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The coverage problem is one of the most fundamental issues in a wireless sensor network, which directly affects the capability and efficiency of the sensor network. In this paper, we formulate this problem as a construction problem to find a topology that covers the required sensing area with high reliability. Deploying a good topology is also beneficial to management and energy saving. We propose an optimal coverage scheme for wireless sensor networks that can maintain sufficient sensing area as well as provide high reliability and long system lifetime, which is the main design challenge in sensor networks. With the same number of sensors, our scheme compares favorably with the existing schemes. Keywords: sensors, coverage, hexagon, reliability, energy. [ABSTRACT FROM AUTHOR]

The Radio Link Control (RLC) protocol of Universal Mobile Telecommunication System (UMTS) provides link layer reliability that could mitigate the effects of the hostile radio propagation channel on packet data transmission. In this paper, the impact of some of the RLC reliability mechanisms on the performance of File Transport Protocol (FTP) is investigated. The investigations are carried out using a real time emulation platform, which makes the results from this study more realistic than simulation or simplified analytical studies as the overall End-2-End performance is analyzed involving real world protocol implementations. [ABSTRACT FROM AUTHOR]

In a variety of applications, wireless sensor networks have received more attention in recent years. Sensor nodes, however, have many limitations including limited battery power and communication range. In this network, data gathering and data fusion help to reduce energy consumption and redundant data. LEACH (Low Energy Adoptive Clustering Hierarchy) is the most representative protocol using data gathering and data fusion, but it has several problems including inefficient energy consumption by many cluster headers to the distant sink and a single-hop routing path. In this paper, we propose two routing protocols called Routing Protocol based on Super-Cluster Header (RPS) and Multi-hop Routing Protocol based on Super-Cluster Header (MRPS) in order to resolve the problems of LEACH. The key idea of our protocols is that only one node sends the combined data to the sink and every node uses multi-hop routing in order to gather data in the cluster. We evaluate performance of our protocols through simulations. Simulation results show that our protocols offer a much better performance than the legacy protocols in terms of energy cost, the network lifetime, and fairness of the energy consumption. [ABSTRACT FROM AUTHOR]

In recent years, a variety of overlay networks are created over the Internet via virtual links. We investigate the impact of the virtual link configuration on the network capacity with a dual-layer lattice network model, focusing on the critical value of the input rate of user traffics. A mean-field theory suggests that the critical traffic is, approximately, inversely proportional to the average trip of virtual hops on the infrastructure. Simulations verify the analytic result and further show that the behavior of the overlay-physical network interactions is significantly divergent with different link configurations. Therefore, the optimization of virtual links will be conducive to improving the effectiveness of overlays. [ABSTRACT FROM AUTHOR]

This paper introduces a dynamic bandwidth allocation algorithm in a video streaming multicast system. The approach is to introduce the vibration of received video quality into the QoS metric and make the receivers more negative in subscribing higher layers when bandwidth increases. A simulated annealing algorithm is applied in the server side to find the optimal allocation schema within the concurrent network situation at run time. Simulated experiments on NS-2 have been carried out to validate the algorithm. The result shows an improvement of 6.8 percents increase in received data rate and 6.0 percents decrease in data loss rate. [ABSTRACT FROM AUTHOR]

In spite of the Internet design principle of putting the complexity on the end-to-end entities, this work contributes to demonstrate what benefits can be expected by adding some processing capabilities to the network nodes for the class of interactive audio streaming applications. In particular, we deal with the bursty-error-prone nature of the Internet by proposing and evaluating a new multiflow block interleaver algorithm. After the conducted simulations, we show that our algorithm can efficiently mitigate the negative impact of long bursts. And what it is more, it is achieved by fulfilling the end-to-end audio time constraint requirements. [ABSTRACT FROM AUTHOR]

cdma2000 EV-DO service was deployed in Korea in 2004. Even though it provides a bandwidth up to almost 2 Mbps, channel quality is time-varying so that service quality should be controlled adaptively. This paper discusses the measurement and analysis of the EV-DO channel quality. Based on the analysis, it proposes a proxy node that is located in the base station, informs the corresponding node of current channel quality. And information from the lower layer is also useful because it can be used to adapt the channel state more quickly and accurately . The proposed feedback control can be used well with scalable video coding. [ABSTRACT FROM AUTHOR]

