Networking for challenged environments, or Delay- and Disruption-Tolerant Networking as it is now most commonly referred to, has attracted great attention in the past few years by the networking research community. Connectivity disruptions, limited network capacity, energy and storage constraints of the participating, mobile devices and the arbitrary movement of nodes are only a few of the challenges that the protocol stack has to deal with. Clearly, current Internet protocols (i.e., the TCP/IP protocol stack) suffer and can fail under such conditions. In this paper, we initially give the DTN Problem Statement; we contend that not all applications have the same requirements from the system and hence, equal (blind) treatment of all data packets will result in reduced network efficiency. Based on that we propose a Design Position for DTN protocols, which states that protocol design has to be done proactively, on the basis of the application’s requirements. We then survey the most recent contributions on the whole spectrum of Delay- and Disruption-Tolerant Networking, from the architectural and the application point of view down to the transport- and the network-layer of the emerging DTN protocol stack. We find that although not explicitly mentioned

Abstract. Solutions for data dissemination in traditional peer-to-peer networks are not suitable for mobile peer-to-peer networks due to the special characteristics of mobile environments, particularly highly variable connectivity, and disconnection. Mobile peer-to-peer data dissemination over Delay Tolerant Networks (DTNs) is a promising paradigm since they can tolerate frequent and long network partitions. DTNs exploit collaborative data storage and node mobility to bridge disconnected nodes and enable communication between them. Recent studies based on real world traces reveal that node mobility exhibits certain patterns influenced by the centrality and the regularity of nodes in the network. Many existing routing algorithms for DTNs exploit only one of the mobility properties, e.g., only node centrality, or only node regularity to route messages from a source node to a destination node. In this paper, we present an adaptive routing algorithm that exploits either centrality or regularity according to the situation to achieve the best possible routing performance in delay tolerant networks. Simulations performed on real mobility traces show that our algorithm outperforms the existing routing algorithms that utilize only one mobility property.

Web-based social networking services enable people who share interests to find each other and collaborate in online and offline social activities. Thanks to the widespread popularity of networked handheld devices, constantly carried by members of the public throughout their daily activities, new possibilities of collaboration and interaction are emerging, among people who are not only socially close to each other, but also in physical proximity. However, a challenge arises as to how to enable people with similar interests to find each other, so to fulfill their social activities anywhere and anytime, while constantly moving around. In this paper, we present ADESSO, a semi-distributed directory and matching service that supports opportunistic social networking in delay tolerant networks. ADESSO consists of a set of self-organising brokers, automatically elected based on their mobility patterns. Users offload their requests to perform social activities onto brokers upon encounters; brokers then collaborate, by means of either request exchanges or broker fusion, in order to match activities in a way that satisfies users ’ social preferences. Preliminary performance evaluation, conducted using real human mobility traces and social networks, shows that ADESSO generates matches that highly satisfy users’ preferences, entailing only a small overhead.

Abstract—Delay tolerant networks (DTNs) are wireless mobile networks in which the existence of an end-to-end path from the source to the destination of a message cannot be guaranteed. This makes message delivery as one of the major challenges in DTNs. Recent studies based on real world traces show that nodes in DTNs exhibit mobility properties such as their centrality in the network or regularity patterns. To the best of our knowledge, existing routing algorithms exploit only some of the nodes mobility properties (e.g., only nodes centrality, or only nodes regularity) while excluding the others. We present in this paper the first dynamic routing algorithm in DTNs that exploits the most appropriate mobility property (among which node centrality and regularity) at the specific time and location. Our algorithm dynamically learns nodes mobility properties in order to appropriately select the best route to the destination on a per-node and per-situation basis. Simulations performed on real mobility traces show that our algorithm has a better delivery ratio and a lower overhead than existing state-of-the-art routing algorithms that rely on a single mobility property. Index Terms—delay tolerant networks, mobility, routing, centrality, regularity.