draft-ietf-dnsext-wcard-clarify-01.txt   draft-ietf-dnsext-wcard-clarify-02.txt 
Internet Engineering Task Force B. Halley
Internet-Draft Nominum dnsext Working Group B. Halley
Internet Draft Nominum
Expiration Date: March 2004
E. Lewis E. Lewis
ARIN ARIN
August 10, 2003 Expires: February 10, 2004 September 2003
Clarifying the Role of Wild Card Domains Clarifying the Role of Wild Card Domains
in the Domain Name System in the Domain Name System
<draft-ietf-dnsext-wcard-clarify-01.txt>
draft-ietf-dnsext-wcard-clarify-02.txt
Status of this Memo Status of this Memo
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provisions of Section 10 of RFC2026. of Section 10 of RFC2026.
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Abstract Abstract
The definition of wild cards is recast from the original in RFC 1034, 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 in words that are more specific and in line with RFC 2119. This
is meant to supplement the definition in RFC 1034 and to alter neither document is meant to supplement the definition in RFC 1034 and to
the spirit nor intent of that definition. alter neither the spirit nor intent of that definition.
1 Introduction Table of Contents
Abstract ................................................ 1
1 Introduction ............................................ 2
1.1 Document Limits ......................................... 3
1.2 Existence ............................................... 4
1.3 An Example .............................................. 4
1.4 Empty Non-terminals ..................................... 5
1.5 Terminology ............................................. 6
2 Defining the Wild Card Domain Name ...................... 7
3 Defining Existence ...................................... 8
4 Impact of a Wild Card In a Query or in RDATA ............ 8
5 Impact of a Wild Card Domain On a Response .............. 9
6 Considerations with Special Types ....................... 12
6.1 SOA RR's at a Wild Card Domain Name ..................... 12
6.2 NS RR's at a Wild Card Domain Name ...................... 12
6.3 CNAME RR's at a Wild Card Domain Name ................... 13
6.4 DNAME RR's at a Wild Card Domain Name ................... 13
7 Security Considerations ................................. 14
8 References .............................................. 14
9 Others Contributing to This Document .................... 14
10 Editors ................................................. 15
Appendix A: Subdomains of Wild Card Domain Names ........ 16
Full Copyright Statement ................................ 18
Acknowledgement ......................................... 18
1. Introduction
The first section of this document will give a crisp overview of what The first section of this document will give a crisp overview of what
is begin defined, as well as the motivation rewording of an original document is begin defined, as well as the motivation rewording of an original
and making a change to bring the specification in line with implementations. document and making a change to bring the specification in line with
Examples are included to help orient the reader. implementations. Examples are included to help orient the reader.
Wild card domain names are defined in Section 4.3.3. of RFC 1034 as Wild card domain names are defined in Section 4.3.3. of RFC 1034 as
"instructions for synthesizing RRs." [RFC1034] The meaning of this is "instructions for synthesizing RRs." [RFC1034]. The meaning of this
that a specific, special domain name is used to construct responses in is that a specific, special domain name is used to construct
instances in which the query name is not otherwise represented in a zone. responses in instances in which the query name is not otherwise
represented in a zone.
A wild card domain name has a specific range of influence on query names A wild card domain name has a specific range of influence on query
(QNAMEs) within a given class, which is rooted at the domain name names (QNAMEs) within a given class, which is rooted at the domain
containing the wild card label, and is limited by explicit entries, zone name containing the wild card label, and is limited by explicit
cuts and empty non-terminal domains (see section 1.3 of this document). entries, zone cuts and empty non-terminal domains (see section 1.3 of
this document).
Note that a wild card domain name has no special impact on the search Note that a wild card domain name has no special impact on the search
for a query type (QTYPE). If a domain name is found that matches the for a query type (QTYPE). If a domain name is found that matches the
QNAME (exact or a wild card) but the QTYPE is not found at that point, QNAME (exact or a wild card) but the QTYPE is not found at that
the proper response is that there is no data available. The search point, the proper response is that there is no data available. The
does not continue on to seek other wild cards that might match the QTYPE. search does not continue on to seek other wild cards that might match
To illustrate, a wild card owning an MX RR does not 'cover' other names the QTYPE. To illustrate, a wild card owning an MX RR does not
in the zone that own an A RR. There are certain special case RR types 'cover' other names in the zone that own an A RR. There are certain
that will be singled out for discussion, the SOA RR, NS RR, CNAME RR, special case RR types that will be singled out for discussion, the
and DNAME RR. SOA RR, NS RR, CNAME RR, and DNAME RR.
Why is this document needed? Empirical evidence suggests that the Why is this document needed? Empirical evidence suggests that the
words in RFC 1034 are not clear enough. There exist a number of words in RFC 1034 are not clear enough. There exist a number of
implementations that have strayed (each differently) from that definition. implementations that have strayed (each differently) from that
There also exists a misconception of operators that the wild card can be definition. There also exists a misconception of operators that the
used to add a specific RR type to all names, such as the MX RR example wild card can be used to add a specific RR type to all names, such as
cited above. This document is also needed as input to efforts to extend the MX RR example cited above. This document is also needed as input
DNS, such as the DNS Security Extensions [RFC 2535]. Lack of a clear to efforts to extend DNS, such as the DNS Security Extensions [RFC
base specification has proven to result in extension documents that 2535]. Lack of a clear base specification has proven to result in
have unpredictable consequences. (This is true in general, not just extension documents that have unpredictable consequences. (This is
for DNS.) true in general, not just for DNS.)
Another reason this clarification is needed is to answer questions Another reason this clarification is needed is to answer questions
regarding authenticated denial of existence, a service introduced in the regarding authenticated denial of existence, a service introduced in
DNS Security Extensions [RFC 2535]. Prior to the work leading up to this the DNS Security Extensions [RFC 2535]. Prior to the work leading up
document, it had been feared that a large number of proof records (NXTs) to this document, it had been feared that a large number of proof
might be needed in each reply because of the unknown number of potential records (NXTs) might be needed in each reply because of the unknown
wild card domains that were thought to be applicable. One outcome of this number of potential wild card domains that were thought to be
fear is a now discontinued document solving a problem that is now known applicable. One outcome of this fear is a now discontinued document
not to exist. I.e., this clarification has the impact of defending against solving a problem that is now known not to exist. I.e., this
unwarranted protocol surgery. It is not "yet another" effort to just clarification has the impact of defending against unwarranted
rewrite the early specifications for the sake of purity. protocol surgery. It is not "yet another" effort to just rewrite the
early specifications for the sake of purity.
