Wide Area Network

Low Power Wide Area (LPWA) networks are attracting a lot of attention primarily because of their ability to offer affordable connectivity to the low-power devices distributed over very large geographical areas. In realizing the vision of the Internet of Things (IoT), LPWA technologies complement and sometimes supersede the conventional cellular and short range wireless technologies in performance for various emerging smart city and machine-to-machine (M2M) applications. This review paper presents the design goals and the techniques, which different LPWA technologies exploit to offer wide-area coverage to low-power devices at the expense of low data rates. We survey several emerging LPWA technologies and the standardization activities carried out by different standards development organizations (e.g., IEEE, IETF, 3GPP, ETSI) as well as the industrial consortia built around individual LPWA technologies (e.g., LORa Alliance,WEIGHTLESS-SIG, and DASH7 Alliance). We further note that LPWA technologies adopt similar approaches, thus sharing similar limitations and challenges. This paper expands on these research challenges and identifies potential directions to address them. While the proprietary LPWA technologies are already hitting the market with large nationwide roll-outs, this paper encourages an active engagement of the research community in solving problems that will shape the connectivity of tens of billions of devices in the next decade.

With the advancements in smart grid, communication technology, intelligent electronic device and substation automation, wide area applications for monitoring, protection, control and fault location becoming focused nowadays and improved from time to time. This research focuses on using wide area synchrophasor measurements for fault location in transmission network which acts as a backup to conventional fault location method. Simple reactance based methods together with a developed rules system are used to locate the possible affected line and its fault location. Using the developed rules and algorithm, fault location impedance will be compared at each synchrophasor bus connected lines for different fault types, then between connected lines and finally between synchrophasors buses. Faults at various locations with different fault resistances have been simulated and the results prove that the developed method can be used to locate the fault point and can be used as a backup to main fault location method. Future works also discussed how the method can be improved to get the best and accurate fault location results.

This paper presents an intrusion detection system architecture based on the artificial immune system concept. In this architecture, an innate immune mechanism through unsupervised machine learning methods is proposed to primarily categorize network traffic to "self" and "non-self" as normal and suspicious profiles respectively. Unsupervised machine learning techniques formulate the invisible structure of unlabeled data without any prior knowledge. The novelty of this work is utilization of these methods in order to provide online and real-time training for the adaptive immune system within the artificial immune system. Different methods for unsupervised machine learning are investigated and DBSCAN (density-based spatial clustering of applications with noise) is selected to be utilized in this architecture. The adaptive immune system in our proposed architecture also takes advantage of the distributed structure, which has shown better self-improvement rate compare to centralized mode and provides primary and secondary immune response for unknown anomalies and zero-day attacks. The experimental results of proposed architecture is presented and discussed.

The electronic government (E-Gov) systems are currently getting recognized as an authentic strategically tool in delivering E-services. Considering the development of information system (IS) as well as the expanding of the internet-based applications in KSA, E-Gov has always been a significant aspect in delivering governmental services. This research has adopted the (IS) success model by both DeLone and McLean (D&M), moreover, it adopted technology acceptance model (TAM) with cybersecurity factors, both models were implemented to discover the status of the IS success then investigate cybersecurity aspects that impact the service efficiency and effectiveness in KSA. Consequently, this research aims to create a model to investigate the IS success model along with cybersecurity factors that influence E-Gov services effectiveness and usage. Therefore, a survey has been applied as the major data gathering approach; the survey has been distributed among 211 users of E-Gov services consistently. Moreover, all research findings were attained through a quantitative method using the structural equation modelling (SEM). Findings revealed that the constructs fundamental of the (IS) success model are strongly influencing users' satisfaction (US) of the E-Gov services; correspondingly, the fundamental constructs factors of cybersecurity with TAM appear to have a strong impacts on perceived risk (PR), in addition, both which affect the E-Gov services towards usage and effectiveness.

