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From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.unix-wizards
Subject: Re: Just how reliable is NFS?
Message-ID: <3504@umcp-cs.UUCP>
Date: Sat, 20-Sep-86 09:37:24 EDT
Article-I.D.: umcp-cs.3504
Posted: Sat Sep 20 09:37:24 1986
Date-Received: Sat, 20-Sep-86 21:01:13 EDT
References: <6@cvbnet.uucp> <335@mc0.UUCP> <2428@phri.UUCP> <258@stracs.cs.strath.ac.uk> <580@celerity.UUCP>
Reply-To: chris@umcp-cs.UUCP (Chris Torek)
Organization: University of Maryland, Dept. of Computer Sci.
Lines: 29

In article <580@celerity.UUCP> ron@celerity.UUCP (Ron McDaniels) writes:
>I would like to point out that the 32-bit CRC generated with every
>Ethernet packet and checked by the receiver of the packet is (orders
>of magnitude?) a far more reliable detector of transmission errors
>than the artifact of the 1st generation of computers, the checksum.
>If your Ethernet driver passes corrupted packets into the higher
>protocol levels, it is because it is ignoring the fact that the
>Ethernet controller chip has run out of memory or some similar
>problem and not because an error has crept by the CRC checking
>logic.

Or perhaps the CRC checking logic has failed, or the CRC was correct
but the transfer from Ethernet memory to host memory failed, or
any number of other possible glitches.  However, it is true that
one must trust the hardware to some extent.  (The exact extent is
often a matter of debate.)  For the sake of argument I will assume
that Ethernet reliability is high enough that a software check is
not worthwhile.

But what proponents of no software checksums seem not to have
considered is this:  Not all networks are Ethernets.  There are
other systems out there.  Many of these systems have considerably
higher error rates than Ethernets.  By disabling software checksums
you preclude the use of these less-reliable but nonetheless useful
alternative networks.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@mimsy.umd.edu