Complexity and diversity of Internet traffic are constantly growing. Networking researchers become aware of the need to constantly monitor and reevaluate their assumptions in order to ensure that the conceptual models correctly represent reality. Using the dataset collected by NetTurbo from three different bidirectional OC-48 links in metro area networks at the two biggest ISPs of China, this paper carefully investigates the self-similar characteristics of traffic from different aspects. In contrast to the previous results which have been widely accepted, this paper shows that for the aggregated traffic and the TCP and UDP traffic whether the self-similarity exists is uncertain. Further, break down by the application category, only the traditional and uncategorized traffic are self-similar while the others are not. However, on the view of the individual application of each category, it seems that traffic of every application exhibits self-similarity. To the best of our knowledge, this paper firstly provides the experimental evidence showing that aggregating different groups of self-similar traffic series could generate a traffic series which is either self-similar or non-self-similar.