draft-josefsson-dns-url-09.txt   draft-josefsson-dns-url-10.txt 
Network Working Group S. Josefsson Network Working Group S. Josefsson
Expires: April 25, 2004 Expires: March 3, 2005
Domain Name System Uniform Resource Identifiers Domain Name System Uniform Resource Identifiers
draft-josefsson-dns-url-09 draft-josefsson-dns-url-10
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2004).
Abstract Abstract
This document define Uniform Resource Identifiers for Domain Name This document define Uniform Resource Identifiers for Domain Name
System resources. System resources.
Table of Contents Table of Contents
1. Introduction and Background . . . . . . . . . . . . . . . . . 3 1. Introduction and Background . . . . . . . . . . . . . . . . . 3
2. DNS URI Registration . . . . . . . . . . . . . . . . . . . . . 4 2. DNS URI Registration . . . . . . . . . . . . . . . . . . . . . 4
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
Normative References . . . . . . . . . . . . . . . . . . . . . 9 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Informative References . . . . . . . . . . . . . . . . . . . . 9 6.1 Normative References . . . . . . . . . . . . . . . . . . . . 9
6.2 Informative References . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 10 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 10
A. Revision Changes . . . . . . . . . . . . . . . . . . . . . . . 10 A. Revision Changes . . . . . . . . . . . . . . . . . . . . . . . 10
A.1 Changes since -06 . . . . . . . . . . . . . . . . . . . . . . 10 A.1 Changes since -06 . . . . . . . . . . . . . . . . . . . . 10
A.2 Changes since -07 . . . . . . . . . . . . . . . . . . . . . . 10 A.2 Changes since -07 . . . . . . . . . . . . . . . . . . . . 10
A.3 Changes since -08 . . . . . . . . . . . . . . . . . . . . . . 10 A.3 Changes since -08 . . . . . . . . . . . . . . . . . . . . 11
A.4 Changes since -09 . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . 12 Intellectual Property and Copyright Statements . . . . . . . . 12
1. Introduction and Background 1. Introduction and Background
The Domain Name System (DNS) [1][2] is a widely deployed system used The Domain Name System (DNS) [1][2] is a widely deployed system used
to, among other things, translate host names into IP addresses. to, among other things, translate host names into IP addresses.
Recent work has added support for storing certificates and Recent work has added support for storing certificates and
certificate revocation lists in the DNS [10]. certificate revocation lists (CRLs) in the DNS [9]. Several
protocols use Uniform Resource Locators (URLs) to point at
The primary motivation behind defining a Uniform Resource Identifier certificates and CRLs. By defining a Uniform Resource Identifier
(URI) for DNS resources, instead of using another non-URI syntax that (URI) scheme for DNS resources, such protocols can reference
embed the domain, type value and class value, is that applications certificates and CRLs stored in the DNS.
that stores or retrieve certificates today uses URIs for this
purpose. Thus, defining a URI scheme for DNS resources allows these
existing protocols to be used with certificates in the DNS without
having to add DNS specific modifications to said protocols. In order
to not introduce interoperability or security considerations,
protocols that uses these URIs naturally must have been written to
allow for future, as of writing yet undefined, URIs to be used.
A few examples of protocols that may utilize DNS URIs: A few examples of protocols that may utilize DNS URIs:
o The OpenPGP Message Format [8], where an end-user may indicate the o The OpenPGP Message Format [7], where an end-user may indicate the
location of a copy of any updates to her key, using the "preferred location of a copy of any updates to her key, using the "preferred
key server" field. key server" field.
o The X.509 Online Certificate Status Protocol [11], where the OCSP o The X.509 Online Certificate Status Protocol [10], where the OCSP
responder can indicate where a CRL is found, using the responder can indicate where a CRL is found, using the
id-pkix-ocsp-crl extension. id-pkix-ocsp-crl extension.
The DNS URI scheme defined here can, of course, be used to reference The DNS URI scheme defined here can be used to reference any data
any DNS data, and is not limited to only certificates. The purpose stored in the DNS, and is not limited to certificates or CRLs. The
of this specification is to define a generic DNS URI, not a specific purpose of this specification is to define a generic DNS URI, not to
DNS solution for certificates stored in the DNS. Browsers may specify a solution only for certificates stored in the DNS.
implement support for DNS URIs by forming DNS queries and render DNS
responses using HTML [14], similar to what is done for the FTP [5].
