draft-ietf-dnsext-dhcid-rr-09.txt   draft-ietf-dnsext-dhcid-rr-10.txt 
DNSEXT M. Stapp DNSEXT M. Stapp
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Expires: August 13, 2005 T. Lemon Expires: March 28, 2006 T. Lemon
A. Gustafsson A. Gustafsson
Nominum, Inc. Nominum, Inc.
February 9, 2005 September 24, 2005
A DNS RR for Encoding DHCP Information (DHCID RR) A DNS RR for Encoding DHCP Information (DHCID RR)
<draft-ietf-dnsext-dhcid-rr-09.txt> <draft-ietf-dnsext-dhcid-rr-10.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is subject to all provisions By submitting this Internet-Draft, each author represents that any
of Section 3 of RFC 3667. By submitting this Internet-Draft, each applicable patent or other IPR claims of which he or she is aware
author represents that any applicable patent or other IPR claims of have been or will be disclosed, and any of which he or she becomes
which he or she is aware have been or will be disclosed, and any of aware will be disclosed, in accordance with Section 6 of BCP 79.
which he or she become aware will be disclosed, in accordance with
RFC 3668.
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This Internet-Draft will expire on August 13, 2005. This Internet-Draft will expire on March 28, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
It is possible for multiple DHCP clients to attempt to update the 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 same DNS FQDN as they obtain DHCP leases. Whether the DHCP server or
the clients themselves perform the DNS updates, conflicts can arise. the clients themselves perform the DNS updates, conflicts can arise.
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Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
It is possible for multiple DHCP clients to attempt to update the 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 same DNS FQDN as they obtain DHCP leases. Whether the DHCP server or
the clients themselves perform the DNS updates, conflicts can arise. the clients themselves perform the DNS updates, conflicts can arise.
To resolve such conflicts, "Resolution of DNS Name Conflicts" [1] To resolve such conflicts, "Resolution of DNS Name Conflicts" [1]
proposes storing client identifiers in the DNS to unambiguously proposes storing client identifiers in the DNS to unambiguously
associate domain names with the DHCP clients to which they refer. 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 This memo defines a distinct RR type for this purpose for use by DHCP
clients and servers, the "DHCID" RR. clients and servers, the "DHCID" RR.
Table of Contents Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The DHCID RR . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The DHCID RR . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1 DHCID RDATA format . . . . . . . . . . . . . . . . . . . . 4 3.1. DHCID RDATA format . . . . . . . . . . . . . . . . . . . . 4
3.2 DHCID Presentation Format . . . . . . . . . . . . . . . . 4 3.2. DHCID Presentation Format . . . . . . . . . . . . . . . . 4
3.3 The DHCID RR Type Codes . . . . . . . . . . . . . . . . . 4 3.3. The DHCID RR Type Codes . . . . . . . . . . . . . . . . . 4
3.4 Computation of the RDATA . . . . . . . . . . . . . . . . . 4 3.4. Computation of the RDATA . . . . . . . . . . . . . . . . . 4
3.5 Examples . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.5.1 Example 1 . . . . . . . . . . . . . . . . . . . . . . 6 3.5.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 5
3.5.2 Example 2 . . . . . . . . . . . . . . . . . . . . . . 6 3.5.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 6
4. Use of the DHCID RR . . . . . . . . . . . . . . . . . . . . . 6 4. Use of the DHCID RR . . . . . . . . . . . . . . . . . . . . . 6
5. Updater Behavior . . . . . . . . . . . . . . . . . . . . . . . 6 5. Updater Behavior . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1 Normative References . . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . . 8
9.2 Informative References . . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . . . . 10
1. Terminology 1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [2]. document are to be interpreted as described in RFC 2119 [2].
2. Introduction 2. Introduction
A set of procedures to allow DHCP [7] clients and servers to A set of procedures to allow DHCP [7] clients and servers to
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are using the MD5 hash to conceal the original data, the fact that an are using the MD5 hash to conceal the original data, the fact that an
attacker could produce a different plaintext resulting in the same attacker could produce a different plaintext resulting in the same
MD5 output is not significant concern. MD5 output is not significant concern.
3. The DHCID RR 3. The DHCID RR
The DHCID RR is defined with mnemonic DHCID and type code [TBD]. The 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 DHCID RR is only defined in the IN class. DHCID RRs cause no
additional section processing. The DHCID RR is not a singleton type. additional section processing. The DHCID RR is not a singleton type.
