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Versions: (draft-jjmb-dhc-dhcpv6-redundancy-consider) 00 01 02 03 RFC 6853

Dynamic Host Configuration (DHC)                           J. Brzozowski
Internet-Draft                              Comcast Cable Communications
Intended status: BCP                                         J. Tremblay
Expires: February 13, 2012                                Videotron Ltd.
                                                                 J. Chen
                                                       Time Warner Cable
                                                            T. Mrugalski
                                                                     ISC
                                                         August 12, 2011


              DHCPv6 Redundancy Deployment Considerations
              draft-ietf-dhc-dhcpv6-redundancy-consider-01

Abstract

   This document documents some deployment considerations for those who
   wishing to use DHCPv6 to support their deployment of IPv6.
   Specifically, providing semi-redundant DHCPv6 services is discussed
   in this document.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on February 13, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Scope and Assumptions  . . . . . . . . . . . . . . . . . . . .  3
     2.1.  Service provider model . . . . . . . . . . . . . . . . . .  4
     2.2.  Enterprise model . . . . . . . . . . . . . . . . . . . . .  5
   3.  Protocol requirements  . . . . . . . . . . . . . . . . . . . .  5
     3.1.  DHCPv6 Servers . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  DHCPv6 Relays  . . . . . . . . . . . . . . . . . . . . . .  5
     3.3.  DHCPv6 Clients . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Deployment models  . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Split Prefixes . . . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Multiple Unique Prefixes . . . . . . . . . . . . . . . . .  8
     4.3.  Identical Prefixes . . . . . . . . . . . . . . . . . . . . 10
   5.  Challenges and Issues  . . . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15























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1.  Introduction

   To support the deployment of IPv6 redundancy and high availability
   are required for many if not all components.  This document provides
   information specific to the proposed near term approach for deploying
   semi-redundant DHCPv6 services in advance of DHCPv6 server
   implementations that support a standards based failover or redundancy
   protocol.


2.  Scope and Assumptions

   This document specifies an interim architecture to provide a semi-
   redundant DHCPv6 solution before the availability of vendor or
   standard based solutions.  The proposed architecture may be used in
   wide range of networks, two notable deployment models are discussed:
   service provider and enterprise network environments.  The described
   architecture leverages only existing and implemented DHCPv6
   standards.  This document does not address a standards based solution
   for DHCPv6 redundancy.  In the absence of a standards based DHCPv6
   redundancy protocol and implementation, some analogies are loosely
   drawn with the DHCPv4 failover protocol for reference.  Specific
   discussions related to DHCPv4 failover and redundancy is out of scope
   for this document.  Reader interested in initial work being done in
   DHCPv6 failover is recommended to read
   [I-D.mrugalski-dhc-dhcpv6-failover-requirements].

   Although DHCPv6 redundancy may be useful in a wide range of
   scenarios, they may be generalized for illustration purposes in the
   two aforementioned.  The following assumptions were made with regards
   to the existing DHCPv6 infrastructure, regardless of the model used:

   1.  At least two DHCPv6 servers are used to service to the same
       clients, but the number of servers is not restricted.

   2.  Existing DHCPv6 servers will not directly communicate or interact
       with one another in the assignment of IPv6 addresses and
       configuration information to requesting clients.

   3.  DHCPv6 clients are instructed to run stateful DHCPv6 to request
       at least one IPv6 address.  Configuration information and other
       options like a delegated IPv6 prefix may be also requested.

   4.  Clients requesting IPv6 addresses, prefixes, and or options care
       of DHCPv6 must recognize and honor the DHCPv6 preference option.
       Furthermore, the requesting clients must process DHCPv6 ADVERTISE
       messages per [RFC3315] when the preference option is present.




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   5.  DHCPv6 server failure does not imply failure of any other network
       service or protocol, e.g.  TFTP servers.  Redundancy of any
       additional services configured by means of DHCPv6 are outside of
       scope of this document.  For example, a single DHCPv6 server may
       configure multiple TFTP servers, with preference for each TFTP
       server, as specified in [RFC5970].