The core part of this document is the URI Registration Template Data browsers may support DNS URIs by forming DNS queries and render
according to [13]. DNS responses using HTML [13], similar to what is commonly done for
FTP [5] resources.
The core part of this document is the URI Registration Template in
accordance with [12].
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 RFC 2119 [6]. document are to be interpreted as described in RFC 2119 [6].
2. DNS URI Registration 2. DNS URI Registration
URL scheme name: "dns". URL scheme name: "dns".
URL scheme syntax: A DNS URI designates a DNS resource record set URL scheme syntax: A DNS URI designate a DNS resource record set,
that can be referenced by domain name, type, class and optionally the referenced by domain name, class, type and optionally the authority.
authority. The DNS URI follows the generic syntax from RFC 2396 [4], The DNS URI follows the generic syntax from RFC 2396 [4], and is
and is described using ABNF [3]. Strings are not case sensitive and described using ABNF [3]. Strings are not case sensitive and free
free insertion of linear-white-space is not permitted. insertion of linear-white-space is not permitted.
dnsurl = "dns:" [ "//" dnsauthority "/" ] dnsname ["?" dnsquery] dnsurl = "dns:" [ "//" dnsauthority "/" ] dnsname ["?" dnsquery]
dnsauthority = hostport dnsauthority = hostport
; See RFC 2396 for "hostport" definition. ; See RFC 2396 for "hostport" definition.
dnsname = *pchar dnsname = *pchar
; See RFC 2396 for "pchar" definition. ; See RFC 2396 for "pchar" definition.
; NB! Can be empty.
; The "dnsname" field may be a "relative"
; or "absolute" name, as per RFC 1034
; section 3.1.
; Note further that an empty "dnsname"
; value is to be interpreted as the
; root itself. See below on relative
; dnsname's.
dnsquery = dnsqueryelement [";" dnsquery] dnsquery = dnsqueryelement [";" dnsquery]
; First matching element MUST be used.
; E.g., dns:host.example.org?TYPE=A;TYPE=TXT
; means type A.
dnsqueryelement = ( "CLASS=" dnsclassval ) / ( "TYPE=" dnstypeval ) / dnsqueryelement = ( "CLASS=" dnsclassval ) / ( "TYPE=" dnstypeval )
( 1*alphanum "=" 1*alphanum ) ; Each clause MUST NOT be used more than
; once.
dnsclassval = 1*digit / "IN" / "CH" / ... dnsclassval = 1*digit / "IN" / "CH" / ...
; Any IANA registered DNS class expressed as ; Any IANA registered DNS class expressed
; mnemonic or as decimal integer. ; as mnemonic or as decimal integer.
dnstypeval = 1*digit / "A" / "NS" / "MD" / ... dnstypeval = 1*digit / "A" / "NS" / "MD" / ...
; Any IANA registered DNS type expressed as ; Any IANA registered DNS type expressed
; mnemonic or as decimal integer. ; as mnemonic or as decimal integer.
Unless specified in the URI, the authority ("dnsauthority") is
assumed to be locally known, the class ("dnsclassval") to be the
Internet class ("IN"), and the type ("dnstypeval") to be the Address
type ("A"). These default values match the typical use of DNS; to
look up addresses for host names.
A dnsquery element MUST NOT contain more than one occurance of the
"CLASS" and "TYPE" fields. For example, both
"dns:example?TYPE=A;TYPE=TXT" and "dns:example?TYPE=A;TYPE=A" are
invalid. However, the fields may occur in any order, so that both
"dns:example?TYPE=A;CLASS=IN" and "dns:example?CLASS=IN;TYPE=A" are
valid.
The digit representation of types and classes MAY be used when a The digit representation of types and classes MAY be used when a
mnemonic for the corresponding value is not well known (e.g., for mnemonic for the corresponding value is not well known (e.g., for
newly introduced types or classes), but SHOULD NOT be used for the newly introduced types or classes), but SHOULD NOT be used for the
types or classes defined in the DNS specification [2]. All types or classes defined in the DNS specification [2]. All
implementations MUST recognize the mnemonics defined in [2]. implementations MUST recognize the mnemonics defined in [2].
