A number of studies on traffic measurement from a variety of working networks have demonstrated that actual network traffic is self-similar in nature (traffic observed at different time resolutions has similar statistical properties, and this phenomenon cannot be modeled well by traditional traffic models such as Poisson and Markovian processes). The causes of self-similarity of network traffic must be identified because understanding the nature of network traffic is critical to properly design and implement computer networks and network services. In this paper, the effects of the transmission control protocol congestion-control mechanism on traffic self-similarity are investigated.