In this contribution, we investigate the performance of the output buffer of a video streaming server. We assume that the server encodes the video stream in a scalable way. When the output buffer gets congested, one may choose to drop the transmission of some of the layers in the packets, thus reducing the packet transmission time and expediting the restoration of the buffer size to normal levels. A discrete-time finite capacity queueing model with buffer size dependent transmission times is constructed and analysed using a probability generating functions approach. We conclude with some numerical examples. [ABSTRACT FROM AUTHOR]

In this paper we revisit strategies for joint radio link buffer management and scheduling for wireless video streaming. Based on previous work [1], we search for an optimal combination of scheduler and drop strategy for different end-to-end streaming options. We will show that a performance gain vs. the two best drop strategies in [1], ie drop the HOL packet or drop the lowest priority packet starting from HOL, is possible: Provided that basic side-information on the video stream structure is available, a more sophisticated strategy removes packets from an HOL group of packets such that the temporal dependencies usually present in video streams are not violated. This advanced buffer management scheme yields significant improvements for almost all investigated scheduling algorithms and streaming options. In addition, we will demonstrate the importance of fairness among users when selecting a suitable scheduler. [ABSTRACT FROM AUTHOR]

Streaming of multimedia content, i. e. the transmission of audio and video data in real-time gains more and more importance due to the increasing availability of digital audio/video devices. In a typical home environment several networks can be used for that purpose. This paper gives an overview of the available technologies pointing out the features of IEEE 1394 and IP based networks. Furthermore it covers principal concepts for coupling of several streaming networks. [ABSTRACT FROM AUTHOR]

Input Queued switches have been very well studied in the recent past. The Maximum Weight Matching (MWM) algorithm is known to deliver 100% throughput under any admissible traffic. However, MWM is not practical for its high computational complexity O(N 3). In this paper, we study a class of approximations to MWM from the point of view of local search. Firstly, we propose a greedy scheduling algorithm called GSA. It has the following features: (a) It is very simple to compute the weight of a neighbor matching. GSA only needs to compute the weight of two swapped edges instead of the weight of all the edges. (b) The computational complexity of GSA is O(c_max), where c_max denotes the maximum number of iterations. Hence we can adjust the value of c_max to achieve low computational complexity. Secondly, we observe that: (a) Local search is well suitable for parallel computing. (b) Each line card of high performance router has at least one processor. Based on the two important observations, we develop the second algorithm PGSA. Compared with GSA, PGSA significantly reduce the number of iterations. Simulation results show that PGSA with three iterations outperforms algorithms in [1] under different switch sizes. [ABSTRACT FROM AUTHOR]

In this paper a high performance and simple scheduling algorithm for combined input-crosspoint crossbar switches, called exhaustive round-robin (ERR), is presented and analyzed. We propose using of this scheduling system for arbitration at inputs and crosspoints. If the virtual output queue (crosspoint buffer) becomes empty, the input (crosspoint) arbiter updates its pointer to the next location in a fixed order. Otherwise, the pointer remains at the current virtual output queue (crosspoint buffer). It is shown that this new solution achieves 100% throughput for several admissible traffic patterns, including uniform and unbalanced traffic, using only one-cell crosspoint buffers. ERR-ERR ensures service to the queues with high load using the exhaustive service and to the queues with low load using RR selection. Also, the performance of proposed CICQ under unbalanced traffic pattern increases and converges to output buffered switch performance as the crosspoint buffer increases. This scheduling algorithm is based only on the information about cell existing in virtual output queue (crosspoint buffer). Therefore, it requires much less hardware than the proposed algorithms. These results show the advantage of the ERR-ERR CICQ switch as a competitor for the next generation of high-performance packet switches. [ABSTRACT FROM AUTHOR]

Recent developments in computer and communication networks require scheduling decisions to be made under increasingly complex system dynamics. We model and analyze the problem of packet transmissions through an arbitrary network of buffered queues, and provide a framework for describing routing and migration. This paper introduces an intuitive geometric description of stability for these networks and describes some simple algorithms which lead to maximal throughput. We show how coordination over sequential timeslots by algorithms such as those based on a round robin can provide considerable advantages over a randomized scheme. [ABSTRACT FROM AUTHOR]

