draft-ietf-dhc-dhcp-dns-03.txt   draft-ietf-dhc-dhcp-dns-04.txt 
Network Working Group Yakov Rekhter Network Working Group Yakov Rekhter
Internet Draft Cisco Systems Internet Draft Cisco Systems
Expiration Date: September 1997 March 1997 Expiration Date: November 1997 May 1997
Interaction between DHCP and DNS Interaction between DHCP and DNS
draft-ietf-dhc-dhcp-dns-03.txt draft-ietf-dhc-dhcp-dns-04.txt
1. Status of this Memo 1. Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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originate an update for the A RR (associated with the client's FQDN). originate an update for the A RR (associated with the client's FQDN).
The update shall be originated following the procedures described in The update shall be originated following the procedures described in
[DynDNS]. [DynDNS].
If a client does not want to be responsible for updating the FQDN to If a client does not want to be responsible for updating the FQDN to
IP address mapping for the FQDN and address(es) used by the client, IP address mapping for the FQDN and address(es) used by the client,
then the client shall include the Client FQDN option in the then the client shall include the Client FQDN option in the
DHCPREQUEST message originated by the client. The Flags field in the DHCPREQUEST message originated by the client. The Flags field in the
option shall be set to 1. option shall be set to 1.
A client that delegates the responsibility for updating the FQDN to
IP address mapping to a server may not receive any indications
(either positive or negative) from the server whether the server was
able to perform the update. In this case the client may use DNS query
to check whether the mapping is updated.
A client should set the RCODE1 and RCODE2 fields in the Client FQDN A client should set the RCODE1 and RCODE2 fields in the Client FQDN
option to 0 when sending the option. option to 0 when sending the option.
Whether the client wants to be responsible for updating the FQDN to Whether the client wants to be responsible for updating the FQDN to
IP address mapping, or whether the client wants to delegate this IP address mapping, or whether the client wants to delegate this
responsibility to a server is a local to the client matter. The responsibility to a server is a local to the client matter. The
choice between the two alternatives may be based on a particular choice between the two alternatives may be based on a particular
security model that is used with the Dynamic DNS Update protocol security model that is used with the Dynamic DNS Update protocol
(e.g., only a client may have sufficient credentials to perform (e.g., only a client may have sufficient credentials to perform
updates to the FQDN to IP address mapping for its FQDN). updates to the FQDN to IP address mapping for its FQDN).
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If a client releases its address lease prior to the lease expiration If a client releases its address lease prior to the lease expiration
time, and the client is responsible for updating its A RR(s), the time, and the client is responsible for updating its A RR(s), the
client should delete the A RR (following the procedures described in client should delete the A RR (following the procedures described in
[DynDNS]) associated with the leased address before sending DHCP [DynDNS]) associated with the leased address before sending DHCP
RELEASE message. RELEASE message.
4.3. DHCP Server behavior 4.3. 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 shall originate an the message with a DHCPACK message, the server may originate an
update for the PTR RR (associated with the address leased to the update for the PTR RR (associated with the address leased to the
client). The server shall originate the update before the server client). The update shall be originated following the procedures
sends the DHCPACK message to the client. The update shall be described in Section 4.4. The server may originate the update before
originated following the procedures described in [DynDNS]. The RCODE the server sends the DHCPACK message to the client. In this case the
from the update [DynDNS] should be carried to the client in the RCODE from the update [DynDNS] shall be carried to the client in the
RCODE1 field of the Client FQDN option in the DHCPACK message. The RCODE1 field of the Client FQDN option in the DHCPACK message and the
RCODE2 field should be set to 0. RCODE2 field shall be set to 0. Alternatively, the server 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 FQDN
option in the DHCPACK message shall be set to 255, and the RCODE2
field shall be set to 0. The choice between the two alternatives is
a local to a DHCP server matter.
