I found the missing 30 milliseconds!

Kent W. England kwe at geo.net
Tue Sep 16 20:01:53 UTC 1997


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?

--Kent, ever helpful with NANOG metrication

Well, back when us old guys were young, switching delay *was* significant. 
Did I ever show you my p4200?

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