In this paper, we present new layouts for the multi-stage interconnection networks such as shuffle, baseline and banyan networks that are suitable for photonic switching. In these new layouts, we decrease the number of crossovers of the stage links and crossovers between inlet-outlet of stages, which are known as the main bottleneck for the increase in switch capacity when it is realized for integrated photonic switching fabric. [ABSTRACT FROM AUTHOR]

Shared-memory based packet switches are increasingly being used for high-performance Internet switches and routers. The shared-memory switches are known to provide better throughput and packet-loss performance for bursty data traffic in high-speed networks and Internets compared with other buffering strategies under conditions of identical memory resource deployed in the shared-memory switch. The scheme to share the common memory resource among various broadband lines has direct impact on the throughput and packet-loss performance of the switch. In this paper, we compare the effect of unbalanced bursty traffic on commonly used memory-sharing schemes, namely the individual-static threshold based, global-static threshold based, dynamic threshold based and SMDA based memory-sharing schemes. Index terms—Shared Memory, Packet Switch, Unbalanced bursty Traffic, Memory-Sharing Schemes. [ABSTRACT FROM AUTHOR]

More and more attention is focused on direct interconnection networks when designing the switching fabrics in the terabit routers. Various switching mechanisms are proposed for multi-computer systems, which also rely on direct interconnection networks between processors to support the messages passing mechanism. But it remains unknown which one is more suitable for fabrics in the terabit routers. Based on the requirements of terabit class routers we made analysis and simulations on various switching mechanisms, such as store and forward, wormhole switching, virtual cut through switching and pipelined circuit switching. The results show that virtual cut through exhibits superior performance characteristics over other switching mechanisms under various conditions. Simulations of the performances of virtual cut through shows that larger buffer, longer flit and more virtual channels help to sustain higher throughput at the cost of increasing latency. [ABSTRACT FROM AUTHOR]

QoS-enabled networks consist of major functions: one is a TCP congestion control (TCC) mechanism at a source/sink node and the other is an active queue management (AQM) scheme at an intermediate node. In this paper, we introduce the major TCC mechanisms and AQM schemes, and provide analytical models and simulation-based comparisons of these TCC/AQM schemes for the purpose of identifying the reciprocal relationship between TCC mechanisms and AQM schemes in QoS-enabled networks. The results show that the equilibrium and dynamics of the underlying network depends on the harmony between the TCC/AQM pairs. The NewReno/PI pair, a feedback-based mechanism encompassing both network and end-systems, can enhance the performance of packet loss and delay sensitive applications. In our opinion, an appropriate combination of active queue management from the network and TCP source reaction would provide an effective solution to the instantaneous network fluctuation which occurs on the Internet. [ABSTRACT FROM AUTHOR]

There is a growing need to support quality-of-service (QoS) in mobile ad hoc networks. Supporting differentiated services (DiffServ) in mobile ad hoc networks, however, is very difficult because of the dynamic nature of mobile ad hoc networks, which causes network congestion. We propose DiffServ module to support differentiated service in mobile ad hoc networks through congestion control. Our DiffServ module uses the periodical rate control for real time traffic and also uses the best effort bandwidth concession when network congestion occurs. We evaluate our mechanism via a simulation study. Simulation results show our mechanism may offer a low and stable delay and a stable throughput for real time traffic in mobile ad hoc networks. [ABSTRACT FROM AUTHOR]

Over the years, quality of service (QoS) has attracted attention from researchers. How to guarantee QoS to customers despite the rapid change of the network status is the main concern. Pricing provides an effective economic means of congestion control and revenue generation. We examine pricing as an effective strategy for revenue management in DiffServ networks. In this paper, we propose an auction scheme to allocate network resources efficiently so as to maximize service provider's revenue. We examine an auction mechanism that provides multiple options for customers to bid on the resources that they require as well as the price they are willing to pay. The service provider acts as an admission control unit in the sense of deciding the admission price and service provided for each class. We target the goal of maximizing a service provider's revenue through auctions. [ABSTRACT FROM AUTHOR]

Unlike IntServ where resource reservation and admission control is per-flow based using RSVP, DiffServ supports aggregated traffic classes to provide various QoS to different classes of traffics. However, it is possible to lead to serious QoS violations without a QoS management support. Therefore, a QoS management system that can manage differentiated QoS provisioning is required. This paper proposes and implements a policy-based QoS management platform for differentiated services networks, which specifies QoS policies to guarantee dynamic QoS requirements. High-level QoS policies are represented as valid XML documents and are mapped into EJB beans of the EJB-based policy server of the platform. The policy distribution and the QoS monitoring are processed using SNMP. [ABSTRACT FROM AUTHOR]

