Network Working Group T. Winters
Internet-Draft QA Cafe
Intended status: Standards Track O. Troan
Expires: 13 January 2022 cisco
12 July 2021
The Universal IPv6 Configuration Option
draft-troan-6man-universal-ra-option-05
Abstract
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 option for RA and DHCP 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.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 13 January 2022.
Copyright Notice
Copyright (c) 2021 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 (https://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 to this document. Code Components
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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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
4. The Universal IPv6 Configuration option . . . . . . . . . . . 3
5. CBOR encoding . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Implementation Guidance . . . . . . . . . . . . . . . . . . . 5
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
9.1. Universal configuration option . . . . . . . . . . . . . 6
9.2. Initial objects in the registry . . . . . . . . . . . . . 6
9.2.1. CDDL/JSON Mapping Parameters to CBOR . . . . . . . . 6
9.2.2. Key Registry . . . . . . . . . . . . . . . . . . . . 7
10. Normative References . . . . . . . . . . . . . . . . . . . . 8
11. Informative References . . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
This document proposes a new universal option for the Router
Advertisement IPv6 ND message [RFC4861] and DHCPv6 [RFC8415]. Its
purpose is to use the RA and DHCP messages as opaque carriers for
configuration information between an agent on a router or DHCP server
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 so 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 a 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.
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2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "*SHALL NOT*",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Additionally, the key words "*MIGHT*", "*COULD*", "*MAY WISH TO*",
"*WOULD PROBABLY*", "*SHOULD CONSIDER*", and "*MUST (BUT WE KNOW YOU
WON'T)*" in this document are to interpreted as described in RFC 6919
[RFC6919].
3. Introduction
This document specifies a new "self-describing" universal
configuration option. Currently new configuration option requires
"standards action". The proposal is that no future IETF document
will be required. The configuration option is described directly in
the universal configuration IANA registry.
4. The Universal IPv6 Configuration option
The option data is described using the schema language CDDL
[RFC8610], encoded in CBOR [RFC7049].
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: IPv6 Configuration Option Format
Fields:
Type: 42 for Universal IPv6 Configuration Option
Length: The length of the option (including the type and length
fields) in units of 8 octets.
Data: CBOR encoded data.
The Option is zero-padded to nearest 8-octet boundary.
Example of an JSON instance of the option:
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{
"ietf": {
"dns": {
"dnssl": [
"example.com"
],
"rdnss": [
"2001:db8::1",
"2001:db8::2"
]
},
"nat64": {
"prefix": "64:ff9b::/96"
},
"rio": [
{
"prefix": "::/0",
"next-hop": "fe80::1"
},
{
"prefix": "2001:db8::/32",
"next-hop": "fe80::2"
}
]
}
}
The universal IPv6 Configuration option MUST be small enough to fit
within a single IPv6 ND or DHCPv6 packet. It then follows that a
single element in the dictionary cannot be larger than what fits
within a single option. Different elements can be split across
multiple universal configuration options (in separate packets). All
IANA registered elements are under the "ietf" key in the dictionary.
Private configuration information can be included in the option using
different keys.
If information learnt via this option conflicts with other
configuration information learnt via Router Advertisement messages or
via DHCPv6, that is considered a configuration error. How those
conflicts should be resolved is left up to the implementation.
5. CBOR encoding
It is recommended that the user can configure the option using JSON.
Likewise an application registering interest in an option SHOULD be
able to use string keys. The CBOR encoding to save space, uses
integers for map keys. The mapping table between integer and string
map keys are part of the IANA registry for the option.
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Values -23-23 encodes to a single byte in CBOR, and these values are
reserved for IETF used map keys.
6. Implementation Guidance
The purpose of this option is to allow users to use the RA or DHCPv6
as an opaque carrier for configuration information without requiring
code changes in the option carrying infrastructure.
On the router or DHCPv6 server side there should be an API allowing a
user to add an element, e.g. a JSON object [RFC8259] or a pre-encoded
CBOR string to RAs sent on a given interface or to DHCPv6 messages
sent to a client.
On the host side, an API SHOULD be available allowing applications to
subscribe to received configuration elements. It SHOULD be possible
to subscribe to configuration object by dictionary key.
The contents of any elements that are not recognized, either in whole
or in part, by the receiving host MUST be ignored and the remainder
of option's contents MUST be processed as normal.
An implementation SHOULD provide a "JSON interface" for configuring
the option.
7. Implementation Status
The Universal IPv6 configuration option sending side is implemented
in VPP (https://wiki.fd.io/view/VPP (https://wiki.fd.io/view/VPP)).
The implementation is a prototype released under Apache license and
available at: https://github.com/vpp-dev/vpp/
commit/156db316565e77de30890f6e9b2630bd97b0d61d (https://github.com/
vpp-dev/vpp/commit/156db316565e77de30890f6e9b2630bd97b0d61d).