Unless specified in the URI, the authority ("dnsauthority") is To avoid ambiguity, relative "dnsname" values (i.e., those not ending
assumed to be locally known, "dnsclassval" to be the Internet class with ".") are assumed to be relative to the root. For example,
("IN"), and "dnstypeval" to be the Address type ("A"). "dns:host.example" and "dns:host.example." both refer to the same
owner name, namely "host.example.". Further, an empty "dnsname"
value is considered to be a degenerative form of a relative name,
which refer to the root (".").
To resolve a DNS URI using the DNS protocol [2] a query is formed by To resolve a DNS URI using the DNS protocol [2] a query is created,
using the dnsname, dnsclassval and dnstypeval from the URI string (or using as input the dnsname, dnsclassval and dnstypeval from the URI
the previously mentioned default values if some value missing from string (or the appropriate default values). If an authority
the string). If authority ("dnsauthority") is given in the URI ("dnsauthority") is given in the URI string, this indicate the server
string, this indicate the server that should receive the DNS query, that should receive the DNS query, otherwise the default DNS server
otherwise the default DNS server should receive it. (Note that DNS should receive it.
URIs could be resolved by other protocols than the DNS protocol. DNS
URIs does not require the use of the DNS protocol, although it is Note that DNS URIs could be resolved by other protocols than the DNS
expected to be the typical usage. This paragraph only illustrate how protocol, or by using the DNS protocol in some other way than as
DNS URIs are resolved using the DNS protocol.) described above (e.g., multicast DNS). DNS URIs do not require the
use of the DNS protocol, although it is expected to be the typical
usage. The previous paragraph only illustrate how DNS URIs are
resolved using the DNS protocol.
A client MAY want to check that it understands the dnsclassval and A client MAY want to check that it understands the dnsclassval and
dnstypeval before sending a query, so that it is able to correctly dnstypeval before sending a query, so that it will be able to
parse the answer. A typical example of a client that would not need understand the response. However, a typical example of a client that
to check dnsclassval and dnstypeval would be a proxy that just treat would not need to check dnsclassval and dnstypeval would be a proxy,
the answer as opaque data. that would just treat the received answer as opaque data.
Character encoding considerations: The characters are encoded as per Character encoding considerations: The characters are encoded as per
the "URI Generic Syntax" RFC [4]. The DNS protocol do not consider the "URI Generic Syntax" RFC [4]. The DNS protocol do not consider
character sets, it simply transports opaque data. In particular, the character sets, it simply transports opaque data. In particular, the
"dnsname" field of the DNS URI is to be considered an "dnsname" field of the DNS URI is to be considered an
internationalized domain name (IDN) unaware domain name slot, in the internationalized domain name (IDN) unaware domain name slot, in the
terminology of [16]. (The reason for this is that making these fields terminology of [15]. The considerations for "hostport" are discussed
be IDN aware by, e.g., specifying that they are UTF-8 [7] strings, in [4]
would require further encoding mechanisms to be able to express all
valid DNS domain names. This is because the DNS allows all octet
sequences to be used as domain labels, so UTF-8 strings do not cover
all possibilities. Instead of defining further encoding mechanisms,
we point applications with internationalization needs at the ASCII
encoding described in [16] which should be satisfactory.) The
considerations for "hostport" are discussed in [4]
To encode a "." that is part of a DNS label the "escaped" encoding Because "." is used as the DNS label separator, an escaping mechanism
MUST be used, and a label delimiter MUST be encoded as ".". That is, is required to encode a "." that is part of a DNS label. The
the only way to encode a label delimiter is ".", and the only way to escaping mechanism is described in section 5.1 of RFC 1035. For
encode a "." as part of label is "%2e". This approach was chosen to example, a DNS label of "exa.mple" can be escaped as "exa\.mple" or
minimize the modifications users will have to do when manually "exa\046mple". However, the URI specification disallow the "\"
translating a domain name string into the URI form. character from occuring directly in URIs, so it must be escaped as
"%5c". The single DNS label "exa.mple" is thus encoded as
"exa%5c.mple". The same mechanism can be used to encode other
characters, for example "?" and ";". Note that "." and "%2e" are
equivalent within dnsname, and are interchangable.
This URI specification allows all possible domain names to be encoded This URI specification allows all possible domain names to be encoded
(of course following the encoding rules of [4]), however certain (of course following the encoding rules of [4]), however certain
applications may restrict the set of valid characters and care should applications may restrict the set of valid characters and care should
be taken so that invalid characters in these contexts does not cause be taken so that invalid characters in these contexts does not cause
harm. In particular, host names in the DNS have certain harm. In particular, host names in the DNS have certain
restrictions. It is up to these application to limit this subset, restrictions. It is up to these application to limit this subset,
this URI scheme places no restrictions. this URI scheme places no restrictions.
