perfSONAR User Q&A and Other Discussion

[Jared Schlemmer <>]

We just turned up a new network endpoint that connects to an existing 
aggregation site via a 1gb AT&T VPLS connection and I’m seeing some 
interesting performance results. The sites are Monterey Bay and Sunnyvale, 
CA. Tests from Sunnyvale to Monterey Bay are good, but the reverse direction, 
Monterey Bay toward Sunnyvale, I see this:

Connecting to host port 5332
[ 16] local port 58534 connected to port 5332
[ ID] Interval                 Transfer        Bitrate              Retr  Cwnd
[ 16]   0.00-1.00   sec   110 MBytes  0.92 Gbits/sec    0   1.16 MBytes       
[ 16]   1.00-2.00   sec   113 MBytes  0.95 Gbits/sec   64    553 KBytes       
[ 16]   2.00-3.00   sec   111 MBytes  0.93 Gbits/sec   32    498 KBytes       
[ 16]   3.00-4.00   sec   112 MBytes  0.94 Gbits/sec   32    434 KBytes       
[ 16]   4.00-5.00   sec   112 MBytes  0.94 Gbits/sec   32    362 KBytes       
[ 16]   5.00-6.00   sec   112 MBytes  0.94 Gbits/sec    0    669 KBytes       
[ 16]   6.00-7.00   sec   112 MBytes  0.94 Gbits/sec   32    622 KBytes       
[ 16]   7.00-8.00   sec   111 MBytes  0.93 Gbits/sec   32    574 KBytes       
[ 16]   8.00-9.00   sec   112 MBytes  0.94 Gbits/sec   32    519 KBytes       
[ 16]   9.00-10.00  sec   112 MBytes  0.94 Gbits/sec   32    458 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[ 16]   0.00-10.00  sec  1.09 GBytes  0.94 Gbits/sec  288             sender
[ 16]   0.00-10.00  sec  1.09 GBytes  0.93 Gbits/sec                  receiver

My questions are, a) how is it that we see retries and such a small window 
size and yet still get near line-rate throughput, and b) what is the real 
world impact of a test like this? Users at the Monterey site are reporting 
wildly varying performance out to the internet. 

There are likely a lot of factors going on here, but I wanted to focus just 
on the testing between these two sites through the AT&T cloud. Any insights, 
theories or suggestions would be much appreciated. Thanks,


Jared Schlemmer
Network Engineer, GlobalNOC at Indiana University

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