Showing papers in "IEEE Network in 2004"

Time synchronization in sensor networks: a survey

Abstract: Time synchronization is an important issue in multihop ad hoc wireless networks such as sensor networks. Many applications of sensor networks need local clocks of sensor nodes to be synchronized, requiring various degrees of precision. Some intrinsic properties of sensor networks, such as limited resources of energy, storage, computation, and bandwidth, combined with potentially high density of nodes make traditional synchronization methods unsuitable for these networks. Hence, there has been an increasing research focus on designing synchronization algorithms specifically for sensor networks. This article reviews the time synchronization problem and the need for synchronization in sensor networks, then presents in detail the basic synchronization methods explicitly designed and proposed for sensor networks.

Middleware to support sensor network applications

Abstract: Current trends in computing include increases in both distribution and wireless connectivity, leading to highly dynamic, complex environments on top of which applications must be built. The task of designing and ensuring the correctness of applications in these environments is similarly becoming more complex. The unified goal of much of the research in distributed wireless systems is to provide higher-level abstractions of complex low-level concepts to application programmers, easing the design and implementation of applications. A new and growing class of applications for wireless sensor networks require similar complexity encapsulation. However, sensor networks have some unique characteristics, including dynamic availability of data sources and application quality of service requirements, that are not common to other types of applications. These unique features, combined with the inherent distribution of sensors, and limited energy and bandwidth resources, dictate the need for network functionality and the individual sensors to be controlled to best serve the application requirements. In this article, we describe different types of sensor network applications and discuss existing techniques for managing these types of networks. We also overview a variety of related middleware and argue that no existing approach provides all the management tools required by sensor network applications. To meet this need, we have developed a new middleware called MiLAN. MiLAN allows applications to specify a policy for managing the network and sensors, but the actual implementation of this policy is effected within MiLAN. We describe MiLAN and show its effectiveness through the design of a sensor-based personal health monitor.

Optical burst switching: a new area in optical networking research

Abstract: In this tutorial, we give an introduction to optical burst switching and compare it with other existing optical switching paradigms. Basic burst assembly algorithms and their effect on assembled burst traffic characteristics are described first. Then a brief review of the early work on burst transmission is provided, followed by a description of a prevailing protocol for OBS networks called just-enough-time (JET). Algorithms used as an OBS core node for burst scheduling as well as contention resolution strategies are presented next. Trade-offs between their performance and implementation complexities are discussed. Recent work on QoS support, IP/WDM multicast, TCP performance in OBS networks, and labeled OBS is also described, and several open issues are mentioned.

Movement control algorithms for realization of fault-tolerant ad hoc robot networks

Abstract: Autonomous and semi-autonomous mobile multirobot systems require a wireless communication network in order to communicate with each other and collaboratively accomplish a given task. A multihop communications network that is self-forming, self-healing, and self-organizing is ideally suited for such mobile robot systems that exist in unpredictable and constantly changing environments. However, since every node in a multihop (or ad hoc) network is responsible for forwarding packets to other nodes, the failure of a critical node can result in a network partition. Hence, it is ideal to have an ad hoc network configuration that can tolerate temporary failures while allowing recovery. Since movement of the robot nodes is controllable, it is possible to achieve such fault-tolerant configurations by moving a subset of robots to new locations. In this article we propose a few simple algorithms for achieving the baseline graph theoretic metric of tolerance to node failures, namely, biconnectivity. We formulate an optimization problem for the creation of a movement plan while minimizing the total distance moved by the robots. For one-dimensional networks, we show that the problem of achieving a biconnected network topology can be formulated as a linear program; the latter lends itself to an optimal polynomial time solution. For two-dimensional networks the problem is much harder, and we propose efficient heuristic approaches for achieving biconnectivity. We compare the performance of the proposed algorithms with each other with respect to the total distance moved metric using simulations.

Positioning in ad hoc sensor networks

Abstract: Position and orientation of individual nodes in ad hoc sensor networks are useful for both service and application implementation. Services that can be enabled by availability of position include routing and querying. At application level, position is required in order to label the reported data in a sensor network, whereas position and orientation enable tracking. Nodes may have local capabilities such as the possibility of measuring ranges to neighbors, angle of arrival, or global capabilities, such as GPS and digital compasses. This article surveys methods used to infer locations in a multihop fashion in networks with or without the mentioned capabilities.

