Showing papers on "Communications protocol published in 2005"

Protocols and Architectures for Wireless Sensor Networks

Abstract: Preface. List of Abbreviations. A guide to the book. 1. Introduction. 1.1 The vision of Ambient Intelligence. 1.2 Application examples. 1.3 Types of applications. 1.4 Challenges for WSNs. 1.5 Why are sensor networks different? 1.6 Enabling technologies. PART I: ARCHITECTURES. 2. Single node architecture. 2.1 Hardware components. 2.2 Energy consumption of sensor nodes. 2.3 Operating systems and execution environments. 2.4 Some examples of sensor nodes. 2.5 Conclusion. 3. Network architecture. 3.1 Sensor network scenarios. 3.2 Optimization goals & figures of merit. 3.3 Design principles for WSNs. 3.4 Service interfaces of WSNs. 3.5 Gateway concepts. 3.6 Conclusion. PART II: COMMUNICATION PROTOCOLS. 4. Physical Layer. 4.1 Introduction. 4.2 Wireless channel and communication fundamentals. 4.3 Physical layer & transceiver design considerations in WSNs. 4.4 Further reading. 5. MAC Protocols 133 5.1 Fundamentals of (wireless) MAC protocols. 5.2 Low duty cycle protocols and wakeup concepts. 5.3 Contention-based protocols. 5.4 Schedule-based protocols. 5.5 The IEEE 802.15.4 MAC protocol. 5.6 How about IEEE 802.11 and Bluetooth? 5.7 Further reading. 5.8 Conclusion. 6. Link Layer Protocols. 6.1 Fundamentals: Tasks and requirements. 6.2 Error control. 6.3 Framing. 6.4 Link management. 6.5 Summary. 7. Naming and Addressing. 7.1 Fundamentals. 7.2 Address and name management in wireless sensor networks. 7.3 Assignment of MAC addresses. 7.4 Distributed assignment of locally unique addresses. 7.5 Content-based and geographic addressing. 7.6 Summary. 8. Time Synchronization. 8.1 Introduction to the time synchronization problem. 8.2 Protocols based on sender/receiver synchronization. 8.3 Protocols based on receiver/receiver synchronization. 8.4 Further reading. 9. Localization and Positioning. 9.1 Properties of positioning. 9.2 Possible approaches. 9.3 Mathematical basics for the lateration problem. 9.4 Single-hop localization. 9.5 Positioning in multi-hop environments. 9.6 Impact of anchor placement. 9.7 Further reading. 9.8 Conclusion. 10. Topology control 295 10.1 Motivation and basic ideas. 10.2 Flat network topologies. 10.3 Hierarchical networks by dominating sets. 10.4 Hierarchical networks by clustering. 10.5 Combining hierarchical topologies and power control. 10.6 Adaptive node activity. 10.7 Conclusions. 11. Routing protocols. 11.1 The many faces of forwarding and routing. 11.2 Gossiping and agent-based unicast forwarding. 11.3 Energy-efficient unicast. 11.4 Broadcast and multicast. 11.5 Geographic routing. 11.6 Mobile nodes. 11.7 Conclusions. 12. Data-centric and content-based networking 395. 12.1 Introduction. 12.2 Data-centric routing. 12.3 Data aggregation. 12.4 Data-centric storage. 12.5 Conclusions. 13. Transport Layer and Quality of Service. 13.1 The transport layer and QoS in wireless sensor networks. 13.2 Coverage and deployment. 13.3 Reliable data transport. 13.5 Block delivery. 13.6 Congestion control and rate control. 14. Advanced application support. 14.1 Advanced in-network processing. 14.2 Security. 14.3 Application-specific support. Bibliography. Index.

On the lifetime of wireless sensor networks

Abstract: We derive a general formula for the lifetime-of wireless sensor networks which holds independently of the underlying network model including network architecture and protocol, data collection initiation, lifetime definition, channel fading characteristics, and energy consumption model. This formula identifies two key parameters at the physical layer that affect the network lifetime: the channel state and the residual energy of sensors. As a result, it provides not only a gauge for performance evaluation of sensor networks but also a guideline for the design of network protocols. Based on this formula, we propose a medium access control protocol that exploits both the channel state information and the residual energy information of individual sensors. Referred to as the max-min approach, this protocol maximizes the minimum residual energy across the network in each data collection.

