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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
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
Hi Izumi,
Sorry for the late reply.
In answer to your question - yes, this is correct. Apologies as it was left out of the text. I'll make sure this is clear when the presentation is made.
best wishes, Anne --
At 07:39 PM 5/08/2004 +0900, Izumi Okutani wrote:
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 managementpolicy *
sig-policy mailing list sig-policy@lists.apnic.net http://mailman.apnic.net/mailman/listinfo/sig-policy
sig-policy: APNIC SIG on resource managementpolicy * _______________________________________________ sig-policy mailing list sig-policy@lists.apnic.net http://mailman.apnic.net/mailman/listinfo/sig-policy
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
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
Hi Paul,
Thanks for the clarification, I understand the logic better. I am not aware of specific cases where large LIRs in JP come to us and consult the problem, but this could be because we did not pro-actively bring the issue in a manner where LIRs can explain their situation.
Let me raise the issue in the JP community and get back to you.
Izumi JPNIC
From: Paul Wilson pwilson@apnic.net Subject: Re: [sig-policy] Policy SIG Proposal - HD ratio for IPv4 allocations Date: Mon, 09 Aug 2004 17:31:55 +1000
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 *
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-- ________________________________________________________________________ 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
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sig-policy mailing list sig-policy@lists.apnic.net http://mailman.apnic.net/mailman/listinfo/sig-policy
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
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-- ________________________________________________________________________ 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
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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
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