Network Nodes (network + node)

Distribution by Scientific Domains

Selected Abstracts

An exact performance model for the reserve channels CAC strategy at a bufferless network node

Dervis Z. Deniz
Abstract The reserve channels call admission control (CAC) strategy in which the total number of channels available at the node is divided into active and reserve channels is analysed. Two types of customers are assumed to exist: the narrowband type requiring bandwidth bn=1 channel and wideband type requiring bw,1 channels. The active channels are shared by all customer types while the reserve channels are allocated by a predefined rule. An exact matrix algorithmic solution technique is proposed that extends the previous results to the case of calls requiring bw,1 channels. Using the developed solution technique, the number of equations to be solved is decreased which reduces the solution time by more than half. The technique is applied to a sample case and performance results in terms of blocking probabilities for both types of calls as well as the mean server utilization are obtained. Copyright 2003 John Wiley & Sons, Ltd. [source]

On QoS mechanism profiling in MPLS-TP transport networks

Christian Addeo
In the context of packet management in optical transport networks, quality of service (QoS) is playing an important role to achieve the right levels of bandwidth, latency, and general treatment for the different services carried over the network. The scope of this paper is to describe quality of service functionalities in the context of a packet transport network. This paper refers to the definition and implementation of the quality of service model in a packet transport network node, describing how this information is carried over a packet transport network. The Alcatel-Lucent 1850 Transport Service Switch (TSS) platform serves as our reference point for a packet transport node. We also include a description of classification, policing, marking, and, in particular, hierarchical scheduling and shaping. 2010 Alcatel-Lucent. [source]

On the efficiency of PGPS-based packet and cell switching technologies for traffic with guaranteed delay

Fulvio Risso
Circuit switching, suited to providing real-time services due to the low and fixed switching delay, is not cost effective for building integrated services networks because it is based on static allocation of resources which is not efficient with bursty data traffic. Moreover it cannot handle flows that are not integer multiple of 64,Kb/s, preventing the usage of low bit rate codecs. This work explores the most suitable alternatives to the circuit switching technology (i.e. packet/cell switching) from the efficiency point of view, assuming that a PGPS scheduler is deployed in the network nodes. The paper defines an index to measure the efficiency of packet telephony, i.e. the volume of real-time traffic with deterministically guaranteed quality plus the amount of data carried related to the amount of network resources used. Furthermore it determines the maximum efficiency obtainable by packet networks, compares different network technologies and explores the problems of the deploying of low bit-rate codecs. Copyright 2003 AEI. [source]

Adaptive state- dependent importance sampling simulation of markovian queueing networks

Pieter-Tjerk De Boer
In this paper, a method is presented for the efficient estimation of rare-event (buffer overflow) probabilities in queueing networks using importance sampling. Unlike previously proposed change of measures, the one used here is not static, i.e., it depends on the buffer contents at each of the network nodes. The ,optimal' state-dependent change of measure is determined adaptively during the simulation, using the cross-entropy method. The adaptive state-dependent importance sampling algorithm proposed in this paper yields asymptotically efficient simulation of models for which it is shown (formally or otherwise) that no effective static change of measure exists. Simulation results for queueing models of communication systems are presented to demonstrate the effectiveness of the method. [source]

Efficient packet classification on network processors

Koert Vlaeminck
Abstract Always-on networking and a growing interest in multimedia- and conversational-IP services offer an opportunity to network providers to participate in the service layer, if they increase functional intelligence in their networks. An important prerequisite to providing advanced services in IP access networks is the availability of a high-speed packet classification module in the network nodes, necessary for supporting any IP service imaginable. Often, access nodes are installed in remote offices, where they terminate a large number of subscriber lines. As such, technology adding processing power in this environment should be energy-efficient, whilst maintaining the flexibility to cope with changing service requirements. Network processor units (NPUs) are designed to overcome these operational restrictions, and in this context this paper investigates their suitability for wireline and robust packet classification in a firewalling application. State-of-the-art packet classification algorithms are examined, whereafter the performance and memory requirements are compared for a Binary Decision Diagram (BDD) and sequential search approach. Several space optimizations for implementing BDD classifiers on NPU hardware are discussed and it is shown that the optimized BDD classifier is able to operate at gigabit wirespeed, independent of the ruleset size, which is a major advantage over a sequential search classifier. Copyright 2007 John Wiley & Sons, Ltd. [source]