   While techniques described in this document provide some aspects of
   redundancy, it should be noted that complete redundancy will not be
   available until DHCPv6 protocol is standardized.  Initial work toward
   that goal is described in
   [I-D.mrugalski-dhc-dhcpv6-failover-requirements].

2.1.  Service provider model

   The service provider model represents cases, where end-user devices
   may be configured directly, without any intermediate devices (like
   home routers used in service provider model).  DHCPv6 clients include
   cable modems, customer gateways or home routers, and end-user
   devices.  In some cases hosts may be configured directly using the
   service provider DHCPv6 infrastructure or via intermediate router,
   that is in turn being configured by the provider DHCPv6
   infrastructure.  The service provider DHCPv6 infrastructure may be
   semi-redundant in either case.  Cable modems, customer gateways or
   home routers, and end-user devices are commonly referred to as CPE
   (Customer Premises Equipment).  The following additional assumptions
   were made, besides the ones made in Section 2:

   1.  The service provider edge routers and access routers (CMTS for
       cable or DSLAM/BRAS for DSL for example) are IPv6 enabled when
       required.

   2.  CPE devices are instructed to perform stateful DHCPv6 to request
       atleast one IPv6 address, delegated prefix, and or configuration
       information.  CPE devices may also be instructed to leverage
       stateless DHCPv6 [RFC3736] to acquire configuration information
       only.  This assumes that IPv6 address and prefix information has
       been acquired using other means.

   3.  The primary application of this BCP is for native IPv6 services.
       Use and applicability to transition mechanisms is out of scope
       for this document.

   4.  CPE devices must implement a stateful DHCPv6 client [RFC3315],
       support for DHCPv6 prefix delegation [RFC3633] or stateless
       DHCPv6 [RFC3736] may also be implemented.





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2.2.  Enterprise model

   The enterprise model represents cases, where end-user devices are
   most often configured directly, without any intermediate devices
   (like home routers used in service provider model).  However,
   enterprise IPv6 environments quite often use or require that DHCPv6
   relay agents are in place to support the use of DHCPv6 for the
   acquisition of IPv6 addresses and or configuration information.  The
   assumptions here extend those that are defined in the beginning of
   Section 2:

   1.  DHCPv6 clients are hosts and are considered end nodes.  Examples
       of such clients include computers, laptops, and possibily mobile
       devices.

   2.  DHCPv6 clients generally do not require the assignment of an IPv6
       prefix delegation and as such do not support DHCPv6 prefix
       delegation [RFC3633].


3.  Protocol requirements

   The following sections outline the requirements that must be
   satisfied by DHCPv6 clients, relays, and servers to ensure the
   desired behavior is provided using pre-existing DHCPv6 server
   implementations as is.  The objective is to provide a semi-redundant
   DHCPv6 service to support the deployment of IPv6 where DHCPv6 is
   required for the assignment of IPv6 addresses, prefixes, and or
   configuration information.

3.1.  DHCPv6 Servers

   This interim architecture requires DHCPv6 servers that are [RFC3315]
   compliant and support the necessary options required to support this
   solution.  Essential to the the use of the interim architecture is
   support for stateful DHCPv6 and the DHCPv6 preference option both
   which are specified in [RFC3315].  For deployment scenarios where
   IPv6 prefix delegation is employed DHCPv6 servers must support DHCPv6
   prefix delegation as defined by [RFC3633].  Further, where stateless
   DHCPv6 is used support for [RFC3736] is required by DHCPv6 servers.

3.2.  DHCPv6 Relays

   There are no specific requirements regarding relays.  However, it is
   implied that DHCPv6 relay agents must be [RFC3315] compliant and must
   support the ability to relay DHCPv6 messages to more than one
   destination minimally.




