Analysis of TCP flags in congested network

This paper proposes a new simple method for network measurement. It extracts 6-bit control flags of TCP (Transmission Control Protocol) packets. The idea is based on the unique feature of flag ratios which is discovered by our rather exhaustive search for the new indexes of network traffic. By the use of flag ratios, one can tell if the network is really congested. It is much simpler than the conventional network monitoring by a network analyzer. The well-known monitoring method is based on the utilization parameter of a communication circuit which ranges from 0% to 100%. One cannot tell the line is congested even if the factor is 100%. 100% means full utilization and does not give any further information. To calculate the real performance of the network, one should estimate the throughput of effective speed of each user. The estimation needs much calculation. Our new method tries to correlate ratios of TCP control flags and network congestion. The result shows the usefulness of this new method. This paper analyses the reason why the flag ratios show the unique feature.