Although the effort to define the DNS Security Extensions has prompted this Although the effort to define the DNS Security Extensions has
document, the clarifications herein relate to basic DNS only. No DNS prompted this document, the clarifications herein relate to basic DNS
Security Extensions considerations are mentioned in the document. only. No DNS Security Extensions considerations are mentioned in the
document.
1.1 Document Limits 1.1. Document Limits
This document limits itself to reinforcing the concepts in RFC 1034. In This document limits itself to reinforcing the concepts in RFC 1034.
the effort to do this, a few issues have been discussed that change In the effort to do this, a few issues have been discussed that
parts of what is in RFC 1034. The discussions have been held within the change parts of what is in RFC 1034. The discussions have been held
DNS Extensions Working Group. within the DNS Extensions Working Group.
Briefly, the issues raised include: Briefly, the issues raised include:
- The lack of clarity in the definition of domain name existence - The lack of clarity in the definition of domain name existence
- Implications of a wild card domain name owning any of the following - Implications of a wild card domain name owning any of the
resource record sets: DNAME [RFC 2672], CNAME, NS, and SOA following resource record sets: DNAME [RFC 2672], CNAME, NS, and
SOA
- Whether RFC 1034 meant to allow special processing of CNAME RR's - Whether RFC 1034 meant to allow special processing of CNAME RR's
owned by wild card domain names owned by wild card domain names
1.2 Existence 1.2. Existence
The notion that a domain name 'exists' will arise numerous times in this The notion that a domain name 'exists' will arise numerous times in
discussion. RFC 1034 raises the issue of existence in a number of places, this discussion. RFC 1034 raises the issue of existence in a number
usually in reference to non-existence and often in reference to processing of places, usually in reference to non-existence and often in
involving wild card domain names. RFC 1034 contains algorithms that reference to processing involving wild card domain names. RFC 1034
describe how domain names impact the preparation of an answer and does contains algorithms that describe how domain names impact the
define wild cards as a means of synthesizing answers. Because of this preparation of an answer and does define wild cards as a means of
a discussion on wild card domain names has to start with the issue of synthesizing answers. Because of this a discussion on wild card
existence. domain names has to start with the issue of existence.
To help clarify the topic of wild cards, a positive definition of existence To help clarify the topic of wild cards, a positive definition of
is needed. Complicating matters, though, is the realization that existence existence is needed. Complicating matters, though, is the
is relative. To an authoritative server, a domain name exists if the realization that existence is relative. To an authoritative server,
domain name plays a role following the algorithms of preparing a response. a domain name exists if the domain name plays a role following the
To a resolver, a domain name exists if there is any data available algorithms of preparing a response. To a resolver, a domain name
corresponding to the name. The difference between the two is the synthesis exists if there is any data available corresponding to the name. The
of records according to a wild card. difference between the two is the synthesis of records according to a
wild card.
For the purposes of this document, the point of view of an authoritative For the purposes of this document, the point of view of an
server is adopted. A domain name is said to exist if it plays a role in authoritative server is adopted. A domain name is said to exist if
the execution of the algorithms in RFC 1034. it plays a role in the execution of the algorithms in RFC 1034.
1.3 An Example 1.3. An Example
For example, consider this wild card domain name: *.example. Any query For example, consider this wild card domain name: *.example. Any
name under example. is a candidate to be matched (answered) by this wild query name under example. is a candidate to be matched (answered) by
card, i.e., to have an response returned that is synthesized from the wild this wild card, i.e., to have an response returned that is
card's RR sets. Although any name is a candidate, not all queries will synthesized from the wild card's RR sets. Although any name is a
match. candidate, not all queries will match.
To further illustrate this, consider this zone: To further illustrate this, consider this zone:
$ORIGIN example. $ORIGIN example.
@ IN SOA @ IN SOA
NS NS
NS NS
* TXT "this is a wild card" * TXT "this is a wild card"
MX 10 mailhost.example. MX 10 mailhost.example.
host1 A 10.0.0.1 host1 A 10.0.0.1
skipping to change at line 154 skipping to change at page 5, line 19
NS NS
NS NS
* TXT "this is a wild card" * TXT "this is a wild card"
MX 10 mailhost.example. MX 10 mailhost.example.
host1 A 10.0.0.1 host1 A 10.0.0.1
_ssh._tcp.host1 SRV _ssh._tcp.host1 SRV
_ssh._tcp.host2 SRV _ssh._tcp.host2 SRV
subdel NS subdel NS
The following queries would be synthesized from the wild card: The following queries would be synthesized from the wild card:
QNAME=host3.example. QTYPE=MX, QCLASS=IN QNAME=host3.example. QTYPE=MX, QCLASS=IN
the answer will be a "host3.example. IN MX ..." the answer will be a "host3.example. IN MX ..."
QNAME=host3.example. QTYPE=A, QCLASS=IN QNAME=host3.example. QTYPE=A, QCLASS=IN
the answer will reflect "no error, but no data" the answer will reflect "no error, but no data"
because there is no A RR set at '*' because there is no A RR set at '*'
The following queries would not be synthesized from the wild card: The following queries would not be synthesized from the wild card:
QNAME=host1.example., QTYPE=MX, QCLASS=IN QNAME=host1.example., QTYPE=MX, QCLASS=IN
because host1.example. exists because host1.example. exists
QNAME=_telnet._tcp.host1.example., QTYPE=SRV, QCLASS=IN QNAME=_telnet._tcp.host1.example., QTYPE=SRV, QCLASS=IN
because _tcp.host1.example. exists (without data) because _tcp.host1.example. exists (without data)
QNAME=_telnet._tcp.host2.example., QTYPE=SRV, QCLASS=IN QNAME=_telnet._tcp.host2.example., QTYPE=SRV, QCLASS=IN
because host2.example. exists (without data) because host2.example. exists (without data)
QNAME=host.subdel.example., QTYPE=A, QCLASS=IN QNAME=host.subdel.example., QTYPE=A, QCLASS=IN
because subdel.example. exists and is a zone cut because subdel.example. exists and is a zone cut
To the server, the following domains are considered to exist in the zone: To the server, the following domains are considered to exist in the
*, host1, _tcp.host1, _ssh._tcp.host1, host2, _tcp.host2, _ssh._tcp.host2, zone: *, host1, _tcp.host1, _ssh._tcp.host1, host2, _tcp.host2,
and subdel. To a resolver, many more domains appear to exist via the _ssh._tcp.host2, and subdel. To a resolver, many more domains appear
synthesis of the wild card. to exist via the synthesis of the wild card.
