Article

Buffer Scheme Optimization of Epidemic Routing in Delay Tolerant Networks

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Abstract

In delay tolerant networks (DTNs), delay is inevitable; thus, making better use of buffer space to maximize the packet delivery rate is more important than delay reduction. In DTNs, epidemic routing is a well-known routing protocol. However, epidemic routing is very sensitive to buffer size. Once the buffer size in nodes is insufficient, the performance of epidemic routing will be drastically reduced. In this paper, we propose a buffer scheme to optimize the performance of epidemic routing on the basis of the Lagrangian and dual problem models. By using the proposed optimal buffer scheme, the packet delivery rate in epidemic routing is considerably improved. Our simulation results show that epidemic routing with the proposed optimal buffer scheme outperforms the original epidemic routing in terms of packet delivery rate and average end-to-end delay. It is worth noting that the improved epidemic routing needs much less buffer size compared to that of the original epidemic routing for ensuring the same packet delivery rate. In particular, even though the buffer size is very small (e.g., 50), the packet delivery rate in epidemic routing with the proposed optimal buffer scheme is still 95.8%, which can satisfy general communication demand.

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... The reader will skip to the next tag after the timer times out, and the object can still be recognized without the message of the blocked tag. In conclusion, the man-in-the-middle attack is prevented[15],[19],[20]. ...
... In conclusion, the man-in-the-middle attack is prevented [15], [19], [20]. ...
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We introduce the Delay Tolerant Firework Routing (DTFR) protocol, a protocol designed for routing in wireless Delay Tolerant Networks (DTNs) that consist of very large numbers of highly mobile nodes. Under DTFR, each packet initially travels, using high priority transmissions, to a target region in the network where the destination is expected to be. Once there, the packet is replicated to a number of copies that spread across the target region, in search of the destination. As soon as a copy finds a known route to the destination, it follows it and gets delivered. To evaluate DTFR's performance, we have developed a simulation tool that can handle networks with numbers of nodes on the order of 104. The simulation is optimized for use in DTNs and is very detailed, taking into account, among other things, the Media Access sublayer and the contents of buffers. Our protocol is compared against (i) Spray and Wait, (ii) GeoCross, (in) GeoDTN+Nav, (iv) a simple flooding protocol (chosen as one extreme of the design space), and (v) Bethlehem Routing (BR), an idealistic protocol that upper bounds the performance of a wide class of protocols. For a wide range of parameters, our protocol is superior (in terms of packet delay and aggregate throughput) to Spray and Wait, GeoCross, GeoDTN+Nav, and the flooding protocol, and performs close to the Bethlehem upper bound.
Article
In this paper, we develop a rigorous, unified framework based on ordinary differential equations (ODEs) to study epidemic routing and its variations. These ODEs can be derived as limits of Markovian models under a natural scaling as the number of nodes increases. While an analytical study of Markovian models is quite complex and numerical solution impractical for large networks, the corresponding ODE models yield closed-form expressions for several performance metrics of interest, and a numerical solution complexity that does not increase with the number of nodes. Using this ODE approach, we investigate how resources such as buffer space and the number of copies made for a packet can be traded for faster delivery, illustrating the differences among various forwarding and recovery schemes considered. We perform model validations through simulation studies. Finally we consider the effect of buffer management by complementing the forwarding models with Markovian and fluid buffer models.
Conference Paper
The non-existence of an end-to-end path poses a challenge in adapting the traditional routing algorithms to delay tolerant networks (DTNs). Previous works include centralized rout- ing approaches based on deterministic mobility, ferry-based routing with deterministic or semi-deterministic mobility, ∞ooding-based approaches for networks with general mo- bility, and probability-based routing for semi-deterministic mobility models. Unfortunately, none of these methods can guarantee both scalability and delivery. In this work,we in- vestigate scalable deterministic routing in DTNs. Instead of routing with global contact knowledge, we propose a simpli- fled DTN model and a routing algorithm which routes on contact information compressed by three combined meth- ods. Analytical studies and simulation results show that the performance of our proposed routing algorithm, DTN Hierarchical Routing (DHR), approximates that of the op- timal time-space Dijkstra's algorithm in terms of delay and hop-count. At the same time, the per node storage overhead is substantially reduced and becomes scalable. Although our work is based on a simplifled DTN model, we believe this approach will lay a groundwork for the understanding of scalable routing in DTNs.
Conference Paper
In this paper, we develop a rigorous, unified framework based on Ordinary Differential Equations (ODEs) to study epidemic routing and its variations. These ODEs can be derived as limits of Markovian models under a natural scaling as the number of nodes increases. While an analytical study of Markovian models is quite complex and numerical solution impractical for large networks, the corresponding ODE models yield closed-form expressions for several performance metrics of interest, and a numerical solution complexity that does not increase with the number of nodes. Using this ODE approach, we investigate how resources such as buffer space and power can be traded for faster delivery, illustrating the differences among the various epidemic schemes considered. Finally we consider the effect of buffer management by complementing the forwarding models with Markovian and fluid buffer models.
Conference Paper
We formulate the delay-tolerant networking routing problem, where messages are to be moved end-to-end across a connectivity graph that is time-varying but whose dynamics may be known in advance. The problem has the added constraints of finite buffers at each node and the general property that no contemporaneous end-to-end path may ever exist. This situation limits the applicability of traditional routing approaches that tend to treat outages as failures and seek to find an existing end-to-end path. We propose a framework for evaluating routing algorithms in such environments. We then develop several algorithms and use simulations to compare their performance with respect to the amount of knowledge they require about network topology. We find that, as expected, the algorithms using the least knowledge tend to perform poorly. We also find that with limited additional knowledge, far less than complete global knowledge, efficient algorithms can be constructed for routing in such environments. To the best of our knowledge this is the first such investigation of routing issues in DTNs.
