Dear SIG members,
A new proposal "prop-170: Nibble-Boundary Alignment for IPv6 Allocations" has been sent to the Policy SIG for review. It will be presented at the Open Policy Meeting (OPM) at APNIC 62 on Thursday, 10 September 2026. https://conference.apnic.net/62/program/program/index.html#/day/7/ We invite you to review and comment on the proposal on the mailing list before the OPM. The comment period on the mailing list before the OPM is an important part of the Policy Development Process (PDP). We encourage you to express your views on the proposal: Do you support or oppose this proposal? Does this proposal solve a problem you are experiencing? If so, tell the community about your situation. Do you see any disadvantages in this proposal? Is there anything in the proposal that is not clear? What changes could be made to this proposal to make it more effective? Information about this proposal is appended below as well as available at: https://www.apnic.net/community/policy/proposals/prop-170/ Regards, Bikram, Shaila, and Ching-Heng APNIC Policy SIG Chairs ------------------------------------------------------------------------ prop-170-v001: Nibble-Boundary Alignment for IPv6 Allocations ------------------------------------------------------------------------ Proposer: Haisheng Yu* [email protected]* [email protected] Joint proposer: Haijun Li [email protected] 1. Problem statement* -------------------- The APNIC Internet Number Resource Policies establish the rules for IPv6 allocations and assignments in the Asia Pacific region. Section 8 governs IPv6 allocations. Section 8.1 establishes a minimum IPv6 allocation size of /32 and allows a larger initial allocation where comprehensive documentation supports a larger calculated address requirement. Section 8.3.4 provides that an eligible account holder may receive a subsequent allocation that doubles the address space allocated to it and, where possible, expands the existing allocation using adjacent address space. The current policy does not establish a general principle for aligning IPv6 allocations to hexadecimal nibble boundaries. A nibble boundary is a prefix length evenly divisible by four, such as /20, /24, /28, or /32. Because IPv6 addresses are expressed in hexadecimal notation and each hexadecimal character represents four bits, nibble-boundary aligned blocks are generally easier to read, document, subdivide, automate, audit, and incorporate into long-term IPv6 address plans. Under the current policy, valid allocation outcomes may include prefixes such as /21, /23, /27, /29, /30, or /31. These prefixes are technically valid and can be routed, registered, and used. However, repeated one-bit expansions, or allocations based only on a non-aligned calculated requirement, may produce address plans that require additional operational handling in IP address management systems, customer addressing structures, routing templates, security segmentation records, audit systems, and future expansion planning. APNIC already uses a Sparse Allocation Framework to improve the possibility of contiguous growth. However, Section 8 does not currently provide a clear policy basis for nibble-boundary alignment where an LIR explicitly requests alignment and supports the request with a long-term IPv6 address plan. This proposal introduces a conditional nibble-boundary alignment mechanism for IPv6 allocations under Section 8. It applies to larger initial allocations and to subsequent allocations where the applicable eligibility and needs-based requirements have been met. It does not amend any IPv6 assignment policy under Section 9. Nibble-boundary alignment does not replace APNIC's existing needs-based assessment. This proposal does not change: - the /32 minimum IPv6 allocation size; - the HD-Ratio utilization requirements; - the one-bit doubling mechanism as the default mechanism for subsequent allocations; - the eligibility and documentation requirements for larger allocations; - APNIC's Sparse Allocation Framework; - the treatment of multiple discrete networks; or - any IPv6 assignment policy under Section 9. Existing resource holders will not be required to renumber, return, or resize any previously delegated IPv6 prefix. 2. Objective of policy change ----------------------------- The objective of this proposal is to introduce a clear and conditional nibble-boundary alignment mechanism for LIR IPv6 allocations under Section 8, while preserving APNIC's existing needs-based review, resource stewardship, and operational flexibility. Under the proposed policy: - Section 8.0 will define a nibble boundary, define the supporting long-term IPv6 address plan, and clarify the scope of the proposal; - Section 8.1 will provide that, where an applicant explicitly requests nibble-boundary alignment and supports the request with a long-term IPv6 address plan, APNIC will normally delegate the smallest nibble-boundary aligned block that can satisfy the calculated address requirement; - Section 8.3.4 will retain one-bit doubling as the default subsequent allocation size; - an account holder requesting a subsequent allocation larger than the default doubling must continue to justify the new requirement under the existing needs-based criteria; - after the larger requirement has been validated, where possible, the existing allocation will be expanded so that the resulting aggregate is nibble-boundary aligned and sufficient to satisfy the validated requirement; - if the existing allocation cannot be expanded, or cannot be expanded adequately, APNIC may make a separate allocation of the size justified, on a nibble boundary where operationally practicable; - nibble-boundary alignment will not be an unconditional entitlement; and - Sections 8.2.1, 8.2.2, and all of Section 9 will remain unchanged. 