1.4 Empty Non-terminals 1.4. Empty Non-terminals
Empty non-terminals are domain names that own no data but have subdomains. Empty non-terminals are domain names that own no data but have
This is defined in section 3.1 of RFC 1034: subdomains. This is defined in section 3.1 of RFC 1034:
# The domain name space is a tree structure. Each node and leaf on the # 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 # tree corresponds to a resource set (which may be empty). The domain
# system makes no distinctions between the uses of the interior nodes and # system makes no distinctions between the uses of the interior nodes and
# leaves, and this memo uses the term "node" to refer to both. # leaves, and this memo uses the term "node" to refer to both.
The parenthesized "which may be empty" specifies that empty non-terminals The parenthesized "which may be empty" specifies that empty non-
are explicitly recognized. According to the definition of existence in terminals are explicitly recognized. According to the definition of
this document, empty non-terminals do exist at the server. existence in this document, empty non-terminals do exist at the
server.
Carefully reading the above paragraph can lead to an interpretation that Carefully reading the above paragraph can lead to an interpretation
all possible domains exist - up to the suggested limit of 255 octets for that all possible domains exist - up to the suggested limit of 255
a domain name [RFC 1035]. For example, www.example. may have an A RR, and octets for a domain name [RFC 1035]. For example, www.example. may
as far as is practically concerned, is a leaf of the domain tree. But the have an A RR, and as far as is practically concerned, is a leaf of
definition can be taken to mean that sub.www.example. also exists, albeit the domain tree. But the definition can be taken to mean that
with no data. By extension, all possible domains exist, from the root on sub.www.example. also exists, albeit with no data. By extension, all
down. As RFC 1034 also defines "an authoritative name error indicating possible domains exist, from the root on down. As RFC 1034 also
that the name does not exist" in section 4.3.1, this is not the intent defines "an authoritative name error indicating that the name does
of the original document. not exist" in section 4.3.1, this is not the intent of the original
document.
RFC1034's wording is to be clarified by adding the following paragraph: RFC1034's wording is to be clarified by adding the following
paragraph:
A node is considered to have an impact on the algorithms of 4.3.2 A node is considered to have an impact on the algorithms of
if it is a leaf node with any resource sets or an interior node, 4.3.2 if it is a leaf node with any resource sets or an interior
with or without a resource set, that has a subdomain that is a leaf node, with or without a resource set, that has a subdomain that
node with a resource set. A QNAME and QCLASS matching an existing is a leaf node with a resource set. A QNAME and QCLASS matching
node never results in a response return code of authoritative name an existing node never results in a response return code of
error. authoritative name error.
The terminology in the above paragraph is chosen to remain as close to The terminology in the above paragraph is chosen to remain as close
that in the original document. The term "with" is a alternate form for to that in the original document. The term "with" is a alternate
"owning" in this case, hence "a leaf node owning resources sets, or an form for "owning" in this case, hence "a leaf node owning resources
interior node, owning or not owning any resource set, that has a leaf sets, or an interior node, owning or not owning any resource set,
node owning a resource set as a subdomain," is the proper interpretation that has a leaf node owning a resource set as a subdomain," is the
of the middle sentence. proper interpretation of the middle sentence.
As an aside, an "authoritative name error" has been called NXDOMAIN in As an aside, an "authoritative name error" has been called NXDOMAIN
some RFCs, such as RFC 2136 [RFC 2136]. NXDOMAIN is the mnemonic assigned in some RFCs, such as RFC 2136 [RFC 2136]. NXDOMAIN is the mnemonic
to such an error by at least one implementation of DNS. As this assigned to such an error by at least one implementation of DNS. As
mnemonic is specific to implementations, it is avoided in the remainder this mnemonic is specific to implementations, it is avoided in the
of this document. remainder of this document.
1.5 Terminology 1.5. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in the document entitled document are to be interpreted as described in the document entitled
"Key words for use in RFCs to Indicate Requirement Levels." [RFC2119] "Key words for use in RFCs to Indicate Requirement Levels." [RFC2119]
Requirements are denoted by paragraphs that begin with with the following Requirements are denoted by paragraphs that begin with with the
convention: 'R'<sect>.<count>. following convention: 'R'<sect>.<count>.
Quotations of RFC 1034 (as has already been done once above) are denoted by Quotations of RFC 1034 (as has already been done once above) are
a '#' in the leftmost column. denoted by a '#' in the leftmost column.
2 Defining the Wild Card Domain Name 2. Defining the Wild Card Domain Name
A wild card domain name is defined by having the initial label be: A wild card domain name is defined by having the initial label be:
0000 0001 0010 1010 (binary) = 0x01 0x2a (hexadecimal) 0000 0001 0010 1010 (binary) = 0x01 0x2a (hexadecimal)
This defines domain names that may play a role in being a wild card, that This defines domain names that may play a role in being a wild card,
is, being a source for synthesized answers. Domain names conforming to that is, being a source for synthesized answers. Domain names
this definition that appear in queries and RDATA sections do not have conforming to this definition that appear in queries and RDATA
any special role. These cases will be described in more detail in sections do not have any special role. These cases will be described
following sections. in more detail in following sections.
R2.1 A domain name that is to be interpreted as a wild card MUST begin R2.1 A domain name that is to be interpreted as a wild card MUST
with a label of '0000 0001 0010 1010' in binary. begin with a label of '0000 0001 0010 1010' in binary.
The first octet is the normal label type and length for a 1 octet long The first octet is the normal label type and length for a 1 octet
label, the second octet is the ASCII representation [RFC 20] for the long label, the second octet is the ASCII representation [RFC 20] for
'*' character. In RFC 1034, ASCII encoding is assumed to be the character the '*' character. In RFC 1034, ASCII encoding is assumed to be the
encoding. character encoding.
