DNSEXT Working Group E. Lewis
INTERNET DRAFT NeuStar
Expiration Date: July 20, 2005 January 2005
Clarifying the Role of Wild Card Domains
in the Domain Name System
draft-ietf-dnsext-wcard-clarify-04.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on July 20, 2005.
Copyright Notice
Copyright (C) The Internet Society (2004, 2005).
Abstract
The definition of wild cards is recast from the original in RFC 1034,
in words that are more specific and in line with RFC 2119. This
document is meant to supplement the definition in RFC 1034 and not to
significantly alter the spirit or intent of that definition.
1 Introduction
In RFC 1034 [RFC1034], sections 4.3.2 and 4.3.3 describe the synthesis
of answers from special records called wildcards. The original
definitions are incomplete. This document clarifies and describes
the wildcard synthesis by adding to the discussion and making
limited modifications. Modifications are made only where necessary
to close inconsistencies that have led to interoperability issues.
1.1 Motivation
Over time many implementations have diverged 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, the impetus for this document lay in the engineering of
the DNS security extensions [RFC TBD]. With an unclear definition
of wildcards the design of authenticated denial became entangled.
Although this document is motivated by DNSSEC and the need to have a
separate document passed for the sake of DNSSEC, other motivations have
arisen. The renewed understanding of wildcards gained is worthy of being
documented.
1.2 The Original Definition
This document is intended to make just one change, 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.
There are a few passages which are changed. This may seem to
contradict the goal of not changing the original specification,
but the changes herein are required because of inconsistencies
with the wording in RFC 1034.
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 they are used is
presented. The terminology is not consistent, the word "wildcard"
is clearly defined to be a resource record. Wildcard has also been
used to refer to domain names whose first (i.e., left most or least
significant) label consists of an asterisk.
1.3 The Clarification
The clarification effort can be divided into three sections:
o The introduction of new terminology for clarity of the discussion
o Changes to the wording of passages of RFC 1034 prompted by discoveries of
conflicting concepts
o Descriptions of special resource record types in the context of wildcards.
1.3.1 New Terms
The term "wildcard" has become so overloaded it is virtually useless
as a description. A few new terms will be introduced to be more
descriptive. The new terms that will be introduced are:
Asterisk Label - a label consisting of an asterisk ("*") and no
other characters.
Wild Card Domain Name - a domain name whose least significant
label (first when reading left to right) is an asterisk label.
Other labels might also be asterisk labels.
Source of Synthesis - a wild card domain name when it is consulted in
the final paragraph of step 3, part c of RFC 1034's 4.3.2 algorithm.
Closest Encloser - in RFC 1034's 4.3.2 algorithm, the name at which
the last match was possible in step 3, part c. This is the longest
sequence of exactly matching labels from the root downward in both the
query name (QNAME) and in the zone being examined.
Label Match - two labels are equivalent if the label type and label
length are both the same and if the labels are case-independent
equivalent strings. Pattern matching is not involved.
These terms will be more fully described as needed later. These
terms will be used to describe a few changes to the words in RFC
1034. A summary of the changes appear next and will be fully
covered in later sections.
Note that labels other than the asterisk label which contain
asterisks have no special significance or terminology in this
document; thus the fact that a domain names starts with an
asterisk is also of no special significance (and has no special
terminology) unless its first label is the asterisk label, e.g.,
"*foo.example." has no special significance).
1.3.2 Changed Text
The definition of "existence" is changed, superficially, to exclude
empty domains that have no subdomains with resource records. This
change will not be apparent to implementations; it is needed to
make descriptions more concise.
In RFC 1034, there is text that seems to prohibit having two asterisk
labels in a wild card domain name. There is no further discussion,
no prescribed error handling, nor enforcement described. With this
document implementations will have to account for such a name's use.
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.
1.3.3 Considerations with Special Types
This clarification will describe in some detail the semantics of
wildcard CNAME RRSets, wildcard NS RRSets, wildcard SOA RRSets,
wildcard DNAME RRSets [RFC 2672], 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.
By the definition in RFC 1034, there can be no empty non-terminal
"wildcards" ("RRs are called wildcards"). However, in the algorithm,
it is possible that an empty non-terminal is sought as the potential
owner of a "wildcard." This is one example of why the ordering of the
discussion in RFC 1034 is confusing.
