Subject: RE: Limiting the Use of Site-Local

From: "Michel Py" <[email-masked]>
Date: Tue, 29 Oct 2002 09:20:42 -0800

[For the record, Internet access for passengers is a completely separate
system that does not connect to the plane's systems, and here's the
reason why: Imagine a bunch of IETFers in a plane. We all have laptops.
Give us an Ethernet link to the plane, someone will hack the plane just
to pass time during a long flight. Sounds like suicide to me....]

> Jim Bound wrote:
> here is not reason at all why what you stated could not
> be link-local addresses.  I would argue if sensors do what
> I hear they will do link-locals are fine and we do have
> controls on that and they are not forwarded off the link.

That's not the way it works. In the rather classic triple or quintuple
system redundancy, each of the devices that can control something is on
a separate bus (a separate subnet). But it might talk to the other two
or four all the time, and they occasionally vote and might decide that
one of the devices is out of whack, things like this. So, there are
multiple links in case of cable failure or jabbering NIC or something,
but they might talk to each other. Site-local.

>  The cockpit and intra-connections could be viewed as on link
> easily. Access to the FAA or GPA Sat-Com would require global
> (hmm maybe inter-planetary scope :--)) and as in my previous
> mail those would be gateways to the sensors.

But the plane itself would not be completely isolated either. Let's face
it: directly or indirectly there is almost no network today that is not
connected to the Internet not even a plane in flight. So saying that SLs
can not be used in networks that are connected to the Internet is the
equivalent of killing them.

Same as the other examples I used before: sensors/control devices in a
metropolitan water distribution system, or in a power grid. SLs are a
perfect choice for these, and somewhere in that network there will
likely be a host that has access to the Internet as well.

These topics have been discussed years ago, and I question why we need
to revisit this.

Michel.

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From: Keith Moore <[email-masked]>
Date: Tue, 29 Oct 2002 13:02:16 -0500

> but they might talk to each other. Site-local.

doesn't follow.  you haven't made a case for site-local, you've just
included the word at the end of the paragraph.

> equivalent of killing them.

killing SLs would not be a crime ... IMHO it would be a good thing,
though I don't expect that to happen.  ("it was a mercy killing, honest!")

and the proposal I made was saying that they could not be used in networks
that were connected to the Internet using IP.  connection via ALGs would be 
acceptable.  the point is that you don't expose a mixture of SLs and globals
except to special-purpose apps like ALGs.  (now if we can only figure out a 
way to make that stick this time)
 
> perfect choice for these, 

no they're not.  because often the reason you want these sensors on IP in 
the first place is so that you don't have to provide your own infrastructure 
to talk to them at a distance.

> These topics have been discussed years ago, and I question why we need
 
because in all this time nobody has figured out a sane way to actually
use the things, even attempting to do so increases complexity without
a significant gain, and they don't solve the problems they were supposed to
solve.  furthermore, appeals to past ignorance aren't exactly convincing.

Keith