[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [sig-policy] Policy SIG Proposal - HD ratio for IPv4 allocations
Hi Paul and Anne,
I understand the basic idea behind the proposal but one quick quesion
about the impact on NIRs - could I assume that NIRs are expected to
"conduct an Open Policy Meeting with a view to adopting a consistent
policy with this proposal"?
I will get back to you again with comments on the proposal itself.
Thanks,
Izumi
JPNIC
From: APNIC Secretariat <secretariat@apnic.net>
Subject: [sig-policy] Policy SIG Proposal - HD ratio for IPv4 allocations
Date: Wed, 04 Aug 2004 15:25:03 +1000
> Dear All,
>
> Please find below a policy proposal for the forthcoming Policy SIG, to be
> presented at APNIC18 in Fiji.
>
> The ideas in this proposal were presented at APNIC16 as an informational
> item ("HD ratio for IPv4") on the agenda. You can find details of the
> presentation, transcripts of the discussions and minutes at:
>
> http://www.apnic.net/meetings/16/programme/sigs/policy.html
>
> Your comments and feedback on this proposal are very much appreciated on
> this mailing list.
>
> Best wishes,
> ______________________________________________________________________
> APNIC Secretariat <secretariat@apnic.net>
> Asia Pacific Network Information Centre (APNIC) Tel: +61-7-3858-3100
> PO Box 2131 Milton, QLD 4064, Australia Fax: +61-7-3858-3199
>
> See you at APNIC 18 Nadi, Fiji, 31 August-3 September 2004
> www.apnic.net/meetings
> ______________________________________________________________________
>
>
> ______________________________________________________________________
>
> prop-020-v001: Application of the HD ratio to IPv4
> ______________________________________________________________________
>
>
> Proposed by: Paul Wilson and Anne Lord, APNIC Secretariat
> Version: 1.0
> Date: 4 August 2004
>
>
> 1 Summary
> -------------
>
> Internet address space is managed hierarchically, by allocation from
> IANA to RIRs and from RIRs to LIRs (ISPs), and by assignment from LIRs
> to infrastructure and customer networks. At each level of allocation or
> assignment some address space may be reserved for future expansion
> and/or efficient aggregation. As more hierarchical levels are
> introduced, the overall efficiency of utilisation of the address space
> will decrease.
>
>
> The HD ratio (Host-Density ratio) has been proposed as a mechanism for
> measuring the utilisation of addresses within hierarchically-managed
> Internet address blocks [RFC 3194]. A given HD ratio value corresponds
> to a percentage utilisation which decreases as the size of the address
> space grows, thus allowing for the decreasing management efficiency
> which is described above.
>
> The HD ratio is used as the utilisation metric for address space under
> the current IPv6 management policy [ipv6-address-policy]. According to
> this policy, a block of IPv6 address space is considered to be utilised
> when its HD ratio reaches 0.80. This value is said to represent a
> conservative but manageable figure ("values of 80% or less correspond to
> comfortable trade-offs between pain and efficiency" [RFC 3194]).
>
> This document proposes the use of the HD ratio for measurement of IPv4
> utilisation, for the same purpose of determining when a given block of
> address space should be considered as fully utilised. The proposed value
> of the HD ratio for IPv4 is 0.96.
>
>
> 2 Background and problem
> ----------------------------
>
> Under the current management framework for IPv4 address space
> [ipv4-address-policy] a block of IPv4 addresses is considered "utilised"
> when 80% of the addresses within the block have been allocated or
> assigned. This measure is applied equally for all address blocks,
> regardless of size.
>
> Current policies assume a hierarchical system of address space
> delegation (from IANA to RIRs to LIRs to customers, as described above),
> but they make no allowance for hierarchical management within allocated
> address space. For LIRs in particular, a hierarchical approach is often
> required for assignment of address space to service elements such as
> customer networks, individual PoPs, regionalised topologies, and even
> distinct ISP products. Small network infrastructures may require simple
> hierarchies, but large infrastructures can require several levels of
> address space subdivision. These levels of hierarchy are "hidden" in
> terms of recognition by the current RIR policy framework, and highly
> constrained by the 80% utilisation requirement. As a result, management
> of large blocks is often extremely difficult, requiring large internal
> routing tables and/or frequent renumbering of internal address blocks.
>
> One of the goals of the RIR system is to avoid unnecessary depletion of
> IPv4 address space, and the 80% utilisation requirement is justified on
> that basis. However address management policies must also be practical
> in terms of management overhead imposed. It may be argued that when
> large address spaces are involved, the "80% rule" imposes unreasonable
> management overheads on an LIR.
>
> A more reasonable approach should impose a more uniform degree of
> management overhead, rather than penalising the holders of large address
> blocks. This is achievable to some degree by basing utilisation
> requirements on the HD ratio rather than the fixed percentage-based
> measure which is in use today.
