Routing In Disruption Tolerant Networks Research Articles

Adaptive DTN Routing: A Neuromorphic Networking Perspective

Routing is one of the main drivers of the end-to-end performance of bundle transmissions over a disruption tolerant network given the potentially large impact of the temporary but long-term partitioning that can occur at different sections of the network. A neuromorphic networking approach that defines an adaptive bundle routing for disruption-tolerant networks (DTN) is proposed where spiking neuronal networks (SNN) are used to determine the routing decisions of autonomous agents. The event-driven information encoding of spiking neurons involves very low energy consumption, which makes this approach attractive for challenging DTN applications with limited access to energy sources. The SNNs are continually updated within an autonomic loop, which produces synapse strength updates that are proportional to the expected communication costs of the routing decisions. A reward shaping procedure and a delay-tolerant mechanism for finding the local link-state is proposed, which allows determining instantaneous learning rewards for the agents. The method was tested on an emulated space communications network with scheduled disruptions. The results show that the proposed cognitive routing approach offers improved bundle delivery performance under network congestion compared to the standard Contact Graph Routing.

An Efficient method for Secure Routing in Delay Tolerant Networks

Delay or Disruption tolerant networks (DTNs) are mobile networks with inherent limitations on network connectivity and topology. There are a number of applications where such networks can be deployed. In extreme situations of lack of connectivity, DTNs nodes stores the messages to the destination and carry it, till it finds and suitable relay node to forward. Most of the existing researchers focused on developing smart relay selection strategies for DTNs. However, the security aspects, such as confidentiality and integrity of the messages being transmitted have been grossly overlooked in the existing DTN routing literature. Hence in this paper, we have addressed the security issues in DTN message forwarding and developed a secure method for message forwarding in DTN. Experimental results show that by incorporating the security features, DTN performance metrics, such as delivery ratio, overhead ratio and delivery delay have been improved compared to traditional routing strategies.

Contact graph routing in DTN space networks: overview, enhancements and performance

Delay- and Disruption Tolerant Networks (DTNs) are based on an overlay protocol and on the store-carry-forward paradigm. In practice, each DTN node can store information for a long time before forwarding it. DTNs are particularly suited to cope with the challenges imposed by the space environment. This paper is focused on routing in space DTNs, and in particular on contact graph routing (CGR) and its most representative enhancements, available in the literature, which are briefly surveyed in this work. Moreover, the applicability and the obtained performance of the DTN protocol stack and of the CGR have been evaluated by presenting results from real experimental experiences such as the Deep Impact Network experiment (employing the EPOXI space cruise), the JAXA jointly performed space link demonstrations with NASA (where the JAXA’s GEO relay satellite called Data Relay Test Satellite has been used), the Space Data Routers European Project, and the pilot operation of a DTN implementation on the International Space Station (ISS).

A one-hop information based geographic routing protocol for delay tolerant MANETs

Delay and disruption tolerant networks (DTNs) may lack continuous network connectivity. Routing in DTNs is thus a challenge since it must handle network partitioning, long delays, and dynamic topology. Meanwhile, routing protocols of the traditional mobile ad hoc networks (MANETs) cannot work well due to the failure of its assumption that most network connections are available. In this paper, a geographic routing protocol is proposed for MANETs in delay tolerant situations, by using no more than one-hop information. A utility function is designed for implementing the under-controlled replication strategy. To reduce the overheads caused by message flooding, we employ a criterion so as to evaluate the degree of message redundancy. Consequently a message redundancy coping mechanism is added to our routing protocol. Extensive simulations have been conducted and the results show that when node moving speed is relatively low, our routing protocol outperforms the other schemes such as Epidemic, Spray and Wait, FirstContact in delivery ratio and average hop count, while introducing an acceptable overhead ratio into the network.