Balancing transport and physical Layers in wireless multihop networks: jointly optimal congestion control and power control

Abstract: In a wireless network with multihop transmissions and interference-limited link rates, can we balance power control in the physical layer and congestion control in the transport layer to enhance the overall network performance while maintaining the architectural modularity between the layers? We answer this question by presenting a distributed power control algorithm that couples with existing transmission control protocols (TCPs) to increase end-to-end throughput and energy efficiency of the network. Under the rigorous framework of nonlinearly constrained utility maximization, we prove the convergence of this coupled algorithm to the global optimum of joint power control and congestion control, for both synchronized and asynchronous implementations. The rate of convergence is geometric and a desirable modularity between the transport and physical layers is maintained. In particular, when congestion control uses TCP Vegas, a simple utilization in the physical layer of the queueing delay information suffices to achieve the joint optimum. Analytic results and simulations illustrate other desirable properties of the proposed algorithm, including robustness to channel outage and to path loss estimation errors, and flexibility in trading off performance optimality for implementation simplicity. This work presents a step toward a systematic understanding of "layering" as "optimization decomposition," where the overall communication network is modeled by a generalized network utility maximization problem, each layer corresponds to a decomposed subproblem, and the interfaces among layers are quantified as the optimization variables coordinating the subproblems. In the case of the transport and physical layers, link congestion prices turn out to be the optimal "layering prices.".

Bluetooth and Wi-Fi wireless protocols: a survey and a comparison

Abstract: Bluetooth and IEEE 802.11 (Wi-Fi) are two communication protocol standards that define a physical layer and a MAC layer for wireless communications within a short range (from a few meters up to 100 m) with low power consumption (from less than 1 mW up to 100 mW). Bluetooth is oriented to connecting close devices, serving as a substitute for cables, while Wi-Fi is oriented toward computer-to-computer connections, as an extension of or substitution for cabled LANs. In this article we offer an overview of these popular wireless communication standards, comparing their main features and behaviors in terms of various metrics, including capacity, network topology, security, quality of service support, and power consumption.

Federated multiprotocol communication

Abstract: Methods, apparatus, and business techniques are disclosed for use in distributed communication systems comprising a plurality of communication protocols. In one embodiment a first air interface is used to initiate communication between a wireless client and a remote server at least partially using a first wireless access point. The server sends the wireless client a stub of a distributed object. The stub is used to instantiate an object class. The object class defines an interface that the remote client can use to communicate with the remote server using an upper layer interface. The distributed object stub also provides an implementation of a software radio configuration for a set of lower protocol layers in a second air interface. The wireless client can thereby communicate with a second wireless access point using said second air interface protocol. Exemplary embodiments of the present invention are disclosed that focus on toll-tag and electronic-commerce related highway systems, distributed federated wireless access systems, and wide area wireless system capacity augmentation.

A scalable synchronization protocol for large scale sensor networks and its applications

Abstract: Synchronization is considered a particularly difficult task in wireless sensor networks due to its decentralized structure. Interestingly, synchrony has often been observed in networks of biological agents (e.g., synchronously flashing fireflies, or spiking of neurons). In this paper, we propose a bio-inspired network synchronization protocol for large scale sensor networks that emulates the simple strategies adopted by the biological agents. The strategy synchronizes pulsing devices that are led to emit their pulses periodically and simultaneously. The convergence to synchrony of our strategy follows from the theory of Mirollo and Strogatz, 1990, while the scalability is evident from the many examples existing in the natural world. When the nodes are within a single broadcast range, our key observation is that the dependence of the synchronization time on the number of nodes N is subject to a phase transition: for values of N beyond a specific threshold, the synchronization is nearly immediate; while for smaller N, the synchronization time decreases smoothly with respect to N. Interestingly, a tradeoff is observed between the total energy consumption and the time necessary to reach synchrony. We obtain an optimum operating point at the local minimum of the energy consumption curve that is associated to the phase transition phenomenon mentioned before. The proposed synchronization protocol is directly applied to the cooperative reach-back communications problem. The main advantages of the proposed method are its scalability and low complexity.

