Experimental Physics and
Industrial Control System

Mark Rivers via Core-talk <core-talk at aps.anl.gov> · Wed, 17 Mar 2021 16:08:32 +0000

At the APS, and I suspect at most EPICS facilities there are a large number of expensive devices that use IPv4: motion controllers, oscilloscopes, PLCs, detectors, cameras, other instrumentation, etc.  Much of this will never be able to run IPv6 because the vendors won't provide new firmware for it.  Replacing it would cost tens of millions of dollars.  So I accept it as a fact that EPICS IOCs are going to need to communicate with IPv4 devices for the foreseeable future.  If that is so, then why is it necessary that IOCs communicate with EPICS clients over IPv6?

I certainly understand that public-facing computers will need to transition to IPv6.

Mark

-----Original Message-----
From: J. Lewis Muir <jlmuir at imca-cat.org> 
Sent: Wednesday, March 17, 2021 9:12 AM
To: Torsten Bögershausen <Torsten.Bogershausen at ess.eu>
Cc: Timo Korhonen <Timo.Korhonen at ess.eu>; Mark Rivers <rivers at cars.uchicago.edu>; 'Michael Davidsaver' <mdavidsaver at gmail.com>; Johnson, Andrew N. <anj at anl.gov>; Ben Franksen <benjamin.franksen at helmholtz-berlin.de>; EPICS core-talk <core-talk at aps.anl.gov>
Subject: Re: IPv6

On 03/17, Torsten Bögershausen via Core-talk wrote:
> The paper says "IPv6 only", right ?
> In order to get an idea what needs to be done, I imagined that the 
> switches don't transport
> IPV4 any more.
> Those switches do probably not exist in reality. You need to imagine them.
> There are not datasheets, they do not exist.
> 
> Imagine them.

The point is that it doesn't make sense to imagine them; they will never exist.  I haven't read the paper or memo or whatever it is, but if it's talking about a requirement to move away from IPv4 to IPv6, then it's limited to just the things that are IPv4, not things that are not IPv4.
It doesn't say that something that is not IPv4 must be converted to IPv6; that would be ridiculous.  I think that's the point that's trying to be made here about the switch: a traditional network switch is a layer 2 device (i.e., data link layer); it doesn't know anything about communications schemes from layer 3 and up (IPv4 and IPv6 are at layer 3), and therefore would have no way to disallow IPv4.

Lewis

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System