Indoor wireless systems poses one of the biggest design challenges although it is the most flexible and easily deployable method of implementing Local Area Networks. This difficulty in predicting the propagation of radio frequency wave in indoor environments is caused by reflection, refraction, diffraction and scattering of signals due to closed proximities to furniture, walls, human beings, and reflectors like ceiling, mirrors and glasses. To help improve the user experience and guarantee good quality of service in indoor situations, the research investigated the throughput and attenuation effect on signal with respect to 4, 5, 6 and 9 inches sizes of blocks walls respectively. The characterized Path-loss exponent was 1.999 and differed from the free space model, Wall and Floor Factor model and ITU model by 53.54dB, 6.42dB and 6.85dB respectively.

Wireless broadband technologies provide ubiquitous broadband access to wireless users, enabling services that were available only to wireline users. In this paper, we summarize emerging wireless broadband access technologies, ranging from WLANs to satellite communications.,We explain the latest standards,in the IEEE 802.11 and IEEE 802.16 families in detail. The MAC layer mechanisms of IEEE 802.11e, 802.11n, and 802.11s standards

In this paper, Integer Programming based methodology is presented for
the optimal placement of Phasor Measurement Unit (PMU) that
minimizes the cost of installation and provide the entire power system
observability. The concepts of zero injection buses are used in this
paper for further reduction in number of PMUs. Integer Programming
may produce multiple results if neighboring buses to zero injection
buses are not handled properly. Though all the results are correct but
create confusion in selecting one of them. In order to mitigate this
problem a criterion has been proposed in this paper to select the
appropriate location of PMU in such circumstances. The proposed
algorithm is tested on IEEE 14-bus, IEEE 24-bus and IEEE 30-bus
systems.

The design of a platform for bi-directional musical performance using modern WAN networks poses several challenges that are different from related applications, e.g., synchronous LAN studio systems or uni-directional WAN streaming. The need to minimize as much as possible audio latency and also maximize audio quality requires specific strategies which are informed, in part, by musical decisions.

This paper presents the design, development and evaluation of Virtual Showroom that focused on interactivity in by manipulating the capabilities of VRML technology. The Virtual Showroom provides virtual furniture that can be viewed, navigated and interacted by the user. Besides that, users are given an option to create the interior design of their own room by dragging virtual furniture provided. Development process involves specific process such as planning, object modeling, navigation, web page integration and evaluation. Evaluation has been done using questionnaire by 30 participants that concentrate on six criteria such as ease of navigation, effectiveness of the interface and user acceptance. Result shows that all of the participants give positive feedback regarding the evaluated criteria and it proves that the objectives of the project have been successfully achieved and able to satisfy both the developer and customers. The development of Virtual Showroom showed that it is possible to have a virtual furniture shop that provided full control for the user while navigating. This can gave a new perspective for the user while do online shopping. The next step is to enhance the application by integrating avatar in order to help first time users in navigating the virtual showroom.

After tightening up network perimeter for dealing with external threats, organizations have woken up to the threats from inside Local Area Networks (LAN) over the past several years. It is thus important to design and implement LAN security strategies in order to secure assets on LAN by filtering traffic and thereby protecting them from malicious access and insider attacks. Banking Financial Services and Insurance (BFSI) industry is one such segment that faces increased risks and security challenges. The typical architecture of this segment includes several thousands of users connecting from various branches over Wide Area Network (WAN) links crossing national and international boundaries with varying network speed to access data center resources. The objective of this work is to deploy LAN security solution to protect the data center located at headquarters from the end user machines. A LAN security solution should ideally provide Network Access Control (NAC) along with cleaning (securing) the traffic going through it. Traffic cleaning itself includes various features like firewall, intrusion detection/prevention, traffic anomaly detection, validation of asset ownership etc. LANenforcer (LE) is a device deployed in front of the data center such that the traffic from end-user machines necessarily passes through it so that it can enforce security. The goal of this system is to enhance the security features of a LANenforcer security system with Intrusion Prevention System (IPS) to enable it to detect and prevent malicious network activities. IPS is plugged into the packet path based on the configuration in such a way that the entire traffic passes through the IPS on LE.

