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Bulk Throughput Measurements - NERSC


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SLAC to NERSC and NERSC to SLAC

On October 12, 2001, measurements were made between pharlap.slac.stanford.edu and pdsfsu00.nersc.gov located at NERSC in Oakland California.  Pharlap was a Sun E4500 with 6*336MHz cpus and a GE interface running Solaris 5.8. SLAC had a 155Mbps link to ESnet. Pdsfsu00  was a 16*336MHz Sun cpu running Solaris 5.6 with a GE interface and connected to ESnet at 2.5Gbps.  The ping response from SLAC to SoX was min/avg/max (std) = 2.82/3.71/71 (1.2) msec. The traceroute from SLAC to NERSC shows the route is via ESnet and is short. Trying to run a traceroute from pdsfsu00 resulted in  icmp socket: Permission denied. The pipechar from SLAC to NERSC was also recorded. The window buffer sizes on pharlap are shown below:
ndd /dev/tcp tcp_max_buf = 4194304
;ndd /dev/tcp tcp_cwnd_max = 2097152
;ndd /dev/tcp tcp_xmit_hiwat = 16384
;ndd /dev/tcp tcp_recv_hiwat = 24576

The window buffer sizes on gigatcp1 were as shown below:
ndd /dev/tcp tcp_max_buf = 4194304
;ndd /dev/tcp tcp_cwnd_max = 2097152
;ndd /dev/tcp tcp_xmit_hiwat = 16384
;ndd /dev/tcp tcp_recv_hiwat = 24576

The performances (seen below) are  asymmetric, throughput being ~ 50%  better from SLAC to NERSC than from NERSC to SLAC. This is interesting since the machines at both ends are very similar with similar window configurations. The measurements were repeated at different times with similar results. We used top to identify that both machines were unloaded (typically top and iperf were the top processes and were using < 1% of the cpu). The maxima (i.e. the top 10% of measured throughputs) from SLAC to NERSC is about 94Mbps, and from NERSC to SLAC is 58Mbps.
 

On November 6th 2001 Pharlap received access to ESnet via an OC12 (622Mbps) link. We therefore remeasured the iperf throughputs on November 7, '01. the results are shown below. The maxima are seen to have increased roughly by a factor of 4.


Created October 6, 2001, last update October 12, 2001.
Comments to iepm-l@slac.stanford.edu