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DNSEXT Working Group M. Stapp
Internet-Draft Cisco Systems, Inc.
Expires: April 23, 2004 T. Lemon
A. Gustafsson
Nominum, Inc.
October 24, 2003
A DNS RR for Encoding DHCP Information (DHCID RR)
<draft-ietf-dnsext-dhcid-rr-07.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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 April 23, 2004.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
It is possible for multiple DHCP clients to attempt to update the
same DNS FQDN as they obtain DHCP leases. Whether the DHCP server or
the clients themselves perform the DNS updates, conflicts can arise.
To resolve such conflicts, "Resolution of DNS Name Conflicts"[1]
proposes storing client identifiers in the DNS to unambiguously
associate domain names with the DHCP clients to which they refer.
This memo defines a distinct RR type for this purpose for use by
DHCP clients and servers, the "DHCID" RR.
Stapp, et. al. Expires April 23, 2004 [Page 1]
Internet-Draft The DHCID RR October 2003
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The DHCID RR . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1 DHCID RDATA format . . . . . . . . . . . . . . . . . . . . . 4
3.2 DHCID Presentation Format . . . . . . . . . . . . . . . . . 4
3.3 The DHCID RR Type Codes . . . . . . . . . . . . . . . . . . 4
3.4 Computation of the RDATA . . . . . . . . . . . . . . . . . . 5
3.5 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.5.1 Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.5.2 Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Use of the DHCID RR . . . . . . . . . . . . . . . . . . . . 6
5. Updater Behavior . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
References . . . . . . . . . . . . . . . . . . . . . . . . . 7
References . . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 8
Full Copyright Statement . . . . . . . . . . . . . . . . . . 10
Stapp, et. al. Expires April 23, 2004 [Page 2]
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1. 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 RFC 2119[2].
2. Introduction
A set of procedures to allow DHCP[7] clients and servers to
automatically update the DNS (RFC 1034[3], RFC 1035[4]) is proposed
in "Resolution of DNS Name Conflicts"[1].
Conflicts can arise if multiple DHCP clients wish to use the same
DNS name. To resolve such conflicts, "Resolution of DNS Name
Conflicts"[1] proposes storing client identifiers in the DNS to
unambiguously associate domain names with the DHCP clients using
them. In the interest of clarity, it is preferable for this DHCP
information to use a distinct RR type. This memo defines a distinct
RR for this purpose for use by DHCP clients or servers, the "DHCID"
RR.
In order to avoid exposing potentially sensitive identifying
information, the data stored is the result of a one-way MD5[5] hash
computation. The hash includes information from the DHCP client's
REQUEST message as well as the domain name itself, so that the data
stored in the DHCID RR will be dependent on both the client
identification used in the DHCP protocol interaction and the domain
name. This means that the DHCID RDATA will vary if a single client
is associated over time with more than one name. This makes it
difficult to 'track' a client as it is associated with various
domain names.
The MD5 hash algorithm has been shown to be weaker than the SHA-1
algorithm; it could therefore be argued that SHA-1 is a better
choice. However, SHA-1 is significantly slower than MD5. A
successful attack of MD5's weakness does not reveal the original
data that was used to generate the signature, but rather provides a
new set of input data that will produce the same signature. Because
we are using the MD5 hash to conceal the original data, the fact
that an attacker could produce a different plaintext resulting in
the same MD5 output is not significant concern.
3. The DHCID RR
The DHCID RR is defined with mnemonic DHCID and type code [TBD]. The
DHCID RR is only defined in the IN class. DHCID RRs cause no
additional section processing. The DHCID RR is not a singleton type.
Stapp, et. al. Expires April 23, 2004 [Page 3]
Internet-Draft The DHCID RR October 2003
3.1 DHCID RDATA format
The RDATA section of a DHCID RR in transmission contains RDLENGTH
bytes of binary data. The format of this data and its
interpretation by DHCP servers and clients are described below.
DNS software should consider the RDATA section to be opaque. DHCP
clients or servers use the DHCID RR to associate a DHCP client's
identity with a DNS name, so that multiple DHCP clients and servers
may deterministically perform dynamic DNS updates to the same zone.
From the updater's perspective, the DHCID resource record RDATA
consists of a 16-bit identifier type, in network byte order,
followed by one or more bytes representing the actual identifier:
< 16 bits > DHCP identifier used
< n bytes > MD5 digest
3.2 DHCID Presentation Format
In DNS master files, the RDATA is represented as a single block in
base 64 encoding identical to that used for representing binary data
in RFC 2535[8]. The data may be divided up into any number of white
space separated substrings, down to single base 64 digits, which are
concatenated to form the complete RDATA. These substrings can span
lines using the standard parentheses.
3.3 The DHCID RR Type Codes
The DHCID RR Type Code specifies what data from the DHCP client's
request was used as input into the hash function. The type codes are
defined in a registry maintained by IANA, as specified in Section 7.
The initial list of assigned values for the type code is:
0x0000 = htype, chaddr from a DHCPv4 client's
DHCPREQUEST (RFC 2131)
0x0001 = The data portion from a DHCPv4 client's Client
Identifier option (RFC 2132)
0x0002 = The data portion (i.e., the DUID) from a DHCPv6
client's Client Identifier option
(draft-ietf-dhc-dhcpv6-*.txt)
0x0003 - 0xfffe = Available to be assigned by IANA
0xffff = RESERVED
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3.4 Computation of the RDATA
The DHCID RDATA is formed by concatenating the two type bytes with
some variable-length identifying data.
< type > < data >
The RDATA for all type codes other than 0xffff, which is reserved
for future expansion, is formed by concatenating the two type bytes
and a 16-byte MD5 hash value. The input to the hash function is
defined to be:
data = MD5(< identifier > < FQDN >)
The FQDN is represented in the buffer in unambiguous canonical form
as described in RFC 2535[8], section 8.1. The type code and the
identifier are related as specified in Section 3.3: the type code
describes the source of the identifier.