Adaptive zone routing protocol for ad hoc network nodes with non-uniform mobilities

Xiaofeng Zhang
Abstract In recent years, a variety of new routing protocols for mobile ad hoc wireless NETworks (MANETs) have been developed. Performance evaluation and comparison of many of these routing protocols have been performed using detailed simulation models. Zone routing protocol (ZRP) is one of these routing protocols, which is a hybrid routing protocol that proactively maintains routing information for a local neighbourhood (routing zone), while reactively acquiring routes to destinations beyond the routing zone. The studies on ZRP have assumed homogeneous scenarios where all mobile nodes have uniform mobility and are statistically identical, lacking the studies on heterogeneous scenarios where mobile nodes move with non-uniform mobilities in the same network. In this paper, we study the performance of ZRP in such scenarios. We propose an efficient scheme for ZRP to adapt to the non-uniform mobilities scenario and study its performance for different mobility scenarios, network loads and network sizes. Copyright 2003 John Wiley & Sons, Ltd. [source]

The common patterns of nature

Abstract We typically observe large-scale outcomes that arise from the interactions of many hidden, small-scale processes. Examples include age of disease onset, rates of amino acid substitutions and composition of ecological communities. The macroscopic patterns in each problem often vary around a characteristic shape that can be generated by neutral processes. A neutral generative model assumes that each microscopic process follows unbiased or random stochastic fluctuations: random connections of network nodes; amino acid substitutions with no effect on fitness; species that arise or disappear from communities randomly. These neutral generative models often match common patterns of nature. In this paper, I present the theoretical background by which we can understand why these neutral generative models are so successful. I show where the classic patterns come from, such as the Poisson pattern, the normal or Gaussian pattern and many others. Each classic pattern was often discovered by a simple neutral generative model. The neutral patterns share a special characteristic: they describe the patterns of nature that follow from simple constraints on information. For example, any aggregation of processes that preserves information only about the mean and variance attracts to the Gaussian pattern; any aggregation that preserves information only about the mean attracts to the exponential pattern; any aggregation that preserves information only about the geometric mean attracts to the power law pattern. I present a simple and consistent informational framework of the common patterns of nature based on the method of maximum entropy. This framework shows that each neutral generative model is a special case that helps to discover a particular set of informational constraints; those informational constraints define a much wider domain of non-neutral generative processes that attract to the same neutral pattern. [source]

An overview of the heterogeneous telescope network system: Concept, scalability and operation

R.R. White
Abstract In the coming decade there will be an avalanche of data streams devoted to astronomical exploration opening new windows of scientific discovery. The shear volume of data and the diversity of event types (Kantor 2006; Kaiser 2004; Vestrand & Theiler & Wozniak 2004) will necessitate; the move to a common language for the communication of event data, and enabling telescope systems with the ability to not just simply respond, but to act independently in order to take full advantage of available resources in a timely manner. Developed over the past three years, the Virtual Observatory Event (VOEvent) provides the best format for carrying these diverse event messages (White et al. 2006a; Seaman & Warner 2006). However, in order for the telescopes to be able to act independently, a system of interoperable network nodes must be in place, that will allow the astronomical assets to not only issue event notifications, but to coordinate and request specific observations. The Heterogeneous Telescope Network (HTN) is a network architecture that can achieve the goals set forth and provide a scalable design to match both fully autonomous and manual telescope system needs (Allan et al. 2006a;White et al. 2006b; Hessman 2006b). In this paper we will show the design concept of this meta-network and nodes, their scalable architecture and complexity, and how this concept can meet the needs of institutions in the near future. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Ethernet aggregation and core network models for effcient and reliable IPTV services