Network traffic burst becomes a threat to network security. In this paper, a decomposition based method is presented for network burst traffic realtime prediction, in which, by passing smoothing filter, network traffic is decomposed into smooth low frequency traffic and high frequency traffic to make prediction respectively, and then a superposition result of the predictions is yielded. Based on LMS algorithm, an improvement of LMS predictor by adjusting prediction according to prediction errors (EaLMS, Error-adjusted LMS) is proposed to process the low frequency traffic, and a simple method of linear combination is presented to predict the high frequency traffic. The experiment results using real network traffic data shows, compared with traditional LMS, the prediction method based on decomposition obviously shorted the prediction delay and reduced the prediction error during traffic burst, while it also improves the global prediction. [ABSTRACT FROM AUTHOR]

With Voice over IP (VoIP) emerging as a viable alternative to the traditional circuit-switched telephony, it is vital that the two are able to intercommunicate. To this end, the IETF Signaling Transport (SIGTRAN) group has defined an architecture for seamless transportation of SS7 signaling traffic between a VoIP network and a traditional telecom network. However, at present, it is unclear if the SIGTRAN architecture will, in reality, meet the SS7 requirements, especially the stringent availability requirements. The SCTP transport protocol is one of the core components of the SIGTRAN architecture, and its failover mechanism is one of the most important availability mechanisms of SIGTRAN. This paper studies the impact of traffic load on the SCTP failover performance in an M3UA-based SIGTRAN network. The paper shows that cross traffic, especially bursty cross traffic such as SS7 signaling traffic, could indeed significantly deteriorate the SCTP failover performance. Furthermore the paper stresses the importance of configuring routers in a SIGTRAN network with relatively small queues. For example, in tests with bursty cross traffic, and with router queues twice the bandwidth-delay product, failover times were measured which were more than 50% longer than what was measured with no cross traffic at all. Furthermore, the paper also identifies some properties of the SCTP failover mechanism that could, in some cases, significantly degrade its performance. [ABSTRACT FROM AUTHOR]

This paper describes and tests a distributed bandwidth broker that has been implemented in NS simulator. It focuses on the admission control algorithm, its advantages and drawbacks. Also, the bandwidth broker is tested, managing the IP Premium service and we compare 2 different implementations of the service. Finally it approaches the problem of the optimal location of a bandwidth broker in a backbone network. For this purpose, a new model is proposed that evaluates each node and finally selects the most capable node where the base bandwidth broker should be located. [ABSTRACT FROM AUTHOR]

A new sampling model for measurement using IP packet identification (IPID) on IP network is provided in this paper under a principle of PSAMP, a working group of IETF, that a good sampling model should work for all purposes of measurement applications at the same time with a simple way. In the paper, and a multi-mask sampling model on the identification field can not only control sampling precise to 1/65536, but also use different sampling parameters among different measurement points. The randomicity and coordination of sampled packets can be assured automatically, and both network traffic performance and statistical characters are analyzed. [ABSTRACT FROM AUTHOR]

In recent years, requirements for performance evaluation techniques of a large-scale network have been increasing. However, the conventional network performance evaluation techniques, such as mathematical modeling and simulation, are suitable for comparatively small-scale networks. Research on parallel simulation has been actively done in recent years, which might be a possible solution for simulating a large-scale network. However, since most existing network simulators are event-driven, parallelization of a network simulator is not easy task. In this paper, a novel network model division method based on link-to-link traffic intensity for accelerating parallel simulator of a large-scale network is proposed. The key ideas of our network model division method are as follows: (1) perform steady state analysis for the network model that is to be simulated, and estimate all traffic intensities along links in steady state, (2) repeatedly apply the minimum cut algorithm from graph theory based on the estimated traffic intensities, so that the simulation model is divided at the link that has little traffic intensities in steady state. [ABSTRACT FROM AUTHOR]

Worm and Dos, DDos attacks take place more and more frequently nowadays. It makes the internet security facing serious threat. In this paper, we introduced the algorithm and design of ESTABD, an internet backbone Early-bird System of Traffic Anomaly Detection Based. By observing the raw variables such as packets count of protocol, TCP flags and payload length distribution etc., ESTABD analyzes real-time traffic to discover the abrupt traffic anomalous and generate warnings. A traffic anomaly detection algorithm based on Statistic Prediction theory is put forward and the algorithm has been tested on real network data. Further more, Alerts correlation algorithm and system policy are addressed in this paper to detect the known worms& Dos attacks and potentially unknown threats. [ABSTRACT FROM AUTHOR]

