WKBI #586, Redploying most of 127/8 as unicast public

Thu Nov 18 03:03:03 UTC 2021

It appears that Joe Maimon <jmaimon at jmaimon.com> said:
>Mark Andrews wrote:
>> It’s a denial of service attack on the IETF process to keep bringing up drafts like this that are never going to be approved.  127/8 is
>in use.  It isn’t free.
>
>There are so many things wrong with this statement that I am not even 
>going to try to enumerate them.

Aw, c'mon, don't leave us guessing.

>For example 
>https://datatracker.ietf.org/doc/html/draft-fuller-240space-02 from 2008 
>which fell prey to the "by the time this is usable IPv6 will have taken 
>over" groupthink.
>
>Objectively wrong.

I will agree that your explanation of the reasons the IETF didn't repurpose 240/8 is objectively wrong.

The amount of work to change every computer in the world running
TCP/IP and every IP application to treat 240/4 as unicast (or to treat
some of 127/8) is not significantly less than the work to get them to
support IPv6. So it would roughly double the work, for a 2% increase
in the address space, or for 127/8 less than 1%.  The code for IPv6
is already written, after all.

Also, while the world has run out of free IPv4 address space, there is
plenty of IPv4 if you are willing to pay for it. A 2% increase in v4
addresses would not change that.

>> "By contrast, IPv6, despite its vastly larger pool of available address space, allocates only a single local loopback address (::1)
>[RFC4291]. This appears to be an architectural vote of confidence in the idea that Internet protocols ultimately do not require millions of
>distinct loopback addresses.”
>>
>> This is an apples-to-oranges comparison.  IPv6 has both link and site local addresses and an architecture to deliver packets to specific
>instances of each.  This does not exist in the IPv4 world.
>
>SO an IPv6 only system without any network interfaces can run multiple 
>discrete instances of the same daemon accepting connections on the same 
>TCP port?

Sure.

 Can I script that, can I template that with hardcoded 
>addresses, same as I can now for 127/8?

Sure, if you think that's a good idea which it isn't.  Use LLAs on your loopback interface.

Personally, I take my 127/8 addresses from a configuration file since I don't know in advance what
other daemons might also want to run on addresses only visible on the local machine.  Or, you know,
some maniac might decide that part of 127/8 isn't loopback so I have to move them to the part that
still is.

In IPv6 I use ULAs since that gives me the option of routing them or not.

R's,
John