Internet Engineering Task Force                               T. Winters
Internet-Draft                                                   QA Cafe
Updates: 7084 (if approved)                              24 January 2025
Intended status: Informational                                          
Expires: 28 July 2025


                 IPv6 CE Routers LAN Prefix Delegation
                     draft-ietf-v6ops-cpe-lan-pd-06

Abstract

   This document defines requirements for IPv6 CE Routers to support
   DHCPv6 Prefix Delegation for redistributing unused prefixes that were
   delegated to the IPv6 CE Router.  This document updates RFC 7084.

Status of This Memo

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   This Internet-Draft will expire on 28 July 2025.

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   Copyright (c) 2025 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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   provided without warranty as described in the Revised BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IPv6 End-User Network Architecture  . . . . . . . . . . . . .   3
   5.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  LAN Prefix Delegation Requirements (LDP)  . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   This document defines DHCPv6 Prefix Delegation in IPv6 CE Routers
   ([RFC7084]) in order to properly utilize the IPv6 prefixes assigned
   by service providers.  Many Service Providers assign prefixes larger
   then /64 to the CE Router, as recommended in [RFC6177].  If an IPv6
   CE Router does not support the Indentity Association for Prefix
   Delegation (IA_PD) Prefix Option ([RFC8415]) on the LAN it will not
   be able to assign any prefixes beyond its local interfaces, limiting
   the usefulness of assigning prefixes larger than /64 by the operator.
   Supporting IA_PD on the LAN interfaces will allow those unused
   prefixes to be distributed into a network.  Work is being done in the
   areas such as Stub Networking Auto Configuration (SNAC) working group
   that depends on IPv6 prefixes being properly distributed.

   Two models, hierarchical prefix and flat, have been proposed in the
   past for prefix sub-delegation beyond the IPv6 CE Router.
   Hierarchical prefix delegation requires an IPv6 CE Router to sub
   delegate IPv6 prefixes based on set of rules.  If more than one
   router uses hierarchical prefix delegation, a IPv6 prefix tree is
   created.  When no routing protocol is present to discover the network
   topology, it's possible to have unbalanced prefix delegation tree
   which leads to running out of prefixes.  For more information on
   heirachical prefix delegation is contained in Section 8.5 of
   CableLabs IPv6 eRouter Specifiction [eRouter].  A flat prefix
   delegation requires the router to be provisioned with the initial
   prefix and to assign /64 prefixes to all other prefix requests from
   routers downstream.  As the default configuration is designed to be
   the flat model to support zero configuration networking.






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   The Home Networking working group produced solutions for prefix
   delegation for home networks, including [RFC7695].  The Home
   Networking solutions haven't been deployed by Service Providers or
   IPv6 CE Routers since the publication partially due to their
   complexity.

   This document does not cover dealing with multi-provisioned networks
   with more than one provider.  Due to complexity of a solution that
   would require routing, provisioning and policy, this is out of scope
   of this document.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Terminology

   The following terminology is defined for this document.

   *  IPv6 CE Router: A router intended for home or small-office use
      that forwards packets not explicitly addressed to itself as
      defined in [RFC7084].

   *  Service Provider: An entity that provides access to the Internet
      as defined in [RFC7084]

   *  ULA:Unique Local Address as defined in [RFC4193].

   *  GUA:Global Unique Addresses as defined in [RFC4291].

4.  IPv6 End-User Network Architecture

   The end-user network that has IPv6 Customer Edge Routers with routers
   and hosts downstream.  Figure 1 illustrates the model topology.













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                        +-----------+
                        |  Service  |
                        |  Provider |
                        |   Router  |
                        +-----+-----+
                              |
                              |
                              |  Customer
                              |  Internet Connection
                              |
                        +-----v-----+
                        |   IPv6    |
                        |    CE     |
                        |  Router   |
                        +-----+-----+
                              |
                       +----+-+-------+
                       |              |
                       |              |
                   +---+----+   +-----+------+
                   |  IPv6  |   |            |
                   |  Host  |   |  Router    |
                   |        |   |            |
                   +--------+   +------------+

                  Figure 1: Example IPv6 End User Topology

5.  Requirements

   The IPv6 CE Router distributes configuration information obtained
   during WAN interface provisioning to IPv6 hosts and routers.
   Previously, an [RFC7084] compliant CE Router would only provide IPv6
   hosts with configuration information.  This allows for addressing and
   routing of IPv6 prefixes to both hosts and routers.  These
   requirements are in addition to the ones in [RFC7084]

5.1.  LAN Prefix Delegation Requirements (LDP)

   LPD-1:   The IPv6 CE Router MUST support IPv6 prefix assignment
            according to [RFC8415] (Identity Association for Prefix
            Delegation (IA_PD) option) on the LAN interface.

