On Tue, 27 Jun 2000, Alex wrote:
Hmm..
err, throughput is unaffected by distance.
The bandwidth-delay product on the 200 mile OC12 is 622E6 * 2*(200*5280E-9) == 1313007 bits == 160 kbyte (assuming symmetric route over the fibre, doubled to give RTT). Most TCP implementations ship and run with default maximum transmit/receive windows that are much smaller than this (e.g. a default 16kbyte window would give a maximum theoretical throughput on a single, monstrous, pipe-filling TCP session of 62,060,606 bit/s on the 200 mile OC12, but 124,121,212,121 bit/s on the .1 mile OC12 -- where it would fill the pipe at 622M (window size/RTT, RTT = 2*{0.1, 200}*5280E-9). Hence in the (naturally entirely common, see it every day) case where you have colocated, TCP-speaking devices at each end of your OC12 that are capable of shifting data at those kinds of speeds and which have their maximum TCP windows set way too small, and ignoring all delays due to queueing, TTL-decrementing and checksum calculating, encapsulation overhead and transmission framing delays, the .1 mile OC12 is about 560Mbit/s faster than the 200 mile OC12. You should say "aggregate throughput for a typically large number of concurrent sessions" if you want to avoid tempting irritating pedants out of their caves :)
On Tue, 27 Jun 2000 Valdis.Kletnieks@vt.edu wrote:
On Tue, 27 Jun 2000 19:56:08 EDT, Alex said:
is a .1 mile OC12 faster than a 200 mile OC12?
Yes, by 200 * 5,280 nanoseconds. Grace Hopper said so. ;)