Intended usage: Whenever DNS resources are useful to reference by Intended usage: Whenever DNS resources are useful to reference by
protocol independent identifiers, often when the data is more protocol independent identifiers, often when the data is more
important than the access method. Since software in general has important than the access method. Since software in general has
coped without this so far, it is not anticipated to be implemented coped without this so far, it is not anticipated to be implemented
widely, nor migrated to by existing systems, but specific solutions widely, nor migrated to by existing systems, but specific solutions
(especially security related) may find this appropriate. (especially security related) may find this appropriate.
Applications and/or protocols which use this scheme: Security related Applications and/or protocols which use this scheme: Security related
software. It may be of interest to auxilliary DNS related software software. DNS administration tools. Network programming packages.
too.
Interoperability considerations: The data referenced by this URI Interoperability considerations: The data referenced by this URI
scheme might be transferred by protocols that are not URI aware (such scheme might be transferred by protocols that are not URI aware (such
as the DNS protocol). This is not anticipated to have any serious as the DNS protocol). This is not anticipated to have any serious
interoperability impact though. interoperability impact though.
Interoperability problems may occur if one entity understands a new Interoperability problems may occur if one entity understands a new
DNS type or class mnemonic but another entity do not understand it. DNS class/type mnemonic and another entity do not understand it.
This is an interoperability problem for DNS software in general, This is an interoperability problem for DNS software in general,
although it is not a major practical problem as the DNS types and although it is not a major practical problem as the DNS types and
classes are fairly static. To guarantee interoperability classes are fairly static. To guarantee interoperability
implementations could use integers for all mnemonics not defined in implementations can use integers for all mnemonics not defined in
[2]. [2].
Interaction with Binary Labels [12], or other extended label types, Interaction with Binary Labels [11], or other extended label types,
has not been analyzed. However, they appear to be infrequently used has not been analyzed. However, they appear to be infrequently used
in practice. in practice.
Security considerations: See below.
Contact: simon@josefsson.org Contact: simon@josefsson.org
Author/Change Controller: simon@josefsson.org Author/Change Controller: simon@josefsson.org
3. Examples 3. Examples
A DNS URI is of the following general form. This is intended to A DNS URI is of the following general form. This is intended to
illustrate, not define, the scheme. illustrate, not define, the scheme.
dns:[//authority/]domain[?type=TYPE;class=CLASS] dns:[//authority/]domain[?CLASS=class;TYPE=type]
The following illustrate a URI for a resource with the name The following illustrate a URI for a resource with the absolute name
"www.example.org", the Internet (IN) class and the Address (A) type: "www.example.org.", the Internet (IN) class and the Address (A) type:
dns:www.example.org?class=IN;type=A dns:www.example.org.?clAsS=IN;tYpE=A
Since the default class is IN, and the default type is A, the same Since the default class is IN, and the default type is A, the same
resource can be identified by a shorter URI: resource can be identified by a shorter URI, using a relative name:
dns:www.example.org dns:www.example.org
The following illustrate a URI for a resource with the name The following illustrate a URI for a resource with the name
"simon.example.org", for the CERT type, in the Internet (IN) class: "simon.example.org", for the CERT type, in the Internet (IN) class:
dns:simon.example.org?type=CERT dns:simon.example.org?type=CERT
The following illustrate a URI for a resource with the name The following illustrate a URI for a resource with the name
"ftp.example.org", in the Internet (IN) class and the address (A) "ftp.example.org", in the Internet (IN) class and the address (A)
type, but from the DNS authority 192.168.1.1 instead of the default type, but from the DNS authority 192.168.1.1 instead of the default
authority (i.e., when DNS is used, the query is sent to that server): authority:
dns://192.168.1.1/ftp.example.org?type=A dns://192.168.1.1/ftp.example.org?type=A
The following illustrate a strange, albeit valid, DNS resource. Note The following illustrate various escaping techniques. The owner name
the encoding of "." and 0x00, and the use of a named dnsauthority: would be "world wide web.example\.domain.org" where "\." denote the
character "." as part of a label, and "." denote the label separator:
dns://internal-dns.example.org/*.%3f%20%00%2e%25+?type=TXT dns:world%20wide%20web.example%5c.domain.example?TYPE=TXT
The following illustrate a strange, but valid, DNS resource:
dns://fw.example.org/*.%20%00.example?type=TXT
4. Security Considerations 4. Security Considerations
If a DNS URI references domains in the Internet DNS environment, both If a DNS URI references domains in the Internet DNS environment, both
the URI itself and the information referenced by the URI is public the URI itself and the information referenced by the URI is public
information. If a DNS URI is used within an "internal" DNS information. If a DNS URI is used within an "internal" DNS
environment, both the DNS URI and the data is referenced should be environment, both the DNS URI and the data is referenced should be
handled using the same considerations that apply to DNS data in the handled using the same considerations that apply to DNS data in the
environment. environment.
