Abstract:Delay/Disruption Tolerant Networks (DTNs), which are based on an overlay protocol and the store-carry-forward paradigm, are considered as a promising solution to cope with the challenges imposed by space environment, such as long delay, intermittent connectivity, etc. Contact Graph Routing (CGR) is a dynamic routing algorithm which can compute routes by taking advantage of a priori knowledge of the space DTN topology. In this paper, the basic principles and algorithm procedures of the CGR are introduced, and the definitions of the associated terminologies and corresponding formulas are given, firstly. Then, the existing enhancements of the CGR are summarized in terms of routing loops avoidance, computational efficiency, routing accuracy, congestion control, opportunistic extension, and exception handling. Next, the representative real test experiments that have been conducted to evaluate the applicability of the DTN protocol stack and CGR, are outlined, and the performance differences between the CGR algorithm and the multi-layered satellite routing algorithm (MLSR) are evaluated by GEO/MEO/LEO satellite network simulation. Finally, the future developments of CGR are given, including the integration of CGR-extension block (CGR-EB) and cache-CGR (C-CGR), opportunistic CGR, CGR extension to large network, CGR-Quality of service (QoS) provision, enhancement of contact plan description method, etc.

Abstract:The delay tolerant network has been extensively studied and applied in recent years. When there is continuing and stable end-to-end path between the source node and the destination node in DTN, the traditional TCP/IP based network routing protocols cannot be applied to Delay/Disruption Tolerant Network. The storage-forward policy is used for message transmission. The performance of DTN routing protocols is influenced by the link existent time, buffer size of the nodes, and the mobility mode of the network. This paper discusses the study of DTN routing protocols, compare their performance, and highlight the future trends of DTN routing protocols.

Abstract:In the recent years, as a new emerging network architecture, Delay/Disruption Tolerant Networks (DTNs) have received extensive attention and are widely investigated. Since the major application scenarios of DTN are extremely particular routing protocols designed for the traditional networks are not suitable for DTN. Therefore, numerous routing protocols have been proposed for DTN. In this paper, the formulation issues of DTN routing protocols are firstly studied, and the classification concerns are then proposed for those protocols. Thereafter, this paper focuses on analyzing and comparing existing representative DTN routing protocols. Finally, current research status and the existing problems about DTN routing protocols are summarized, the key issues and future trends in DTN routing are pointed out.

Abstract:As newly proposed end-to-end, store-and-forward networks, delay and disruption tolerant networks (DTN) are characterized by intermittent connectivity, frequent partitions, extremely high latency, asymmetric data rates, high error rates, heterogeneous interconnection, etc. Hence, traditional routing protocols for Internet, mobile ad hoc networks and wireless sensor networks, are difficult to be applied efficiently in DTN scenarios, and routing in DTN faces many new challenges. After briefly describing the fundamental characteristics of DTN and the major challenges in designing routing protocols, the metrics used to evaluate the DTN routing protocols are proposed. Next, research on routing protocols for DTN is comprehensively summarized and deeply analyzed in this paper, including unicast routing, multicast routing, and anycast routing. Finally, the main routing protocols are compared, and the open issues for the future research are also pointed out to motivate new research and development in the field of DTN.