Fun Friday – Datacenter Checksum Stories

In an e2e discussion on the loss of data integrity on Oracle TNS gateways that still exists today, one wag said “When Network General was adding more SQL decodes to the Sniffer(r), in the ’90s, we had a presentation on the Oracle transport (TNS) underlying SQL Net traffic. TNS rode on Netware SPP, or TCP, etc. The fellow went into packet fields in detail and explained how Oracle also made gateway software available for Sun boxes to go from an Oracle system to an IBM SNA db system. The gateway received SQL on TNS on TCP on IP on Ethernet (for instance) and spit out SQL on TNS or whatever IBM wanted. As he expounded on TNS pkt fields, a few hands went up — “What’s the checksum field for if it’s always 0?”…”It’s unimplemented for now”. “Well if it’s unused and your gateway has bad memory, how do you know the data going into the db on the other side will be good?” Answer: “I don’t know”. (Thanks to Alex Cannara).

Of course, if the Oracle tech guy had gone to the Microsoft Research school of obsfucation, he would have said “The probability of this event occuring such that the reliability of the underlying link layer is impaired by an improbably low memory bit error at ten to the minus 12 excluding thermal radiative factors and charge displacement is so low as to be impossible, hence the question is irrelevent”. Now, that’s the way to talk the talk. I guess that’s why Oracle is always Number 2 to Microsoft. 🙂

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