RE: what problem is solved by proscribing non-64 bit prefixes?

["TJ" <[e-mail]>]

Funny, "On the other hand I see enormous value in allowing any size of network on any customer's premises. It's not for this generation of engineers and ISPs to constrain what our great-grandchildren might invent" is something I see as an argument for sticking with /64s.  You never know what may be developed that needs all those host bits (or, atleast - needs more than we expect ... think things like per-sessions IP addresses and such 'craziness' :)  )


Thanks!
/TJ


>-----Original Message-----
>From: [e-mail] [mailto:[e-mail]] On Behalf Of
>Dunn, Jeffrey H.
>Sent: Wednesday, October 01, 2008 11:04 PM
>To: Brian E Carpenter
>Cc: Alexandru Petrescu; [e-mail]; [e-mail];
>[e-mail]; [e-mail]; Sherman, Kurt T.; draft-ietf-
>[e-mail]; [e-mail]; [e-mail];
>[e-mail]; [e-mail]; Martin, Cynthia E.
>Subject: RE: what problem is solved by proscribing non-64 bit prefixes?
>
>Brian,
>
>Your point about raising the size of the address space to the fourth power
>is not quite correct.  If we constrain the network prefix to be 64-bits,
>then, assuming that the longest routable IPv4 prefix is 24, we have only
>raised the prefix size by the power 2.67.  Now assume that we start handing
>out /28 prefixes to ISPs for their residential customers (who are now all
>behind a NAT), we have now only raised the number of subnets to the 1.17. My
>argument is that it is not the number of unique end system addresses that is
>the issue, rather the number of subnets.
>
>As to your observation concerning this generation's engineers, I whole
>heartedly second your suggestion.
>
>Best Regards,
>
>Jeffrey Dunn
>Info Systems Eng., Lead
>MITRE Corporation.
>[phone] (mobile)
>
>
>-----Original Message-----
>From: Brian E Carpenter [mailto:[e-mail]]
>Sent: Wednesday, October 01, 2008 4:43 PM
>To: Dunn, Jeffrey H.
>Cc: Alexandru Petrescu; [e-mail]; Sherman, Kurt T.;
>[e-mail]; [e-mail]; [e-mail];
>[e-mail]; [e-mail];
>[e-mail]; [e-mail]; [e-mail]; v6ops-
>[e-mail]; Martin, Cynthia E.
>Subject: Re: what problem is solved by proscribing non-64 bit prefixes?
>
>On 2008-10-02 02:04, Dunn, Jeffrey H. wrote:
>> More to the point, what would a individual household do with
>Avogadro's
>> number worth of IPv6 addresses (2^80 = 1.2x10^24)?  This seems
>> extremely wasteful.  Further, a reasonable sized ISP with a couple of
>> million customers would require a /28 or more just for their
>> residential customer base.  This sounds like a prescription for
>address
>> exhaustion.
>
>Not in the least. Please remember that we have raised the size of the
>address space to the *fourth* power; we squared it and squared it again.
>Even if we'd stuck to the original plan of assigning /48s everywhere, that
>means we've *squared* the size of the subnet prefix space (/24 to /48).
>Unless really stupid allocation mechanisms are allowed, that is enough for
>any imaginable future. And all the evidence is that the RIRs are being
>extremely conservative in their practices for allocation. So I don't see
>even a remote cause for concern.
>
>On the other hand I see enormous value in allowing any size of network on
>any customer's premises. It's not for this generation of engineers and ISPs
>to constrain what our great-grandchildren might invent.
>
>    Brian
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