SMART: A Social- and Mobile-Aware Routing Strategy for Disruption-Tolerant Networks

Disruption-tolerant networks (DTNs) are sparse mobile ad hoc networks where nodes connect with each other intermittently and end-to-end communication paths do not exist. Data routing in DTNs is challenging and has drawn much attention from research communities recently. Although many DTN routing strategies have been proposed in the past, they confront problems such as blind spots and dead ends and lack efficient implementation in a decentralized, large-scale, mobile, and dynamic environment. To overcome these difficulties, we introduce a new solution for DTNs that leverages the social properties and mobility characteristics of users. Our observation of the mobile trajectories of three data sets collected from real DTNs reveals that user movements appear locally and they tend to form communities correlated to geographic locations. Based on these findings, we propose a social- and mobile-aware routing strategy (SMART). It exploits a distributed community partitioning algorithm to divide the DTN into smaller communities regarding user locations and interaction routines. For intracommunity communications, a decayed routing metric convoluting social similarity and social centrality is calculated, which is used to decide forwarding node efficiently while avoiding the blind-spot and dead-end problems. To enable efficient intercommunity communications, we choose the fringe nodes that travel remotely as relays, and we propose the node-to-community utilities for routing decision across communities. We present empirical analysis to show that SMART reduces the occurrence of blind spots and dead ends to a level below 1%. The efficiency of SMART is evaluated by extensive trace-driven experiments, which illustrate that it outperforms other routing strategies in various real DTN traces.

Replication Control for Ensuring Reliability of Convergecast Message Delivery in Infrastructure-Aided DTNs

Hybrid networks constructed from cellular networks and delay- and disruption-tolerant networks (DTNs) are able to provide reliable communications to mobile nodes in base-station-starved areas regardless of node mobility or density. However, no routing scheme in DTNs has considered the adaptation to other networks, i.e., cellular networks. Thus, the reliability of message delivery is dependent on the position relationship between source nodes and base stations. In this paper, we propose an advanced routing scheme that controls the maximum number of replicas according to the distance between the source node and the nearest base station. Furthermore, we show how to decide the maximum number of replica messages for the distance from the base stations by analyzing the message delivery reliability of an existing DTN routing scheme. Additionally, we execute extensive computer simulations to evaluate the performance of our proposed routing scheme. Our results show that our proposed routing scheme keeps the required reliability regardless of the source node location.

Directed Flooding Routing Algorithm Based on Location in DTN

. In allusion to the high delay, restricted nodes resources and lack of persistent end to end connections in Delay /Disruption Tolerant Networks ( DTN) ,this paper proposes a novel directed flooding routing algorithm based on location information. The algorithm combines DTN with the known nodes locations in communication channel to improve the DTN networks topology knowledge to reduce the noneffective duplicate,then conducts single duplicate routing depending on location. The algorithm can increase the directivity and purposiveness of message transmission, decrease the consumption of networks resources, and thereby reduce propagation delay and improve the delivery ratio. The simulation shows that the proposed algorithm is feasible and effective, and it is superior to the typical DTN routing algorithms such as Epidemic Routing.

Efficient DTN Routing Protocol

his paper presents a novel routing protocol for Disruption Tolerant Networks (DTNs) called Efficient DTN Routing Protocol (EDRP). EDRP smartly integrates the forwarding and buffer management policies into an adaptive protocol that includes a local network parameters estimation mechanism. It dynamically adjusts the delivery probability for messages according to a new metric. Meanwhile, EDRP arranges the forwarding sequence and the dropping priority based on their assigned weight. The weight is determined by the Replication Density (RD), the Message Length (ML), and Message Remaining Life Time (MRLT). An extensive simulation of EDRP was carried out and its performance was compared to well known DTN routing protocols: PRoPHET, and Epidemic Routing protocols. Simulation results show that the proposed routing protocol outperforms them in terms of packet delivery ratio , delivery delay and message overhead. General Terms DTN networks, Opportunistic network, Adaptive routing protocols, Forwarding and Dropping, New routing protocols.