In addition, if the Client FQDN option carried in the DHCPREQUEST In addition, if the Client FQDN option carried in the DHCPREQUEST
message has its Flags field set to 1, then the server shall originate message has its Flags field set to 1, then the server shall originate
an update for the A RR (associated with the FQDN carried in the an update for the A RR (associated with the FQDN carried in the
option). The server shall originate the update before the server option). The update shall be originated following the procedures
sends the DHCPACK message to the client. The update shall be described in Section 4.4. The server may originate the update before
originated following the procedures described in [DynDNS]. The RCODE the server sends the DHCPACK message to the client. In this case the
from the update [DynDNS] should be carried to the client in the RCODE from the update [DynDNS] shall be carried to the client in the
RCODE2 field of the Client FQDN option in the DHCPACK message. RCODE2 field of the Client FQDN option in the DHCPACK message.
Alternatively the server may send the DHCPACK message to the client
without waiting for the update to be completed. In this case the
RCODE2 field of the Client FQDN option in the DHCKACK message shall
be set to 255. The choice between the two alternatives is a local to
the server matter.
Even, if the Client FQDN option carried in the DHCPREQUEST message Even, if the Client FQDN option carried in the DHCPREQUEST message
has its Flags field set to 0 (indicating that the client wants to has its Flags field set to 0 (indicating that the client wants to
update the A RR), the server could (under configuration control) update the A RR), the server could (under configuration control)
update the A RR. The server shall originate the update before the update the A RR. The update shall be originated following the
server sends the DHCPACK message to the client. The update shall be procedures described in Section 4.4. The server may originate the
originated following the procedures described in [DynDNS]. The RCODE update before the server sends the DHCPACK message to the client. In
from the update [DynDNS] should be carried to the client in the this case the RCODE from the update [DynDNS] shall be carried to the
RCODE2 field of the Client FQDN option in the DHCPACK message. The client in the RCODE2 field of the Client FQDN option in the DHCPACK
Flags field in the Client FQND option shall be set to 3. message, and the Flags field in the Client FQND option shall be set
to 3. Alternatively, the server may send the DHCPACK message to the
client without waiting for the update to be completed. In this case
the RCODE2 field of the Client FQDN option in the DHCKACK message
shall be set to 255, and the Flags field in the Client FQDN option
shall be set to 3. The choice between the two alternatives is a local
to the server matter.
Whether a DHCP server is always responsible for updating the FQDN to Whether a DHCP server is always responsible for updating the FQDN to
IP address mapping (in addition to updating the IP to FQDN mapping), IP address mapping (in addition to updating the IP to FQDN mapping),
regarless of the wishes of a DHCP client, is a local to the server regarless of the wishes of a DHCP client, is a local to the server
matter. The choice between the two alternatives may be based on a matter. The choice between the two alternatives may be based on a
particular security model. particular security model.
When a server receives a DHCPREQUEST message from a client, and the When a server receives a DHCPREQUEST message from a client, and the
message contains the Client FQDN option, the server shall ignore the message contains the Client FQDN option, the server shall ignore the
value carried in the RCODE1 and RCODE2 fields of the option. value carried in the RCODE1 and RCODE2 fields of the option.
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If the DHCPREQUST message received by a DHCP server from a DHCP If the DHCPREQUST message received by a DHCP server from a DHCP
client doesn't carry the Client FQDN option, and the DHCP client client doesn't carry the Client FQDN option, and the DHCP client
acquires its FQDN from a DHCP server (as part of a normal DHCP acquires its FQDN from a DHCP server (as part of a normal DHCP
transaction), then the server may be configured to update both A and transaction), then the server may be configured to update both A and
PTR RRs. In this scenario the DHCPOFFER message originated by the PTR RRs. In this scenario the DHCPOFFER message originated by the
server shall carry the Domain Name option, and the client server shall carry the Domain Name option, and the client
acknowledges the use of the FQDN carried in this option by including acknowledges the use of the FQDN carried in this option by including
the option (with the FQDN) in the DHCPREQUEST originated by the the option (with the FQDN) in the DHCPREQUEST originated by the
client. The updates shall be originated following the procedures client. The updates shall be originated following the procedures
described in [DynDNS]. described in Section 4.4.
If a server originates updates for both the A and PTR RRs, then the If a server originates updates for both the A and PTR RRs, then the
order in which the updates are generated is not significant. order in which the updates are generated is not significant.
