IPv6 Addressing Help

Mark Andrews marka at isc.org
Mon Aug 17 21:38:25 CDT 2009

In message <[email protected]>, "Ray Burkholder" writes:
> >
> > Why is is necessary insist that using bits in a fashion that doesn't
> > require that growth be predicated on requests for additional resources
> > be considered wasteful?
> >
> Don't we still need to subnet in a reasonably small fashion in order to
> contain broadcasts, ill-behaved machines, and other regular discovery
> crap that exists on any given segment?

That is the constrained by the number of machines on the segment.
It has nothing to do with the number of bits allocated to the local
portion other than that number of bits has to be big enough to
contain the number of machines.  With IPv4 the address space is so
tight that one drives the other.  With IPv6 these are independent
of each other.

> And if we have to segment in such a fashion, the request and allocation
> of additional resources is a natural consequence of such containment.

But we don't.

This is one of the difference between IPv4 think and IPv6 think.
I can remember the discussions about whether IPv6 addressed should
be 64 bits or not.  One of the reasons for going to 128 bits was
so that we wouldn't have to worry about being overly conservative
with address at the network level.  The original thinking was /80
which later changed to /64.  Pack networks not hosts.


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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org

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