A protocol for packet network intercommunication

Abstract: A protocol that supports the sharing of resources that exist in different packet switching networks is presented. The protocol provides for variation in individual network packet sizes, transmission failures, sequencing, flow control, end-to-end error checking, and the creation and destruction of logical process-to-process connections. Some implementation issues are considered, and problems such as internetwork routing, accounting, and timeouts are exposed.

A unifying link abstraction for wireless sensor networks

Abstract: Recent technological advances and the continuing quest for greater efficiency have led to an explosion of link and network protocols for wireless sensor networks. These protocols embody very different assumptions about network stack composition and, as such, have limited interoperability. It has been suggested [3] that, in principle, wireless sensor networks would benefit from a unifying abstraction (or "narrow waist" in architectural terms), and that this abstraction should be closer to the link level than the network level. This paper takes that vague principle and turns it into practice, by proposing a specific unifying sensornet protocol (SP) that provides shared neighbor management and a message pool.The two goals of a unifying abstraction are generality and efficiency: it should be capable of running over a broad range of link-layer technologies and supporting a wide variety of network protocols, and doing so should not lead to a significant loss of efficiency. To investigate the extent to which SP meets these goals, we implemented SP (in TinyOS) on top of two very different radio technologies: B-MAC on mica2 and IEEE 802.15.4 on Telos. We also built a variety of network protocols on SP, including examples of collection routing [53], dissemination [26], and aggregation [33]. Measurements show that these protocols do not sacrifice performance through the use of our SP abstraction.

A spatiotemporal communication protocol for wireless sensor networks

Abstract: In this paper, we present a spatiotemporal communication protocol for sensor networks, called SPEED. SPEED is specifically tailored to be a localized algorithm with minimal control overhead. End-to-end soft real-time communication is achieved by maintaining a desired delivery speed across the sensor network through a novel combination of feedback control and nondeterministic geographic forwarding. SPEED is a highly efficient and scalable protocol for sensor networks where the resources of each node are scarce. Theoretical analysis, simulation experiments, and a real implementation on Berkeley motes are provided to validate the claims.

A disconnection-tolerant transport for drive-thru Internet environments

Abstract: Today's mobile, wireless, and ad-hoc communications often exhibit extreme characteristics challenging assumptions underlying the traditional way of end-to-end communication protocol design in the Internet. One specific scenario is Internet access from moving vehicles on the road as we are researching in the drive-thru Internet project. Using wireless LAN as a broadly available access technology leads to intermittent - largely unpredictable and usually short-lived - connectivity, yet providing high performance while available. To allow Internet applications to deal reasonably well with such intermittent connectivity patterns, we have introduced a supportive drive-thru architecture. A key component is a "session" protocol offering persistent end-to-end communications even in the presence of interruptions. In this paper, we present the design of the persistent connectivity management protocol (PCMP) and report on findings from our implementation.

Measuring the evolution of transport protocols in the internet

Abstract: In this paper we explore the evolution of both the Internet's most heavily used transport protocol, TCP, and the current network environment with respect to how the network's evolution ultimately impacts end-to-end protocols. The traditional end-to-end assumptions about the Internet are increasingly challenged by the introduction of intermediary network elements (middleboxes) that intentionally or unintentionally prevent or alter the behavior of end-to-end communications. This paper provides measurement results showing the impact of the current network environment on a number of traditional and proposed protocol mechanisms (e.g., Path MTU Discovery, Explicit Congestion Notification, etc.). In addition, we investigate the prevalence and correctness of implementations using proposed TCP algorithmic and protocol changes (e.g., selective acknowledgment-based loss recovery, congestion window growth based on byte counting, etc.). We present results of measurements taken using an active measurement framework to study web servers and a passive measurement survey of clients accessing information from our web server. We analyze our results to gain further understanding of the differences between the behavior of the Internet in theory versus the behavior we observed through measurements. In addition, these measurements can be used to guide the definition of more realistic Internet modeling scenarios. Finally, we present several lessons that will benefit others taking Internet measurements.

High data rate interface apparatus and method

Abstract: A data interface for transferring digital data between a host and a client over a communication path using packet structures linked together to form a communication protocol for communicating a pre-selected set of digital control and presentation data. The signal protocol is used by link controllers configured to generate, transmit, and receive packets forming the communications protocol, and to form digital data into one or more types of data packets, with at least one residing in the host device and being coupled to the client through the communications path. The interface provides a cost-effective, low power, bi-directional, high-speed data transfer mechanism over a short-range “serial” type data link, which lends itself to implementation with miniature connectors and thin flexible cables which are especially useful in connecting display elements such as wearable micro-displays to portable computers and wireless communication devices.

