Internet DRAFT - draft-gont-v6ops-host-configuration
draft-gont-v6ops-host-configuration
IPv6 Operations Working Group (v6ops) F. Gont
Internet-Draft SI6 Networks / UTN-FRH
Intended status: Best Current Practice G. Doering
Expires: September 14, 2017 SpaceNet AG
M. Garcia Corbo
SITRANS
G. Gont
SI6 Networks
March 13, 2017
On the Dynamic/Automatic Configuration of IPv6 Hosts
draft-gont-v6ops-host-configuration-01
Abstract
IPv6 has two different mechanisms for dynamic/automatic host
configuration: SLAAC and DHCPv6. These two mechanisms allow for the
configuration of IPv6 addresses and a number of network parameters.
While there is overlap in the parameters that can be configured via
these two protocols, different implementations support only subsets
of such parameters with either mechanism, or have no support for
DHCPv6 at all. This document analyzes a problem that arises from
this situation, and mandates that all host implementations support
RFC 6105 (DNS options for SLAAC) and the stateless DHCPv6
functionality in RFC 3315.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 14, 2017.
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Copyright Notice
Copyright (c) 2017 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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This document may not be modified, and derivative works of it may not
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Current Requirements regarding RDNSS and Stateless DHCPv6 . . 4
4. Requirements for IPv6 Hosts . . . . . . . . . . . . . . . . . 4
5. Requirements for IPv6 Routers . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
IPv6 has two different mechanisms for dynamic/automatic host
configuration: Stateless Address Autoconfiguration (SLAAC) [RFC4862]
and Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315].
SLAAC allows for distributed address assignment (where each host
automatically configures its own IPv6 addresses) and basic network
configuration (such as recursive DNS servers and DNS search lists).
On the other hand, DHCPv6 provides for centralized address assignment
(the DHCPv6 server leases IPv6 addresses to hosts) and richer network
configuration (NTP servers, web proxys, etc.).
Traditionally, SLAAC has been seen as a more lightweight mechanism,
suitable for resource-constrained devices, while DHCPv6 has been seen
more as heavy-weight and full-fledged mechanism. We note that this
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distinction is rather questionable, and is essentially meaningless
for typical mobile devices or home appliances.
Among the possible configuration information that can be conveyed
with both SLAAC and DHCPv6 is DNS related configuration: recursive
DNS servers and DNS search lists. Configuring this information is
probably as vital in practice as configuring IPv6 addresses, since
for obvious reasons both humans and popular applications operate on
names (rather than on IPv6 addresses). The ability to convey this
information has always been part of DHCPv6, while for the SLAAC case,
support was added in a separate document that standardizes "IPv6
Router Advertisement Options for DNS Configuration" [RFC6106].
Unfortunately, different host and router implementations provide
support for only a subset of these options. For example, some host
implementations (e.g., Android) support SLAAC DNS options [RFC6106],
but do not support stateless DHCPv6. On the other hand, other host
implementations (e.g., Microsoft Windows) support stateless DHCPv6,
but do not support [RFC6106]. Similarly, some router implementations
support [RFC6106], while others do not.
This represents a problem for IPv6 deployment, since:
1. in order to support most popular IPv6 host implementations, IPv6
networks are required to support *both* SLAAC and DHCPv6.
2. some router implementations do not support [RFC6106] and hence
support for the SLAAC DNS options may be impossible or require
yet an additional network element or network service to support
[RFC6106]
We note that, in most cases, this problem is currently masked by the
fact that most IPv6 deployments are actually dual-stack, and hence
hosts can currently rely DNS-related information being obtained via
IPv4-based DHCP. However, at the point such deployments disable IPv4
to become IPv6-only, the aforementioned problems will become evident,
possibly as a surprise to network operators.
2. Terminology
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].
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3. Current Requirements regarding RDNSS and Stateless DHCPv6
Section 7.2.1 of [RFC6434] ("IPv6 Node Requirements") states:
IPv6 nodes use DHCP [RFC3315] to obtain address configuration
information (see Section 5.9.5) and to obtain additional (non-
address) configuration. If a host implementation supports
applications or other protocols that require configuration that is
only available via DHCP, hosts SHOULD implement DHCP.
