On Jun 15, 2017, at 6:54 AM, John C Klensin <john-ietf(_at_)jck(_dot_)com>
wrote:
I suggest that one of the reasons the
Internet has been successful is precisely because of sensible
application of the robustness principle. Not only do things
mostly work, or at least produce sensible error messages or
warnings rather than blowing up, in the presence of small
deviations or errors, but (in recent years at least in theory)
it avoids out having to spend extra years in standards
development while we analyze every possible error and edge case
and specify what should happen. Instead, when appropriate, we
get to say, when appropriate, "this is the conforming behavior,
if you don't conform, the standard has nothing to say to you,
but you should not depend on its working". The robustness
principle is important guidance for those edge cases.
+1
Further, testing for all those edge cases becomes itself a performance burden
on operational code, amplifying the leverage of a DOS attack based on all that
excess validation.
The Postel principle helps make achieving the balance between usefulness and
correctness tractable.
Joe