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3.3.  DHCPv6 Clients

   DHCPv6 clients are required to be compliant to [RFC3315] and support
   the necessary options required to support this solution depending on
   the mode of operations and desired behavior.  Where prefix delegation
   is required DHCPv6 clients will be required to support DHCPv6 prefix
   delegation as defined in [RFC3633].  Clients used with this semi-
   redundant DHCPv6 deployment model must support the acquistion of at
   least one IPv6 address and configuration information using stateful
   DHCPv6 as specified by [RFC3315].  The use of stateless DHCPv6 which
   is also specified in [RFC3315] may also be supported.  DHCPv6 client
   must recognize and adhere to the processing of the advertised DHCPv6
   preference options sent by the DHCPv6 servers.


4.  Deployment models

   At the time of this writing a standards-based DHCPv6 redundancy
   protocol and implementations are not available.  As a result DHCPv6
   server implementations will be used as-is to provide best effort,
   semi-redundant DHCPv6 services.  Behavior of the DHCPv6 services will
   in part be governed by the configuration used by each of the servers.
   Additionally, various aspects of the DHCPv6 protocol [RFC3315] will
   be leveraged to yield the desired behavior.  No inter-server or
   inter-process communications will be used to coordinate DHCPv6 events
   and or activities.  DHCP services for both IPv4 and IPv6 may operate
   simultaneously on the same physical server(s) or may operate on
   different ones.

4.1.  Split Prefixes

   In the split prefixes model, each DHCPv6 server is configured with a
   unique, non-overlapping range derived from the /64 prefix deployed
   for use within an IPv6 network.  Distribution between two servers,
   for example, would require that an allocated /64 be split in two /65
   ranges. 2001:db8:1:0001:0000::/65 and 2001:db8:1:0001:8000::/65 would
   be assigned to each DHCPv6 server for allocation to clients derived
   from 2001:db8:1:0001::/64 prefix.

   Each DHCP server allocates IPv6 addresses from the corresponding
   ranges per device class.  Each DHCPv6 server will be simultaneously
   active and operational.  Address allocation is governed largely
   through the use of the DHCPv6 preference option, so server with
   higher preference value is always prefered.  Additional proprietary
   mechanisms can be leveraged to further enforce the favoring of one
   DHCP server over another.  Example of such scenario is presented in
   Figure 1.




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   It is important to note that over time, it is possible that bindings
   may be disproportionally distributed amongst DHCPv6 servers and not
   any one server will be authoritative for all bindings.  Per
   [RFC3315], a DHCPv6 ADVERTISE messages with a preference option of
   255 is an indicator to a DHCPv6 client to immediately begin a client-
   initiated message exchange by transmitting a REQUEST message.
   Alternatively, a DHCPv6 ADVERTISE messages with a preference option
   of any value lesser than 255 or is absent is an indicator to the
   client that it must wait for subsequent ADVERTISE messages (for a
   specified period of time) before proceeding.  Additionally, in the
   event of a DHCPv6 server failure it is desirable for a server other
   than the server that originally responded to be able to rebind the
   client.  It is not critical, that the DHCPv6 server be able to rebind
   the client in this scenario, however, this is generally desirable
   behavior.  Given the proposed architecture, the remaining active
   DHCPv6 server will have a different range configured making it
   technically incorrect for the same to rebind the client in its
   current state.  Ultimately, when rebinding fails the client will
   acquire a new binding from the configured range unique to an active
   server.  Furthermore, shorter T1, T2, valid, and preferred lifetimes
   can be used to reduce the possibility that a client or some other
   element on the network will experience a disruption in service or
   access to relevant binding data.  The values used for T2, preferred
   and valid lifetime can be adjusted or configured to minimize service
   disruption.  Ideally T2, preferred and valid lifetimes that are equal
   or near equal can be used to trigger a DHCPv6 client to reacquire
   IPv6 address, prefix, and or configuration information almost
   immediately after rebinding fails.  It is important to note that
   shorter values will most certainly create additional load and
   processing for the DHCPv6 server, which must be considered.

   Using a split prefix configuration model dynamic updates to DNS can
   be coordinated to ensure that the DNS is properly updated with
   current binding information.  Challenges arise with regards to the
   update of PTR for IPv6 addresses since the DNS may need to be
   overwritten in a failure condition.  The use of a split prefixes
   enables the differentiation of bindings and binding timing to
   determine which represents the current state.  This becomes
   particularly important when DHCPv6 Leasequery [RFC5007] and/or DHCPv6
   Bulk Leasequery [RFC5460] are leveraged to determine lease or binding
   state.  An additional benefit is that the use of separate ranges per
   DHCPv6 server makes failure conditions more obvious and detectable.









