draft-ietf-dhc-server-override-01.txt   draft-ietf-dhc-server-override-02.txt 
Internet Engineering Task Force Richard Johnson Network Working Group R. Johnson
Internet Draft Kim Kinnear Internet-Draft J. Jumarasamy
Expiration: March 2005 Mark Stapp Expires: December 31, 2005 K. Kinnear
File: draft-ietf-dhc-server-override-01.txt Jay Kumarasamy M. Stapp
Cisco Systems, Inc. Cisco Systems, Inc.
June 29, 2005
DHCP Server-ID Override Suboption DHCP Server-ID Override Suboption
<draft-ietf-dhc-server-override-01.txt> draft-ietf-dhc-server-override-02.txt
September 27, 2004
Status of this Memo Status of this Memo
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, each author represents that any
patent or other IPR claims of which I am aware have been disclosed, applicable patent or other IPR claims of which he or she is aware
or will be disclosed, and any of which I become aware will be have been or will be disclosed, and any of which he or she becomes
disclosed, in accordance with RFC 3668. aware will be disclosed, in accordance with Section 6 of BCP 79.
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 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 Internet- other groups may also distribute working documents as Internet-
Drafts. 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
time. It is inappropriate to use Internet-Drafts as reference 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 December 31, 2005.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2005).
Abstract Abstract
This memo defines a new suboption of the DHCP relay information This memo defines a new suboption of the DHCP relay information
option [6] which allows the DHCP relay to specify a new value for the option [6] which allows the DHCP relay to specify a new value for the
Server-ID option, which is inserted by the DHCP Server. In some Server-ID option, which is inserted by the DHCP Server. In some
cases it is convenient for the DHCP relay to act as the actual DHCP cases it is convenient for the DHCP relay to act as the actual DHCP
server such that DHCP RENEWAL requests will come to the relay instead server such that DHCP RENEWAL requests will come to the relay instead
of going to the server directly. This gives the relay the of going to the server directly. This gives the relay the
opportunity to include the Relay Agent option with appropriate opportunity to include the Relay Agent option with appropriate
suboptions even on RENEWAL messages. suboptions even on RENEWAL messages.
This new relay agent suboption allows the relay to tell the DHCP Table of Contents
server what value to use in the Server-ID option [3]. If this
suboption is not present, the server should build the Server-ID
option in the normal fashion.
1.0 Introduction 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Server-ID Override Suboption Definition . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5. Intellectual Property Rights and Copyright . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 9
1. Introduction
There are many situations where the DHCP relay is involved and can There are many situations where the DHCP relay is involved and can
insert a relay agent option with appropriate suboptions easily into insert a relay agent option with appropriate suboptions easily into
DHCP DISCOVER messages. Once the lease has been granted, however, DHCP DISCOVER messages. Once the lease has been granted, however,
future DHCP RENEWAL messages are sent directly to the DHCP Server as future DHCP RENEWAL messages are sent directly to the DHCP Server as
specified in the Server-ID option. This means that the relay may not specified in the Server-ID option. This means that the relay may not
see the DHCP RENEWAL messages (depending upon network topology) and see the DHCP RENEWAL messages (depending upon network topology) and
thus can not provide the same relay agent option information in the thus can not provide the same relay agent option information in the
RENEWAL messages. RENEWAL messages.
skipping to change at page 2, line 46 skipping to change at page 4, line 5
REBINDING. REBINDING.
This new suboption could also be used by the DHCP relay in order to This new suboption could also be used by the DHCP relay in order to
allow the relay to appear as the actual DHCP server to the client. allow the relay to appear as the actual DHCP server to the client.
This has the advantage that the relay can more easily keep up-to-date This has the advantage that the relay can more easily keep up-to-date
information about leases granted, etc. information about leases granted, etc.
In short, this new suboption allows the DHCPv4 relay to function in In short, this new suboption allows the DHCPv4 relay to function in
the same fashion as the DHCPv6 relay currently does. the same fashion as the DHCPv6 relay currently does.
1.1 Conventions 2. Server-ID Override Suboption Definition
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 [1].
2.0 Server-ID Override Suboption Definition
The format of the suboption is: The format of the suboption is:
Code Len Overridden Server-ID address Code Len Overriding Server-ID address
+-----+-----+-----+-----+-----+-----+ +-----+-----+-----+-----+-----+-----+
| TBD | n | a1 | a2 | a3 | a4 | | TBD | n | a1 | a2 | a3 | a4 |
+-----+-----+-----+-----+-----+-----+ +-----+-----+-----+-----+-----+-----+
Figure 1
The option length (n) is 4. The octets "a1" through "a4" specify the The option length (n) is 4. The octets "a1" through "a4" specify the
value which SHOULD be inserted into the Server-ID option by the DHCP value which SHOULD be inserted into the Server-ID option by the DHCP
Server upon reply. Server upon reply.
DHCP Servers SHOULD use this value, if present, as the value to DHCP Servers SHOULD use this value, if present, as the value to
insert into the Server-ID option whenever responding to a DHCP insert into the Server-ID option whenever responding to a DHCP
Client. Client.
When servicing a DHCP REQUEST packet the DHCP Server would normally When servicing a DHCP REQUEST packet the DHCP Server would normally
look at the Server-ID option for verification that the address look at the Server-ID option for verification that the address
specified there is one of the addresses associated with the DHCP specified there is one of the addresses associated with the DHCP
Server, silently ignoring the REQUEST if it does not match a Server, silently ignoring the REQUEST if it does not match a
configured DHCP Server interface address. If the REQUEST packet configured DHCP Server interface address. If the REQUEST packet
contains a Server-ID Override Suboption, however, comparison should contains a Server-ID Override Suboption, however, comparison should
be made between this suboption and the Server-ID option. If both of be made between this suboption and the Server-ID option. If both of
the Server-ID Override Suboption and the Server-ID Option specify the the Server-ID Override Suboption and the Server-ID Option specify the
same address, then the Server should accept the REQUEST packet for same address, then the Server should accept the REQUEST packet for
processing, regardless of whether or not the Server-ID Option matchs processing, regardless of whether or not the Server-ID Option matchs
a DHCP Server interface. a DHCP Server interface.