Since DNS information is (in theory) also available via RA messages,
the aforementioned text essentially makes support for stateless
DHCPv6 optional.
Regarding SLAAC DNS options, [RFC6434] states, in Section 7.3,
o Implementations SHOULD implement the DNS RA option [RFC6106].
which certainly is not clear whether it is referring to hosts,
routers, or both.
In any case, we note that [RFC6434] has been published on the
"Informational" track, and hence implementations may completely
ignore this RFC while still claiming full-compliance with all the
relevant IETF standards.
[RFC7084] ("Basic Requirements for IPv6 Customer Edge Routers")
requires support for "DNS_SERVERS [RFC3646]" option and the SLAAC DNS
options in the IPv6 CE Routers. As with [RFC6434], it was published
on the "Informational" track.
4. Requirements for IPv6 Hosts
IPv6 hosts MUST support the SLAAC DNS options specified in [RFC6106],
and the stateless DHCPv6 mechanism specified in [RFC3315].
5. Requirements for IPv6 Routers
IPv6 routers MUST support the SLAAC DNS options specified in
[RFC6106].
6. IANA Considerations
This document has no actions for IANA. The RFC-Editor should remove
this section prior to publication of this document as an RFC.
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7. Security Considerations
Host implementations supporting SLAAC are subject to a number of
attacks based on forged ICMPv6 Router Advertisement [RFC4861]
messages. Such attacks can be mitigated by means of RA-Guard
[RFC6105] [RFC7113]. Hosts supporting DHCPv6 are subject to a number
of attacks based on forged DHCPv6-server messages. Such attacks can
be mitigated by means of DHCPv6-Shield [RFC7610].
8. Acknowledgements
The authors would like to thank Chuck Anderson, Brian Carpenter, Nick
Hilliard, Philip Homburg, Mark Smith, Barbara Stark, and several
participants of the v6ops wg (TBD) for providing valuable comments on
earlier versions of this document.
Fernando Gont would like to thank Nelida Garcia and Jorge Oscar Gont
for their love and support, and Ivan Arce and Diego Armando Maradona
for their inspiration.
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,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2003, <http://www.rfc-editor.org/info/rfc3315>.
[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,
<http://www.rfc-editor.org/info/rfc4861>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<http://www.rfc-editor.org/info/rfc4862>.
[RFC6106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS Configuration",
RFC 6106, DOI 10.17487/RFC6106, November 2010,
<http://www.rfc-editor.org/info/rfc6106>.
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9.2. Informative References
[RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
DOI 10.17487/RFC6105, February 2011,
<http://www.rfc-editor.org/info/rfc6105>.
[RFC6434] Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
Requirements", RFC 6434, DOI 10.17487/RFC6434, December
2011, <http://www.rfc-editor.org/info/rfc6434>.
[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,
<http://www.rfc-editor.org/info/rfc7084>.
[RFC7113] Gont, F., "Implementation Advice for IPv6 Router
Advertisement Guard (RA-Guard)", RFC 7113,
DOI 10.17487/RFC7113, February 2014,
<http://www.rfc-editor.org/info/rfc7113>.
[RFC7610] Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield:
Protecting against Rogue DHCPv6 Servers", BCP 199,
RFC 7610, DOI 10.17487/RFC7610, August 2015,
<http://www.rfc-editor.org/info/rfc7610>.
Authors' Addresses
Fernando Gont
SI6 Networks / UTN-FRH
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706
Argentina
Phone: +54 11 4650 8472
Email: fgont@si6networks.com
URI: http://www.si6networks.com
Gert Doering
SpaceNet AG
Joseph-Dollinger-Bogen 14
Muenchen D-80807
Germany
Email: gert@space.net
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Madeleine Garcia Corbo
Servicios de Informacion del Transporte
Neptuno 358
Havana City 10400
Cuba
Email: madelen.garcia16@gmail.com
Guillermo Gont
SI6 Networks
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706
Argentina
Phone: +54 11 4650 8472
Email: ggont@si6networks.com
URI: https://www.si6networks.com
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