I wonder which we will run out of first: IPv6 addresses or our
energy resources? Does the earth have sufficient energy resources to
support the level of human economic activity implied by the exhaustion of
the IPv6 address space? Guess i am looking too far into the future? :)
Maha.
On Mon, 24 Apr 2000, Mathis Jim-AJM005 wrote:
A brief history lesson...
There was some concern about a 32-bit address space. MIT-LCS
proposed 48 (or 64-bit) addresses but that was coupled with a
reduction of the TCP sequence number to 16 bits. After some
discussion, we settled on 32-bits based on the computing
resources available at the time. At that time, there was no
separate IP header, only addressing fields in the TCP header.
Around that time, the ARPANET had recently scaled up from
8-bit host addresses to 24-bits. Seemed unlikely that anyone
would build more than 100 ARPANET-sized networks with its huge
IMPs and PDP-10 mainframe computers (and UCLA's 360). 48-bit
Ethernet addressing wasn't around yet; otherwise we probably
would have picked 64 bits just to not have to deal with ARP.
This was before Moore's law; Intel had just released the
8008 microprocessor. There were less than 100,000 large
commercial buildings (>500,000 sq. ft) in the world; seemed
that the number of class-c addresses were sufficient. For
better or worse, the size of the address field went unchanged
from the original version of TCP (before IP was a separate
header).
We were caught short by a technology paradigm shift coming
from semiconductor physics. If computers rode the same
technology advancement curve as cars, we wouldn't be having
an address space problem now.
We cannot predict the next big technology paradigm shift.
The real lesson to learn from IPv4 - IPv6 (which I think
was described by Knuth in regards to conversion of computer
instruction sets but I can't find the reference) is the
cost of delaying conversion. For the longer you delay
the inevitable, the more installed base you have to
convert and the exponentially higher the resulting cost.
Jim
-----Original Message-----
From: Keith Moore [mailto:moore(_at_)cs(_dot_)utk(_dot_)edu]
Sent: Monday, April 24, 2000 2:36 PM
To: Anthony Atkielski
Cc: ietf(_at_)ietf(_dot_)org
Subject: Re: IPv6: Past mistakes repeated?
What I find interesting throughout discussions that mention
IPv6 as a
solution for a shortage of addresses in IPv4 is that people see the
problems with IPv4, but they don't realize that IPv6 will
run into the
same difficulties. _Any_ addressing scheme that uses addresses of
fixed length will run out of addresses after a finite
period of time,
I suppose that's true - as long as addresses are consumed at a rate
faster than they are recycled. But the fact that we will run out of
addresses eventually might not be terribly significant - the Sun will
also run out of hydrogen eventually, but in the meantime we still find
it useful.
and that period may be orders of magnitude shorter than anyone might
at first believe.
it is certainly true that without careful management IPv6 address
space could be consumed fairly quickly. but to me it looks like that
with even moderate care IPv6 space can last for several tens of years.
Consider IPv4. Thirty-two bits allows more than four billion
individual machines to be addressed.