I found the missing 30 milliseconds!

Jay R. Ashworth jra at scfn.thpl.lib.fl.us
Tue Sep 16 21:46:26 UTC 1997

On Tue, Sep 16, 1997 at 01:01:53PM -0700, Kent W. England wrote a
treatise which identified the Rose Mary Woods of the Internet, or so he
> You can't send a packet out an interface until the entire packet has been
> received on the incoming interface. Now if we assume 1500 byte packets (the
> new de facto MTU on all modern Internet backbones) and DS-3 pipes, then it
> takes about 250 microseconds to buffer the pkt on each hop. Since the US
> internet backbone from coast to coast is about 120 hops, there's your 30
> milliseconds and Bob's your uncle.
> Did I do the arithmetic right?

I think you did the math right...

but isn't that what "cut-through" switching is all about?  Sending the
packet out before you're done getting it in?

-- jra
Jay R. Ashworth                                                jra at baylink.com
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