Abstract: The efficient use of resources and the lossless transfer of data bursts in future optical
networks requires the accurate knowledge of the available bandwidth for each network
link. Such information is important in monitoring congestions and can be used by
appropriate load balancing and congestion avoidance mechanisms. In this paper we
propose a mechanism for monitoring and subsequently managing bandwidth resources,
using the Simple NetworkManagement Protocol (SNMP). In the proposed mechanism,
link bandwidth availability is not a scalar parameter, but a function of time that records
the future utilization of the link. For every output port, each agent-node maintains a
simple data structure in the form of a table that records the utilization profile of that
outgoing link. With the addition of new objects in the Management Information Base
(MIB) of each agent-node and proper synchronization, SNMP can be used to update
and retrieve the reservations made on the links in order to obtain an instant picture of
the network traffic situation.
Abstract: The management of Grid resources requires scheduling of both computation and communication tasks at various levels. In this study, we consider the two constituent sub-problems of Grid scheduling, namely: (i) the scheduling of computation tasks to processing resources and (ii) the routing and scheduling of the data movement in a Grid network. Regarding computation tasks, we examine two typical online task scheduling algorithms that employ advance reservations and perform full network simulation experiments to measure their performance when implemented in a centralized or distributed manner. Similarly, for communication tasks, we compare two routing and data scheduling algorithms that are implemented in a centralized or a distributed manner. We examine the effect network propagation delay has on the performance of these algorithms. Our simulation results indicate that a distributed architecture with an exhaustive resource utilization update strategy yields better average end-to-end delay performance than a centralized architecture.
Abstract: Core networks of the future will have a
translucent and eventually transparent optical
structure. Ultra-high-speed end-to-end connectiv-
ity with high quality of service and high reliability
will be realized through the exploitation of opti-
mized protocols and lightpath routing algorithms.
These algorithms will complement a flexible con-
trol and management plane integrated in the
proposed solution. Physical layer impairments
and optical performance are monitored and
incorporated in impairment-aware lightpath rout-
ing algorithms. These algorithms will be integrat-
ed into a novel dynamic network planning tool
that will consider dynamic traffic characteristics,
a reconfigurable optical layer, and varying physi-
cal impairment and component characteristics.
The network planning tool along with extended
control planes will make it possible to realize the
vision of optical transparency. This article pre-
sents a novel framework that addresses dynamic
cross-layer network planning and optimization
while considering the development of a future
transport network infrastructure.
Abstract: The efficient use of resources and the lossless transfer of data bursts in future optical
networks requires the accurate knowledge of the available bandwidth for each network
link. Such information is important in monitoring congestions and can be used by
appropriate load balancing and congestion avoidance mechanisms. In this paper we
propose a mechanism for monitoring and subsequently managing bandwidth resources,
using the Simple NetworkManagement Protocol (SNMP). In the proposed mechanism,
link bandwidth availability is not a scalar parameter, but a function of time that records
the future utilization of the link. For every output port, each agent-node maintains a
simple data structure in the form of a table that records the utilization profile of that
outgoing link. With the addition of new objects in the Management Information Base
(MIB) of each agent-node and proper synchronization, SNMP can be used to update
and retrieve the reservations made on the links in order to obtain an instant picture of
the network traffic situation.
Abstract: In this work we present the basic concepts in the architecture of a peer-to-peer environment for monitoring multiple wireless sensor networks, called ShareSense. ShareSense, which is currently under development, uses JXTA as a peer-to-peer substrate. We demonstrate its basic functionalities using a simple application scenario, which utilizes multiple disparate wireless sensor networks. This application scenario involves monitoring of such networks using a separate management environment and a custom application GUI, as well as using Google Earth as an additional user interface.
Abstract: We propose a MAC protocol for mobile ad hoc networks that
uses power control for the RTS/CTS and DATA frame
transmissions in order to improve energy and capacity
utilization efficiency. Unlike IEEE 802.11, in our scheme the
RTS frames are not sent using the maximum transmission
power to silence neighbouring nodes, and the CTS frames do
not silence all receiving nodes to the same degree. In contrast,
the transmission power of the RTS frames follows a slow
start principle, while the CTS frames, which are sent at
maximum transmission power, prevent the neighbouring
nodes from transmitting their DATA frames with power more
than a computed threshold, while allowing them to transmit at
power levels less than that threshold. This is done by
including in the RTS and the CTS frames additional
information, such as the power of the transmissions, and the
interference tolerance of the nodes. Moreover the DATA
frames are sent at the minimum required transmission power
increased by a small margin to ensure connectivity with the
intended receiver, so as to cause minimal interference to
neighbouring nodes and allow for future interference to be
added to the receiver of the DATA frames. The power to be
used by the transmitter is computed by the recipient of the
RTS frame and is included in the CTS frame. It is expected
that a network with such a power management scheme would
achieve a better throughput performance and more power
savings than a network without such a scheme.
