Delay Tolerant Networks

Today’s Internet has been very successful at connecting communicating devices round the globe. It has been made possible by using a set of protocols, which is widely known as TCP/IP protocol suite. Every device on the innumerous sub-networks that comprise the Internet uses this protocol for transferring the data from source to destination with the minimal possible delay and high reliability. The underlying principle on which TCP/IP works is based on end-to-end data transfer using number of potentially dissimilar link-layer technologies. However, there are many regions where the assumptions of the internet cannot be upheld. If at any instant there is no path between the sources to destination, then TCP/IP fails to work properly or might even stop working completely. Because of such circumstances, a newer network has evolved which is independent end to end connectivity between nodes. This network is called as Delay Tolerant Networks (DTN).

b. Store and Forward Technique Delay Tolerant Networks have overcome the problems associated with the conventional protocols in terms of lack of connectivity, irregular delays, asymmetric bidirectional data rates etc. using the concept of store and forward. The method of store and forward is very analogous to the real life postal service. Every letter has to pass through a set of post offices, here it is processed and forwarded, before reaching the destination. Here the complete message or a chunk of it is transferred and stored in nodes successively until it reaches the destination. The following figure (fig. 3), gives a rough graphical representation of how a message is propagated through a network.

Fig. 10. Message delivery ratio comparison among ER, PRoPHET, Spray And Wait, Spray And Focus, NNV in RWP regarding buffer changes V. C ONCLUSION Delay tolerant networks (DTNs) are sparse wireless networks with intermittent connections. Routing in such networks is challenging. In this paper, a new routing protocol, called nearest neighbor visit (NNV) is proposed. Due to limited sources of nodes, it tries to reduce overhead while maintaining good message delivery ratio. NNV tries to find connected neighbors which are geographically closest to destination and sends the message to it. The receiving node, forwards the message to nodes which have recently met the destination. This will greatly reduce delay and overhead. In order to evaluate proposed method, NNV was compared to ER, PROPHET, Spray And wait, and Spray And Focus. Experiments were done on UCL data base and random values. Simulation results proved that NNV has reduced overhead and delivery delay while keeping message delivery ratio in acceptable range.

packets according to their respective interest profiles. Each node periodically broadcasts its interest profile and a list of service descriptors of the packets it currently carries and when any of the receivers of this broadcast is either interested in the broadcasted interest profile or can provide the service matching the service description, the data are exchanged. After receiving a discovery reply, the service requestor sends an invocation request to the service provider and waits for the real service data. To the best of our knowledge, this is the only paper that targets service discovery in delay tolerant networks. Unfortunately, the paper does not discuss how the interest profiles are created. With all nodes having interest profiles covering all services, both query and service packets are using expensive epidemic spreading, while with all nodes having interest profiles equal to services they provide, the protocol enables service discovery when the requestor meets the service provider. The latter case is termed Proximity-based method, which has low overhead but also low service discovery rate. Even in this case, the overhead (periodic broadcasts of service request) is dependent on frequency of the broadcast and on the length of the cutoff time for the service discover, none of which was defined in [10].

Delay tolerant networks (DTNs) have attracted much attention from research workers due to their wide applications in various challenging environments. Existing Delay tolerant networks research mainly concentrates on information propagation and packet delivery. Delay tolerant networks where the time evolving topology is known a priori or can be judged. We framed such a time-evolving network as a weighted directed space time graph which includes both special and temporal information. Links that are inside the space time graph are unreliable due to either the dynamic nature of wireless communications. The purpose of our topology design problem is to build a sparse structure from the original space-time graph such that for any pair of devices, there is a space-time path connecting them with reliability higher than the required threshold the total cost of the structure is reduced. Such an optimization problem is NP-hard, thus we propose several heuristics which can significantly downs the total cost of the topology while maintain the

Email: anniegrace03@yahoo.com.cn Abstract—Delay tolerant networks (DTNs) attempt to minimize the possible adverse impacts due to limitations and anomalies in intermittently connected networks. Routing in such sparse and dynamic networks is difficult as the source has little information about the destination, rendering a key challenge to find one simple and effective message delivery mechanism. In this paper, we propose PriCost, a protocol based on the cost for efficient routing of messages, and use the node’s past interactions with others to determine the cost of potential routing, in the absence of any other information. Our simulations show that PriCost performs better than MaxProp with reduced complexity. The evaluations also show different cost based metrics hardly affect the performance provided they depend on the same feature extraction algorithm.

