Experimental Physics and
Industrial Control System

"Johnson, Andrew N. via Tech-talk" <tech-talk at aps.anl.gov> · Thu, 13 Feb 2020 09:57:45 +0000

Hi Ricardo,

> On Feb 13, 2020, at 1:21 AM, Ricardo Cardenes <rcardenes at gemini.edu> wrote:
> 
> On Wed, Feb 12, 2020 at 12:41 PM Johnson, Andrew N. via Tech-talk <tech-talk at aps.anl.gov> wrote:
> 
>> I did read the other day that the latest Linux kernel release will not support NFS over UDP by default (v2 only works over UDP, I’m not sure about v3) so the writing is on the wall, but it’ll hopefully be a year or two until RHEL gets to that kernel.
> 
> As far as I know, all versions of NFS work over TCP, at least on Linux (and for a long time, you can find references to this all the way back on RHEL 4 doc, probably earlier). Quoting the Reference Guide:
> 
> All versions of NFS can use Transmission Control Protocol (TCP) running over an IP network, with NFSv4 requiring it. NFSv2 and NFSv3 can use the User Datagram Protocol (UDP) running over an IP network to provide a stateless network connection between the client and server.
> 
> Other vendors have added TCP support to NFSv2, so it's not an isolated case.
> 
> If UDP support is the problem, that could be a way around it. Of course, moving to (at least) NFSv3 would be ideal.

My point may have been more related to the VxWorks 5.5 and 6.x clients, which can only use UDP for transporting NFSv2 and possibly also for NFSv3. I had assumed that Till’s client code for RTEMS might have the same limitations, but I haven’t actually looked at that to know for sure.

- Andrew

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System