Building a reference combinatorial model for MANETs

Abstract: Wireless technologies and the deployment of mobile and nomadic services are driving the emergence of complex ad hoc networks that have a highly dynamic behavior. Modeling such dynamics and creating a reference model on which results could be compared and reproduced, was stated as a fundamental issue by a recent NSF workshop on networking. In this article we show how the modeling of time-changes unsettles old questions and allows for new insights into central problems in networking, such as routing metrics, connectivity, and spanning trees. Such modeling is made possible through evolving graphs, a simple combinatorial model that helps capture the behavior or dynamic networks over time.

Transmission power control in wireless ad hoc networks: challenges, solutions and open issues

Abstract: Recently, power control in mobile ad hoc networks has been the focus of extensive research. Its main objectives are to reduce the total energy consumed in packet delivery and/or increase network throughput by increasing the channel's spatial reuse. In this article, we give an overview of various power control approaches that have been proposed in the literature. We discuss the factors that influence the selection of the transmission power, including the important interplay between the routing (network) and the medium access control (MAC) layers. Protocols that account for such interplay are presented.

Issues in designing middleware for wireless sensor networks

Abstract: Wireless sensor networks are being developed for a variety of applications. With the continuing advances in network and application design, appropriate middleware is needed to provide both standardized and portable system abstractions, and the capability to support and coordinate concurrent applications on sensor networks. In this article, we first identify several design principles for such middleware. These principles motivate a cluster-based lightweight middleware framework that separates application semantics from the underlying hardware, operating system, and network infrastructure. We propose a layered architecture for each cluster that consists of a cluster control layer and a resource management layer. Key design issues and related challenges within this framework that deserve further investigation are outlined. Finally, we discuss a technique for energy-efficient resource allocation in a single-hop cluster, which serves as a basic primitive for the development of the resource management layer.

A review of fault management in WDM mesh networks: basic concepts and research challenges

Abstract: The article first presents a broad overview of the fault management mechanisms involved in deploying a survivable optical mesh network which employs optical crossconnects. We review various protection and restoration schemes, primary and back-up route computation methods, shareability optimization, and dynamic restoration. We then describe different parameters that can measure the quality of service provided by a WDM mesh network to upper protocol layers (e.g., IP network backbones, ATM network backbones, leased lines, virtual private networks), such as service availability, service reliability, restoration time, and service restorability. We review these concepts, the factors that affect them, and how to improve them. In particular, we present a framework for cost-effective availability-aware connection provisioning to provide differentiated services in WDM mesh networks. Through the framework, the more realistic scenario of multiple near-simultaneous failures can be handled. In addition, the emerging problem of protecting low-speed connections of different bandwidth granularities is also reviewed.

Feasibility of IP restoration in a tier 1 backbone

Abstract: Large IP networks usually combine protection and restoration mechanisms at various layers of the protocol stack to minimize service disruption in the event of failures. Sprint has chosen an IP-based restoration approach for building a highly available tier 1 IP backbone. This article describes the design principles of Sprint's network that makes IP-based restoration an effective and cost-efficient approach. The effectiveness of IP-based restoration is evaluated by analyzing network failure characteristics, and measuring disruptions in service availability during controlled failure experiments in the backbone. Current trends for improving the performance of IP-based restoration are also discussed.

Mobility support in IP: a survey of related protocols

Abstract: This article presents an overview of a set of IP-based mobility protocols mobile IP, HAWAII, cellular IP, hierarchical MIP, TeIeMIP, dynamic mobility agent, and terminal independent MIP - that will play an important role in the forthcoming convergence of IP and legacy wireless networks A comparative analysis with respect to system parameters such as location update, handoff latency and signaling overhead exposes their ability in managing micro/macro/global-level mobility We use this observation to relate their features against a number of key design issues identified for seamless IP-based mobility as envisioned for future 4G networks

Mobile ad hoc networks - current approaches and future directions

Abstract: Most research efforts in the area of MANETs focus on developing efficient routing protocols. Although routing protocols assume unique node addresses, the question of how to provide them remains open. In order to allow truly spontaneous and infrastructureless networking, a protocol for dynamic allocation of unique addresses is needed. Recently, various address autoconfiguration protocols for MANETs have been proposed. This article gives an overview of the challenges of address autoconfiguration in MANETs, presents current approaches, and discusses their advantages and drawbacks.