Managing Disconnected Mobile Nodes in a Delay Tolerant Network with HALF Routing Protocol

Delay and Disruption Tolerant Networks (DTN) can provide an underlying base to support mobility environments. DTN is equipped with advance features such as custody transfer and hop by hop routing which can tackle the frequent disconnections of mobile devices by buffering bundles and dynamically making hop-by-hop routing decisions under intermittent connectivity environment. In this paper, we have proposed a DTN routing protocol HALF (Handoffbased And Limited Flooding) which can manage and improve performance of disrupted and challenging communication between mobile nodes in the presence of an infrastructure network consisting of fixed interconnected nodes (routers). HALF makes use of the general handoff mechanisms intended for the IP network, in a DTN way and also integrates a limited flooding technique to it. Simulation results show that HALF attains better performance than other existing DTN routing protocols under diverse network conditions. As the traffic intensity changes from low to high, delivery ratio of other DTN routing protocols decreased by 50% to 75% whereas in HALF such ratio is reduced by less than 5%. HALF can deliver about 3 times more messages than the other protocols when the disrupted network has to deal with larger size of messages. If we calculate the overhead ratio in terms of „how many extra (successful) transfer‟ is needed for each delivery, HALF gives less than 20% overhead ratio while providing a good delivery ratio.

Cooperation as a Service in VANET: Implementation and Simulation Results

The past decade has witnessed the emergence of Vehicular Ad-hoc Networks (VANET), specializing from the well-known Mobile Ad Hoc Networks (MANET) to Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) wireless communications. While the original motivation for Vehicular Networks was to promote traffic safety, recently it has become increasingly obvious that Vehicular Networks open new vistas for Internet access, providing weather or road condition, parking availability, distributed gaming, and advertisement. In previous papers [27,28], we introduced Cooperation as a Service (CaaS); a new service-oriented solution which enables improved and new services for the road users and an optimized use of the road network through vehicle's cooperation and vehicle-to-vehicle communications. The current paper is an extension of the first ones; it describes an improved version of CaaS and provides its full implementation details and simulation results. CaaS structures the network into clusters, and uses Content Based Routing (CBR) for intra-cluster communications and DTN (Delay–and disruption-Tolerant Network) routing for inter-cluster communications. To show the feasibility of our approach, we implemented and tested CaaS using Opnet modeler software package. Simulation results prove the correctness of our protocol and indicate that CaaS achieves higher performance as compared to an Epidemic approach.

An Efficient Prediction-Based Routing in Disruption-Tolerant Networks

Routing is one of the most challenging, open problems in disruption-tolerant networks (DTNs) because of the short-lived wireless connectivity environment. To deal with this issue, researchers have investigated routing based on the prediction of future contacts, taking advantage of nodes' mobility history. However, most of the previous work focused on the prediction of whether two nodes would have a contact, without considering the time of the contact. This paper proposes predict and relay (PER), an efficient routing algorithm for DTNs, where nodes determine the probability distribution of future contact times and choose a proper next-hop in order to improve the end-to-end delivery probability. The algorithm is based on two observations: one is that nodes usually move around a set of well-visited landmark points instead of moving randomly; the other is that node mobility behavior is semi-deterministic and could be predicted once there is sufficient mobility history information. Specifically, our approach employs a time-homogeneous semi-Markov process model that describes node mobility as transitions between landmarks. Then, we extend it to handle the scenario where we consider the transition time between two landmarks. A simulation study shows that this approach improves the delivery ratio and also reduces the delivery latency compared to traditional DTN routing schemes.

Impact of source counter on routing performance in resource constrained DTNs

We study routing schemes for Disruption Tolerant Networks (DTNs) where transmission bandwidth is scarce. In such a setting, a key issue is how to schedule the transmission of packets under limited bandwidth to optimize performance. Such a scheduling consists of source control (i.e., source nodes choosing a routing scheme) and the local transmission scheduling performed by each node. Existing works typically focus on transmission scheduling and buffer management aspects, but due to theoretical and practical difficulties, only heuristics have been proposed. In this work, we explore an alternative way to improve DTN routing performance via source control. We first show through simulation that for spray-and-wait routing scheme where the source node specifies the maximum allowed number of copies of a packet in the network, there exists an optimal counter value that achieves the minimum network-wide average packet delivery delay. Then as a first step towards understanding multi-hop multi-copy DTN routing schemes such as spray-and-wait scheme, we perform modeling study of two-hop single-copy scheme and two-hop multi-copy scheme under various transmission scheduling schemes, via queuing network analysis and continuous time Markov chain model analysis. Our modeling analysis provides insights into the impact of source counter on routing performance and further suggests the existence of an optimal counter value. Relying on the insights gained via simulations and modeling studies, we propose an adaptive scheme where nodes adjust their counter values to achieve minimum packet delivery delay, in a distributed and asynchronous fashion. Simulations demonstrate the effectiveness of our scheme and suggest the potential of exploring this rich area for improving DTN routing performance.

