if not v6, what?

Tue Sep 7 16:34:39 UTC 2021

Michael Thomas wrote:

> I looked up CGN's this morning and the thing that struck me the most was 
> losing port forwarding. It's probably a small thing to most people but 
> losing it means to get an incoming session it always has to be mediated 
> by something on the outside.

So, to receive mails at home, we need forwarding of well known
SMTP port (25) or an external SMTP server.

> So is there anything we could have done different?

As for well known port, we can specify non-default port numbers
in URLs (I'm not sure whether it works for mailto: or not) or.
in the future, things like DNS SRV RRs should be helpful.

Then, to run servers at home, we only need some not-well-known
ports forwarded, which can be default or value added service of
your local ISP, just like fixed IP addresses today.

 > Even if we bolted two more bytes onto an IPv4 address
 > and nothing more, would that have  been adopted either?

Nothing more?

We may even develop transport protocols with 32 bit port
numbers, which is a lot easier to deploy than IPv6.

						Masataka Ohta