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We are currently testing some network equipment (consumer routers with 1 Gbit/s ports) with Jpef 2.0. All kinds of connection parameters are tested: wired and wireless, different wireless standards, TCP/UDP, etc.
When not specifying a TCP window size, the performance is low (300 mbit/s). If you enter a high value, the throughput is much better (900 mbit/s). Google tells that Windows uses TCP Window Scaling, there is no "standard" TCP Window size.
What should we use as the TCP Window size in Jperf?
The only option allowed on Jperf is a fixed value? – Diogo – 2012-06-05T14:01:26.893
Nope, you can manually choose a Window size. edit: yes, it is one fixed value you can enter – Robert – 2012-06-05T14:02:16.020
As far I know it is an automatic algorithm, Windows adjust this value depending on the internet speed. I will try to find the theory behind it, but I think on your case you must set a value due to the speed of the network that you are testing... – Diogo – 2012-06-05T14:07:48.773
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Tried to find a good reference, but the best one that I found was this. On my opinion Jperf leaves this value "open for edit" only because this way be a parameter important to test networks in some specific way. I mean, this should be a choice of the tester so you could find the best value for your network. I just reccomend you to read most of everything you could find about this and try to test different values until you reach the best one for you.
– Diogo – 2012-06-05T14:19:43.687Thanks! I think I have enough information for now. I'm can't accept a comment as an answer, so could you post it as an answer? – Robert – 2012-06-06T07:47:30.800
Yes, I will paste it as an asnwer. Thank you. – Diogo – 2012-06-06T11:59:02.327