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                 +----------+                 +-----------+
                 | Client 1 +-\            +--+ Server 1  |
                 +----------+  \           |  +-----------+
                                \          |
                                 \         |
                                  \        |
                 +----------+      \       |  +-----------+
                 | Client 2 +--------------+--| Server 2  |
                 +----------+      /       |  +-----------+
                       .          /        .
                       .         /         .
                       .        /          .
                 +----------+  /           .  +-----------+
                 | Client N +-/            .--| n+1 Server|
                 +----------+                 +-----------+

                 Server 1
                 ========
                 Prefix=2001:db8:1:0:0::/64
                 Range=2001:db8:1:0:0::/65
                 Preference=255

                 Server 2
                 ========
                 Prefix=2001:db8:1:0:0::/64
                 Range=2001:db8:1:0:8000::/65
                 Preference=0

                 Server n+1
                 ==========
                 Prefix, range, and preference would
                 vary based on range definition


                         Split prefixes approach.

                                 Figure 1

4.2.  Multiple Unique Prefixes

   In multiple prefix model, each DHCPv6 server is configured with a
   unique, non-overlapping range derived from multiple unique prefixes
   deployed for use within an IPv6 network.  Distribution between two
   servers, for example, would require that a /64 range be configured
   from an allocated from unique /64 prefixes.  For example, the range
   2001:db8:1:0001::/64 would be assigned to a single DHCPv6 server for
   allocation to clients derived from 2001:db8:1:0001::/64 prefix,
   subsequently the 2001:db8:1:0001:1000::/64 from the prefix 2001:db8:



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   1:0001:1000::/64 could be used by a second DHCP server.  This would
   be repeated for each active DHCP server.  Example of this scenario is
   presented in Figure 2.

   This approach uses a unique prefix and ultimately range per DHCPv6
   server with corresponding prefixes configured for use in the network.
   The corresponding network infrastructure must in turn be configured
   to use multiple prefixes on the inteface(s) facing the DHCPv6 client.
   The configuration is similar on all the servers, but a different
   prefix and a different preference is used per DHCPv6 server.

   This approach would drastically increase the rate of consumption of
   IPv6 prefixes and would also yield operational and management
   challenges related to the underlying network since a significantly
   higher number of prefixes would need to be configured and routed.
   This approach also does not provide a clean migration path to the
   desired solution leveraging a standards-based DHCPv6 redundancy or
   failover protocol, which of course has yet to be specified.

   The use of multiple unique prefixes provides benefits similar to
   those referred to in Section 4.1 related to dynamic updates to DNS.
   The use of multiple unique prefixes enables the differentiation of
   bindings and binding timing to determine which represents the current
   state.  This becomes particularly important when DHCPv6 Leasequery
   [RFC5007] and/or DHCPv6 Bulk Leasequery [RFC5460] are leveraged to
   determine lease or binding state.  The use of separate prefixes and
   ranges per DHCPv6 server makes failure conditions more obvious and
   detectable.























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                 +----------+                 +-----------+
                 | Client 1 +-\            +--+ Server 1  |
                 +----------+  \           |  +-----------+
                                \          |
                                 \         |
                                  \        |
                 +----------+      \       |  +-----------+
                 | Client 2 +--------------+--| Server 2  |
                 +----------+      /       |  +-----------+
                       .          /        .
                       .         /         .
                       .        /          .
                 +----------+  /           .  +-----------+
                 | Client N +-/            .--| n+1 Server|
                 +----------+                 +-----------+

                 Server 1
                 ========
                 Prefix=2001:db8:1:0000::/64
                 Range=2001:db8:1:0000::/64
                 Preference=255

                 Server 2
                 ========
                 Prefix=2001:db8:1:1000::/64
                 Range=2001:db8:1:1000::/64
                 Preference=0

                 Server 3
                 ========
                 Prefix=2001:db8:1:2000::/64
                 Range=2001:db8:1:2000::/64
                 Preference=(>0 and <255)

                     Multiple unique prefix approach.