In the master file formats used in RFCs, a "*" is a legal representation In the master file formats used in RFCs, a "*" is a legal
for the wild card label. Even if the "*" is escaped, it is still representation for the wild card label. Even if the "*" is escaped,
interpreted as the wild card when it is the only character in the label. it is still interpreted as the wild card when it is the only
character in the label.
R2.2. A server MUST treat a wild card domain name as the basis of R2.2 A server MUST treat a wild card domain name as the basis of
synthesized answers regardless of any "escape" sequences in synthesized answers regardless of any "escape" sequences in the
the input format. input format.
RFC 1034 and RFC 1035 ignore the case in which a domain name might be RFC 1034 and RFC 1035 ignore the case in which a domain name might be
"the*.example.com." The interpretation is that this domain name in a "the*.example.com." The interpretation is that this domain name in a
zone would only match queries for "the*.example.com" and not have any zone would only match queries for "the*.example.com" and not have any
other role. other role.
Note: By virtue of this definition, a wild card domain name may have a Note: By virtue of this definition, a wild card domain name may have
subdomain. The subdomain (or sub-subdomain) itself may also be a wild a subdomain. The subdomain (or sub-subdomain) itself may also be a
card. E.g., *.*.example. is a wild card, so is *.sub.*.example. wild card. E.g., *.*.example. is a wild card, so is *.sub.*.example.
More discussion on this is given in Appendix A. More discussion on this is given in Appendix A.
3 Defining Existence 3. Defining Existence
As described in the Introduction, a precise definition of existence is As described in the Introduction, a precise definition of existence
needed. is needed.
R3.1 An authoritative server MUST treat a domain name as existing during R3.1 An authoritative server MUST treat a domain name as existing
the execution of the algorithms in RFC 1034 when the domain name during the execution of the algorithms in RFC 1034 when the
conforms to the following definition. A domain name is defined domain name conforms to the following definition. A domain name
to exist if the domain name owns data and/or has a subdomain that is defined to exist if the domain name owns data and/or has a
exists. subdomain that exists.
Note that at a zone boundary, the domain name owns data, including the Note that at a zone boundary, the domain name owns data, including
NS RR set. At the delegating server, the NS RR set is not authoritative, the NS RR set. At the delegating server, the NS RR set is not
but that is of no consequence here. The domain name owns data, therefore, authoritative, but that is of no consequence here. The domain name
it exists. owns data, therefore, it exists.
R3.2 An authoritative server MUST treat a domain name that has neither R3.2 An authoritative server MUST treat a domain name that has
a resource record set nor an existing subdomain as non-existent when neither a resource record set nor an existing subdomain as non-
executing the algorithm in section 4.3.2. of RFC 1034. existent when executing the algorithm in section 4.3.2. of RFC
1034.
A note on terminology. A domain transcends zones, i.e., all DNS data is A note on terminology. A domain transcends zones, i.e., all DNS data
in the root domain but segmented into zones of control. In this document, is in the root domain but segmented into zones of control. In this
there are references to a "domain name" in the context of existing "in a document, there are references to a "domain name" in the context of
zone." In this usage, a domain name is the root of a domain, not the entire existing "in a zone." In this usage, a domain name is the root of a
domain. The domain's root point is said to "exist in a zone" if the zone domain, not the entire domain. The domain's root point is said to
is authoritative for the name. RR sets existing in a domain need not be "exist in a zone" if the zone is authoritative for the name. RR sets
owned by the domain's root domain name, but are owned by other domain existing in a domain need not be owned by the domain's root domain
names in the domain. name, but are owned by other domain names in the domain.
4 Impact of a Wild Card Domain In a Query Message or in an RDATA field 4. Impact of a Wild Card In a Query or in RDATA
When a wild card domain name appears in a question, e.g., the query name When a wild card domain name appears in a question, e.g., the query
is "*.example.", the response in no way differs from any other query. name is "*.example.", the response in no way differs from any other
In other words, the wild card label in a QNAME has no special meaning, query. In other words, the wild card label in a QNAME has no special
and query processing will proceed using '*' as a literal query name. meaning, and query processing will proceed using '*' as a literal
query name.
R4.1 A wild card domain name acting as a QNAME MUST be treated as any R4.1 A wild card domain name acting as a QNAME MUST be treated as any
other QNAME, there MUST be no special processing accorded it. other QNAME, there MUST be no special processing accorded it.
If a wild card domain name appears in the RDATA of a CNAME RR or any If a wild card domain name appears in the RDATA of a CNAME RR or any
other RR that has a domain name in it, the same rule applies. In the other RR that has a domain name in it, the same rule applies. In the
instance of a CNAME RR, the wild card domain name is used in the same instance of a CNAME RR, the wild card domain name is used in the same
manner of as being the original QNAME. For other RR's, rules vary manner of as being the original QNAME. For other RR's, rules vary
regarding what is done with the domain name(s) appearing in them, regarding what is done with the domain name(s) appearing in them, in
in no case does the wild card hold special meaning. no case does the wild card hold special meaning.
R4.2 A wild card domain name appearing in any RR's RDATA MUST be treated R4.2 A wild card domain name appearing in any RR's RDATA MUST be
as any other domain name in that situation, there MUST be no special treated as any other domain name in that situation, there MUST
processing accorded it. be no special processing accorded it.
5 Impact of a Wild Card Domain On a Response 5. Impact of a Wild Card Domain On a Response
The description of how wild cards impact response generation is in RFC The description of how wild cards impact response generation is in
1034, section 4.3.2. That passage contains the algorithm followed by a RFC 1034, section 4.3.2. That passage contains the algorithm
server in constructing a response. Within that algorithm, step 3, part followed by a server in constructing a response. Within that
'c' defines the behavior of the wild card. The algorithm is directly algorithm, step 3, part 'c' defines the behavior of the wild card.
