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From: Jon D. <jd...@nc...> - 2004-02-23 23:01:11
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On Mon, Feb 23, 2004 at 06:46:30PM +0100, ono...@vi... wrote: > Hi all! > > Could someone explain why Iperf really starts dropping packets? > > I mean, selecting the UDP mode, setting a UDP bandwidth value and the > number of bytes to be transmitted, why does Iperf show losses for higher > values of the UDP bandwdith rate? > > Is it a matter of CPU load or something related with the buffer sizes? Iperf using UDP doesn't drop packets per se, rather it will blindly transmit at the specified rate and if there is contention for resources somewhere in the system the data will be lost. Often it is CPU utilization that is the culprit. What is the CPU utilization you see during the test? Using larger buffers may help this since there will be less overhead. The other common cause of lost data with a UDP test is loss somewhere in the network. How are the two systems interconnected? Jon -- Jon Dugan | Senior Network Engineer, NCSA Network Research jd...@nc... | 269 CAB, 605 E Springfield, Champaign, IL 61820 217-244-7715 | http://www.ncsa.uiuc.edu/~jdugan/ |