I found the missing 30 milliseconds!

Craig A. Huegen c-huegen at quadrunner.com
Tue Sep 16 20:41:14 UTC 1997

On Tue, 16 Sep 1997, Kent W. England wrote:

That's all well and everything, but I'll put $5 down that says everyone
here used standard 56-byte ICMP payload for their pings, which makes the
packet less than 100 bytes total.


==>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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