383 research outputs found
Routing algorithms classification & Proposed Routing Algorithm for DTN
This paper provides an introduction to Delay Tolerant Networks (DTN)alogorithms and would touch upon some basic classification. Continuous connectivity is difficult in today�s wireless world. The data preservation and security in challenged and intermittent network, is of paramount importance. In this paper, we will see how DTN provides detail classification and discription for further studies & application.an effective alternative. Security of data becomes important in disrupted networks; this paper would also discuss Praposed Routing algorithms with DTNs
Reputation and credit based incentive mechanism for data-centric message delivery in delay tolerant networks
In a Data-centric Delay Tolerant Networks (DTNs), it is essential for nodes to cooperate in message forwarding in order to enable successful delivery of a message in an opportunistic fashion with nodes having their social interests defined. In the data-centric dissemination protocol proposed here, a source annotates messages (images) with keywords, and then intermediate nodes are presented with an option of adding keyword-based annotations in order to create higher content strength messages on path toward the destination. Hence, contents like images get enriched as there is situation evolution or learned by these intermediate nodes, such as in a battlefield, or in a disaster situation. Nodes might turn selfish and not participate in relaying messages due to relative scarcity of battery and storage capacity in mobile devices. Therefore, in addition to content enrichment, an incentive mechanism is proposed in this thesis which considers factors like message quality, battery usage, level of interests, etc. for the calculation of incentives. Moreover, with the goal of preventing the nodes from turning malicious by adding inappropriate message tags in the quest of acquiring more incentive, a distributed reputation model (DRM) is developed and consolidated with the proposed incentive scheme. DRM takes into account inputs from multiple users like ratings for the relevance of annotations in the message, message quality, etc. The proposed scheme safeguards the network from congestion due to uncooperative or selfish nodes in the system. The performance evaluation shows that our approach delivers more high priority and high quality messages while reducing traffic at a slightly lower message delivery ratio compared to ChitChat --Abstract, page iv
An Analytical Model of Epidemic Routing with Immunity for Disruption Tolerant Networks
We study the epidemic routing scheme with an immunity mechanism. The immunity mechanism enables more efficient utilization of limited buffer space at the nodes, by allowing nodes to remove outstanding copies of messages that have already been delivered. We develop a new analytical model for estimating the message delivery ratio (MDR) and the average delivery delay (ADD) under a variant of epidemic routing with the immunity mechanism, which we call an immunity routing scheme (IRS). The proposed model is based on a continuous-time Markov chain and takes into finite buffer sizes at the nodes.Laboratory for Telecommunications Science
Threshold Based Best Custodian Routing Protocol for Delay Tolerant Network
Delay Tolerant Network (DTN) is a kind of network in which the source may not be able to establish the stable and uninterrupted path to destination due to network partitioning, dynamic topology change and frequent disconnections. In order to dealt disruption and disconnections a store, carry and forward paradigm is used in which node stores the incoming messages in its buffer, carries it while moving and forward when comes within the transmission range of other nodes. Message forwarding contributes and important role in increasing its delivery. For instance, probabilistic routing protocol forwards message to a node having high probability value to meet message destination. These protocols cannot handle a situation in which the node continually transmits messages even the probability difference is very small. In this paper, we have proposed a routing protocol known as Threshold Based best custodian Routing Protocol (TBbcRP) for delay tolerant network. We have proposed a threshold-based method to compute the quality value which is the ability of node to carry message. A self-learning mechanism has been used to remove the delivered messages from the network. Moreover, a buffer aware mechanism has been used that make sure availability of buffer space at receiver before message transmission. We have compared the performance of TBbcRP with Epidemic, PRoPHET and Delegated Forwarding. The proposed TBbcRP outperforms in terms of maximizing the delivery probability, reducing number of transmissions and message drop
PERFORMANCE EVALUATION OF DISRUPTION TOLERANT NETWORKS WITH IMMUNITY MECHANISM AND CODING TECHNIQUE
We examine the performance of a Disruption Tolerant Networks (DTNs) with an epidemic routing (ER) scheme with the coding technique and/or immunity mechanism under the various network environments. We are interested in the scenarios of opportunistic dissemination of large files. First, we study how the different implementations of the ER scheme perform in diverse network settings. We compare the performance of ER with its summary vector implemented as both a list and as a Bloom filter. Second, we examine how network coding affects the performance of the ER scheme. To this end, we investigate the performance of encoding-based routing (EBR), a variant of the ER scheme which uses random linear coding at source nodes. EBR is expected to mitigate what is commonly known as the coupon collector’s problem, which arises when a large file is chopped into small fragments and then the fragments are disseminated throughout the network. We
compare this to the case where intermediate non-source nodes are allowed to create new linear combinations from the ones it already holds. Lastly, we evaluate the benefits of two different types of immunity mechanisms – one based on file ID and the other based on bundle ID – with not only the ER scheme but also two different EBR schemes in various network scenarios and settings. We also investigate the performance gain from compressing the immunity list.
By presenting and analyzing extensive simulation results, we provide information that could provide a guideline for employing each of the aforementioned techniques in routing schemes of interest in various network settings
THE PLAGUE AND THE PARTHENON: CRUSADE, CLIMATE CHANGE AND DISEASE IN THE EARLY MODERN MEDITERRANEAN
The present study examines the role epidemic diseases, specifically malaria and bubonic plague, played on the course of the Morean War (1684-1699). The Morean War was a major offensive by Christian powers, led by the Venetian Republic, against Ottoman controlled Greece. Christian victories during the war were widely celebrated across western Europe, but even in victory Christian forces took severe casualties from multiple disease outbreaks. First, this study seeks to explain the terrestrial and maritime networks the war was fought over, and how those networks either led the opposing forces into regions of endemic disease (malaria), or how they allowed other diseases (bubonic plague), to be distributed around the region. Furthermore, this demonstrates the impact of epidemic events on the Christian armies and the subsequent prosecution of the war, and that epidemic disease was a major catalyst behind demographic change in the Peloponnese, the principal theater of conflict
Epidemic models for research ideas spreading in the scientific community
We apply the basic SIR model and some of its extended versions to the propagation of scientific ideas in the community of researchers, in order to investigate the spread of those ideas. To this end, we collected quantitative records of articles published in scientific conferences for some selected topics over a 5 year period. The values of the basic reproductive ratio are discussed to compile classification based on the contagion level and the description given by the models are investigated
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