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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 RFC 4592

DNSEXT Working Group                                            E. Lewis
INTERNET DRAFT                                                   NeuStar
Expiration Date: November 11, 2005                           May 11 2005

                           The Role of Wildcards
                         in the Domain Name System
                   draft-ietf-dnsext-wcard-clarify-06.txt

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This is an update to the wildcard definition of RFC 1034.  The
   interaction with wildcards and CNAME is changed, an error
   condition removed, and the words defining some concepts central to
   wildcards are changed.  The overall goal is not to change wildcards,
   but to refine the definition of RFC 1034.

1 Introduction

   In RFC 1034 [RFC1034], sections 4.3.2 and 4.3.3 describe the synthesis
   of answers from special resource records called wildcards.  The
   definition in RFC 1034 is incomplete and has proven to be confusing.
   This document describes the wildcard synthesis by adding to the
   discussion and making limited modifications.  Modifications are made
   to close inconsistencies that have led to interoperability issues.
   This description does not expand the service intended by the original
   definition.

   Staying within the spirit and style of the original documents, this
   document avoids specifying rules for DNS implementations regarding
   wildcards.  The intention is to only describe what is needed for
   interoperability, not restrict implementation choices.  In addition,
   consideration has been given to minimize any backwards compatibility
   with implementations that have complied with RFC 1034's definition.

   This document is focused on the concept of wildcards as defined in RFC
   1034.  Nothing is implied regarding alternative approaches, nor are
   alternatives discussed.

1.1 Motivation

   Many DNS implementations have diverged with respect to wildcards in
   different ways from the original definition, or at from least what
   had been intended.  Although there is clearly a need to clarify the
   original documents in light of this alone, the impetus for this
   document lay in the engineering of the DNS security extensions
   [RFC4033].  With an unclear definition of wildcards the design of
   authenticated denial became entangled.

   This document is intended to limit changes,  only those based on
   implementation experience, and to remain as close to the original
   document as possible.  To reinforce this, relevant sections of RFC
   1034 are repeated verbatim to help compare the old and new text.

1.2 The Original Definition

   The context of the wildcard concept involves the algorithm by which
   a name server prepares a response (in RFC 1034's section 4.3.2) and
   the way in which a resource record (set) is identified as being a
   source of synthetic data (section 4.3.3).

   The beginning of the discussion ought to start with the definition
   of the term "wildcard" as it appears in RFC 1034, section 4.3.3.

# In the previous algorithm, special treatment was given to RRs with
# owner names starting with the label "*".  Such RRs are called
# wildcards. Wildcard RRs can be thought of as instructions for
# synthesizing RRs.  When the appropriate conditions are met, the name
# server creates RRs with an owner name equal to the query name and
# contents taken from the wildcard RRs.

   This passage appears after the algorithm in which the term wildcard
   is first used.   In this definition, wildcard refers to resource
   records.  In other usage, wildcard has referred to domain names, and
   it has been used to describe the operational practice of relying on
   wildcards to generate answers.  It is clear from this that there is
   a need to define clear and unambiguous terminology in the process of
   discussing wildcards.

   The mention of the use of wildcards in the preparation of a response
   is contained in step 3c of RFC 1034's section 4.3.2 entitled
   "Algorithm." Note that "wildcard" does not appear in the algorithm,
   instead references are made to the "*" label.  The portion of the
   algorithm relating to wildcards is deconstructed in detail in
   section 3 of this document, this is the beginning of the passage.

#        c. If at some label, a match is impossible (i.e., the
#           corresponding label does not exist), look to see if [...]
#           the "*" label exists.

   The scope of this document is the RFC 1034 definition of wildcards and
   the implications of updates to those documents, such as DNSSEC.
   Alternate schemes for synthesizing answers are not considered.
   (Note that there is no reference listed.  No document is known to
   describe any alternate schemes, although there has been some
   mention of them in mailing lists.)

1.3 This Document

   This document accomplishes these three items.
   o Defines new terms
   o Makes minor changes to avoid conflicting concepts
   o Describes the actions of certain resource records as wildcards

1.3.1 New Terms

   To help in discussing what resource records are wildcards, two terms
   will be defined - "asterisk label" and "wild card domain name".  These
   are defined in section 2.1.1.