The allocation of data to nodes in a computer communications network is a critical issue in distributed database design, specially in wide area network where optimizing the distributed queries is the main objective. Numerous models of data allocation have been presented so far no optimal or universally accepted algorithm exists yet, and very few algorithms have been implemented to date (Rob and Cornonel, 1993). In this paper a method to construct a model of data allocation for distributed database system has been proposed. The adopted method for the construction of the data allocation model leads to an efficient model of its kind. The proposed model not only solves distributed database design problem, but also solves distributed database maintenance problem by covering initial allocation and post allocation of the data. The efficiency of proposed model has been proved by comparing proposed model with other relevant models.

We present Globule, a collaborative content delivery network developed by our research group. Globule is composed of Web servers that cooperate across a wide-area network to provide performance and availability guarantees to the sites they host. We discuss the issues involved in developing and setting up a large-scale collaborative CDN and provide solutions for many of its unique problems.

We propose a two level model for TCP connection arrivals in local area networks (LAN). The £rst level are user sessions whose arrival is timevarying Poisson. The second level are connections within a user session. Their number and mean interarrival are independent and biPareto across user session. The interarrivals within a user session are Weibull, and across all users are correlated Weibull. Our model has a small number of parameters which are inferred from real traf£c collected at a £rewall. We show that traf£c synthesized with our model closely matches the original data. We extend this approach to a general model involving shot noise and show it is asymptotically consistent with more common fractal models used in data networks. Finally, we show that this model extends to the wide area network applications without alteration and it predicts smoothing of wide area network traf£c pro£le due to spatial aggregation, which we observe experimentally by synthetically creating large aggregate TCP load.

The transition from synchronous transport methods to IP for production quality video and audio services implies a deterioration of the timing quality of the signals, since IP is a completely asynchronous transport format. IEEE 1588 (PTP) has been introduced to convey precise timing over an IP network. In the Studio LAN, reaching the required quality level of timing transport with PTP is manageable, but doing it in the WAN is very challenging. In practice the only wide area solution today is to use GPS controlled Grand Master (GM) clocks at each remote location to provide synchronization with sufficient quality. This scheme has some disadvantages in that it depends on that a GPS signal is always available, which may not be the case, for several reasons. The industry also needs solutions for PTP transport over the terrestrial WANs. We will describe the challenges with PTP over the WAN, but also show how a synchronous overlay on top of the IP network can provide sufficient PTP quality over the WAN for professional Audio and Video services without resorting to GPS controlled GMs at each end point. Real operational cases using this functionality will be described.

The SD-WAN is network architecture of the virtual wide-area system which provides facility to network services to better invest in broadband, LTE, MPLS internet services included in the transport services. This paper consists of full analysis review of SD-WAN and its logical architecture for further development according to the new generation internet demands. During analysis of existing architectures many limitations were found like existing architecture of wan is no more capable to provide high performance with the massive bandwidth of data being on websites, full edge functionalities of data servers and network services. Newly developed advanced applications and with new upgraded technology has inflated the requirements of the long-distance data transmission, which leads to redesigning the wide-area network with a newly designed structure and perspectives which accomplishes the network demands. Some good features also identified like some of the vulnerabilities that can be possible to obtain the information of the version of operating system, version of web server, and type of device which can be used to detect vulnerabilities in the network device.

Remote device and network management can play an important role in realizing efficient and user-friendly deployment of fixed-mobile converged network services. TR-069 is currently the most popular remote-management protocol in the DSL world, but is not used in mobile networks. This paper investigates the applicability of TR-069 for remote device management of mobile devices. We installed a TR-069 client on a mobile phone, and measured the performance of the protocol in relation to the properties of the mobile data connection and the small footprint of the mobile device. The results confirm theoretical considerations derived from literature. The main conclusion is that TR-069 can be safely used for remote management of mobile devices, but requires a higher connection capacity of the remote management server due to the longer connection times in mobile networks.