When the updater is using the client's link-layer address as the
identifier, the first two bytes of the DHCID RDATA MUST be zero. To
generate the rest of the resource record, the updater computes a
one-way hash using the MD5 algorithm across a buffer containing the
client's network hardware type, link-layer address, and the FQDN
data. Specifically, the first byte of the buffer contains the
network hardware type as it appeared in the DHCP 'htype' field of
the client's DHCPREQUEST message. All of the significant bytes of
the chaddr field in the client's DHCPREQUEST message follow, in the
same order in which the bytes appear in the DHCPREQUEST message. The
number of significant bytes in the 'chaddr' field is specified in
the 'hlen' field of the DHCPREQUEST message. The FQDN data, as
specified above, follows.
When the updater is using the DHCPv4 Client Identifier option sent
by the client in its DHCPREQUEST message, the first two bytes of the
DHCID RR MUST be 0x0001, in network byte order. The rest of the
DHCID RR MUST contain the results of computing an MD5 hash across
the payload of the option, followed by the FQDN. The payload of the
option consists of the bytes of the option following the option code
and length.
When the updater is using the DHCPv6 DUID sent by the client in its
REQUEST message, the first two bytes of the DHCID RR MUST be 0x0002,
in network byte order. The rest of the DHCID RR MUST contain the
results of computing an MD5 hash across the payload of the option,
followed by the FQDN. The payload of the option consists of the
bytes of the option following the option code and length.
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3.5 Examples
3.5.1 Example 1
A DHCP server allocating the IPv4 address 10.0.0.1 to a client with
Ethernet MAC address 01:02:03:04:05:06 using domain name
"client.example.com" uses the client's link-layer address to
identify the client. The DHCID RDATA is composed by setting the two
type bytes to zero, and performing an MD5 hash computation across a
buffer containing the Ethernet MAC type byte, 0x01, the six bytes of
MAC address, and the domain name (represented as specified in
Section 3.4).
client.example.com. A 10.0.0.1
client.example.com. DHCID AAAUMru0ZM5OK/PdVAJgZ/HU
3.5.2 Example 2
A DHCP server allocates the IPv4 address 10.0.12.99 to a client
which included the DHCP client-identifier option data
01:07:08:09:0a:0b:0c in its DHCP request. The server updates the
name "chi.example.com" on the client's behalf, and uses the DHCP
client identifier option data as input in forming a DHCID RR. The
DHCID RDATA is formed by setting the two type bytes to the value
0x0001, and performing an MD5 hash computation across a buffer
containing the seven bytes from the client-id option and the FQDN
(represented as specified in Section 3.4).
chi.example.com. A 10.0.12.99
chi.example.com. DHCID AAHdd5jiQ3kEjANDm82cbObk\012
4. Use of the DHCID RR
This RR MUST NOT be used for any purpose other than that detailed in
"Resolution of DNS Name Conflicts"[1]. Although this RR contains
data that is opaque to DNS servers, the data must be consistent
across all entities that update and interpret this record.
Therefore, new data formats may only be defined through actions of
the DHC Working Group, as a result of revising [1].
5. Updater Behavior
The data in the DHCID RR allows updaters to determine whether more
than one DHCP client desires to use a particular FQDN. This allows
site administrators to establish policy about DNS updates. The DHCID
RR does not establish any policy itself.
Updaters use data from a DHCP client's request and the domain name
that the client desires to use to compute a client identity hash,
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and then compare that hash to the data in any DHCID RRs on the name
that they wish to associate with the client's IP address. If an
updater discovers DHCID RRs whose RDATA does not match the client
identity that they have computed, the updater SHOULD conclude that a
different client is currently associated with the name in question.
The updater SHOULD then proceed according to the site's
administrative policy. That policy might dictate that a different
name be selected, or it might permit the updater to continue.
6. Security Considerations
The DHCID record as such does not introduce any new security
problems into the DNS. In order to avoid exposing private
information about DHCP clients to public scrutiny, a one-way hash is
used to obscure all client information. In order to make it
difficult to 'track' a client by examining the names associated with
a particular hash value, the FQDN is included in the hash
computation. Thus, the RDATA is dependent on both the DHCP client
identification data and on each FQDN associated with the client.
Administrators should be wary of permitting unsecured DNS updates to
zones which are exposed to the global Internet. Both DHCP clients
and servers SHOULD use some form of update authentication (e.g.,
TSIG[11]) when performing DNS updates.
7. IANA Considerations
IANA is requested to allocate an RR type number for the DHCID record
type.
This specification defines a new number-space for the 16-bit type
codes associated with the DHCID RR. IANA is requested to establish a
registry of the values for this number-space.
Three initial values are assigned in Section 3.3, and the value
0xFFFF is reserved for future use. New DHCID RR type codes are
tentatively assigned after the specification for the associated type
code, published as an Internet Draft, has received expert review by
a designated expert. The final assignment of DHCID RR type codes is
through Standards Action, as defined in RFC 2434[6].
8. Acknowledgements
Many thanks to Josh Littlefield, Olafur Gudmundsson, Bernie Volz,
and Ralph Droms for their review and suggestions.
Normative References
[1] Stapp, M., "Resolution of DNS Name Conflicts Among DHCP Clients
Stapp, et. al. Expires April 23, 2004 [Page 7]
Internet-Draft The DHCID RR October 2003
(draft-ietf-dhc-dns-resolution-*)", November 2002.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.
[3] Mockapetris, P., "Domain names - Concepts and Facilities", RFC
1034, Nov 1987.
[4] Mockapetris, P., "Domain names - Implementation and
Specification", RFC 1035, Nov 1987.
[5] Rivest, R., "The MD5 Message Digest Algorithm", RFC 1321, April
1992.
[6] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", RFC 2434, October 1998.
Informative References
[7] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
Mar 1997.
[8] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999.
[9] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, Mar 1997.
[10] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
(draft-ietf-dhc-dhcpv6-*.txt)", November 2002.
