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Re: IPv6
From: "Stephen Sprunk" <stephen () sprunk org>
Date: Thu, 12 Jun 2003 23:48:18 -0500


Thus spake "E.B. Dreger" <eddy+public+spam () noc everquick net>
SS> When a 30Mpps IPv4 box falls back to <200kpps for IPv6, I
SS> don't think "not completely functional" is an adequate
SS> description.  To me, that falls into the "not supported"
SS> category.

Why not use the highest-order 32 bits of an IPv6 address for
interdomain routing... i.e., "overlay" them on IPv4 addresses
and/or a 32-bit ASN?  Yes, it smells of classful routing.  Call
me shortsighted, but how many billion interdomain routing
policies do we really need?

Most L3 switches shipping today (e.g. the product in question) have
particular ethertypes and destination address offsets hardcoded into their
ASICs.  It's not a matter of supporting 128-bit addresses -- they simply
doesn't understand IPv6's header any more than they do DECnet or AppleTalk.

While allocation policies may have an effect on how IPv6 FIBs are most
efficiently stored, address length is a fairly small part of the problem
when you're talking about redesigning every ASIC to handle both IPv4 and
IPv6.

S


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