draft-ietf-dhc-stateless-dhcpv6-renumbering-02.txt   rfc4076.txt 
Dynamic Host Congiguration T. Chown
Internet-Draft University of Southampton Network Working Group T. Chown
Expires: April 25, 2005 S. Venaas Request for Comments: 4076 University of Southampton
Category: Informational S. Venaas
UNINETT UNINETT
A. Vijayabhaskar A. Vijayabhaskar
Cisco Systems (India) Private Cisco Systems (India) Private Limited
Limited May 2005
October 25, 2004
Renumbering Requirements for Stateless DHCPv6
draft-ietf-dhc-stateless-dhcpv6-renumbering-02
Status of this Memo
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance with
RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at Renumbering Requirements for Stateless
http://www.ietf.org/ietf/1id-abstracts.txt. Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
The list of Internet-Draft Shadow Directories can be accessed at Status of This Memo
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 25, 2005. This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2005).
Abstract Abstract
IPv6 hosts using Stateless Address Autoconfiguration are able to IPv6 hosts using Stateless Address Autoconfiguration are able to
automatically configure their IPv6 address and default router configure their IPv6 address and default router settings
settings. However, further settings are not available. If such automatically. However, further settings are not available. If
hosts wish to automatically configure their DNS, NTP or other these hosts wish to configure their DNS, NTP, or other specific
specific settings the stateless variant of the Dynamic Host settings automatically, the stateless variant of the Dynamic Host
Configuration Protocol for IPv6 (DHCPv6) could be used. This Configuration Protocol for IPv6 (DHCPv6) could be used. This
combination of Stateless Address Autoconfiguration and stateless combination of Stateless Address Autoconfiguration and stateless
DHCPv6 could be used quite commonly in IPv6 networks. However, hosts DHCPv6 could be used quite commonly in IPv6 networks. However, hosts
using such a combination currently have no means by which to be using this combination currently have no means by which to be
informed of changes in stateless DHCPv6 option settings, e.g. the informed of changes in stateless DHCPv6 option settings; e.g., the
addition of a new NTP server address, a change in DNS search paths, addition of a new NTP server address, a change in DNS search paths,
or full site renumbering. This document is presented as a problem or full site renumbering. This document is presented as a problem
statement from which a solution should be proposed in a subsequent statement from which a solution should be proposed in a subsequent
document. document.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ...................................................2
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement ..............................................3
3. Renumbering Scenarios . . . . . . . . . . . . . . . . . . . . 4 3. Renumbering Scenarios ..........................................3
3.1 Site renumbering . . . . . . . . . . . . . . . . . . . . . 4 3.1. Site Renumbering .........................................4
3.2 Changes to a DHCPv6-assigned setting . . . . . . . . . . . 4 3.2. Changes to a DHCPv6-assigned Setting .....................4
4. Renumbering Requirements . . . . . . . . . . . . . . . . . . . 4 4. Renumbering Requirements .......................................4
5. Considerations in choosing a solution . . . . . . . . . . . . 5 5. Considerations in Choosing a Solution ..........................4
6. Solution Space . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Solution Space .................................................5
7. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Summary ........................................................5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. Security Considerations ........................................6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 9. Acknowledgements ...............................................6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10. References .....................................................6
10.1 Normative References . . . . . . . . . . . . . . . . . . . . 6 10.1. Normative References .....................................6
10.2 Informative References . . . . . . . . . . . . . . . . . . . 7 10.2. Informative References ...................................6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . 8
1. Introduction 1. Introduction
IPv6 hosts using Stateless Address Autoconfiguration [1] are able to IPv6 hosts using Stateless Address Autoconfiguration [2] are able to
automatically configure their IPv6 address and default router configure their IPv6 address and default router settings
settings. While Stateless Address Autoconfiguration for IPv6 allows automatically. Although Stateless Address Autoconfiguration for IPv6
automatic configuration of these settings, it does not provide a allows automatic configuration of these settings, it does not provide
mechanism for additional, non IP-address settings to be automatically a mechanism for additional non IP-address settings to be configured
configured. automatically.