Redundant radio frequency network having a roaming terminal communication protocol

Abstract: Disclosed herein is a redundant network and communication protocol at least including host computers, RF base stations, and roaming terminals. The network may utilize a polling communication protocol such that under heavy traffic conditions, a roaming terminal wishing to initiate communication may be required to determine whether the channel is clear by listening for an entire interpoll gap time. When a hidden terminal is communicating, the roaming terminal may conclude that the communication is taking place upon receiving a polling frame directed to the hidden terminal from the normally silent base station. Inherent redundancy techniques may be used with a spanning tree approach for determining the most efficient pathways from a source to a destination and ensuring that the network adapts to spatial changes or breakdowns within the network.

Security Considerations for Voice Over IP Systems

Abstract: syntax notation one (ASN.1): A standard, flexible method that (a) describes data structures for representing, encoding, transmitting, and decoding data, (b) provides a set of formal rules for describing the structure of objects independent of machine-specific encoding techniques, (c) is a formal network- management Transmission Control Protocol/Internet Protocol (TCP/IP) language that uses human-readable notation and a compact, encoded representation of the same information used in communications protocols, and (d) is a precise, formal notation that removes ambiguities. Call Processor – component that sets up and monitors the state of calls, and provides phone number translation, user authorization, and coordination with media gateways. Codec – coder/decoder, which converts analog voice into digital data and back again, and may also compress and decompress the data for more efficient transmission. Firewall Control Proxy component that controls a firewall’s handling of a call. The firewall control proxy can instruct the firewall to open specific ports that are needed by a call, and direct the firewall to close these ports at call termination. H.323 The International Telecommunications Union (ITU) standard for packet- switched network voice and video calling and signaling. Jitter non-uniform delays that can cause packets to arrive and be processed out of sequence Latency – time delay in processing voice packets. Media gateway the interface between circuit switched networks and IP network. Media gateways handle analog/digital conversion, call origination and reception, and quality improvement functions such as compression or echo cancellation.

Vehicle Applications of Controller Area Network

Abstract: The Controller Area Network (CAN) is a serial bus communications protocol developed by Bosch in the early 1980s. It defines a standard for efficient and reliable communication between sensor, actuator, controller, and other nodes in real-time applications. CAN is the de facto standard in a large variety of networked embedded control systems. The early CAN development was mainly supported by the vehicle industry: CAN is found in a variety of passenger cars, trucks, boats, spacecraft, and other types of vehicles. The protocol is also widely used today in industrial automation and other areas of networked embedded control, with applications in diverse products such as production machinery, medical equipment, building automation, weaving machines, and wheelchairs.The purpose of this chapter is to give an introduction to CAN and some of its vehicle applications. The outline is as follows. Section 2 describes the CAN protocol, including its message formats and error handling. The section is concluded by a brief history of CAN. Examples of vehicle application architectures based on CAN are given in Section 3. A few specific control loops closed over CAN buses are discussed in Section 4. The paper is concluded with some perspectives in Section 5, where current research issues such as x-by-wire and standardized software architectures are considered. The examples are described in more detail in [14]. A detailed description of CAN is given in the textbook [6]. Another good resource for further information is the homepage of the organization CAN-in-Automation (CiA) [3]. The use of CAN as a basis for distributed control systems is discussed in [13].

Software Model Checking: The VeriSoft Approach

Abstract: Verification by state-space exploration, also often referred to as model checking, is an effective method for analyzing the correctness of concurrent reactive systems (for instance, communication protocols). Unfortunately, traditional model checking is restricted to the verification of properties of models, i.e., abstractions, of concurrent systems. We discuss in this paper how model checking can be extended to analyze arbitrary software, such as implementations of communication protocols written in programming languages like C or C++. We then introduce a search technique that is suitable for exploring the state spaces of such systems. This algorithm has been implemented in VeriSoft, a tool for systematically exploring the state spaces of systems composed of several concurrent processes executing arbitrary code. During the past five years, VeriSoft has been applied successfully for analyzing several software products developed in Lucent Technologies, and has also been licensed to hundreds of users in industry and academia. We discuss applications, strengths and limitations of VeriSoft, and compare it to other approaches to software model checking, analysis and testing.