[11] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington,
"Secret Key Transaction Authentication for DNS (TSIG)", RFC
2845, May 2000.
Authors' Addresses
Mark Stapp
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: 978.936.1535
EMail: mjs@cisco.com
Stapp, et. al. Expires April 23, 2004 [Page 8]
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Ted Lemon
Nominum, Inc.
950 Charter St.
Redwood City, CA 94063
USA
EMail: mellon@nominum.com
Andreas Gustafsson
Nominum, Inc.
950 Charter St.
Redwood City, CA 94063
USA
EMail: gson@nominum.com
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Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS 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.
Acknowledgement
Funding for the RFC editor function is currently provided by the
Internet Society.
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DNSEXT M. Stapp
Internet-Draft Cisco Systems, Inc.
Expires: January 14, 2005 T. Lemon
A. Gustafsson
Nominum, Inc.
July 16, 2004
A DNS RR for Encoding DHCP Information (DHCID RR)
<draft-ietf-dnsext-dhcid-rr-08.txt>
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. 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 become aware will be disclosed, in accordance with
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 January 14, 2005.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
It is possible for multiple DHCP clients to attempt to update the
same DNS FQDN as they obtain DHCP leases. Whether the DHCP server or
the clients themselves perform the DNS updates, conflicts can arise.
To resolve such conflicts, "Resolution of DNS Name Conflicts" [1]
proposes storing client identifiers in the DNS to unambiguously
Stapp, et al. Expires January 14, 2005 [Page 1]
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associate domain names with the DHCP clients to which they refer.
This memo defines a distinct RR type for this purpose for use by DHCP
clients and servers, the "DHCID" RR.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The DHCID RR . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1 DHCID RDATA format . . . . . . . . . . . . . . . . . . . . 4
3.2 DHCID Presentation Format . . . . . . . . . . . . . . . . 4
3.3 The DHCID RR Type Codes . . . . . . . . . . . . . . . . . 4
3.4 Computation of the RDATA . . . . . . . . . . . . . . . . . 4
3.5 Examples . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.5.1 Example 1 . . . . . . . . . . . . . . . . . . . . . . 6
3.5.2 Example 2 . . . . . . . . . . . . . . . . . . . . . . 6
4. Use of the DHCID RR . . . . . . . . . . . . . . . . . . . . . 6
5. Updater Behavior . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1 Normative References . . . . . . . . . . . . . . . . . . . . 8
9.2 Informative References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . 10
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1. 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 RFC 2119 [2].
2. Introduction
A set of procedures to allow DHCP [7] clients and servers to
automatically update the DNS (RFC 1034 [3], RFC 1035 [4]) is proposed
in "Resolution of DNS Name Conflicts" [1].
Conflicts can arise if multiple DHCP clients wish to use the same DNS
name. To resolve such conflicts, "Resolution of DNS Name Conflicts"
[1] proposes storing client identifiers in the DNS to unambiguously
associate domain names with the DHCP clients using them. In the
interest of clarity, it is preferable for this DHCP information to
use a distinct RR type. This memo defines a distinct RR for this
purpose for use by DHCP clients or servers, the "DHCID" RR.
In order to avoid exposing potentially sensitive identifying
information, the data stored is the result of a one-way MD5 [5] hash
computation. The hash includes information from the DHCP client's
REQUEST message as well as the domain name itself, so that the data
stored in the DHCID RR will be dependent on both the client
identification used in the DHCP protocol interaction and the domain
name. This means that the DHCID RDATA will vary if a single client
is associated over time with more than one name. This makes it
difficult to 'track' a client as it is associated with various domain
names.
The MD5 hash algorithm has been shown to be weaker than the SHA-1
algorithm; it could therefore be argued that SHA-1 is a better
choice. However, SHA-1 is significantly slower than MD5. A
successful attack of MD5's weakness does not reveal the original data
that was used to generate the signature, but rather provides a new
set of input data that will produce the same signature. Because we
are using the MD5 hash to conceal the original data, the fact that an
attacker could produce a different plaintext resulting in the same
MD5 output is not significant concern.
3. The DHCID RR
The DHCID RR is defined with mnemonic DHCID and type code [TBD]. The
DHCID RR is only defined in the IN class. DHCID RRs cause no
additional section processing. The DHCID RR is not a singleton type.
Stapp, et al. Expires January 14, 2005 [Page 3]
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3.1 DHCID RDATA format
The RDATA section of a DHCID RR in transmission contains RDLENGTH
bytes of binary data. The format of this data and its interpretation
by DHCP servers and clients are described below.
DNS software should consider the RDATA section to be opaque. DHCP
clients or servers use the DHCID RR to associate a DHCP client's
identity with a DNS name, so that multiple DHCP clients and servers
may deterministically perform dynamic DNS updates to the same zone.
From the updater's perspective, the DHCID resource record RDATA
consists of a 16-bit identifier type, in network byte order, followed
by one or more bytes representing the actual identifier:
< 16 bits > DHCP identifier used
< n bytes > MD5 digest
3.2 DHCID Presentation Format
In DNS master files, the RDATA is represented as a single block in
base 64 encoding identical to that used for representing binary data
in RFC 2535 [8]. The data may be divided up into any number of white
space separated substrings, down to single base 64 digits, which are
concatenated to form the complete RDATA. These substrings can span
lines using the standard parentheses.
3.3 The DHCID RR Type Codes
The DHCID RR Type Code specifies what data from the DHCP client's
request was used as input into the hash function. The type codes are
defined in a registry maintained by IANA, as specified in Section 7.
The initial list of assigned values for the type code is:
0x0000 = htype, chaddr from a DHCPv4 client's DHCPREQUEST [7].
0x0001 = The data portion from a DHCPv4 client's Client Identifier
option [9].
0x0002 = The client's DUID (i.e., the data portion of a DHCPv6
client's Client Identifier option [10] or the DUID field from a
DHCPv4 client's Client Identifier option [12]).
0x0003 - 0xfffe = Available to be assigned by IANA.