3. Situation in other regions ----------------------------- ARIN Number Resource Policy Manual (NRPM), Section 6, provides the clearest existing RIR policy example for nibble-boundary IPv6 allocation and assignment. Key original wording from ARIN includes: - Section 6.5.1 defines a nibble boundary as a "network mask which aligns on a 4-bit boundary". - Section 6.5.2.1 states: "All allocations shall be made on nibble boundaries." - Section 6.5.8.3 uses the concept of "one or more justified nibble boundaries" for subsequent end-user assignments. The relevant ARIN policy structure is broader than a single definition. Section 6.3.4 identifies aggregation as an IPv6 address management goal and explains that IPv6 policy should avoid fragmentation of address ranges. Section 6.3.7 addresses the need to reduce administrative overhead and avoid repeated small incremental requests. Section 6.3.8 states that aggregation is the most important IPv6 address policy goal. ARIN's policy demonstrates that nibble-boundary allocation can coexist with needs-based review. It does not operate as uncontrolled over-allocation. Instead, it combines a clear definition, needs-based eligibility, controls for large allocation sizes, contiguous expansion where possible, and operational flexibility for special network structures. The current RIPE IPv6 policy, RIPE-738, does not establish a general mandatory nibble-boundary rule for LIR allocations equivalent to ARIN's. However, its top-level policy objectives are closely aligned with the operational rationale of this proposal and provide policy-level support for the same direction: aggregation, avoidance of fragmentation, and reduced administrative overhead. Key original wording from RIPE-738 includes: - Section 2.7 identifies minimizing overhead as a policy goal, including minimizing "overhead associated with obtaining address space". - Section 3.4 states that IPv6 address space should be distributed in a hierarchical manner "to permit the aggregation of routing information" and that aggregation is the "highest priority" in IPv6 address policy. RIPE Policy Proposal 2024-01 is not current RIPE policy and does not revise LIR PA allocation rules. It concerns IPv6 Provider Independent assignments for end users. Although the scope is different, the proposal's core operational logic is relevant: nibble-boundary sizing can reduce repeated incremental requests, avoid network-wide renumbering, and trade a modest short-term increase in delegated address space for longer-term operational stability. This proposal is distinct from APNIC prop-164. It does not reduce the minimum IPv6 allocation from /32, does not establish /36 as the new minimum allocation, and does not require existing resource holders to return address space. Prop-164 addressed whether smaller initial IPv6 allocations should be available under APNIC policy. This proposal instead adds a conditional nibble-boundary planning rule for Section 8 LIR IPv6 allocations while preserving APNIC's existing needs-based review framework. 4. Proposed policy solution --------------------------- This proposal makes three policy text changes: - add definitions and scope under Section 8.0; - add a conditional alignment paragraph under Section 8.1; and - add a conditional alignment mechanism under Section 8.3.4. 4.1 Add definitions and scope under Section 8.0 Insert the following text immediately after the heading "8.0 IPv6 allocations": Nibble-boundary alignment A nibble boundary is a prefix length evenly divisible by four. For the purposes of Sections 8.1 and 8.3.4, a long-term IPv6 address plan is documentation supporting the requested allocation size. It may include, as applicable, expected user, customer, or site growth; the extent of the infrastructure; hierarchical and geographical network structure; security segmentation; and the planned longevity of the allocation. Nibble-boundary alignment applies only where an applicant explicitly requests it and provides the supporting long-term IPv6 address plan required by the applicable section. Nibble-boundary alignment does not replace or reduce any eligibility, utilization, HD-Ratio, or documentation requirement. It does not create an unconditional entitlement to additional address space. These provisions apply only to IPv6 allocations under Section 8. They do not amend any IPv6 assignment policy under Section 9. 