draft-ietf-dhc-fqdn-option-05.txt   draft-ietf-dhc-fqdn-option-06.txt 
DHC Working Group M. Stapp DHC Working Group M. Stapp
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Expires: May 2, 2003 Y. Rekhter Expires: April 26, 2004 Y. Rekhter
Juniper Networks Juniper Networks
November 1, 2002 October 27, 2003
The DHCP Client FQDN Option The DHCP Client FQDN Option
<draft-ietf-dhc-fqdn-option-05.txt> <draft-ietf-dhc-fqdn-option-06.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 May 2, 2003. This Internet-Draft will expire on April 26, 2004.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
DHCP provides a powerful mechanism for IP host configuration. DHCP provides a powerful mechanism for IP host configuration.
However, the configuration capability provided by DHCP does not However, the configuration capability provided by DHCP does not
include updating DNS, and specifically updating the name to address include updating DNS, and specifically updating the name to address
and address to name mappings maintained in the DNS. and address to name mappings maintained in the DNS.
This document specifies a DHCP option which can be used to exchange This document specifies a DHCP option which can be used to exchange
information about a DHCP client's fully-qualified domain name, and information about a DHCP client's fully-qualified domain name, and
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4. The Client FQDN Option . . . . . . . . . . . . . . . . . . . 4 4. The Client FQDN Option . . . . . . . . . . . . . . . . . . . 4
4.1 The Flags Field . . . . . . . . . . . . . . . . . . . . . . 5 4.1 The Flags Field . . . . . . . . . . . . . . . . . . . . . . 5
4.2 The RCODE Fields . . . . . . . . . . . . . . . . . . . . . . 6 4.2 The RCODE Fields . . . . . . . . . . . . . . . . . . . . . . 6
4.3 The Domain Name Field . . . . . . . . . . . . . . . . . . . 6 4.3 The Domain Name Field . . . . . . . . . . . . . . . . . . . 6
4.3.1 Deprecated ASCII Encoding . . . . . . . . . . . . . . . . . 7 4.3.1 Deprecated ASCII Encoding . . . . . . . . . . . . . . . . . 7
5. DHCP Client behavior . . . . . . . . . . . . . . . . . . . . 7 5. DHCP Client behavior . . . . . . . . . . . . . . . . . . . . 7
6. DHCP Server Behavior . . . . . . . . . . . . . . . . . . . . 9 6. DHCP Server Behavior . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
References . . . . . . . . . . . . . . . . . . . . . . . . . 13 References . . . . . . . . . . . . . . . . . . . . . . . . . 13
References . . . . . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14
Full Copyright Statement . . . . . . . . . . . . . . . . . . 15 Full Copyright Statement . . . . . . . . . . . . . . . . . . 15
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
DNS (RFC1034[2], RFC1035[3]) maintains (among other things) the DNS (RFC1034[2], RFC1035[3]) maintains (among other things) the
information about mapping between hosts' Fully Qualified Domain information about mapping between hosts' Fully Qualified Domain
Names (FQDNs)[4] and IP addresses assigned to the hosts. The Names (FQDNs)[7] and IP addresses assigned to the hosts. The
information is maintained in two types of Resource Records (RRs): A information is maintained in two types of Resource Records (RRs): A
and PTR. The A RR contains mapping from a FQDN to an IP address; the and PTR. The A RR contains mapping from a FQDN to an IP address; the
PTR RR contains mapping from an IP address to a FQDN. The DNS PTR RR contains mapping from an IP address to a FQDN. The DNS
update specification (RFC2136[5]) describes a mechanism that enables update specification (RFC 2136[4]) describes a mechanism that
DNS information to be updated over a network. enables DNS information to be updated over a network.