Real-world environment models for mobile network evaluation

Abstract: Simulation environments are an important tool for the evaluation of new concepts in networking. The study of mobile ad hoc networks depends on understanding protocols from simulations, before these protocols are implemented in a real-world setting. To produce a real-world environment within which an ad hoc network can be formed among a set of nodes, there is a need for the development of realistic, generic and comprehensive mobility, and signal propagation models. In this paper, we propose the design of a mobility and signal propagation model that can be used in simulations to produce realistic network scenarios. Our model allows the placement of obstacles that restrict movement and signal propagation. Movement paths are constructed as Voronoi tessellations with the corner points of these obstacles as Voronoi sites. Our mobility model also introduces a signal propagation model that emulates properties of fading in the presence of obstacles. As a result, we have developed a complete environment in which network protocols can be studied on the basis of numerous performance metrics. Through simulation, we show that the proposed mobility model has a significant impact on network performance, especially when compared with other mobility models. In addition, we also observe that the performance of ad hoc network protocols is effected when different mobility scenarios are utilized.

A WBAN System for Ambulatory Monitoring of Physical Activity and Health Status: Applications and Challenges

Abstract: Recent technological advances in sensors, low-power integrated circuits, and wireless communications have enabled the design of low-cost, miniature, lightweight, intelligent physiological sensor platforms that can be seamlessly integrated into a body area network for health monitoring. Wireless body area networks (WBANs) promise unobtrusive ambulatory health monitoring for extended periods of time and near real-time updates of patients' medical records through the Internet. A number of innovative systems for health monitoring have recently been proposed. However, they typically rely on custom communication protocols and hardware designs, lacking generality and flexibility. The lack of standard platforms, system software support, and standards makes these systems expensive. Bulky sensors, high price, and frequent battery changes are all likely to limit user compliance. To address some of these challenges, we prototyped a WBAN utilizing a common off-the-shelf wireless sensor platform with a ZigBee-compliant radio interface and an ultra low-power microcontroller. The standard platform interfaces to custom sensor boards that are equipped with accelerometers for motion monitoring and a bioamplifier for electrocardiogram or electromyogram monitoring. Software modules for on-board processing, communication, and network synchronization have been developed using the TinyOS operating system. Although the initial WBAN prototype targets ambulatory monitoring of user activity, the developed sensors can easily be adapted to monitor other physiological parameters. In this paper, we discuss initial results, implementation challenges, and the need for standardization in this dynamic and promising research field

The TCP/IP Guide : A Comprehensive, Illustrated Internet Protocols Reference

Abstract: Filled with over 350 illustrations and hundreds of tables help to explain the finer points of this complex topic, this up-to-date guide details the core protocols that make TCP/IP internetworks function and the most important classic TCP/IP applications.

The state of the art in cross-layer design for wireless sensor networks

Abstract: The literature on cross-layer protocols, protocol improvements, and design methodologies for wireless sensor networks (WSNs) is reviewed and a taxonomy is proposed. The communication protocols devised for WSNs that focus on cross-layer design techniques are reviewed and classified, based on the network layers they aim at replacing in the classical open system interconnection (OSI) network stack. Furthermore, systematic methodologies for the design of cross-layer solution for sensor networks as resource allocation problems in the framework of non-linear optimization are discussed. Open research issues in the development of cross-layer design methodologies for sensor networks are discussed and possible research directions are indicated. Finally, possible shortcomings of cross-layer design techniques such as lack of modularity, decreased robustness, and instability are discussed, and precautionary guidelines are presented.

An efficient on-chip NI offering guaranteed services, shared-memory abstraction, and flexible network configuration

Abstract: We present a network interface (NI) for an on-chip network. Our NI decouples computation from communication by offering a shared-memory abstraction, which is independent of the network implementation. We use a transaction-based protocol to achieve backward compatibility with existing bus protocols such as AXI, OCP, and DTL. Our NI has a modular architecture, which allows flexible instantiation. It provides both guaranteed and best-effort services via connections. These are configured via NI ports using the network itself, instead of a separate control interconnect. An example instance of this NI with four ports has an area of 0.25 mm/sup 2/ after layout in 0.13-/spl mu/m technology, and runs at 500 MHz.

