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Re: [sig-policy] Policy SIG Proposal - HD ratio for IPv4 allocations
Hi All,
Let me introduce some of the discussions we had in JP about the
proposal. The general vibes so far is that there are no strong support
for the proposal.
Comments received on our mailing list are:
* Support the concept of considering heirachical management, but
concerned that utilization rate may be too low for large
allocations
* The idea of HD-ratio is conceptualistic. It does not necessarily
match the actual operation and it is difficult to judge if it is an
appropriate way to measure utilization
* Subsequent allocation rate should be considered in terms of how
much free address space should be secured in order to accmodate
customer increase between making an allocation request and
receiving the actual allocation.
It could be possible that ISPs with small allocations also have
problems as they have less capacity to accomodate large increase in
the number of subscribers. How about applying a flat rate with
lower percentage? (No comments on this suggestion from the others)
* It disadvantages star-up ISPs when conditions are not consistent in
areas which cannot be improved by efforts, such as service quality,
price, etc
I think the general feeling at the moment is that there are no strong
opposition about reviewing the current utilization rate, but not sure
why HD-ratio should be applied(the concept already explained).
I have asked on our ML yesterday whether there is anybody who would
have a problem if HD-ratio is *NOT* applied, and there are no comments
on this yet.
To confirm the situation, do large ISPs in the rest of AP consider
they would be strongly disadvantaged and have a problem if HD-ratio is
NOT applied, or would it meet their needs by simply lowering the flat
utilization rate?
I note from Paul's explanation that some LIRs in the region are having
problems with the current rate and I do see that this should be
addressed in some way.
I would like to know what is the difference in the situation between
JP and the rest of the region.
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 *
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>
