Packet delay is one of the most important Internet performance metrics. Many studies indicate that long-range dependence (LRD) exits in Internet packet delay, but the scaling behavior of packet delay is very complicated. This paper analyzes the Internet round-trip time (RTT) behavior based on small-interval (10ms) measurements and finds that RTT series consist of two completely different components: spiky component and normal component. A bottleneck model is proposed to explain the phenomenon. By using detrended fluctuation analysis (DFA) method, it is found that the original RTT series don?t exhibit simplex scaling behavior, and although the spiky component accounts for a little proportion of the original RTT series, it has a great impact on the scaling behavior. After removing the spiky component, RTT series show LRD, with Hurst exponent ranging from 0.55 to 0.8.