   To assist in clarifying the role of wildcards in the name server
   algorithm in RFC 1034, 4.3.2, "source of synthesis" and "closest
   encloser" are defined.  These definitions are in section 3.3.2.
   "Label match" is defined in section 3.2.

   The introduction of new terms ought not have an impact on any existing
   implementations.  The new terms are used only to make discussions of
   wildcards clearer.

1.3.2 Changed Text

   The definition of "existence" is changed, superficially.  This
   change will not be apparent to implementations; it is needed to
   make descriptions more precise.  The change appears in section 2.2.3.

   RFC 1034, section 4.3.3., seems to prohibit having two asterisk
   labels in a wildcard owner name.  With this document the restriction
   is removed entirely.  This change and its implications are in
   section 2.1.3.

   The actions when a source of synthesis owns a CNAME RR are changed to
   mirror the actions if an exact match name owns a CNAME RR.  This
   is an addition to the words in RFC 1034, section 4.3.2, step 3,
   part c.  The discussion of this is in section 3.3.3.

   Only the latter change represents an impact to implementations.  The
   definition of existence is not a protocol impact.  The change to the
   restriction on names is unlikely to have an impact, as there was no
   discussion of how to enforce the restriction.

1.3.3 Considerations with Special Types

   This document describes semantics of wildcard CNAME RRSets [RFC2181],
   wildcard NS RRSets, wildcard SOA RRSets, wildcard DNAME RRSets
   [RFC2672], wildcard DS RRSets [RFC TBD], and empty non-terminal
   wildcards.  Understanding these types in the context of wildcards
   has been clouded because these types incur special processing if they
   are the result of an exact match.  This discussion is in section 4.

   These discussions do not have an implementation impact, they cover
   existing knowledge of the types, but to a greater level of detail.

1.4 Standards Terminology

   This document does not use terms as defined in "Key words for use in
   RFCs to Indicate Requirement Levels." [RFC2119]

   Quotations of RFC 1034 are denoted by a '#' in the leftmost column.

2 Wildcard Syntax

   The syntax of a wildcard is the same as any other DNS resource record,
   across all classes and types.  The only significant feature is the
   owner name.

   Because wildcards are encoded as resource records with special names,
   they are included in zone transfers and incremental zone transfers.
   [RFC1995].  This feature has been underappreciated until discussions
   on alternative approaches to wildcards appeared on mailing lists.

2.1 Identifying a Wildcard

   To provide a more accurate description of "wildcards", the definition
   has to start with a discussion of the domain names that appear as
   owners.  Two new terms are needed, "Asterisk Label" and "Wild Card
   Domain Name."

2.1.1 Wild Card Domain Name and Asterisk Label

   A "wild card domain name" is defined by having its initial
   (i.e., left-most or least significant) label be, in binary format:

        0000 0001 0010 1010 (binary) = 0x01 0x2a (hexadecimal)

   The first octet is the normal label type and length for a 1 octet
   long label, the second octet is the ASCII representation [RFC20] for
   the '*' character.

   A descriptive name of a label equaling that value is an "asterisk
   label."

   RFC 1034's definition of wildcard would be "a resource record owned
   by a wild card domain name."

2.1.2 Asterisks and Other Characters

   No label values other than that in section 2.1.1 are asterisk labels,
   hence names beginning with other labels are never wild card domain
   names.  Labels such as 'the*' and '**' are not asterisk labels,
   they do not start wild card domain names.

2.1.3 Non-terminal Wild Card Domain Names

   In section 4.3.3, the following is stated:

#   ..........................  The owner name of the wildcard RRs is of
#   the form "*.<anydomain>", where <anydomain> is any domain name.
#   <anydomain> should not contain other * labels......................

   This restriction is lifted because the original documentation of it
   is incomplete and the restriction does not serve any purpose given
   years of operational experience.

   Indirectly, the above passage raises questions about wild card domain
   names having subdomains and possibly being an empty non-terminal.  By
   thinking of domain names such as "*.example.*.example." and
   "*.*.example." and focusing on the right-most asterisk label in each,
   the issues become apparent.

