90 IPv6 sub-TLA allocations made

Colleagues,

I've just done some calculations that shows the maximum theoritical 
utilisation that can be achieved is 75% whilst maintaining the minimum size of 
routing table. That is if you take a large number of subnets, each subnet
 containing a random number of hosts, and assign to each subnet the nearest
 power of 2 larger than the number of hosts, the utilisation you get is 75%.

This is a 75% utilisation per level of network hierarchy. 

So if we assume 3 levels of network hierarchy and each level doing perfect
 routing aggregation and perfect address allocation we will get an overall
  utilisation of
 0.75^3 = 0.422 == 42% overall utilisation for the TLA.

I'd like to bet that if we have a network with enough hosts to justify 64 bits 
of address space it'll also be large enough to require more than 3 levels of 
network hierarchy. Any requirements to get high address space utilisation out 
of IPv6 can simply be demonstrated to lack scaling qualities.

Regards,


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Peter Willis		            | E-mail: peter.j.willis at bt.com
IP Technology Strategist            | Phone:  01473 645178 Fax: 01473 644506
BTexact Technologies CTO            |
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