If information referenced by DNS URIs are used to make security If information referenced by DNS URIs are used to make security
decisions (examples of such data include, but is not limited to, decisions (examples of such data include, but is not limited to,
certificates stored in the DNS), implementations may need to employ certificates stored in the DNS), implementations may need to employ
security techniques such as Secure DNS [9], or even CMS [15] or security techniques such as Secure DNS [8], or even CMS [14] or
OpenPGP [8], to protect the data during transport. How to implement OpenPGP [7], to protect the data during transport. How to implement
this will depend on the usage scenario, and it is not up to this URI this will depend on the usage scenario, and it is not up to this URI
scheme to define how the data referenced by DNS URIs should be scheme to define how the data referenced by DNS URIs should be
protected. protected.
If applications accept unknown dnsqueryelement values (e.g., accepts If applications accept unknown dnsqueryelement values (e.g., accepts
the URI "dns:www.example.org?secret=value" without knowing what the the URI "dns:www.example.org?secret=value" without knowing what the
"secret=value" dnsqueryelement means), a covert channel used to "secret=value" dnsqueryelement means), a covert channel used to
"leak" information may be enabled. The implications of covert "leak" information may be enabled. The implications of covert
channels should be understood by applications that accepts unknown channels should be understood by applications that accepts unknown
dnsqueryelement values. dnsqueryelement values.
This draft does not modify the security considerations related to the Slight variations, such as difference between upper and lower case in
DNS or URIs in general. the dnsname field, can be used as a covert channel to leak
information.
5. IANA Considerations 5. IANA Considerations
The IANA is asked to register the DNS URI scheme, using the template The IANA is asked to register the DNS URI scheme, using the template
in section 2, in accordance with RFC 2717 [13]. in section 2, in accordance with RFC 2717 [12].
Acknowledgments Acknowledgments
Thanks to Stuart Cheshire, Donald Eastlake, Pasi Eronen, Ted Hardie, Thanks to Stuart Cheshire, Donald Eastlake, Pasi Eronen, Ted Hardie,
Peter Koch, Andrew Main, Larry Masinter, Michael Mealling, Steve Peter Koch, Andrew Main, Larry Masinter, Michael Mealling, Steve
Mattson, and Paul Vixie for comments and suggestions. The author Mattson, and Paul Vixie for comments and suggestions. The author
acknowledges the RSA Laboratories for supporting the work that led to acknowledges the RSA Laboratories for supporting the work that led to
this document. this document.
Normative References 6. References
6.1 Normative References
[1] Mockapetris, P., "Domain names - concepts and facilities", STD [1] Mockapetris, P., "Domain names - concepts and facilities", STD
13, RFC 1034, November 1987. 13, RFC 1034, November 1987.
[2] Mockapetris, P., "Domain names - implementation and [2] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[3] Crocker, D. and P. Overell, "Augmented BNF for Syntax [3] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[4] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource [4] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998. Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
Informative References 6.2 Informative References
[5] Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9, [5] Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9,
RFC 959, October 1985. RFC 959, October 1985.
[6] Bradner, S., "Key words for use in RFCs to Indicate Requirement [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[7] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC [7] Callas, J., Donnerhacke, L., Finney, H. and R. Thayer, "OpenPGP
2279, January 1998.
[8] Callas, J., Donnerhacke, L., Finney, H. and R. Thayer, "OpenPGP
Message Format", RFC 2440, November 1998. Message Format", RFC 2440, November 1998.
[9] Eastlake, D., "Domain Name System Security Extensions", RFC [8] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999. 2535, March 1999.