   Although those example names have been restricted per RFC 1034, a name
   such as "example.*.example." illustrates the same problems.  The
   sticky issue of subdomains and empty non-terminals is not removed by
   the restriction.  With that conclusion, the restriction appears to
   be meaningless, worse yet, it implies that an implementation would
   have to perform checks that do little more than waste CPU cycles.

   A wild card domain name can have subdomains.  There is no need to
   inspect the subdomains to see if there is another asterisk label in
   any subdomain.

   A wild card domain name can be an empty non-terminal.  (See the
   upcoming sections on empty non-terminals.)  In this case, any
   lookup encountering it will terminate as would any empty
   non-terminal match.

2.2 Existence Rules

   The notion that a domain name 'exists' is mentioned in the definition
   of wildcards.  In section 4.3.3 of RFC 1034:

# Wildcard RRs do not apply:
#
...
#   - When the query name or a name between the wildcard domain and
#     the query name is know[n] to exist.  For example, if a wildcard

   RFC 1034 also refers to non-existence in the process of generating
   a response that results in a return code of "name error."  NXDOMAIN
   is introduced in RFC 2308, section 2.1 says "In this case the domain
   ... does not exist." The overloading of the term "existence" is
   confusing.

   For the purposes of this document, a domain name is said to exist if
   it plays a role in the execution of the algorithms in RFC 1034.  This
   document avoids discussion determining when an authoritative name
   error has occurred.

2.2.1 An Example

   To illustrate what is meant by existence consider this complete zone:

       $ORIGIN example.
       example.                  3600 IN  SOA   <SOA RDATA>
       example.                  3600     NS    ns.example.com.
       example.                  3600     NS    ns.example.net.
       *.example.                3600     TXT   "this is a wild card"
       *.example.                3600     MX    10 host1.example.
       sub.*.example.            3600     TXT   "this is not a wild card"
       host1.example.            3600     A     192.0.4.1
       _ssh._tcp.host1.example.  3600     SRV  <SRV RDATA>
       _ssh._tcp.host2.example.  3600     SRV  <SRV RDATA>
       subdel.example.           3600     NS   ns.example.com.
       subdel.example.           3600     NS   ns.example.net.

   A look at the domain names in a tree structure is helpful:

                                 |
                 -------------example------------
                /           /         \          \
               /           /           \          \
              /           /             \          \
             *          host1          host2      subdel
             |            |             |
             |            |             |
            sub         _tcp          _tcp
                          |             |
                          |             |
                        _ssh          _ssh

   The following queries would be synthesized from one of the wildcards:

        QNAME=host3.example. QTYPE=MX, QCLASS=IN
             the answer will be a "host3.example. IN MX ..."

        QNAME=host3.example. QTYPE=A, QCLASS=IN
             the answer will reflect "no error, but no data"
             because there is no A RR set at '*.example.'

        QNAME=foo.bar.example. QTYPE=TXT, QCLASS=IN
             the answer will be "foo.bar.example. IN TXT ..."
             because bar.example. does not exist, but the wildcard does.

   The following queries would not be synthesized from any of the
   wildcards:

        QNAME=host1.example., QTYPE=MX, QCLASS=IN
             because host1.example. exists

        QNAME=ghost.*.example., QTYPE=MX, QCLASS=IN
             because *.example. exists

        QNAME=sub.*.example., QTYPE=MX, QCLASS=IN
             because sub.*.example. exists

        QNAME=_telnet._tcp.host1.example., QTYPE=SRV, QCLASS=IN
             because _tcp.host1.example. exists (without data)

        QNAME=host.subdel.example., QTYPE=A, QCLASS=IN
             because subdel.example. exists (and is a zone cut)

2.2.2 Empty Non-terminals

   Empty non-terminals [RFC2136, Section 7.16] are domain names that own
   no resource records but have subdomains that do.  In section 2.2.1,
   "_tcp.host1.example." is an example of a empty non-terminal name.
   Empty non-terminals are introduced by this text in section 3.1 of RFC
   1034:

# The domain name space is a tree structure.  Each node and leaf on the
# tree corresponds to a resource set (which may be empty).  The domain
# system makes no distinctions between the uses of the interior nodes
# and leaves, and this memo uses the term "node" to refer to both.

