[ih] Checksums in Host-Host protocol

[Dave Crocker]

> On Friday, April 18, 2025 at 03:12:39 PM EDT, Steve Crocker via
> Internet-history <internet-history at elists.isoc.org> wrote:
> ...
> We removed the checkum from our design, a mistake I've rued ever since.


I was at Ungermann-Bass(*) in the latter 1980s, and managed its 
development of a TCP/IP stack for its 'smart' Ethernet cards. These has 
a Intel 186 chip on the card.

U-B´s original business was using networking tech to do terminal 
concentration back to mainframes.  That is, they reduced the amount of 
wiring needed back to the mainframe.  Eventually, however, they had to 
support PCs and that included Netbios and SMB.

The original U-B protocol stack was a modified XNS, which was true for a 
number of vendors, each making their own adaptations. (I think I was 
told that XNS had been published well enough to use but the Internet 
protocols were not yet stable, when these networking companies were 
getting started.)

While I was at U-B, there was a major fire drill for a customer that 
discovered they had very serious file data corruption. Eventually the 
culprit was found to be a bad U-B interface card. But none of the 
networking protocols enforced data integrity and this problem had, 
apparently, gone on for months.

It was quietly noted that had they been running with TCP, there would 
have been no data corruption.  Just an increase in retransmissions...


d/

(*) Ungermann-Bass was one of the original LAN companies, though it did 
not market as a networking company.  It had a very few, very large 
customers, and it never quite managed to expand from this.  One example 
was that its 'dumb' Ethernet card was superior to the wildly popular 
3Com Ethernet card.  Another was that as a private tool to aid 
development debugging, I adapted a packet tracing tool to provide 
symbolic TCP and IP traces.  After seeing some ops admin customers get 
excited about this tool, as I used it to show how the smart Ethernet 
card was performing, I tried to get Marketing interested in selling it 
and they declined.  About 2 years later, Harry Saal was making good 
money off of a similar product. sigh.

-- 
Dave Crocker

Brandenburg InternetWorking
bbiw.net
bluesky: @dcrocker.bsky.social
mast: @dcrocker at mastodon.social