The question to answer is, for a liberal estimate of the number of
"sites" required 50 years from now, how efficiently (how non-wastefully)
do assignments need to be made to fit within available space?
An extremely liberal estimate of the number of sites required would be
one per person. Taking the upper range of the year 2050 population
projection from http://www.popin.org/pop1998/ ...
World population currently stands at 5.9 billion persons and
is growing at 1.33 per cent per year, or an annual net
addition of 78 million people. World population in the mid
21st century is expected to be in the range of 7.3 to 10.7
billion. The medium-fertility projection, which is usually
considered as "most likely", indicates that world population
will reach 8.9 billion in 2050.
tells us to reckon on 11 billion sites. The available space for
assignment of /48 site identifiers is 45 bits worth if we confine
ourselves to one three-bit Format Prefix. (Six more such are potentially
available.) Using the H-ratio of RFC 1715 to compute the required
efficiency of assignment as log_10(1.07*10^10) / 45 = 0.22. This is less
than the efficiencies of telephone numbers and DECnetIV or IPv4 addresses
shown in RFC 1715*. Coupled with the generous assumption of a site per
person, the reasonable expectation of easier renumbering for IPv6 than
IPv4 or the telephone, and the availability of 6x more unicast address
space, I can't see any way to justify a claim that a /48 per site can't
be supported.
Matt Crawford
(* Actually, RFC 1715 understates the efficiency of phone number
allocation by using the number of nodes /before/ an increase in
numbering space was made but counting the bits /after/ the increase.)
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