Average Network Load Research Articles

QoE-Aware Efficient Content Distribution Scheme For Satellite-Terrestrial Networks

The satellite-terrestrial networks (STN) utilize the spacious coverage and low transmission latency of the Low Earth Orbit (LEO) constellation to transfer requested content for subscribers especially in remote areas. With the development of storage and computing capacity of satellite onboard equipment, it is considered promising to leverage in-network caching technology on STN to improve content distribution efficiency. However, traditional caching and distribution schemes are not suitable in STN, considering dynamic satellite propagation links and time-varying topology. More specifically, the unevenness of user distribution heightens difficulties for assurance of user quality of experience. To address these problems, we first propose a density-based network division algorithm. The STN is divided into a series of blocks with different sizes to amortize the data delivery costs. To deploy the caching satellites, we analyze the link connectivity and propose an approximate minimum coverage vertex set algorithm. Then, a novel cache node selection algorithm is designed for optimal subscriber matching. On the basis of time-varying network model, the STN cache content updating mechanism is derived to enable a stable and sustainable quality of user experience. The simulation results demonstrate that the proposed user-oriented STN content distribution scheme can obviously reduce the average propagation delay and network load under different network conditions and has better stability and self-adaptability under continuous time variation.

Decentralized and Lightweight Approach to Detect Eclipse Attacks on Proof of Work Blockchains

Clients of permissionless blockchain systems, like Bitcoin, rely on an underlying peer-to-peer network to send and receive transactions. It is critical that a client is connected to at least one honest peer, as otherwise the client can be convinced to accept a maliciously forked view of the blockchain. In such an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eclipse attack</i> , the client is unable to reliably distinguish the canonical view of the blockchain from the view provided by the attacker. The consequences of this can be catastrophic if the client makes business decisions based on a distorted view of the blockchain transactions. In this paper, we investigate the design space and propose two approaches for Bitcoin clients to detect whether an eclipse attack against them is ongoing. Each approach chooses a different trade-off between average attack detection time and network load. The first scheme is based on the detection of suspicious block timestamps. The second scheme allows blockchain clients to utilize their natural connections to the Internet (i.e., standard Web activity) to gossip about their blockchain views with contacted servers and their other clients. Our proposals improve upon previously proposed eclipse attack countermeasures without introducing any dedicated infrastructure or changes to the Bitcoin protocol and network, and we discuss an implementation. We demonstrate the effectiveness of the gossip-based schemes through rigorous analysis using original Internet traffic traces and real-world deployment. The results indicate that our protocol incurs a negligible overhead and detects eclipse attacks rapidly with high probability, and is well-suited for practical deployment.

Cluster‐Based Cooperative Cache Deployment and Coded Delivery Strategy in C‐V2X Networks

Cellular vehicle‐to‐everything‐ (C‐V2X‐) based communications can support various content‐oriented applications and have gained significant progress in recent years. However, the limited backhaul bandwidth and dynamic topology make it difficult to obtain the multimedia service with high‐reliability and low‐latency communication in C‐V2X networks, which may degrade the quality of experience (QoE). In this paper, we propose a novel cluster‐based cooperative cache deployment and coded delivery strategy for C‐V2X networks to improve the cache hit ratio and response time, reduce the request‐response delay, and improve the bandwidth efficiency. To begin with, we design an effective vehicle cluster method. Based on the constructed cluster, we propose a two‐level cooperative cache deployment approach to cache the frequently requested files on the edge nodes, LTE evolved NodeB (eNodeB) and cluster head (CH), to maximize the overall cache hit ratio. Furthermore, we propose an effective coded delivery strategy to minimize the network load and the ratio of redundant files. Simulation results demonstrate that our proposed method can effectively reduce the average response delay and network load and improve both the hit ratio and the ratio of redundant files.