Conference Paper
The highly successful architecture and protocols of today's Internet may operate poorly in environments characterized by very long delay paths and frequent network partitions. These problems are exacerbated by end nodes with limited power or memory resources. Often deployed in mobile and extreme environments lacking continuous connectivity, many such networks have their own specialized protocols, and do not utilize IP. To achieve interoperability between them, we propose a network architecture and application interface structured around optionally-reliable asynchronous message forwarding, with limited expectations of end-to-end connectivity and node resources. The architecture operates as an overlay above the transport layers of the networks it interconnects, and provides key services such as in-network data storage and retransmission, interoperable naming, authenticated forwarding and a coarse-grained class of service.
Article
In this paper, we present a framework for analyzing routing performance in delay tolerant networks (DTNs). Differently from previous work, our framework is aimed at characterizing the exact distribution of relevant performance metrics, which is a substantial improvement over existing studies characterizing either the expected value of the metric, or an asymptotic approximation of the actual distribution. In particular, the considered performance metrics are packet delivery delay, and communication cost, expressed as number of copies of a packet circulating in the network at the time of delivery. Our proposed framework is based on a characterization of the routing process as a stochastic coloring process and can be applied to model performance of most stateless delay tolerant routing protocols, such as epidemic, two-hops, and spray and wait. After introducing the framework, we present examples of its application to derive the packet delivery delay and communication cost distribution of two such protocols, namely epidemic and two- hops routing. Characterizing packet delivery delay and communication cost distribution is important to investigate fundamental properties of delay tolerant networks. As an example, we show how packet delivery delay distribution can be used to estimate how epidemic routing performance changes in presence of different degrees of node cooperation within the network. More specifically, we consider fully cooperative, noncooperative, and probabilistic cooperative scenarios, and derive nearly exact expressions of the packet delivery rate (PDR) under these scenarios based on our proposed framework. The comparison of the obtained packet delivery rate estimation in the various cooperation scenarios suggests that even a modest level of node cooperation (probabilistic cooperation with a low probability of cooperation) is sufficient to achieve 2-fold performance improvement with respect to the most pessimistic scenario in which all potential forwarders drop packets.
Article
Delay Tolerant Networks (DTNs) are a class of emerging networks that experience frequent and long-duration partitions. Delay is inevitable in DTNs, so ensuring the validity and reliability of the message transmission and making better use of buffer space are more important than concentrating on how to decrease the delay. In this paper, we present a novel routing protocol named Location and Direction Aware Priority Routing (LDPR) for DTNs, which utilizes the location and moving direction of nodes to deliver a message from source to destination. A node can get its location and moving direction information by receiving beacon packets periodically from anchor nodes and referring to received signal strength indicator (RSSI) for the beacon. LDPR contains two schemes named transmission scheme and drop scheme, which take advantage of the nodes' information of the location and moving direction to transmit the message and store the message into buffer space, respectively. Each message, in addition, is branded a certain priority according to the message's attributes (e.g. importance, validity, security and so on). The message priority decides the transmission order when delivering the message and the dropping sequence when the buffer is full. Simulation results show that the proposed LDPR protocol outperforms epidemic routing (EPI) protocol, prioritized epidemic routing (PREP) protocol, and DTN hierarchical routing (DHR) protocol in terms of packet delivery ratio, normalized routing overhead and average end-to-end delay. It is worth noting that LDPR doesn't need infinite buffer size to ensure the packet delivery ratio as in EPI. In particular, even though the buffer size is only 50, the packet delivery ratio of LDPR can still reach 93.9%, which can satisfy general communication demand. We expect LDPR to be of greater value than other existing solutions in highly disconnected and mobile networks.
Article
In most of dynamic Ad hoc sensor wireless applications ( e.g. military networks, vehicular ad hoc networks, wild life tracking sensor network), it is not possible to sustain an uninterrupted path from source to destination. Hence the traditional routing strategies (TCP/IP) cannot be deployed as they have to establish complete path before transmission.DTN (disruption-tolerant network) has emerged as technology which enables the communication by intermittently connected nodes. A node in DTN may not able to transmit all messages from its forwarding queue due to limited transmission duration, dynamic topology changes and network partitioning. Therefore, the order in which the messages are forwarded becomes very important.In this paper we propose a new message forwarding queue mode to optimize the performance of Epidemic router in terms of delivery probability. This technique is called as Transmit smallest message first (TSMF). Through simulations we prove that proposed queue mode (TSMF) out performs well as compared to existing FIFO and RANDOM.
Article
Mobile ad hoc routing protocols allow nodes with wireless adaptors to communicate with one another without any pre-existing network infrastructure. Existing ad hoc routing protocols, while robust to rapidly changing network topology, assume the presence of a connected path from source to destination. Given power limitations, the advent of short-range wireless networks, and the wide physical conditions over which ad hoc networks must be deployed, in some scenarios it is likely that this assumption is invalid. In this work, we develop techniques to deliver messages in the case where there is never a connected path from source to destination or when a network partition exists at the time a message is originated. To this end, we introduce Epidemic Routing, where random pair-wise exchanges of messages among mobile hosts ensure eventual message delivery. The goals of Epidemic Routing are to: i) maximize message delivery rate, ii) minimize message latency, and iii) minimize the total...