DHCP[6] provides a mechanism by which a host (a DHCP client) can DHCP[5] provides a mechanism by which a host (a DHCP client) can
acquire certain configuration information, along with its IP acquire certain configuration information, along with its IP
address(es). However, DHCP does not provide any mechanisms to update address(es). However, DHCP does not provide any mechanisms to update
the DNS RRs that contain the information about mapping between the the DNS RRs that contain the information about mapping between the
host's FQDN and its IP address(es) (A and PTR RRs). Thus DNS host's FQDN and its IP address(es) (A and PTR RRs). Thus DNS
information for a DHCP client may not exist or may be incorrect - a information for a DHCP client may not exist or may be incorrect - a
host (the client) could acquire its address by using DHCP, but the A host (the client) could acquire its address by using DHCP, but the A
RR for the host's FQDN wouldn't reflect the address that the host RR for the host's FQDN wouldn't reflect the address that the host
acquired, and the PTR RR for the acquired address wouldn't reflect acquired, and the PTR RR for the acquired address wouldn't reflect
the host's FQDN. the host's FQDN.
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to modify its own domain name. Compliant implementations MAY support to modify its own domain name. Compliant implementations MAY support
some or all of these possibilities. Furthermore, this specification some or all of these possibilities. Furthermore, this specification
applies only to DHCP client and server processes: it does not apply applies only to DHCP client and server processes: it does not apply
to other processes which initiate DNS updates. to other processes which initiate DNS updates.
This document describes a new DHCP option which a client can use to This document describes a new DHCP option which a client can use to
convey all or part of its domain name to a DHCP server. convey all or part of its domain name to a DHCP server.
Site-specific policy determines whether DHCP servers use the names Site-specific policy determines whether DHCP servers use the names
that clients offer or not, and what DHCP servers may do in cases that clients offer or not, and what DHCP servers may do in cases
where clients do not supply domain names. Another document, where clients do not supply domain names. Another document,
"Resolving Name Conflicts"[7], defines a protocol for establishing "Resolving Name Conflicts"[6], defines a protocol for establishing
policy and arbitrating conflicts when collisions occur in the use of policy and arbitrating conflicts when collisions occur in the use of
FQDNs by DHCP clients. FQDNs by DHCP clients.
4. The Client FQDN Option 4. The Client FQDN Option
To update the IP address to FQDN mapping a DHCP server needs to know To update the IP address to FQDN mapping a DHCP server needs to know
the FQDN of the client to which the server leases the address. To the FQDN of the client to which the server leases the address. To
allow the client to convey its FQDN to the server this document allow the client to convey its FQDN to the server this document
defines a new DHCP option, called "Client FQDN". The FQDN Option defines a new DHCP option, called "Client FQDN". The FQDN Option
also contains Flags and RCode fields which DHCP servers can use to also contains Flags and RCode fields which DHCP servers can use to
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it expects the DHCP server to perform any FQDN-to-IP (the A RR) DNS it expects the DHCP server to perform any FQDN-to-IP (the A RR) DNS
update on its behalf. If this bit is clear, the client indicates update on its behalf. If this bit is clear, the client indicates
that it intends to maintain its own FQDN-to-IP mapping update. that it intends to maintain its own FQDN-to-IP mapping update.
If a DHCP server intends to take responsibility for the A RR update If a DHCP server intends to take responsibility for the A RR update
whether or not the client sending the FQDN option has set the "S" whether or not the client sending the FQDN option has set the "S"
bit, it sets both the "O" bit and the "S" bit, and sends the FQDN bit, it sets both the "O" bit and the "S" bit, and sends the FQDN
option in its DHCPOFFER and/or DHCPACK messages. option in its DHCPOFFER and/or DHCPACK messages.
The data in the Domain Name field SHOULD appear in DNS-style binary The data in the Domain Name field SHOULD appear in DNS-style binary
encoding (without compression, of course), as described in encoding (without compression, of course), as described in RFC
RFC1035[3]. A client which sends the FQDN option SHOULD use this 1035[3]. A client which sends the FQDN option SHOULD use this
encoding. The client MUST set the "E" bit when the data in the encoding. The client MUST set the "E" bit when the data in the
Domain Name field is in DNS binary encoding. If a server receives an Domain Name field is in DNS binary encoding. If a server receives an
FQDN option from a client, and intends to include an FQDN option in FQDN option from a client, and intends to include an FQDN option in
its reply, it MUST use the same encoding that the client used, and its reply, it MUST use the same encoding that the client used, and
MUST set the "E" bit accordingly. MUST set the "E" bit accordingly.
Server implementors should note that earlier draft versions of this Server implementors should note that earlier draft versions of this
specification permitted an ASCII encoding of the domain name. specification permitted an ASCII encoding of the domain name.
