TCP Rate Help

The TCP Rate tool allows you to examine TCP/IP data transfer behavior more closely. Specify a URL pointing to some web content (http://) and press Test to begin retreiving data. The TCP Rate tool will try to retrieve the URL content repeatedly allowing you to see the effect of tuning changes on TCP data transfer. Alternatively, you can leave the "Test URL" field empty to monitor your own data transfer tools. Notice that parameter changes affect subsequent TCP connections, so you may need to restart a file transfer in progress to see the effect of tuning.

Depending on your connection bandwidth, the TCP Rate tool can transfer a lot of data so please choose your target carefully (preferably one of your own servers) or keep your tuning sessions as short as possible. Most smaller websites including pay for network bandwidth beyond a limited budget. It's best to choose pages with lots of text content that will fill many segments. or have worked well in our testing.

The plot on the upper right side of the window shows TCP Data transferred in bytes per second (no TCP or IP headers, and no UDP or ICMP datagrams). Green bars in the upper half show receive data while red bars in the lower half show transmit data if any. A purple line shows a 10 second running average. Blue bars indicate duplicate or retransmit data. The plot shifts left each second to show the last minute of data transfer.

Orange bars show the number of TCP control packets that do not contain any data such as SYN, ACK, FIN, keep alive or probe. Typically these packet consist of a 20-byte IP header, but only the number of such packets is plotted, not their size.

The scale for the vertical axis can be either linear or base-2 logarithmic and adjusts automatically so the data will fit. For logarithmic, each succesive vertical increment represents twice as much data. The marks on the vertical axis are spaced two increments apart corresponding to four times as much data (0, 2, 8, 32, 128, 512, 2K, 8K, 32K...). By using a logarithmic scale, small duplicate or retransmit segments are easily visible along side large data transfers. The shorter segment is overlayed on top of the longer one making it easy to see even minor network inefficiency.

A check box by the bottom left of the plot area selects a linear vertical scale for visually comparing the relative size of plot segments.

The window also includes counters that report the following:

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