[address-policy-wg] last Call: Policy proposal #beta HD ratio policy proposal
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Hans Petter Holen
hpholen at tiscali.no
Fri Jul 1 00:37:28 CEST 2005
Hans Petter Holen wrote: Following the discussion on the mailinglist prior to and after posting the formal proposal I have seen no proposals to modify the proposal and would like to move the proposal into the conclustion phase in the policy development process http://www.ripe.net/ripe/draft-documents/pdp.html Last cal will end at July 15th. Best Regards Hans Petter Holen WG Chair > Thanks Alain, > I'll as the new PDP is not in operation yet, I'll add this to my list > as #beta v1 > > I propose that we enter into the Discussion phase for 4 weeks from > date until April 4. > > -hph > > BIDRON Alain ROSI/DAS wrote: > >> Dear Colleagues >> Referring to the minutes of the last RIPE Policy Working Group >> meeting and to the action list as updated during that meeting, I have >> to make a formal proposal on use of HD ratio for IPV4. >> Here is this policy proposal. >> In order to be consistent with the PDP Draft proposal coming from Rob >> Blokzijl I have used the template provided in the new PDP proposal. >> Best regards. >> Alain >> >> >> _________________________________________________________ >> 1. Policy Proposal Name: IPv4-HD-Ratio >> 2. Author >> a. name: Alain Bidron >> b. e-mail: alain.bidron at francetelecom.com >> c. telephone: +33 1 44 44 27 75 >> d. organisation: France Telecom >> 3. Proposal Version: V0 >> 4. Submission Date: 02/02/2005 >> 5. Suggested WG for discussion and publication: Address Policy WG >> 6. Proposal type: modify >> 7. Policy term: permanent >> 8. Summary of proposal: Internet address space is managed >> hierarchically: >> - IANA allocates space to Regional Internet Registries (RIRs). >> - RIRs allocate space to Local Internet Registries (LIRs). >> - LIRs assign space to End Users. >> >> At each level, some address space may be reserved for future >> expansion and/or efficient aggregation. As more hierarchical levels >> are introduced, the overall efficiency of the address space usage >> decreases. >> >> The HD ratio (Host-Density ratio) is a way to measure address space >> usage [RFC 3194]. The HD ratio value can relate to a percentage of >> usage, which decreases as the amount of address space grows. This >> allows for the decreasing efficiency that occurs with more >> hierarchical levels. >> >> The HD ratio is currently used to measure IPv6 address space usage >> [ipv6-address-policy]. The IPv6 Address Allocation and Assignment >> Policy considers a block of IPv6 address space to be ‘used’ when its >> HD ratio reaches 0.80. This is a manageable figure ("values of 80% or >> less correspond to comfortable trade-offs between pain and >> efficiency" [RFC 3194]). >> >> This document proposes using the HD ratio to measure IPv4 usage. The >> proposed value of the HD ratio for IPv4 is 0.96. >> >> 9. Policy text: >> a. Current: "An LIR may receive an additional allocation when about >> eighty percent (80%) of all the address space currently allocated to >> it is used in valid assignments or sub-allocations." >> b. New: "An LIR may receive an additional allocation when its total >> allocated address space usage meets the HD-Ratio value of 0.96." >> >> 10. Rationale: >> >> a. Background >> The current document, “IPv4 Address Allocation and Assignment >> Policies for the RIPE NCC Service Region” [ipv4-address-policy], >> considers a block of IPv4 addresses to be ‘used’ when 80% of the >> addresses within the block have been sub-allocated or assigned. This >> is applied to all address blocks, regardless of size. >> Current policies assume a hierarchical system of address space >> delegation. However, they do not make any 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 >> Points of Presence (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 not >> recognised by the current policy framework and are highly restricted >> by the "80% rule". As a result, managing large blocks is often >> 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. However, address management policies must also >> be practical in terms of how much management overhead they cause. >> When large amounts of address space are involved, the "80% rule" can >> result in more work for an LIR. >> >> Basing usage on the HD ratio should lead to equal levels of >> management overhead across the board, rather than penalising the >> holders of large address blocks. >> >> b.Impact >> To see a rough estimation of the immediate impact of this proposal, >> an HD Ratio value of 0.96 was applied to the average amount of >> address space held by an LIR in the RIPE NCC Service Region. This >> showed that on average, LIRs would qualify for an additional >> allocation block when they have assigned or sub-allocated about 59% >> of their allocated address space. >> >> c.Arguments supporting the proposal. >> This proposal fairly takes into account addressing hierarchies used >> in large and extra-large registries and introduces a useful level of >> flexibility for those registries >> The local Internet registries using the 80% criteria may continue to >> do so and will not be impacted by the new policy. >> The RIPE NCC will provide support to minimise complicated >> calculations or administrative burden to LIRs. >> >> d. Arguments opposing the proposal. >> This proposal will have some limited impact on IPV4 address consumption. >> >> >> >> >> Appendix A. The HD ratio >> >> The HD ratio is calculated as follows [RFC 3194]: >> >> HD = log(U)/log(S) >> >> Where: >> >> S is the size of the address block concerned, and U is >> the number of addresses used. >> >> Note: The current IPv4 policy considers addresses to be ‘used’ once >> they are assigned or sub-allocated by the LIR. >> Appendix B. Selection of HD ratio value >> >> We should decide an appropriate HD ratio value on a rational basis. >> To do this, we make certain assumptions about the number of "hidden" >> hierarchical levels involved in managing address blocks of various >> sizes. If we assume there is 80% usage at each level, we can easily >> calculate the overall usage. >> >> The following table proposes a set of hierarchical levels which we >> can reasonably expect within different amounts of address space. If a >> usage of 80% is achieved at each hierarchical level, then the overall >> usage will be (0.80 to the power of "n"). It is then possible to >> calculate HD ratio values from this value. >> >> Size range Level 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 levels of hierarchy listed above are based on assumptions >> about the likely size and structure of LIRs holding address blocks of >> these sizes. A reasonable HD ratio value may be 0.96 (a round figure >> which occurs within most of these ranges) from the table above. The >> following table gives the usage requirements for IPv4 address blocks >> from /24 to /8 for this value. >> >> IPv4 Addresses Addresses Util% >> prefix total used >> 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, but the same >> calculations can be made for non-CIDR blocks. >> >> As an example, an LIR holding a total amount of address space equal >> to a /16 would be able to receive more address space when they had >> sub-allocated or assigned 64.17% of that space; while an LIR holding >> a /9 would be able to receive more space when they had sub-allocated >> or assigned 52.85% of their address space. >> >> Appendix C. 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] RIPE NCC document: "IPv6 Address Allocation and >> Assignment Policy" http://www.ripe.net/ripe/docs/ipv6policy.html >> [ipv4-address-policy] RIPE NCC document: "IPv4 Address Allocation and >> Assignment Policies for the RIPE NCC Service Region" >> http://www.ripe.net/ripe/docs/ipv4-policies.html >> >> >>
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