v6 subnet size for DSL & leased line customers
randy at psg.com
Thu Dec 27 04:19:27 UTC 2007
>> vendors, like everyone else, will do what is in their best interests.
>> as i am an operator, not a vendor, that is often not what is in my best
>> interest, marketing literature aside. i believe it benefits the ops
>> community to be honest when the two do not seem to coincide.
> If the ops community doesn't provide enough addresses and a way to use
> them then the vendors will do the same thing they did in v4.
i presume you mean nat v6/v6. this would be a real mess and i don't
think anyone is contending it is desirable. but this discussion is
ostensibly operators trying to understand what is actually appropriate
and useful for a class of customers, i believe those of the consumer,
soho, and similar scale.
to summarize the positions i think i have heard
o one /64 subnet per device, but the proponent gave no estimate of the
number of devices
the latter three all assuming that the allocation would be different if
the site had actual need and justification.
personally, i do not see an end site needing more than 256 subnets *by
default*, though i can certainly believe a small minority of them need
more and would use the escape clause. so, if we, for the moment, stick
to the one /64 per subnet religion, than a /56 seems sufficient for the
personally, i have a hard time thinking that any but a teensie minority,
who can use the escape clause, need more than 256. hence, i just don't
buy the /48 position.
personally, i agree that one subnet is likely to be insufficient in a
large proportion of cases. so keeping to the /64 per subnet religion, a
/64 per site is insufficient for the default.
still personally, i think the one /64 subnet per device is analogous to
one receptacle per mains breaker, i.e. not sensible.
> there are three legs to the tripod
> network operator
> equipment manufacturer
> They have (or should have) a mutual interest in:
> Transparent and automatic configuration of devices.
as you have seen from chris's excellent post  on this one, one size
does not fit all. this is likely another worthwhile, but separate,
> The assignment of globally routable addresses to internet
> connected devices
i suspect that there are folk out there who equate nat with security. i
suspect we both think them misguided.
> The user having some control over what crosses the boundry
> between their network and the operators.
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