This paper addresses the provisioning VPN services over shared network infrastructure with QoS guarantees (bandwidth and propagation delay), attempt to minimise the bandwidth reservation on the network. We present general MILP formulations based on the hose model and the pipe model. The reformulated MILP can be solved by standard MILP packages efficiently and scalably. The benchmark results show that the over-provisioning factor about 5 in bandwidth reservation for VPN can be reduced by the hose model, compared with the pipe model. [ABSTRACT FROM AUTHOR]

Caching has been recognized as one of the most important techniques to reduce Internet bandwidth consumption caused by the tremendous growth of the WWW. Class-based LRU (C-LRU) delivers better results for the hit rate than most of the existing strategies, sharing the best and second place with GDS-Hit which provides better results for small cache sizes, since in this case cache places may still be unused. We study an extension of the C-LRU caching algorithm, namely Pass-Down-C-LRU (PD-C-LRU), to exploit these unused cache places for small cache sizes. We have found that the filling degrees of the classes affect the performance results for both hit rate as for the byte hit rate. Keywords: Caching, Class-based LRU, World Wide Web, Proxy Server. [ABSTRACT FROM AUTHOR]

Interest is used as a constraint to filter uninterested data in sensor networks. Within these interested data some are more valuable than others. Sometimes among these interested data, we hope to process the more important data first. By using Reward to denote the important level of data, in this paper, we present a packet scheduling algorithm by considering four constraints (Energy, Time, Reward, and Interest) simultaneously. Based on simulation result, we find out that our ETRI-PS packet scheduling algorithm can substantially improve the information quality and reduce energy consumption.This work is partially supported by the Ministry of Commerce, Industry & Energy, Korea. [ABSTRACT FROM AUTHOR]

A wireless sensor network is a new kind of wireless Ad-Hoc network consisting of a large number of small low cost, power constrained sensors deployed in a large area for gathering information for a large variety of applications. Since sensors are power constrained devices, it is quite important to organize them in some fashion in order to minimize total energy consumption in communication with base station. Clustering sensors into groups, so that sensors communicate information only to respective cluster heads and then cluster heads communicate the aggregated information to the processing center, is such an approach. In this paper, we propose an algorithm to organize sensors into clusters, which tries to extend the lifetime of network by forming balanced clusters as well as minimizing the total energy consumed in communication. In our algorithm, the number of hops is not fixed; rather it depends upon the spatial location of sensors. [ABSTRACT FROM AUTHOR]

Power Conservation is one of the most important challenges in wireless sensor networks. We propose two minimum-energy routing algorithms CODE and SIDE. CODE (COordination-based Data dissemination for sEnsor networks) addresses mobile sinks and considers energy efficiency not only in communication but also in idle-to-sleep state. SIDE (SInk cluster-based data Dissemination for sEnsor networks) addresses numerous stationary sinks and relies on loosely resource-constraints of a sink to ease the cost burden of sensor nodes. Our simulation results show that both algorithms reduce energy and prolong the network lifetimeThis research work has been partially supported by Korea Ministry of Information and Communication ITRC Program joint with SunMoon University.. [ABSTRACT FROM AUTHOR]

The quality and diversity of communication scenarios in distance education depend strongly on the available bandwidth. With the increase of existing network capacity teleteaching applications improve enormously in quality and quantity. Synchronous teleteaching which was initially just a video-stream based transmission of lectures is meanwhile enriched with multimedia applications and moves towards multimedia conferencing sessions. Advanced communication infrastructures for synchronous teleteaching applications are introduced. Solutions are based on standard desktop conferencing tools and streaming tools over IP on the one hand and transmission of media streams over ISDN and ATM codecs on the other hand. The pros and cons of each technology are outlined. Recommendations for appropriate usage are given. [ABSTRACT FROM AUTHOR]