If a server detects that a lease on an address that the server leases If a server detects that a lease on an address that the server leases
to a client expires, the server should delete the PTR RR associated to a client expires, the server should delete the PTR RR associated
with the address. In addition, if the client authorized the server to with the address. In addition, if the client authorized the server to
update its A RR, the server should also delete the A RR. The deletion update its A RR, the server should also delete the A RR. The deletion
should follow the procedures described in [DynDNS]. should follow the procedures described in [DynDNS].
If a server terminates a lease on an address prior to the lease If a server terminates a lease on an address prior to the lease
expiration time, the server should delete the PTR RR associated with expiration time, the server should delete the PTR RR associated with
the address. In addition, if the client (that leased the address) the address. In addition, if the client (that leased the address)
authorized the server to update its A RR, the server should also authorized the server to update its A RR, the server should also
delete the A RR. The deletion should follow the procedures described delete the A RR. The deletion should follow the procedures described
in [DynDNS]. in [DynDNS].
4.4. Procedures for performing DNS updates
When a DHCP server needs to update the PTR RR for a particular IP
address, the server first has to delete all the PTR RRs associated
with the address, and then add a new PTR RR for that address.
When a DHCP server needs to update the A RR for a particular FQDN,
the server first has to delete all the A RRs associated with that
FQDN, and then add a new A RR for that FQDN. Note that this rule
precludes the ability to support multi-homed hosts in the scenario
where A RRs are updated by a DHCP server. Therefore, multi-homed
hosts should perform updates to their A RRs by themselves.
Procedures for deleting and adding RRs are described in [DynDNS].
5. Updating other RRs 5. Updating other RRs
The procedures described in this document cover updates only to the A The procedures described in this document cover updates only to the A
and PTR RRs. Updating other types of RRs is outside the scope of this and PTR RRs. Updating other types of RRs is outside the scope of this
document. document.
6. Security Considerations 6. Security Considerations
Security issues are not discussed in this document. Security issues are not discussed in this document.
skipping to change at page 6, line 41 skipping to change at page 7, line 31
specification", RFC1035, 11/01/1987 specification", RFC1035, 11/01/1987
[RFC1541] R. Droms, "Dynamic Host Configuration Protocol", RFC1541, [RFC1541] R. Droms, "Dynamic Host Configuration Protocol", RFC1541,
10/27/1993 10/27/1993
[RFC1594] A. Marine, J. Reynolds, G. Malkin, "FYI on Questions and [RFC1594] A. Marine, J. Reynolds, G. Malkin, "FYI on Questions and
Answer Answers to Commonly asked ``New Internet User'' Questions", Answer Answers to Commonly asked ``New Internet User'' Questions",
RFC1594, 03/11/1994 RFC1594, 03/11/1994
[DynDNS] P. Vixie, S. Thomson, Y. Rekhter, J. Bound, "Dynamic Updates [DynDNS] P. Vixie, S. Thomson, Y. Rekhter, J. Bound, "Dynamic Updates
in the Domain Name System (DNS UPDATE)", draft-ietf-dnsind-dynDNS- in the Domain Name System (DNS UPDATE)", RFC2136, April 1997
09.txt
8. Acknowledgements 8. Acknowledgements
Many thanks to Mark Beyer, Jim Bound, Ralph Droms, Peter Ford, Edie Many thanks to Mark Beyer, Jim Bound, Ralph Droms, Peter Ford, Edie
Gunter, Michael Lewis, Michael Patton, and Glenn Stump for their Gunter, Stuart Kwan, Ted Lemon, Michael Lewis, Michael Patton, Mark
review and comments. Stapp, and Glenn Stump for their review and comments.
9. Author Information 9. Author Information
Yakov Rekhter Yakov Rekhter
cisco Systems, Inc. cisco Systems, Inc.
170 Tasman Dr. 170 Tasman Dr.
San Jose, CA 95134 San Jose, CA 95134
Phone: (914) 528-0090 Phone: (914) 528-0090
email: yakov@cisco.com email: yakov@cisco.com
 End of changes. 

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