Subject: Re: The bottom is /112 (was: RE: Extending a /64)

From: "Templin (US), Fred L" <[email-masked]>
Date: Mon, 16 Nov 2020 21:25:58 +0000

At the risk of time-wasting:

From: Mark Smith [mailto:[email-masked]]
Sent: Monday, November 16, 2020 1:11 PM
To: Templin (US), Fred L <[email-masked]>
Cc: 6man WG <[email-masked]>
Subject: [EXTERNAL] Re: The bottom is /112 (was: RE: Extending a /64)

On Tue, 17 Nov 2020, 03:31 Templin (US), Fred L, <[email-masked]<mailto:[email-masked]>> wrote:
New thread just to make sure this simple assertion is not lost. I hereby declare
"the bottom" to be /112. That gives a 112-bit "network part" and a 16-bit "host
part". That is as many addresses as an old-fashioned IPv4 "class-B", and it also
parallels the number of transport port numbers available in a 16-bit UDP/TCP
port number space, so it is also good for multi-addressing.

I think /112 is good for now and for all time - with the exception of /127 for
P2P links, of course. Agreed?

How would you have solved this problem if IPv6 addresses were 64 bits in size?
[>]

That alternative is long ago OBE.

That was the original proposal, and it was considered large enough to solve the next generation Internet protocol problem. See RFC8507.
[>]

I’m glad this RFC was published as a historical and evolutionary reminder.
I would have liked to have seen IPAE published as well, but it too would
have been from historical purposes.

The only reason addresses were made 128 bits was that so all IPv6 node interfaces could have single size 64 bit interface identifiers. See RFC7421.
[>]

So, maybe for now “the bottom” is /64, but leave open the possibility that it
might expand to /112 in the future?

Fred

Fred

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