Qcheck is a free network performance utility by NetIQ. It's free because it's a subset of NetIQ's more comprehensive network performance analysis tools.  NetIQ hopes you like what you see and will want to buy the more expensive (and fully featured) stuff. You can download it from here.

Qcheck has a very intuitive interface and has lots of good on-line help, which you can view here.

The Qcheck help pages accessed by the link above are normally installed on your computer when you install Qcheck. They are provided here as a convenience and are Copyright © NetIQ Corporation, 1995-2001. All rights reserved.

We use the following Qcheck tests in our product evaluations:

TCP Response Time:
This test is very similar to "ping" and tells you how long it takes another machine to respond.  This measurement is commonly referred to as "lag" or "latency".  We use 10 iterations of 100 byte data size unless otherwise noted.

TCP Throughput:
Tests the time it takes to transfer a block of data from one computer to another.  Sometimes called "bandwidth", it's a measure of your network's raw transfer speed.  We use 1000kByte test data size unless otherwise noted

UDP Streaming: [description from Qcheck Help file]
"Streaming tests, like multimedia applications, send data without acknowledgments. In Qcheck, streaming uses the connectionless protocols IPX or UDP. Qcheck's streaming tests emulate the behavior of applications that use streaming, such as Voice over IP and video broadcasts. This test indicates how much bandwidth your multimedia traffic might need and makes it easy for you to compare the speed of your network hardware with the actual data rate your network is achieving."

We run this test as a way to check how well devices can keep up with non TCP data and as a way to test the efficiency of a router.  We usually run a 10 second test, but the rate depends on what the device under test will bear and is noted in the review.