4.2 Amend Section 8.1 Minimum IPv6 allocation Retain the existing text of Section 8.1 and add the following paragraph after its existing final paragraph: Where an applicant explicitly requests nibble-boundary alignment and provides a long-term IPv6 address plan, APNIC will normally delegate the smallest nibble-boundary aligned block that can satisfy the calculated address requirement. This provision applies only after the address requirement has been assessed in accordance with this section. It does not replace the HD-Ratio based utilization policy or any supporting-documentation requirement. Section 8.1 establishes the /32 minimum allocation size and governs the sizing of larger initial allocations. The expression "the smallest nibble-boundary aligned block that can satisfy the calculated address requirement" means the least amount of nibble-boundary aligned address space capable of meeting the requirement calculated under the existing policy. The alignment mechanism does not independently establish or enlarge the underlying requirement. If nibble-boundary alignment is not requested, the initial allocation will continue to be processed under the existing Section 8.1 and Section 8.2 rules. 4.3 Amend Section 8.3.4 Size of subsequent allocation Retain the existing text of Section 8.3.4: When an account holder has achieved an acceptable utilization for its allocated address space, it is immediately eligible to obtain an additional allocation that results in a doubling of the address space allocated to it. Where possible, except where separate disaggregated ranges are requested for multiple discrete networks, the allocation will be made from an adjacent address block, meaning that its existing allocation is extended by one bit to the left. If an account holder needs more address space, it must provide documentation justifying its new requirements. The allocation size will be based on the new needs (the number of users, the extent of the infrastructure, the hierarchical and geographical structuring of the account holder's operations, the segmentation of infrastructure for security and the planned longevity of the allocation). Add the following text at the end of Section 8.3.4: The one-bit doubling described above remains the default subsequent allocation size where eligibility is based on acceptable utilization alone. Where an account holder explicitly requests nibble-boundary alignment for a subsequent allocation larger than the default doubling, it must provide a long-term IPv6 address plan as part of the documentation justifying its new requirements. After APNIC validates the larger requirement: 1. Where possible, the subsequent allocation will result in the expansion of the existing allocation by one or more nibble boundaries, as justified by the validated requirement. 2. If the existing allocation cannot be expanded, or cannot be expanded adequately to meet the validated requirement, APNIC may make a separate new allocation using a nibble-boundary aligned block sufficient to satisfy the validated additional requirement. If nibble-boundary alignment is not requested, the subsequent allocation will continue to be processed under the existing one-bit doubling and needs-based sizing rules in this section. This amendment preserves one-bit doubling as the default subsequent allocation mechanism. An account holder cannot obtain a substantially larger allocation solely because it prefers nibble-boundary alignment. A request larger than the default doubling must first be supported and validated under the existing needs-based criteria. The wording follows the operational structure used in ARIN policy: expand the existing allocation where possible and, where sufficient expansion is not possible, make a separate allocation of the size justified. 4.4 Sections and mechanisms not amended This proposal makes no text change to: - Section 8.2.1, Account holders with existing IPv4 space; - Section 8.2.2, Account holders without existing IPv4 space; - Section 8.3.1, Existing IPv6 address resource holders; - Section 8.3.2, Applied HD-Ratio; - Section 8.3.3, Alternative allocation criteria; or - Section 9, IPv6 assignments. The following existing mechanisms also remain unchanged: - the /32 minimum IPv6 allocation; - the HD-Ratio value and utilization thresholds; - one-bit doubling as the default subsequent allocation size; - APNIC's Sparse Allocation Framework; and - the exception for multiple discrete networks. 5. Advantages / Disadvantages ----------------------------- Advantages - Establishes a clear Section 8 allocation mechanism The proposal gives APNIC, NIRs, LIRs, and request evaluators a clear policy basis for considering nibble-boundary alignment instead of treating it only as an informal operational preference. - Improves operational clarity Nibble-boundary aligned blocks are easier to read, document, verify, subdivide, and process in IP address management, automation, logging, routing policy, security segmentation, reverse DNS, and audit systems. - Supports hierarchical planning and aggregation Nibble-boundary alignment provides a clearer basis for dividing address space by geography, network layer, service, security domain, site, or customer group while preserving cleaner aggregates for routing and long-term internal planning. The proposal does not regulate BGP announcements, but it improves the address-planning conditions that support aggregation. - Reduces repeated incremental expansion Where a larger requirement has been validated, expansion of the existing allocation by one or more nibble boundaries, as justified, may reduce repeated small subsequent requests, administrative overhead, future