                                 Figure 2

4.3.  Identical Prefixes

   In the identical prefix model, each DHCPv6 server is configured with
   the same overlapping prefix and range deployed for use within an IPv6
   network.  Distribution between two or more servers, for example,
   would require that the same /64 prefix and range be configured on all
   DHCP servers.  For example, the range 2001:db8:1:0001:0000::/64 would
   be assigned to all DHCPv6 server for allocation to clients derived
   from 2001:db8:1:0001::/64 prefix.  This would be repeated for each
   active DHCP server.  Example of such scenario is presented in



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   Figure 3.

   This approach uses the same prefix, length, and range definition
   across multiple DHCPv6 servers.  All other configuration remaining
   the same the only other attribute of configuration option configured
   differently per DHCPv6 server would be DHCPv6 preference.  This
   approach conceivably eases the migration of DHCPv6 services to fully
   support a standards based redundancy or failover protocol.  Similar
   to the split prefix architecture described above this approach does
   not place any additional addressing requirements on network
   infrastructure.

   The use of identical prefixes provides no benefit or advantage
   related to dynamic DNS updates, support of DHCPv6 Leasequery
   [RFC5007] or DHCPv6 Bulk Leasequery [RFC5460].  In this case all DHCP
   servers will use the same prefix and range configurations making it
   less obvious that a failure condition or event has occurred.


































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                 +----------+                 +-----------+
                 | Client 1 +-\            +--+ Server 1  |
                 +----------+  \           |  +-----------+
                                \          |
                                 \         |
                                  \        |
                 +----------+      \       |  +-----------+
                 | Client 2 +--------------+--| Server 2  |
                 +----------+      /       |  +-----------+
                       .          /        .
                       .         /         .
                       .        /          .
                 +----------+  /           .  +-----------+
                 | Client N +-/            .--| n+1 Server|
                 +----------+                 +-----------+

                 Server 1
                 ========
                 Prefix=2001:db8:1:0000::/64
                 Range=2001:db8:1:0000::/64
                 Preference=255

                 Server 2
                 ========
                 Prefix=2001:db8:1:0000::/64
                 Range=2001:db8:1:0000::/64
                 Preference=0

                 Server 3
                 ========
                 Prefix=2001:db8:1:0000::/64
                 Range=2001:db8:1:0000::/64
                 Preference=(>0 and <255)

                        Identical prefix approach.

                                 Figure 3


5.  Challenges and Issues

   The lack of interaction between DHCPv6 servers introduces a number of
   challenges related to the operations of the same in a production
   environment.  The following areas are of particular concern:

   o  Interactions with DNS server(s) to support the dynamic update of
      the same address when one or more DHCPv6 servers have become
      unavailable.  This specifically becomes a challenge when or if



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      nodes that were initially granted a lease:

      1.  Attempt to renew or rebind the lease originally granted, or

      2.  Attempt to obtain a new lease

      DHCID Resource Record, defined in [RFC4701], allows identification
      of the current owner for specific DNS data that can be used during
      DNS Update procedure [RFC2136].  [RFC4704] specifies how DHCPv6
      servers and/or client may perform updates.  [RFC4703] provides a
      way how to solve conflicts between clients.  Although it deals
      with most cases, it is still possible to leave abandoned RR
      records.  Consider following scenario.  There are two independent
      servers.  Server A assigns a lease to a client and updates DNS
      with AAAA record for assigned address and name.  When the client
      renews, server A is not available and server B assigns a different
      lease.  DNS is again updated (now two AAAA RRs are in the DNS for
      the client).  Anyone trying to use the DNS information doesn't
      know which of the two leases is active.  And, if server A never
      recovers, its information may never be removed.

   o  Interactions with DHCPv6 servers to facilitate the acquisition of
      IPv6 lease data care of the DHCPv6 Leasequery [RFC5007] or DHCPv6
      Bulk Leasequery [RFC5460] protocols when one or more DHCPv6
      servers have become unavailable and have granted leases to DHCPv6
      clients.  If IPv6 lease data is required and the granting server
      is unavailable it will not be possible to obtain any information
      about leases granted until one of the following has taken place.

