Figure 7.1: Number of Segments versus Size of Data Transfer
Figure 7.1 shows the results from testing for the number of segments for T/TCP versus number of segments for normal TCP/IP. It is immediately obvious that there is a saving of on average five packets. These five packets are accounted for in the three way handshake and the packets that are sent to close a connection. Discrepancies in the path of the graph are caused by lost packets and retransmissions.
One interesting point about the average number of segments when using a TCP client and a T/TCP server, there is still a saving of one segment. A normal TCP transaction requires 9 segments, but because the server was using T/TCP, the FIN segment was piggybacked on the final data segment, reducing the number of segments by one. This demonstrates that there is still a reduction in segments even if just one side is T/TCP aware.
Figure 7.2 shows the percentage savings for the different packet sizes. The number of packets saved remains fairly constant, but because there is an increase in the number of packets being exchanged, there is a decrease in the overall savings. This indicates that T/TCP is more beneficial to small data exchanges.
Figure 7.2: Percentage Savings per Size of Data Transfer
The above test results were obtained from two hosts on the same intranet. For comparison purposes, the tests were repeated for a host on the internet, www.elite.net was chosen as the host. Requests were sent to the web server for similar sized data. Figure 7.3 shows these results. This graph is not as smooth as the graph seen in figure 7.1 due to a higher percentage of packets being lost and retransmitted.
Figure 7.3: Number of Segments versus Size of Data Transfer for Internet
Host