Composite event detection as a generic middleware extension

Abstract: Event-based communication provides a flexible and robust approach to monitoring and managing large-scale distributed systems. Composite event detection extends the scope and flexibility of these systems by allowing application components to express interest in complex patterns of events. This makes it possible to handle the large numbers of events generated in Internet-wide systems, and in network monitoring and pervasive computing applications. In this article, we introduce a novel generic composite event detection framework that can be added on top of existing middleware architectures, as demonstrated in our implementation over JMS. We argue that the framework is flexible, expressive and easy to implement. Based on finite state automata extended with a rich time model and parameterization support, it provides a decomposable core language for specifying composite events. This allows detection to be distributed automatically throughout the system, guided by distribution policies that control the quality of service. Finally, tests show that using our composite event system over JMS can reduce bandwidth consumption while maintaining low notification delay for composite events.

Scalable geographic routing algorithms for wireless ad hoc networks

Abstract: The design of efficient routing protocols for dynamical changing network topologies is a crucial part of building power-efficient and scalable ad hoc wireless networks. If position information is available due to GPS or some kind of relative positioning technique, a promising approach is given by geographic routing algorithms, where each forwarding decision is based on the positions of current, destination, and possible candidate nodes in vicinity only. About 15 years ago heuristic greedy algorithms were proposed, which in order to provide freedom from loops might fail even if there is a path from source to destination. In recent years planar graph traversal has been investigated as one possible strategy to recover from such greedy routing failures. This article provides a tutorial for this class of geographic routing algorithms, and discusses recent improvements to both greedy forwarding and routing in planar graphs.

Wireless sensor networks: leveraging the virtual infrastructure

Abstract: Overlaying a virtual infrastructure over a physical network is a time-honored strategy for conquering scale. We design a general-purpose virtual architecture for wireless sensor networks and show that it can be leveraged by a number of different protocols.

Performance evaluation of constraint-based path selection algorithms

Abstract: Constraint-based path selection is an invaluable part of a full-fledged quality of service (QoS) architecture. Internet service providers want to be able to select paths for QoS flows that optimize network utilization and satisfy user requirements and as such increase revenues. Unfortunately, finding a path subject to multiple constraints is known to be an NP-complete problem. Hence, accurate constraint-based path selection algorithms with a fast running time are scarce. Numerous heuristics and a few exact algorithms have been proposed. In this article we compare most of these algorithms. We focus on the restricted shortest path algorithms and multi-constrained path algorithms. The performance evaluation of these two classes of algorithms is presented based on complexity analysis and simulation results and may shed some light on the difficult task of selecting the proper algorithm for a QoS-capable network.

The IEEE 802.17 media access protocol for high-speed metropolitan-area resilient packet rings

Abstract: The resilient packet ring (RPR) IEEE 802.17 standards is under development as a new high-speed technology for metropolitan backbone networks. A key performance objective of PRP is to simultaneously achieve high utilization, spatial reuse, and fairness, an objective not achieved by current technologies such as SONET and Gigabit Ethernet or legacy ring technologies, such as FDDI. The core technical challenge for RPR is the design of a fairness algorithm that dynamically throttles traffic to achieve these properties. The difficulty is in the distributed nature of the problem, that upstream ring nodes must inject traffic at a rate according to congestion and fairness criteria downstream. This article provides an overview of the RPR protocol with a focus on medium access and fairness.

Failure protection in layered networks with shared risk link groups

Abstract: The shared risk link group (SRLG) has been widely recognized as a fundamental concept in layered network design by the industry. However, several issues related to SRLG protections that are of both theoretical interest and practical importance have not been explored fully. Two major issues are avoiding failures caused by "traps" in finding backup paths, and minimizing the total network capacity requested by active and backup paths. In this article, we highlight the significance of the trap problem in layered networks with SRLG and evaluate the performance of several existing SRLG protection schemes in terms of trap avoidance and bandwidth efficiency, as well as their complexities. We also demonstrate that a simple yet intelligent heuristic algorithm can achieve good performance.

