Mobility is the most important component in mobile ad-hoc networks and delay-tolerant networks. We first investigate numerous GPS mobility traces of human mobile nodes and observe super-diffusive behavior in all GPS traces, which is characterized by a 'faster-than-linear' growth rate of the mean square displacement of a mobile node. We then investigate a large amount of access point based traces, and develop a theoretical framework built upon continuous time random walk formalism, in which one can identify the degree of diffusive behavior of mobile nodes even under possibly heavy-tailed pause time distribution, as in the case of reality. We study existing synthetic models and trace based models in term of the capability of producing various degrees of diffusive behavior, and use a set of Levy walk models due to its simplicity and flexibility. In addition, we show that diffusive properties make a huge impact on contact-based metrics and the performance of routing protocols in various scenarios. Our work in this paper thus suggests that the diffusive behavior of mobile nodes should be correctly captured and taken into account for the design and comparison study of network protocols.