3.1 DHCID RDATA format 3.1. DHCID RDATA format
The RDATA section of a DHCID RR in transmission contains RDLENGTH The RDATA section of a DHCID RR in transmission contains RDLENGTH
bytes of binary data. The format of this data and its interpretation bytes of binary data. The format of this data and its interpretation
by DHCP servers and clients are described below. by DHCP servers and clients are described below.
DNS software should consider the RDATA section to be opaque. DHCP DNS software should consider the RDATA section to be opaque. DHCP
clients or servers use the DHCID RR to associate a DHCP client's 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 identity with a DNS name, so that multiple DHCP clients and servers
may deterministically perform dynamic DNS updates to the same zone. may deterministically perform dynamic DNS updates to the same zone.
From the updater's perspective, the DHCID resource record RDATA From the updater's perspective, the DHCID resource record RDATA
consists of a 16-bit identifier type, in network byte order, followed consists of a 16-bit identifier type, in network byte order, followed
by one or more bytes representing the actual identifier: by one or more bytes representing the actual identifier:
< 16 bits > DHCP identifier used < 16 bits > DHCP identifier used
< n bytes > MD5 digest < n bytes > MD5 digest
3.2 DHCID Presentation Format 3.2. DHCID Presentation Format
In DNS master files, the RDATA is represented as a single block in In DNS master files, the RDATA is represented as a single block in
base 64 encoding identical to that used for representing binary data 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 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 space separated substrings, down to single base 64 digits, which are
concatenated to form the complete RDATA. These substrings can span concatenated to form the complete RDATA. These substrings can span
lines using the standard parentheses. lines using the standard parentheses.
3.3 The DHCID RR Type Codes 3.3. The DHCID RR Type Codes
The DHCID RR Type Code specifies what data from the DHCP client's 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 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. defined in a registry maintained by IANA, as specified in Section 7.
The initial list of assigned values for the type code is: The initial list of assigned values for the type code is:
0x0000 = htype, chaddr from a DHCPv4 client's DHCPREQUEST [7]. 0x0000 = htype, chaddr from a DHCPv4 client's DHCPREQUEST [7].
0x0001 = The data portion from a DHCPv4 client's Client Identifier 0x0001 = The data portion from a DHCPv4 client's Client Identifier
option [9]. option [9].
0x0002 = The client's DUID (i.e., the data portion of a DHCPv6 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 client's Client Identifier option [10] or the DUID field from a
DHCPv4 client's Client Identifier option [12]). DHCPv4 client's Client Identifier option [12]).
0x0003 - 0xfffe = Available to be assigned by IANA. 0x0003 - 0xfffe = Available to be assigned by IANA.
0xffff = RESERVED 0xffff = RESERVED
3.4 Computation of the RDATA 3.4. Computation of the RDATA
The DHCID RDATA is formed by concatenating the two type bytes with The DHCID RDATA is formed by concatenating the two type bytes with
some variable-length identifying data. some variable-length identifying data.
< type > < data > < type > < data >
The RDATA for all type codes other than 0xffff, which is reserved for 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 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 16-byte MD5 hash value. The input to the hash function is defined to
be: be:
data = MD5(< identifier > < FQDN >) data = MD5(< identifier > < FQDN >)
The FQDN is represented in the buffer in unambiguous canonical form 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 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 identifier are related as specified in Section 3.3: the type code
describes the source of the identifier. describes the source of the identifier.
When the updater is using the client's link-layer address as the 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 identifier, the first two bytes of the DHCID RDATA MUST be zero. To
generate the rest of the resource record, the updater computes a generate the rest of the resource record, the updater computes a one-
one-way hash using the MD5 algorithm across a buffer containing the way hash using the MD5 algorithm across a buffer containing the
client's network hardware type, link-layer address, and the FQDN client's network hardware type, link-layer address, and the FQDN
data. Specifically, the first byte of the buffer contains the data. Specifically, the first byte of the buffer contains the
network hardware type as it appeared in the DHCP 'htype' field of 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 client's DHCPREQUEST message. All of the significant bytes of the
chaddr field in the client's DHCPREQUEST message follow, in the same chaddr field in the client's DHCPREQUEST message follow, in the same
order in which the bytes appear in the DHCPREQUEST message. The order in which the bytes appear in the DHCPREQUEST message. The
number of significant bytes in the 'chaddr' field is specified in the number of significant bytes in the 'chaddr' field is specified in the
'hlen' field of the DHCPREQUEST message. The FQDN data, as specified 'hlen' field of the DHCPREQUEST message. The FQDN data, as specified
above, follows. above, follows.
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option consists of the bytes of the option following the option code option consists of the bytes of the option following the option code
and length. and length.
