On 2010.04.29 17:31, Robert Enger - NANOG wrote:
1) The capacity that a campus has into I2 or NLR is different than the BW the campus purchases from their commercial provider(s).
2) The commercial BW test sites are not optimized for speed. They do not have unlimited capacity network connections. And, they have not tuned their network stack for HS operation: notably, their OS will impose memory limits on the socket / transmit-buffer pool; so even if a receiver advertises a big window, frequently the transmitter (speed test server) will never queue enough data to fill the pipe
3) Peering capacity is not what it should be into the networks used by some of the BW test sites.
Your observation is disturbingly bleak... do you have a recommendation? ...perhaps a site with good bandwidth and a cluster of iperf(1) boxes available? :) Steve