[NANOG] FUS for IP space fragmentation (Re: fair warning: less than 1000 days left to IPv4 exhaustion)

Sat May 10 04:02:49 UTC 2008

Talk of IPv6 space hoarding and fragmentation.  Ughh.  Perhaps we can
avoid repeating IPv4 mistakes with IPv6.

Exponential problems need linear solutions.

The method for handing out blocks is flawed.  There's no need for linear
stride-N allocations, assuming that a highly-sparse array is acceptable.

Allocate thus:

1. At start of 0b/1
2. At start of 1b/1
3. At start of 01b/2
4. At start of 11b/2
5. At start of 001b/3
6. At start of 101b/3
7. At start of 011b/3
8. At start of 111b/3
(and so forth)

Allocate on /1 boundaries as many times as possible... then /2...
followed by /3... next /4... et cetera.  Let each allocation be long
enough to contain sufficient address space; the space to the right is
reserved for growth.

Different networks will grow at different speeds.  That is handled by
allocating from "largest available /N" instead of "next /N in sequence",
and tends to keep new allocations away from rapidly-growing ones.

Fragmentation is drastically reduced.  Allocating more space is a simple
matter of "grow right", reducing the "hoard as much as possible because
new space is a pain" mentality.

Wait... we've had this discussion before:

http://www.merit.edu/mail.archives/nanog/2006-03/msg00183.html

Eddy
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