1.4 Standards Terminology
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 the document entitled
"Key words for use in RFCs to Indicate Requirement Levels." [RFC2119]
Quotations of RFC 1034 (as has already been done once above) are
denoted by a '#' in the leftmost column.
2 "Wildcard"
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).
Tackling the latter first, there are two objectives in defining a
means to identify a resource record set as a source of synthesis.
First, to simplify implementations, one objective is to encode synthesis
rules into the domain tree, i.e., avoiding a special data store for
synthesis is desirable. The second objective impacts interoperability,
that is a master server of one implementation has to be able to
send the synthesis instructions to the slaves. Although there are
alternatives to the use of zone transfers via port 53, a truly
interoperable record synthesis approach has to be able to insert the
synthesis instructions into a zone transfer.
The objectives in describing the synthesis of records in the context
of the name server algorithm include knowing when to employ the
process of synthesis and how the synthesis is carried out.
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.
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)
This is "*" in presentation format.
The first octet is the normal label type and length for a 1 octet
long label, the second octet is the ASCII representation [RFC 20] for
the '*' character. In RFC 1034, ASCII encoding is assumed to be the
character encoding.
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." This is mentioned to help maintain some
orientation between this clarification and RFC 1034. Keep in mind,
that in "Clarifications to the DNS Specification" [RFC 2181] the name
of the basic unit of DNS data became the resource record set (RRSet) and
not the resource record.
2.1.2 Variations on Wild Card Domain Names
Labels other than the asterisk label which contain the ASCII
representation of the asterisk (0x2a) have no significance for the
purposes of this document.
RFC 1034 and RFC 1035 do not explicitly mention the case in which a
domain name might be something like "the*.example." The
interpretation is that this domain name in a zone would only match
queries for "the*.example." and not have any other role. An
asterisk ('*') occurring other than as the sole character in
a label is simply a character forming part of the label and has no
special meaning. This is not an asterisk label, simply a label
an asterisk in it. The same is true for "**.example." and
"*the.example."
The interpretation of a wild card domain specification which is not a
leaf domain is not clearly defined in RFC 1034. E.g., sub.*.example.,
is not discussed, not barred. In wanting to minimize changes from
the original specification, such names are permitted. Although
"sub.*.example." is not a wild card domain name, "*.example." is.
RRSets used to synthesize records can be owned by a wild card domain
name that has subdomains.
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 covers names like "*.foo.*.example." The pre-RFC2119 wording uses
"should not" which has an ambiguous meaning. The specification does not
proscribe actions upon seeing such a name, such as whether or not a
zone containing the name should fail to be served. What if a dynamic
update (RFC2136) requested to add the name to the zone? The failure
semantics are not defined.
The recommendation is that implementations ought to anticipate the
appearance of such names but generally discourage their use in
operations. No standards statement, such as "MUST NOT" nor "SHOULD NOT"
is made here.
The interpretation of this is, when seeking a wild card domain name
for the purposes of record synthesis, an implementation need not to
check the domain name for subdomains.
It is possible that a wild card domain name is an empty non-terminal.
(See the upcoming sections on empty non-terminals.) In this case,
the lookup will terminate as would any empty non-terminal match.
2.2 Existence Rules
The notion that a domain name 'exists' arises numerous times in
discussions about the wildcard concept. RFC 1034 raises the issue
of existence in a number of places, usually in reference to
non-existence and in reference to processing involving wildcards.
RFC 1034 contains algorithms that describe how domain names impact
the preparation of an answer and does define wildcards as a means of
synthesizing answers. Because of this a discussion on wildcards
needs to cover a definition of existence.
To help clarify the topic of wild cards, a positive definition of
existence is needed. Complicating matters, though, is the
realization that existence is relative. To an authoritative server,
a domain name exists if the domain name plays a role following the
algorithms of preparing a response. To a resolver, a domain name
exists if there is any data available corresponding to the name. The
difference between the two is the synthesis of records according to a
wildcard.
For the purposes of this document, the point of view of an
authoritative server is more interesting. A domain name is said to
exist if it plays a role in the execution of the algorithms in RFC 1034.
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.
