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Network Working Group J. Abley
Internet-Draft ISC
Expires: January 11, 2006 July 10, 2005
Shim6 Applicability Statement
draft-ietf-shim6-applicability-00
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This Internet-Draft will expire on January 11, 2006.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document discusses the applicability of the Shim6 IPv6 protocol
element and associated support protocols to provide site multihoming
capabilities in IPv6.
Note on Shim6 Maturity
Shim6 is a work in progress, and does not currently meet the maturity
requirements for advancement to Proposed Standard.
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A summary of the maturity of the various technical specifications
that accompany this document can be found in Section 6.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Architectural Overview . . . . . . . . . . . . . . . . . . . . 3
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Implementations . . . . . . . . . . . . . . . . . . . . . . . 3
5. Operational Experience . . . . . . . . . . . . . . . . . . . . 4
6. Maturity Assessment . . . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . 4
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
10.1 Normative References . . . . . . . . . . . . . . . . . . . 4
10.2 Informative References . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 5
A. Change History . . . . . . . . . . . . . . . . . . . . . . . . 5
Intellectual Property and Copyright Statements . . . . . . . . 6
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1. Introduction
Site multi-homing is an arrangement by which a site may use multiple
paths to the rest of the Internet, to provide better reliability for
traffic passing in and out of the site than would be possible with a
single path. Some of the motivations for operators to multi-home
their network are described in [RFC3582].
In IPv4, site multi-homing is achieved by introducing the additional
state required to allow session resilience over re-homing events to
the global Internet routing system (sometimes referred to as the
Default-Free Zone, or DFZ) [I-D.ietf-multi6-v4-multihoming]. There
is concern that this approach will not scale [RFC3221].
In IPv6, site multi-homing in the style of IPv4 is not generally
available to end sites due to a strict route aggregation in the DFZ,
coupled with Regional Internet Registry (RIR) allocation policies
which prohibit the direct assignment of provider-independent (PI)
addresses to most end users. Site multi-homing for sites without PI
addresses is achieved by assigning multiple addresses to each host,
one from each provider. This multi-homing approach provides no
transport-layer stability across re-homing events.
Shim6 introduces transport-layer mobility across re-homing events
using a layer-3 shim approach. State information relating to the
multi-homing of two endpoints exchanging unicast traffic is retained
on the endpoints themselves, rather than in the network.
Communications between shim6-capable hosts and shim6-incapable hosts
proceed as normal, but without the benefit of transport-layer
stability. The Shim6 approach is thought to have better scaling
properties than the IPv4 approach, at the expense of somewhat reduced
operational capability.
2. Architectural Overview
A general architectural overview of Shim6 will be included here. In
the absense of useful text in this section, readers may wish to refer
to [I-D.ietf-shim6-arch].
3. Applicability
A list of shim6 technical specifications will go here, each with a
requirements level, per [RFC2026].
4. Implementations
There is no known implementation of Shim6.
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5. Operational Experience
There is no known operational experience of Shim6.
6. Maturity Assessment
Shim6 is not sufficiently mature at the time of writing to be
advanced to Proposed Standard [RFC2026]. The following is a list of
possible work remaining before such advancement might be sought:
o The Shim6 technical specifications enumerated in this document are
not yet stable.
o The Shim6 technical specifications have yet to resolve all known
design choices.
o The extent to which the Shim6 architecture is well-understood has
yet to be thoroughly gauged.
o There is no Management Information Base (MIB) available for Shim6.
o There is neither implementation nor operational experience of
Shim6.
o The Shim6 architecture has known technical ommissions.
7. Security Considerations
Security considerations go here.
8. IANA Considerations
IANA considerations go here.
9. Acknowledgements
This work was supported by the US National Science Foundation
(research grant SCI-0427144) and DNS-OARC.
10. References
10.1 Normative References
[I-D.ietf-shim6-arch]
Huston, G., "Architectural Commentary on Site Multi-homing
using a Level 3 Shim", draft-ietf-shim6-arch-00 (work in
progress), July 2005.
10.2 Informative References
[I-D.ietf-multi6-v4-multihoming]
Abley, J., Black, B., and V. Gill, "IPv4 Multihoming
Practices and Limitations",
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draft-ietf-multi6-v4-multihoming-03 (work in progress),
January 2005.
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC3221] Huston, G., "Commentary on Inter-Domain Routing in the
Internet", RFC 3221, December 2001.
[RFC3582] Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site-
Multihoming Architectures", RFC 3582, August 2003.
Author's Address
Joe Abley
Internet Systems Consortium, Inc.
950 Charter Street
Redwood City, CA 94063
US
Phone: +1 650 423 1317
Email: jabley@isc.org
Appendix A. Change History
This section should be removed prior to publication.
draft-ietf-shim6-applicability-00: First draft, largely incomplete,
submitted to facilitate comments on general structure and
approach.
Abley Expires January 11, 2006 [Page 5]
Internet-Draft Shim6 Applicability Statement July 2005
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Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
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