[address-policy-wg] Policy proposal: #beta: IPv4-HD-Ratio
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Iljitsch van Beijnum
iljitsch at muada.com
Tue Apr 26 19:53:53 CEST 2005
On 26-apr-2005, at 15:22, Michael.Dillon at radianz.com wrote: >>> Note that the current HD ratio for all IPv4 address space that isn't >>> reserved by IANA is 90.45%. >> As you see the HD Ratio propsed is much higher but >> would help LIR's with bigger allocations to justify >> their IP usage. > You are comparing apples and oranges. Or maybe you have painted > all your apples with orange paint. > > The proposal suggests that the HD ratio should be 0.96 > It does not mention a percentage. In fact, a percentage > is a kind of ratio but it is not the same kind of ratio > as the HD ratio. From RFC 3194: log(number of allocated objects) HD = ------------------------------------------ log(maximum number of allocatable objects) This ratio is defined for any number of allocatable objects greater than 1 and any number of allocated objects greater or equal than 1 and less than or equal the maximum number of allocatable objects. The ratio is usually presented as a percentage, e.g. 70%. It varies between 0 (0%), when there is just one allocation, and 1 (100%), when there is one object allocated to each available address. > The comment regarding all IP address space that is not > reserved by IANA is not clear whether it is talking about > an HD ratio or an allocation percentage. And the most important > thing is that it does not say what is the source of the > numbers that lead to the 90.45 result. Out of the 256 /8 blocks 32 are class D (224 - 239, multicast) and E (240 - 255, reserved) and three others are also unusable: 0, 10 and 127. Of the 221 usable /8s 72 were unused as of March 2005. See http://www.iana.org/assignments/ipv4-address-space . According to the ISC Domain Survey at http://www.isc.org/ds/ 317 million IPv4 hosts had a domain name in January 2005. So that's 149 * 2^24 = 2.5 billion allocatable objects with 317 million objects allocated, or: 8.501 / 9.397 = 0.9047. (log base 10.) > HD ratio for IPv4 is intended to count the number of addresses > assigned by an LIR and compare that to the number of addresses > that RIPE (or another RIR) has allocated to the LIR. No, the intent of the HD ratio is to show that we need IPv6 even though only some 9% of all usable IPv6 addresses are in use. (Throw in standard disclaimer about the host count.) > When discussing > "all IPv4 address space" or "IANA reserved address space" we are > talking about address attributes that are not covered by the > HD ratio as we know it. The HD ratio is just a rule of thumb that says on everage, we waste one fifth to an eighth of the address length. The fact that we're now apparently using more than 90% oof the address length while including sparsely populated pre-1993 address space shows that the HD ratio isn't all that useful, although it's main point, that there are losses at allocation boundaries, is of course very true.
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