Clients which implemented this encoding were deployed before this Clients which implemented this encoding were deployed before this
specification was completed. Server implementors which need to specification was completed. Server implementors which need to
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4.2 The RCODE Fields 4.2 The RCODE Fields
The RCODE1 and RCODE2 fields are used by a DHCP server to indicate The RCODE1 and RCODE2 fields are used by a DHCP server to indicate
to a DHCP client the Response Code from any A or PTR RR DNS updates to a DHCP client the Response Code from any A or PTR RR DNS updates
it has performed. The server may also use these fields to indicate it has performed. The server may also use these fields to indicate
whether it has attempted such an update before sending the DHCPACK whether it has attempted such an update before sending the DHCPACK
message. Each of these fields is one byte long. message. Each of these fields is one byte long.
Implementors should note that EDNS0 describes a mechanism for Implementors should note that EDNS0 describes a mechanism for
extending the length of a DNS RCODE to 12 bits. EDNS0 is specified extending the length of a DNS RCODE to 12 bits. EDNS0 is specified
in RFC2671[8]. Only the least-significant 8 bits of the RCODE from a in RFC 2671[8]. Only the least-significant 8 bits of the RCODE from
DNS update will be carried in the Client FQDN DHCP Option. This a DNS update will be carried in the Client FQDN DHCP Option. This
provides enough number space to accomodate the RCODEs defined in the provides enough number space to accomodate the RCODEs defined in the
DNS update specification. DNS update specification.
4.3 The Domain Name Field 4.3 The Domain Name Field
The Domain Name part of the option carries all or part of the FQDN The Domain Name part of the option carries all or part of the FQDN
of a DHCP client. The data in the Domain Name field SHOULD appear in of a DHCP client. The data in the Domain Name field SHOULD appear in
uncompressed DNS encoding as specified in RFC1035[3]. If the DHCP uncompressed DNS encoding as specified in RFC1035[3]. If the DHCP
client uses DNS encoding, it MUST set the third bit in the Flags client uses DNS encoding, it MUST set the third bit in the Flags
field (the "E" bit). In order to determine whether a name has field (the "E" bit). In order to determine whether a name has
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clients which send the FQDN option with the "E" bit clear are using clients which send the FQDN option with the "E" bit clear are using
an ASCII version of the Domain Name field. Servers MAY be prepared an ASCII version of the Domain Name field. Servers MAY be prepared
to return an ASCII encoded version of the Domain Name field to such to return an ASCII encoded version of the Domain Name field to such
clients. The use of ASCII encoding in this option should be clients. The use of ASCII encoding in this option should be
considered deprecated. considered deprecated.
A DHCP client which used ASCII encoding was permitted to suggest a A DHCP client which used ASCII encoding was permitted to suggest a
single label if it was not configured with a fully-qualified name. single label if it was not configured with a fully-qualified name.
Such clients send a single label as a series of ASCII characters in Such clients send a single label as a series of ASCII characters in
the Domain Name field, excluding the "." (dot) character. Such the Domain Name field, excluding the "." (dot) character. Such
clients SHOULD follow the character-set recommendations of clients SHOULD follow the character-set recommendations of RFC
RFC1034[2] and RFC1035[3]. 1034[2] and RFC 1035[3].
Server implementors should also be aware that some client software Server implementors should also be aware that some client software
may attempt to use UTF-8[10] character encoding. This information is may attempt to use UTF-8[10] character encoding. This information is
included for informational purposes only: this specification does included for informational purposes only: this specification does
not require any support for UTF-8. not require any support for UTF-8.
5. DHCP Client behavior 5. DHCP Client behavior
The following describes the behavior of a DHCP client that The following describes the behavior of a DHCP client that
implements the Client FQDN option. implements the Client FQDN option.
