Path: utzoo!attcan!uunet!snorkelwacker!spdcc!dyer
From: dyer@spdcc.COM (Steve Dyer)
Newsgroups: comp.unix.i386
Subject: Re: SLIP for 386/ix
Keywords: SLIP
Message-ID: <1658@ursa-major.SPDCC.COM>
Date: 13 Feb 90 13:56:48 GMT
References: <511187@nstar.UUCP>
Reply-To: dyer@ursa-major.spdcc.COM (Steve Dyer)
Organization: S.P. Dyer Computer Consulting, Cambridge MA
Lines: 37

In article <511187@nstar.UUCP> larry@nstar.UUCP (Larry Snyder) writes:
>ISC is planning on releasing Slip for 386/ix next month.  I am under
>the idea that Slip with TCP/IP and RFS will allow me to run RFS (or NFS)
>over serial lines so that I may use FTP.  Is this true?  Can someone
>fill me in with the details?

Er, you seem to be a little mixed up.  FTP is a protocol which runs over
TCP/IP which allows you to send or retrieve files between two machines.
You copy the file over, which is then part of the local file system, and
you operate on the file like any other file.  Both RFS and NFS are remote
file systems, meaning that they provide an access method beneath the UNIX
system call layer (i.e., open, close, read and write operate on remote
files in much the same way as they do on local files.)

NFS runs over RPC which usually runs over IP, and RFS can run over IP, so 
it should be at least theoretically possible to run them over SLIP, provided
your vendor gives you all the right "glue".

A couple of points: SLIP provides framing, but no checksum or retransmission.
It's very easy to drop a byte or two when a machine like a 386 is heavily
loaded.  For a protocol which ordinarily expects a low error link layer
like ethernet, SLIP can cause some nasty surprises.  In most Sun-derived
implementations of NFS, NFS checksumming is turned off by default.  Combine
this with SLIP, and it's only a matter of time before some of your data
gets corrupted.  You should see whether ISC provides some way of turning
on NFS checksums if you're going to use NFS over SLIP.  Finally, NFS over
a 9600 baud line is mainly useful (if that) for occasional archival access
to files.  I wouldn't try to beat on the filesystem at all.

-- 
Steve Dyer
dyer@ursa-major.spdcc.com aka {ima,harvard,rayssd,linus,m2c}!spdcc!dyer
dyer@arktouros.mit.edu, dyer@hstbme.mit.edu