Re: AmigaNet warning messages

[Ignatios Souvatzis <is%jocelyn.rhein.de@localhost>]

On Fri, Aug 27, 1999 at 02:28:15AM +0200, Stefan Hensen wrote:

[About the ed0: warning - receiver ring buffer overrun messages]
> I have the same sort of ethernet board in my Amiga 4000 and I also get the
> above mentioned messages. But surprisingly, this happens only if the Amiga
> acts as NFS client and then only while reading data from the NFS server. It
> does not occur during write access to the NFS server and it also does not
> occur if the Amiga itself acts as NFS server, neither with read nor with
> write accesses. FTP file transfers also work without any error messages in
> both directions and with the Amiga acting either as client or as server.
> Also things like remote tape access work without any problems. (The machine
> "on the other side" was a Pentium II/Linux system in all cases.)
> 
> Therefore, I suspect that the problem does perhaps not really come from the
> driver for the AmigaNet board but from the NFS client part. (But I do not
> know enough about the kernel internals to be sure about this.)

You are right, sort of. But the culprit ist the idiotically designed chip.

NFS, with standard parameters, likes to send 8 kBytes of data + rpc headers
at once. Such a packet gets split up into 6 fragments on Ethernet. When the
receiver chip can't buffer them all, and the receiving cpu isn't fast enough
to read them off the chip fast enough, some get lost, or overwrite earlier
packets, depending on the Ethernet chipset used. The latter is what happens
to the Amiga ed users.

Set the "nfs read size" and "nfs write size" (nfs_mount: -r / -w options) to
1 kByte on the client machine.

FTP, rcp etc.  don't stuffer from this problem because they operate over
TCP, which knows about the packet size on (e.g.) Ethernet and only sends 
(on average) 2 packets before waiting for an ACK packet from the peer.

Regards,
        -is