Performing research on live network traffic requires the traffic to be well documented and described. The results of such research are heavily dependent on the particular network. This paper presents a study of network characteristics, which can be used to describe the behaviour of a network. We propose a number of characteristics that can be collected from the networks and evaluate them on five different networks of Masaryk University. The proposed characteristics cover IP, transport and application layers of the network traffic. Moreover, they reflect strong day-night and weekday patterns that are present in most of the networks. Variation in the characteristics between the networks indicates that they can be used for the description and differentiation of the networks. Furthermore, a weak correlation between the chosen characteristics implies their independence and contribution to network description.