Routing 1protocols determines the shortest path to transfer the data from one host to another and specify how communication takes place between each routers. There are different classes of routing protocols are available in different environments such as intra and inter Autonomous System (AS).A routing protocol can be static or dynamic as well as link state and path vector. We will focus on Open Shortest Path First (OSPF) and Border Gateway Protocol (BGP), OSPF and BGP protocols are dynamic in nature. BGP is aninter-autonomous system routing protocol and OSPF is an intra-a utonomous system routing
protocol. We can analyze the performance of Wide Area Network (WAN) by enabling the Interior Gateway
Protocol (IGP) and Exterior Gateway Protocol (EGP) of the network and ensure the Quality of Service (QoS).

As the use of the Internet continues to grow explosively, edge computing has emerged as an important technique for delivering Web content over the Internet. Edge computing moves data and computation closer to end-users for fast local access and better load distribution. Current approaches use caching, which does not work well with highly dynamic data. In this paper, we propose a different approach to enhance edge computing. Our approach lies in a wide area data replication protocol that enables the delivery of dynamic content with full consistency guarantees and with all the benefits of edge computing, such as low latency and high scalability. What is more, the proposed solution is fully transparent to the applications that are brought to the edge. Our extensive evaluations in a real wide area network using TPC-W show promising results. Figure 10. Scenario 2: Clustered edge servers (10 servers) at four cites

The relative performance of di erent data collection methods in the assessment of various tra c parameters is signi cant when the amount of data generated by a complete trace of a tra c interval is computationally overwhelming, and even capturing summary statistics for all tra c is impractical. This paper presents a study of the performance of various methods of sampling in answering questions related to wide area network tra c characterization. Using a packet trace from a network environment that aggregates tra c from a large number of sources, we simulate various sampling approaches, including time-driven and event-driven methods, with both random and deterministic selection patterns, at a variety of granularities. Using several metrics which indicate the similarity between two distributions, we then compare the sampled traces to the parent population. Our results revealed that the timetriggered techniques did not perform as well as the packettriggered ones. Furthermore, the performance di erences within each class (packet-based or time-based techniques) are small.

This paper proposes a traffic-responsive urban traffic control strategy allowing a real time passive public transport priority. The proposed strategy is based on a store and forward modeling of both of the private vehicle and Public transport traffic. The regulator is designed using the linear quadratic, which allows a traffic responsive co-ordinated control for wide-area networks. The objective of this strategy is to control the junctions traffic lights in order to improve the traffic performance on the sections at the precise times when public transport is using the service sections. A simulation example is provided to demonstrate the efficiency of the proposed strategy.

Active-X technologies deployed on the client side of the architecture do not only reduce the burden on the server and network bandwidth but also loosely coupled with the server for flexible update of the site content without affecting user interface. The interface design permits quicker search of a specific product without sacrificing the appeal of 3D interactions and navigation. Such features are appealing to both utilitarian and hedonic online customers.

Power consumption in general, and of ICT technologies in particular, has become a key issue during the last few years. The ratio of power demand versus power resources is constantly growing, and energy cost is increasing at a constant rate. The electricity jumped up of about 35% in Italy during the period 2004-2007 (1). Moreover, Green House Gases (GHG) emissions

According to several studies, the power consumption of the Internet accounts for up to 10% of the worldwide energy consumption, and several initiatives are being put into place to reduce the power consumption of the ICT sector in general. To this goal, we propose a novel approach to switch off network nodes and links while still guaranteeing full connectivity and maximum link utilization. After showing that the problem falls in the class of capacitated multi-commodity flow problems, and therefore it is NP-complete, we propose some heuristic algorithms to solve it. Simulation results in a realistic scenario show that it is possible to reduce the number of links and nodes currently used by up to 30% and 50% respectively during off-peak hours, while offering the same service quality.

In this paper, we analyze virtual machine (VM) scalability on multi-core systems for compute-, memory-, and network I/O-intensive workloads. The VM scalability evaluation under these three workloads will help cloud users to understand the performance impact of underlying system and network architectures. We demonstrate that VMs on the state-of-the-art multi-core processor based systems scale as well as multiple threads on native SMP kernel for CPU and memory intensive workloads. Intra-VM communication of network I/O intensive TCP message workload has a lower overhead compared to multiple threads when VMs are pinned to specific cores. However, VM scalability is severely limited for such workloads for across-VM communication on a single host due to virtual bridges. For across local and wide area network communication, the network bandwidth is the limiting factor. Unlike previous studies that use workload mixes, we apply a single workload type at a time to clearly attribute VM scalability bottlenecks to system and network architectures or virtualization itself.