A Testbed for Evaluating Video Streaming Services in LTE

With the deployment of the first commercial long term evolution (LTE) networks, mobile operators need to understand how quality of service (QoS) network indicators and codec parameters affect subjective quality in video streaming services as perceived by customers. In this paper, the development of a testbed for evaluating the quality of experience (QoE) of 3D video streaming service over LTE is described. The proposed system consists of three elements: a streaming server, an internet protocol-level mobile network emulator, based on NetEm tool, and a streaming client. The main contribution of this testbed is the modification of NetEm code to model the impact of time correlation between packet arrivals on the packet delay in a video stream. In the testbed, different network conditions are configured by setting network emulator parameters based on the results obtained by a system-level LTE simulator. Results show how average network load and user position inside a cell have a strong impact on the QoS and QoE perceived by the end video user.

Mobile Ad Hoc Networks in Presence of Black Hole Attack

This paper analyses three performance metrics namely average throughput, average network load and average video conferencing packet end-to-end delays under the influence of black hole attack in a Mobile Ad Hoc Network, using the ad hoc on-demand distance vector routing protocol. The simulation was carried out on Riverbed Modeler Academic Edition software. Simulation results show that the average throughput, average network load and average video conferencing packet end-to-end delay decreases as the number of black hole attack nodes is increased. Also, the effects of the influence of black hole attack nodes tend to decrease due to mobility of the nodes. It was observed that when the destination nodes move closer to the source nodes and get in to the latter’s transmission range, the effects of the black hole attack is greatly minimized.

Bridging the gap between peak and average loads on science networks

Backbone networks are typically overprovisioned in order to support peak loads. Research and education networks (RENs), for example, are often designed to operate at 20–30% of capacity. Thus, Internet2 upgrades its backbone interconnects when the weekly 95th-percentile load is reliably above 30% of link capacity, and analysis of ESnet traffic between major laboratories shows a substantial gap between peak and average utilization. As science data volumes increase exponentially, it is unclear whether this overprovisioning trend can continue into the future. Even if overprovisioning is possible, it may not be the most cost-effective (and desirable) approach going forward. Under the current mode of free access to RENs, traffic at peak load may include both flows that need to be transferred in near-real time–for example, for computation and instrument monitoring and steering–and flows that are less time-critical, for example, archival and storage replication operations. Thus, peak load does not necessarily indicate the capacity that is absolutely required at that moment. We thus examine how data transfers are impacted when the average network load is increased while the network capacity is kept at the current levels. We also classify data transfers into on-demand (time-critical) and best-effort (less time-critical) and study the impact on both classes for different proportions of both the number of on-demand transfers and amount of bandwidth allocated for on-demand transfers. For our study, we use real transfer logs from production GridFTP servers to do simulation-based experiments as well as real experiments on a testbed. We find that when the transfer load is doubled and the network capacity is fixed at the current level, the gap between peak and average throughput decreases by an average of 18% in the simulation experiments and 16% in the testbed experiments, and the average slowdown experienced by the data transfers is under 1.5×. Furthermore, when transfers are classified as on-demand or best-effort, on-demand transfers experience almost no slowdown and the mean slowdown experienced by best-effort transfers is under 2× in the simulation experiments and under 1.2× in the testbed experiments.

Load Balancing Algorithm of Switched Dynamic Iteration

In order to reduce business latency and packet loss rate, to improve the throughput of integration of heteroge- neous wireless network, to achieve load diversification and to improve end quality of service, while there are many prob- lems on the dropout rate of the traditional load balancing algorithm in processing throughput, delay and business, there- fore, gateway load balancing algorithm is proposed in this paper. All terminals in the access network can reflect the effec- tiveness of the average network load level of the network; this algorithm will gain weight of the load in the network of small business terminal to switch to the network load which is light. First, it defines the heterogeneous networks and net- work terminal payoff function utility functions which are used to characterize the experience and network QOS terminal load situation, and then presents the specific processes of the gateway load balancing algorithm. Finally, switching deci- sional load balancing algorithm, proposed by Yan X, etc. is compared with simulation experiments and it shows that: the proposed gateway load balancing algorithm has strong robustness to achieve network load balancing and to achieve a bal- anced use of network resource.