The full version of the Dynamic Host Configuration Protocol for IPv6 The full version of the Dynamic Host Configuration Protocol for IPv6
(DHCPv6) [2] is designed to provide both stateful address assignment (DHCPv6) [3] is designed to provide both stateful address assignment
to IPv6 hosts, as well as additional (non IP-address) configuration to IPv6 hosts, as well as additional (non IP-address) configuration
including DNS, NTP and other specific settings. A full stateful including DNS, NTP, and other specific settings. A full stateful
DHCPv6 server allocates the addresses and maintains the clients DHCPv6 server allocates the addresses and maintains the clients'
bindings to keep track of client leases. bindings to keep track of client leases.
If hosts using Stateless Address Autoconfiguration for IPv6 wish to If hosts using Stateless Address Autoconfiguration for IPv6 wish to
automatically configure their DNS, NTP or other specific settings the configure their DNS, NTP, or other specific settings automatically,
stateless variant [3] of DHCPv6 could be used. The stateless variant the stateless variant [4] of DHCPv6 could be used. This variant is
of DHCPv6 is more lightweight. It does not do address assignment, more lightweight. It does not do address assignment; instead, it
instead it only provides additional configuration parameters like DNS only provides additional configuration parameters, such as DNS
resolver addresses. It does not maintain state about the information resolver addresses. It does not maintain dynamic state about the
assigned to clients, hence there is no need to maintain per-client information assigned to clients, and therefore there is no need to
state on the server. In other words, all clients can be given the maintain dynamic per-client state on the server.
same information, in the same way that the information in Router
Advertisements is not client-specific.
This combination of Stateless Address Autoconfiguration and stateless This combination of Stateless Address Autoconfiguration and stateless
DHCPv6 could be used quite commonly in IPv6 networks. DHCPv6 could be used quite commonly in IPv6 networks.
2. Problem Statement 2. Problem Statement
A problem however lies in the ability, or lack of ability, of clients A problem, however, lies in the ability, or lack of ability, of
using this combination to be informed of (or to deduce) changes in clients using this combination to be informed of (or to deduce)
DHCPv6 assigned settings. changes in DHCPv6-assigned settings.
While a DHCPv6 server unicasts Reconfigure message to individual While a DHCPv6 server unicasts Reconfigure messages to individual
clients to trigger the clients to intiate Information-request/reply clients to trigger them to initiate Information-request/reply
configuration exchanges to update their configuration settings, the configuration exchanges to update their configuration settings, the
stateless variant of DHCPv6 cannot use the Reconfigure mechanism stateless variant of DHCPv6 cannot use the Reconfigure mechanism
because it does not maintain a list of IP addresses (leases) to send because it does not maintain a list of IP addresses (leases) to send
the unicast messages to. Note that in DHCPv6, Reconfigure messages the unicast messages to. Note that in DHCPv6, Reconfigure messages
must be unicast; multicast is not allowed. must be unicast; multicast is not allowed.
Thus events including the following cannot be handled: Thus, events including the following cannot be handled:
o Full site renumbering o Full site renumbering
o DNS server change of address o DNS server change of address
o NTP server change of address o NTP server change of address
o A change in DNS search paths o A change in DNS search paths
It would be highly desirable that a host using the combination of It would be highly desirable that a host using the combination of
Stateless Address Autoconfiguration and stateless DHCPv6 could handle Stateless Address Autoconfiguration and stateless DHCPv6 could handle
a renumbering or reconfiguration event, whether planned or unplanned a renumbering or reconfiguration event, whether planned or unplanned
by the network administrator. by the network administrator.
skipping to change at page 4, line 15 skipping to change at page 3, line 34
o NTP server change of address o NTP server change of address
o A change in DNS search paths o A change in DNS search paths
It would be highly desirable that a host using the combination of It would be highly desirable that a host using the combination of
Stateless Address Autoconfiguration and stateless DHCPv6 could handle Stateless Address Autoconfiguration and stateless DHCPv6 could handle
a renumbering or reconfiguration event, whether planned or unplanned a renumbering or reconfiguration event, whether planned or unplanned
by the network administrator. by the network administrator.