quoted in lines that begin with a '#' sign. Commentary is interleaved. 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 There is a documentation issue deserving some explanation. The
in RFC 1034, section 4.3.2. is not intended to be pseudo code, i.e., it's algorithm in RFC 1034, section 4.3.2. is not intended to be pseudo
steps are not intended to be followed in strict order. The "algorithm" code, i.e., it's steps are not intended to be followed in strict
is a suggestion. As such, in step 3, parts a, b, and c, do not have to order. The "algorithm" is a suggestion. As such, in step 3, parts
be implemented in that order. 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. Another issue needing explanation is that RFC 1034 is a full
There is another RFC, RFC 2672, which makes, or proposes an adjustment standard. There is another RFC, RFC 2672, which makes, or proposes
to RFC 1034's section 4.3.2 for the sake of the DNAME RR. RFC 2672 is an adjustment to RFC 1034's section 4.3.2 for the sake of the DNAME
a proposed standard. The dilemma in writing these clarifications is RR. RFC 2672 is a proposed standard. The dilemma in writing these
knowing which document is the one being clarified. Fortunately, the clarifications is knowing which document is the one being clarified.
difference between RFC 1034 and RFC 2672 is not significant with respect Fortunately, the difference between RFC 1034 and RFC 2672 is not
to wild card synthesis, so this document will continue to state that significant with respect to wild card synthesis, so this document
it is clarifying RFC 1034. If RFC 2672 progresses along the standards will continue to state that it is clarifying RFC 1034. If RFC 2672
track, it will need to refer to modifying RFC 1034's algorithm as progresses along the standards track, it will need to refer to
amended here. modifying RFC 1034's algorithm as amended here.
The context of part 'c' is that the search is progressing label by label The context of part 'c' is that the search is progressing label by
through the QNAME. (Note that the data being searched is the authoritative label through the QNAME. (Note that the data being searched is the
data in the server, the cache is searched in step 4.) Step 3's part 'a' authoritative data in the server, the cache is searched in step 4.)
covers the case that the QNAME has been matched in full, regardless of the Step 3's part 'a' covers the case that the QNAME has been matched in
presence of a CNAME RR. Step 'b' covers crossing a cut point, resulting full, regardless of the presence of a CNAME RR. Step 'b' covers
in a referral. All that is left is to look for the wild card. crossing a cut point, resulting in a referral. All that is left is
to look for the wild card.
Step 3 of the algorithm also assumes that the search is looking in the Step 3 of the algorithm also assumes that the search is looking in
zone closest to the answer, i.e., in the same class as QCLASS and as the zone closest to the answer, i.e., in the same class as QCLASS and
close to the authority as possible on this server. If the zone is not as close to the authority as possible on this server. If the zone is
the authority, then a referral is given, possibly one indicating lameness. not the authority, then a referral is given, possibly one indicating
lameness.
# c. If at some label, a match is impossible (i.e., the # c. If at some label, a match is impossible (i.e., the
# corresponding label does not exist), look to see if a # corresponding label does not exist), look to see if a
# the "*" label exists. # the "*" label exists.
The above paragraph refers to finding the domain name that exists in the The above paragraph refers to finding the domain name that exists in
zone and that most encloses the QNAME. Such a domain name will mark the the zone and that most encloses the QNAME. Such a domain name will
boundary of candidate wild card domain names that might be used to mark the boundary of candidate wild card domain names that might be
synthesize an answer. (Remember that at this point, if the most enclosing used to synthesize an answer. (Remember that at this point, if the
name is the same as the QNAME, part 'a' would have recorded an exact most enclosing name is the same as the QNAME, part 'a' would have
match.) The existence of the enclosing name means that no wild card name recorded an exact match.) The existence of the enclosing name means
higher in the tree is a candidate to answer the query. that no wild card name higher in the tree is a candidate to answer
the query.
Once the closest enclosing node is identified, there's the matter of what Once the closest enclosing node is identified, there's the matter of
exists below it. It may have subdomains, but none will be closer to the what exists below it. It may have subdomains, but none will be
QNAME. One of the subdomains just might be a wild card. If it exists, closer to the QNAME. One of the subdomains just might be a wild
this is the only wild card eligible to be used to synthesize an answer card. If it exists, this is the only wild card eligible to be used
for the query. Even if the closest enclosing node conforms to the syntax to synthesize an answer for the query. Even if the closest enclosing
rule in section 2 for being a wild card domain name, the closest enclosing node conforms to the syntax rule in section 2 for being a wild card
node is not eligible to be a source of a synthesized answer. domain name, the closest enclosing node is not eligible to be a
source of a synthesized answer.
The only wild card domain name that is a candidate to synthesize an answer The only wild card domain name that is a candidate to synthesize an
will be the "*" subdomain of the closest enclosing domain name. Three answer will be the "*" subdomain of the closest enclosing domain
possibilities can happen. The "*" subdomain does not exist, the "*" name. Three possibilities can happen. The "*" subdomain does not
subdomain does but does not have an RR set of the same type as the QTYPE, exist, the "*" subdomain does but does not have an RR set of the same
or it exists and has the desired RR set. type as the QTYPE, or it exists and has the desired RR set.
For the sake of brevity, the closest enclosing node can be referred to as For the sake of brevity, the closest enclosing node can be referred
the "closest encloser." The closest encloser is the most important concept to as the "closest encloser." The closest encloser is the most
in this clarification. Describing the closest encloser is a bit tricky, important concept in this clarification. Describing the closest
but it is an easy concept. encloser is a bit tricky, but it is an easy concept.
To find the closest encloser, you have to first locate the zone that is To find the closest encloser, you have to first locate the zone that
the authority for the query name. This eliminates the need to be concerned is the authority for the query name. This eliminates the need to be
that the closest encloser is a cut point. In addition, we can assume too concerned that the closest encloser is a cut point. In addition, we
that the query name does not exist, hence the closest encloser is not equal can assume too that the query name does not exist, hence the closest
to the query name. We can assume away these two cases because they are encloser is not equal to the query name. We can assume away these
handled in steps 2, 3a and 3b of section 4.3.2.'s algorithm. two cases because they are handled in steps 2, 3a and 3b of section
4.3.2.'s algorithm.
What is left is to identify the existing domain name that would have been What is left is to identify the existing domain name that would have
up the tree (closer to the root) from the query name. Knowing that an been up the tree (closer to the root) from the query name. Knowing
exact match is impossible, if there is a "*" label descending from the that an exact match is impossible, if there is a "*" label descending
unique closest encloser, this is the one and only wild card from which from the unique closest encloser, this is the one and only wild card
an answer can be synthesized for the query. from which an answer can be synthesized for the query.
