If memory serves me right, Kaliaperumal, Rajesh wrote: > Hi Bruce, > Single stream was pretty low and then I started trying multiple > streams. I am expecting a throughput of the order of 70-100Mbps (my ISP DL > being the limiting factor).
Hmmm. I don't have any good explanation off-hand. The only two thoughts I can think of right now are: 1) the IPsec tunnel and MSS manipulation are unusual features of the path, and 2) that's a fairly old version of iperf3. I'm not sure if either of those are a factor, just saying they stand out to me. Note that using multiple streams isn't necessarily going to scale the throughput linearly. Bruce. > On 5/9/18, 4:02 PM, "Bruce A. Mah" <[email protected]> wrote: > > If memory serves me right, Kaliaperumal, Rajesh wrote: > > Hi all, > > > > > > > > Iperf version – iperf 3.1.3 > > > > > > > > My set up: iperf server (GCE) <=> Gateway VM (GCE) <=> IPsec server > > (GCE) <=> WAN <=> Laptop with IPSec Client > > > > > > > > *My test:* > > > > Server – /iperf3 -s / > > > > Client – /iperf3 -c <server ip> -P 15 -R -w 768k/ > > > > Due to IPsec header, my Gateway VM modifies the MSS size of the > > SYN-SYN/ACK message so that the TCP segments are not fragmented after > > IPSec ESP encryption. > > > > > > > > *My Observation:* > > > > When I perform a downlink test by using the “-R” option at the iperf > > client side, my throughput has a lot of variation and quickly drops to 1 > > or 2 Mbps. In other words, the iPerf server reduces the rate at which it > > pumps data. There are no packet drops on other VMs in my setup. > > > > > > > > I want to understand how iperf server determines the rate at which it > > has to pump data? > > With those parameters (and thank you for providing that information), > the server basically just sends data as fast as it can on the 15 TCP > connections you specified by the -P parameter. The speed at which it > can send data is governed by the TCP congestion control and flow control > algorithms. > > Of course those TCP connections will interact with each other, and any > other network traffic along the path. If the system isn't behaving in a > way that makes sense to you, might I suggest trying your experiment with > just a single TCP connection? Also, what throughput were you expecting > to get? > > Bruce. > > > >
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