Internet DRAFT - draft-boucadair-6man-prefix-routing-reco
draft-boucadair-6man-prefix-routing-reco
6man Working Group M. Boucadair
Internet-Draft France Telecom
Intended status: Standards Track A. Petrescu
Expires: March 28, 2015 CEA, LIST
September 24, 2014
IPv6 Prefix Length Recommendation for Forwarding
draft-boucadair-6man-prefix-routing-reco-03
Abstract
The length of IP prefixes is an information used by forwarding and
routing processes is policy-based. As such, no maximum length must
be assumed by design.
Discussions on the 64-bit boundary in IPv6 addressing revealed a need
for a clear recommendation on which bits must be used by forwarding
decision-making processes. This document sketches a recommendation
to be followed by forwarding and routing designs with regards to the
prefix length. The aim is to avoid hard-coded routing and forwarding
designs that exclude some IP prefix lengths.
Requirements Language
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].
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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This Internet-Draft will expire on March 28, 2015.
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Copyright Notice
Copyright (c) 2014 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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Recommendation . . . . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
Recent discussions on the 64-bit boundary in IPv6 addressing
([I-D.ietf-6man-why64]) revealed a need for a clear recommendation on
which bits must be used by forwarding decision-making processes.
A detailed analysis of the 64-bit boundary in IPv6 addressing, and
the implication for end-site prefix assignment, is documented in
[I-D.ietf-6man-why64]. No recommendation is included in
[I-D.ietf-6man-why64].
It is fundamental to not link routing and forwarding to the IPv6
prefix/address semantics [RFC4291]. This document includes a
recommendation for that aim.
Forwarding decisions made by routers primarily rely upon a longest
prefix-match algorithm. Like in IPv4, the IPv6 prefix-match
algorithms involve one critical operation which is the comparison of
a destination address with a prefix present in a routing table (e.g.,
compare the 2001:db8::1 address with the 2001:db8::/64 prefix). The
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recommendation of this document is to be followed by that critical
operation.
It is important that the compare operation be a bit-wise comparison,
and not a byte-wise comparison.
2. Recommendation
Forwarding decision-making processes MUST NOT restrict by design the
length of IPv6 prefixes. In particular, forwarding processes MUST be
designed to process prefixes of any length up to /128, by increments
of 1.
Obviously, policies can be enforced to restrict the length of IP
prefixes advertised within a given domain or in a given
interconnection link. These policies are deployment-specific and/or
driven by administrative (interconnection) considerations.
This recommendation does not conflict with the 64-bit boundary
involved when IPv6 stateless address autoconfiguration (SLAAC,
[RFC4862]) is used on links such as Ethernet [RFC2464].
Some lookup algorithm implementations (find the prefix matching a
given destination address) may be affected by this recommendation,
even more so for IPv6 than IPv4. The performance of some
implementations may be degraded when prefix lengths are longer than
/64.
3. IANA Considerations
This document does not require any action from IANA.
4. Security Considerations
This document does not introduce security issues in addition to what
is discussed in [RFC4291].
5. Acknowledgements
Thanks to Eric Vyncke and Christian Jacquenet for their comments.
Special thanks to Randy Bush and Brian Carpenter for their support.
6. References
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6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
6.2. Informative References
[I-D.ietf-6man-why64]
Carpenter, B., Chown, T., Gont, F., Jiang, S., Petrescu,
A., and A. Yourtchenko, "Analysis of the 64-bit Boundary
in IPv6 Addressing", draft-ietf-6man-why64-05 (work in
progress), September 2014.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, December 1998.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Alexandru Petrescu
CEA, LIST
CEA Saclay
Gif-sur-Yvette, Ile-de-France 91190
France
Phone: +33169089223
Email: Alexandru.Petrescu@cea.fr
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