      1.  The granting DHCPv6 server becomes available with all lease
          information restored

      2.  The client has renewed or rebound its lease against a
          different DHCPv6 server

      It is important to note that with DHCPv6 until such time that a
      redundancy or failover protocol is available binding updates and
      synchronization will not occur between DHCPv6 servers.


6.  IANA Considerations

   IANA is not requested to assign any numbers at this time.


7.  Security Considerations

   Security considerations specific to the operation of the DHCPv6



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   protocol are created through the use of this interim architecture for
   DHCPv6 redundancy beyond what has been cited for Dynamic Host
   Configuration Protocol for IPv6 (DHCPv6) [RFC3315].  There are
   considerations related to DNS, specifically the dynamic updating of
   DNS, when such models are employed.  Potential opportunities are
   created to overwrite valid DNS resource records when provisions have
   been made accommodate some of the models cited in this document.  In
   some cases this is desirable to ensure that DNS remains up to date
   when using one or more of these models, however, abuse of the same
   could result in undesirable behavior.


8.  Acknowledgements

   Many thanks to Bernie Volz, Kim Kinnear, Ralph Droms, Bernie Volz and
   David Hankins for their input and review.

   This work has been partially supported by Gdansk University of
   Technology.


9.  References

9.1.  Normative References

   [RFC2136]  Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
              "Dynamic Updates in the Domain Name System (DNS UPDATE)",
              RFC 2136, April 1997.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [RFC3736]  Droms, R., "Stateless Dynamic Host Configuration Protocol
              (DHCP) Service for IPv6", RFC 3736, April 2004.

   [RFC4701]  Stapp, M., Lemon, T., and A. Gustafsson, "A DNS Resource
              Record (RR) for Encoding Dynamic Host Configuration
              Protocol (DHCP) Information (DHCID RR)", RFC 4701,
              October 2006.

   [RFC4703]  Stapp, M. and B. Volz, "Resolution of Fully Qualified
              Domain Name (FQDN) Conflicts among Dynamic Host
              Configuration Protocol (DHCP) Clients", RFC 4703,



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              October 2006.

   [RFC4704]  Volz, B., "The Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
              Option", RFC 4704, October 2006.

   [RFC5007]  Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng,
              "DHCPv6 Leasequery", RFC 5007, September 2007.

   [RFC5460]  Stapp, M., "DHCPv6 Bulk Leasequery", RFC 5460,
              February 2009.

   [RFC5970]  Huth, T., Freimann, J., Zimmer, V., and D. Thaler, "DHCPv6
              Options for Network Boot", RFC 5970, September 2010.

9.2.  Informative References

   [I-D.mrugalski-dhc-dhcpv6-failover-requirements]
              Mrugalski, T. and K. Kinnear, "DHCPv6 Failover
              Requirements",
              draft-mrugalski-dhc-dhcpv6-failover-requirements-00 (work
              in progress), June 2011.


Authors' Addresses

   John Jason Brzozowski
   Comcast Cable Communications
   1306 Goshen Parkway
   West Chester, PA  19380
   USA

   Phone: +1-609-377-6594
   Email: john_brzozowski@cable.comcast.com


   Jean-Francois Tremblay
   Videotron Ltd.
   612 Saint-Jacques
   Montreal, Quebec  H3C 4M8i
   Canada

   Email: Jean-Francois.TremblayING@videotron.com








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   Jack Chen
   Time Warner Cable
   13820 Sunrise Valley Drive
   Herndon, VA  20171
   USA

   Email: jack.chen@twcable.com


   Tomasz Mrugalski
   Internet Systems Consortium, Inc.
   950 Charter St.
   Redwood City, CA  94063
   USA

   Phone: +1 650 423 1345
   Email: tomasz.mrugalski@gmail.com


































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