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[ih] why did CC happen at all?

On 9/2/2014 9:59 AM, Craig Partridge wrote:
>> So that weak 16 bit UDP checksum can help catch this stuff.  I wonder
>> how many corrupted files were created with NFS and broken ethernet
>> hardware?
> Lots and lots.
> At one point, a late generation of BBN Butterfly computers had a low voltage
> problem on a bus that would cause some bytes of a DMA from network adapters
> to be garbage.  Trashed the NFS filesystem, as I recall, about once a week.


We had an essentially identical type of customer problem at
Ungermann-Bass -- circa 1987 -- which used a variant of the XNS
protocol, lacking an e2e checksum.  Long history of undetected faulty
X.25/LAN router interface bug, which meant a long history of corrupted
file data.

We were developing an Internet stack for the various UB platforms and it
happens that some of the same team was working on a new X.25 box, which
we quickly installed.

We ruefully noted that if we'd been running TCP or UDP (with checksums)
there would have been no file corruption and just some retransmit
counters incremented.


Dave Crocker
Brandenburg InternetWorking