Reliable Multicasting in Disruption Tolerant Networks

Delay Tolerant Network (DTN) is a sparse and intermittently connected mobile wireless network where reliable communication and end-to-end connectivity cannot be assured. In DTN, a node delivers messages to the destination using store and forward scheme. Messages are copied and transferred to multiple relay-nodes in order to increase the opportunity for that message to reach the intended destination. Contact is the time duration for which two or more mobile nodes encounter each other within their radio transmission ranges, and are able to transfer messages. Due to arbitrary node movement, contact time will be varied, and is unlikely to be predictable. In this paper, we propose a fuzzy decision mechanism we called “fuzzy-spray”, to improve the routing and packet transfer efficiency in DTN environment. Fuzzy-spray can reduce overall latency in DTN by intelligently selecting appropriate messages to send to the relay-node during its next contact time. It uses fuzzy logic to prioritize messages that are stored in the buffer, based only on local parameters from each message, namely forward transmission count and message size. There is no need to know a priori information about network such as node mobility model, or node-distribution across the deployed area. The simulation results show that fuzzy-spray has the best performance in terms of overall speed of delivery, and lowest average message delay compared with other existing algorithms.

In Delay Tolerant Networks (DTNs), message forwarding is a challenging open problem because of low node density and lack of global information. Most of the previous forwarding methods select a node as a relay node with the best cumulative and global ability of contacting the destination without considering the maximum message acceptable delivery latency. However, if the network is composed of several communities, the cumulatively and globally calculated forwarding metric (and not in each community) will not have suitable estimation of contact between relay node and destination. Therefore, in this paper, we introduce and evaluate a novel forwarding method, which called Community-based Contact Prediction message forwarding method (CCPMFM). The CCPMFM exploits a semi-Markov process to explain and predict the node mobility between communities. The CCPMFM selects the relay node with regard to the maximum message acceptable delivery latency. To calculate the forwarding metric, CCPMFM considers the contact patterns of each community only for the same community and not for the entire network. CCPMFM also selects the relay node with regard to maximum message acceptable delivery latency. The evaluation results show that this method improves the delivery ratio and reduces the number of message forwardings and delivery latency with respect to prevalent DTNs forwarding methods.

Delay-Tolerant Networks (DTNs) are a type of emerging networks characterized by very long delay paths and frequent network partitions. For the distinct characteristics of DTNs, routing becomes one of the most challenging open problems. Recent years numerous approaches have been presented for addressing routing issues in DTNs. This paper surveys main DTN routing strategies and gives a comparison of them with respect to the performance metrics. Specially, we summarize the cardinal mobility models and DTN simulators which are significantly important to evaluate the performance of DTN routing protocols.

Internet of Things (IoT) devices used in mining, agriculture, and environmental sensing often require Disruption Tolerant Networking (DTN) support, since end-to-end network connectivity may not always available in distributed and sparsely populated locations. Data mules such as workers or vehicles, which pass through the monitored area periodically, bridge the gap between disconnected networks. Since data dissemination often involves multiple users, and configuration updates from the Monitoring and Control Center needs to be delivered reliably to all participating IoT devices, the combination of efficient Reliable Multicast algorithms with DTN should address this problem effectively. This paper examines the current status of DTN support for multicast from different design aspect of routing protocols and summarizes some of the open issues related to the design of Reliable Multicast DTN (RMDTN) protocols for IoT.

Disruption tolerant network (DTN) refers to the type of sparse mobile ad hoc network where the nodes are connected intermittently. A common strategy to cope with intermittent network connectivity is to use multiple-copy routing for message delivery. However, the resultant replicates of messages incur significant burden on the bandwidth and storage requirements of each node. In this paper, we investigate the effect of excessive message-replications in multiple-copy routing in DTNs under communication bandwidth and buffer constraints. By modeling the message delivery process as a Markov chain, we first analytically derive the delivery latency as a function of message-replication limit for the single-message-delivery case. The performance of the multiple-message-multiple-flow case is then evaluated via extensive simulations. For the latter, we observe that there is an optimal value for the message-replication limit of each message beyond which network performance will degrade. Finally, we propose an alternative forwarding and message-dropping strategy to address the problem of unfairness found in the basic FIFO-with-blocking strategy. Our results show that the average message delivery delay can be reduced by as much as 25% with the proposed scheme.