To illustrate, using the example in section 1.2 of this document, the To illustrate, using the example in section 1.2 of this document, the
following chart shows QNAMEs and the closest enclosers. In Appendix A following chart shows QNAMEs and the closest enclosers. In
there is another chart showing unusual cases. Appendix A there is another chart showing unusual cases.
QNAME Closest Encloser Wild Card Source QNAME Closest Encloser Wild Card Source
host3.example. example. *.example. host3.example. example. *.example.
_telnet._tcp.host1.example. _tcp.host1.example. no wild card _telnet._tcp.host1.example. _tcp.host1.example. no wild card
_telnet._tcp.host2.example. host2.example. no wild card _telnet._tcp.host2.example. host2.example. no wild card
_telnet._tcp.host3.example. example. *.example. _telnet._tcp.host3.example. example. *.example.
_chat._udp.host3.example. example. *.example. _chat._udp.host3.example. example. *.example.
Note that host1.subdel.example. is in a subzone, so the search for it ends Note that host1.subdel.example. is in a subzone, so the search for it
in a referral in part 'b', thus does not enter into finding a closest ends in a referral in part 'b', thus does not enter into finding a
encloser. closest encloser.
The fact that a closest encloser will be the only superdomain that The fact that a closest encloser will be the only superdomain that
can have a candidate wild card will have an impact when it comes to can have a candidate wild card will have an impact when it comes to
designing authenticated denial of existence proofs. designing authenticated denial of existence proofs.
# If the "*" label does not exist, check whether the name # If the "*" label does not exist, check whether the name
# we are looking for is the original QNAME in the query # we are looking for is the original QNAME in the query
# or a name we have followed due to a CNAME. If the name # or a name we have followed due to a CNAME. If the name
# is original, set an authoritative name error in the # is original, set an authoritative name error in the
# response and exit. Otherwise just exit. # response and exit. Otherwise just exit.
The above passage says that if there is not even a wild card domain name The above passage says that if there is not even a wild card domain
to match at this point (failing to find an explicit answer elsewhere), name to match at this point (failing to find an explicit answer
we are to return an authoritative name error at this point. If we were elsewhere), we are to return an authoritative name error at this
following a CNAME, the specification is unclear, but seems to imply that point. If we were following a CNAME, the specification is unclear,
a no error return code is appropriate, with just the CNAME RR (or sequence but seems to imply that a no error return code is appropriate, with
of CNAME RRs) in the answer section. just the CNAME RR (or sequence of CNAME RRs) in the answer section.
# If the "*" label does exist, match RRs at that node # If the "*" label does exist, match RRs at that node
# against QTYPE. If any match, copy them into the answer # against QTYPE. If any match, copy them into the answer
# section, but set the owner of the RR to be QNAME, and # section, but set the owner of the RR to be QNAME, and
# not the node with the "*" label. Go to step 6. # not the node with the "*" label. Go to step 6.
This final paragraph covers the role of the QTYPE in the process. Note This final paragraph covers the role of the QTYPE in the process.
that if no resource record set matches the QTYPE the result is that no data Note that if no resource record set matches the QTYPE the result is
is copied, but the search still ceases ("Go to step 6."). In the following that no data is copied, but the search still ceases ("Go to step
section, a suggested change is made to this, under the heading "CNAME RRs 6."). In the following section, a suggested change is made to this,
at a Wild Card Domain Name." under the heading "CNAME RRs at a Wild Card Domain Name."
6 Considerations with Special Types
For the purposes of this section, "special" means that a record induces 6. Considerations with Special Types
processing at the server beyond simple lookup. The special types in this
section are SOA, NS, CNAME, and DNAME. SOA is special because it is used
as a zone marker and has an impact on step 2 of the algorithm in 4.3.2.
NS denotes a cut point and has an impact on step 3b. CNAME redirects the
query and is mentioned in steps 3a and 3b. DNAME is a "CNAME generator."
6.1 SOA RR's at a Wild Card Domain Name For the purposes of this section, "special" means that a record
induces processing at the server beyond simple lookup. The special
types in this section are SOA, NS, CNAME, and DNAME. SOA is special
because it is used as a zone marker and has an impact on step 2 of
the algorithm in 4.3.2. NS denotes a cut point and has an impact on
step 3b. CNAME redirects the query and is mentioned in steps 3a and
3b. DNAME is a "CNAME generator."
If the owner of an SOA record conforms to the basic rules of owning an 6.1. SOA RR's at a Wild Card Domain Name
SOA RR (meaning it is the apex of a zone) the impact on the search algorithm
is not in section 3c (where records are synthesized) as would be expected.
The impact is really in step 2 of the algorithm, the choice of zone.
We are no longer talking about whether or not an SOA RR can be synthesized If the owner of an SOA record conforms to the basic rules of owning
in a response because we are shifting attention to step 2. We are now talking an SOA RR (meaning it is the apex of a zone) the impact on the search
about what it means for a name server to synthesize a zone for a response. algorithm is not in section 3c (where records are synthesized) as
To date, no implementation has done this. Thinking ahead though, anyone would be expected. The impact is really in step 2 of the algorithm,
choosing to pursue this would have to be aware that a server would have to the choice of zone.
be able to distinguish between queries for data it will have to synthesize and
queries that ought to be treated as if they were prompted by a lame delegation.
It is not a protocol error to have an SOA RR owned by a wild card domain name, We are no longer talking about whether or not an SOA RR can be
just as it is not an error to have zone name be syntactically equivalent to a synthesized in a response because we are shifting attention to step
domain name. However, this situation requires careful consideration of how 2. We are now talking about what it means for a name server to
a server chooses the appropriate zone for an answer. And an SOA RR is synthesize a zone for a response. To date, no implementation has
not able to be synthesized as in step 3c. done this. Thinking ahead though, anyone choosing to pursue this
would have to be aware that a server would have to be able to
distinguish between queries for data it will have to synthesize and
queries that ought to be treated as if they were prompted by a lame
delegation.
6.2 NS RR's at a Wild Card Domain Name It is not a protocol error to have an SOA RR owned by a wild card
domain name, just as it is not an error to have zone name be
syntactically equivalent to a domain name. However, this situation
requires careful consideration of how a server chooses the
appropriate zone for an answer. And an SOA RR is not able to be
synthesized as in step 3c.