>
>
> 3 Proposal
> --------------
>
> In recognition of the problems outlined above, it is now proposed to
> consider replacing the current fixed percentage based utilisation
> requirement for IPv4 address space with an HD ratio based requirement.
>
> 3.1 The HD ratio
> -----------------
>
>
> According to RFC3194, The HD ratio is calculated as follows:
>
> HD = log(U)/log(S)
>
> Where:
>
> S is the size of the address block concerned, and
> U is the number of addresses which are utilised.
>
> Note: Under the current IPv4 policy framework, addresses are
> considered to be utilised once they are assigned or sub-allocated
> by the LIR.
>
> 3.2 Selection of HD ratio value
> --------------------------------
>
> The appropriate HD ratio value should be decided on a rational
> basis. In order to do this, we make certain assumptions about the
> depth of "hidden" hierarchy involved in managing address blocks of
> various sizes. If we assume that 80% utilisation is achieved at
> each level of this assumed hierarchy, then the overall utilisation
> can be easily calculated.
>
> The following table proposes a set of hierarchical depths which may
> be reasonably expected within address spaces of given sizes. If 80%
> utilisation is achieved at each hierarchical level, then the
> overall utilisation will be (0.80 to the power of "n"); and from
> this value, corresponding HD ratio levels can then be calculated.
>
> Size range Depth Utilisation HD ratio
> (prefix) (n) (0.80**n) (calculated)
> ---------- ----- ----------- ------------
>
> /24 to /20 1 80% .960 to .973
> /20 to /16 1.5 72% .961 to .970
> /16 to /12 2 64% .960 to .968
> /12 to /8 2.5 57.2% .960 to .966
> /8 to /4 3 51.20% .960 to .966
>
> The depths of hierarchy listed above are based on simple
> assumptions about the likely size and structure of LIRs holding
> address blocks of these sizes. From the table, a rational HD ratio
> value may be chosen as 0.96 (a round figure which occurs within
> most of the above ranges). For this value, the following table
> gives the utilisation requirement for IPv4 address blocks from /24
> to /8.
>
> IPv4 Addresses Addresses Util%
> prefix total utilised
> ------ --------- --------- ------
>
> 24 256 205 80.11%
> 23 512 399 77.92%
> 22 1024 776 75.79%
> 21 2048 1510 73.71%
> 20 4096 2937 71.70%
> 19 8192 5713 69.74%
> 18 16384 11113 67.83%
> 17 32768 21619 65.98%
> 16 65536 42055 64.17%
> 15 131072 81811 62.42%
> 14 262144 159147 60.71%
> 13 524288 309590 59.05%
> 12 1048576 602249 57.43%
> 11 2097152 1171560 55.86%
> 10 4194304 2279048 54.34%
> 9 8388608 4433455 52.85%
> 8 16777216 8624444 51.41%
>
> Note: This table provides values for CIDR blocks only, however for
> non-CIDR blocks the same calculations can be applied to produce
> equally meaningful results.
>
>
> 4 Implementation
> -------------------
>
> This proposal will impact on procedures for allocation from APNIC to
> LIRs.
>
> 4.1 RIR-LIR procedures
> -----------------------
>
> The impact of the proposal on the RIR-LIR administrative procedures
> would be to replace the current 80% utilisation requirement, with a
> 0.96 HD ratio requirement.
>
> By way of examples, an LIR holding a total address space equal to a
> /16 would be able to receive more address space when they had
> allocated or assigned 64.17% of that space; while an LIR holding a
> /9 would be able to receive more space when they had allocated or
> assigned 52.85% of their address space.
>
> The HD ratio calculation is trivial, but slightly more complex than
> the existing 80% calculation. Some APNIC members may in some
> circumstances require extra assistance, however for those using
> MyAPNIC, the calculation would be automatic and require no
> additional effort.
>
> 4.2 Implementation timeline
> ----------------------------
>
> If implemented, this policy could be effective within 3 months of the
> implementation date.
>
>
> 5 References
> ---------------
>
> [RFC 3194] "The Host-Density ratio for address assignment efficiency: An
> update on the H ratio", A. Durand, C.Huitema, November 2001.
>
> [ipv6-address-policy] APNIC document: "IPv6 address allocation and
> assignment policy" http://www.apnic.net/docs/policy/
>
> [ipv4-address-policy] APNIC document: "Policies for IPv4 address space
> management in the Asia Pacific region" http://www.apnic.net/docs/
> policy/add-manage-policy.html
>
>
>
> * sig-policy: APNIC SIG on resource management policy *
> _______________________________________________
> sig-policy mailing list
> sig-policy@lists.apnic.net
> http://mailman.apnic.net/mailman/listinfo/sig-policy
>
>