Abstract: We propose a MAC protocol for mobile ad hoc networks that
uses power control for the RTS/CTS and DATA frame
transmissions in order to improve energy and capacity
utilization efficiency. Unlike IEEE 802.11, in our scheme the
RTS frames are not sent using the maximum transmission
power to silence neighbouring nodes, and the CTS frames do
not silence all receiving nodes to the same degree. In contrast,
the transmission power of the RTS frames follows a slow
start principle, while the CTS frames, which are sent at
maximum transmission power, prevent the neighbouring
nodes from transmitting their DATA frames with power more
than a computed threshold, while allowing them to transmit at
power levels less than that threshold. This is done by
including in the RTS and the CTS frames additional
information, such as the power of the transmissions, and the
interference tolerance of the nodes. Moreover the DATA
frames are sent at the minimum required transmission power
increased by a small margin to ensure connectivity with the
intended receiver, so as to cause minimal interference to
neighbouring nodes and allow for future interference to be
added to the receiver of the DATA frames. The power to be
used by the transmitter is computed by the recipient of the
RTS frame and is included in the CTS frame. It is expected
that a network with such a power management scheme would
achieve a better throughput performance and more power
savings than a network without such a scheme.
Abstract: In this work, we present a concrete framework, based on web services-oriented architecture, for integrating small programmable objects in the web of things.
Functionality and data gathered by the Small Programmable Objects (SPO) are exposed using Web Services. Based on this, by exploiting XML encoding, SPO can be comprehensible by any web application. The architecture proposed is focused in providing secure and efficient interoperability between SPO and the web.
Additionally, the proposed architecture provides management capabilities for deploying, maintaining and operating SPO applications across multiple networks.
We present the multilayer architecture of our system and its implementation, which uses a combination of Java Standard and Micro Editions. Finally, we present a case study presenting our implementation. In this application we use SunSPOTs, which are wireless network motes developed by Sun Microsystems.
Abstract: Avertical perspective, ranging from management
and routing to physical layer options, concerning dynamic
network monitoring and compensation of impairments
(M&C),is given.Feasibility, reliability,and performance
improvements on reconfigurable transparent networksare
expected to arise from the consolidated assessment of networkmanagement and control specifications, as a more accurate evaluation of available M&C techniques. In the network
layer,physical parameters aware algorithms are foreseen to
pursue reliable network performance. In the physical layer,
some new M&C methods were developed and rating of the state-of-the-art reported in literature is given. Optical monitoring implementation and viability is discussed.
Abstract: We present the conceptual basis and the initial planning for an open source management architecture for wireless sensor networks (WSN). Although there is an abundance of open source tools serving the administrative needs of WSN deployments, there is a lack of tools or platforms for high level integrated WSN management. This is because of a variety of factors, including the lack of open source management tools, the immaturity of tools that offer manageability for WSNs, the limited high level management capabilities of sensor devices and architectures, and the lack of standardization. The current work is, to our knowledge, the first effort to conceptualize, formalize and design a remote, integrated management platform for the support of WSN research laboratories. The platform is based on the integration and extension of two innovative platforms: jWebDust, a WSN operation and management platform, and OpenRSM, an open source integrated remote systems and networkmanagement platform. The proposed system architecture can support several levels of integration (infrastructure management, functionality integration, firmware management), corresponding to different use-cases and application settings.