Delay-tolerant networks consist of mobile nodes that communicate in unscheduled opportunity without network infrastructure support. When mobile nodes move in highly dynamic networks, they suffer from many challenging issues such as broken network topology and transient connectivity among nodes. In this paper, we propose a geo-routing scheme with an angle-based decision policy (GRAD) for message delivery in delay-tolerant networks. This scheme can select relay nodes in geographic proximity to perform message delivery towards a destination. After a definite number of relays, the message can be destined to a destination. Simulation results show that GRAD can attain a higher rate of successful message delivery and lower communication cost as compared with a classical Spray and Wait scheme under area-confined random waypoint and SLAW mobility patterns in delay-tolerant networks.

Wireless data communications commonly use public networks to exchange data packets. Public networks of rural area are lack of network infrastructure so it will inflict high delay for wireless communications. The rural areas are same with intermittent area that need a mechanism of data transfer to tolerate with delay. The Delay Tolerant Network (DTN) is a solution for data transmission in rural areas that have coverless TCP/IP network. DTN uses store-and-forward mechanism to send data packets from the source to the destination through intermediary nodes. DTN uses dynamic routing protocols to determine routes of data packets delivery. DTN implements a reliable routing protocol of Optimized Link State Routing (OLSR) algorithm to looking for a delivery route of data packets to the end node. The OLSR routing protocol uses MPRs node as selected nodes, which forwards the control messages of networks topology information. This could streamline the network traffic of DTN to determine the best route of delivery data packets from the sender to the receiver. This paper presents transmission of medical data from the source of the node in the rural area to the destination node through the nodes of intermediate. This telemedicine system sends medical data of patient's private data that is encrypted using Advanced Encryption System (AES) to guarantee the medical data safety. The AES encryption system takes no more than 0.4 ms for data encrypting and decrypting process.

Delay tolerant networks (DTNs) are wireless networks in which an end-to-end path for a given node pair can never exist for an extended period. It has been reported as a viable approach in launching multiple message replicas in order to increase message delivery ratio and reduce message delivery delay. This advantage, nonetheless, is at the expense of taking more buffer space at each node. The combination of custody and replication entails high buffer and bandwidth overhead. This paper investigates a new buffer management architecture for epidemic routing in DTNs, which helps each node to make a decision on which message should be forwarded or dropped. The proposed buffer management architecture is characterized by a suite of novel functional modules, including Summary Vector Exchange Module (SVEM), Networks State Estimation Module (NSEM), and Utility Calculation Module (UCM). Extensive simulation results show that the proposed buffer management architecture can achieve superb performance against its counterparts in terms of delivery ratio and delivery delay.KeywordsRoutingBuffer management

Researching on delay tolerant networks is an emerging field. Many researchers are dedicated to the approach of the routing algorithms and its applications. With sufficient energy in the core-nodes in the networks, a nested source spray and wait routing algorithm, which is ameliorated from source spray and wait routing algorithm, has been put forward in this paper. The simulation results indicate that by increasing the cost of energy consumption at the core-nodes, this routing algorithm has better performances in terms of delivery probability and the average delay.

This paper explores mobility mining to extract relevant node and network characteristics in Delay Tolerant Networks during disaster scenarios. Through mobility analysis, this paper aims to discover location hotspots and look at mobility entropy of different node groups with different roles during a disaster. In general, this paper presents a routing scheme for DTN that aims to improve the effective delivery of messages on specific geographic locations and entities. The routing scheme incorporates Area of Interest (AoI) of nodes and calculation of encounter probability in the routing decision and proposes better message management to optimize node’s memory. Simulation results show significant advantages of the proposed scheme compared to Epidemic for geographic routing and Epidemic scheme with Angle of Deviation (AoD) in terms of delivery rate, delivery latency, and message overhead.