Hamiltonian p-cycles for fiber-level protection in semi-homogeneous homogeneous and optical networks

Abstract: Recently there has been interest in DWDM-based optical networks that are assumed to employ exactly two working fibers uniformly on every span (or "link"). At the fiber level such networks are referred to as homogeneous networks. An interesting and highly efficient strategy for protection of such networks is to use a single dark-fiber p-cycle formed on a Hamiltonian cycle (if it exists). We show that in a homogeneous Hamiltonian network, a Hamiltonian p-cycle is the most efficient overall solution, although interestingly it does not always correspond to the individually most efficient p-cycle that can be formed. We also consider p-cycle planning in non-Hamiltonian but homogeneous networks and introduce the concept of a semi-homogenous network, specifically linked to the p-cycle concept. The proposed semi-homogeneous class of network actually realizes the theoretical lower bound on span-restorable networks in terms of network redundancy. Such networks also provide a strategy to accommodate certain patterns of capacity growth beyond a homogenous network without any increase in protection capacity. The work also demonstrates and explains why a single Hamiltonian p-cycle is not as efficient as a specifically optimized set of individual p-cycles in a "capacitated" (non-homogeneous) network where the working capacity on each span varies in a general way. These discussions provide new options for DWDM network architecture and also clarify some possible confusions about the applicability of Hamiltonian p-cycles and generalized sets of p-cycles.

An econometric model for resource management in competitive wireless data networks

Abstract: This article investigates the role and importance of the economic aspects that are vital to the success of wireless services deployment and provider selection by users in a competitive environment. We show how some of the econometric measures can meaningfully capture the user decisions/actions (e.g., churning) that can potentially be utilized by the providers in managing radio resources (e.g., bandwidth) in wireless data networks. In particular, by modeling the interaction between a service provider and its customers (or users) as a non-cooperative game, we propose a novel cross-layer resource management framework for integrated admission and rate control in CDMA networks. Analytical and simulation results demonstrate how the proposed framework can help minimize customer churning and maximize revenue for the wireless operators, yet optimizing customer satisfaction by providing differentiated quality of service to different classes of users.

Exploiting user profiles to support differentiated services in next-generation wireless networks

Abstract: In the next-generation wireless network, user profiles such as the location, the velocity (both speed and direction), and the resource requirements of the mobile device can be accurately determined and maintained by the network on a per-user basis. We investigate the design of a wireless network architecture that exploits user profiles to maximize network efficiency and provide better quality-of-service (QoS) to different classes of users. In this article we provide implementation guidelines of such an architecture for the third-generation partnership project (3GPP) network. The key underlying primitive of the architecture is the use of both real-time and aggregate user profiles to perform advance resource reservation in the handoff target cells of the wireless cellular network. We identify various factors that can influence the efficiency of the resource reservation scheme, and through a simulation analysis of an example scenario we show the impact of these factors on the QoS that profiled users receive. The example scenario comprises two service classes: a high cost, profiled service with higher QoS; and a lower cost, non-profiled service with best-effort QoS. The results show that high QoS can be guaranteed to users who subscribe to the profiled service.

A methodology for the design of distributed search in P2P middleware

Abstract: Important research efforts are being conducted in the area of search, lookup, and routing, and are even increasing in the quest for P2P middleware that is both scalable and decentralized. To structure and classify current as well as facilitate and give direction to future research, this methodology proposes a top-down two-dimensional design space. This design space has been developed for exhaustiveness so as to cover all possible design options, existing or yet to be conceived. A comprehensive survey of P2P search systems serves as a reference for the reader while at the same time validating the framework. An identification of areas in the design space not covered by current systems leads to the design of a novel peer-to-peer-based keyword routing scheme. Finally, an evaluation of possible design options along the most important requirement will help guide system designers.

An architecture for scalable, efficient, and fast fault-tolerant multicast provisioning

Abstract: Providing fault tolerance to multicast connections is an important and challenging requirement of future networks. The existing techniques for fault-tolerant multicast can be grouped into on-demand and preplanned approaches. On-demand approaches can have long recovery latency. For faster recovery, preplanned approaches have been developed. However, in this type of approach the overhead cost is generally very high, especially when there is a large number of simultaneous groups in the network. In this paper first we provide an overview of the current multicast fault tolerance method . In add, on, we propose a novel architecture called Aggregated MPLS-Based Fault-Tolerant Multicast (AMFM) for scalable, efficient, and fast fault-tolerant multicast provisioning. AMFM falls in the category of preplanned approaches. Using the concept of aggregated multicast, AMFM facilitates fault tolerance in a very elegant way: it reduces the protection cost significantly; it is scalable to large numbers of groups; and it can also recover from failure in a very fast manner. This article describes the architecture of AMFM and provides a feasibility check from an implementation point of view. We also conduct experiments to evaluate the performance of AMFM and show it can provide fault tolerance in a scalable fashion.

