a para from nick. some cleanups. authots' addresses.

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Randy Bush 2017-07-25 16:11:06 +09:00
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6man N. Bourbaki 6man N. Bourbaki
Internet-Draft The Intertubes Internet-Draft The Intertubes
Updates: 4291 (if approved) July 19, 2017 Updates: 4291 (if approved) July 25, 2017
Intended status: Standards Track Intended status: Standards Track
Expires: January 20, 2018 Expires: January 26, 2018
IPv6 is Classless IPv6 is Classless
@ -35,7 +35,7 @@ Status of This Memo
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 20, 2018. This Internet-Draft will expire on January 26, 2018.
Copyright Notice Copyright Notice
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Internet-Draft IPv6 is Classless July 2017 Internet-Draft IPv6 is Classless July 2017
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 2 2. Suggested Reading . . . . . . . . . . . . . . . . . . . . . . 2
3. Problem reinforced by classful addressing . . . . . . . . . . 3 3. Problems Reinforced by Classful Addressing . . . . . . . . . 3
4. Identifier and Subnet Length Statements . . . . . . . . . . . 4 4. Identifier and Subnet Length Statements . . . . . . . . . . . 4
5. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 4 5. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8. Authors . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
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[I-D.jinmei-6man-prefix-clarify] is also worth reading to clarify [I-D.jinmei-6man-prefix-clarify] is also worth reading to clarify
uses of varying prefix lengths on a single link. uses of varying prefix lengths on a single link.
3. Problem reinforced by classful addressing 3. Problems Reinforced by Classful Addressing
For host computers on local area networks, generation of interface For host computers on local area networks, generation of interface
identifiers is no longer necessarily bound to layer 2 addresses identifiers is no longer necessarily bound to layer 2 addresses
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particular constant. Rather, it should expect any lengths of particular constant. Rather, it should expect any lengths of
interface identifiers interface identifiers
As IPv6 usage has evolved and grown over in recent years, it has As IPv6 use has evolved and grown, it has become evident that it
become evident that it faces several scaling and coordination faces several scaling and coordination problems. These problems are
problems. These problems are analogous to allocation and analogous to allocation and coordination problems that motivated IPv4
coordination problems that motivated IPv4 CIDR allocation and later CIDR allocation and later abundant IPv4 PAT, they include:
abundant IPv4 PAT, they include:
Address allocation models for specific counts of fixed length Address allocation models for specific counts of fixed length
subnets to downstream networks or devices from /48 down to /64 are subnets to downstream networks or devices from /48 down to /64 are
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Hierarchical allocation of fixed-length subnets requires Hierarchical allocation of fixed-length subnets requires
coordination between lower / intermediate / upper network coordination between lower / intermediate / upper network
elements. It has implicit assumption that policies and size elements. It has implicit assumption that policies and size
allocation allowed the top of the hierarchy will accommodate allocation allowed at the top of the hierarchy will accommodate
present and future use cases with fixed length subnet allocation. present and future use cases with fixed length subnet allocation.
Coordination with upstream networks across administrative domains Coordination with upstream networks across administrative domains
for the allocation of fixed length subnets reveals topology and for the allocation of fixed length subnets reveals topology and
intent that may be private in scope. Policies for hierarchical intent that may be private in scope, allowing the upstream
allocation are applied top-down and amount to permission to build networks to restrict the topology that may be built. Policies for
hierarchical allocation are applied top-down and amount to
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a particular topology (for example mobile device tethering, permission to build a particular topology (for example mobile
virtual machine instantiation, containers and so on). device tethering, virtual machine instantiation, containers and so
on).
In the case where a device is given a /64 (e.g. mobile phone
running SLAAC only, not DHCP), there is no protocol allowing them
to provide downstream routed layer 3 subnets, because all they
have is a /64. This applies more to nodes which do not have
DHCPv6.
4. Identifier and Subnet Length Statements 4. Identifier and Subnet Length Statements
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recommended (see [RFC8064]) algorithm for selecting stable interface recommended (see [RFC8064]) algorithm for selecting stable interface
identifiers [RFC7217] is a parameter, rather than a hard-coded value. identifiers [RFC7217] is a parameter, rather than a hard-coded value.
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6. Security Considerations 6. Security Considerations
Assuming that nodes employ unpredictable interface identifiers Assuming that nodes employ unpredictable interface identifiers
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[RFC7707] [RFC7721]. For some specific subnets, such as point to [RFC7707] [RFC7721]. For some specific subnets, such as point to
point links, this may be less of an issue. point links, this may be less of an issue.
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On the other hand, we assume that a number of IPv6 implementations On the other hand, we assume that a number of IPv6 implementations
fail to enforce limits on the size of some of the data structures fail to enforce limits on the size of some of the data structures
they employ for communicating with neighboring nodes, such as the they employ for communicating with neighboring nodes, such as the
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The authors of this document are as follows: The authors of this document are as follows:
Randy Bush, Internet Initiative Japan Randy Bush <randy@psg.com>, Internet Initiative Japan
Brian Carpenter, University of Auckland Brian Carpenter <brian.e.carpenter@gmail.com>, University of
Auckland
Fernando Gont, SI6 Networks / UTN-FRH Fernando Gont <fgont@si6networks.com>, SI6 Networks / UTN-FRH
Nick Hilliard, INEX Nick Hilliard <nick@netability.ie>, INEX
Joel Jaeggli, Fastly Joel Jaeggli <joelja@bogus.com>, Fastly
Geoff Huston, APNIC Geoff Huston <gih@apnic.net>, APNIC
Chris Morrow, Google, Inc. Chris Morrow <morrowc@ops-netman.net>, Google, Inc.
Job Snijders, NTT Communications Job Snijders <morrowc@ops-netman.net>, NTT Communications
9. References 9. References
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(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>. December 1998, <http://www.rfc-editor.org/info/rfc2460>.
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[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <http://www.rfc-editor.org/info/rfc4291>. 2006, <http://www.rfc-editor.org/info/rfc4291>.
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DOI 10.17487/RFC7217, April 2014, DOI 10.17487/RFC7217, April 2014,
<http://www.rfc-editor.org/info/rfc7217>. <http://www.rfc-editor.org/info/rfc7217>.
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[RFC8064] Gont, F., Cooper, A., Thaler, D., and W. Liu, [RFC8064] Gont, F., Cooper, A., Thaler, D., and W. Liu,
"Recommendation on Stable IPv6 Interface Identifiers", "Recommendation on Stable IPv6 Interface Identifiers",
RFC 8064, DOI 10.17487/RFC8064, February 2017, RFC 8064, DOI 10.17487/RFC8064, February 2017,
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Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <http://www.rfc-editor.org/info/rfc4632>. 2006, <http://www.rfc-editor.org/info/rfc4632>.
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[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007, DOI 10.17487/RFC4862, September 2007,
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Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136, Interface Identifiers", RFC 7136, DOI 10.17487/RFC7136,
February 2014, <http://www.rfc-editor.org/info/rfc7136>. February 2014, <http://www.rfc-editor.org/info/rfc7136>.
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[RFC7608] Boucadair, M., Petrescu, A., and F. Baker, "IPv6 Prefix [RFC7608] Boucadair, M., Petrescu, A., and F. Baker, "IPv6 Prefix
Length Recommendation for Forwarding", BCP 198, RFC 7608, Length Recommendation for Forwarding", BCP 198, RFC 7608,
DOI 10.17487/RFC7608, July 2015, DOI 10.17487/RFC7608, July 2015,
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