GUI: TCP flow direction, duration, and throughput

In the ByteBlower GUI, the user does not configure HTTP clients and servers directly. Instead, the user defines a TCP flow in the Flow View, whose traffic flows between a source port and a destination port.

Note that in the background, an HTTP client and HTTP server are still created. Based on the HTTP Request Method field in the TCP Flow Template view (AUTO, GET, or PUT), the client and server are created on the correct port. This ensures the bulk of data flows from the configured source port to the destination port.

Consider two ports HTTP server and HTTP client.

The default case (AUTO) normally results in the GET situation. However, if the configured source port is a NATted port (as configured in the Port view), GET is likely not to work. In this case, the SYN message would flow from the destination port towards the source port. If the source port is behind a NATbox however, it will typically drop that SYN message. That's why ByteBlower switches to PUT in that case.

In the report, the duration and average throughput results are presented to the user. Their values are based on the API calls described above.

• Timing and throughput values are always measured on the receiving side. This is the HTTP client for GET and the HTTP server for PUT.
• Duration is based on Time.Data.Packet.First and Time.Data.Packet.Last.
• Throughput is based on AverageThroughput.

This results in the following formulas:

In addition, the report also includes more detailed Timing information. An example is shown below.

• Time To First Byte (TTF): Is the time it takes for the first TCP payload byte to reach the client. This matches the T2 timestamps mentioned earlier.
• Minimum RTT: Is the shortest round-trip time throughout the lifetime of the session.
• Average RTT: The average round-trip time throughout, again over the whole lifetime of the TCP session.
• Maximum RTT: Finally, the longest round-trip time encountered during the session.

The above statistics are over the whole lifetime of the TCP flow. Intermediate results are shown in the TCP graphs. An example is shown below, more information about this graph is available in this KB article.