8. Security Considerations
Unless there is a security 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.
9. IANA Considerations
IANA is requested to add a new registry for the Universal IPv6
Configuration option. The registry should be named "IPv6 Universal
Configuration Information Option".
The schema field follows the CDDL schema definition in [RFC8610].
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Changes and additions to the registry follow the policies below
[RFC8126]:
+============================+========================+
| Range | Registration Procedure |
+============================+========================+
| -23-23 | Standards Action |
+----------------------------+------------------------+
| 24-32767 | Specification Required |
+----------------------------+------------------------+
| 32768-18446744073709551615 | Expert Review |
+----------------------------+------------------------+
Table 1
A new registration requires a new CBOR key to parameter name
assignment and a CDDL definition.
9.1. Universal configuration option
The IANA is requested to add the universal option to the "IPv6
Neighbor Discovery Option Formats" registry with the value of 42.
The IANA is requested to add the universal option to the "Dynamic
Host Configuration Protocol for IPv6 (DHCPv6) Option Codes" registry.
9.2. Initial objects in the registry
9.2.1. CDDL/JSON Mapping Parameters to CBOR
+===========================+==========+
| Parameter Name / JSON key | CBOR Key |
+===========================+==========+
| ietf | -23 |
+---------------------------+----------+
| pio | -22 |
+---------------------------+----------+
| mtu | -21 |
+---------------------------+----------+
| rio | -20 |
+---------------------------+----------+
| dns | -19 |
+---------------------------+----------+
| nat64 | -18 |
+---------------------------+----------+
| ipv6-only | -17 |
+---------------------------+----------+
| pvd | -16 |
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+---------------------------+----------+
| prefix | -15 |
+---------------------------+----------+
| preferred-lifetime | -14 |
+---------------------------+----------+
| valid-lifetime | -13 |
+---------------------------+----------+
| lifetime | -12 |
+---------------------------+----------+
| a-flag | -11 |
+---------------------------+----------+
| l-flag | -10 |
+---------------------------+----------+
| preference | -9 |
+---------------------------+----------+
| nexthop | -8 |
+---------------------------+----------+
| nssl | -7 |
+---------------------------+----------+
| dnss | -6 |
+---------------------------+----------+
| fqdn | -5 |
+---------------------------+----------+
| uri | -4 |
+---------------------------+----------+
Table 2
9.2.2. Key Registry
+------------------------------------------------+-----------+
|CDDL | Reference |
+------------------------------------------------+-----------+
|ietf = { | |
| ? pio : [+ pio] | |
| ? mtu : (0..65535) | |
| ? rio : [+ rio] | |
| ? dns : dns | |
| ? nat64: nat64 | |
| ? ipv6-only: bool | |
| ? pvd : pvd | |
|} | |
| | |
|pio = { | RFC4861 |
| prefix : ipv6-prefix | |
| ? preferred-lifetime : uint .size 4 | |
| ? valid-lifetime : uint .size 4 | |
| ? a-flag : bool | |
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| ? l-flag : bool | |
|} | |
| | |
|rio = { | RFC4191 |
| prefix : ipv6-prefix | |
| ? preference : (0..3) | |
| ? lifetime : uint .size 4 | |
| ? mtu : (0..65535) | |
| ? nexthop: ipv6-address | |
|} | |
| | |
|dns = { | RFC8106 |
| nssl : [* tstr] | |
| dnss : [+ ipv6-address] | |
| lifetime : uint .size 4 | |
|} | |
| | |
|nat64 = { | RFC7050 |
| prefix : ipv6-prefix | |
|} | |
| | |
|pvd = { | |
| fqdn : tstr | |
| uri : tstr | |
| ? dns : dns | |
| ? nat64: nat64 | |
| ? pio : [+ pio] | |
| ? rio : [+ rio] | |
|} | |
|ipv6-prefix = #6.261(bstr) | |
|ipv6-address = #6.260(bstr) | |
+------------------------------------------------+-----------+
10. 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>.
[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,
<https://www.rfc-editor.org/info/rfc4861>.
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[RFC6919] Barnes, R., Kent, S., and E. Rescorla, "Further Key Words
for Use in RFCs to Indicate Requirement Levels", RFC 6919,
DOI 10.17487/RFC6919, April 2013,
<https://www.rfc-editor.org/info/rfc6919>.
[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>.
[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>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>.
11. Informative References
[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,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
Appendix A. Acknowledgements
Many thanks to Dave Thaler for feedback and suggestions of a more
effective CBOR encoding. Thank you very much to Carsten Bormann for
CBOR and CDDL help.
Authors' Addresses
T. Winters
QA Cafe
Email: tim@qacafe.com
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O. Troan
cisco
Email: ot@cisco.com
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