draft-ietf-dhc-stateless-dhcpv6-renumbering-01.txt   draft-ietf-dhc-stateless-dhcpv6-renumbering-02.txt 
Dynamic Host Congiguration T. Chown Dynamic Host Congiguration T. Chown
Internet-Draft University of Southampton Internet-Draft University of Southampton
Expires: August 30, 2004 S. Venaas Expires: April 25, 2005 S. Venaas
UNINETT UNINETT
A. Vijayabhaskar A. Vijayabhaskar
Hewlett-Packard STSD-I Cisco Systems (India) Private
March 2004 Limited
October 25, 2004
Renumbering Requirements for Stateless DHCPv6 Renumbering Requirements for Stateless DHCPv6
draft-ietf-dhc-stateless-dhcpv6-renumbering-01 draft-ietf-dhc-stateless-dhcpv6-renumbering-02
Status of this Memo Status of this Memo
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed, 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 and any of which I become aware will be disclosed, in accordance with
RFC 3668. RFC 3668.
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
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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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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on August 30, 2004. This Internet-Draft will expire on April 25, 2005.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2004). All Rights Reserved.
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 automatically configure their IPv6 address and default router
settings. However, further settings are not available. If such settings. However, further settings are not available. If such
hosts wish to automatically configure their DNS, NTP or other hosts wish to automatically configure their DNS, NTP or other
specific settings the stateless variant of the Dynamic Host specific settings 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 such a 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, changes in DNS search paths, or addition of a new NTP server address, a change in DNS search paths,
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 . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
3. Renumbering Scenarios . . . . . . . . . . . . . . . . . . . . 4 3. Renumbering Scenarios . . . . . . . . . . . . . . . . . . . . 4
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 . . . . . . . . . . . . 5
6. Solution Space . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Solution Space . . . . . . . . . . . . . . . . . . . . . . . . 5
7. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. Security Considerations . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
10. Normative References . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1 Normative References . . . . . . . . . . . . . . . . . . . . 6
10.2 Informative References . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . 8 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 [1] are able to
automatically configure their IPv6 address and default router automatically configure their IPv6 address and default router
settings. While Stateless Address Autoconfiguration for IPv6 allows settings. While Stateless Address Autoconfiguration for IPv6 allows
automatic configuration of these settings, it does not provide a automatic configuration of these settings, it does not provide a
mechanism for additional, non IP-address settings to be automatically mechanism for additional, non IP-address settings to be automatically
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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 automatically configure their DNS, NTP or other specific settings the
stateless variant [3] of DHCPv6 could be used. The stateless variant stateless variant [3] of DHCPv6 could be used. The stateless variant
of DHCPv6 is more lightweight. It does not do address assignment, of DHCPv6 is more lightweight. It does not do address assignment,
instead it only provides additional configuration parameters like DNS instead it only provides additional configuration parameters like DNS
resolver addresses. It does not maintain state about the information resolver addresses. It does not maintain state about the information
assigned to clients; the additional parameters do not have an assigned to clients, hence there is no need to maintain per-client
explicit life-time associated with them in the same way that IP state on the server. In other words, all clients can be given the
addresses do, and hence the DHCPv6 server does not need to maintain same information, in the same way that the information in Router
the state of the clients. 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. In the absence DHCPv6 could be used quite commonly in IPv6 networks.
of an alternative method for DNS, NTP and other options to be
automatically configured, it may become the most common combination
for statelessly configuring hosts.
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 clients
using this combination to be informed of (or to deduce) changes in using this combination to be informed of (or to deduce) changes in
DHCPv6 assigned settings. DHCPv6 assigned settings.
While a DHCPv6 server unicasts Reconfigure message to individual While a DHCPv6 server unicasts Reconfigure message to individual
clients to trigger the clients to intiate Information-request/reply clients to trigger the clients to intiate 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. the unicast messages to. Note that in DHCPv6, Reconfigure messages
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 Changes 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
Stateless DHCPv6, since only IP address options have a lifetime, i.e.
there is no mechanism even in the full DHCPv6 to "expire" old
information or otherwise force a client to recheck that new/updated
information is available. However, with full DHCPv6, a node may
learn of updates to non-address options when renewing its address
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 wishing to change ISP must thus address space in IPv6. A site changing its ISP must thus renumber
renumber its network. Any such site renumbering will require hosts its network. Any such site renumbering will require hosts to
to reconfigure both their own address and default router settings as reconfigure both their own address and default router settings as
well as their stateless DHCPv6-assigned settings. well as 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, is moved to a new network (prefix), or an existing
server is decommissioned or known to be unavailable. server is decommissioned or known to be unavailable.
