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Re: [sig-policy] Policy SIG Proposal - HD ratio for IPv4 allocations
Paul and all,
Good argument here Paul. I agree that to set a hard and fact
"%" rule for utilization of address space to be used as a justify
additional allocations is not really legitimate.
Paul Wilson wrote:
> Thanks for your question Izumi.
>
> The fundamental argument behind the HD-Ratio (and the H-Ratio before it)
> is that the administrative complexity of address space management cannot
> be represented by a simple percentage formula. The need for
> hierarchical structure imposes proportionally more complexity and
> administrative "pain" as the address space grows; and the HD-Ratio is a
> much better representation of that "pain" than is a fixed percentage,
> for an address space of any size.
>
> I would answer your specific suggestion of 70% by asking whether we can
> find any case where the 80% utilisation requirement has causes a problem
> to holders of /19 or /20 address blocks. I am unaware of any such
> cases, however I am certainly aware of many cases where the "%80 rule"
> has caused great cost and inconvenience to large address block holders
> (those for instance holding a /14 or more).
>
> For more discussion of the fundamental assumption of the HD-ratio, I
> suggest that you review RFCs 3194 and 1715. The arguments here apply as
> much to IPv4 as they do to IPv6, and in fact they would suggest to use a
> much smaller value than we have proposed.
>
> Regards,
>
> Paul
>
> Izumi Okutani wrote:
>
> > I agree that heirachical management should be taken into
> > consideration, but could this not be addressed by lowering the current
> > utilization rate to, say 70% for all LIRs?
> >
> > Since it is based on the percentage, I would assume that large ISPs
> > would enjoy a large free pool relative to smaller ISPs without
> > applying the HD-ratio. For example, LIRs with /12 blocks can have
> > 315,472 free addresses with 70% utilization rate, whereas LIRs with
> > /20 allocations would only have 1,228 addresses with the same rate.
> >
> > I am not for nor against the proposal at this stage, I simply would
> > like to know why HD-ratio should to be applied to address the problem.
> >
> > That's all from me for now, but I will also explain the proposal to
> > the JP community and get back to you with comments from JP.
> >
> >
> > Izumi
> >
> > 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
> >>
> >>
> >
> >
> > * 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
>
> --
> ________________________________________________________________________
> Paul Wilson, Director-General, APNIC <dg@apnic.net>
> http://www.apnic.net ph/fx +61 7 3858 3100/99
> ------------------------------------------------------------------------
> See you at APNIC-18! Nadi, Fiji, 31 Aug - 3 Sep 2004
> http://www.apnic.net/meetings
> * sig-policy: APNIC SIG on resource management policy *
> _______________________________________________
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