   The parenthesized "which may be empty" specifies that empty non-
   terminals are explicitly recognized, and that empty non-terminals
   "exist."

   Pedantically reading the above paragraph can lead to an
   interpretation that all possible domains exist - up to the suggested
   limit of 255 octets for a domain name [RFC1035].  For example,
   www.example. may have an A RR, and as far as is practically
   concerned, is a leaf of the domain tree.  But the definition can be
   taken to mean that sub.www.example. also exists, albeit with no data.
   By extension, all possible domains exist, from the root on down.  As
   RFC 1034 also defines "an authoritative name error indicating that
   the name does not exist" in section 4.3.1, this is not the intent of
   the original document.

2.2.3 Yet Another Definition of Existence

   RFC1034's wording is fixed by the following paragraph:

   The domain name space is a tree structure.  Nodes in the tree either
   own at least one RRSet and/or have descendants that collectively own
   at least on RRSet.  A node may have no RRSets if it has descendents
   that do, this node is a empty non-terminal.  A node may have its own
   RRSets and have descendants with RRSets too.

   A node with no descendants is a leaf node.  Empty leaf nodes do not
   exist.

   Note that at a zone boundary, the domain name owns data, including
   the NS RR set.  At the delegating server, the NS RR set is not
   authoritative, but that is of no consequence here.  The domain name
   owns data, therefore, it exists.

2.3 When does a Wild Card Domain Name is not Special

   When a wild card domain name appears in a message's query section,
   no special processing occurs.  An asterisk label in a query name
   only (label) matches an asterisk label in the existing zone tree
   when the 4.3.2 algorithm is being followed.

   When a wild card domain name appears in the resource data of a
   record, no special processing occurs.  An asterisk label in that
   context literally means just an asterisk.

3. Impact of a Wild Card Domain Name On a Response

   The description of how wildcards impact response generation is in
   RFC 1034, section 4.3.2.  That passage contains the algorithm
   followed by a server in constructing a response.  Within that
   algorithm, step 3, part 'c' defines the behavior of the wild card.

   The algorithm in RFC 1034, section 4.3.2. is not intended to be pseudo
   code, i.e., its steps are not intended to be followed in strict
   order.  The "algorithm" is a suggestion.  As such, in step 3, parts
   a, b, and c, do not have to be implemented in that order.

3.1 Step 2

   Step 2 of the RFC 1034's section 4.3.2 reads:

#   2. Search the available zones for the zone which is the nearest
#      ancestor to QNAME.  If such a zone is found, go to step 3,
#      otherwise step 4.

   In this step, the most appropriate zone for the response is chosen.
   The significance of this step is that it means all of step 3 is being
   performed within one zone.  This has significance when considering
   whether or not an SOA RR can be ever be used for synthesis.

3.2 Step 3

   Step 3 is dominated by three parts, labelled 'a', 'b', and 'c'.  But
   the beginning of the step is important and needs explanation.

#   3. Start matching down, label by label, in the zone.  The
#      matching process can terminate several ways:

   The word 'matching' refers to label matching.  The concept
   is based in the view of the zone as the tree of existing names.  The
   query name is considered to be an ordered sequence of labels - as
   if the name were a path from the root to the owner of the desired
   data.  (Which it is - 3rd paragraph of RFC 1034, section 3.1.)

   The process of label matching a query name ends in exactly one of
   three choices, the parts 'a', 'b', and 'c'.  Either the name is
   found, the name is below a cut point, or the name is not found.

   Once one of the parts is chosen, the other parts are not considered.
   (E.g., do not execute part 'c' and then change the execution path to
   finish in part 'b'.)  The process of label matching is also done
   independent of the query type (QTYPE).

   Parts 'a' and 'b' are not an issue for this clarification as they
   do not relate to record synthesis.  Part 'a' is an exact match that
   results in an answer, part 'b' is a referral.  It is possible, from
   the description given, that a query might fit into both part a and
   part b, this is not within the scope of this document.