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required for the hosts to be informed that they should request new required for the hosts to be 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 a planned or unplanned one, from the
perspective of the network administrator. There is already work perspective of the network administrator. There is already work
underway in understanding the planned renumbering [4] scenario for underway in understanding the planned renumbering [4] scenario for
IPv6 networks. However, there is currently no mechanism in stateless IPv6 networks. However, there is currently no mechanism in stateless
DHCPv6 to even handle planned renumbering events. DHCPv6 to even handle planned renumbering events.
The unplanned renumbering event, which may be more common in smaller,
unmanaged networks, is more difficult to cater for. Ideally, any
solution for the problem should consider planned and unplanned
events.
The solution should also be secure, such that additional security
concerns are not added to the stateless DHCPv6 networking
environment.
5. Considerations in choosing a solution 5. Considerations in choosing a solution
There are a number of considerations that could be listed for a There are a number of considerations that could be listed for a
desirable solution: desirable solution:
o It should support planned renumbering; it is desirable to support o The solution should support planned renumbering; it is desirable
unplanned renumbering. that it also supports unplanned renumbering.
o Security is important; e.g., avoiding denialof service attacks o Security is important. No new security concerns should be
mounted through Reconfigure messages sent from an attacker. 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.
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o Adding a Reconfigure message mechanism that would work in the o Adding 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 to be
realised. realised.
o Conveying a valid lifetime timer to clients for stateless o Conveying a valid lifetime timer to clients for stateless
DHCPv6-assigned settings. This could primarily enable planned DHCPv6-assigned settings. This could primarily enable planned
events, but with a small time-out it could to some extent handle events, but with a small time-out it could to some extent handle
unplanned events at the expense of the additional request traffic. unplanned events at the expense of the additional request traffic.
The selection of recommended lifetime values/ranges would be the
subject of future work.
o Using some form of Router Advertisement as a hint to request new o Using some form of Router Advertisement as a hint to request new
stateless DHCPv6-assigned settings. Using only an observed new stateless DHCPv6-assigned settings. Using only an observed new
Router Advertisement prefix as a hint to re-request settings would Router Advertisement prefix as a hint to re-request settings would
not handle changes that are purely to NTP, DNS or other options. not 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 IPv6 DNA Goals [5]).
o Changing semantics of the DHCPv6 'O' flag such that toggling its o Changing semantics of the DHCPv6 'O' flag such that toggling its
value may trigger an Information-request message. value may trigger an Information-request message.
There will also be conditions under which a client should also send
an Information-request, such as reconnection to a link. Such
specific recommendations are outside the scope of this document but
we expect ongoing work in the Detecting Network Attachment (DNA) WG
(as scoped in IPv6 DNA Goals [5]) 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 learnt through stateless
DHCPv6. A short list of candidate solutions is presented, which the DHCPv6. A short list of candidate solutions is presented, which the
authors hope may be expanded upon in subsequent documents. authors hope may 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 statemement 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 the introduction of new security concerns
for (stateless) DHCPv6. for (stateless) DHCPv6.
The issues of maintaining appropriate security through a renumbering
event are outside the scope of this document (in the case where
specific servers within the network are being added or removed,
firewall configurations and ACLs, for example, will need to reflect
this). However, this is an important area for further work.
9. Acknowledgements 9. Acknowledgements
The authors would like to thank Ralph Droms and Bermie Volz for their The authors would like to thank Ralph Droms, Bermie Volz and other
comments on this draft. individuals on the DHC mail list for their comments on this draft, as
well as colleagues on the 6NET project. We also thank the review
comments, particularly those from Thomas Narten.
10 Normative References 10. References
10.1 Normative References
[1] Thomson, S. and T. Narten, "IPv6 Stateless Address [1] 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. [2] 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) [3] 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
[4] Baker, F., Lear, E. and R. Droms, "Procedures for Renumbering an [4] Baker, F., Lear, E. and R. Droms, "Procedures for Renumbering an
IPv6 Network without a Flag Day", IPv6 Network without a Flag Day",
draft-baker-ipv6-renumber-procedure-01 (work in progress), draft-ietf-v6ops-renumbering-procedure-01 (work in progress),
October 2003. July 2004.
[5] Choi, J., "Detecting Network Attachment in IPv6 Goals", [5] Choi, J., "Detecting Network Attachment in IPv6 Goals",
draft-ietf-dna-goals-00 (work in progress), June 2004. draft-ietf-dna-goals-03 (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
Stig Venaas Stig Venaas
UNINETT UNINETT
Trondheim NO 7465 Trondheim NO 7465
Norway Norway
EMail: venaas@uninett.no EMail: venaas@uninett.no
Vijayabhaskar A K Vijayabhaskar A Kalusivalingam
Hewlett-Packard STSD-I Cisco Systems (India) Private Limited
29, Cunningham Road 9, Brunton Road
Bangalore 560052 Bangalore 560025
India India
EMail: vijayak@india.hp.com EMail: vibhaska@cisco.com
Intellectual Property Statement Intellectual Property Statement
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
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