VoIP is increasingly used in voice communication systems, where integration of legacy radios is an important feature. In addition to managing radio channel access, requiring Push-to-Talk (PTT) and Squelch signals, also cross coupling of radio channels is an important feature in air traffic control and public safety applications. Therefore we present a signaling approach based on the Session Initiation Protocol (SIP) in combination with a dynamic master slave model. It provides compatibility with standard SIP-phones and the existing expiry mechanism is used for detection of failure states. We complete our contribution with estimations of the audio and PTT-request delay in a coupled sector. [ABSTRACT FROM AUTHOR]

Hierarchical video allows to send different qualities of flow to clients from a single video file located on a server. Light clients (such as PDA) can't display this kind of video because of the lake of computing resources to decode (aggregate layers) the video in real-time. That's why we propose to distribute this aggregation on active nodes located along the video flow path between the video server and the light client (each active router decides independently to process packets). To achieve this the best way, we make our protocol respectful of others traffics in guaranteeing them a minimum part of active node resources. In order to guarantee some QoS level, active nodes check their resources and their interface congestion. Thus, in case of overloaded active nodes, they contact the video server to decrease the quality of the video to ease the network. This allows a hierarchical video to be displayed on a PDA with the best quality without disturbing others traffics. [ABSTRACT FROM AUTHOR]

For a typical portable handheld device, the backlight accounts for a significant percentage of the total energy consumption (e.g., around 30% for a Compaq iPAQ 3650). Substantial energy savings can be achieved by dynamically adapting backlight intensity levels on such low-power portable devices. In this paper, we analyze the characteristics of video streaming services and propose an adaptive scheme called Quality Adapted Backlight Scaling (QABS), to achieve backlight energy savings for video playback applications on handheld devices. Specifically, we present a fast algorithm to optimize backlight dimming while keeping the degradation in image quality to a minimum so that the overall service quality is close to a specified threshold. Additionally, we propose two effective techniques to prevent frequent backlight switching, which negatively affects user perception of video. Our initial experimental results indicate that the energy used for backlight is significantly reduced, while the desired quality is satisfied. The proposed algorithms can be realized in real time. [ABSTRACT FROM AUTHOR]

This paper proposes an intelligent scheme to enhance Quality of Service for video streaming over IP networks. The idea is to discard packets intelligently at a router in Active Networks (AN) before the buffer is full. This paper also presents an AN-based network node architecture to support the proposed scheme. Our simulation results show that it improves not only the visual quality per video stream but also network efficiency significantly. [ABSTRACT FROM AUTHOR]

A growing number of network applications create virtual networks called overlays on top of the Internet. Because advanced communication modes such as multicast have not been able to be successfully deployed at the network layer, they are now being implemented at the application layer thus creating such virtual networks. However these overlays require some form of addressing and routing inside themselves. Usually their topology is kept as simple as possible (e.g. tree, ring, etc.) but as their size increases, the need to be able to cope with a non trivial topology will increase. Our aim is to design a simple but robust addressing and routing scheme for topologically complex overlays. The only assumption is that the overlays are built upon the Internet and thus their topologies are constrained by the Internet topology. The benefit of our architecture is that they will not have to set up and maintain specific trivial topologies. In this paper we present the mechanisms of our distributed addressing and routing scheme. We have carried out simulations and we present some performance results of our routing algorithm such as path inflation and resistance to network dynamics. [ABSTRACT FROM AUTHOR]

This paper presents an evolutionary computation approach to optimise the design of communication networks where traffic forecasts are uncertain. The work utilises Fast Local Search (FLS), which is an improved hill climbing method and uses Guided Local Search (GLS) to escape from local optima and to distribute the effort throughout the solution space. The only parameter that needs to be tuned in GLS is called the regularization parameter lambda (λ). This parameter represents the degree up to which constraints on the features in the optimization problem are going to affect the outcome of the local search. To fine-tune this parameter, a series of evaluations were performed in several network scenarios to investigate the application towards network planning. Two types of performance criteria were evaluated: computation time and overall cost. Previous work by the authors has introduced the technique without fully investigating the sensitivity of λ on the performance. The significant result from this work is to show that the computational performance is relatively insensitive to the value of λ and a good value for the problem type specified is given. [ABSTRACT FROM AUTHOR]