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
| |
| |
_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=_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)
To the server, all of the domains in the tree exist. The resolver will
get answers to some names off the tree, thanks to synthesis.
2.2.2 Empty Non-terminals
Empty non-terminals are domain names that own no resource records but
have subdomains that do. This is defined 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. According to the definition of
existence in this document, empty non-terminals do exist at the
server.
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 [RFC 1035]. 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 clarified by the following paragraph:
A node is considered to have an impact on the algorithms of
4.3.2 if it is a leaf node with any resource sets or an interior
node (with or without a resource set) that has a subdomain that
is a leaf node with a resource set. A QNAME and QCLASS matching
an existing node never results in a response code of
authoritative name error (RCODE==3).
The terminology in the above paragraph is chosen to remain as close
to that in the original document. The term "with" is a alternate
form for "owning" in this case, hence "a leaf node owning resources
sets, or an interior node, owning or not owning any resource set,
that has a leaf node owning a resource set as a subdomain," is the
proper interpretation of the middle sentence. The phrase "resource
set" appears in the original text of RFC 1034, this would now be
replaced by "RRSet."
As an aside, an "authoritative name error", response code (RCODE) 3,
has been called NXDOMAIN in some RFCs, such as RFC 2136 [RFC 2136].
NXDOMAIN is the mnemonic assigned to such an error by at least one
implementation of DNS.
Summarizing the discussion on existence in non-RFC1034 words:
An authoritative server is to treat a domain name as existing
during the execution of the algorithms in RFC 1034 when the
domain name conforms to the following definition. A domain name
is defined to exist if the domain name is on the domain tree and
either owns data or has a subdomain that exists.
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 not own a wildcard (record)
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 On a Response
The description of how wild cards 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 is directly quoted in lines that begin with a '#' sign.
Commentary is interleaved.
There is a documentation issue deserving some explanation. 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.
Another issue needing explanation is that RFC 1034 is a full
standard. There is another RFC, RFC 2672, which makes, or proposes
an adjustment to RFC 1034's section 4.3.2 for the sake of the DNAME
RR. RFC 2672 is a proposed standard. The dilemma in writing these
clarifications is knowing which document is the one being clarified.
Fortunately, the difference between RFC 1034 and RFC 2672 is not
significant with respect to wild card synthesis, so this document
will continue to state that it is clarifying RFC 1034. If RFC 2672
progresses along the standards track, it will need to refer to
modifying RFC 1034's algorithm as amended here.
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.
If an implementation were to attempt to synthesize zones, this would be
the step to do this. Note though that each name server listed in the NS
RRSet for the synthesized zone would have to coherently synthesize the
zone.
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.)
The process of label matching a query name ends in exactly one of three
choices, the parts 'a', 'b', and 'c'. 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.
Parts 'a' and 'b' are not an issue for this clarification as they do not
relate to record synthesis. Part 'a' generally covers a situation in
which all of the labels in the query name have a (label) match in the tree.
Part 'b' generally covers a situation in which any label in the query
name (label) matches a tree label and the tree label has a NS RRSet.
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 a
# the "*" label exists.
To help describe the process of looking 'to see if a [sic] the "*"
label exists' a term has been coined to describe the last label
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
the 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.
Other terms have been coined on the mailing list in the past. E.g.,
it has been said that existing names block the application of
wildcard records. This is still an appropriate viewpoint, but
replacing this notion with the closest encloser and source of
synthesis terminology depicts the wildcard process is more clearly.
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.
3.3.3 Non-existent Source of Synthesis
In RFC 1034:
# 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.
The above passage is clear, evidenced by the lack of discussion and
mis-implementation of it over the years. It is included for
completeness only. (No attempt is made to re-interpret it lest
a mistake in editing leads to confusion.)
3.3.4 Type Matching
RFC 1034 concludes part 'c' with this:
# 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.
This 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 a change has been made.
The change is to add the following text:
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
Five types of RRSets owned by a wild card domain name have caused
confusion. Four explicit types causing confusion are SOA, NS, CNAME,
DNAME, and the fifth type - "none."
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., if *.example. has an SOA record, then only a query like
QNAME=*.example., QTYPE=A, QCLASS=IN would see it. A query like
QNAME=foo.example., QTYPE=A, QCLASS=IN would not see it - a different
zone would have been picked in Step 2. A QNAME of www.*.example.
would result in a query referencing the *.example zone.
