IPv6 Unique Local Addresses (was Re: New Active Exploit: memcached on port 11211 UDP & TCP being exploited for reflection attacks)

Fri Mar 2 13:40:37 UTC 2018

Owen DeLong <owen at delong.com> writes:

>> On Mar 2, 2018, at 3:17 AM, Bjørn Mork <bjorn at mork.no> wrote:
>> 
>> Owen DeLong <owen at delong.com> writes:
>> 
>>> What can you do with ULA that GUA isn’t suitable for?
>> 
>> 1) get
>> 2) keep
>> 3) move
>
> Wrong.
>
> 1) get
> 	Easy as going to http://tunnelbroker.net <http://tunnelbroker.net/> and filling out a form. Remember to check the box for your /48.

Provided you have IPv4 connectivity and an email address you can and
will associate with the tunnel/prefix.  You are limiting the scope here.

> 2) keep
> 	Admittedly, you might have to connect to your tunnel every once in a while to keep it alive, but that’s
> 	hardly a high bar.

Depends.  How about preconfigured devices in storage?  There are a
number of use cases where outside connectivity does not matter, and
where depending on regular connections will complicate stuff.

> 3) move
> 	If you’re not talking to the internet with it (which you can’t with ULA, theoretically), you can move that same
> 	HE /48 anywhere you want, with the additional advantage that you can, if you need to, connect your tunnel
> 	and actually make it work on the internet too.

Sure. There is also a long tradition in IPv4 for "borrowing" someone
elses addresses.  It is never a good idea.  You or anyone else cannot
make any guarantee about HE address availability at any point in time or
space.

You may also want to consider https://www.tunnelbroker.net/tos.php

>> Granted, many of us can do that with GUAs too.  But with ULA those
>> features are avaible to everyone everywhere.  Which is useful for a
>
> You really think that doing ULA according to the RFCs (collision
> avoidance algorithm and all) is easier than filling out a form at HE?
> REALLY?

Yes.

You are comparing apples and orange seeds.  If you don't want to
construct your tunnel from the RFCs, then you cannot require ULA users
to start there either,

The ULA equivalent of the HE tunnel form is an ULA calculator. E.g
http://www.kame.net/~suz/gen-ula.html

Which is much simpler.  At least it looks simpler to me.

But it doesn't really matter.  The main point is that ULAs are usable in
many cases where HE (or other ISP allocated) GUAs are not. If you don't
care about Internet connectivity, then ULAs are as good as PI GUA space.

Believe it or not, but there are still devices and networks where
Internet connectivity is either optional or even unwanted.  These
devices and networks still need addresses for their internal
communcation.

>> number of applications where you care mostly about the local environment
>> and not so much about global connectivity.
>
> I hear you, but I’m not convinced about the ease.

When was the last time you saw a non RFC1918 address in a consumer
equipment setup guide?  If we consider the distant future where IPv4 is
long dead and buried, what is default configuration URL is going to
replace http://192.168.1.1/ and similar?

IoT might be a thing for a while until people start worrying about where
they store their data.  I'm sure local sensor networks will become
popular again once the hype is over.

Many ISPs make more money on providing network accesses which are
isolated from the Internet than actually providing Internet access

More and more systems are made up of networked subsystems.  Take a look
at your average core router for example. These susbsystems need
addresses.  But you rarely want them to connect to the Internet.

One can easily imagine future PC or handheld systems where internal
buses like I2C and USB (when used to connect *internal* lowspeed
components like fingerprint readers etc) have been replaced by IP over
ethernet.

Just to name a few applications I can think of here and now.  There are
many many more.

I'm not claiming that ULAs are the answers to all these.  There are
certainly reasons why you might want GUAs instead.  But these are cases
where the main disadvantage of the ULAs - The lack of Internet
connectivity - does not matter, or is even turned into an advantage.

Bjørn