Abstract: The Greek School Network (GSN) has developed and put into production a number of e-learning services, including synchronous and asynchronous tele-education, electronic class management, blogs, video-on-demand, podcasts and multimedia libraries. These new services complement established and accepted e-learning services, such as teleconferencing, user wikis, forums, email, electronic publishing, and e-magazines. This report presents the most prominent digital e-learning services offered by GSN, with emphasis on the asynchronous tele-education service, which is presented in detail. Its implementation platform, the Moodle course management system, is compared against well-known asynchronous open source tele-education platforms such as COSE, Claroline, Fle3, ILIAS, Manhattan, KEWL, Comentor, e-Class and Eledge. The evaluation of the asynchronous tele-education platforms is based on detailed comparisons of their characteristics and of the methodology they adopt in order to deliver educational services. The comparison is based on evaluation criteria derived from the documented experiences of research institutes and educational bodies and also from the experience of GSN itself. The paper concludes with the presentation of an extension to Moodle for implementing communities of practice (CoPs) that facilitate the creation and delivery of electronic educational open content for teachers in a synergetic manner.
Abstract: In this paper, we present BAD, an application-level multi-
cast infrastructure. BAD is designed to improve the perfor-
mance of multicast dissemination trees, under both a static
and a dynamic environment, where the e ective bandwidth
of the network links changes with time. Its main goal is
to improve the data rate that end users perceive during
a multicast operation. BAD can be used for the creation
and management of multicast groups. It can be deployed
over any DHT retaining its fundamental advantages of band-
width improvement. BAD consists of a suit of algorithms
for node joins/leaves, bandwidth distribution to heteroge-
neous nodes, tree rearrangement and reduction of overhead.
We have implemented BAD within the FreePastry system.
We report on the results of a detailed performance evalua-
tion which testi es for BAD's eciency and low overhead.
Speci cally, our experiments show that the improvement on
the minimum bandwidth ranges from 40% to 1400% and the
improvement on the average bandwidth ranges from 60% to
250%.
Abstract: This chapter aims at presenting certain important aspects of the design of lightweight, event-driven algorithmic solutions for data dissemination in wireless sensor networks that provide support for reliable, efficient and concurrency-intensive operation. We wish to emphasize that efficient solutions at several levels are needed, e.g.~higher level energy efficient routing protools and lower level power management schemes. Furthermore, it is important to combine such different level methods into integrated protocols and approaches. Such solutions must be simple, distributed and local. Two useful algorithmic design principles are randomization (to trade-off efficiency and fault-tolerance) and adaptation (to adjust to high network dynamics towards improved operation). In particular, we provide a) a brief description of the technical specifications of state-of-the-art sensor devices b) a discussion of possible models used to abstract such networks, emphasizing heterogeneity, c) some representative power management schemes, and d) a presentation of some characteristic protocols for data propagation. Crucial efficiency properties of these schemes and protocols (and their combinations, in some cases) are investigated by both rigorous analysis and performance evaluations through large scale simulations.
Abstract: Wireless sensor networks are a recently introduced category of ad hoc computer networks, which are comprised by nodes of small size and limited computing and energy resources. Such nodes are able of measuring physical properties such as temperature, humidity, etc., wireless communication between each other and in some cases interaction with their surrounding environments (through the use of electromechanical parts).
As these networks have begun to be widely available (in terms of cost and commercial hardware availability), their field of application and philosophy of use is constantly evolving. We have numerous examples of their applications, ranging from monitoring the biodiversity of a specific outdoor area to structural health monitoring of bridges, and also networks ranging from few tens of nodes to even thousands of nodes.
In this PhD thesis we investigated the following basic research lines related to wireless sensor networks:
a) their simulation,
b) the development of data propagation protocols suited to such networks and their evaluation through simulation,
c) the modelling of ``hostile'' circumstances (obstacles) during their operation and evaluation of their impact through simulation,
d) the development of a sensor networkmanagement application.
Regarding simulation, we initially placed an emphasis to issues such as the effective simulation of networks of several thousands of nodes, and in that respect we developed a network simulator (simDust), which is extendable through the addition of new data propagation protocols and visualization capabilities. This simulator was used to evaluate the performance of a number of characteristic data propagation protocols for wireless sensor networks. Furthermore, we developed a new protocol (VRTP) and evaluated its performance against other similar protocols. Our studies show that the new protocol, that uses dynamic changes of the transmission range of the network nodes, performs better in certain cases than other related protocols, especially in networks containing obstacles and in the case of non-homogeneous placement of nodes.
Moreover, we emphasized on the addition of ``realistic'' conditions to the simulation of such protocols, that have an adversarial effect on their operation. Our goal was to introduce a model for obstacles that adds little computational overhead to a simulator, and also study the effect of the inclusion of such a model on data propagation protocols that use geographic information (absolute or relative). Such protocols are relatively sensitive to dynamic topology changes and network conditions. Through our experiments, we show that the inclusion of obstacles during simulation can have a significant effect on these protocols.
