Re: Tails and Dogs


CERF@USC-ISI.ARPA
15 Feb 1986 09:58-EST


Mike,

There was an old joke once about crossing an onion with a donkey and getting
a piece of ass that brought tears to your eyes. I suppose one might say the
same thing about crossing architectures with onions, although I am not sure
what the connotations are.

I was not advocating that the TCP level of flow control be used, somehow,
to protect the network - just the opposite. The point is that the network
(lower) layer must have mechanisms to protect its resources DESPITE the
presence of the higher level end/end flow control.

This does NOT, however, mean that one should design systems by deliberately
being blind to how things work. John Nagle's recent RFC's and Dave Mills'
work on tiny pipes/flow control algorithms are manifestations of the Jack
Haverty school of engineering: "the smarter you are about the environment,
the better you can tune the system to give optimum performance."

The hard line to draw or engineering judgement to make is when to
deliberately ignore specific information or not rely on it to achieve
greater generality, but probably at the cost of poorer performance.
Much of the initial INTERNET design deliberately took the latter approach
in the interest of bringing an experimental facility into being from
which we could learn in what ways it made sense to be "smart."

Hope this makes my point a bit more clearly.

Vint



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