Christian Hermsmeyer
With the growing interest on wireline network architectures for residential triple-play and business Ethernet services there is a renewed demand for efficient and reliable packet-based transport capabilities between the content providers and the end users. Voice and data traffic carried over a variety of access technologies is collected via technology-specific access networks (e.g., digital subscriber line [xDSL], passive optical network [xPON], and wireless fidelity [WiFi]). Metro and core networks need to aggregate the various user flows from different access network nodes and provide scalable and cost-effective distribution of various flow types (e.g., Internet access, voice, video on demand, and broadcast TV services) to the relevant service access points. Varying quality of service and resiliency requirements for these services are being reflected in a new breed of converged Ethernet and optical network elements with capabilities to interwork the bearer-planes of these two networking technologies seamlessly. Network elements based on Ethernet/Optical converged technology are able to select the most fitting mechanisms from each networking technology to meet the transport requirements for each individual service demand better while providing significantly enhanced implementation and operational efficiencies. This paper discusses network architecture models and network elements addressing these goals. 2007 Alcatel-Lucent. [source]

Role of Network Branching in Eliciting Differential Short-Term Signaling Responses in the Hypersensitive Epidermal Growth Factor Receptor Mutants Implicated in Lung Cancer

Jeremy Purvis
We study the effects of EGFR inhibition in wild-type and mutant cell lines upon tyrosine kinase inhibitor TKI treatment through a systems level deterministic and spatially homogeneous model to help characterize the hypersensitive response of the cancer cell lines harboring constitutively active mutant kinases to inhibitor treatment. By introducing a molecularly resolved branched network systems model (the molecular resolution is introduced for EGFR reactions and interactions in order to distinguish differences in activation between wild-type and mutants), we are able to quantify differences in (1) short-term signaling in downstream ERK and Akt activation, (2) the changes in the cellular inhibition EC50 associated with receptor phosphorylation (i.e., 50% inhibition of receptor phosphorylation in the cellular context), and (3) EC50 for the inhibition of activated downstream markers ERK-(p) and Akt-(p), where (p) denotes phosphorylated, upon treatment with the inhibitors in cell lines carrying both wild-type and mutant forms of the receptor. Using the branched signaling model, we illustrate a possible mechanism for preferential Akt activation in the cell lines harboring the oncogenic mutants of EGFR implicated in non-small-cell lung cancer and the enhanced efficacy of the inhibitor erlotinib especially in ablating the cellular Akt-(p) response. Using a simple phenomenological model to describe the effect of Akt activation on cellular decisions, we discuss how this preferential Akt activation is conducive to cellular oncogene addiction and how its disruption can lead to dramatic apoptotic response and hence remarkable inhibitor efficacies. We also identify key network nodes of our branched signaling model through sensitivity analysis as those rendering the network hypersensitive to enhanced ERK-(p) and Akt-(p); intriguingly, the identified nodes have a strong correlation with species implicated in oncogenic transformations in human cancers as well as in drug resistance mechanisms identified for the inhibitors in non-small-cell lung cancer therapy. [source]

Clustering-based scheduling: A new class of scheduling algorithms for single-hop lightwave networks

Sophia G. Petridou
Abstract In wavelength division multiplexing (WDM) star networks, the construction of the transmission schedule is a key issue, which essentially affects the network performance. Up to now, classic scheduling techniques consider the nodes' requests in a sequential service order. However, these approaches are static and do not take into account the individual traffic pattern of each node. Owing to this major drawback, they suffer from low performance, especially when operating under asymmetric traffic. In this paper, a new class of scheduling algorithms for WDM star networks, which is based on the use of clustering techniques, is introduced. According to the proposed Clustering-Based Scheduling Algorithm (CBSA), the network's nodes are organized into clusters, based on the number of their requests per channel. Then, their transmission priority is defined beginning from the nodes belonging to clusters with higher demands and ending to the nodes of clusters with fewer requests. The main objective of the proposed scheme is to minimize the length of the schedule by rearranging the nodes' service order. Furthermore, the proposed CBSA scheme adopts a prediction mechanism to minimize the computational complexity of the scheduling algorithm. Extensive simulation results are presented, which clearly indicate that the proposed approach leads to a significantly higher throughput-delay performance when compared with conventional scheduling algorithms. We believe that the proposed clustering-based approach can be the base of a new generation of high-performance scheduling algorithms for WDM star networks. Copyright 2008 John Wiley & Sons, Ltd. [source]