Re: [TUHS] core

[jnc@mercury.lcs.mit.edu (Noel Chiappa)]

    > From: "Theodore Y. Ts'o"

    > To be fair, it's really easy to be wise to after the fact.

Right, which is why I added the caveat "seen to be such _at the time_ by some
people - who were not listened to".

    > failed protocols and designs that collapsed of their own weight because
    > architects added too much "maybe it will be useful in the future"

And there are also designs which failed because their designers were too
un-ambitious! Converting to a new system has a cost, and if the _benefits_
(which more or less has to mean new capabilities) of the new thing don't
outweigh the costs of conversion, it too will be a failure.

    > Sometimes having architects being successful to add their "vision" to a
    > product can be worst thing that ever happened

A successful architect has to pay _very_ close attention to both the 'here and
now' (it has to be viable for contemporary use, on contemporary hardware, with
contemporary resources), and also the future (it has to have 'room to grow').

It's a fine edge to balance on - but for an architecture to be a great
success, it _has_ to be done.

    > The problem is it's hard to figure out in advance which is poor vision
    > versus brilliant engineering to cut down the design so that it is "as
    > simple as possible", but nevertheless, "as complex as necessary".
      
Absolutely. But it can be done. Let's look (as an example) at that IPv3->IPv4
addressing decision.

One of two things was going to be true of the 'Internet' (that name didn't
exist then, but it's a convenient tag): i) It was going to be a failure (in
which case, it probably didn't matter what was done, or ii) it was going to be
a success, in which case that 32-bit field was clearly going to be a crippling
problem.

With that in hand, there was no excuse for that decision.

I understand why they ripped out variable-length addresses (I was just about
to start writing router code, and I know how hard it would have been), but in
light of the analysis immediately above, there was no excuse for looking
_only_ at the here and now, and not _also_ looking to the future.

	Noel