NFS over serial link

NFS over serial link

Post by Kevin P. Kleinfelt » Sun, 02 Sep 1990 04:01:00



I'm presently attending an IBM class on TCP/IP.  Their workbook says
AIX NFS is only supported over Token-Ring and Ethernet.
The instructor says he knows of no reason why it should not work with
a serial link.  Who is right?  Is there anyone out there who has USED
AIX NFS over a serial line?  If it won't work, why not?

(Yes, I know it will be slow, but I really plan to use it for file
downloading.  I have another machine that is my primary machine, where
I will be able to use Token-Ring, and I want my machines to have a
consistent interface to the data.)

Also, there are about 25 IBMers in this class.  They run about 2 sessions
a month.  They may not have a solid base of experience in TCP/IP (which is
a pain) but they seem to have a commitment training their staff in it.
--

gatech!nanovx!msa3b!kevin

 
 
 

NFS over serial link

Post by Karl Kleinpas » Sun, 02 Sep 1990 02:56:00


   I'm presently attending an IBM class on TCP/IP.  Their workbook says
   AIX NFS is only supported over Token-Ring and Ethernet.
   The instructor says he knows of no reason why it should not work with
   a serial link.  Who is right?  Is there anyone out there who has USED
   AIX NFS over a serial line?  If it won't work, why not?

They're both right: It's not _supported_, but it does work.

I've been experimenting rather a lot with SLIP lately in preparation
for leaving my office behind for the month of October, and one of the
things I've tried along the way is NFS mounts over SLIP.  There's not
much to be said in favor of it - "comedy is not pretty" probably sums
it up reasonably well.  Worse, I'm doing it at slow speeds like
2400bps.

A simple copy of a small (5Kbyte) file from a local disc to a remote
NFS filesystem resulted in the astounding throughput of...77bytes/s.

It's doable, but you don't want to do it.  Use ftp if all you want is
file downloading.

--Karl

 
 
 

NFS over serial link

Post by Samuel L » Sun, 02 Sep 1990 11:45:00



Quote:>The instructor says he knows of no reason why it should not work with
>a serial link. ... If it won't work, why not?

Most (all?) implementations of NFS doesn't use the UDP checksum for error
detection, and thus rely on whatever's below IP to be error-free.  In
the Ethernet and Token Ring environment this works okay because of the
relative reliability of the hardware, but on a SLIP line the chance of
a datagram getting corrupted in the middle but still arrive at the other
end is usually much higher, especially if you are using low-speed modems
without automatic error correction for the link.

So, I guess the answer is it will work most of the times, but for the
times that it doesn't work, you might not know until too late.

[ If AIX's NFS implementation actually uses the UCP checksum, then you
  can just ignore what I said above. ]

...Sam
--

 
 
 

NFS over serial link

Post by Sam Dra » Sun, 02 Sep 1990 18:46:00



Quote:>                               Is there anyone out there who has USED
>AIX NFS over a serial line?  If it won't work, why not?

We have also successfully run NFS over TCP/IP over X.25 from AIX/RT.
Worked fine, but again I'm not sure if it's officially supported (meaning
if it doesn't work for you, IBM might not promise to fix it).

Opinions are mine and mine alone.

Sam Drake / IBM Almaden Research Center