Considerations on the IPv6 Host Density Metric
RFC 4692
Document | Type |
RFC - Informational
(October 2006; No errata)
Was draft-huston-hd-metric (individual in ops area)
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Author | Geoff Huston | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4692 (Informational) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | David Kessens | ||
Send notices to | (None) |
Network Working Group G. Huston Request for Comments: 4692 APNIC Category: Informational October 2006 Considerations on the IPv6 Host Density Metric Status of This Memo This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This memo provides an analysis of the Host Density metric as it is currently used to guide registry allocations of IPv6 unicast address blocks. This document contrasts the address efficiency as currently adopted in the allocation of IPv4 network addresses and that used by the IPv6 protocol. Note that for large allocations there are very significant variations in the target efficiency metric between the two approaches. Table of Contents 1. Introduction ....................................................2 2. IPv6 Address Structure ..........................................2 3. The Host Density Ratio ..........................................3 4. The Role of an Address Efficiency Metric ........................4 5. Network Structure and Address Efficiency Metric .................6 6. Varying the HD-Ratio ............................................7 6.1. Simulation Results .........................................8 7. Considerations .................................................10 8. Security Considerations ........................................11 9. Acknowledgements ...............................................11 10. References ....................................................12 10.1. Normative References .....................................12 10.2. Informative References ...................................12 Appendix A. Comparison Tables ....................................13 Huston Informational [Page 1] RFC 4692 IPv6 Host Density Metric October 2006 1. Introduction Metrics of address assignment efficiency are used in the context of the Regional Internet Registries' (RIRs') address allocation function. Through the use of a common address assignment efficiency metric, individual networks can be compared to a threshold value in an objective fashion. The common use of this metric is to form part of the supporting material for an address allocation request, demonstrating that the network has met or exceeded the threshold address efficiency value, and it forms part of the supportive material relating to the justification of the allocation of a further address block. Public and private IP networks have significant differences in purpose, structure, size, and technology. Attempting to impose a single efficiency metric across this very diverse environment is a challenging task. Any address assignment efficiency threshold value has to represent a balance between stating an achievable outcome for any competently designed and operated service platform while without setting a level of consumption of address resources that imperils the protocol's longer term viability through consequent address scarcity. There are a number of views relating to address assignment efficiency, both in terms of theoretic analyses of assignment efficiency and in terms of practical targets that are part of current address assignment practices in today's Internet. This document contrasts the address efficiency metric and threshold value as currently adopted in the allocation of IPv4 network addresses and the framework used by the address allocation process for the IPv6 protocol. 2. IPv6 Address Structure Before looking at address allocation efficiency metrics, it is appropriate to summarize the address structure for IPv6 global unicast addresses. The general format for IPv6 global unicast addresses is defined in [RFC4291] as follows (Figure 1). | 64 - m bits | m bits | 64 bits | +------------------------+-----------+----------------------------+ | global routing prefix | subnet ID | interface ID | +------------------------+-----------+----------------------------+ IPv6 Address Structure Figure 1 Huston Informational [Page 2] RFC 4692 IPv6 Host Density Metric October 2006 Within the current policy framework for allocation of IPv6 addresses in the context of the public Internet, the value for 'm' in the figure above, referring to the subnet ID, is commonly a 16-bit field. Therefore, the end-site global routing prefix is 48 bits in length,Show full document text