4.2. NS RRSet at a Wild Card Domain Name
The semantics of a wild card domain name's ownership of a NS RRSet
has been unclear. Looking through RFC 1034, the recommendation
is to have the NS RRSet act the same a any non-special type, e.g.,
like an A RRSet.
If the NS RRSet in question is at the top of the zone, i.e., the
name also owns an SOA RRSet, the QNAME equals the zone name. This
would trigger part 'a' of Step 3.
In any other case, the wild card domain name owned NS RRSet would
be the only RRSet (prior to changes instituted by DNSSEC) at the
node by DNS rules. If the QNAME equals the wild card domain name
or is a subdomain of it, then the node would be considered in part
'b' of Step 3. [should dnssec be left out of this?]
Note that there is no synthesis of records in the authority section
because part 'b' does not specify synthesis. The referral returned
would have the wild card domain name in the authority section unchanged.
If the QNAME is not the same as the wild card domain name nor a
subdomain of it, then part 'c' of Step 3 has been triggered. Once
part 'c' is entered, there is no reverting to part 'b' - i.e.,
once an NS RRSet is synthesized it does not mean that the server has
to consider the name delegated away. I.e., the server is not
synthesizing a record (the NS RRSet) that means the server does not
have the right to synthesize. (Only an authoritative server can
perform synthesis. By synthesizing an NS RRSet, it appears that the
authority for the name has been delegated to another authority.)
In summation, an NS RRSet at a wild card domain name will not result in
the generation of referral messages for non-existent domains.
4.3. CNAME RRSet at a Wild Card Domain Name
The issue of a CNAME RRSet owned by wild card domain names 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 3.3.4 of this document.
4.4. DNAME RRSet at a Wild Card Domain Name
The specification of the DNAME RR, which is at the proposed level of
standardization, is not as mature as the full standard in RFC 1034.
Because of this, or the reason for this is, there appears to be a
a number of issues with that definition and it's rewrite of the algorithm
in 4.3.2. For the time being, when it comes to wild card processing
issues, a DNAME can be considered to be a CNAME synthesizer. A DNAME
at a wild card domain name is effectively the same as a CNAME at a
wild card domain name.
4.5 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. References
Normative References
[RFC 20] ASCII Format for Network Interchange, V.G. Cerf, Oct-16-1969
[RFC 1034] Domain Names - Concepts and Facilities, P.V. Mockapetris,
Nov-01-1987
[RFC 1035] Domain Names - Implementation and Specification, P.V
Mockapetris, Nov-01-1987
[RFC 2119] Key Words for Use in RFCs to Indicate Requirement Levels, S
Bradner, March 1997
[RFC 2181] Clarifications to the DNS Specification, R. Elz and R. Bush,
July 1997.
Informative References
[RFC 2136] Dynamic Updates in the Domain Name System (DNS UPDATE), P.
Vixie, Ed., S. Thomson, Y. Rekhter, J. Bound, April 1997
[RFC 2535] Domain Name System Security Extensions, D. Eastlake, March 1999
[RFC 2672] Non-Terminal DNS Name Redirection, M. Crawford, August 1999
7. Others Contributing to This Document
Others who have been editors of this document: Bob Halley.
Others who have directly caused text to appear in the document: Alex
Bligh, Robert Elz, Paul Vixie and Olaf Kolkman.
Many others have indirect influences on the content.
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. Trailing Boilerplate
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78 and
except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. The IETF invites any interested party to
bring to its attention any copyrights, patents or patent
applications, or other proprietary rights that may cover technology
that may be required to implement this standard. Please address the
information to the IETF at ietf-ipr@ietf.org.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Expiration
This document expires on or about July 20, 2005.
Datatracker
Report a datatracker bug
draft-ietf-dnsext-wcard-clarify-04
Internet-Draft
| Document | Document type |
This is an older version of an Internet-Draft that was ultimately published as RFC 4592.
Expired & archived
|
|
|---|---|---|---|
| Select version | |||
| Compare versions | |||
| Author | |||
| RFC stream |
|
||
| Other formats | |||
| Additional resources | Mailing list discussion |