Networked sensors-those that coordinate amongst them-selves to achieve a larger sensing task-will revolutionize information gathering and processing both in urban envi-ronments and in inhospitable terrain. The sheer numbers of these sensors and the expected dynamics in these environ-ments present unique challenges in the design of unattended autonomous sensor networks. These challenges lead us to hypothesize that sensor network coordination applications may need to be structured differently from traditional net-work applications. In particular, we believe that localized algorithms (in which simple local node behavior achieves a desired global objective) may be necessary for sensor net-work coordination. In this paper, we describe localized al-gorithms, and then discuss directed diffusion, a simple com-munication model for describing localized algorithms. 1

Abstract—Recently, many overlay applications have emerged in the Internet, such as peer-to-peer file sharing, end host multicasting, and content distribution network. Currently, each of these applications requires their proprietary functionality support, such as network topology discovery, routing path selection, fault detection and tolerance, etc. A general unified framework may be a desirable alternative to application-specific overlays. In this paper, we introduce the concept of overlay brokers (OBs). We assume that each autonomous system in the Internet has one or more OBs. These OBs cooperate with each other to form an overlay service network (OSN) and provide overlay service support for overlay applications, such as resource allocation and negotiation, overlay routing, topology discovery, and other functionalities. The scope of our effort is the support of quality-of-service (QoS) in overlay networks. In this paper, our primary focus is on the design of QoSaware routing protocols for overlay networks (QRONs). The goal of QRON is to find a QoS-satisfied overlay path, while trying to balance the overlay traffic among the OBs and the overlay links in the OSN. A subset of OBs, connected by the overlay paths, can form an application specific overlay network for an overlay application. The proposed QRON algorithm adopts a hierarchical methodology that enhances its scalability. Two different types of path selection algorithms are analyzed in our paper. We have simulated the protocols based on the transit-stub topologies produced by GT-ITM. Simulation results have shown that the proposed algorithms perform well in providing QoS-aware overlay routing service. Index Terms—Modified shortest distance path (MSDP), overlay brokers (OBs), overlay routing, overlay service network (OSN), proportional bandwidth shortest path (PBSP), quality-of-service (QoS)-aware routing in overlay networks (QRONs), QoS satisfaction ratio. I.

Abstract. The efficient subdivision of a sensor network into uniform, mostly non-overlapping clusters of physically close nodes is an important building block in the design of efficient upper layer network functions such as routing, broadcast, data aggregation, and query processing. We present ACE, an algorithm that results in highly uniform cluster formation that can achieve a packing efficiency close to hexagonal close-packing. By using the self-organizing properties of three rounds of feedback between nodes, the algorithm induces the emergent formation of clusters that are an efficient cover of the network, with significantly less overlap than the clusters formed by existing algorithms. The algorithm is scale-independent — it completes in time proportional to the deployment density of the nodes regardless of the overall number of nodes in the network. ACE requires no knowledge of geographic location and requires only a small constant amount of communications overhead. 1

In this paper, we present a middleware architecture for coordination services in sensor networks that facilitates interaction between groups of sensors which monitor different environmental events. It sits on top of the native routing infrastructure and exports the abstraction of mobile communication endpoints maintained at the locations of such events. A single logical destination is created and maintained for every environmental event of interest. Such destinations are uniquely labeled and can be used for communication by application-level algorithms for coordination and sensory data management between the different event locales. For example, they may facilitate coordination, in a distributed intrusion scenario, among nodes in the vicinity of the intruders.