The Stream Control Transmission Protocol (SCTP) is a reliable transport protocol to tackle the limitations of TCP and UDP. SCTP was originally designed to transport PSTN signaling messages over IP networks, but is also capable of serving as a general-purpose transport protocol. SCTP provides attractive features such as multi-streaming and multi-homing that may be helpful in high-mobility environment. SCTP congestion control mechanisms are based upon TCP congestion principals with the exception of the fast recovery algorithm. Original SCTP congestion control can perform badly in high-speed wide area networks because of its slow response with large congestion window. We proposed a new congestion control scheme based on the simple congestion window modification for SCTP to improve its performance in high-speed wide area networks. The results of several experiments we performed proved that our new suggested congestion control scheme for SCTP in high-speed network improved the throughput of the original SCTP congestion control scheme significantly. [ABSTRACT FROM AUTHOR]

Priority scheduling for packets is a hot topic, as interactive (voice,video) services are being integrated in existing data networks. In this paper, we consider a discrete-time queueing system with non-preemptive (or Head-Of-the-Line) priority scheduling and a general number of priority classes. Packets of variable length arrive in the queueing system. We derive expressions for the probability generating functions of the packet delays. From these functions, some performance measures (such as moments and approximate tail probabilities) are calculated. We apply the theoretical results to a queue that handles arriving multimedia traffic. [ABSTRACT FROM AUTHOR]

This paper considers the primary and secondary path generation problem in traffic engineering. We first present a standard MILP model. Since its size and integrality gap are very large, we then apply a Benders decomposition to isolate the failure case capacity constraints, related linearisation variables and linearisation constraints. The disaggregated Benders cuts are generated, which is actually the set of violated failure case capacity constraints with their linearisation variables and the required linearisation constraints. This corresponds to adding the failure case capacity constraints, their linearisation variables and linearisation constraints only as they are needed. Some results on generated test cases for different network topologies are given. In comparison with the standard MILP formulation, we reduce execution times on average by a factor of 1000 using the Benders decomposition. We also compare with a scheme of accepting demands one-by-one, which can handle more large-scale problems at the cost of loosing optimality. [ABSTRACT FROM AUTHOR]

The traffic management of IP networks faces increasing challenges, due to the occurrence of sudden and deep traffic variations in the network, which can be mainly attributed to the large diversity of supported applications and services, to the drastic differences in user behaviors, and to the complexity of traffic generation and control mechanisms. In this context, active traffic measurements are particularly important since they allow characterizing essential aspects of network operations, namely the quality of service measured in terms of packet delays and losses. The main goal of the work presented in this paper is the performance characterization of operational networks consisting in heterogeneous environments including both wired and wireless LANs, using active measurements. We propose a measurement methodology and its corresponding measurement platform. The measurement methodology is based on the One-Way Active Measurement Protocol (OWAMP), a recent proposal from the Internet2 and IETF IPPM groups for measuring delays and losses in a single direction. The measurement platform was implemented, tested and conveniently validated in different network scenarios. Keywords: Network management, traffic monitoring, active measurement, OWAMP. [ABSTRACT FROM AUTHOR]

Recently, the interest in sensor network has increased with the advanced technologies in the field of digital signal processing, sensing and wireless networking devices. In this paper, an efficient protocol to set up a data dissemination path shared among multiple sink nodes is proposed for a special sensor network, where the source sensor nodes update their sensed data according to various desired update rates requested by sink nodes. We modify and enhance the basic SAFE(Sinks Accessing data From Environments) protocol to minimize the increased amount of data update rate at the intermediate nodes over a dissemination path. By using GloMoSim simulator, we show that our ESAFE (Enhanced SAFE) protocol outperforms the basic SAFE. [ABSTRACT FROM AUTHOR]

Data dissemination is a fundamental task in wireless sensor networks. Because of the radios range limitation and energy consumption constraints, sensor data is commonly disseminated in a multihop fashion (flat networks) through a tree topology. However, to the best of our knowledge none of the current solutions worry about the moment when the dissemination topology needs to be rebuilt. This work addresses such problem introducing the use of information fusion mechanisms, where the traffic is handled as a signal that is filtered and translated into evidences that indicate the likelihood of critical failures occurrence. These evidences are combined by a Dempster-Shafer engine to detect the need for a topology reconstruction. Our solution, called Diffuse, is evaluated through a set of simulations. We conclude that information fusion is a promising approach that can improve the performance of dissemination algorithms for wireless sensor networks by avoiding unnecessary traffic. [ABSTRACT FROM AUTHOR]