As the percentage of Vehicles are increasing on roads, Vehicular Ad-hoc network have reached to a significant interest of the researcher in recent times. V2V network and V2I are prominent as an organized solution for attaining safety for moving vehicles on road and transmitting data for a secure journey while driving and transferring data in the form of message from one vehicle to other. VDTN is a kind of Delay Tolerant Networks (DTNs), to provide reliable and efficient communications. Various routing protocols have been used previously in VDTN to enhance the performance of the network in terms of forwarding information in the form of messages to their preferred locations. In this paper, we introduce a novel protocol called Buffer-Efficient Disruption Tolerant Routing Protocol (BEDTRP) to improve delivery delay, overhead and latency. This protocol significantly improves the communication performance such as delivery ratio and overhead in terms of increasing buffer size and bandwidth. Evaluation results show that the proposed method BEDTRP achieves high bandwidth utilization performance to provide better delivery ratio, lower delivery delay, and low overhead against buffer changes. We used ns-2 network simulator to implement Delay tolerant network protocol.

In intermittently connected delay tolerant wireless sensor networks, sensor data generated at sensor nodes should be delivered to a sink node using opportunistic contacts between intermittently connected nodes. Since there is no stable end-to-end routing path from a source node to a sink node in intermittently connected network, an opportunistic routing protocol to deliver sensor data efficiently is needed. In this paper, an improved opportunistic routing protocol is proposed, where both current delivery predictability and maximum delivery predictability are used together to decide whether sensor data should be forwarded or not to a contact node. The proposed protocol can reduce buffer overflow and thus increase the delivery ratio, which is one of the most important performance measures in delay tolerant wireless sensor networks. The performance of the proposed routing protocol is compared with that of PRoPHET protocol and FREAK protocol, by varying buffer sizes and the number of nodes, in terms of delivery ratio, overhead ratio, and delivery latency. Performance analysis results show that the proposed protocol has better delivery ratio, overhead ratio, and delivery latency than the PRoPHET protocol and FREAK protocol have, in most considered parameter values, with appropriate selection of message dissemination thresholds.

In challenged networks, such as opportunistic networks or Delay Tolerant Networks (DTNs), due to frequent network partition an end-to-end connection between source and destination may not always be possible due to nodes move unpredictably with high speeds. For such type of networks, traditional routing protocols fails to transmit and also no guarantee on delivery of data to specified destination because these protocols deliver data definitely whenever there exists continuous end-to-end connectivity between source and destination over time. To provide efficient routing for such networks replication based routing schemes were proposed to achieve higher delivery probability. Unlike Internet protocols, Delay Tolerant Networks routing protocols follow store-carryforward mechanism to reduce packets dropping probability, tolerate delays and improve delivery performance in terms of delivery ratio and delivery latency. This paper defines the most efficient replication based routing protocols such as epidemic, PROPHET, spray and wait and Encounter based routing. This paper also explains how message TTL, buffer sizes and area of grid impact performance of replication based routing protocol in terms of delivery ratio and Average latency and overhead ratio.

Delay tolerant networks (DTNs) are mobile wireless networks that are characterized by frequent partitions and potentially long message delivery delays. Such networks have the potential for use in important application environments where en- ergy sources are limited. Therefore, efficient power management mechanisms are necessary to allow these networks to operate over a long period of time. In this paper, we leverage the observation that many DTNs are characterized by sparse connectivity, pro- viding the opportunity to save energy by aggressively disabling node radios (sleeping). The major challenge is to balance sleeping periods with wake-up periods so that valuable and infrequent communication opportunities between nodes are not missed. We develop a power management framework that allows a node to save energy while missing few communication opportunities. The framework is tailored to the available knowledge about network connectivity over time. Further, the framework supports an explicit tradeoff between energy savings and connectivity, so that network operators can choose, for example, to conserve energy at the cost of reduced message delivery performance. We evaluate our mechanisms using ns-2 simulations. Our results show that our power management mechanisms consume from 10% to 50% of the energy expended when the network operates without power management. These energy savings come at the cost of some performance degradation when available knowledge is incomplete, though our tuning parameter allows a rich set of tradeoffs between energy consumption and performance.

Economy driven content dissemination in Delay Tolerant Networks