[10] Eastlake, D. and O. Gudmundsson, "Storing Certificates in the [9] Eastlake, D. and O. Gudmundsson, "Storing Certificates in the
Domain Name System (DNS)", RFC 2538, March 1999. Domain Name System (DNS)", RFC 2538, March 1999.
[11] Myers, M., Ankney, R., Malpani, A., Galperin, S. and C. Adams, [10] Myers, M., Ankney, R., Malpani, A., Galperin, S. and C. Adams,
"X.509 Internet Public Key Infrastructure Online Certificate "X.509 Internet Public Key Infrastructure Online Certificate
Status Protocol - OCSP", RFC 2560, June 1999. Status Protocol - OCSP", RFC 2560, June 1999.
[12] Crawford, M., "Binary Labels in the Domain Name System", RFC [11] Crawford, M., "Binary Labels in the Domain Name System", RFC
2673, August 1999. 2673, August 1999.
[13] Petke, R. and I. King, "Registration Procedures for URL Scheme [12] Petke, R. and I. King, "Registration Procedures for URL Scheme
Names", BCP 35, RFC 2717, November 1999. Names", BCP 35, RFC 2717, November 1999.
[14] Connolly, D. and L. Masinter, "The 'text/html' Media Type", RFC [13] Connolly, D. and L. Masinter, "The 'text/html' Media Type", RFC
2854, June 2000. 2854, June 2000.
[15] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3369, [14] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3369,
August 2002. August 2002.
[16] Faltstrom, P., Hoffman, P. and A. Costello, "Internationalizing [15] Faltstrom, P., Hoffman, P. and A. Costello, "Internationalizing
Domain Names in Applications (IDNA)", RFC 3490, March 2003. Domain Names in Applications (IDNA)", RFC 3490, March 2003.
[16] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD
63, RFC 3629, November 2003.
Author's Address Author's Address
Simon Josefsson Simon Josefsson
EMail: simon@josefsson.org EMail: simon@josefsson.org
Appendix A. Revision Changes Appendix A. Revision Changes
Note to RFC editor: This appendix is to be removed on publication. Note to RFC editor: Remove this appendix before publication.
A.1 Changes since -06 A.1 Changes since -06
The MIME registration templates for text/dns and application/dns was The MIME registration templates for text/dns and application/dns was
removed, and will be defined in separate documents. removed, and will be defined in separate documents.
Improved discussion related to which mnemonics that must be Improved discussion related to which mnemonics that must be
supported. The interoperability problem that provoked the supported. The interoperability problem that provoked the
clarification is also mentioned. clarification is also mentioned.
skipping to change at page 11, line 8 skipping to change at page 11, line 14
A.3 Changes since -08 A.3 Changes since -08
Modifications derived from Last-Call comments: Made more clear that Modifications derived from Last-Call comments: Made more clear that
DNS URIs does not imply use of the DNS protocol, but the issue is not DNS URIs does not imply use of the DNS protocol, but the issue is not
stressed because of the apparent inflamatory state of affairs. Added stressed because of the apparent inflamatory state of affairs. Added
informative references to HTML and FTP. Clarified that dnsname can informative references to HTML and FTP. Clarified that dnsname can
be empty. Clarified that first dnsqueryelement "win" in case of be empty. Clarified that first dnsqueryelement "win" in case of
ambiguity. Clarified security consideration with respect to unknown ambiguity. Clarified security consideration with respect to unknown
dnsqueryelements. Use "authority" instead of "server". Say "IANA dnsqueryelements. Use "authority" instead of "server". Say "IANA
registered" instead of "standard". Interoperability note about binary registered" instead of "standard". Interoperability note about
DNS labels. Typos. binary DNS labels. Typos.
A.4 Changes since -09
Use legal texts from RFC 3667. Update UTF-8 reference to RFC 3629.
Simplified introduction. Discuss relative and absolute dnsname's.
Clarify that empty dnsname correspond to the root. Change so that
dns:foo?TYPE=A;TYPE=TXT is invalid, instead of meaning TYPE=A. The
underspecified extension mechanism was dropped; now only TYPE= and
CLASS= are permitted. Remove background discussion of why the
dnsname field is made a IDN unaware domain name slot. Use standard
DNS escaping (i.e, "\." for ".") instead of broken approach that
violated the URI specification. Improve examples. Add security
considerations.
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 End of changes. 

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