I don’t think the formula is particularly difficult to understand once it is corrected, and I’d argue that change could go via the editorial process since it amounts to correcting a typo. Admittedly it’s a mathematical typo, but it’s an obvious error (confirmed by the author even) with an obvious correction.
Owen > On Aug 21, 2025, at 14:38, William Herrin <[email protected]> wrote: > > Hi Folks, > > I have three followup questions for you on the proposal to correct the > formula used to determine the maximum qualification for ISP IPv6 > addresses. > >> From the current PPML discussion, it sounds like folks agree that the > revised formula correctly aligns with the text. Does anyone disagree? > > There's a misalignment between the terms "provider allocation unit" in > NRPM 6.5.2.1c and "provider assignment unit" in 2.15 and 2.16. As far > as I can tell, these are the only places in the NRPM that either term > is used. One of these should be changed to match the other so that > folks trying to understand 6.5.2.1.c can actually find the term's > definition. Does anyone have a preference for which? > > Now the big question: if we don't abandon it for non-interest, there > are probably three ways we can proceed with this proposal: > > 1. Change the formula as proposed. > > 2. Drop the formula and rely on the now-identical text. > > 3. Drop the formula and rewrite the text for clarity, without changing > the formula the text describes. > > Option 1 makes the minimum change to the policy, but leaves behind a > formula that may be difficult to understand. > > Option 3 theoretically leaves IPv6 allocation and the NRPM in more > comprehensible state, but it would require the largest change to the > policy text and carries a risk of unintentionally changing what the > policy calls for. > > What are your thoughts on the best choice here? > > Regards, > Bill Herrin > > >> On Wed, Jul 2, 2025 at 2:53 PM William Herrin <[email protected]> wrote: >> >>> On Tue, Jul 1, 2025 at 11:34 AM ARIN <[email protected]> wrote: >>> Draft Policy ARIN-2025-6: Fix formula in 6.5.2.1c >>> >>> Problem Statement: >>> >>> Sections 6.5.2.1 explains the initial IPv6 ISP/LIR allocation in a way that >>> is difficult to follow and the formula in section (c) does not match the >>> remainder of the text. >>> >>> Policy Statement: >>> >>> In 6.5.2.1c, replace: >>> >>> "This calculation can be summarized as /N where N = P-(X+Y) and P is the >>> organization’s Provider Allocation Unit X is a multiple of 4 greater than >>> 4/3*serving sites and Y is a multiple of 4 greater than 4/3*end sites >>> served by largest serving site." >>> >>> with: >>> >>> "This calculation can be summarized as /N where N = P-(X+Y) and P is the >>> organization’s Provider Allocation Unit, X is a multiple of 4 greater than >>> 4/3*log_2(serving sites) and Y is a multiple of 4 greater than >>> 4/3*log_2(end sites served by largest serving site). >> >> >> FYI, I'm the primary Advisory Council shepherd for this draft policy. >> Here's some explanation: >> >> Section 6.5.2.1c holds the criteria for the _maximum_ initial IPv6 >> allocation for ISPs. They qualify for the number of IPv6 addresses >> described here and may request that much or a smaller block. The >> section is frankly hard to read. Here's what that part of the NRPM >> currently says: >> >> "c. The maximum allowable allocation shall be the smallest >> nibble-boundary aligned block that can provide an equally sized >> nibble-boundary aligned block to each of the requesters serving sites >> large enough to satisfy the needs of the requesters largest single >> serving site using no more than 75% of the available addresses. >> This calculation can be summarized as /N where N = P-(X+Y) and P is >> the organization’s Provider Allocation Unit X is a multiple of 4 >> greater than 4/3*serving sites and Y is a multiple of 4 greater than >> 4/3*end sites served by largest serving site. >> >> d. For purposes of the calculation in (c), an end site which can >> justify more than a /48 under the end-user assignment criteria in >> 6.5.8 shall count as the appropriate number of /48s that would be >> assigned under that policy. >> >> e. For purposes of the calculation in (c), an LIR which has >> subordinate LIRs shall make such reallocations according to the same >> policies and criteria as ARIN. In such a case, the prefixes necessary >> for such a reallocation should be treated as fully utilized in >> determining the block sizing for the parent LIR. LIRs which do not >> receive resources directly from ARIN will not be able to make such >> reallocations to subordinate LIRs and subordinate LIRs which need more >> than a /32 shall apply directly to ARIN." >> >> >> Here's how ARIN staff explained the current implementation of NRPM 6.5.2.1c: >> >> "ARIN staff implements 6.5.2.1.c based on the text. The summarized >> formula is overly complex and inaccurate for your typical IPv6 >> requestor. The text alone is more easily understood by customers and >> implemented by ARIN staff. >> >> ARIN staff calculates Initial allocation sizes by verifying how many >> serving sites the ISP has in the ARIN region, and how many customers >> are served at the largest serving site. ARIN assumes each customer >> will receive a /48 for simplicity and to promote IPv6 transition. >> >> Once the sites and customers are provided by the requestor, ARIN staff >> confirms what size is justified at the largest serving site based on >> the 75% rule. That size is applied to all sites, then checked against >> the 75% rule for the overall allocation justified by the ISP. The ISP >> can opt to request a smaller size. They are not required to request >> the largest justified size, though it is recommended to avoid future >> renumbering. >> >> For example: >> An ISP has 7 sites and 30,000 customers at the largest site. >> >> ARIN assumes each of the 30,000 customers receives a /48. There are >> only 4,096 /48s in a /36, so a /36 is too small. The next >> nibble-boundary aligned subnet is a /32 which has 65,536 /48s. 30,000 >> is less than 75% of 65,536, so the ISP’s largest serving site >> justifies a /32. >> >> Thus, each of the 7 sites receives a /32. The next nibble-boundary >> after /32 is a /28. There are 16 /32s in a /28. 7 /32s of the total 16 >> /32s is less than 75%, so the organization justifies a total >> allocation of a /28. 7 /32s for immediate allocation to each of their >> 7 sites and 9 additional /32s for future growth. >> >> Example 2: >> >> Building off the previous example, if the largest serving site had >> 60,000 customers, then a /32 would be too small. 60,000 is greater >> than 75% of the available 65,536 /48s in a /32. The next >> nibble-boundary aligned subnet is a /28, so the largest serving site >> justifies a /28. Thus, each of the 7 sites receives a /28, so the >> organization justifies a /24." >> >> >> Regards, >> Bill Herrin >> >> -- >> William Herrin >> [email protected] >> https://bill.herrin.us/ > > > > -- > William Herrin > [email protected] > https://bill.herrin.us/ > _______________________________________________ > ARIN-PPML > You are receiving this message because you are subscribed to > the ARIN Public Policy Mailing List ([email protected]). > Unsubscribe or manage your mailing list subscription at: > https://lists.arin.net/mailman/listinfo/arin-ppml > Please contact [email protected] if you experience any issues. _______________________________________________ ARIN-PPML You are receiving this message because you are subscribed to the ARIN Public Policy Mailing List ([email protected]). Unsubscribe or manage your mailing list subscription at: https://lists.arin.net/mailman/listinfo/arin-ppml Please contact [email protected] if you experience any issues.