Positioning of the RPR standard in contemporary operator environments

Abstract: This article deals with the fundamentals and current standardization efforts for IEEE 802.17 resilient packet ring. Its special resilience features make this technology robust against outages of the network infrastructure. The goals of this article are threefold. First, the fundamentals of RPR and the standardization process carried out under the auspices of IEEE and ITU are overviewed. Second, potentially hazardous situations involving traffic assignments are defined and illustrated. Finally, possible situations where the simplicity, enhanced throughput, and automatic resilience features of RPR may be advantageous for network operators are identified.

Scalable monitoring support for resource management and service assurance

Abstract: Continuous monitoring of network status and its resources are necessary to ensure proper network operation. Deployment of QoS-based value-added services in IP networks necessitates the employment of resource management techniques and specifically the use of traffic engineering. The latter typically relies on monitoring data for both offline proactive and dynamic reactive solutions. The variety of data to be collected and analyzed using different measurement methods and tools, and the extent of monitoring information to use demand a proper QoS monitoring infrastructure. A monitoring system should be scalable in terms of network size, speed, and number of customers subscribed to value-added services. This article investigates the requirements of scalable monitoring system architectures, proposes principles for designing such systems, and validates them through the design and implementation of a scalable monitoring system for QoS delivery in IP differentiated services networks. Experimental assessment results prove the accuracy and scalability of the proposed monitoring system.

A framework for resilient Internet routing protocols

Abstract: At a fundamental level, all Internet-based applications rely on a dependable packet delivery service provided by the Internet routing infrastructure. However, the Internet is a large-scale complex loosely coupled distributed system made of many imperfect components. Faults of varying-scale and severity occur from time to time. In this paper we survey the research efforts over the years aimed at enhancing the dependability of the routing infrastructure. To provide a comprehensive overview of the various efforts, we first introduce a threat model based on known threats, then sketch out a defense framework, and put each of the existing efforts at appropriate places in the framework based on the faults and attacks against which it can defend. Our analysis shows that although individual defense mechanisms may effectively guard against specific faults, no single fence can counter all faults. Thus, a resilient Internet routing infrastructure calls for integrating techniques from cryptographic protection mechanisms, statistical anomaly detection, protocol syntax checking, and protocol semantics checking to build a multifence defense system.

Real-time visualization of network attacks on high-speed links

Abstract: This article shows that malicious traffic flows such as denial-of-service attacks and various scanning activities can be visualized in an intuitive manner. A simple but novel idea of plotting a packet using its source IP address, destination IP address, and the destination port in a 3-dimensional space graphically reveals ongoing attacks. Leveraging this property, combined with the fact that only three header fields per each packet need to be examined, a fast attack detection and classification algorithm can be devised.

A classification of reliable multicast protocols

Abstract: The range of user requirements on multicast protocols is so wide that no single protocol will ever satisfy them. The set of multicast protocols can be classified using the user requirements, and the architectures, mechanisms, communications patterns, and policies used to satisfy these requirements. We provide such a classification, and illustrate it with several example protocols chosen to cover the range of features described.

SONET/SDH-like resilience for IP networks: a survey of traffic protection mechanisms

Abstract: Typically IP networks respond to a link failure by finding an alternate traffic path after the failure is discovered. This results in a convergence time during which traffic may be dropped at the failed link until an alternate path is found (e.g., through link state routing protocols like OSPF or IS-IS). While there has been steady progress in decreasing IP routing convergence times, these approaches are limited by the need to communicate among multiple routers. However, IP traffic can be protected using techniques below layer 3, which are not subject to this constraint. This article discusses mechanisms where a link failure can be protected locally, SONET/SDH-like, at sub-50-ms protection times. Descriptions of linear SONET automatic protection switching for routers, resilient packet ring protection, IP interface bundling, and MPLS fast reroute are covered. Protection triggers and coexistence of various protection methods are also discussed.

Software tools for networking

Abstract: Sexually transmitted diseases (STDs) threaten mens reproductive health but they are preventable. When the means to prevent STDs are unknown unavailable unused or fail STDs can threaten the health and fertility of both men and their sex partners. Other threats such as environmental toxins which may affect mens offspring or reduce sperm count and consequently fertility have not been consistently identified. If these latter threats exist they may be preventable. Other reproductive system conditions such as prostate and testicular cancer may or may not be preventable but they pose no risk to others. Since the advent of AIDS greater attention has been focused upon STDs as primary reproductive health threats. STDs STD-related infertility how male reproductive health status affects family health environmental threats to male fertility prostate cancer and testicular cancer are discussed.