It's been 20 years today (Oct 16, UTC). Hard to believe.

Fred Baker fredbaker.ietf at
Wed Oct 17 00:08:25 UTC 2018

On Oct 16, 2018, at 4:57 PM, Wayne Bouchard <web at> wrote:
> Well, simply put, the idea is that you should be able to compensate
> for a certain amount of deviation from accepted usage as long as its
> still within what the protocol allows (or can be read to allow) but
> that you yourself should act with a fairly strict interpretation. In
> others, don't be the one *causing* the problems...

Indeed. To give a TCP example, the opening exchange is theoretically SYN, SYN ACK, ACK. A common case is that it is SYN, SYN ACK, data, either because the ACK got lost, or because someone cut a corner. The issue is to note that the SYN might have been duplicated in flight, and the receiver might therefore have the appearance of two sessions. Which one? The ACK (or data segment) - any segment within the sessions - clarifies that. So, if there is a minor protocol violation but the intent it clear, follow the intent.

The alternative version of the Robustness Principle: "S**t happens; deal with it."

Says someone who has implemented such things...
Victorious warriors win first and then go to war,
Defeated warriors go to war first and then seek to win.
     Sun Tzu

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