   LPD-2:   The IPv6 CE Router MUST assign a prefix from the delegated
            prefix as specified by L-2 [RFC7084].  If not insufficient
            are available the IPv6 CE Router SHOULD log a system
            management error.





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   LPD-3:   The prefix assigned to a link MUST NOT change in the absence
            of topology or configuration changes.

   LPD-4:   After LAN link prefix assignment the IPv6 CE Router MUST
            make the remaining IPv6 prefixes available to other routers
            via Prefix Delegation.

   LPD-5:   The IPv6 CE Router MUST install a route to the assigned
            IA_PD with a next-hop of the IPv6 node that was assigned the
            prefix.  The IPv6 CE Router MUST remove the route when IA_PD
            lease expires.

   LPD-6:   By default, the IPv6 CE Router firewall MUST allow
            forwarding of packets with an outer IPv6 header containing a
            source address belonging to Delegated Prefixes, along with
            reciprocal packets from the same flow, following the
            recommendations of [RFC6092].  This updates WPD-5 of
            [RFC7084] to not drop packets from prefixes that have been
            delegated.

   LPD-7:   The IPv6 CE Router MUST provision IA_PD prefixes with a
            prefix-length of 64 unless configured to different prefix-
            length by the user.  The prefix length of 64 is used as that
            is the current prefix length supported by SLAAC.

   LPD-8:   If the CE Router is configured to generate a ULA prefix as
            defined in ULA-1 of [RFC7084] after LAN link prefix
            assignment of the ULA prefixes the IPv6 CE Router MUST make
            the remaining IPv6 prefixes available to other routers via
            Prefix Delegation.

   LPD-9:   If the CE Router is provisioning both ULA and GUA via prefix
            delegation, the GUA SHOULD appear first in the packet.

   LPD-10:  IPv6 CE Router MUST NOT delegate prefixes via DHCPv6 on the
            LAN using lifetimes that exceed the remaining lifetimes of
            the corresponding prefixes learned on the WAN via DHCPv6-PD.

6.  Security Considerations

   This document does not add any new security considerations beyond
   those mentioned in Section 4 of [RFC8213] and Section 22 of
   [RFC8415].

7.  IANA Considerations

   This document makes no request of IANA.




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8.  Acknowledgements

   Thanks to the following people for their guidance and feedback:
   Marion Dillon, Erik Auerswald, Esko Dijk, Tim Carlin, Richard
   Patterson, Ted Lemon, Michael Richardson, Martin Huneki, Gabor
   Lencse, Ole Troan, Brian Carpenter, David Farmer, Tim Chown, Ron
   Bonica, Erica Johnson.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
              <https://www.rfc-editor.org/info/rfc4193>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <https://www.rfc-editor.org/info/rfc4291>.

   [RFC6092]  Woodyatt, J., Ed., "Recommended Simple Security
              Capabilities in Customer Premises Equipment (CPE) for
              Providing Residential IPv6 Internet Service", RFC 6092,
              DOI 10.17487/RFC6092, January 2011,
              <https://www.rfc-editor.org/info/rfc6092>.

   [RFC6177]  Narten, T., Huston, G., and L. Roberts, "IPv6 Address
              Assignment to End Sites", BCP 157, RFC 6177,
              DOI 10.17487/RFC6177, March 2011,
              <https://www.rfc-editor.org/info/rfc6177>.

   [RFC7084]  Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
              Requirements for IPv6 Customer Edge Routers", RFC 7084,
              DOI 10.17487/RFC7084, November 2013,
              <https://www.rfc-editor.org/info/rfc7084>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.







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   [RFC8213]  Volz, B. and Y. Pal, "Security of Messages Exchanged
              between Servers and Relay Agents", RFC 8213,
              DOI 10.17487/RFC8213, August 2017,
              <https://www.rfc-editor.org/info/rfc8213>.

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,
              <https://www.rfc-editor.org/info/rfc8415>.

9.2.  Informative References

   [RFC7695]  Pfister, P., Paterson, B., and J. Arkko, "Distributed
              Prefix Assignment Algorithm", RFC 7695,
              DOI 10.17487/RFC7695, November 2015,
              <https://www.rfc-editor.org/info/rfc7695>.

   [eRouter]  CableLabs, "IPv4 and IPv6 eRouter Specification Version
              I21", February 2022,
              <https://www.cablelabs.com/specifications/CM-SP-eRouter>.

Author's Address

   Timothy Winters
   QA Cafe
   100 Main Street, Suite #212
   Dover, NH 03820
   United States of America
   Email: tim@qacafe.com





















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