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address(es) used by the client, then the client MUST include the address(es) used by the client, then the client MUST include the
Client FQDN option in the DHCPREQUEST message originated by the Client FQDN option in the DHCPREQUEST message originated by the
client. A DHCP client MAY choose to include the Client FQDN option client. A DHCP client MAY choose to include the Client FQDN option
in its DISCOVER messages as well as its REQUEST messages. The in its DISCOVER messages as well as its REQUEST messages. The
least-significant ("S") bit in the Flags field in the option MUST be least-significant ("S") bit in the Flags field in the option MUST be
set to 0. Once the client's DHCP configuration is completed (the set to 0. Once the client's DHCP configuration is completed (the
client receives a DHCPACK message, and successfully completes a client receives a DHCPACK message, and successfully completes a
final check on the parameters passed in the message), the client MAY final check on the parameters passed in the message), the client MAY
originate an update for the A RR (associated with the client's originate an update for the A RR (associated with the client's
FQDN). The update SHOULD be originated following the procedures FQDN). The update SHOULD be originated following the procedures
described in RFC2136[5] and "Resolving Name Conflicts"[7]. If the described in RFC 2136[4] and "Resolving Name Conflicts"[6]. If the
DHCP server from which the client is requesting a lease includes the DHCP server from which the client is requesting a lease includes the
FQDN option in its ACK message, and if the server sets both the "S" FQDN option in its ACK message, and if the server sets both the "S"
and the "O" bits (the two least-significant bits) in the option's and the "O" bits (the two least-significant bits) in the option's
flags field, the DHCP client MUST NOT initiate an update for the flags field, the DHCP client MUST NOT initiate an update for the
name in the Domain Name field. name in the Domain Name field.
A client can choose to delegate the responsibility for updating the A client can choose to delegate the responsibility for updating the
FQDN to IP address mapping for the FQDN and address(es) used by the FQDN to IP address mapping for the FQDN and address(es) used by the
client to the server. In order to inform the server of this choice, client to the server. In order to inform the server of this choice,
the client SHOULD include the Client FQDN option in its DHCPREQUEST the client SHOULD include the Client FQDN option in its DHCPREQUEST
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(either positive or negative) from the server whether the server was (either positive or negative) from the server whether the server was
able to perform the update. In this case the client MAY use a DNS able to perform the update. In this case the client MAY use a DNS
query to check whether the mapping is updated. query to check whether the mapping is updated.
A client MUST set the RCODE1 and RCODE2 fields in the Client FQDN A client MUST set the RCODE1 and RCODE2 fields in the Client FQDN
option to 0 when sending the option. option to 0 when sending the option.
If a client releases its lease prior to the lease expiration time If a client releases its lease prior to the lease expiration time
and the client is responsible for updating its A RR, the client and the client is responsible for updating its A RR, the client
SHOULD delete the A RR (following the procedures described in SHOULD delete the A RR (following the procedures described in
"Resolving Name Conflicts"[7]) associated with the leased address "Resolving Name Conflicts"[6]) associated with the leased address
before sending a DHCP RELEASE message. Similarly, if a client was before sending a DHCP RELEASE message. Similarly, if a client was
responsible for updating its A RR, but is unable to renew its lease, responsible for updating its A RR, but is unable to renew its lease,
the client SHOULD attempt to delete the A RR before its lease the client SHOULD attempt to delete the A RR before its lease
expires. A DHCP client which has not been able to delete an A RR expires. A DHCP client which has not been able to delete an A RR
which it added (because it has lost the use of its DHCP IP address) which it added (because it has lost the use of its DHCP IP address)
should attempt to notify its administrator, perhaps by emitting a should attempt to notify its administrator, perhaps by emitting a
log message. log message.
6. DHCP Server Behavior 6. DHCP Server Behavior
When a server receives a DHCPREQUEST message from a client, if the When a server receives a DHCPREQUEST message from a client, if the
message contains the Client FQDN option, and the server replies to message contains the Client FQDN option, and the server replies to
the message with a DHCPACK message, the server may be configured to the message with a DHCPACK message, the server may be configured to
originate an update for the PTR RR (associated with the address originate an update for the PTR RR (associated with the address
leased to the client). Any such update SHOULD be originated leased to the client). Any such update SHOULD be originated
following the procedures described in "Resolving Name Conflicts"[7]. following the procedures described in "Resolving Name Conflicts"[6].