On the interdependence of distributed topology control and geographical routing in ad hoc and sensor networks

Abstract: Since ad hoc and sensor networks can be composed of a very large number of devices, the scalability of network protocols is a major design concern. Furthermore, network protocols must be designed to prolong the battery lifetime of the devices. However, most existing routing techniques for ad hoc networks are known not to scale well. On the other hand, the so-called geographical routing algorithms are known to be scalable but their energy efficiency has never been extensively and comparatively studied. In a geographical routing algorithm, data packets are forwarded by a node to its neighbor based on their respective positions. The neighborhood of each node is constituted by the nodes that lie within a certain radio range. Thus, from the perspective of a node forwarding a packet, the next hop depends on the width of the neighborhood it perceives. The analytical framework proposed in this paper allows to analyze the relationship between the energy efficiency of the routing tasks and the extension of the range of the topology knowledge for each node. A wider topology knowledge may improve the energy efficiency of the routing tasks but increases the cost of topology information due to signaling packets needed to acquire this information. The problem of determining the optimal topology knowledge range for each node to make energy efficient geographical routing decisions is tackled by integer linear programming. It is shown that the problem is intrinsically localized, i.e., a limited topology knowledge is sufficient to make energy efficient forwarding decisions. The leading forwarding rules for geographical routing are compared in this framework, and the energy efficiency of each of them is studied. Moreover, a new forwarding scheme, partial topology knowledge forwarding (PTKF), is introduced, and shown to outperform other existing schemes in typical application scenarios. A probe-based distributed protocol for knowledge range adjustment (PRADA) is finally introduced that allows each node to efficiently select online its topology knowledge range. PRADA is shown to rapidly converge to a near-optimal solution.

Method and system for communicating with identification tags

Abstract: A method, identification tag reader and computer program product for communication with an identification tag are disclosed. To communicate with the tag, identification data may be retrieved from an identification tag. A guest identification, compliant with at least a portion of a standard network protocol address, may be assigned to the identification tag. A message addressed to a tag routing address of the tag may be received, and a response to the message may be sent.

Building automation system data management

Abstract: A building automation system (BAS) comprising a plurality of end devices, at least one communication network, and a protocol-independent server engine. The end devices are each associated with at least one of a space, a system, or a subsystem for at least a portion of a building or a campus. The communication network supports a plurality of communication protocols and communicatively couples at least a portion of the plurality of end devices. The server engine is communicatively coupled to the at least one communication network and includes means for selectively implementing a dynamic extensibility capability for the BAS that establishes communications with and control of the plurality of end devices over the plurality of communication protocols, and means for selectively implementing an automatic configuration capability for the BAS that supports addition of end devices to the plurality of end devices by determining at least one characteristic of each end device. Methods of establishing communications with unknown end devices in a building automation system (BAS) based upon metadata descriptors provided by known and unknown end devices are also disclosed.

Broadband multi-service, switching, transmission and distribution architecture for low-cost telecommunications networks

Abstract: A low-cost, distributed broadband multi-service communication network includes intelligent hybrid communication nodes (99) which communicate with one another. The hybrid communication nodes (99) have multi-media interfaces (41-47) and processors (2) that allow the node to receive a communication broadcast at one protocol interface (41-47), convert the broadcast to other communication protocols, and route it to those different communication protocol interfaces (41-47) for transmission to other communication media. The smart hybrid communication nodes (99) provide a distributed system that does not rely on a central intelligence, so that the network can be instantly deployed and expanded. In addition, a weatherproof container permits the nodes to be physically mounted adjacent to a communication antenna (54). This eliminates the need for a cable to connect a transmitter interface to the antenna, which can be several hundred feet away at the top of a tower. Even expensive cable results in substantial power and signal loss.

