Thanks to remote access to a laptop in the ESTEC LAN (contact MarcoMarletta for an account) we have some new results in the AsymmetricThroughput case. The results seem to suggest that there is no performance problem at the current location where the laptop is attached.

The laptop has a 100Mbit/s full-duplex access-link and we can achieve around 90Mbit/s upload speed to ndt.switch.ch and around 65-70Mbit/s download speed from ndt.switch.ch using iperf with a single-session tcp. (I suppose this is due to other traffic in that specific vlan the laptop is in).

What we observed is that you can not set a default send window for TCP in Windows XP so you will end up with a 64K default window which will lead to around 20Mbit/s upload speed limitation as observed in other tests before. However when using an application which uses setsockopt to set the buffers manually to 512K (like in this case iperf) we were able to push it to 90Mbit/s.

It is still unclear to me why the test which was conducted by Marco on Monday only resulted in around 200Kbit/s upload speed and 18.81Mbit/s; Talking with Marco about this it seems that nothing has changed since then.

Looking at packet traces of both sides of the connection during a web100 ndt test from the laptop at ESTEC (195.169.140.254) to ndt.switch.ch you can see that probably there are some small packets being re-ordered. (TCP DUP acks without retransmission). Else, there is not much to see. Looks pretty nice and steady... Data rate is around 20mbit/s in one direction and 65mbit/s in the other. Btw that is with the standard 64k send buffer on the laptop (java applet) side and a large receive and send buffer at ndt.switch.ch (8MB/8MB)

-- ChrisWelti - 02 May 2005