Complimentary to the issue of an SOA RR owned by a wild card domain name is 6.2. NS RR's at a Wild Card Domain Name
the issue of NS RR's owned by a wild card domain name. In this instance,
each machine being referred to in the RDATA of the NS RR has to be able to
understand the impact of this on step 2, the choosing of the authoritative
zone.
Referring to the same machine in such a NS RR will probably not work well. Complimentary to the issue of an SOA RR owned by a wild card domain
This is because the server may become confused as to whether the query name name is the issue of NS RR's owned by a wild card domain name. In
ought to be answered by the zone owning the NS RR in question or a synthesized this instance, each machine being referred to in the RDATA of the NS
zone. (It isn't known in advance that the query name will invoke the wild RR has to be able to understand the impact of this on step 2, the
card synthesis.) choosing of the authoritative zone.
The status of other RR's owned by a wild card domain name is the same as Referring to the same machine in such a NS RR will probably not work
if the owner name was not a wild card domain name. I.e., when there is a well. This is because the server may become confused as to whether
NS RR at a wild card domain name, other records are treated as being below the query name ought to be answered by the zone owning the NS RR in
the zone cut. question or a synthesized zone. (It isn't known in advance that the
query name will invoke the wild card synthesis.)
The status of other RR's owned by a wild card domain name is the same
as if the owner name was not a wild card domain name. I.e., when
there is a NS RR at a wild card domain name, other records are
treated as being below the zone cut.
Is it not a protocol error to have a NS RR owned by a wild card domian name, Is it not a protocol error to have a NS RR owned by a wild card
complimentary to the case of a SOA RR. However, for this to work, an domian name, complimentary to the case of a SOA RR. However, for
implementation has to know how to synthesize a zone. this to work, an implementation has to know how to synthesize a zone.
6.3 CNAME RR's at a Wild Card Domain Name 6.3. CNAME RR's at a Wild Card Domain Name
The issue of CNAME RR's owned by wild card domain names has prompted a The issue of CNAME RR's owned by wild card domain names has prompted
suggested change to the last paragraph of step 3c of the algorithm in 4.3.2. a suggested change to the last paragraph of step 3c of the algorithm
The changed text is this: in 4.3.2. The changed text is this:
If the "*" label does exist and if the data at the node is If the "*" label does exist and if the data at the node is a
a CNAME and QTYPE doesn't match CNAME, copy the CNAME RR CNAME and QTYPE doesn't match CNAME, copy the CNAME RR into the
into the answer section of the response, set the owner answer section of the response, set the owner of the CNAME RR to
of the CNAME RR to be QNAME, and then change QNAME to the be QNAME, and then change QNAME to the canonical name in the
canonical name in the CNAME RR, and go back to step 1. CNAME RR, and go back to step 1.
If the "*" label does exist and either QTYPE is CNAME or the If the "*" label does exist and either QTYPE is CNAME or the
data at the node is not a CNAME, then match RRs at that node data at the node is not a CNAME, then match RRs at that node
against QTYPE. If any match, copy them into the answer against QTYPE. If any match, copy them into the answer section,
section, but set the owner of the RR to be QNAME, and but set the owner of the RR to be QNAME, and not the node with
not the node with the "*" label. Go to step 6. the "*" label. Go to step 6.
Apologies if the above isn't clear, but an attempt was made to stitch Apologies if the above isn't clear, but an attempt was made to stitch
together the passage using just the phrases in section 3a and 3c of the together the passage using just the phrases in section 3a and 3c of
algorithm so as to preserve the original flavor. the algorithm so as to preserve the original flavor.
In case the passage as suggested isn't clear enough, the intent is to make In case the passage as suggested isn't clear enough, the intent is to
"landing" at a wild card name and finding a CNAME the same as if this happened make "landing" at a wild card name and finding a CNAME the same as if
as a result of a direct match. I.e., Finding a CNAME at the name matched this happened as a result of a direct match. I.e., Finding a CNAME
in step 3c is supposed to have the same impact as finding the CNAME in step at the name matched in step 3c is supposed to have the same impact as
3a. finding the CNAME in step 3a.
6.4 DNAME RR's at a Wild Card Domain Name 6.4. DNAME RR's at a Wild Card Domain Name
The specification of the DNAME RR, which is at the proposed level of 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 standardization, is not as mature as the full standard in RFC 1034.
of this, or the reason for this is, there appears to be a host of issues Because of this, or the reason for this is, there appears to be a
with that definition and it's rewrite of the algorithm in 4.3.2. For the host of issues with that definition and it's rewrite of the algorithm
time being, when it comes to wild card processing issues, a DNAME can in 4.3.2. For the time being, when it comes to wild card processing
be considered to be a CNAME synthesizer. A DNAME at a wild card domain name issues, a DNAME can be considered to be a CNAME synthesizer. A DNAME
is effectively the same as a CNAME at a wild card domain name. at a wild card domain name is effectively the same as a CNAME at a
wild card domain name.
7 Security Considerations 7. Security Considerations
This document is refining the specifications to make it more likely that This document is refining the specifications to make it more likely
security can be added to DNS. No functional additions are being made, just that security can be added to DNS. No functional additions are being
refining what is considered proper to allow the DNS, security of the DNS, and made, just refining what is considered proper to allow the DNS,
extending the DNS to be more predictable. security of the DNS, and extending the DNS to be more predictable.
