> iperf knows only what the operating system tells it, so the answer to > this question does not depend on iperf but on the operating system. > For both UDP and TCP what the sending side reports is what has been > sent, NOT what has been received. So it can differ between the sending > and receiving side. But for TCP it cannot differ for long, because in > case of a network problem the TCP socket buffer on the sending side > will fill up and eventually block the sender.
Do I understand it right that iperf on the client site doesn't calculate the true bandwidth? Because the client sends a lot of data but it doesn't know, if the server receives this packages. Only by TCP and SCTP the client will a little bit regulate by the ACKs but it has no effect on the measurement on the client site. Is this correct or is there someting wrong, what I have written? If it correct, I get the true bandwidth only from the server site? Because there I can see all packages which have reached the server. > > To verify all this simply unplug the network cable during a test. Be > careful to unplug the cable of the *receiving* side, because some > operating systems on the sending side will brutally close all sockets > and indirectly interrupt iperf (not even giving you a chance to plug > the cable back). You can also try to change the socket buffer size > using the "-w" option. > I have unplugged the cable and I see that the bandwidth is going down. But iperf hold the connection by TCP somehow and ignores the -t option. I think that he will transmit the data outstanding data and will end after this the retransmission. > > I think there is also some additional iperf magic handshake at the end > of the test, not sure. The source code is your friend here. Yeah, I think really there are some "magic" Handshakes but nobody no which. But I have two additional questions: By UDP, I say on the client site "-t 10" what is the reason for that the server sends his report exactly after 10secs? In wireshark I can see only UDP packages, but in the meantime I think that the client transmit the configuration in the udp payload. And how the server no by all protocols if I use the -d or -r option to transmit data from server to client? It is all not really easy to understand for me. But I have thought that this question are answered in an manual, because I can't use a tool and believe the measurements if I don't know really how it works. Regards Frank ______________________________________________________ GRATIS für alle WEB.DE-Nutzer: Die maxdome Movie-FLAT! Jetzt freischalten unter http://movieflat.web.de ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Iperf-users mailing list Iperf-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/iperf-users