3.3 Part 'c'

   The context of part 'c' is that the process of label matching the
   labels of the query name has resulted in a situation in which there
   is no corresponding label in the tree.  It is as if the lookup has
   "fallen off the tree."

#         c. If at some label, a match is impossible (i.e., the
#            corresponding label does not exist), look to see if [...]
#            the "*" label exists.

   To help describe the process of looking 'to see if [...] the "*"
   label exists' a term has been coined to describe the last domain
   (node) matched.  The term is "closest encloser."

3.3.1 Closest Encloser and the Source of Synthesis

   The closest encloser is the node in the zone's tree of existing
   domain names that has the most labels matching the query name
   (consecutively, counting from the root label downward). Each match
   is a "label match" and the order of the labels is the same.

   The closest encloser is, by definition, an existing name in the zone.
   The closest encloser might be an empty non-terminal or even be a wild
   card domain name itself.  In no circumstances is the closest encloser
   to be used to synthesize records for the current query.

   The source of synthesis is defined in the context of a query process
   as that wild card domain name immediately descending from the
   closest encloser, provided that this wild card domain name exists.
   "Immediately descending" means that the source of synthesis has a name
   of the form <asterisk label>.<closest encloser>.  A source of
   synthesis does not guarantee having a RRSet to use for synthesis.
   The source of synthesis could be an empty non-terminal.

   If the source of synthesis does not exist (not on the domain tree),
   there will be no wildcard synthesis.  There is no search for an
   alternate.

   The important concept is that for any given lookup process, there
   is at most one place at which wildcard synthetic records can be
   obtained.  If the source of synthesis does not exist, the lookup
   terminates, the lookup does not look for other wildcard records.

3.3.2 Closest Encloser and Source of Synthesis Examples

   To illustrate, using the example zone in section 2.2.1 of this
   document, the following chart shows QNAMEs and the closest enclosers.

   QNAME                        Closest Encloser     Source of Synthesis
   host3.example.               example.             *.example.
   _telnet._tcp.host1.example.  _tcp.host1.example.  no source
   _telnet._tcp.host2.example.  host2.example.       no source
   _telnet._tcp.host3.example.  example.             *.example.
   _chat._udp.host3.example.    example.             *.example.
   foobar.*.example.            *.example.           no source

3.3.3 Type Matching

    RFC 1034 concludes part 'c' with this:

#            If the "*" label does not exist, check whether the name
#            we are looking for is the original QNAME in the query
#            or a name we have followed due to a CNAME.  If the name
#            is original, set an authoritative name error in the
#            response and exit.  Otherwise just exit.
#
#            If the "*" label does exist, match RRs at that node
#            against QTYPE.  If any match, copy them into the answer
#            section, but set the owner of the RR to be QNAME, and
#            not the node with the "*" label.  Go to step 6.

   The final paragraph covers the role of the QTYPE in the lookup
   process.

   Based on implementation feedback and similarities between step 'a' and
   step 'c' a change to this passage has been made.

   The change is to add the following text to step 'c':

            If the data at the source of synthesis is a CNAME, and
            QTYPE doesn't match CNAME, copy the CNAME RR into the
            answer section of the response changing the owner name
            to the QNAME, change QNAME to the canonical name in the
            CNAME RR, and go back to step 1.

   This is essentially the same text in step a covering the processing of
   CNAME RRSets.

4. Considerations with Special Types

   Sections 2 and 3 of this document discuss wildcard synthesis with
   respect to names in the domain tree and ignore the impact of types.
   In this section, the implication of wildcards of specific types are
   discussed.  The types covered are those that have proven to be the
   most difficult to understand.  The types are SOA, NS, CNAME, DNAME,
   SRV, DS, NSEC, RRSIG and "none," i.e., empty non-terminal wild card
   domain names.

4.1 SOA RRSet at a Wild Card Domain Name

   A wild card domain name owning an SOA RRSet means that the domain
   is at the root of the zone (apex).  The domain can not be a source of
   synthesis because that is, by definition, a descendent node (of
   the closest encloser) and a zone apex is at the top of the zone.

   Although a wild card domain name owning an SOA RRSet can never be a
   source of synthesis, there is no reason to forbid the ownership of
   an SOA RRSet.