Finally, regarding applications, we initially proposed an architecture (WebDust/ShareSense), for the management of such networks, that would provide basic capabilities of managing such networks and developing applications above it. Features that set it apart are the capability of managing multiple heterogeneous sensor networks, openess, the use of a peer-to-peer architecture for the interconnection of multiple sensor network. A large part of the proposed architecture was implemented, while the overall architecture was extended to also include additional visualization capabilities.
Abstract: In large-scale or evolving networks, such as the Internet,
there is no authority possible to enforce a centralized traffic management.
In such situations, Game Theory and the concepts of Nash equilibria
and Congestion Games [8] are a suitable framework for analyzing
the equilibrium effects of selfish routes selection to network delays.
We focus here on layered networks where selfish users select paths to
route their loads (represented by arbitrary integer weights). We assume
that individual link delays are equal to the total load of the link. We
focus on the algorithm suggested in [2], i.e. a potential-based method
for finding pure Nash equilibria (PNE) in such networks. A superficial
analysis of this algorithm gives an upper bound on its time which is
polynomial in n (the number of users) and the sum of their weights. This
bound can be exponential in n when some weights are superpolynomial.
We provide strong experimental evidence that this algorithm actually
converges to a PNE in strong polynomial time in n (independent of the
weights values). In addition we propose an initial allocation of users
to paths that dramatically accelerates this algorithm, compared to an
arbitrary initial allocation. A by-product of our research is the discovery
of a weighted potential function when link delays are exponential to their
loads. This asserts the existence of PNE for these delay functions and
extends the result of
Abstract: ManyWSN algorithms and applications are based on knowledge
regarding the position of nodes inside the network area.
However, the solution of using GPS based modules in order
to perform localization in WSNs is a rather expensive solution
and in the case of indoor applications, such as smart
buildings, is also not applicable. Therefore, several techniques
have been studied in order to perform relative localization
in WSNs; that is, to compute the position of
a node inside the network area relatively to the position
of other nodes. Many such techniques are based on indicators
like the Radio Signal Strength Indicator (RSSI)
and the Link Quality Indicator (LQI). These techniques are
based on the assumption that there is strong correlation between
the Euclidian distance of the communicating motes
and these indicators. Therefore, high values of RSSI and
LQI should indicate physical proximity of two communicating
nodes. However, these indicators do not depend solely on
distance. Physical obstacles, ambient electromagnetic noise
and interferences from other wireless transmissions also affect
the quality of wireless communication in a stochastic
way. In this paper we propose, implement, experimentally
fine tune and evaluate a localization algorithm that exploits
the stochastic nature of interferences during wireless communications
in order to perform localization in WSNs. Our
algorithm is particularly designed for in-door localisation of
moving people in smart buildings. The localisation achieved
is fine-grained, i.e. the position of the target mote is successfully
computed with approximately one meter accuracy.
This fine-grained localisation can be used by smart Building
Management Systems in many applications such as room
adaptation to presence. In our scenario, our proposed algorithm is used by a smart room in order to localise the
position of people inside the room and adapt room illumination
accordingly.
Abstract: Building efficient internet-scale data management services is the main focus of this chapter. In particular, we aim to show how to leverage DHT technology and extend it with novel algorithms and architectures in order to (i) improve efficiency and reliability for traditional DHT (exact-match) queries, particularly exploiting the abundance of altruism witnessed in real-life P2P networks, (ii) speedup range queries for data stored on DHTs, and (iii) support efficiently and scalably the publish/subscribe paradigm over DHTs, which crucially depends on algorithms for supporting rich queries on string-attribute data.
Abstract: The problem of robust line planning requests for a set of
origin-destination paths (lines) along with their frequencies in an underlying
railway network infrastructure, which are robust to
uctuations of
real-time parameters of the solution.
In this work, we investigate a variant of robust line planning stemming
from recent regulations in the railway sector that introduce competition
and free railway markets, and set up a new application scenario: there is
a (potentially large) number of line operators that have their lines xed
and operate as competing entities struggling to exploit the underlying
network infrastructure via frequency requests, while the management of
the infrastructure itself remains the responsibility of a single (typically
governmental) entity, the network operator.