fragmentation, and the risk of renumbering. - Preserves needs-based safeguards The proposal does not allow nibble-boundary alignment to substitute for eligibility, utilization, HD-Ratio, or documentation requirements. The underlying requirement must be validated before alignment is applied. - Preserves existing policy scope The proposal does not amend Section 9 assignments, reduce the /32 minimum allocation size, or alter the default one-bit doubling mechanism. Disadvantages - Larger address blocks in some cases Nibble-boundary alignment may result in the delegation of more address space than the exact non-aligned calculated requirement. For example, where a calculated requirement is larger than /32 but can be satisfied by /30, the smallest nibble-boundary aligned block that can satisfy that requirement is /28. The additional address space results from alignment to the applicable nibble boundary. It is not an independent justification for a larger underlying requirement. - Resource-management and system impact APNIC and NIRs may need to update request-evaluation procedures, registration systems, internal tools, and operational guidance to support nibble-boundary alignment consistently. Existing sparse allocation spacing may not always provide sufficient adjacent address space for the requested expansion. In those cases, a separate allocation may be required. - Possible fee impact Where membership tiers or fees are affected by the total IPv6 address space delegated to an account holder, nibble-boundary alignment may result in a higher fee category. APNIC and the relevant NIR should assess this impact and inform an applicant of any material fee consequence before the applicant accepts a nibble-boundary aligned allocation. - Implementation discretion The terms "will normally", "the smallest nibble-boundary aligned block", "one or more nibble boundaries, as justified", and "where operationally practicable" require implementation judgment. APNIC may need to publish implementation guidance to promote consistent evaluation across APNIC and NIR workflows. 6. Impact on APNIC ------------------ Existing resource holders will not be required to renumber, return, or resize IPv6 allocations delegated before implementation of this proposal. For initial allocations, the existing eligibility and needs-based assessment remain unchanged. Where a larger initial allocation has been validated and the applicant explicitly requests nibble-boundary alignment, APNIC will normally delegate the smallest nibble-boundary aligned block that can satisfy the calculated address requirement. For subsequent allocations, one-bit doubling remains the default where eligibility is based on acceptable utilization alone. A request for a larger nibble-boundary aligned allocation must satisfy the existing documentation and needs-assessment requirements. After the larger requirement has been validated, where possible, the subsequent allocation will result in the expansion of the existing allocation by one or more nibble boundaries, as justified by the validated requirement. If the existing allocation cannot be expanded, or cannot be expanded adequately, APNIC may make a separate allocation of the size justified, on a nibble boundary where operationally practicable. IPv6 assignments under Section 9 remain outside the scope of this proposal. Where an allocation request is processed through an NIR, the NIR will implement this mechanism through its local operational workflow, subject to the same policy safeguards and applicable APNIC-NIR operational procedures. APNIC and NIRs may need to update request-evaluation procedures, registration systems, internal tools, and operational guidance to support nibble-boundary alignment consistently. APNIC and the relevant NIR should also assess whether nibble-boundary alignment has any material fee consequence for an applicant before the applicant accepts the allocation. References ---------- APNIC Internet Number Resource Policies, Sections 3.1.7, 5.1.2, 8.0, 8.1, 8.2.1, 8.2.2, 8.3.1-8.3.4, and 9: https://www.apnic.net/community/policy/resources/ APNIC Guidelines for IPv6 Allocation and Assignment Requests: https://www.apnic.net/about-apnic/corporate-documents/documents/resource-guidelines/ipv6-guidelines/ ARIN Number Resource Policy Manual, Sections 6.5.1, 6.5.2.1, 6.5.3, and 6.5.8.3: https://www.arin.net/participate/policy/nrpm/ RIPE-738, IPv6 Address Allocation and Assignment Policy: https://www.ripe.net/publications/docs/ripe-738/ RIPE Policy Proposal 2024-02, IPv6 Initial Allocations /28 and Extension to /28, withdrawn 26 February 2026: https://www.ripe.net/community/policies/proposals/2024-02/ RIPE Policy Proposal 2024-01, Revised IPv6 PI Assignment Policy: https://www.ripe.net/community/policies/proposals/2024-01/ APNIC prop-164, Allocations of IPv6 Resources Longer Than a /32 with Nibble-Boundary Alignment: https://www.apnic.net/community/policy/proposals/prop-164/ _______________________________________________ Go to the SIG-policy-chair mailing list on Orbit -- https://orbit.apnic.net/mailing-list/[email protected] Explore https://orbit.apnic.net, where the APNIC community connect, discuss and share information related to Internet addressing and networking. 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