In data grids, many distributed scientific and engineering applications often require access to a large amount of data (terabytes or petabytes). Data access time depends on bandwidth, especially in a cluster grid. Network bandwidth within the same cluster is larger than across clusters. In a communication environment, the major bottleneck to supporting fast data access in Grids is the high latencies of Wide Area Networks (WANs) and Internet. Effective scheduling in such network architecture can reduce the amount of data transferred across the Internet by dispatching a job to where the needed data are present. Another solution is to use a data replication mechanism to generate multiple copies of the existing data to reduce access opportunities from a remote site. To utilize the above two concepts, in this paper we develop a job scheduling policy, called HCS (Hierarchical Cluster Scheduling), and a dynamic data replication strategy, called HRS (Hierarchical Replication Strategy), to improve the data access efficiencies in a cluster grid. We simulate our algorithm to evaluate various combinations of data access patterns. We also implement HCS and HRS in the Taiwan Unigrid environment. The simulation and experiment results show that HCS and HRS successfully reduces data access time and the amount of inter-cluster-communications in comparison with other strategies in a cluster grid.

In this paper, we analyze virtual machine (VM) scalability on multi-core systems for compute-, memory-, and network I/O-intensive workloads. The VM scalability evaluation under these three workloads will help cloud users to understand the performance impact of underlying system and network architectures. We demonstrate that VMs on the state-of-the-art multi-core processor based systems scale as well as multiple threads on native SMP kernel for CPU and memory intensive workloads. Intra-VM communication of network I/O intensive TCP message workload has a lower overhead compared to multiple threads when VMs are pinned to specific cores. However, VM scalability is severely limited for such workloads for across-VM communication on a single host due to virtual bridges. For across local and wide area network communication, the network bandwidth is the limiting factor. Unlike previous studies that use workload mixes, we apply a single workload type at a time to clearly attribute VM scalability bottlenecks to system and network architectures or virtualization itself.

We propose a two level model for TCP connection arrivals in local area networks (LAN). The £rst level are user sessions whose arrival is timevarying Poisson. The second level are connections within a user session. Their number and mean interarrival are independent and biPareto across user session. The interarrivals within a user session are Weibull, and across all users are correlated Weibull. Our model has a small number of parameters which are inferred from real traf£c collected at a £rewall. We show that traf£c synthesized with our model closely matches the original data. We extend this approach to a general model involving shot noise and show it is asymptotically consistent with more common fractal models used in data networks. Finally, we show that this model extends to the wide area network applications without alteration and it predicts smoothing of wide area network traf£c pro£le due to spatial aggregation, which we observe experimentally by synthetically creating large aggregate TCP load.

Applications that explore, query, analyze, visualize, and, in general, process very large scale data sets are known as Data Intensive Applications. Large scale data intensive computing plays an increasingly important role in many scientific activities and commercial applications, whether it involves data mining of commercial transactions, experimental data analysis and visualization, or intensive simulation such as climate modeling. By combining high performance computation, very large data storage, high bandwidth access, and high-speed local and wide area networking, data intensive computing enhances the technical capabilities and usefulness of most systems. The integration of parallel and distributed computational environments will produce major improvements in performance for both computing intensive and data intensive applications in the future. The purpose of this introductory article is to provide an overview of the main issues in parallel data intensive computing in scientific and commercial applications and to encourage the reader to go into the more in-depth articles later in this special issue.

Software defined Wide Area Networking (SD-WAN) is considered as a novel architecture and key technology for future network model. The baseline model for SDN is used to couple data and control plane, facilitating flexible, centralized and networking control. Even though, Wide Area Network such as data centre network have various like SDN, it is still measured as crisis to deploy SDN in Wide area networks (WANs). Prevailing works like multiple controllers are needed in WANs with covering SDN domain. Moreover, SDN controller placement and domain partition problems have to be addressed. Therefore, this work proposed Game theory model based Nash equilibrium concept for placement and partition algorithms that may partition huge network into numerous small SDWAN effectually and efficiently. In this algorithm, Nash equilibrium is utilized stability and discovers SDN and determine optimal amount of SDN automatically. To compute this model, a new experimental structure is structured with WAN topologies. The outcomes demonstrate efficiency of algorithm for controller placement and domain partition crisis.