† School of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, U.K. Email: jindp@mail.tsinghua.edu.cn Abstract—In Delay Tolerant Networks (DTNs), there exists only intermittent connectivity between communication sources and destinations. In order to provide successful communication services for these challenged networks, a variety of relaying and routing algorithms have been proposed with the assumption that nodes are homogeneous in terms of contact rates and delivery costs. However, various applications of DTN have shown that mobile nodes should be divided into different classes in terms of their energy requirements and communication ability, and real application data have revealed the heterogeneous contact rates between node pairs. In this paper, we design an optimal relaying scheme for DTNs, which takes into account nodes’ heterogeneous contact rates and delivery costs when selecting relays to minimise the delivery cost while satisfying the required message delivery probability. Extensive results based on real traces demonstrate that our relaying scheme requires the least delivery cost and achieves the largest maximum delivery probability, compared with the schemes that neglect nodes’ heterogeneity.

ABSTRACT Delay-tolerant networks (DTNs) have the potential to connect de- vices and areas of the world that are under-served by current net- works. A critical challenge for DTNs is determining routes through the network without ever having an end-to-end connection, or even knowing which “routers” will be connected at any given time. Prior approaches have focused either on epidemic message replication or on knowledge of the connectivity schedule. The epidemic ap- proach of replicating messages to all nodes is expensive and does not appear to scale well with increasing load. It can, however, op- erate without any prior network configuration. The alternatives, by requiring a priori connectivity knowledge, appear infeasible for a self-configuring network.

Advances in ubiquitous mobile computing has given rise to the pervasive deploy- ment of physical devices embedded with sensors, software, and wireless commu- nications that collect and exchange data. These devices are adept for deployment in environments with minimal existing infrastructure, as the devices themselves become the components of a functioning network. With the addition of mobil- ity, these devices operate where disruption between entities is high, resulting in dynamic, fragmented, and ephemeral networks. Such networks are considered Delay Tolerant Networks (DTNs). The pervasiveness of DTN nodes, and their varied deployment environments leads to two important motivations for securing DTNs. First, the data collected, stored, and transferred between nodes can be of high value due to commercial, safety, or national security reasons. Second, persistent threats from adversaries are common. Consequently, the development of techniques to secure communications from persistent threats from within a DTN is an important area of research.

Abstract In delay tolerant networks (DTNs), the network may not be fully connected at any instant of time, but connections occurring between nodes at different times make the network connected through the entire time continuum. In such a case, traditional routing methods fail to operate because there are no contemporaneous end-to-end paths between sources and destinations. This study examines the routing in DTNs where connections arise in a periodic nature. We analyze various levels of periodicity in order to meet the requirements of different network models. We propose different routing algorithms for different kinds of periodic connections. Our proposed routing methods guarantee the earliest delivery time and minimum hop-count, simultaneously. We evaluate our routing schemes via extensive simulation experiments and compare them to some other popular routing approaches proposed for DTNs. Our evaluations show the feasibility and effectiveness of our schemes as viable routing methods for delay tolerant networks.

Email: nilamchaudhary115@gmail.com 1 , svpatel.ce@spcevng.ac.in 2 Abstract- Delay tolerant network refers to a network where connectivity is opportunistic. Due to such intermittent connectivity traditional routing protocol fails. In order to efficiently route the information in such an environment there have been proposed various classes of routing: Replication based, Knowledge based and Coding based etc. This technique uses local information available with node: Neighbourhood index, past contacts, contact duration, node mobility etc. to determine next hop or destination. This paper presents survey on a routing strategy of Flooding (Replication) based, Knowledge (Store and Forwarding) based and based on Coding in delay tolerant networks.

Delay Tolerant Networks (DTN) have the unique feature of intermittent connectivity[15], which provides opportunistic communication [1] and makes routing different from other wireless networks. In standard network, nodes are connected most of the time. But in case of DTN, the connectivity is not constantly maintained but it is still desirable to allow communication between nodes. Hence traditional routing protocols are unable to deliver packets between the hosts. They require end-to-end connectivity between nodes. The node mobility is other cause for lack of end-to-end connectivity. It introduces the problem of lack of knowledge about current position of node, if mobility pattern is unknown.

Index Terms: Delay-tolerant networks, Proximity malware, and Behavioral malware characterization. 1. INTRODUCTION Mobile shopper natural philosophy permeate our lives. laptop computer computers, PDAs, and additional recently and conspicuously, smart-phones, are getting indispensable tools for our educational, skilled, and entertainment needs. These new devices are often equipped with a diverse set of non- infrastructural connectivity technologies, e.g., Infra-red, Bluetooth, and more recently, Wi-Fi Direct. With the universal presence of these short-range connectivity technologies, the communication paradigm, identified by the networking research community under the umbrella term Delay-tolerant Networks (DTNs), is becoming a viable alternative to the traditional infrastructural paradigm.