Note that the scope of the problem can also be seen to extend beyond Note that the scope of the problem could extend beyond Stateless
Stateless DHCPv6, since only IP address options have a lifetime, i.e. DHCPv6, since only IP address options have a lifetime; i.e., there is
there is no mechanism even in the full DHCPv6 to "expire" old no mechanism even in the full DHCPv6 that "expires" old information
information or otherwise force a client to recheck that new/updated or otherwise forces a client to recheck that new/updated information
information is available. However, with full DHCPv6, a node may is available. However, with full DHCPv6, a node may learn of updates
learn of updates to non-address options when renewing its address to non-address options when renewing its address lease.
lease.
3. Renumbering Scenarios 3. Renumbering Scenarios
There are two main scenarios for changes to DHCPv6-assigned settings, There are two main scenarios for changes to DHCPv6-assigned settings
that would require the client to initiate an Information-request/ that would require the client to initiate an Information-request/
reply exchange to update the configuration. reply exchange to update the configuration.
3.1 Site renumbering 3.1. Site Renumbering
One of the fundamental principles of IPv6 is that sites receive their One of the fundamental principles of IPv6 is that sites receive their
IPv6 address allocations from an ISP using provider assigned (PA) IPv6 address allocations from an ISP using provider-assigned (PA)
address space. There is currently no provider independent (PI) address space. There is currently no provider-independent (PI)
address space in IPv6. A site changing its ISP must thus renumber address space in IPv6. Therefore, a site changing its ISP must
its network. Any such site renumbering will require hosts to renumber its network. Any such site renumbering will require hosts
reconfigure both their own address and default router settings as to reconfigure both their own address and default router settings and
well as their stateless DHCPv6-assigned settings. their stateless DHCPv6-assigned settings.
3.2 Changes to a DHCPv6-assigned setting 3.2. Changes to a DHCPv6-assigned Setting
An administrator may need to change one or more stateless An administrator may need to change one or more stateless
DHCPv6-assigned settings, e.g. an NTP server, DNS server, or the DNS DHCPv6-assigned settings; e.g., an NTP server, DNS server, or the DNS
search path. This may be required if a new, additional DNS server is search path. This may be required if a new, additional DNS server is
brought online, is moved to a new network (prefix), or an existing brought online and is moved to a new network (prefix), or if an
server is decommissioned or known to be unavailable. existing server is decommissioned or known to be unavailable.
4. Renumbering Requirements 4. Renumbering Requirements
Ideally, any of the above scenarios should be handled automatically Ideally, any of the above scenarios should be handled automatically
by the hosts on the network. For this to be realised, a method is by the hosts on the network. For this to be realised, a method is
required for the hosts to be informed that they should request new required whereby the hosts are informed that they should request new
stateless DHCPv6-assigned setting information. stateless DHCPv6-assigned setting information.
The solution to the problem may depend on whether the renumbering or The solution to the problem may depend on whether the renumbering or
configuration change is a planned or unplanned one, from the configuration change is planned or unplanned, from the perspective of
perspective of the network administrator. There is already work the network administrator. There is already work underway toward
underway in understanding the planned renumbering [4] scenario for understanding the planned renumbering [5] scenario for IPv6 networks.
IPv6 networks. However, there is currently no mechanism in stateless However, there is currently no mechanism in stateless DHCPv6 for
DHCPv6 to even handle planned renumbering events. handling planned renumbering events.