A scalable object location service can enable users to search for various objects in an environment where many small, networked devices are attached to objects. We investigate two hierarchical, self-configuring or unattended approaches for an eficient object location service. Each approach has its advantages and disadvantages based on the anticipated load. The first approach, SCOUT-AGG, is based on aggregation of object names. The second approach, SCOUT-MAE is based on indirection, where information about an object is stored at the locator sensor for the object. The relative efJiciency of SCOUT-AGG and SCOUT-MAP can be characterized by the query to mobilit>l update rate of the system. SCOUT-AGG performs better for low query to update rate but its performance deteriorates in general relative to SCOUT-MAP as the query to update rate increases. The rate of performance deterioration depends on query specijicity (i.e., queries for a specific object or for any object of a particular t>lpe). SCOUT-MAP generally exhibits better load balancing than SCOUT-AGG for various scenarios. We support the above results through simple analytical modeling and siniulation. 1.

Wireless Sensor Networks (WSNs) are being designed to solve a gamut of interesting real-world problems. Limitations on available energy and bandwidth, message loss, high rates of node failure, and communication restrictions pose challenging requirements for these systems. Beyond these inherent limitations, both the possibility of node mobility and energy conserving protocols that power down nodes introduce additional complexity to routing protocols that depend on up to date routing or neighborhood tables. Such state-based protocols suffer excessive delay or message loss, as system dynamics require expensive upkeep of these tables. Utilizing characteristics of high node density and location awareness, we introduce IGF, a location-aware routing protocol that is robust and works without knowledge of the existence of neighboring nodes (state-free). We compare our work against established routing protocols to demonstrate the efficacy of our solution when nodes are mobile or periodically sleep to conserve energy. We show that IGF far outperforms these protocols, in some cases delivering close to 100% of the packets transmitted while alternate solutions fail to even find a path between a source and destination. Specifically, we show that our protocol demonstrates a vast improvement over prior work using metrics of delivery ratio, control overhead, and end-to-end delay.

We present a troubleshooting approach for coordinating problem diagnosis, and describe Global Distributed Troubleshooting (GDT), a distributed protocol which realizes this approach. We show through simulation that GDT scales well as the number of observers and problems grows.

When an ATM node discovers that it cannot continue the setup of a virtual channel under the requested Quality of Service (QoS), it initiates a backtracking procedure called “crankback. ” We propose a novel scheme, referred to as crankback prediction, that decreases the crankback overhead. Under the proposed scheme, nodes check during the connection admission control procedure whether the establishment of a virtual channel has a good chance to be admitted over the entire designated route. If this is not the case, crankback is initiated even before a particular QoS parameter is violated. The main idea behind the proposed scheme is to allocate a “quota ” to the Peer Groups (PGs) along the message path, and then to suballocate this quota to the child PGs of these PGs. This process continues recursively until reaching the 1-level PG, which contains only physical nodes. The main advantage of the proposed scheme is that it lowers the setup delay and the processing and communication load imposed by signaling messages that establish unused portions of Virtual Channels (VCs)

Hierarchical routing (HR) has been touted as one of the major point-to-point routing techniques for large wireless sensor networks (WSNs). Yet, in contrast to numerous theoretical analyzes and high-level simulations, little work has been done to evaluate this technique in realistic WSN settings and to compare various proposed protocols. We fill this gap in this paper. Based on the analysis of a few tens of proposed HR infrastructures, we develop a framework that captures the common characteristics of the infrastructures and at the same time identifies various design points where the infrastructures differ. We then evaluate the implementation of the framework on a 60-node testbed and in TOSSIM. Our results demonstrate how HR performs in practice, how such performance diverges from high-level simulation results, and how it is affected by different design decisions in different infrastructures. Ultimately, our goal is to identify under which circumstances HR can be practical in WSNs.

The deployment of sensor networks in security- and safety-critical environments requires secure communication primitives. In this paper, we design, implement, and evaluate a new secure routing protocol for sensor networks. Our protocol requires no special hardware and provides message delivery even in an environment with active adversaries. We adopt a clean-slate approach and design a new sensor network routing protocol with security and efficiency as central design parameters. Our resulting protocol is efficient yet highly resilient to active attacks. We demonstrate the performance of our algorithms with results from extensive simulations as well as an implementation on Telos sensor nodes.