0xffff = RESERVED
3.4 Computation of the RDATA
The DHCID RDATA is formed by concatenating the two type bytes with
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some variable-length identifying data.
< type > < data >
The RDATA for all type codes other than 0xffff, which is reserved for
future expansion, is formed by concatenating the two type bytes and a
16-byte MD5 hash value. The input to the hash function is defined to
be:
data = MD5(< identifier > < FQDN >)
The FQDN is represented in the buffer in unambiguous canonical form
as described in RFC 2535 [8], section 8.1. The type code and the
identifier are related as specified in Section 3.3: the type code
describes the source of the identifier.
When the updater is using the client's link-layer address as the
identifier, the first two bytes of the DHCID RDATA MUST be zero. To
generate the rest of the resource record, the updater computes a
one-way hash using the MD5 algorithm across a buffer containing the
client's network hardware type, link-layer address, and the FQDN
data. Specifically, the first byte of the buffer contains the
network hardware type as it appeared in the DHCP 'htype' field of the
client's DHCPREQUEST message. All of the significant bytes of the
chaddr field in the client's DHCPREQUEST message follow, in the same
order in which the bytes appear in the DHCPREQUEST message. The
number of significant bytes in the 'chaddr' field is specified in the
'hlen' field of the DHCPREQUEST message. The FQDN data, as specified
above, follows.
When the updater is using the DHCPv4 Client Identifier option sent by
the client in its DHCPREQUEST message, the first two bytes of the
DHCID RR MUST be 0x0001, in network byte order. The rest of the
DHCID RR MUST contain the results of computing an MD5 hash across the
payload of the option, followed by the FQDN. The payload of the
option consists of the bytes of the option following the option code
and length.
When the updater is using the DHCPv6 DUID sent by the client in its
REQUEST message, the first two bytes of the DHCID RR MUST be 0x0002,
in network byte order. The rest of the DHCID RR MUST contain the
results of computing an MD5 hash across the payload of the option,
followed by the FQDN. The payload of the option consists of the
bytes of the option following the option code and length.
3.5 Examples
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3.5.1 Example 1
A DHCP server allocating the IPv4 address 10.0.0.1 to a client with
Ethernet MAC address 01:02:03:04:05:06 using domain name
"client.example.com" uses the client's link-layer address to identify
the client. The DHCID RDATA is composed by setting the two type
bytes to zero, and performing an MD5 hash computation across a buffer
containing the Ethernet MAC type byte, 0x01, the six bytes of MAC
address, and the domain name (represented as specified in Section
3.4).
client.example.com. A 10.0.0.1
client.example.com. DHCID AAAUMru0ZM5OK/PdVAJgZ/HU
3.5.2 Example 2
A DHCP server allocates the IPv4 address 10.0.12.99 to a client which
included the DHCP client-identifier option data 01:07:08:09:0a:0b:0c
in its DHCP request. The server updates the name "chi.example.com"
on the client's behalf, and uses the DHCP client identifier option
data as input in forming a DHCID RR. The DHCID RDATA is formed by
setting the two type bytes to the value 0x0001, and performing an MD5
hash computation across a buffer containing the seven bytes from the
client-id option and the FQDN (represented as specified in Section
3.4).
chi.example.com. A 10.0.12.99
chi.example.com. DHCID AAHdd5jiQ3kEjANDm82cbObk\012
4. Use of the DHCID RR
This RR MUST NOT be used for any purpose other than that detailed in
"Resolution of DNS Name Conflicts" [1]. Although this RR contains
data that is opaque to DNS servers, the data must be consistent
across all entities that update and interpret this record.
Therefore, new data formats may only be defined through actions of
the DHC Working Group, as a result of revising [1].
5. Updater Behavior
The data in the DHCID RR allows updaters to determine whether more
than one DHCP client desires to use a particular FQDN. This allows
site administrators to establish policy about DNS updates. The DHCID
RR does not establish any policy itself.
Updaters use data from a DHCP client's request and the domain name
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that the client desires to use to compute a client identity hash, and
then compare that hash to the data in any DHCID RRs on the name that
they wish to associate with the client's IP address. If an updater
discovers DHCID RRs whose RDATA does not match the client identity
that they have computed, the updater SHOULD conclude that a different
client is currently associated with the name in question. The
updater SHOULD then proceed according to the site's administrative
policy. That policy might dictate that a different name be selected,
or it might permit the updater to continue.
6. Security Considerations
The DHCID record as such does not introduce any new security problems
into the DNS. In order to avoid exposing private information about
DHCP clients to public scrutiny, a one-way hash is used to obscure
all client information. In order to make it difficult to 'track' a
client by examining the names associated with a particular hash
value, the FQDN is included in the hash computation. Thus, the RDATA
is dependent on both the DHCP client identification data and on each
FQDN associated with the client.
Administrators should be wary of permitting unsecured DNS updates to
zones which are exposed to the global Internet. Both DHCP clients
and servers SHOULD use some form of update authentication (e.g., TSIG
[11]) when performing DNS updates.
7. IANA Considerations
IANA is requested to allocate an RR type number for the DHCID record
type.
This specification defines a new number-space for the 16-bit type
codes associated with the DHCID RR. IANA is requested to establish a
registry of the values for this number-space.
Three initial values are assigned in Section 3.3, and the value
0xFFFF is reserved for future use. New DHCID RR type codes are
tentatively assigned after the specification for the associated type
code, published as an Internet Draft, has received expert review by a
designated expert. The final assignment of DHCID RR type codes is
through Standards Action, as defined in RFC 2434 [6].
8. Acknowledgements
Many thanks to Josh Littlefield, Olafur Gudmundsson, Bernie Volz, and
Ralph Droms for their review and suggestions.
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9. References
9.1 Normative References
[1] Stapp, M. and B. Volz, "Resolution of DNS Name Conflicts Among
DHCP Clients (draft-ietf-dhc-dns-resolution-*)", July 2004.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] Mockapetris, P., "Domain names - concepts and facilities", STD
13, RFC 1034, November 1987.
