draft-ietf-dnsext-dhcid-rr-01.txt   draft-ietf-dnsext-dhcid-rr-02.txt 
Network Working Group M. Stapp DNSEXT Working Group M. Stapp
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Expires: June 1, 2001 T. Lemon Expires: August 31, 2001 T. Lemon
A. Gustafsson A. Gustafsson
Nominum, Inc. Nominum, Inc.
December 2000 March 2, 2001
A DNS RR for Encoding DHCP Information A DNS RR for Encoding DHCP Information
<draft-ietf-dnsext-dhcid-rr-01.txt> <draft-ietf-dnsext-dhcid-rr-02.txt>
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as other groups may also distribute working documents as
Internet-Drafts. Internet-Drafts.
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months and may be updated, replaced, or obsoleted by other documents months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as reference at any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on June 1, 2001. This Internet-Draft will expire on August 31, 2001.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract Abstract
A situation can arise where multiple DHCP clients request the same A situation can arise where multiple DHCP clients request the same
DNS name from their (possibly distinct) DHCP servers. To resolve DNS name from their (possibly distinct) DHCP servers. To resolve
such conflicts, 'Resolution of DNS Name Conflicts'[5] proposes such conflicts, 'Resolution of DNS Name Conflicts'[6] proposes
storing client identifiers in the DNS to unambiguously associate storing client identifiers in the DNS to unambiguously associate
domain names with the DHCP clients "owning" them. This memo defines domain names with the DHCP clients "owning" them. This memo defines
a distinct RR type for use by DHCP servers, the "DHCID" RR. a distinct RR type for use by DHCP 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
4. DHCID RDATA format . . . . . . . . . . . . . . . . . . . . . . 3 4. DHCID RDATA format . . . . . . . . . . . . . . . . . . . . . . 3
4.1 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Appendix A: Base 64 Encoding . . . . . . . . . . . . . . . . . 4 7. Appendix A: Base 64 Encoding . . . . . . . . . . . . . . . . . 5
References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 7
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 8 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 8
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[1]. document are to be interpreted as described in RFC 2119[1].
2. Introduction 2. Introduction
A set of procedures to allow DHCP[2] clients and servers to A set of procedures to allow DHCP[2] clients and servers to
automatically update the DNS (RFC1034[3], RFC1035[4]) is proposed in automatically update the DNS (RFC1034[4], RFC1035[5]) is proposed in
"Resolution of DNS Name Conflicts"[5]. "Resolution of DNS Name Conflicts"[6].
A situation can arise where multiple DHCP clients wish to use the A situation can arise where multiple DHCP clients wish to use the
same DNS name. To resolve such conflicts, Resolution of DNS Name same DNS name. To resolve such conflicts, Resolution of DNS Name
Conflicts[5] proposes storing client identifiers in the DNS to Conflicts[6] proposes storing client identifiers in the DNS to
unambiguously associate domain names with the DHCP clients using unambiguously associate domain names with the DHCP clients using
them. In the interest of clarity, it would be preferable for this them. In the interest of clarity, it would be preferable for this
DHCP information to use a distinct RR type. DHCP information to use a distinct RR type.
This memo defines a distinct RR type for this purpose for use by This memo defines a distinct RR type for this purpose for use by
DHCP clients or servers, the "DHCID" RR. DHCP clients or servers, the "DHCID" RR.
3. The DHCID RR 3. The DHCID RR
The DHCID RR is defined with mnemonic DHCID and type code [TBD]. The DHCID RR is defined with mnemonic DHCID and type code [TBD].
4. DHCID RDATA format 4. 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 bytes of binary data. The format of this data and its
interpretation by DHCP servers and clients are described below. interpretation by DHCP servers and clients are described below.
DNS software should consider the RDATA section to be opaque. In DNS DNS software should consider the RDATA section to be opaque. In DNS
master files, the RDATA is represented in base 64 (see Appendix A) master files, the RDATA is represented in base 64 encoding (see
and may be divided up into any number of white space separated Appendix A (Section 7)) and may be divided up into any number of
substrings, down to single base 64 digits, which are concatenated to white space separated substrings, down to single base 64 digits,
obtain the full signature. These substrings can span lines using which are concatenated to obtain the full signature. These
the standard parenthesis. This format is identical to that used for substrings can span lines using the standard parenthesis. This
representing binary data in DNSSEC (RFC2535[6]). format is identical to that used for representing binary data in
DNSSEC (RFC2535[7]).
DHCP clients or servers use the DHCID RR to associate a DHCP 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 client's identity with a DNS name, so that multiple DHCP clients and
servers may safely perform dynamic DNS updates to the same zone. servers may safely perform dynamic DNS updates to the same zone.
From the updater's perspective, the DHCID resource record consists From the updater's perspective, the DHCID resource record consists
of a 16-bit identifier type, followed by one or more bytes of a 16-bit identifier type, followed by one or more bytes
representing the actual identifier. There are two possible forms representing the actual identifier.
for a DHCID RR - one that is used when the DHCP server is using the
client's link-layer address to identify it, and one that is used
when the DHCP server is using some DHCP option that the DHCP client
sent to identify it. When the link-layer address is used as the
identifier, the first two bytes of the RRDATA are set to 0. When a
DHCP option is used as the identifier, the first two bytes of the
RRDATA contain the option number, in network byte order. The two
bytes 0xffff are reserved for future extensibility. In both cases,
the remainder of the RRDATA is the result of performing a one-way
hash across the identifier.