The requirements of wide-area distributed database systems differ dramatically from those of local-area network systems. In a wide-area network (WAN) configuration, individual sites usually report to different system administrators, have different access and charging algorithms, install site-specific data type extensions, and have different constraints on servicing remote requests. Typical of the last point are production transaction environments, which are fully engaged during normal business hours, and cannot take on additional load. Finally, there may be many sites participating in a WAN distributed DBMS.

As part of an NIH-funded study of malaria pathogenesis, a magnetic resonance (MR) imaging research facility was established in Blantyre, Malaŵi to enhance the clinical characterization of pediatric patients with cerebral malaria through application of neurological MR methods. The research program requires daily transmission of MR studies to Michigan State University (MSU) for clinical research interpretation and quantitative post-processing. An intercontinental satellite-based network was implemented for transmission of MR image data in Digital Imaging and Communications in Medicine (DICOM) format, research data collection, project communications, and remote systems administration. Satellite Internet service costs limited the bandwidth to symmetrical 384 kbit/s. DICOM routers deployed at both the Malaŵi MRI facility and MSU manage the end-to-end encrypted compressed data transmission. Network performance between DICOM routers was measured while transmitting both mixed clinical MR studies and synthetic studies. Effective network latency averaged 715 ms. Within a mix of clinical MR studies, the average transmission time for a 256 × 256 image was 2.25 and~6.25 s for a 512 × 512 image. Using synthetic studies of 1,000 duplicate images, the interquartile range for 256 × 256 images was [2.30, 2.36] s and [5.94, 6.05] s for 512 × 512 images. Transmission of clinical MRI studies between the DICOM routers averaged 9.35 images per minute, representing an effective channel utilization of~137% of the 384-kbit/s satellite service as computed using uncompressed image file sizes (including the effects of image compression, protocol overhead, channel latency, etc.). Power unreliability was the primary cause of interrupted operations in the first year, including an outage exceeding 10 days.

In this paper, we report on some preliminary results from an in-depth, wavelet-based analysis of a set of high-quality, packet-level tra c measurements, collected over the last 6-7 years from a number of di erent working wide-area networks (WANs). We rst validate and con rm an earlier nding, originally due to Paxson and Floyd 12], that actual WAN tra c is consistent with statistical self-similarity for su ciently large time scales. We then relate this large-time scaling phenomenon to the empirically observed characteristics of WAN tra c at the level of individual connections or applications. In particular, we present here original results about a detailed statistical analysis of Web-session characteristics, and report on an intriguing scaling property of measured WAN tra c at the transport layer (i.e., number of TCP connection arrivals per time unit). This scaling property of WAN tra c at the TCP layer was absent in the pre-Web period but has become ubiquitous in today's WWW-dominated WANs and is a direct consequence of the ever-increasing popularity of the Web (WWW) and its emergence as the major contributor to WAN tra c. Moreover, we show that this changing nature of WAN tra c can be naturally accounted for by self-similar tra c models, primarily because of their ability to provide physical explanations for empirically observed tra c phenomena in a networking context. Finally, we provide empirical evidence that actual WAN tra c traces also exhibit scaling properties over small time scales, but that the small-time scaling phenomenon is distinctly di erent from the observed large-time scaling property. We relate this newly observed characteristic of WAN tra c to the e ects that the dominant network protocols (e.g., TCP) and controls have on the ow of packets across the network and discuss the potential that multifractals have in this context for providing a structural modeling approach for WAN tra c and for capturing in a compact and parsimonious manner the observed scaling phenomena at large as well as small time scales.