[4] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April
1992.
[6] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
9.2 Informative References
[7] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[8] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999.
[9] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[10] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M.
Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.
[11] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington,
"Secret Key Transaction Authentication for DNS (TSIG)", RFC
2845, May 2000.
[12] Lemon, T. and B. Sommerfeld, "Node-Specific Client Identifiers
for DHCPv4 (draft-ietf-dhc-3315id-for-v4-*)", February 2004.
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Authors' Addresses
Mark Stapp
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: 978.936.1535
EMail: mjs@cisco.com
Ted Lemon
Nominum, Inc.
950 Charter St.
Redwood City, CA 94063
USA
EMail: mellon@nominum.com
Andreas Gustafsson
Nominum, Inc.
950 Charter St.
Redwood City, CA 94063
USA
EMail: gson@nominum.com
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Disclaimer of Validity
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.
Copyright Statement
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.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
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INTERNET-DRAFT Donald E. Eastlake 3rd
Clarifies STD0013 Motorola Laboratories
Expires December 2004 July 2004
Domain Name System (DNS) Case Insensitivity Clarification
------ ---- ------ ----- ---- ------------- -------------
<draft-ietf-dnsext-insensitive-04.txt>
Donald E. Eastlake 3rd
Status of This Document
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance with
RFC 3668.
Distribution of this document is unlimited. Comments should be sent
to the DNSEXT working group at namedroppers@ops.ietf.org.
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC 2026. 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.
Abstract
Domain Name System (DNS) names are "case insensitive". This document
explains exactly what that means and provides a clear specification
of the rules. This clarification should not have any interoperability
consequences.
D. Eastlake 3rd [Page 1]
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Acknowledgements
The contributions to this document of Rob Austein, Olafur
Gudmundsson, Daniel J. Anderson, Alan Barrett, Marc Blanchet, Dana,
Andreas Gustafsson, Andrew Main, and Scott Seligman are gratefully
acknowledged.
Table of Contents
Status of This Document....................................1
Abstract...................................................1
Acknowledgements...........................................2
Table of Contents..........................................2
1. Introduction............................................3
2. Case Insensitivity of DNS Labels........................3
2.1 Escaping Unusual DNS Label Octets......................3
2.2 Example Labels with Escapes............................4
3. Name Lookup, Label Types, and CLASS.....................4
3.1 Original DNS Label Types...............................5
3.2 Extended Label Type Case Insensitivity Considerations..5
3.3 CLASS Case Insensitivity Considerations................5
4. Case on Input and Output................................6
4.1 DNS Output Case Preservation...........................6
4.2 DNS Input Case Preservation............................6
5. Internationalized Domain Names..........................7
6. Security Considerations.................................7
Copyright and Disclaimer...................................9
Normative References.......................................9
Informative References....................................10
-02 to -03 Changes........................................10
-03 to -04 Changes........................................11
Author's Address..........................................11
Expiration and File Name..................................11
D. Eastlake 3rd [Page 2]
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1. Introduction
The Domain Name System (DNS) is the global hierarchical replicated
distributed database system for Internet addressing, mail proxy, and
other information. Each node in the DNS tree has a name consisting of
zero or more labels [STD 13][RFC 1591, 2606] that are treated in a
case insensitive fashion. This document clarifies the meaning of
"case insensitive" for the DNS.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119].
2. Case Insensitivity of DNS Labels
DNS was specified in the era of [ASCII]. DNS names were expected to
look like most host names or Internet email address right halves (the
part after the at-sign, "@") or be numeric as in the in-addr.arpa
part of the DNS name space. For example,
foo.example.net.
aol.com.
www.gnu.ai.mit.edu.
or 69.2.0.192.in-addr.arpa.
Case varied alternatives to the above would be DNS names like
Foo.ExamplE.net.
AOL.COM.
WWW.gnu.AI.mit.EDU.
or 69.2.0.192.in-ADDR.ARPA.
However, the individual octets of which DNS names consist are not
limited to valid ASCII character codes. They are 8-bit bytes and all
values are allowed. Many applications, however, interpret them as
ASCII characters.
2.1 Escaping Unusual DNS Label Octets
In Master Files [STD 13] and other human readable and writable ASCII
contexts, an escape is needed for the byte value for period (0x2E,
".") and all octet values outside of the inclusive range of 0x21
("!") to 0x7E ("~"). That is to say, 0x2E and all octet values in
the two inclusive ranges 0x00 to 0x20 and 0x7F to 0xFF.
One typographic convention for octets that do not correspond to an
D. Eastlake 3rd [Page 3]
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ASCII printing graphic is to use a back-slash followed by the value
of the octet as an unsigned integer represented by exactly three
decimal digits.
The same convention can be used for printing ASCII characters so that
they will be treated as a normal label character. This includes the
back-slash character used in this convention itself which can be
expressed as \092 or \\ and the special label separator period (".")
which can be expressed as and \046 or \. respectively. It is
advisable to avoid using a backslash to quote an immediately
following non-printing ASCII character code to avoid implementation
difficulties.
A back-slash followed by only one or two decimal digits is undefined.
A back-slash followed by four decimal digits produces two octets, the
first octet having the value of the first three digits considered as
a decimal number and the second octet being the character code for
the fourth decimal digit.
2.2 Example Labels with Escapes
The first example below shows embedded spaces and a period (".")
within a label. The second one show a 5 octet label where the second
octet has all bits zero, the third is a backslash, and the fourth
octet has all bits one.
Donald\032E\.\032Eastlake\0323rd.example.
and a\000\\\255z.example.
3. Name Lookup, Label Types, and CLASS
The design decision was made that comparisons on name lookup for DNS
queries should be case insensitive [STD 13]. That is to say, a lookup
string octet with a value in the inclusive range of 0x41 to 0x5A, the
upper case ASCII letters, MUST match the identical value and also
match the corresponding value in the inclusive range 0x61 to 0x7A,
the lower case ASCII letters. And a lookup string octet with a lower
case ASCII letter value MUST similarly match the identical value and
also match the corresponding value in the upper case ASCII letter
range.