On the security of cluster-based communication protocols for wireless sensor networks

Abstract: Wireless sensor networks are ad hoc networks comprised mainly of small sensor nodes with limited resources, and are rapidly emerging as a technology for large-scale, low-cost, automated sensing and monitoring of different environments of interest. Cluster-based communication has been proposed for these networks for various reasons such as scalability and energy efficiency. In this paper, we investigate the problem of adding security to cluster-based communication protocols for homogeneous wireless sensor networks consisting of sensor nodes with severely limited resources, and propose a security solution for LEACH, a protocol where clusters are formed dynamically and periodically. Our solution uses building blocks from SPINS, a suite of highly optimized security building blocks that rely solely on symmetric-key methods; is lightweight and preserves the core of the original LEACH.

Robust TCP stream reassembly in the presence of adversaries

Abstract: There is a growing interest in designing high-speed network devices to perform packet processing at semantic levels above the network layer. Some examples are layer-7 switches, content inspection and transformation systems, and network intrusion detection/prevention systems. Such systems must maintain per-flow state in order to correctly perform their higher-level processing. A basic operation inherent to per-flow state management for a transport protocol such as TCP is the task of reassembling any out-of-sequence packets delivered by an underlying unreliable network protocol such as IP. This seemingly prosaic task of reassembling the byte stream becomes an order of magnitude more difficultto soundly execute when conducted in the presence of an adversary whose goal is to either subvert the higher-level analysis or impede the operation of legitimate traffic sharing the same network path. We present a design of a hardware-based high-speed TCP reassembly mechanism that is robust against attacks. It is intended to serve as a module used to construct a variety of network analysis systems, especially intrusion prevention systems. Using trace-driven analysis of out-of-sequence packets, we first characterize the dynamics of benign TCP trafficand show how we can leverage the results to design a reassembly mechanism that is efficient when dealing with non-attack traffic. We then refine the mechanism to keep the system effective in the presence of adversaries. We show that although the damage caused by an adversary cannot be completely eliminated, it is possible to mitigate the damage to a great extent by careful design and resource allocation. Finally, we quantify the trade-off between resource availability and damage from an adversary in terms of Zombie equations that specify, for a given configuration of our system, the number of compromised machines an attacker must have under their control in order to exceed a specified notion of "acceptablecollateral damage."

Selectively ordered protocol for unreliable channels

Abstract: A communication protocol provides a selective ordering of packets such that some sequences of packets on the channel are guaranteed not to be delivered out of order, while other packets on the same channel may be delivered before earlier sent packets are received, thereby preempting their delivery. The communication protocol can be implemented using UDP over IP. The protocol may be used for exchange of information in a distributed multi-player game.

VITP: an information transfer protocol for vehicular computing

Abstract: Recent advances in wireless inter-vehicle communication systems enable the development of Vehicular Ad-Hoc Networks (VANET) and create significant opportunities for the deployment of a wide variety of vehicular applications and services. In this paper, we introduce the Vehicular Information Transfer Protocol (VITP), an application-layer communication protocol, which is designed to support the establishment of a distributed, ad-hoc service infrastructure over VANET. The VITP infrastructure can be used to provide location-based, traffic-oriented services to drivers, using information retrieved from vehicular sensors and taking advantage of on-board GPS navigation systems. In this paper, we present the key design concepts of the protocol and the infrastructure, the protocol specification, simple examples of protocol interactions that support driver inquiries, and a simulation study of VITP performance properties.

Soft tamper-proofing via program integrity verification in wireless sensor networks

Abstract: Small low-cost sensor devices, each equipped with limited resources, are networked and used for various critical applications, especially those related to homeland security. Making such a sensor network secure is challenging mainly because it usually has to operate in a harsh, sometimes hostile, and unattended environment, where it is subject to capture, reverse-engineering, and manipulation. To address this challenge, we present a program-integrity verification (PIV) protocol that verifies the integrity of the program residing in each sensor device whenever the device joins the network or has experienced a long service blockage. The heart of PIV is the novel randomized hash function tailored to low-cost CPUs, by which the algorithm for hash computation on the program can be randomly generated whenever the program needs to be verified. By realizing this randomized hash function, the PlV protocol 1) prevents manipulation/reverse-engineering/reprogramming of sensors unless the attacker modifies the sensor hardware (e.g., attaching more memory), 2) provides purely software-based protection, and 3) triggers the verification infrequently, thus incurring minimal intrusiveness into normal sensor functions. Our performance evaluation shows that the PIV protocol is computationally efficient and incurs only a small communication overhead, hence making it ideal for use in low-cost sensor networks.