5. Considerations in choosing a solution 5. Considerations in Choosing a Solution
There are a number of considerations that could be listed for a A number of considerations could be listed for a desirable solution:
desirable solution:
o The solution should support planned renumbering; it is desirable o The solution should support planned renumbering; it is desirable
that it also supports unplanned renumbering. that it also supports unplanned renumbering.
o Security is important. No new security concerns should be o Security is important. No new security concerns should be
introduced to Stateless DHCPv6 by the solution. introduced to Stateless DHCPv6 by the solution.
o It must be possible to update options even if the network is not o It must be possible to update options, even if the network is not
renumbered. renumbered.
o It is desirable to maintain the "stateless" property; i.e., no o It is desirable to maintain the "stateless" property; i.e., no
per-client state should need to be kept in the server. per-client state should need to be kept in the server.
6. Solution Space 6. Solution Space
Solutions should be designed and presented in a separate document. Solutions should be designed and presented in a separate document.
An initial, brief set of candidate solutions might include: An initial brief set of candidate solutions might include the
following:
o Adding a Reconfigure message mechanism that would work in the o Add a Reconfigure message mechanism that would work in the
stateless DHCPv6 environment. This could enable planned or stateless DHCPv6 environment. This could enable planned or
unplanned events, but may require a multicast mechanism to be unplanned events, but may require a multicast mechanism in order
realised. to be realised.
o Conveying a valid lifetime timer to clients for stateless o Convey a valid lifetime timer to clients for stateless DHCPv6-
DHCPv6-assigned settings. This could primarily enable planned assigned settings. This could primarily enable planned events,
events, but with a small time-out it could to some extent handle but with a small time-out it could handle unplanned events to some
unplanned events at the expense of the additional request traffic. extent at the expense of the additional request traffic. The
The selection of recommended lifetime values/ranges would be the selection of recommended lifetime values/ranges would be the
subject of future work. subject of future work.
o Using some form of Router Advertisement as a hint to request new o Use some form of Router Advertisement (RA) [1] as a hint to
stateless DHCPv6-assigned settings. Using only an observed new request new stateless DHCPv6-assigned settings. Using only an
Router Advertisement prefix as a hint to re-request settings would observed new RA prefix as a hint to re-request settings would not
not handle changes that are purely to NTP, DNS or other options. handle changes that are purely to NTP, DNS, or other options.
Other possible means of detection of network (re)attachment could Other possible means of detection of network (re)attachment could
also be used as cues (e.g. see IPv6 DNA Goals [5]). also be used as cues (e.g., see Goals of Detecting Network
Attachment (DNA) in IPv6 [6]).
o Changing semantics of the DHCPv6 'O' flag such that toggling its o Change the semantics of the 'O' flag in RAs [2] so that toggling
value may trigger an Information-request message. its value may trigger an Information-request message.
There will also be conditions under which a client should also send There will also be conditions under which a client should send an
an Information-request, such as reconnection to a link. Such Information-request, such as reconnection to a link. Recommendations
specific recommendations are outside the scope of this document but for these cases are outside the scope of this document, but we expect
we expect ongoing work in the Detecting Network Attachment (DNA) WG ongoing work in the DNA WG (as scoped in Goals of Detecting Network
(as scoped in IPv6 DNA Goals [5]) to yield recommendations. Attachment (DNA) in IPv6 [6]) to yield recommendations.
7. Summary 7. Summary
This document presents a problem statement for how IPv6 hosts that This document presents a problem statement for how IPv6 hosts that
use the combination of Stateless Address Autoconfiguration and use the combination of Stateless Address Autoconfiguration and
stateless DHCPv6 may be informed of renumbering events or other stateless DHCPv6 may be informed of renumbering events or other
changes to the settings that they originally learnt through stateless changes to the settings that they originally learned through
DHCPv6. A short list of candidate solutions is presented, which the stateless DHCPv6. A short list of candidate solutions is presented,
authors hope may be expanded upon in subsequent documents. which the authors hope will be expanded upon in subsequent documents.