   E.g., given this zone:
          $ORIGIN *.example.
          @                 3600 IN  SOA   <SOA RDATA>
                            3600     NS    ns1.example.com.
                            3600     NS    ns1.example.net.
          www               3600     TXT   "the www txt record"

   A query for www.*.example.'s TXT record would still find the "the www
   txt record" answer.  The reason is that the asterisk label only
   becomes significant when RFC 1034's 4.3.2, step 3 part 'c' in in
   effect.

   Of course, there would need to be a delegation in the parent zone,
   "example." for this to work too.  This is covered in the next section.

4.2 NS RRSet at a Wild Card Domain Name

   With the definition of DNSSEC [RFC4033, RFC4034, RFC4035] now in
   place, the semantics of a wild card domain name owning an NS RR has
   come to be poorly defined.  The dilemma relates to a conflict
   between the rules for synthesis in part 'c' and the fact that the
   resulting synthesis generates a record for which the zone is not
   authoritative.  In a DNSSEC signed zone, the mechanics of signature
   management (generation and inclusion in a message) become unclear.

   After some lengthy discussions, there has been no clear "best answer"
   on how to document the semantics of such a situation.  Barring such
   records from the DNS would require definition of rules for that, as
   well as introducing a restriction on records that were once legal.
   Allowing such records and amending the process of signature
   management would entail complicating the DNSSEC definition.

   Combining these observations with thought that a wild card domain name
   owning an NS record is an operationally uninteresting scenario, i.e.,
   it won't happen in the normal course of events, accomodating this
   situation in the specification would also be categorized as
   "needless complication." Further, expending more effort on this
   topic has proven to be an exercise in diminishing returns.

   In summary, there is no definition given for wild card domain names
   owning an NS RRSet.  The semantics are left undefined until there
   is a clear need to have a set defined, and until there is a clear
   direction to proceed.  Operationally, inclusion of wild card NS
   RRSets in a zone is discouraged, but not barred.

4.3 CNAME RRSet at a Wild Card Domain Name

   The issue of a CNAME RRSet owned by a wild card domain name has
   prompted a suggested change to the last paragraph of step 3c of the
   algorithm in 4.3.2.  The changed text appears in section 3.3.3 of
   this document.

4.4 DNAME RRSet at a Wild Card Domain Name

   Ownership of a DNAME RRSet by a wild card domain name represents a
   threat to the coherency of the DNS and is to be avoided or outright
   rejected.  Such a DNAME RRSet represents non-deterministic synthesis
   of rules fed to different caches.  As caches are fed the different
   rules (in an unpredictable manner) the caches will cease to be
   coherent.  ("As caches are fed" refers to the storage in a cache of
   records obtained in responses by recursive or iterative servers.)

   For example, assume one cache, responding to a recursive request,
   obtains the record "a.b.example. DNAME foo.bar.tld." and another
   cache obtains "b.example. DNAME foo.bar.tld.", both generated from
   the record "*.example. DNAME foo.bar.tld." by an authoritative server.

   The DNAME specification is not clear on whether DNAME records in a
   cache are used to rewrite queries.  In some interpretations, the
   rewrite occurs, in some, it is not.  Allowing for the occurrence of
   rewriting, queries for "sub.a.b.example. A" may be rewritten as
   "sub.foo.bar.tld. A" by the former caching server and may be rewritten
   as "sub.a.foo.bar.tld. A" by the latter.  Coherency is lost, an
   operational nightmare ensues.

   Another justification for banning or avoiding wildcard DNAME records
   is the observation that such a record could synthesize a DNAME owned
   by "sub.foo.bar.example." and "foo.bar.example."  There is a
   restriction in the DNAME definition that no domain exist below a
   DNAME-owning domain, hence, the wildcard DNAME is not to be permitted.

4.5 SRV RRSet at a Wild Card Domain Name

   The definition of the SRV RRset is RFC 2782 [RFC2782].  In the
   definition of the record, there is some confusion over the term
   "Name."  The definition reads as follows:

# The format of the SRV RR
...
#      _Service._Proto.Name TTL Class SRV Priority Weight Port Target
...
#   Name
#     The domain this RR refers to.  The SRV RR is unique in that the
#     name one searches for is not this name; the example near the end
#     shows this clearly.

