Decentralized online social networks (DOSNs) have recently emerged as a viable solution to preserve the users' privacy and ensure higher users' control over the contents they publish. However, little is known about the backlashes that the decentralized organization and management of these platforms may have on the overlaid social network. This paper fills the gap. Specifically, we investigate how a decentralized architecture based on distributed servers impacts the structure of the users' neighborhood and their ego-networks. Our analysis relies on social data gathered from the decentralized micro-blogging platform Mastodon, the newest and fastest-growing decentralized alternative to Twitter. Our findings highlight that the social network supported by each server, namely instance, has a specific footprint in terms of degree distribution and clustered structure of the ego-networks of its members. Further, how users connect to people hosted in other instances is heavily bound by the server they are in. Moreover, users who tend to establish relationships in outer instances prefer to use a bunch of servers. Finally, we show that the ego-networks of the users are more clustered within the instance boundary, i.e. triangles are more likely to form among members of the same instance. All these findings suggest that the decentralization drives the social network to a structure that can be potentially very different from the usual one typical of centralized online social networks. Thus, the architecture of a DOSN is a factor developers and researchers should take into account when designing this kind of social platforms.

In today's technology-assisted society, social interactions may be expressed through a variety of techno-communication channels, including online social networks, email and mobile phones (calls, text messages). Consequently, a clear grasp of human behavior through the diverse communication media is considered a key factor in understanding the formation of the today's information society. So far, all previous research on user communication behavior has focused on a sole communication activity. In this paper we move forward another step on this research path by performing a multidimensional study of human sociality as an expression of the use of mobile phones. The paper focuses on user temporal communication behavior in the interplay between the two complementary communication media, text messages and phone calls, that represent the bi-dimensional scenario of analysis. Our study provides a theoretical framework for analyzing multidimensional bursts as the most general burst category, that includes one-dimensional bursts as the simplest case, and offers empirical evidence of their nature by following the combined phone call/text message communication patterns of approximately one million people over three-month period. This quantitative approach enables the design of a generative model rooted in the three most significant features of the multidimensional burst - the number of dimensions, prevalence and interleaving degree - able to reproduce the main media usage attitude. The other findings of the paper include a novel multidimensional burst detection algorithm and an insight analysis of the human media selection process.

The growing number of mobile devices equipped with a wireless interface and the end-user trend to shift toward wireless technology is opening new possibilities for networking. In particular, opportunistic communication embodies a feasible solution for environments with scarce or costly infrastructure-based connectivity. In this context we provide a delay-tolerant solution that provides service opportunistic connectivity. Our approach follows the Delay/Disruption Tolerant Network (DTN) paradigm by implementing a store-carry-and-forward communication model among mobile users and buses, the latter embodying carrier entities. A user can delegate the carrier a request which involves Internet access. This request is then forwarded to the bus station's Internet Gateway (IG) in an opportunistic fashion, including both data muling and multi-hop transmission through other buses. Once the request is served at the bus station's IG, the result is opportunistically sent back toward the bus line where the user expects the result. In this paper we present our idea and discuss results obtained through simulations in a realistic urban scenario.