IPv6 CE Routers LAN Prefix Delegation
draft-ietf-v6ops-cpe-lan-pd-00

Internet Engineering Task Force                               T. Winters
Internet-Draft                                                   QA Cafe
Intended status: Informational                          27 February 2024
Expires: 30 August 2024

                 IPv6 CE Routers LAN Prefix Delegation
                     draft-ietf-v6ops-cpe-lan-pd-00

Abstract

   This document defines requirements for IPv6 CE Routers to support
   DHCPv6 Prefix Delegation for redistributing any unused prefix(es)
   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 30 August 2024.

Copyright Notice

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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  . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

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 ISP will assign a prefix larger then /64
   to the CE Router, as recommended in [RFC6177].  If an IPv6 CE Router
   doesn't support IA_PD on the LAN it will not be able to assign any
   prefixes beyond it's local interfaces.  Limiting the usefulness of
   assigning prefixes larger than /64 by the operator.  Supporting IA_PD
   on the LAN interfaces will allow for 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 addresses being properly distibuted.

   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 then 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 provisioned with the initial prefix
   then assign /64 prefixes to all other prefix request from routers
   downstream.  This is the default configuration is designed to be the
   flat model to support zero configuration networking.

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   The Home Networking working group producted solutions for prefix
   delegation for home networks, including [RFC7695].  The Home
   Networking solutions haven't been deployed by ISPs 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
   will 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.

   This document also makes use of internal conceptual variables to
   describe protocol behavior and external variables that an
   implementation must allow system administrators to change.  The
   specific variable names, how their values change, and how their
   settings influence protocol behavior are provided to demonstrate
   protocol behavior.  An implementation is not required to have them in
   the exact form described here, as long as its external behavior is
   consistent with that described in this document.

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].

   *  Internet Service Provider (ISP): An entity that provides access to
      the Internet.  In this document, a service provider specifically
      offers Internet access using IPv6, and may also offer IPv4
      Internet access.  The service provider can provide such access
      over a variety of different transport methods such as DSL, cable,
      wireless, and others.

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, a router based on [RFC7084] would only provide IPv6 hosts
   with individual addresses; this update allows for addressing and
   routing of IPv6 prefixes to both hosts and routers.

5.1.  LAN Prefix Delegation Requirements

   LPD-1:  The IPv6 CE Router MUST support a DHCPv6 server capable of
           IPv6 prefix assignment according to [RFC8415] (Identity
           Association for Prefix Delegation (IA_PD) option).

   LPD-2:  The IPv6 CE Router MUST assign a prefix from the delegated
           prefix to each of its LAN links.  If not enough addresses are
           available the IPv6 CE Router SHOULD log a system management
           error.

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

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   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]

   LPD-7:  The IPv6 CE Router SHOULD by default provision IA_PD IA
           prefixes with a prefix-length of 64.

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.

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.

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>.

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   [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>.

   [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

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

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