*BSD News Article 76536


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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: 2.2-current and NFS
Date: 20 Aug 1996 21:48:41 GMT
Organization: Private BSD site, Dresden
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shanee@rabbit.augusta.de (Andreas Kohout) wrote:

> I have a little problem with my laptop. It is a DECpc 425 and without 
> fast seriall (no FIFO).
> 
> I try to connect it with my Pentium box over (user)PPP and NFS. But also 
> with 9600 baud there are some silo overflows. And than the NFS connection
> brokes down. No more packet transfere ...

I think you gotta use a full null-modem cable (including RTS/CTS
crossover), in combination with hardware flow control.

My ancient 386/sx16 notebook with a builtin non-FIFO UART handles up
to 38400 bps without flow control, and 115200 bps with flow control.
(Effective bandwidth ~ 75 % then, i.e. ~ 8 KB/s).  Of course, it
seriously loses even clock interrupts at this high rate, but it's
still impressing.

I think there are occasional silo overflows, but they are benign and
always corrected by the upper layers.

Make sure to use a small block size for NFS, since NFS suffers badly
from missed packets.  (It always has to retransmit an entire NFS block
which might be much more than one IP packet for small MTUs.)

Better yet, mount the NFS server via TCP if the server supports it.

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)