I've used QCheck (freeware) for testing response time, TCP and UDP performance, and packet loss. Works well. You need to install the enpoint on the target machine. Check out: http://www.ixiacom.com/products/performance_applications/pa_display.php?skey =pa_q_check -Mike McSpedon Arrow Global Data Communications -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of Alex Bligh Sent: Friday, October 15, 2004 8:25 AM To: Iljitsch van Beijnum; Joe Shen Cc: NANGO; Alex Bligh Subject: Re: why upload with adsl is faster than 100M ethernet ? <snip> I can't remember what the tool is now, but there used to be a tool which worked like ping but sent a udp stream at a given rate per second and told you about packet drops, and also allowed for some parameter to be tweaked to give stochastic variation in interpacket delay (i.e. massive jitter). You could use this to show inadequate buffering on gigabit interfaces where a 2Mb/s stream would get through, but if you wound up the jitter sufficiently, a whole burst of packets would arrive together and a gigabit interface with (deliberately) misconfigured buffers would then drop packets. Alex