(Historical Note: the terms "upper case" and "lower case" were
invented after movable type. The terms originally referred to the
two font trays for storing, in partitioned areas, the different
physical type elements. Before movable type, the nearest equivalent
terms were "majuscule" and "minuscule".)
D. Eastlake 3rd [Page 4]
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One way to implement this rule would be, when comparing octets, to
subtract 0x20 from all octets in the inclusive range 0x61 to 0x7A
before the comparison. Such an operation is commonly known as "case
folding" but implementation via case folding is not required. Note
that the DNS case insensitivity does NOT correspond to the case
folding specified in iso-8859-1 or iso-8859-2. For example, the
octets 0xDD (\221) and 0xFD (\253) do NOT match although in other
contexts, where they are interpreted as the upper and lower case
version of "Y" with an acute accent, they might.
3.1 Original DNS Label Types
DNS labels in wire encoded names have a type associated with them.
The original DNS standard [RFC 1035] had only two types. ASCII
labels, with a length of from zero to 63 octets, and indirect labels
which consist of an offset pointer to a name location elsewhere in
the wire encoding on a DNS message. (The ASCII label of length zero
is reserved for use as the name of the root node of the name tree.)
ASCII labels follow the ASCII case conventions described herein and,
as stated above, can actually contain arbitrary byte values. Indirect
labels are, in effect, replaced by the name to which they point which
is then treated with the case insensitivity rules in this document.
3.2 Extended Label Type Case Insensitivity Considerations
DNS was extended by [RFC 2671] to have additional label type numbers
available. (The only such type defined so far is the BINARY type [RFC
2673].)
The ASCII case insensitivity conventions only apply to ASCII labels,
that is to say, label type 0x0, whether appearing directly or invoked
by indirect labels.
3.3 CLASS Case Insensitivity Considerations
As described in [STD 13] and [RFC 2929], DNS has an additional axis
for data location called CLASS. The only CLASS in global use at this
time is the "IN" or Internet CLASS.
The handling of DNS label case is not CLASS dependent.
D. Eastlake 3rd [Page 5]
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4. Case on Input and Output
While ASCII label comparisons are case insensitive, [STD 13] says
case MUST be preserved on output, and preserved when convenient on
input. However, this means less than it would appear since the
preservation of case on output is NOT required when output is
optimized by the use of indirect labels, as explained below.
4.1 DNS Output Case Preservation
[STD 13] views the DNS namespace as a node tree. ASCII output is as
if a name was marshaled by taking the label on the node whose name is
to be output, converting it to a typographically encoded ASCII
string, walking up the tree outputting each label encountered, and
preceding all labels but the first with a period ("."). Wire output
follows the same sequence but each label is wire encoded and no
periods inserted. No "case conversion" or "case folding" is done
during such output operations, thus "preserving" case. However, to
optimize output, indirect labels may be used to point to names
elsewhere in the DNS answer. In determining whether the name to be
pointed to, for example the QNAME, is the "same" as the remainder of
the name being optimized, the case insensitive comparison specified
above is done. Thus such optimization MAY easily destroy the output
preservation of case. This type of optimization is commonly called
"name compression".
4.2 DNS Input Case Preservation
Originally, DNS input came from an ASCII Master File as defined in
[STD 13] or a zone transfer. DNS Dynamic update and incremental zone
transfers [RFC 1995] have been added as a source of DNS data [RFC
2136, 3007]. When a node in the DNS name tree is created by any of
such inputs, no case conversion is done. Thus the case of ASCII
labels is preserved if they are for nodes being created. However,
when a name label is input for a node that already exist in DNS data
being held, the situation is more complex. Implementations may retain
the case first input for such a label or allow new input to override
the old case or even maintain separate copies preserving the input
case.
For example, if data with owner name "foo.bar.example" is input and
then later data with owner name "xyz.BAR.example" is input, the name
of the label on the "bar.example" node, i.e. "bar", might or might
not be changed to "BAR" or the actual input case could be preserved.
Thus later retrieval of data stored under "xyz.bar.example" in this
case can easily return data with "xyz.BAR.example". The same
D. Eastlake 3rd [Page 6]
INTERNET-DRAFT DNS Case Insensitivity
considerations apply when inputting multiple data records with owner
names differing only in case. For example, if an "A" record is stored
as the first resourced record under owner name "xyz.BAR.example" and
then a second "A" record is stored under "XYZ.BAR.example", the
second MAY be stored with the first (lower case initial label) name
or the second MAY override the first so that only an upper case
initial label is retained or both capitalizations MAY be kept.
Note that the order of insertion into a server database of the DNS
name tree nodes that appear in a Master File is not defined so that
the results of inconsistent capitalization in a Master File are
unpredictable output capitalization.
5. Internationalized Domain Names
A scheme has been adopted for "internationalized domain names" and
"internationalized labels" as described in [RFC 3490, 3454, 3491, and
3492]. It makes most of [UNICODE] available through a separate
application level transformation from internationalized domain name
to DNS domain name and from DNS domain name to internationalized
domain name. Any case insensitivity that internationalized domain
names and labels have varies depending on the script and is handled
entirely as part of the transformation described in [RFC 3454] and
[RFC 3491] which should be seen for further details. This is not a
part of the DNS as standardized in STD 13.
6. Security Considerations
The equivalence of certain DNS label types with case differences, as
clarified in this document, can lead to security problems. For
example, a user could be confused by believing two domain names
differing only in case were actually different names.
Furthermore, a domain name may be used in contexts other than the
DNS. It could be used as a case sensitive index into some data base
system. Or it could be interpreted as binary data by some integrity
or authentication code system. These problems can usually be handled
by using a standardized or "canonical" form of the DNS ASCII type
labels, that is, always mapping the ASCII letter value octets in
ASCII labels to some specific pre-chosen case, either upper case or
lower case. An example of a canonical form for domain names (and also
a canonical ordering for them) appears in Section 8 of [RFC 2535].