Investigating on Mobile Ad-Hoc Network to Transfer FTP Application

Mobile Ad-hoc Network (MANET) is the collection of mobile nodes without requiring of any infrastructure. Mobile nodes in MANET are operating as a router and MANET network topology can change quickly. Due to nodes in the network are mobile and thus can move randomly and organize arbitrarily regardless of the directions that generate great complexity in routing traffic from source to destination. To communicate with other nodes MANET nodes contain multiple applications and it needs the different level of data traffic. While data communicate different routing protocols require whereas every node must act as a router. Nowadays, different routing protocols have available for MANET. MANET protocols designed and implemented at the network layer have vital roles that affect the application running at the application layer. In this paper, the performance of On Demand Distance Vector (AODV), Dynamic Source Routing (DSR) and Geographic Routing Protocol (GRP) will be evaluated. The main purpose of this research is to analyze the performance of MANET routing protocols to identify “Which routing protocol has ability to provide the best performance to transfer FTP Application in high mobility case under low, medium and high density scenario?”. The performance analyze with respect to Average End-to-End Delay, Media Access Delay, Network Load, Retransmission Attempt and Throughput. All simulations have been done using OPNET. On the basis of results show that the GRP gives better performance in End-to-End Delay, Media Access Delay, and Retransmission Attempt when varying network size and provide the best Throughput in small and medium network size. Simulation results verify that AODV gives better Throughput in a large network and lower Network Load in small and medium network size compared to GRP. DSR produces low Average Network load as compared to other protocols. The overall study of the FTP application shows that the performance of theses routing protocols differences by varying number of nodes and node speed. This paper results will produce enough information to identify the best routing protocol for MANET to transfer FTP application.

An adaptive routing optimization and energy-balancing algorithm in ZigBee hierarchical networks

ZigBee hierarchical tree routing protocol (HRP; ZigBee Alliance, San Ramon, CA, USA) provides a simple but reliable topology. However, the transmission routes are not always efficient, and the links are fixed after they were determined during the network initialization. In this paper, we propose an adaptive routing optimization and energy-balancing algorithm in ZigBee hierarchical networks. In our routing algorithm, the parent node could adaptively maintain its child's links for lower network load, and all the information needed can be obtained from a neighbour table to avoid introducing extra communication overhead. Such algorithm makes ZigBee's hierarchical topology to adaptively maintain and optimize the routing paths during its lifetime, and an address reassignment mechanism is also introduced to ensure that our algorithm follows ZigBee specification. In addition, an energy-balancing algorithm is also proposed to reduce the power cost of low-battery device. Simulation results show that our routing scheme has better performance with lower average transmission hops and network load, and our energy-balancing algorithm could reduce the power consumption of low-battery device.

On the effect of sudden data bursts in the upstream channel of Ethernet PONs employing IPACT under the gated-service discipline

The Interleaved Polling with Adapted Cycle Times (IPACT) algorithm for dynamic bandwidth allocation proposed for Ethernet Passive Optical Networks (EPONs) has been deeply analysed in the literature under Poisson traffic. However, the case when ONUs suddenly offer bursty traffic in the upstream channel of a PON has not been considered in such detail.This paper studies the performance behaviour of the upstream channel of EPONs employing IPACT with the gated-service disciple, under Poisson traffic together with sudden bursts. We show that one burst arrival produces a peak in the average transmission window of every ONU, lasting its effects for several cycle times, depending on the burst size and the average network load. Such a burst has a direct impact on the delay experienced by the packets of other ONUs. This is mathematically modelled using a modification of the formerly studied M/G/1 queue with vacations and validated with simulation.

Dissemination of information in complex networks with congestion

We address the problem of message transfer in complex networks with congestion. We propose a new strategy aimed at improving routing efficiency. Such a strategy, contrary to the shortest available path length from a given source to its destination (perhaps the most widely analyzed routing strategy), takes into account the congestion of nodes and can be deployed, with a minimal overhead, on top of it. Our results show that, by distributing more homogeneously the congestion of nodes, it significantly reduces the average network load as well as the collapse point.

Quantitative assessment of user-level QoS and its mapping

This paper proposes a scheme for quantitative assessment of user-level (or perceptual) quality of service (QoS) for audio-video transmission by means of two psychometric methods: the method of paired comparisons and the law of comparative judgment. Moreover, we discuss QoS mapping from application-level QoS to user-level QoS by principal component analysis and multiple regression analysis. In the assessment, we simulate the transmission of an audio-video stream over a loaded network. In order to investigate the effect of the contents on QoS mapping, we treat two types of audio-video streams. By experiment, we demonstrate that our scheme can construct an interval scale as the user-level QoS parameter for each stream and represent it as a function of two application-level QoS parameters with high accuracy. We notice that the multiple regression line depends on the contents. We also propose the concept of control gain by media synchronization, which indicates how much media synchronization control subjectively lightens the average network load.

