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. (301) 448-6965 (mobile) -----Original Message----- From: Brian E Carpenter [mailto:[EMAIL PROTECTED] Sent: Wednesday, October 01, 2008 4:43 PM To: Dunn, Jeffrey H. Cc: Alexandru Petrescu; [EMAIL PROTECTED]; Sherman, Kurt T.; ipv6@ietf.org; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]; 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 -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