See also [RFC 3597].
Finally, a non-DNS name may be stored into DNS with the false
expectation that case will always be preserved. For example, although
D. Eastlake 3rd [Page 7]
INTERNET-DRAFT DNS Case Insensitivity
this would be quite rare, on a system with case sensitive email
address local parts, an attempt to store two "RP" records that
differed only in case would probably produce unexpected results that
might have security implications. That is because the entire email
address, including the possibly case sensitive local or left hand
part, is encoded into a DNS name in a readable fashion where the case
of some letters might be changed on output as described above.
D. Eastlake 3rd [Page 8]
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Copyright and Disclaimer
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.
Normative References
[ASCII] - ANSI, "USA Standard Code for Information Interchange",
X3.4, American National Standards Institute: New York, 1968.
[RFC 1034, 1035] - See [STD 13].
[RFC 1995] - M. Ohta, "Incremental Zone Transfer in DNS", August
1996.
[RFC 2119] - S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", March 1997.
[RFC 2136] - P. Vixie, Ed., S. Thomson, Y. Rekhter, J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)", April 1997.
[RFC 2535] - D. Eastlake, "Domain Name System Security Extensions",
March 1999.
[RFC 3007] - B. Wellington, "Secure Domain Name System (DNS) Dynamic
Update", November 2000.
[RFC 3597] - Andreas Gustafsson, "Handling of Unknown DNS RR Types",
draft-ietf-dnsext-unknown-rrs-05.txt, March 2003.
[STD 13]
- P. Mockapetris, "Domain names - concepts and facilities", RFC
1034, November 1987.
- P. Mockapetris, "Domain names - implementation and
specification", RFC 1035, November 1987.
D. Eastlake 3rd [Page 9]
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Informative References
[RFC 1591] - J. Postel, "Domain Name System Structure and
Delegation", March 1994.
[RFC 2606] - D. Eastlake, A. Panitz, "Reserved Top Level DNS Names",
June 1999.
[RFC 2929] - D. Eastlake, E. Brunner-Williams, B. Manning, "Domain
Name System (DNS) IANA Considerations", September 2000.
[RFC 2671] - P. Vixie, "Extension mechanisms for DNS (EDNS0)", August
1999.
[RFC 2673] - M. Crawford, "Binary Labels in the Domain Name System",
August 1999.
[RFC 3092] - D. Eastlake 3rd, C. Manros, E. Raymond, "Etymology of
Foo", 1 April 2001.
[RFC 3454] - P. Hoffman, M. Blanchet, "Preparation of
Internationalized String ("stringprep")", December 2002.
[RFC 3490] - P. Faltstrom, P. Hoffman, A. Costello,
"Internationalizing Domain Names in Applications (IDNA)", March 2003.
[RFC 3491] - P. Hoffman, M. Blanchet, "Nameprep: A Stringprep Profile
for Internationalized Domain Names (IDN)", March 2003.
[RFC 3492] - A. Costello, "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications (IDNA)", March
2003.
[UNICODE] - The Unicode Consortium, "The Unicode Standard",
<http://www.unicode.org/unicode/standard/standard.html>.
-02 to -03 Changes
The following changes were made between draft version -02 and -03:
1. Add internationalized domain name section and references.
2. Change to indicate that later input of a label for an existing DNS
name tree node may or may not be normalized to the earlier input or
override it or both may be preserved.
3. Numerous minor wording changes.
D. Eastlake 3rd [Page 10]
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-03 to -04 Changes
The following changes were made between draft version -03 and -04:
1. Change to conform to the new IPR, Copyright, etc., notice
requirements.
2. Change in some section headers for clarity.
3. Drop section on wildcards.
4. Add emphasis on loss of case preservation due to name compression.
5. Add references to RFCs 1995 and 3092.
Author's Address
Donald E. Eastlake 3rd
Motorola Laboratories
155 Beaver Street
Milford, MA 01757 USA
Telephone: +1 508-786-7554 (w)
+1 508-634-2066 (h)
EMail: Donald.Eastlake@motorola.com
Expiration and File Name
This draft expires December 2004.
Its file name is draft-ietf-dnsext-insensitive-04.txt.
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@@ -7,8 +7,8 @@
DNSEXT Working Group Levon Esibov DNSEXT Working Group Levon Esibov
INTERNET-DRAFT Bernard Aboba INTERNET-DRAFT Bernard Aboba
Category: Standards Track Dave Thaler Category: Standards Track Dave Thaler
<draft-ietf-dnsext-mdns-32.txt> Microsoft <draft-ietf-dnsext-mdns-33.txt> Microsoft
25 June 2004 18 July 2004
Linklocal Multicast Name Resolution (LLMNR) Linklocal Multicast Name Resolution (LLMNR)
@@ -16,28 +16,29 @@ Category: Standards Track Dave Thaler
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed, patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance with and any of which I become aware will be disclosed, in accordance with
RFC 3667. RFC 3668.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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The list of current Internet-Drafts can be accessed at http:// The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on November 22, 2004. This Internet-Draft will expire on January 2, 2005.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society 2004. All rights reserved.