When the updater is using the DHCPv6 DUID sent by the client in its 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, 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 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, results of computing an MD5 hash across the payload of the option,
followed by the FQDN. The payload of the option consists of the followed by the FQDN. The payload of the option consists of the
bytes of the option following the option code and length. bytes of the option following the option code and length.
3.5 Examples 3.5. Examples
3.5.1 Example 1 3.5.1. Example 1
A DHCP server allocating the IPv4 address 10.0.0.1 to a client with 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 Ethernet MAC address 01:02:03:04:05:06 using domain name
"client.example.com" uses the client's link-layer address to identify "client.example.com" uses the client's link-layer address to identify
the client. The DHCID RDATA is composed by setting the two type the client. The DHCID RDATA is composed by setting the two type
bytes to zero, and performing an MD5 hash computation across a buffer bytes to zero, and performing an MD5 hash computation across a buffer
containing the Ethernet MAC type byte, 0x01, the six bytes of MAC containing the Ethernet MAC type byte, 0x01, the six bytes of MAC
address, and the domain name (represented as specified in address, and the domain name (represented as specified in
Section 3.4). Section 3.4).
client.example.com. A 10.0.0.1 client.example.com. A 10.0.0.1
client.example.com. DHCID AAAUMru0ZM5OK/PdVAJgZ/HU client.example.com. DHCID AAAUMru0ZM5OK/PdVAJgZ/HU
3.5.2 Example 2 3.5.2. Example 2
A DHCP server allocates the IPv4 address 10.0.12.99 to a client which 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 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" in its DHCP request. The server updates the name "chi.example.com"
on the client's behalf, and uses the DHCP client identifier option 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 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 setting the two type bytes to the value 0x0001, and performing an MD5
hash computation across a buffer containing the seven bytes from the hash computation across a buffer containing the seven bytes from the
client-id option and the FQDN (represented as specified in client-id option and the FQDN (represented as specified in
Section 3.4). Section 3.4).
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designated expert. The final assignment of DHCID RR type codes is designated expert. The final assignment of DHCID RR type codes is
through Standards Action, as defined in RFC 2434 [6]. through Standards Action, as defined in RFC 2434 [6].
8. Acknowledgements 8. Acknowledgements
Many thanks to Josh Littlefield, Olafur Gudmundsson, Bernie Volz, and Many thanks to Josh Littlefield, Olafur Gudmundsson, Bernie Volz, and
Ralph Droms for their review and suggestions. Ralph Droms for their review and suggestions.
9. References 9. References
9.1 Normative References 9.1. Normative References
[1] Stapp, M. and B. Volz, "Resolution of DNS Name Conflicts Among [1] Stapp, M. and B. Volz, "Resolution of DNS Name Conflicts Among
DHCP Clients (draft-ietf-dhc-dns-resolution-*)", July 2004. DHCP Clients (draft-ietf-dhc-dns-resolution-*)", September 2005.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement [2] 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.
[3] Mockapetris, P., "Domain names - concepts and facilities", [3] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987. STD 13, RFC 1034, November 1987.
[4] Mockapetris, P., "Domain names - implementation and [4] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, November 1987.
[5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April [5] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321,
1992. April 1992.
[6] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [6] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
9.2 Informative References 9.2. Informative References
[7] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, [7] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997. March 1997.
[8] Eastlake, D., "Domain Name System Security Extensions", [8] Eastlake, D., "Domain Name System Security Extensions",
RFC 2535, March 1999. RFC 2535, March 1999.
[9] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor [9] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997. Extensions", RFC 2132, March 1997.
[10] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. [10] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003. (DHCPv6)", RFC 3315, July 2003.
[11] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington, [11] Vixie, P., Gudmundsson, O., Eastlake, D., and B. Wellington,
"Secret Key Transaction Authentication for DNS (TSIG)", "Secret Key Transaction Authentication for DNS (TSIG)",
RFC 2845, May 2000. RFC 2845, May 2000.
[12] Lemon, T. and B. Sommerfeld, "Node-Specific Client Identifiers [12] Lemon, T. and B. Sommerfeld, "Node-Specific Client Identifiers
for DHCPv4 (draft-ietf-dhc-3315id-for-v4-*)", February 2004. for DHCPv4 (draft-ietf-dhc-3315id-for-v4-*)", June 2005.
Authors' Addresses Authors' Addresses
Mark Stapp Mark Stapp
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Ave. 1414 Massachusetts Ave.
Boxborough, MA 01719 Boxborough, MA 01719
USA USA
Phone: 978.936.1535 Phone: 978.936.1535
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