EnPassant: anonymous routing for disruption‐tolerant networks with applications in assistive environments

ABSTRACTDisruption‐tolerant networking holds a great deal of potential for making communications easier and more flexible in pervasive assistive environments. However, security and privacy must be addressed to make these communications acceptable with respect to protecting patient privacy. We propose EnPassant, a system for using disruption‐tolerant networking in privacy‐preserving way. EnPassant uses concepts from anonymous communications, re‐routing messages through groups of peer nodes to hide the relation between the sources and destinations. We describe a set of protocols that explore a practical range of tradeoffs between privacy and communication costs by modifying how closely the protocol adheres to the optimal predicted path. We also describe the cryptographic tools needed to facilitate changes in‐group membership. Finally, we present the results of extensive trace‐based simulation experiments that allow us to both compare between our proposed protocols and observe the costs of increasing the number of groups and intermediate nodes in a path. Copyright © 2010 John Wiley & Sons, Ltd.

Routing for disruption tolerant networks: taxonomy and design

Communication networks, whether they are wired or wireless, have traditionally been assumed to be connected at least most of the time. However, emerging applications such as emergency response, special operations, smart environments, VANETs, etc. coupled with node heterogeneity and volatile links (e.g. due to wireless propagation phenomena and node mobility) will likely change the typical conditions under which networks operate. In fact, in such scenarios, networks may be mostly disconnected, i.e., most of the time, end-to-end paths connecting every node pair do not exist. To cope with frequent, long-lived disconnections, opportunistic routing techniques have been proposed in which, at every hop, a node decides whether it should forward or store-and-carry a message. Despite a growing number of such proposals, there still exists little consensus on the most suitable routing algorithm(s) in this context. One of the reasons is the large diversity of emerging wireless applications and networks exhibiting such episodic connectivity. These networks often have very different characteristics and requirements, making it very difficult, if not impossible, to design a routing solution that fits all. In this paper, we first break up existing routing strategies into a small number of common and tunable routing modules (e.g. message replication, coding, etc.), and then show how and when a given routing module should be used, depending on the set of network characteristics exhibited by the wireless application. We further attempt to create a taxonomy for intermittently connected networks. We try to identify generic network characteristics that are relevant to the routing process (e.g., network density, node heterogeneity, mobility patterns) and dissect different wireless networks or applications based on these characteristics. Our goal is to identify a set of useful design guidelines that will enable one to choose an appropriate routing protocol for the application or network in hand. Finally, to demonstrate the utility of our approach, we take up some case studies of challenged wireless networks, and validate some of our routing design principles using simulations.

Replication Routing in DTNs: A Resource Allocation Approach

Routing protocols for disruption-tolerant networks (DTNs) use a variety of mechanisms, including discovering the meeting probabilities among nodes, packet replication, and network coding. The primary focus of these mechanisms is to increase the likelihood of finding a path with limited information, and so these approaches have only an incidental effect on such routing metrics as maximum or average delivery delay. In this paper, we present rapid, an intentional DTN routing protocol that can optimize a specific routing metric such as the worst-case delivery delay or the fraction of packets that are delivered within a deadline. The key insight is to treat DTN routing as a resource allocation problem that translates the routing metric into per-packet utilities that determine how packets should be replicated in the system. We evaluate rapid rigorously through a prototype deployed over a vehicular DTN testbed of 40 buses and simulations based on real traces. To our knowledge, this is the first paper to report on a routing protocol deployed on a real outdoor DTN. Our results suggest that rapid significantly outperforms existing routing protocols for several metrics. We also show empirically that for small loads, RAPID is within 10% of the optimal performance.