Most of the existing power saving protocols are designed for irregular networks. These protocols can also be applied to regular networks, but these protocols do not consider the characteristics of regular networks and thus are more complicated and less efficient than the protocols designed for regular networks. Therefore, we propose a novel power management protocol for regular WSNs. Gathering information to the base station is an important operation for WSN. Hence, even some nodes switch to PS mode, the network still needs to be connected so that the sensed information can be sent to the base station through the active nodes. The goal of our protocols is to choose several different connected dominating sets, so that these connected dominating sets can switch to active mode in turn to serve other nodes in PS mode. Simulation results show that our power management protocol can conserve lots of power and greatly extend the lifetime of the WSN with a reasonable extra transmission delay. [ABSTRACT FROM AUTHOR]

A strategy for energy saving in wireless sensor networks is to manage the duty cycle of sensors, by dynamically selecting a different set of nodes to be active in every moment. We propose a strategy for node selection in multihop sensor networks that prioritizes nodes with larger residual energy and relevance for the application. The proposed scheme is based on an implementation of the knapsack algorithm and it seeks to maximize the network lifetime, while assuring the application QoS. An environmental monitoring application was simulated and huge energy savings were achieved with the proposed scheduling algorithm. [ABSTRACT FROM AUTHOR]

Most wireless sensor networks (WSN) researches assume that the network is connected and there is always a path connected by wireless links between a source and a destination. In this paper, we argue that network partitioning is not an uncommon phenomenon for practical WSN applications, especially when the sensor nodes are deployed in a hash working environment. We first present a simple distributed method to detect the occurrence of network partitions. Some critical survival nodes would be selected to re-connect to the sink after certain network disruption happens. Two reconnection approaches, Transmission Range Adjustment (TRA) and Message Ferry (MF), are then proposed. We study their performances in terms of power consumption by taking the specifications of the commercial sensor nodes into account. Simulation results show that TRA is more appropriate for the current implementation of WSN. However, MF has the potential to be more energy-efficient if there is a powerful wireless transmitter and a larger amount of buffers at each sensor node. [ABSTRACT FROM AUTHOR]

Today's Internet is a loose federation of independent network providers, each acting in their own self interest. With the ISPs forming with peer relationship under this economic reality, [1] proves that the total cost of "hot potato" routing is much worse than the optimal cost and then gives a price mechanism—one ISP charges the other a price per unit flow, to prevent this phenomenon. However, with its mechanism the global welfare loss may be arbitrarily high. In this paper we propose a new price mechanism—one ISP charges the other a given fee for different flow scale. With our mechanism, we show that if both ISPs agree on splitting the flow according to the max global welfare the charging ISP will get more profit and the charged ISP will achieve the least cost. And our new mechanism can almost eliminate the welfare loss. Finally, some instances are given and the results show that our mechanism is much more effective than that in [1]. [ABSTRACT FROM AUTHOR]

These days, the majority of large systems serving large numbers of users prefer N-tier architecture because of its scalability and flexibility. To maintain the quality of service in these systems, we need to understand how much delay is generated in each tier. However, the structure and the behavior of this architecture is so complicated that it is difficult to analyze these delays without installing special software or hardware - improvements that might change the server's behavior or result in significant additional costs. To solve these problems, we developed a practical method for estimating the delays generated in each tier of N-tier architecture that uses only easily obtainable parameters. In this paper, we first discuss what these easily obtainable parameters are. We then construct a performance model of the N-tier architecture using these parameters and analyze the delays in the model. Finally, we describe the experiments we conducted to evaluate our approach. [ABSTRACT FROM AUTHOR]

This paper introduces PrometeoAvailable under the GPL license on sourceforge. See http://prometeo-proxy.sourceforge.net/ a multi-function, modular and extensible proxy server created as part of one the author's thesis work. We will discuss the needs that this project was meant to address: mainly the lack of an application with the aforesaid features, combined with native IPv6 support and ease of administration. Prometeo also provides a C++ framework which simplifies the development of networking applications. The design of Prometeo's will be described, starting with an overview of its components and modules and commenting on the most significant parts of the implementation. Then we will focus on the main issues considered during the development of the project, comparing the adopted solutions with those of other state-of-the-art packages like Squid [1]. Finally we will discuss new ways of improving Prometeo's performances and scalability.This work has been partially supported by the FIRB project named WebMinds of the Italian Ministry for Education, University and Research and by the 6NET E.U. project. [ABSTRACT FROM AUTHOR]