The line operators are typically unwilling to reveal their true incentives.
Nevertheless, the network operator would like to ensure a fair (or, socially
optimal) usage of the infrastructure, e.g., by maximizing the (unknown to
him) aggregate incentives of the line operators. We show that this can be
accomplished in certain situations via a (possibly anonymous) incentivecompatible
pricing scheme for the usage of the shared resources, that is
robust against the unknown incentives and the changes in the demands
of the entities. This brings up a new notion of robustness, which we
call incentive-compatible robustness, that considers as robustness of the
system its tolerance to the entities' unknown incentives and elasticity
of demands, aiming at an eventual stabilization to an equilibrium point
that is as close as possible to the social optimum.
Abstract: Wireless sensor networks can be very useful in applications that require the detection of crucial events, in physical environments subjected to critical conditions, and the propagation of data reporting their realization to a control center. In this paper we propose jWebDust, a generic and modular application environment for developing and managing applications that are based on wireless sensor networks. Our software architecture provides a range of services that allow to create customized applications with minimum implementation effort that are easy to administrate. We move beyond the ?networking-centric? view of sensor network research and focus on how the end user (administrator, control center supervisor, etc.) will visualize and interact with the system.
We here present its open architecture, the most important design decisions, and discuss its distinct features and functionalities. jWebDust allows heterogeneous components to interoperate (real world sensor networks will rarely be homogeneous) and allows the integrated management and control of multiple such networks by also defining web-based mechanisms to visualize the network state, the results of queries, and a means to inject queries in the network. The architecture also illustrates how existing protocols for various services can interoperate in a bigger framework - such as the tree construction, query routing, etc.
Abstract: We address the call control problem in wireless cellular networks that utilize Frequency Division Multiplexing (FDM) technology. In such networks, many users within the same geographical region (cell) can communicate simultaneously with other users of the network using distinct frequencies. The available frequency spectrum is limited; hence, its management should be done efficiently. The objective of the call control problem is, given a spectrum of available frequencies and users that wish to communicate in a cellular network, to maximize the number of users that communicate without signal interference. We study the online version of the problem in cellular networks using competitive analysis and present new upper and lower bounds.
Abstract: The concept of trust plays an important role in the operation and public acceptance of today's computing environment. Although it is a difficult concept to formalize and handle, many efforts have been made towards a clear definition of trust and the development of systematic ways for trust management. Our central viewpoint is that trust cannot be defined, anymore, as consisting of a static set of rules that define systems properties that hold eternally due to the highly dynamic nature of today's computing systems (e.g. wireless networks, ad-hoc networks, virtual communities and digital territories etc.). Our approach is an effort to define trust in terms of properties that hold with some limiting probability as the the system grows and try to establish conditions that ensure that ??good?? properties hold almost certainly. Based on this viewpoint, in this paper we provide a new framework for defining trust through formally definable properties that hold, almost certainly, in the limit in randomly growing combinatorial structures that model ??boundless?? computing systems (e.g. ad-hoc networks), drawing on results that establish the threshold behavior of predicates written in the first and second order logic. We will also see that, interestingly, some trust models have properties that do not have limiting probabilities. This fact can be used to demonstrate that as certain trust networks grow indefinitely, their trust properties are not certain to be present
Abstract: Managing corporate Information Technology (IT) environment becomes increasingly complex as server logic architecture becomes distributed and the number of manageable entities increases. At the same time, the open source community has not yet produced a reliable systems and networkmanagement solution, even though there are open source initiatives specializing in individual fields of remote management. This paper presents OpenRSM, an integrated remote management system created by integrating individual open source initiatives and augmenting them to support additional functionality so that a lightweight integrated systems and networkmanagement solution is produced.
Abstract: This paper studies the data gathering problem in wireless networks, where data generated at the nodes has to be collected at a single sink. We investigate the relationship between routing optimality and fair resource management. In particular, we prove that for energy balanced data propagation, Pareto optimal routing and flow maximization are equivalent, and also prove that flow maximization is equivalent to maximizing the network lifetime. We algebraically characterize the network structures in which energy balanced data flows are maximal. Moreover, we algebraically characterize communication links which are not used by an optimal flow. This leads to the characterization of minimal network structures supporting the maximal flows.