In this paper we present a middleware infrastructure, called DataCutter, that enables processing of scientific datasets stored in archival storage systems across a widearea network. DataCutter provides support for subsetting of datasets through multidimensional range queries, and application specific aggregation on scientific datasets stored in an archival storage system. We also present experimental results from a prototype implementation.

We present a protocol for general state machine replication - a method that provides strong consistency - that has high performance in a wide-area network. In particular, our protocol Mencius has high throughput under high client load and low latency under low client load even under ...

We present the architecture, technology and experimental applications of a real-time, multi-site, interactive and collaborative environment called Distributed Immersive Performance (DIP). The objective of DIP is to develop the technology for live, interactive musical performances in which the participants -subsets of musicians, the conductor and the audience -are in different physical locations and are interconnected by very high fidelity multichannel audio and video links. DIP is a specific realization of broader immersive technology -the creation of the complete aural and visual ambience that places a person or a group of people in a virtual space where they can experience events occurring at a remote site or communicate naturally regardless of their location. The DIP experimental system has interaction sites and servers in different locations on the USC campus and at several partners, including the New World Symphony of Miami Beach, FL. The sites have different types of equipment to test the effects of video and audio fidelity on the ease of use and functionality for different applications. Many sites have high-definition (HD) video or digital video (DV) quality images projected onto wide screen wall displays completely integrated with an immersive audio reproduction system for a seamless, fully three-dimensional aural environment with the correct spatial sound localization for participants. The system is capable of storage and playback of the many streams of synchronized audio and video data (immersidata), and utilizes novel protocols for the low-latency, seamless, synchronized realtime delivery of immersidata over local area networks and widearea networks such as Internet2. We discuss several recent interactive experiments using the system and many technical challenges common to the DIP scenario and a broader range of applications.

The MALLBA project tackles the resolution of combinatorial optimization problems using generic algorithmic skeletons implemented in C++. A skeleton in the MALLBA library implements an optimization method in one of the three families of generic optimization techniques offered: exact, heuristic and hybrid. Moreover, for each of those methods, MALLBA provides three different implementations: sequential, parallel for Local Area Networks, and parallel for Wide Area Networks. This paper introduces the architecture of the MALLBA library, details some of the implemented skeletons, and offers computational results for some classical optimization problems to show the viability of our library. Among other conclusions, we claim that the design used to develop the optimization techniques included in the library is generic and efficient at the same time. Parallel Computing 32 (2006) 415-440 www.elsevier.com/locate/parco environments have some characteristics different from LAN ones. The main features of WAN networks are: higher communication overhead, heterogeneity, unstable behavior of the links, security restrictions, and frequent faulty scenarios.

We present the architecture, technology and experimental applications of a real-time, multi-site, interactive and collaborative environment called Distributed Immersive Performance (DIP). The objective of DIP is to develop the technology for live, interactive musical performances in which the participants -subsets of musicians, the conductor and the audience -are in different physical locations and are interconnected by very high fidelity multichannel audio and video links. DIP is a specific realization of broader immersive technology -the creation of the complete aural and visual ambience that places a person or a group of people in a virtual space where they can experience events occurring at a remote site or communicate naturally regardless of their location. The DIP experimental system has interaction sites and servers in different locations on the USC campus and at several partners, including the New World Symphony of Miami Beach, FL. The sites have different types of equipment to test the effects of video and audio fidelity on the ease of use and functionality for different applications. Many sites have high-definition (HD) video or digital video (DV) quality images projected onto wide screen wall displays completely integrated with an immersive audio reproduction system for a seamless, fully three-dimensional aural environment with the correct spatial sound localization for participants. The system is capable of storage and playback of the many streams of synchronized audio and video data (immersidata), and utilizes novel protocols for the low-latency, seamless, synchronized realtime delivery of immersidata over local area networks and widearea networks such as Internet2. We discuss several recent interactive experiments using the system and many technical challenges common to the DIP scenario and a broader range of applications.