The server MAY complete the update before the server sends the The server MAY complete the update before the server sends the
DHCPACK message to the client. In this case the RCODE from the DHCPACK message to the client. In this case the RCODE from the
update MUST be carried to the client in the RCODE1 field of the update MUST be carried to the client in the RCODE1 field of the
Client FQDN option in the DHCPACK message. Alternatively, the server Client FQDN option in the DHCPACK message. Alternatively, the server
MAY send the DHCPACK message to the client without waiting for the MAY send the DHCPACK message to the client without waiting for the
update to be completed. In this case the RCODE1 field of the Client update to be completed. In this case the RCODE1 field of the Client
FQDN option in the DHCPACK message MUST be set to 255. The choice FQDN option in the DHCPACK message MUST be set to 255. The choice
between the two alternatives is entirely determined by the between the two alternatives is entirely determined by the
configuration of the DHCP server. Servers SHOULD support both configuration of the DHCP server. Servers SHOULD support both
configuration options. configuration options.
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In addition, if the Client FQDN option carried in the DHCPREQUEST In addition, if the Client FQDN option carried in the DHCPREQUEST
message has the "S" bit in its Flags field set, then the server MAY message has the "S" bit in its Flags field set, then the server MAY
originate an update for the A RR (associated with the FQDN carried originate an update for the A RR (associated with the FQDN carried
in the option) if it is configured to do so by the site's in the option) if it is configured to do so by the site's
administrator, and if it has the necessary credentials. The server administrator, and if it has the necessary credentials. The server
MAY be configured to use the name supplied in the client's FQDN MAY be configured to use the name supplied in the client's FQDN
option, or it MAY be configured to modify the supplied name, or option, or it MAY be configured to modify the supplied name, or
substitute a different name. substitute a different name.
Any such update SHOULD be originated following the procedures Any such update SHOULD be originated following the procedures
described in "Resolving Name Conflicts"[7]. The server MAY originate described in "Resolving Name Conflicts"[6]. The server MAY originate
the update before the server sends the DHCPACK message to the the update before the server sends the DHCPACK message to the
client. In this case the RCODE from the update RFC2136[5] MUST be client. In this case the RCODE from the update RFC 2136[4] MUST be
carried to the client in the RCODE2 field of the Client FQDN option carried to the client in the RCODE2 field of the Client FQDN option
in the DHCPACK message. Alternatively the server MAY send the in the DHCPACK message. Alternatively the server MAY send the
DHCPACK message to the client without waiting for the update to be DHCPACK message to the client without waiting for the update to be
completed. In this case the RCODE2 field of the Client FQDN option completed. In this case the RCODE2 field of the Client FQDN option
in the DHCPACK message MUST be set to 255. The choice between the in the DHCPACK message MUST be set to 255. The choice between the
two alternatives is entirely a matter of the DHCP server's two alternatives is entirely a matter of the DHCP server's
configuration. In either case, if the server intends to perform the configuration. In either case, if the server intends to perform the
DNS update and the client's REQUEST message included the FQDN DNS update and the client's REQUEST message included the FQDN
option, the server SHOULD include the FQDN option in its ACK option, the server SHOULD include the FQDN option in its ACK
message. If the server includes the FQDN option, it MUST set the "S" message. If the server includes the FQDN option, it MUST set the "S"
bit in the option's Flags field and MUST clear the "O" bit. bit in the option's Flags field and MUST clear the "O" bit.
Even if the Client FQDN option carried in the DHCPREQUEST message Even if the Client FQDN option carried in the DHCPREQUEST message
has the "S" bit in its Flags field clear (indicating that the client has the "S" bit in its Flags field clear (indicating that the client
wants to update the A RR), the server MAY be configured by the local wants to update the A RR), the server MAY be configured by the local
administrator to update the A RR on the client's behalf. A server administrator to update the A RR on the client's behalf. A server
which is configured to override the client's preference SHOULD which is configured to override the client's preference SHOULD
include an FQDN option in its ACK message, and MUST set both the "O" include an FQDN option in its ACK message, and MUST set both the "O"
and "S" bits in the FQDN option's Flags field. The update SHOULD be and "S" bits in the FQDN option's Flags field. The update SHOULD be
originated following the procedures described in "Resolving Name originated following the procedures described in "Resolving Name
Conflicts"[7]. The server MAY originate the update before the server Conflicts"[6]. The server MAY originate the update before the server
sends the DHCPACK message to the client. In this case the RCODE from sends the DHCPACK message to the client. In this case the RCODE from
the update RFC2136[5] MUST be carried to the client in the RCODE2 the update RFC 2136[4] MUST be carried to the client in the RCODE2
field of the Client FQDN option in the DHCPACK message. field of the Client FQDN option in the DHCPACK message.