8. Security Considerations 8. Security Considerations
There are no security considerations in this problem statemement per There are no security considerations in this problem statement per
se. However, whatever mechanism is designed or chosen to address se. However, whatever mechanism is designed or chosen to address
this problem should avoid the introduction of new security concerns this problem should avoid introducing new security concerns for
for (stateless) DHCPv6. (stateless) DHCPv6.
The issues of maintaining appropriate security through a renumbering The issues of maintaining appropriate security through a renumbering
event are outside the scope of this document (in the case where event are outside the scope of this document (if specific servers
specific servers within the network are being added or removed, within the network are being added or removed, firewall
firewall configurations and ACLs, for example, will need to reflect configurations and ACLs, for example, will need to reflect this).
this). However, this is an important area for further work. However, this is an important area for further work.
9. Acknowledgements 9. Acknowledgements
The authors would like to thank Ralph Droms, Bermie Volz and other The authors would like to thank Ralph Droms, Bernie Volz, and other
individuals on the DHC mail list for their comments on this draft, as individuals on the DHC mail list for their comments on this document,
well as colleagues on the 6NET project. We also thank the review as well as colleagues on the 6NET project. We also thank the review
comments, particularly those from Thomas Narten. comments, particularly those from Thomas Narten.
10. References 10. References
10.1 Normative References 10.1. Normative References
[1] Thomson, S. and T. Narten, "IPv6 Stateless Address [1] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998.
[2] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998. Autoconfiguration", RFC 2462, December 1998.
[2] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and M. [3] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 3315, July 2003. RFC 3315, July 2003.
[3] Droms, R., "Stateless Dynamic Host Configuration Protocol (DHCP) [4] Droms, R., "Stateless Dynamic Host Configuration Protocol (DHCP)
Service for IPv6", RFC 3736, April 2004. Service for IPv6", RFC 3736, April 2004.
10.2 Informative References 10.2. Informative References
[4] Baker, F., Lear, E. and R. Droms, "Procedures for Renumbering an [5] Baker, F., Lear, E. and R. Droms, "Procedures for Renumbering an
IPv6 Network without a Flag Day", IPv6 Network without a Flag Day", Work in Progress, July 2004.
draft-ietf-v6ops-renumbering-procedure-01 (work in progress),
July 2004.
[5] Choi, J., "Detecting Network Attachment in IPv6 Goals", [6] Choi, J., "Goals of Detecting Network Attachment (DNA) in IPv6",
draft-ietf-dna-goals-03 (work in progress), October 2004. Work in Progress, October 2004.
Authors' Addresses Authors' Addresses
Tim Chown Tim Chown
University of Southampton University of Southampton
School of Electronics and Computer Science School of Electronics and Computer Science
Southampton, Hampshire SO17 1BJ Southampton, Hampshire SO17 1BJ
United Kingdom United Kingdom
EMail: tjc@ecs.soton.ac.uk EMail: tjc@ecs.soton.ac.uk
skipping to change at page 8, line 5 skipping to change at page 8, line 5
EMail: venaas@uninett.no EMail: venaas@uninett.no
Vijayabhaskar A Kalusivalingam Vijayabhaskar A Kalusivalingam
Cisco Systems (India) Private Limited Cisco Systems (India) Private Limited
9, Brunton Road 9, Brunton Road
Bangalore 560025 Bangalore 560025
India India
EMail: vibhaska@cisco.com EMail: vibhaska@cisco.com
Intellectual Property Statement Full 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.
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.
Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights 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 might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an 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 attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at ietf-
ietf-ipr@ietf.org. 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 (2004). 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 Acknowledgement
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
 End of changes. 

This html diff was produced by rfcdiff 1.25, available from http://www.levkowetz.com/ietf/tools/rfcdiff/