   Do not confuse the definition "Name" with a domain name.  I.e., once
   removing the _Service and _Proto labels from the owner name of the
   SRV RRSet, what remains could be a wild card domain name but this is
   immaterial to the SRV RRSet.

   E.g.,  If an SRV record is:
        _foo._udp.*.example. 10800 IN SRV 0 1 9 old-slow-box.example.

   *.example is a wild card domain name and although it it the Name of
   the SRV RR, it is not the owner (domain name).  The owner domain name
   is "_foo._udp.*.example." which is not a wild card domain name.

   The confusion is likely based on the mixture of the specification of
   the SRV RR and the description of a "use case."

4.6 DS RRSet at a Wild Card Domain Name

   A DS RRSet owned by a wild card domain name is meaningless and
   harmless.

4.7 NSEC RRSet at a Wild Card Domain Name

   Wild card domain names in DNSSEC signed zones will have an NSEC RRSet.
   Synthesis of these records will only occur when the query exactly
   matches the record.  Synthesized NSEC RR's will not be harmful as
   they will never be used in negative caching or to generate a negative
   response.

4.8 RRSIG at a Wild Card Domain Name

   RRSIG records will be present at a wild card domain name in a signed
   zone, and will be synthesized along with data sought in a query.
   The fact that the owner name is synthesized is not a problem as the
   label count in the RRSIG will instruct the verifying code to ignore
   it.

4.9 Empty Non-terminal Wild Card Domain Name

   If a source of synthesis is an empty non-terminal, then the response
   will be one of no error in the return code and no RRSet in the answer
   section.

5. Security Considerations

   This document is refining the specifications to make it more likely
   that security can be added to DNS.  No functional additions are being
   made, just refining what is considered proper to allow the DNS,
   security of the DNS, and extending the DNS to be more predictable.

6. IANA Considerations

    None.

7. References

   Normative References

   [RFC20]   ASCII Format for Network Interchange, V.G. Cerf, Oct-16-1969

   [RFC1034] Domain Names - Concepts and Facilities, P.V. Mockapetris,
             Nov-01-1987

   [RFC1035] Domain Names - Implementation and Specification, P.V
             Mockapetris, Nov-01-1987

   [RFC1995] Incremental Zone Transfer in DNS, M. Ohta, August 1996

   [RFC2119] Key Words for Use in RFCs to Indicate Requirement Levels, S
             Bradner, March 1997

   [RFC2181] Clarifications to the DNS Specification, R. Elz and R. Bush,
             July 1997

   [RFC2308] Negative Caching of DNS Queries (DNS NCACHE), M. Andrews,
             March 1998

   [RFC2782] A DNS RR for specifying the location of services (DNS SRV),
             A. Gulbrandsen, et.al., February 2000

   [RFC4033] DNS Security Introduction and Requirements, R. Arends,
             et.al., March 2005

   [RFC4034] Resource Records for the DNS Security Extensions, R. Arends,
             et.al., March 2005

   [RFC4035] Protocol Modifications for the DNS Security Extensions,
             R. Arends, et.al., March 2005

   [RFC2672] Non-Terminal DNS Name Redirection, M. Crawford, August 1999

   Informative References

   [RFC2136] Dynamic Updates in the Domain Name System (DNS UPDATE), P.
             Vixie, Ed., S. Thomson, Y. Rekhter, J. Bound, April 1997

8. Editor

        Name:         Edward Lewis
        Affiliation:  NeuStar
        Address:      46000 Center Oak Plaza, Sterling, VA, 20166, US
        Phone:        +1-571-434-5468
        Email:        ed.lewis@neustar.biz

   Comments on this document can be sent to the editor or the mailing
   list for the DNSEXT WG, namedroppers@ops.ietf.org.

9. Others Contributing to the Document

   This document represents the work of a large working group.  The
   editor merely recorded the collective wisdom of the working group.

10. Trailing Boilerplate

   Copyright (C) The Internet Society (2005).

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   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
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Acknowledgement

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Expiration

   This document expires on or about November 11, 2005.

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