Dynamic retransmission control for reliable mobile multicast

Most existing multicast protocols adopt a static retransmission scheme (unicast or multicast) to retransmit lost packets. In the mobile multicast environment, static multicast retransmission mode may lead to congestion in the receivers' wireless interfaces, while static unicast mode may result in great network load. Both static unicast and multicast retransmission modes will cause a performance loss. This paper logically divides the mobile multicast network into fixed and mobile parts, and focuses on the mobile part. Then this paper analyzes the retransmission costs when multicast or unicast mode is chosen. Two main parameters are used to compare their efficiencies: the average air-interface utilization of each receiver and the average network load. Based on the results of analysis, two new algorithms, called NLPA (Network Load Priority Algorithm) and AUPA (Air-interface Utilization Priority Algorithm) are presented. Finally, simulation results conclude that, with proper parameters, both NLPA and AUPA can dynamically alternate between unicast and multicast retransmission modes according to the conditions of network and receiver, and avoid congestion in receivers' wireless interfaces as well as great network load, with a better use of network and terminal resources.

Using multirail networks in high‐performance clusters

AbstractUsing multiple independent networks (also known as rails) is an emerging technique which is being used to overcome bandwidth limitations and enhance fault tolerance of current high‐performance parallel computers. In this paper, we present and analyze various algorithms to allocate multiple communication rails, including static and dynamic allocation schemes. An analytical lower bound on the number of rails required for static rail allocation is shown. We also present an extensive experimental comparison of the behavior of various algorithms in terms of bandwidth and latency. We show that striping messages over multiple rails can substantially reduce network latency, depending on average message size, network load and allocation scheme. The methods compared include a static rail allocation, a basic round‐robin rail allocation, a local‐dynamic allocation based on local knowledge and a dynamic rail allocation that reserves both communication endpoints of a message before sending it. The last method is shown to perform better than the others at higher loads: up to 49% better than local‐knowledge allocation and 37% better than the round‐robin allocation. This allocation scheme also shows lower latency and it saturates at higher loads (for long enough messages). Most importantly, this proposed allocation scheme scales well with the number of rails and message size. In addition we propose a hybrid algorithm that combines the benefits of the local‐dynamic allocation for short messages with those of the dynamic algorithm for large messages. Copyright © 2003 John Wiley &amp; Sons, Ltd.

A carrier sensed multiple access protocol high data rate ring networks

This paper presents a significant extension of the CSMA network access protocol. The protocol is based on the facts that, at high data rates, networks can contain multiple messages simultaneously over their span, and that in a ring, nodes needs only to detect the presence of a message arriving from the immediate up stream neighbor. When an incoming signal is detected, the node truncates the message it is presently sending instead of aborting it. The system has been named Carrier Sensed Multiple Access Ring Network, CSMA/RN.Analytical studies using three performance factors, wait or access time, service time and response or end-to-end travel time are presented. The service time is basically a function of the network rate; it changes by a factor of 4 between no load and full load. Wait time, which is zero for no load, remains small for load factors up to 70% of full load. Response time, which adds travel time while on the network to wait and service time, is mainly a function of network length, especially for longer distance networks.Simulation results are shown for CSMA/RN where messages are removed at the destination. Destination removal on an average increases network load capacity by a factor of 2, i.e., a 1 Gbps network can handle a 2 Gbps load. A wide range of local and metropolitan area network parameters including variations in message size, network length and node count are studied. In all cases performance is excellent, and message fracture usually remains less than a factor of 4. Throughput, even at overload conditions, remains high for the protocol. The nominal network rate is 1 Gbps; however, performance remains good for data rates as low as 200 Mbps. Finally, a scaling factor based upon the ratio of message to network length demonstrates that the results of this paper, and hence, the CSMA/RN protocol, are applicable to wide area networks.