Abstract Abstract
@@ -54,14 +55,13 @@ Abstract
Esibov, Aboba & Thaler Standards Track [Page 1] Esibov, Aboba & Thaler Standards Track [Page 1]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
Table of Contents Table of Contents
@@ -96,6 +96,7 @@ Table of Contents
Acknowledgments .............................................. 24 Acknowledgments .............................................. 24
Authors' Addresses ........................................... 25 Authors' Addresses ........................................... 25
Intellectual Property Statement .............................. 25 Intellectual Property Statement .............................. 25
Disclaimer of Validity ....................................... 26
Full Copyright Statement ..................................... 26 Full Copyright Statement ..................................... 26
@@ -114,14 +115,13 @@ Full Copyright Statement ..................................... 26
Esibov, Aboba & Thaler Standards Track [Page 2] Esibov, Aboba & Thaler Standards Track [Page 2]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
1. Introduction 1. Introduction
@@ -181,7 +181,7 @@ Esibov, Aboba & Thaler Standards Track [Page 3]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
1.1. Requirements 1.1. Requirements
@@ -241,7 +241,7 @@ Esibov, Aboba & Thaler Standards Track [Page 4]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
This may occur via any mechanism, including DHCPv4 [RFC2131] or This may occur via any mechanism, including DHCPv4 [RFC2131] or
@@ -301,7 +301,7 @@ Esibov, Aboba & Thaler Standards Track [Page 5]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
2.1. LLMNR packet format 2.1. LLMNR packet format
@@ -361,7 +361,7 @@ Esibov, Aboba & Thaler Standards Track [Page 6]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
LLMNR senders and responders MUST support standard queries (opcode LLMNR senders and responders MUST support standard queries (opcode
@@ -421,7 +421,7 @@ Esibov, Aboba & Thaler Standards Track [Page 7]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
question section of an LLMNR query. LLMNR responders MUST silently question section of an LLMNR query. LLMNR responders MUST silently
@@ -481,7 +481,7 @@ Esibov, Aboba & Thaler Standards Track [Page 8]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
responder has another RR as well; the SOA RR MUST NOT be the only RR responder has another RR as well; the SOA RR MUST NOT be the only RR
@@ -541,7 +541,7 @@ Esibov, Aboba & Thaler Standards Track [Page 9]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
[e] Responders MUST NOT respond using cached data. [e] Responders MUST NOT respond using cached data.
@@ -601,7 +601,7 @@ Esibov, Aboba & Thaler Standards Track [Page 10]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
significantly complicates implementation of LLMNR and would not be significantly complicates implementation of LLMNR and would not be
@@ -661,7 +661,7 @@ Esibov, Aboba & Thaler Standards Track [Page 11]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
Section 2.4 discusses use of TCP for LLMNR queries and responses. In Section 2.4 discusses use of TCP for LLMNR queries and responses. In
@@ -721,7 +721,7 @@ Esibov, Aboba & Thaler Standards Track [Page 12]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
2.7. Retransmission and jitter 2.7. Retransmission and jitter
@@ -781,7 +781,7 @@ Esibov, Aboba & Thaler Standards Track [Page 13]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
Due to the TTL minimalization necessary when caching an RRset, all Due to the TTL minimalization necessary when caching an RRset, all
@@ -841,7 +841,7 @@ Esibov, Aboba & Thaler Standards Track [Page 14]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
round trip estimates, with exponential backoff. [RFC1536] Section 4 round trip estimates, with exponential backoff. [RFC1536] Section 4
@@ -901,7 +901,7 @@ Esibov, Aboba & Thaler Standards Track [Page 15]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
IPv4 hosts can be resolved over IPv4 without LLMNR. However, if no IPv4 hosts can be resolved over IPv4 without LLMNR. However, if no
@@ -961,7 +961,7 @@ Esibov, Aboba & Thaler Standards Track [Page 16]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
There are some scenarios when multiple responders MAY respond to the There are some scenarios when multiple responders MAY respond to the
@@ -1021,7 +1021,7 @@ Esibov, Aboba & Thaler Standards Track [Page 17]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
it MUST check whether the response arrived on an interface different it MUST check whether the response arrived on an interface different
@@ -1081,7 +1081,7 @@ Esibov, Aboba & Thaler Standards Track [Page 18]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
multiple interfaces, and receives replies from more than one, the multiple interfaces, and receives replies from more than one, the
@@ -1141,7 +1141,7 @@ Esibov, Aboba & Thaler Standards Track [Page 19]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
of both hosts responding to the name 'A'. Link-local addresses will of both hosts responding to the name 'A'. Link-local addresses will
@@ -1201,7 +1201,7 @@ Esibov, Aboba & Thaler Standards Track [Page 20]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
possible for an attacker to spoof a response to a frequent query possible for an attacker to spoof a response to a frequent query
@@ -1261,7 +1261,7 @@ Esibov, Aboba & Thaler Standards Track [Page 21]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
eliminating the benefits of cache separation. As a result, LLMNR is eliminating the benefits of cache separation. As a result, LLMNR is
@@ -1321,7 +1321,7 @@ Esibov, Aboba & Thaler Standards Track [Page 22]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
@@ -1381,7 +1381,7 @@ Esibov, Aboba & Thaler Standards Track [Page 23]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
[RFC2937] Smith, C., "The Name Service Search Option for DHCP", RFC [RFC2937] Smith, C., "The Name Service Search Option for DHCP", RFC
@@ -1441,7 +1441,7 @@ Esibov, Aboba & Thaler Standards Track [Page 24]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
Authors' Addresses Authors' Addresses
@@ -1478,7 +1478,7 @@ Intellectual Property Statement
might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and IETF's procedures with respect to rights in standards-track and
standards- related documentation can be found in BCP-11. Copies of standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such obtain a general license or permission for the use of such
@@ -1501,34 +1501,25 @@ Esibov, Aboba & Thaler Standards Track [Page 25]
INTERNET-DRAFT LLMNR 25 June 2004 INTERNET-DRAFT LLMNR 18 July 2004
Full Copyright Statement Disclaimer of Validity
Copyright (C) The Internet Society (2004). All Rights Reserved. This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
This document and translations of it may be copied and furnished to OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
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Copyright Statement
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.
Open Issues Open Issues
Open issues with this specification are tracked on the following web Open issues with this specification are tracked on the following web
@@ -1536,10 +1527,19 @@ Open Issues
http://www.drizzle.com/~aboba/DNSEXT/llmnrissues.html http://www.drizzle.com/~aboba/DNSEXT/llmnrissues.html
Expiration Date
This memo is filed as <draft-ietf-dnsext-mdns-32.txt>, and expires
December 22, 2004.