3.0 IANA Considerations 3. Security Considerations
None.
4.0 Acknowledgements
This document is the result of work done within Cisco Systems.
Thanks to Jay Kumarasamy, Kim Kinnear, and Mark Stapp for their work
on this suboption definition and the other related work for which
this is necessary.
5.0 Security Considerations
Message authentication in DHCP for intradomain use where the out-of- Message authentication in DHCP for intradomain use where the out-of-
band exchange of a shared secret is feasible is defined in RFC 3118 band exchange of a shared secret is feasible is defined in [3].
[5]. Potential exposures to attack are discussed in section 7 of the Potential exposures to attack are discussed in section 7 of the DHCP
DHCP protocol specification in RFC 2131 [2]. protocol specification in [2].
The DHCP Relay Agent option depends on a trusted relationship between The DHCP Relay Agent option depends on a trusted relationship between
the DHCP relay agent and the server, as described in section 5 of RFC the DHCP relay agent and the server, as described in section 5 of RFC
3046. While the introduction of fraudulent relay-agent options can 3046. While the introduction of fraudulent relay-agent options can
be prevented by a perimeter defense that blocks these options unless be prevented by a perimeter defense that blocks these options unless
the relay agent is trusted, a deeper defense using the authentication the relay agent is trusted, a deeper defense using the authentication
option for relay agent options [4] SHOULD be deployed as well. option for relay agent options [4] SHOULD be deployed as well.
If a rogue DHCP relay were inserted between the client and the If a rogue DHCP relay were inserted between the client and the
server, it could redirect clients to it using this suboption. This server, it could redirect clients to it using this suboption. This
would allow such a system to later deny renew requests and thus force would allow such a system to later deny renew requests and thus force
clients to discontinue use of their allocated address. This clients to discontinue use of their allocated address. This
interception, however, would need to be done during the initial interception, however, would need to be done during the initial
DISCOVER and OFFER phase, since the suboption value SHOULD be ignored DISCOVER and OFFER phase, since the suboption value SHOULD be ignored
by the server during RENEWAL state. Either DHCP Authentication [5] by the server during RENEWAL state. Either DHCP Authentication [3]
or DHCP Relay Agent option authentication [4] would address this or DHCP Relay Agent option authentication [4] would address this
case. case.
6.0 Intellectual Property Rights and Copyright 4. IANA Considerations
None.
5. Intellectual Property Rights and Copyright
The IETF has been notified of intellectual property rights claimed in The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this regard to some or all of the specification contained in this
document. For more information consult the online list of claimed document. For more information consult the online list of claimed
rights. rights.
Copyright (C) The Internet Society (2004). This document is subject Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights." except as set forth therein, the authors retain all their rights."
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
References 6. 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, BCP 14, March 1997. Levels", RFC 2119, BCP 14, March 1997.
[2] Droms, R. "Dynamic Host Configuration Protocol", RFC 2131, [2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997. March 1997.
[3] Alexander, S. and Droms, R., "DHCP Options and BOOTP Vendor [3] Droms, R., "Authentication for DHCP Messages", RFC 3118,
Extensions", RFC 2132, March 1997. June 2001.
[4] Stapp, M. "The Authentication Suboption for the DHCP [4] Stapp, M., "The Authentication Suboption for the DHCP Relay
Relay Agent Option", draft-ietf-dhc-auth-suboption-00.txt, Agent Option", RFC 4030, March 2005.
June 23, 2002
[5] Droms, R. "Authentication for DHCP Messages", RFC 3118, [5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
June 2001 Considerations Section in RFCs", RFC 2434, October 1998.
[6] Patrick, M., "DHCP Relay Agent Information Option", [6] Patrick, M., "DHCP Relay Agent Information Option", RFC 3096,
RFC 3046, January 2001 November 2004.
Author Information: Authors' Addresses
Richard Johnson Richard A. Johnson
Jay Kumarasamy Cisco Systems, Inc.
Cisco Systems
170 W. Tasman Dr. 170 W. Tasman Dr.
San Jose, CA 95134 San Jose, CA 95134
US
Phone: (408) 526-4000 Phone: +1 408 526 4000
Email: raj@cisco.com
EMail: jayk@cisco.com Jay Kumarasamy
raj@cisco.com Cisco Systems, Inc.
170 W. Tasman Dr.
San Jose, CA 95134
US
Phone: +1 408 526 4000
Email: jayk@cisco.com
Kim Kinnear Kim Kinnear
Cisco Systems, Inc.
170 W. Tasman Dr.
San Jose, CA 95134
US
Phone: +1 408 526 4000
Email: kkinnear@cisco.com
Mark Stapp Mark Stapp
Cisco Systems Cisco Systems, Inc.
250 Apollo Drive 170 W. Tasman Dr.
Chelmsford, MA 01824 San Jose, CA 95134
US
Phone: (978) 244-8000 Phone: +1 408 526 4000
Email: mjs@cisco.com
EMail: kkinnear@cisco.com Intellectual Property Statement
mjs@cisco.com
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
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 (2005). 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.
 End of changes. 

This html diff was produced by rfcdiff 1.24, available from http://www.levkowetz.com/ietf/tools/rfcdiff/