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Bulk Thruput Measurements-Daresbury

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Bulk Thruput Measurements | Bulk throughput simulation | Windows vs. streams | Effect of load on RTT and loss | Bulk file transfer measurements

SLAC to Daresbury Lab (UK)

We show four measurements from SLAC to Daresbury. The first was made between 08:45 and 10:03 Thursday September 7, 2000, the second was made between 18:25 and 19:17 Thursday September 7, 2000. The utilization of the outbound SLAC ATM link to ESnet was 27Mbps (close to 100% - note the link is actually an ATM T3 link (~45Mbps), however after removing the ~20% ATM "tax" for headers etc., 3.5Mbps for an ATM PVC used for a VoIP/QoS pilot and a further 2 Mbps for an IPv6 pilot, the actual available bandwidth is between 27Mbps and 33Mbps) and 9Mbps respectively at these times. The third graph is for thruput from SLAC (pharlap.slac.stanford.edu) to Daresbury (rtlin1.dl.ac.uk) made on November 2, 2000. This was after the SLAC to ESnet link had been upgraded from the T3 link to an OC3 (155Mbps link). A slight improvement is seen. Also it is seen that the improvement with increasing window size is more noticeable. The fourth graph shows measurements made July 16, 2001. The pipechar is also available. At this time the host at DL (rtlin1.dl.ac.uk) was a 200MHz PC running Linux with a 100Mbps Ethernet which could not accept windows of > 64kBytes. The SLAC to ESnet ATM link had been upgraded to OC3 9155Mbps) from T3 (45Mbps) the week prior to making this measurement. The maximum iperf window settable for the host at Daresbury was 128kBytes. See the path characteristics measured on November 2, 2000 for more details on the route. The path characteristics identify the bottleneck to be the 10Mbps ATM PVC between JAnet and ESnet in New York.
SLAC to DL bulk thruput SLAC to DL bulk thruput SLAC to DL bulk thruput SLAC to DL Jul 2001

Daresbury Lab to SLAC

The version of iperf running on the Linux operating system at Daresbury did not support windows over 128Kbytes and also the client set a window 2 times the size requested. We adjusted to this "feature" in our measurements. The following first graph is for thruput from Daresbury (rtlin1.dl.ac.uk) to SLAC (pharlap.slac.stanford.edu) and was made on 10/16/00. The second graph measurements were made on July 25, 2001. Comparing the two graphs from SLAC to DL (above) and from DL to SLAC (below) made in July 2001, it can be seen that the maximum throughput from DL to SLAC is higher than that from SLAC to DL. The pipechar measured at this time is available. The third graph shows the asymmetry in the two throughputs as a function of the window size * streams, where
Asymmetry = (thru(SLAC>DL)-thru(DL-SLAC))/(thru(SLAC>DL)+thru(DL>SLAC))
The fourth graph shows the frequency histogram of the asymmetry. We later discovered that the rtlin1.dl.ac.uk machine running Linux 2.2 was configured to have a maximum window (/proc/sys/net/core/rmem_max and wmem_max) size of 64KBytes. So even though Iperf was reporting window sizes of > 64KB it was not using them.
DL to SLAC thruput

Sample Bulk Throughput Measurements

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Summary of Bulk Throughput Measurements


Created August 25, 2000, last update August 29, 2001.
Comments to iepm-l@slac.stanford.edu