Alternatively, the server MAY send the DHCPACK message to the client Alternatively, the server MAY send the DHCPACK message to the client
without waiting for the update to be completed. In this case the without waiting for the update to be completed. In this case the
RCODE2 field of the Client FQDN option in the DHCPACK message MUST RCODE2 field of the Client FQDN option in the DHCPACK message MUST
be set to 255. Whether the DNS update occurs before or after the be set to 255. Whether the DNS update occurs before or after the
DHCPACK is sent is entirely up to the DHCP server's configuration. DHCPACK is sent is entirely up to the DHCP server's configuration.
When a DHCP server sends the Client FQDN option to a client in the When a DHCP server sends the Client FQDN option to a client in the
DHCPACK message, the DHCP server SHOULD send its notion of the DHCPACK message, the DHCP server SHOULD send its notion of the
complete FQDN for the client in the Domain Name field. The server complete FQDN for the client in the Domain Name field. The server
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The server MUST use the same encoding format (ASCII or DNS binary The server MUST use the same encoding format (ASCII or DNS binary
encoding) that the client used in the FQDN option in its encoding) that the client used in the FQDN option in its
DHCPREQUEST, and MUST set the "E" bit in the option's Flags field DHCPREQUEST, and MUST set the "E" bit in the option's Flags field
accordingly. accordingly.
If a client's DHCPREQUEST message doesn't carry the Client FQDN If a client's DHCPREQUEST message doesn't carry the Client FQDN
option (e.g., the client doesn't implement the Client FQDN option), option (e.g., the client doesn't implement the Client FQDN option),
the server MAY be configured to update either or both of the A and the server MAY be configured to update either or both of the A and
PTR RRs. The updates SHOULD be originated following the procedures PTR RRs. The updates SHOULD be originated following the procedures
described in "Resolving Name Conflicts"[7]. described in "Resolving Name Conflicts"[6].
If a server detects that a lease on an address that the server If a server detects that a lease on an address that the server
leases to a client has expired, the server SHOULD delete any PTR RR leases to a client has expired, the server SHOULD delete any PTR RR
which it added via DNS update. In addition, if the server added an A which it added via DNS update. In addition, if the server added an A
RR on the client's behalf, the server SHOULD also delete the A RR. RR on the client's behalf, the server SHOULD also delete the A RR.
The deletion SHOULD follow the procedures described in "Resolving The deletion SHOULD follow the procedures described in "Resolving
Name Conflicts"[7]. Name Conflicts"[6].
If a server terminates a lease on an address prior to the lease's If a server terminates a lease on an address prior to the lease's
expiration time, for instance by sending a DHCPNAK to a client, the expiration time, for instance by sending a DHCPNAK to a client, the
server SHOULD delete any PTR RR which it associated with the address server SHOULD delete any PTR RR which it associated with the address
via DNS Update. In addition, if the server took responsibility for via DNS Update. In addition, if the server took responsibility for
an A RR, the server SHOULD also delete that A RR. The deletion an A RR, the server SHOULD also delete that A RR. The deletion
SHOULD follow the procedures described in "Resolving Name SHOULD follow the procedures described in "Resolving Name
Conflicts"[7]. Conflicts"[6].
7. Security Considerations 7. Security Considerations
Unauthenticated updates to the DNS can lead to tremendous confusion, Unauthenticated updates to the DNS can lead to tremendous confusion,
through malicious attack or through inadvertent misconfiguration. through malicious attack or through inadvertent misconfiguration.
Administrators should be wary of permitting unsecured DNS updates to Administrators should be wary of permitting unsecured DNS updates to
zones which are exposed to the global Internet. Both DHCP clients zones which are exposed to the global Internet. Both DHCP clients
and servers SHOULD use some form of update request origin and servers SHOULD use some form of update request origin
authentication procedure (e.g., Secure DNS Dynamic Update[12]) when authentication procedure (e.g., Secure DNS Dynamic Update[12]) when
performing DNS updates. performing DNS updates.
skipping to change at page 13, line 5 skipping to change at page 13, line 5
the remote access server was sufficient, and would therefore trust the remote access server was sufficient, and would therefore trust
the client identification encoded within the DHCP client-id. the client identification encoded within the DHCP client-id.
