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Network Working Group                                           O. Troan
Internet-Draft                                             Cisco Systems
Intended status: Experimental                          December 28, 2018
Expires: July 1, 2019

      The Universal IPv6 Router Advertisement Option (experiment)


   One of the original intentions for the IPv6 host configuration, was
   to configure the network-layer parameters only with IPv6 ND, and use
   service discovery for other configuration information.  Unfortunately
   that hasn't panned out quite as planned, and we are in a situation
   where all kinds of configuration options are added to RAs and DHCP.
   This document proposes a new universal RA option in a self-describing
   data format, with the list of elements maintained in an IANA
   registry, with greatly relaxed rules for registration.

Status of This Memo

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

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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 1, 2019.

Copyright Notice

   Copyright (c) 2018 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
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   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.

1.  Introduction

   This document proposes a new universal option for the Router
   Advertisement IPv6 ND message [RFC4861].  It's purpose is to use the
   RA as an opaque carrier for configuration information between an
   agent on a router and host / host application.

   DHCP is suited to give per-client configuration information, while
   the RA mechanism advertises configuration information to all hosts on
   the link.  There is a long running history of "conflict" between the
   two.  The arguments go; there is less fate-sharing in DHCP, DHCP
   doesn't deal with multiple sources of information, or make it more
   difficult to change information independent of the lifetimes, RA
   cannot be used to configure different information to different
   clients and son on.  And of course some options are only available in
   RAs and some options are only available in DHCP.

   While this proposal does not resolve the DHCP vs RA debate, it
   proposes an experimental solution to the problem of a very slow
   process of standardizing new options, and the IETF spending an
   inordinate amount of time arguing over new configuration options.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  The Experiment

   This document specifies a new "self-describing" universal RA option.
   Currently new configuration option requires "standards action".  The
   purpose of the experiment is two-fold.  What is the implications of
   an opaque RA option that should not require any code changes for new
   elements within the option?  And what happens when change control is
   relaxed?  The proposal is that no IETF document is required.  The
   configuration option is described directly in the universal RA IANA
   registry.  The other part of the experiment is to

   Duration of experiment: 2 years.

   How to evaluate success?  How many new options have been defined.
   Did expert review suffice to stop "harmful" options?  Was any of the
   options implemented and deployed?  On a successful experiment, the

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   time limit of the registry will be removed and it's experimental
   status will be removed.  If the experiment is deamed a failure, then
   the registry will be removed.

4.  The Universal RA option

   The option data is described using the schema language CDDL
   [I-D.ietf-cbor-cddl], with the limitation described in appendix E
   "Use with JSON" and encoded in CBOR [RFC7049].  The restriction is
   there to ensure an easy representation in JSON [RFC8259].

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       |     Type      |    Length     |   Data

                   Figure 1: Universal RA Option Format


   Type        42 for Universal RA Option

   Length      The length of the option (including the type and length
               fields) in units of 8 octets.

   Data        CBOR encoded JSON padded to the nearest 8 octet boundary.


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       "ietf": {
           "dns": {
               "dnssl": [
               "rdnss": [
           "nat64": {
               "prefix": "64:ff9b::/96"

                                 Figure 2

   The universal RA option MUST be small enough to fit within a single
   RA packet.  It then follows that a single JSON object can not be
   larger than what fits within a single option.  Different JSON objects
   can be split across multiple universal RA options (in separate RA

   All IANA registered elements are under the "ietf" JSON object.
   Private configuration information can be included in the option using
   different keys.

5.  Implementation Guidance

   The purpose of this option is to allow users to use the RA as an
   opaque carrier for configuration information without requiring code

   On the router side there should be an API allowing a user to add a
   JSON object or a pre-encoded CBOR string to RAs sent on a given

   On the host side, an API should be available allowing applications to
   subscribe to received RA elements, based on a JSON dictionary key.
   Note, the host side must be able to decode the CBOR into a JSON

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6.  Security Considerations

   Unless there is a secutity relationship between the host and the
   router (e.g.  SEND), and even then, the consumer of configuration
   information can put no trust in the information received.

7.  IANA Considerations

   IANA is requested to add a new registry for the Universal RA option.
   The registry should be named "IPv6 ND RA Universal option
   (experimental)".  Changes and additions to the registry require
   expert review [RFC8126].

   The schema field follows the CDDL schema definition in

   The IANA is requested to add the universal option to the "IPv6
   Neighbor Discovery Option Formats" registry with the value of 42.

7.1.  Initial objects in the registry

   The PVD [I-D.ietf-intarea-provisioning-domains] elements (and PIO,
   RIO [RFC4191]) are included to provide an alternative representation
   for the proposed new options in that draft.

      | CDDL Description                                | Reference |
      | ietf = {                                        |           |
      |   ? dns : dns                                   |           |
      |   ? nat64: nat64                                |           |
      |   ? ipv6-only: bool                             |           |
      |   ? pvd : pvd                                   |           |
      |   ? mtu : uint                                  |           |
      |   ? rio : rio                                   |           |
      | }                                               |           |
      |                                                 |           |
      | pio = {                                         | [RFC4861] |
      |   prefix : tstr                                 |           |
      |   ? preferred-lifetime : uint                   |           |
      |   ? valid-lifetime : uint                       |           |
      |   ? a-flag : bool                               |           |

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      |   ? l-flag : bool                               |           |
      | }                                               |           |
      |                                                 |           |
      | rio_route = {                                   | [RFC4191] |
      |   prefix : tstr                                 |           |
      |   ? preference : (0..3)                         |           |
      |   ? lifetime : uint                             |           |
      | }                                               |           |
      | rio = {                                         |           |
      |   routes : [+ rio_route]                        |           |
      | }                                               |           |
      |                                                 |           |
      | dns = {                                         | [RFC8106] |
      |  dnssl : [* tstr]                               |           |
      |  rdnss : ipv6-addresses : [* tstr]              |           |
      |  ? lifetime : uint                              |           |
      | }                                               |           |
      |                                                 |           |
      | nat64 = {                                       | [RFC7050] |
      |   prefix : tstr                                 |           |
      | }                                               |           |
      | ipv6-only : bool                                | [v6only]  |
      |                                                 |           |
      | pvd = {                                         | [pvd]     |
      |   fqdn : tstr                                   |           |
      |   uri : tstr                                    |           |
      |   ? dns : dns                                   |           |
      |   ? nat64: nat64                                |           |
      |   ? pio : pio                                   |           |
      |   ? rio : rio                                   |           |
      | }                                               |           |

                                 Figure 3

8.  References

              Hinden, R. and B. Carpenter, "IPv6 Router Advertisement
              IPv6-Only Flag", draft-ietf-6man-ipv6only-flag-04 (work in
              progress), November 2018.

              Birkholz, H., Vigano, C., and C. Bormann, "Concise data
              definition language (CDDL): a notational convention to
              express CBOR and JSON data structures", draft-ietf-cbor-
              cddl-06 (work in progress), November 2018.

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              Pfister, P., Vyncke, E., Pauly, T., Schinazi, D., and W.
              Shao, "Discovering Provisioning Domain Names and Data",
              draft-ietf-intarea-provisioning-domains-03 (work in
              progress), October 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <https://www.rfc-editor.org/info/rfc4191>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,

Author's Address

   Ole Troan
   Cisco Systems
   Philip Pedersens vei 1
   Lysaker  1366

   Email: ot@cisco.com

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