We note that energy balance, although implying global optimality, is a local property that can be computed efficiently and in a distributed manner. We suggest online distributed algorithms for energy balance in different optimal network structures and numerically show their stability in particular setting. We remark that although the results obtained in this paper have a direct consequence in energy saving for wireless networks they do not limit themselves to this type of networks neither to energy as a resource. As a matter of fact, the results are much more general and can be used for any type of network and different type of resources.
Abstract: This paper studies the data gathering problem in wireless networks, where data generated at the nodes has to be collected at a single sink. We investigate the relationship between routing optimality and fair resource management. In particular, we prove that for energy-balanced data propagation, Pareto optimal routing and flow maximization are equivalent, and also prove that flow maximization is equivalent to maximizing the network lifetime. We algebraically characterize the network structures in which energy-balanced data flows are maximal. Moreover, we algebraically characterize communication links which are not used by an optimal flow. This leads to the characterization of minimal network structures supporting the maximal flows.
We note that energy-balance, although implying global optimality, is a local property that can be computed efficiently and in a distributed manner. We suggest online distributed algorithms for energy-balance in different optimal network structures and numerically show their stability in particular setting. We remark that although the results obtained in this paper have a direct consequence in energy saving for wireless networks they do not limit themselves to this type of networks neither to energy as a resource. As a matter of fact, the results are much more general and can be used for any type of network and different types of resources.
Abstract: The problem of robust line planning requests for a set of
origin-destination paths (lines) along with their tra±c rates (frequencies)
in an underlying railway network infrastructure, which are robust to
°uctuations of real-time parameters of the solution.
In this work, we investigate a variant of robust line planning stemming
from recent regulations in the railway sector that introduce competition
and free railway markets, and set up a new application scenario: there is
a (potentially large) number of line operators that have their lines ¯xed
and operate as competing entities struggling to exploit the underlying
network infrastructure via frequency requests, while the management of
the infrastructure itself remains the responsibility of a single (typically
governmental) entity, the network operator.
The line operators are typically unwilling to reveal their true incentives.
Nevertheless, the network operator would like to ensure a fair (or, socially
optimal) usage of the infrastructure, e.g., by maximizing the (unknown to
him) aggregate incentives of the line operators. We show that this can be
accomplished in certain situations via a (possibly anonymous) incentive-
compatible pricing scheme for the usage of the shared resources, that is
robust against the unknown incentives and the changes in the demands
of the entities. This brings up a new notion of robustness, which we
call incentive-compatible robustness, that considers as robustness of the
system its tolerance to the entities' unknown incentives and elasticity
of demands, aiming at an eventual stabilization to an equilibrium point
that is as close as possible to the social optimum.
Abstract: We present SeAl1, a novel data/resource and data-access management infrastructure designed for the purpose of addressing a key problem in P2P data sharing networks, namely the problem of wide-scale selfish peer behavior. Selfish behavior has been manifested and well documented and it is widely accepted that unless this is dealt with, the scalability, efficiency, and the usefulness of P2P sharing networks will be diminished. SeAl essentially consists of a monitoring/accounting subsystem, an auditing/verification subsystem, and incentive mechanisms. The monitoring subsystem facilitates the classification of peers into selfish/altruistic. The auditing/verification layer provides a shield against perjurer/slandering and colluding peers that may try to cheat the monitoring subsystem. The incentives mechanisms efectively utilize these layers so to increase the computational/networking and data resources that are available to the community. Our extensive performance results show that SeAl performs its tasks swiftly, while the overhead introduced by our accounting and auditing mechanisms in terms of response time, network, and storage overheads are very small.
Abstract: We present SeAl, a novel data/resource and data-access management infrastructure designed for the purpose of addressing a key problem in P2P data sharing networks, namely the problem of wide-scale selfish peer behavior. Selfish behavior has been manifested and well documented and it is widely accepted that unless this is dealt with, the scalability, efficiency, and the usefulness of P2P sharing networks will be diminished. SeAl essentially consists of a monitoring/accounting subsystem, an auditing/verification subsystem, and incentive mechanisms. The monitoring subsystem facilitates the classification of peers into selfish/altruistic. The auditing/verification layer provides a shield against perjurer/slandering and colluding peers that may try to cheat the monitoring subsystem. The incentives mechanisms effectively utilize these layers so to increase the computational/networking and data resources that are available to the community. Our extensive performance results show that SeAl performs its tasks swiftly, while the overhead introduced by our accounting and auditing mechanisms in terms of response time, network, and storage overheads are very small.