In an all-optical wide area network, some network nodes may handle heavier volumes of traffic. It is desirable to allocate more full-range wavelength converters (FWC's) to these nodes, so that the FWC's can be fully utilized to resolve wavelength conflict. In this paper, we propose a set of algorithms for allocating FWC's in all-optical networks. We adopt the simulation-based optimization approach, in which we collect utilization statistics of FWC's from computer simulations and then perform optimization to allocate the FWC's. Therefore, our algorithms are widely applicable and they are not restricted to any particular model or assumption. We have conducted extensive computer simulations on regular and irregular networks under both uniform and nonuniform traffic. Compared with the best existing allocation, the results show that our algorithms can significantly reduce: 1) the overall blocking probability (i.e., better mean quality of service) and 2) the maximum of the blocking probabilities experienced at all the source nodes (i.e., better fairness). Equivalently, for a given performance requirement on blocking probability, our algorithms can significantly reduce the number of FWC's required.

Grid computing frameworks built on top of the TCP/IP protocol stack are efficient in local area networks (LANs), where almost dedicated network resources are available. Supporting distributed grid computing applications connected by Wide Area Networks (WANs), i.e. global grid computing, represent a more challenging task that requires the availability of network protocols capable of guaranteeing Quality of Service (QoS). In this paper we propose to utilize a Service Oriented Automatic Switched Transport Network (SO-ASTN) as the transport infrastructure for supporting global grid computing. The SO-ASTN consists of the addition to the plain ASTN of an extra layer, namely the service plane, designed according to the ITU-T Intelligent Network Conceptual Model. The main novelty of the architecture is the network awareness that grid computing applications are provided with. Global grid computing applications can therefore experience LAN QoS level in a Wide Area Network (WAN) scenario.

We propose a two level model for TCP connection arrivals in local area networks (LAN). The £rst level are user sessions whose arrival is timevarying Poisson. The second level are connections within a user session. Their number and mean interarrival are independent and biPareto across user session. The interarrivals within a user session are Weibull, and across all users are correlated Weibull. Our model has a small number of parameters which are inferred from real traf£c collected at a £rewall. We show that traf£c synthesized with our model closely matches the original data. We extend this approach to a general model involving shot noise and show it is asymptotically consistent with more common fractal models used in data networks. Finally, we show that this model extends to the wide area network applications without alteration and it predicts smoothing of wide area network traf£c pro£le due to spatial aggregation, which we observe experimentally by synthetically creating large aggregate TCP load.

Tools for parallel systems today range from specification over debugging to performance analysis and more. Typ- ically, they help the programmers of parallel algorithms from the early development stages to a certain level of pro- gram optimization. However, in HPC ( High Performance Computing) today the end-user of massively parallel CFD (ComputationalFluid Dynamics)-programs has little or no support in his

The centralized thin client computing environment offers a solution to the vulnerability of desktops to viruses, trojan horses and worms. It also releases the user from regular software and hardware updates. One of the major barriers for the proliferation of thin clients in public wide-area networks is the hampering presentation of multimedia applications. While the existing remote display protocols offer a good user experience for office applications, most protocols cannot deal with swift display updates, like video playback, or hardware-accelerated 3D-graphics as in games. In this paper, a wide range of wellknown and widely used thin client protocols are tested in both low-motion and high-motion scenarios. It is shown that additional functionality is required to offer a satisfying multimedia experience.

Resumen-En muchos países latinoamericanos los costes de los enlaces de datos de media distancia provistos por las empresas de telecomunicaciones dentro de unárea metropolitana, son elevados. Una solución para abaratar los costes es utilizar enlaces inalámbricos de "spread spectrum", con antenas direccionales de ganancia entre 15 y 25 db, colocadas en mástiles en el exterior de los edificios. Con esta disposición de los equipos, se puede cubrir todo elárea metropolitana, requiriéndose en muchos casos múltiples saltos, para llegar al lugar de destino. Sin embargo la norma IEEE 802.11 no ha sido diseñada para trabajar en estas condiciones, teniendo bajo rendimiento en la capa de transporte TCP, cuando existen múltiples saltos. Este hecho se ve agravado cuando además existen ramificaciones en estos saltos. En el presente trabajo se ha analizado esta situación, realizando simulaciones y proponiendo soluciones novedosas, con el fin de mejorar el rendimiento de este tipo de redes.