Performance evaluations of data-centric information retrieval schemes for DTNs

Mobile nodes in some challenging network scenarios, e.g. battlefield and disaster recovery scenarios, suffer from intermittent connectivity and frequent partitions. Disruption Tolerant Network (DTN) technologies are designed to enable communications in such environments. Several DTN routing schemes have been proposed. However, not much work has been done on designing schemes that provide efficient information access in such challenging network scenarios. In this paper, we explore how a content-based information retrieval system can be designed for DTNs. There are three important design issues, namely (a) how data should be replicated and stored at multiple nodes, (b) how a query is disseminated in sparsely connected networks, and (c) how a query response is routed back to the issuing node. We first describe how to select nodes for storing the replicated copies of data items. We consider the random and the intelligent caching schemes. In the random caching scheme, nodes that are encountered first by a data-generating node are selected to cache the extra copies while in the intelligent caching scheme, nodes that can potentially meet more nodes, e.g. faster nodes, are selected to cache the extra data copies. The number of replicated data copies K can be the same for all data items or varied depending on the access frequencies of the data items. In this work, we consider fixed, proportional and square-root replication schemes. Then, we describe two query dissemination schemes: (a) W-copy Selective Query Spraying (WSS) scheme and (b) L-hop Neighborhood Spraying (LNS) scheme. In the WSS scheme, nodes that can move faster are selected to cache the queries while in the LNS scheme, nodes that are within L-hops of a querying node will cache the queries. For message routing, we use an enhanced Prophet scheme where a next-hop node is selected only if its predicted delivery probability to the destination is higher than a certain threshold. We conduct extensive simulation studies to evaluate different combinations of the replication and query dissemination algorithms. Our results reveal that the scheme that performs the best is the one that uses the WSS scheme combined with binary spread of replicated data copies. The WSS scheme can achieve a higher query success ratio when compared to a scheme that does not use any data and query replication. Furthermore, the square-root and proportional replication schemes provide higher query success ratio than the fixed copy approach with varying node density. In addition, the intelligent caching approach can further improve the query success ratio by 5.3-15.8% with varying node density. Our results using different mobility models reveal that the query success ratio degrades at most 7.3% when the Community-Based model is used compared to the Random Waypoint (RWP) model [J. Broch et al., A Performance Comparison of Multihop wireless Ad hoc Network Routing Protocols, ACM Mobicom, 1998, pp. 85-97]. Compared to the RWP and the Community-Based mobility models, the UmassBusNet model from the DieselNet project [X. Zhang et al., Modeling of a Bus-based Disruption Tolerant Network Trace, Proceedings of ACM Mobihoc, 2007.] achieves much lower query success ratio because of the longer inter-node encounter time.

Packet Scheduling and Discard Policies for Diffusion Control in Delay and Disruption Tolerant Networks

A Disruption Tolerant Network (DTN) is characterized by scenarios where end-to-end connectivity is rarely available. Hence, in such networks, the use of existing ad hoc routing protocols may result on poor performance, since they rely on the existence of an end-to-end path between the source and destination nodes. This paper proposes a DTN routing strategy called DRAIN. Differently from other proposals based on Epidemic routing, DRAIN considers realistic scenarios where nodes’ buffer capacity and link bandwidth are limited. Our performance analysis demonstrates the inefficacy of the Epidemic approach in scenarios under such constraints. However, through a controlled packet diffusion and a quantitative packet deliver estimate, DRAIN is able to present good delivery rates in the same conditions, as well as a lower consumption of network resources.

Performance Evaluation of a Power Management Scheme for Disruption Tolerant Network

Disruption tolerant network (DTN) is characterized by frequent partitions and intermittent connectivity. Power management issue in such networks is challenging. Existing power management schemes for wireless networks cannot be directly applied to DTNs because they assume the networks are well-connected. Since the network connectivity opportunities are rare, any power management scheme deployed in DTNs should not worsen the existing network connectivity. In this paper, we design a power management scheme called context-aware power management scheme (CAPM) for DTNs. Our CAPM scheme has an adaptive on period feature that allows it to achieve high delivery ratio and low delivery latency when used with Prophet, a recently proposed DTN routing scheme. Via simulations, we evaluate the performance of the CAPM scheme when used with the Prophet routing scheme in different scenarios e.g. different traffic load, node speeds and sleep patterns. Our evaluation results indicate that the CAPM scheme is very promising in providing energy saving (as high as 80%) without degrading much the data delivery performance.