8. Acknowledgements 8. Acknowledgements
Many thanks to Mark Beyer, Jim Bound, Ralph Droms, Robert Elz, Peter Many thanks to Mark Beyer, Jim Bound, Ralph Droms, Robert Elz, Peter
Ford, Edie Gunter, Andreas Gustafsson, R. Barr Hibbs, Kim Kinnear, Ford, Edie Gunter, Andreas Gustafsson, R. Barr Hibbs, Kim Kinnear,
Stuart Kwan, Ted Lemon, Ed Lewis, Michael Lewis, Josh Littlefield, Stuart Kwan, Ted Lemon, Ed Lewis, Michael Lewis, Josh Littlefield,
Michael Patton, and Glenn Stump for their review and comments. Michael Patton, and Glenn Stump for their review and comments.
References Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Requirement Levels", RFC 2119, March 1997. Levels", RFC 2119, March 1997.
[2] Mockapetris, P., "Domain names - Concepts and Facilities", RFC [2] Mockapetris, P., "Domain names - Concepts and Facilities", RFC
1034, Nov 1987. 1034, Nov 1987.
[3] Mockapetris, P., "Domain names - Implementation and [3] Mockapetris, P., "Domain names - Implementation and
Specification", RFC 1035, Nov 1987. Specification", RFC 1035, Nov 1987.
[4] Marine, A., Reynolds, J. and G. Malkin, "FYI on Questions and [4] Vixie, P., Thomson, S., Rekhter, Y. and J. Bound, "Dynamic
Answers to Commonly asked ``New Internet User'' Questions",
RFC 1594, March 1994.
[5] Vixie, P., Thomson, S., Rekhter, Y. and J. Bound, "Dynamic
Updates in the Domain Name System", RFC 2136, April 1997. Updates in the Domain Name System", RFC 2136, April 1997.
[6] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, [5] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997. March 1997.
[7] Stapp, M., "Resolution of DNS Name Conflicts Among DHCP [6] Stapp, M., "Resolution of DNS Name Conflicts Among DHCP Clients
Clients (draft-ietf-dhc-ddns-resolution-*.txt)", July 2000. (draft-ietf-dhc-ddns-resolution-*.txt)", October 2003.
Informative References
[7] Marine, A., Reynolds, J. and G. Malkin, "FYI on Questions and
Answers to Commonly asked ``New Internet User'' Questions",
RFC 1594, March 1994.
[8] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, [8] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671,
August 1999. August 1999.
[9] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington, [9] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington,
"Secret Key Transaction Authentication for DNS (TSIG)", RFC "Secret Key Transaction Authentication for DNS (TSIG)", RFC
2845, May 2000. 2845, May 2000.
[10] Yergeau, F., "UTF-8, a transformation format of ISO 10646", [10] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
RFC 2279, January 1998. RFC 2279, January 1998.
skipping to change at page 14, line 9 skipping to change at page 14, line 9
[12] Wellington, B., "Secure DNS Dynamic Update", RFC 3007, [12] Wellington, B., "Secure DNS Dynamic Update", RFC 3007,
November 2000. November 2000.
[13] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", [13] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages",
RFC 3118, June 2001. RFC 3118, June 2001.
Authors' Addresses Authors' Addresses
Mark Stapp Mark Stapp
Cisco Systems, Inc. Cisco Systems, Inc.
250 Apollo Dr. 1414 Massachusetts Ave.
Chelmsford, MA 01824 Boxborough, MA 01719
USA USA
Phone: 978.244.8498 Phone: 978.936.1535
EMail: mjs@cisco.com EMail: mjs@cisco.com
Yakov Rekhter Yakov Rekhter
Juniper Networks Juniper Networks
1194 North Mathilda Avenue 1194 North Mathilda Avenue
Sunnyvale, CA 94089 Sunnyvale, CA 94089
USA USA
Phone: 408.745.2000 Phone: 408.745.2000
EMail: yakov@juniper.net EMail: yakov@juniper.net
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published 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
 End of changes. 

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