Abstract: The Greek School Network (GSN) is a closed educational network that offers advanced
telematic and networking services to all primary/secondary education schools and
educational administration offices in Greece. The primary objective of GSN is to provide a network infrastructure for the interconnection of school PC laboratories so that modern educational methods and pedagogical models can be used in the school community securely and effectively. GSN has scaled in size, reached maturity, and is currently delivering a wide range of network and telematic services to students and educators. Being the second largest
communications network nationwide, GSN is exposed to all kinds of security threats and, due to its educational hypostasis, naive user behaviour. The current paper presents an evaluation of security management solutions for the enforcement of policies, practices, and user protection methodologies proven viable within the GSN environment, as indicated by statistics and metrics on the use of the related services. The paper reaches the conclusion that GSN security services constitute a sound framework that can successfully cover the needs of
the school community.
Abstract: In this paper we present the design of jWebDust, a generic and modular application environment for developing and managing applications based on wireless sensor networks that are accessible via the internet. Our software architecture provides a range of services that allow to create customized web-based applications with minimum implementation effort that are easy to administrate. We here present its open architecture, the most important design decisions, and discuss its distinct features and functionalities. jWebDust allows heterogeneous components to interoperate and the integrated management and control of multiple such networks by defining web-based mechanisms to visualize the network state, the results of queries, and a means to inject queries in the network.
Abstract: In this work we present the design of jWebDust, a
software environment for monitoring and controlling sensor networks via a web interface. Our software architecture provides a range of services that allow to create customized applications with minimum implementation effort that are easy to administrate. We present its open architecture, the most important design decisions, and discuss its distinct features and functionalities. jWebDust will allow heterogeneous components to operate in the same sensor network, and the integrated management and control of multiple such networks by defining web-based mechanisms to visualize the network state, the results of queries, and a means to inject queries in the network.
Abstract: We present the conceptual basis and the initial planning for an open
source management architecture for wireless sensor networks (WSN). Although
there is an abundance of open source tools serving the administrative needs of
WSN deployments, there is a lack of tools or platforms for high level integrated
WSN management. The current work is, to our knowledge, the first effort to
conceptualize and design a remote, integrated management platform for the
support of WSN research laboratories. The platform is based on the integration
and extension of two innovative platforms: jWebDust, a WSN operation and
management platform, and OpenRSM, an open source integrated remote
systems and networkmanagement platform. The proposed system architecture
can support several levels of integration in order to cover to multiple,
qualitatively differentiated use-cases.
Abstract: In this paper we study the threshold behavior of the fixed radius random graph model and its applications to the key management problem of sensor networks and, generally, for mobile ad-hoc networks. We show that this random graph model can realistically model the placement of nodes within a certain region and their interaction/sensing capabilities (i.e. transmission range, light sensing sensitivity etc.). We also show that this model can be used to define key sets for the network nodes that satisfy a number of good properties, allowing to set up secure communication with each other depending on randomly created sets of keys related to their current location. Our work hopes to inaugurate a study of key management schemes whose properties are related to properties of an appropriate random graph model and, thus, use the rich theory developed in the random graph literature in order to transfer ?good? properties of the graph model to the key sets of the nodes.
Partially supported by the IST Programme of the European Union under contact number IST-2005-15964 (AEOLUS) and the INTAS Programme under contract with Ref. No 04-77-7173 (Data Flow Systems: Algorithms and Complexity (DFS-AC)).
Abstract: Peer-to-peer sharing systems are becoming
increasingly popular and an exciting new class of
innovative, internet-based data management
systems. In these systems, users contribute their
own resources (processing units and storage
devices) and content (i.e., documents) to the P2P
community. We focus on the management of
content and resources in such systems. Our goal
is to harness all available resources in the P2P
network so that the users can access all available
content efficiently. Efficiency is taken both from
(i) the point of view of the system, in that we
strive to ensure fair load distribution among all
peer nodes, and (ii) from the point of view of the
users, in that we strive to ensure low user-request
response times.
We propose a novel architecture for this new
class of applications, which differs drastically
from what is either found currently in existing
products or proposed in academia. We contribute
and study novel solutions that achieve our goals,
while at the same time addressing the formidable
challenges due to the autonomy of peers, their
heterogeneous processing and storage capacities,
their different content contributions, the huge
system scale, and the highly dynamic system
environment.
