[182383] in North American Network Operators' Group
Re: Dual stack IPv6 for IPv4 depletion
daemon@ATHENA.MIT.EDU (Stephen Satchell)
Wed Jul 15 19:58:41 2015
X-Original-To: nanog@nanog.org
Date: Wed, 15 Jul 2015 16:55:15 -0700
From: Stephen Satchell <list@satchell.net>
To: Owen DeLong <owen@delong.com>
In-Reply-To: <D99C3785-455C-41B5-A5A1-6781086515AF@delong.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
On 07/15/2015 02:23 PM, Owen DeLong wrote:
> I will point out that nobody has said “what the F*** were they
> thinking” when they made it possible to use 4GB of RAM instead of
> just 640k, but lots of people have said “what the F*** were they
> thinking when they limited it to 640k.”
That 640k was the architectural limit imposed on Intel 16-bit 8086
system implementations, once you allocated fixed space for ROM. This
was specific to the "IBM PC". This has to do with the 20-bit addressing
used in the 8086. One could "grow" the address space externally, and
some computer systems (not "IBM PC compatible") did so.
Again, the 4-GB RAM limits is an architectural limit of the hardware;
there is no "speed-of-light" limit in the amount of DRAM one can have in
a system.
Let's review the bidding on Internet Protocol, shall we?
APRANET NCP (1970) -- 8-bit host
Version 0 -- can't figure out the limit, if any; 4-bit "chunks"
Version 1 -- 16-bit net/host address
Version 2 -- variable! in octet increments
Version 3 -- (not available)
Version 4-78jun -- variable! in octet increments
Version 4-78sep -- 32 bit net/host address, Class A (8-bit net)
Version 5 -- (experimental circuit-switch protocol)
Version 6 -- 128-bit