The details of the method used to generate the data in the RR and The type code can have one of three classes of values. The first
the use to which a DHCP client or server may put this association class contains just the value zero. This type indicates that the
are beyond the scope of this draft, and are discussed in the remaining contents of the DHCID record encode an identifier that is
specification of the DNS update behavior, 'Resolution of DNS Name based on the client's link-layer network address.
Conflicts'[5]. This RR MUST NOT be used for any purpose other than
that detailed in the DHC document. Althought this RR contains data The second class of types contains just the value 0xFFFF. This type
that is opaque to DNS servers, the data is meaningful to DHCP code is reserved for future extensibility.
updaters. Therefore, new data formats may only be defined through
actions of the DHC Working Group. The third class of types contains all the values not included in the
first two - that is, every value other than zero or 0xFFFF. Types in
this class indicate that the remaining contents of the DHCID record
encode an identifier that is based on the DHCP option whose code is
the same as the specified type. The most common value in this class
at the time of the writing of this draft is 61, which is the DHCP
option code[3] for the Client Identifier option.
The data following the type code (for type codes other than 0xFFFF)
is derived by running a one-way hash across the identifying
information. The details of this are specified in "Resolution of
DNS Name Conflicts"[6].
This RR MUST NOT be used for any purpose other than that detailed in
"Resolution of DNS Name Conflicts"[6]. Althought 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 [6].
4.1 Example 4.1 Example
A DHCP server allocating the IPv4 address 10.0.0.1 to a client A DHCP server allocating the IPv4 address 10.0.0.1 to a client
"client.org.nil" might use the client's link-layer address to "client.org.nil" might use the client's link-layer address to
identify the client: identify the client:
client.org.nil. A 10.0.0.1 client.org.nil. A 10.0.0.1
client.org.nil. DHCID AAAY KREX Igqt wYgQ o93/ yNlJ client.org.nil. DHCID AAAY KREX Igqt wYgQ o93/ yNlJ
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information about DHCP clients to public scrutiny, a one-way-hash is information about DHCP clients to public scrutiny, a one-way-hash is
used to obscure all client information. used to obscure all client information.
6. IANA Considerations 6. IANA Considerations
IANA is requested to allocate an RR type number for the DHCID record IANA is requested to allocate an RR type number for the DHCID record
type. type.
7. Appendix A: Base 64 Encoding 7. Appendix A: Base 64 Encoding
The following encoding technique is taken from RFC 2045[7] by N. The following encoding technique is taken from RFC 2045[8] by N.
Borenstein and N. Freed. It is reproduced here in an edited form Borenstein and N. Freed. It is reproduced here in an edited form
for convenience. for convenience.
A 65-character subset of US-ASCII is used, enabling 6 bits to be A 65-character subset of US-ASCII is used, enabling 6 bits to be
represented per printable character. (The extra 65th character, "=", represented per printable character. (The extra 65th character, "=",
is used to signify a special processing function.) is used to signify a special processing function.)
The encoding process represents 24-bit groups of input bits as The encoding process represents 24-bit groups of input bits as
output strings of 4 encoded characters. Proceeding from left to output strings of 4 encoded characters. Proceeding from left to
right, a 24-bit input group is formed by concatenating 3 8-bit input right, a 24-bit input group is formed by concatenating 3 8-bit input
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three characters followed by one "=" padding character. three characters followed by one "=" padding character.
References References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997. Levels", RFC 2119, March 1997.
[2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, Mar [2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, Mar
1997. 1997.
[3] Mockapetris, P., "Domain names - Concepts and Facilities", RFC [3] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, Mar 1997.
[4] Mockapetris, P., "Domain names - Concepts and Facilities", RFC
1034, Nov 1987. 1034, Nov 1987.
[4] Mockapetris, P., "Domain names - Implementation and [5] Mockapetris, P., "Domain names - Implementation and
Specification", RFC 1035, Nov 1987. Specification", RFC 1035, Nov 1987.
[5] Stapp, M., "Resolution of DNS Name Conflicts Among DHCP Clients [6] Stapp, M., "Resolution of DNS Name Conflicts Among DHCP Clients
(draft-ietf-dhc-dns-resolution-*)", July 2000. (draft-ietf-dhc-dns-resolution-*)", July 2000.
[6] Eastlake, D., "Domain Name System Security Extensions", RFC [7] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999. 2535, March 1999.
[7] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [8] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies", Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, November 1996. RFC 2045, November 1996.
Authors' Addresses Authors' Addresses
Mark Stapp Mark Stapp
Cisco Systems, Inc. Cisco Systems, Inc.
250 Apollo Dr. 250 Apollo Dr.
Chelmsford, MA 01824 Chelmsford, MA 01824
USA USA
skipping to change at page 8, line 7 skipping to change at page 8, line 7
Andreas Gustafsson Andreas Gustafsson
Nominum, Inc. Nominum, Inc.
950 Charter St. 950 Charter St.
Redwood City, CA 94063 Redwood City, CA 94063
USA USA
EMail: gson@nominum.com EMail: gson@nominum.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2001). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
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