II. D ELAY T OLERANT N ETWORKS The most important routing objective in DTNs is to maximize the probability of message deliver. One of the major properties of delay tolerant networks (DTNs) is that there does not always exist a complete path from a source to a destination. DTN routing protocols appropriate the mobility of the nodes and buffering of messages. This also makes possible for a node to carry a message and in that Way Bridge partitions in the network. It knows as store-carry-forward. When a message is created and stored in the source node, if a contact becomes available to a next-hop node the message is sent over this contact. Messages are stored at the new node until the destination node is found.

V. C ONCLUSION AND F UTURE W ORK Delay-tolerant networking (DTN) is an approach to computer network that solves the technical issues in heterogeneous network that face the unpredictable loss of continuous network connectivity, long delay, high error rates. The new application called Secured Delay Tolerant Networks (SDTN) has been designed for securing Delay Tolerant Networks. It provides security for the data sent among the nodes in the DTN. Pattern matching of viruses is an effective method in detecting viruses. Both the pattern matching method for detecting viruses and using Bundle Security Protocol gives more strengthen DTN. This scheme is designed in such a way that it causes lesser communication overhead.Application Secured Delay Tolerant Networks, is not able to detect the viruses which are obfuscated. As a part of my future work, I would like to incorporate the method to find the obfuscated viruses as well as to design more strengthen

KEYWORDS: Delay Tolerant Mobile Network (DTMN), Exponential Weighted Moving Average (EWMA). I INTRODUCTION Delay tolerant networks(DTNs) is an excited research topic nowadays has been introduced to mobile communications technology[1],[2] that does not guarantee the existence of path between a source and destination. When the two nodes move with each other's transmission region between a periods of time they can meet each other. When it move out of transmission region the connection is lost between the hosts. The message to be delivered by carrying from source to destination can be appearing or forecast. The networks must tolerate the delay of the message in such networks routing is hugely based on root contact probabilities.

In this paper we consider how to provide anonymity in Delay Tolerant Networks (DTN). DTNs [6] provide end-to-end communication in environments lacking continuous connectivity or presenting long delays. We focus our work in a class of DTNs called deterministic DTNs, which are such networks where the behavior is known in advance or where a repetitive action occurs over time. We will show that in such scenarios anonymous communications can be established using an onion routing [8] approach which takes into account the particularities of deterministic DTNs.

As discussed before, the DTN overlays on top of heterogeneous regional networks. These underlying networks might suffer from scarce resources such as limited band- width, limited connectivity, constrained storage in the intermediaries, etc. Security is a critical issue in the DTN architecture, where the communicating nodes running in the extreme environments, may be threatened by malevolent security attacks. The DTN Security Overview document [20] highlights some possible security threats that pose unique challenges to secure DTN communication. These include unauthorized resource consumption and denial-of-service (DoS) attacks. Without integrity and confidentiality, bundle data might be corrupted or read by malicious users while in transit. So security services are required in some circumstances in the delay-tolerant networks. The DTN architecture security requirements differ from traditional net- work security model in the sense that security services need to be incorporated in the intermediate DTN nodes in addition to the source and destination node [21].

M.S. in Computer Engineering Supervisor: Asst. Prof. Dr. ˙Ibrahim K¨ orpeo˘ glu August, 2010 In delay tolerant networks (DTNs), the network may not be fully connected at any instance of time, but connections occurring between nodes at different times make the network connected through the entire time continuum. In such a case, traditional routing methods fail to operate as there are no contemporaneous end-to-end paths between sources and destinations. This study examines the routing in DTNs where connections arise in a periodic nature. Various levels of periodicity are analyzed to meet requirements of different network models. We propose various routing algorithms for periodic connections. Our proposed methods can find routes that can guarantee earliest delivery and minimum hop count. We evaluate our routing schemes via extensive simulation experiments and also compare them to some other popular routing approaches proposed for delay tolerant networks. Our evaluations show the feasibility and effectivenes of our schemes as alternative routing methods for delay tolerant networks.

3.1 a l g o r i t h m s p e c i f i c at i o n Most of the approaches, presented in previous chapter, are based on a buffer drop differentia- tion. These approaches create a set of directives that allow to select which message, present in the buffer of a node, is going to be discarded. This means that, it does not create a direct chance of delivery to certain messages, it just avoids them to be discarded later than sooner. The purpose of this thesis is to integrate traffic differentiation in delay tolerant networks, but using a different approach. The goal is to achieve differentiation, in a form similar to the currently existing one on non delay tolerant network connections that is through pre-selection of which messages are the ones to have priority on sending. This pre-selection directly in- fluences the delivery. This chapter focus on the algorithms required to improve the delivery rate through traffic differentiation in DTN , by prioritising messages. The base algorithm will then serve as a guide for existing routing protocols, namely Epidemic, Spray and Wait, and