8 References 8. References
Normative References Normative References
[RFC 20] ASCII Format for Network Interchange, V.G. Cerf, Oct-16-1969 [RFC 20] ASCII Format for Network Interchange, V.G. Cerf, Oct-16-1969
[RFC 1034] Domain Names - Concepts and Facilities, P.V. Mockapetris, [RFC 1034] Domain Names - Concepts and Facilities, P.V. Mockapetris,
Nov-01-1987 Nov-01-1987
[RFC 1035] Domain Names - Implementation and Specification, P.V [RFC 1035] Domain Names - Implementation and Specification, P.V
Mockapetris, Nov-01-1987 Mockapetris, Nov-01-1987
[RFC 2119] Key Words for Use in RFCs to Indicate Requirement Levels, S [RFC 2119] Key Words for Use in RFCs to Indicate Requirement Levels, S
Bradner, March 1997 Bradner, March 1997
Informative References Informative References
[RFC 2136] Dynamic Updates in the Domain Name System (DNS UPDATE), P. Vixie, [RFC 2136] Dynamic Updates in the Domain Name System (DNS UPDATE), P. Vixie,
Ed., S. Thomson, Y. Rekhter, J. Bound, April 1997 Ed., S. Thomson, Y. Rekhter, J. Bound, April 1997
[RFC 2535] Domain Name System Security Extensions, D. Eastlake, March 1999 [RFC 2535] Domain Name System Security Extensions, D. Eastlake, March 1999
[RFC 2672] Non-Terminal DNS Name Redirection, M. Crawford, August 1999 [RFC 2672] Non-Terminal DNS Name Redirection, M. Crawford, August 1999
9 Others Contributing to This Document 9. Others Contributing to This Document
Others who have directly caused text to appear in the document: Paul Vixie Others who have directly caused text to appear in the document: Paul
and Olaf Kolkman. Many others have indirect influences on the content. Vixie and Olaf Kolkman. Many others have indirect influences on the
content.
10 Editors 10. Editors
Name: Bob Halley Name: Bob Halley
Affiliation: Nominum, Inc. Affiliation: Nominum, Inc.
Address: 2385 Bay Road, Redwood City, CA 94063 USA Address: 2385 Bay Road, Redwood City, CA 94063 USA
Phone: +1-650-381-6016 Phone: +1-650-381-6016
EMail: Bob.Halley@nominum.com EMail: Bob.Halley@nominum.com
Name: Edward Lewis Name: Edward Lewis
Affiliation: ARIN Affiliation: ARIN
Address: 3635 Concorde Pkwy, Suite 200, Chantilly, VA 20151 USA Address: 3635 Concorde Pkwy, Suite 200, Chantilly, VA 20151 USA
Phone: +1-703-227-9854 Phone: +1-703-227-9854
Email: edlewis@arin.net Email: edlewis@arin.net
Comments on this document can be sent to the editors or the mailing
list for the DNSEXT WG, namedroppers@ops.ietf.org.
Appendix A: Subdomains of Wild Card Domain Names Appendix A: Subdomains of Wild Card Domain Names
In reading the definition of section 2 carefully, it is possible to In reading the definition of section 2 carefully, it is possible to
rationalize unusual names as legal. In the example given, *.example. rationalize unusual names as legal. In the example given,
could have subdomains of *.sub.*.example. and even the more direct *.example. could have subdomains of *.sub.*.example. and even the
*.*.example. (The implication here is that these domain names own more direct *.*.example. (The implication here is that these domain
explicit resource records sets.) Although defining these names is not names own explicit resource records sets.) Although defining these
easy to justify, it is important that implementions account for the names is not easy to justify, it is important that implementions
possibility. This section will give some further guidence on handling account for the possibility. This section will give some further
these names. guidence on handling these names.
The first thing to realize is that by all definitions, subdomains of The first thing to realize is that by all definitions, subdomains of
wild card domain names are legal. In analyzing them, one realizes wild card domain names are legal. In analyzing them, one realizes
that they cause no harm by their existence. Because of this, they are that they cause no harm by their existence. Because of this, they
allowed to exist, i.e., there are no special case rules made to disallow are allowed to exist, i.e., there are no special case rules made to
them. The reason for not preventing these names is that the prevention disallow them. The reason for not preventing these names is that the
would just introduce more code paths to put into implementations. prevention would just introduce more code paths to put into
implementations.
The concept of "closest enclosing" existing names is important to keep in The concept of "closest enclosing" existing names is important to
mind. It is also important to realize that a wild card domain name can keep in mind. It is also important to realize that a wild card
be a closest encloser of a query name. For example, if *.*.example. is domain name can be a closest encloser of a query name. For example,
defined in a zone, and the query name is a.*.example., then the closest if *.*.example. is defined in a zone, and the query name is
enclosing domain name is *.example. Keep in mind that the closest a.*.example., then the closest enclosing domain name is *.example.
encloser is not eligible to be a source of synthesized answers, just the Keep in mind that the closest encloser is not eligible to be a source
subdomain of it that has the first label "*". of synthesized answers, just the subdomain of it that has the first
label "*".
To illustrate this, the following chart shows some matches. Assume that To illustrate this, the following chart shows some matches. Assume
the names *.example., *.*.example., and *.sub.*.example. are defined that the names *.example., *.*.example., and *.sub.*.example. are
in the zone. defined in the zone.
QNAME Closest Encloser Wild Card Source QNAME Closest Encloser Wild Card Source
a.example. example. *.example. a.example. example. *.example.
b.a.example. example. *.example. b.a.example. example. *.example.
a.*.example. *.example. *.*.example. a.*.example. *.example. *.*.example.
b.a.*.example. *.example. *.*.example. b.a.*.example. *.example. *.*.example.
b.a.*.*.example. *.*.example. no wild card b.a.*.*.example. *.*.example. no wild card
a.sub.*.example. sub.*.example. *.sub.*.example. a.sub.*.example. sub.*.example. *.sub.*.example.
b.a.sub.*.example. sub.*.example. *.sub.*.example. b.a.sub.*.example. sub.*.example. *.sub.*.example.
a.*.sub.*.example. *.sub.*.example. no wild card a.*.sub.*.example. *.sub.*.example. no wild card
*.a.example. example. *.example. *.a.example. example. *.example.
a.sub.b.example. example. *.example. a.sub.b.example. example. *.example.
Recall that the closest encloser itself cannot be the wild card. Therefore Recall that the closest encloser itself cannot be the wild card.
the match for b.a.*.*.example. has no applicable wild card. Therefore the match for b.a.*.*.example. has no applicable wild card.
Finally, if a query name is sub.*.example., any answer available will come Finally, if a query name is sub.*.example., any answer available will
from an exact name match for sub.*.example. No wild card synthesis is come from an exact name match for sub.*.example. No wild card
performed in this case. synthesis is performed in this case.
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society 2003. All Rights Reserved. Copyright (C) The Internet Society 2003. All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published and or assist in its implementation may be prepared, copied, published
distributed, in whole or in part, without restriction of any kind, and distributed, in whole or in part, without restriction of any
provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
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The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
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This document and the information contained herein is provided on an This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
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Acknowledgement Acknowledgement
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
 End of changes. 

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