pettersen-subtld-structure-09
sullivan-dbound-problem-statement-01 (work in progress), March
2012.
July 2015.

[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987. 1987,
<http://www.rfc-editor.org/info/rfc1034>.

[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. 1987, <http://www.rfc-editor.org/info/rfc1035>.

[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997. 1997,
<http://www.rfc-editor.org/info/rfc2181>.

[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998. 1998,
<http://www.rfc-editor.org/info/rfc2308>.

[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
DOI 10.17487/RFC2782, February 2000. 2000,
<http://www.rfc-editor.org/info/rfc2782>.

[RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record
(RR) Types", RFC 3597, DOI 10.17487/RFC3597, September 2003.
2003, <http://www.rfc-editor.org/info/rfc3597>.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005. 2005,
<http://www.rfc-editor.org/info/rfc3986>.

[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. 2005,
<http://www.rfc-editor.org/info/rfc4033>.

[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005. 2005,
<http://www.rfc-editor.org/info/rfc4034>.

[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005. 2005,
<http://www.rfc-editor.org/info/rfc4035>.

[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35, RFC 4395,
DOI 10.17487/RFC4395, February 2006. 2006,
<http://www.rfc-editor.org/info/rfc4395>.

[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008.

[RFC6125] Saint-Andre, P. and J. Hodges, "Representation 2008,
<http://www.rfc-editor.org/info/rfc5155>.

[RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates Document Framework",
RFC 5890, DOI 10.17487/RFC5890, August 2010,
<http://www.rfc-editor.org/info/rfc5890>.

[RFC5891] Klensin, J., "Internationalized Domain Names in the Context of Transport Layer
Security (TLS)",
Applications (IDNA): Protocol", RFC 6125, March 2011. 5891,
DOI 10.17487/RFC5891, August 2010,
<http://www.rfc-editor.org/info/rfc5891>.

[RFC5892] Faltstrom, P., Ed., "The Unicode Code Points and
Internationalized Domain Names for Applications (IDNA)",
RFC 5892, DOI 10.17487/RFC5892, August 2010,
<http://www.rfc-editor.org/info/rfc5892>.

[RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts
for Internationalized Domain Names for Applications
(IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010,
<http://www.rfc-editor.org/info/rfc5893>.

[RFC5894] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Background, Explanation, and
Rationale", RFC 5894, DOI 10.17487/RFC5894, August 2010,
<http://www.rfc-editor.org/info/rfc5894>.

[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011. 2011,
<http://www.rfc-editor.org/info/rfc6265>.

[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, DOI 10.17487/RFC6335, August 2011. 2011,
<http://www.rfc-editor.org/info/rfc6335>.

[RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
Internationalization in the IETF", BCP 166, RFC 6365,
DOI 10.17487/RFC6365, September 2011,
<http://www.rfc-editor.org/info/rfc6365>.

[RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the
DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012.

[publicsuffix.org]
Mozilla Foundation, "Public Suffix List", also known as:
Effective TLD (eTLD) List, . 2012,
<http://www.rfc-editor.org/info/rfc6672>.

[RFC7489] Kucherawy, M., Ed. and E. Zwicky, Ed., "Domain-based
Message Authentication, Reporting, and Conformance
(DMARC)", RFC 7489, DOI 10.17487/RFC7489, March 2015,
<http://www.rfc-editor.org/info/rfc7489>.

[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", RFC 7719, DOI 10.17487/RFC7719, December
2015, <http://www.rfc-editor.org/info/rfc7719>.

Appendix A. Discussion Venue

This Internet-Draft is discussed on in the applications area dbound working
group mailing list: apps-discuss@ietf.org. group:
dbound@ietf.org.

Appendix B. Change History

00 to 01:

* Changed the mnemonic from BOUND to AREALM

* Added ports and scheme to the RRTYPE

* Added some motivating text and suggestions about what can be
done with the new RRTYPE

* Removed use of "origin" term, because it was confusing. The
document filename preserves "origin" in the name in order that
the tracker doesn't lose the change history, but that's just a
vestige.

* Removed references to cross-document information sharing and
ECMAScript. I don't understand the issues there, but Maciej
Stachowiak convinced me that they're different enough that this
mechanism probably won't work.

* Attempted to respond to all comments received. Thanks to the
commenters; omissions and errors are mine.

01 to 02:

* Changed mnemonic again, from AREALM to SOPA. This in response
to observation by John Klensin that anything using
"administrative" risks confusion with the standard
administrative boundary language of zone cuts.

* Add discussion of two strategies: name-only or scheme-and-port.

* Increase prominence of utility to CAs. This use emerged in
last IETF meeting.

02 to 03:

* Removed discussion of scheme-and-port, which was confusing.

* Add inclusion/exclusion/exception approach in response to
comment by Phill H-B.

* Change mechanism for indicating "no others" to a wildcard
mechanism.

* Added better discussion of use cases

03 to 00:

* Renamed file to get rid of "origin", which caused confusion.

* Added Jeff as co-author

* Remove exception relation; instead, more than one RR is
allowed.

* Added discussion of SRV records

00 to 01:

* Failed to include change control entry

* Modest rearrangement of text, little improvement

01 to 02:

* Significant rearrangement of sections

* Large removal of text (moved to problem statement document)

* Considerably more detail in specification, including more
rigorous description of RRTYPE

* Altered handling of wildcard targets

* Attempt to improve overview to make it plainer what the system
does

* Clarify what use cases really work
* Reversion to permit cross-tree use, with deployment warnings
that it won't be useful

Authors' Addresses

Andrew Sullivan
Dyn, Inc.
150 Dow St
Manchester, NH 03101
U.S.A.

Email: asullivan@dyn.com

Jeff Hodges
PayPal
2211 North First Street
San Jose, California 95131
US

Email: Jeff.Hodges@PayPal.com