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Data center networks (DCNs) are the backbone of many cloud and Internet services. They are vulnerable to link failures, that occur on a daily basis, with a high frequency. Service disruption due to link failure may incur financial losses, compliance breaches and reputation damage. Performance metrics such as packet loss and routing flaps are negatively affected by these failure events. We propose a new Bayesian learning approach towards adaptive path allocation that aims to improve DCN performance by reducing both packet loss and routing flaps ratios. The proposed approach incorporates historical information about link failure and usage probabilities into its allocation procedure, and updates this information on-the-fly during DCN operational time. We evaluate the proposed framework using an experimental platform built with the POX controller and the Mininet emulator. Compared with a benchmark shortest path algorithm, the results show that the proposed methods perform better in terms of reducing the packet loss and routing flaps.

An advanced metering infrastructure (AMI) consists of a meter data management system, a concentrator, and a meter. Each component can communicate with all other components, through either wired or wireless connections. In an AMI local area networks, various protocols, such as Zigbee, WiFi, and power-line communication, have the potential to be used in AMI communication. Of these protocols, Zigbee offers self-constructing networks, low costs, and superior safety levels. Zigbee is adopted as the LAN communication protocol because of these advantages in this study. In a LAN, a concentrator may encounter many emergent situations, any of which might cause the concentrator to lose its network connection function. Consequently, additional time is required for network construction, which tends to reduce the reliability of smart grids with LANs of this type. To solve these issues, this paper proposes the fast join process (FJP) and enhanced FJP to shorten the time of Zigbee network construction. The strategy employed in this paper is to let every meter join a specified concentrator. The proposed FJP does not scan unnecessary channels. By simplifying association message exchange, we further propose a new method called the enhanced FJP. By using these methods, not only can message flow be managed easily, but the time of network construction can also be improved.

In recent years, the emerging paradigm of software-defined networking has become a hot and thriving topic in both the industrial and academic sectors. Software-defined networking offers numerous benefits against legacy networking systems by simplifying the process of network management through reducing the cost of network configurations. Currently, data plane fault management is limited to two mechanisms: proactive and reactive. These fault management and recovery techniques are activated only after a failure occurrence and hence packet loss is highly likely to occur. This is due to convergence time where new network paths will need to be allocated in order to forward the affected traffic rather than drop it. Such convergence leads to temporary service disruption and unavailability. Practically, not only the speed of recovery mechanisms affects the convergence, but also the delay caused by the process of failure detection. In this paper, we define a new approach for data plane fault management in software-defined networks where the goal is to eliminate the convergence process altogether rather than accelerate the failure detection and recovery. We propose a new framework, called Smart Routing, which allows the network controller to receive forewarning signs on failures and hence avoid risky paths before the failure incidents occur. The proposed approach aims to decrease service disruption, which in turn increases network service availability. We validate our framework through a set of experiments that demonstrate how the underlying model runs and its impact on improving service availability. We take as example of the applicability of the new framework three types of topologies covering real and simulated networks.

Recently, increasing attention has been paid to the study of applying software defined networks to improve video transmission. Compared with the existing studies which focus on a wired network, this study proposed a multi-path transmission mechanism for improving the performance of transmitting videos from a wired network to a wireless one in a software defined network environment. In the proposed mechanism, a mobile host could apply network bonding to integrate several physical or virtual wireless network modules, each of which was connected to a different access point, into a combined device. Thus, multiple wireless links of the mobile host could be established and hence multiple transmission paths from the video source in the wired network to the mobile host were derived. In addition, different amount of video packets were allocated onto different transmission paths so as to maximize the performance of the multi-path transmission. According to the results of our experiments, the proposed mechanism can enhance the performance of transmission in terms of Peak Signal to Noise Ratio (PSNR).

The increasing complexity of modern day networked applications and the massive demand on the Internet resources has reignited interest and concern in the underlying networking infrastructures and their ability to cope with such complexity and adapt to the demands of the business applications, particularly where such applications require a high degree of robustness and reliability. As a result, software-defined networking has emerged as a promising approach to the definition of network architectures that could carry a high degree of adaptability and robustness reminiscent of the future Internet. Fault tolerance and network updates are considered two of the current research challenges that hamper the growth of software-defined networking in this area. Therefore, this paper represents a step toward tackling these two issues in the context of single link failures. Our main contribution lies in the definition of new algorithms that aim to enhance the problem of finding alternative paths in large-scale networks with minimal cost and time-to-update factors. The new solution aims at increasing the efficiency of flow operation reduction during link failures. We evaluate our framework and show how its implementation results in improved efficiency.

Packets that traverse more hops to the destination will get lower throughput and result in the inter-flow fairness issue.We propose a virtual queue management scheme that does not require the modification of any communication protocol.According to the number of flows, our scheme adjusts the parameters to achieve each flow's fair sharing of channel resource.Our proposed scheme can mitigate the inter-flow fairness problem and effectively improves the quality of video transmission. Due to intra-flow and inter-flow interference problems, the throughput performance decreases dramatically in a multi-hop wireless network. These two kinds of bandwidth unfair sharing problems could cause serious collisions and congestion, hence affecting the performance of multi-hop wireless networks. That is to say, data packets that need to traverse more hops to arrive at the destination will get lower throughput and result in the inter-flow fairness problem. Furthermore, the quality of video transmission is especially poor in traditional multi-hop wireless network environments. Therefore, in this paper, we propose a virtual queue management scheme that does not require the modification of any communication protocol. According to the number of flows, it adjusts the queue management scheme to achieve each flow's fair sharing of channel resource. It also improves the quality of video transmission. Through NS2 simulations, the results show that our proposed scheme can mitigate the inter-flow fairness problem and effectively improves the quality of video transmission. Display Omitted

Being increasingly dense and mature in layout, Internet has become an infrastructure for a state. The traditional single server can no longer bear the network traffic in rapid growth. For example, once the booking service for concert tickets is made available to the public, we are always prompted when clicking into the booking system that the server is busy. And when the system is finally restored normal, the tickets have been sold out. The load issue puzzling the ticket system also occurs in the transportation section every time when a long holiday is coming. Even though the system is updated on a yearly basis, net- work congestion still happens frequently. Therefore, there is still great space for the development of the ways and mechanisms of load balance in traditional multi-servers. Evaluation of the mech- anism and efficacy of load balance through P4Switch is proposed in this paper in the hope to achieve more efficient server load balance.

A following vehicle can significantly reduce fatigue in people who want a hands-free walk. The vehicle follows a person and carries heavy things for him/her so that the person can walk in comfort without the burden of carrying the heavy things. Robot Operating System, ROS, is a software framework which is widely adopted for the development of automated guided vehicles, AGVs. Following vehicles and AGVs share many similarities. Both of them can move goods and autonomously plan their paths without manual intervention. Thus, this paper proposes a following vehicle prototype utilizing ROS. In a ROS robot, we integrate a program to measure the power present in received radio signals from a radio transmitter attached to the person it follows. The measurements indicate the approximate distance between the following vehicle and its user. The vehicle, then, moves toward the user based on the estimated distance. The experiment results prove that the proposed prototype can correctly follow the movement of its user in a linear direction with an obvious but acceptable delay.

With the continuous development of network technologies, a growing number of devices are connected to the Internet, and the reliability, availability and data transmission performance of the network have become increasingly important. Software-Defined Network (SDN) breaks the closed system of the traditional network that is formed by the tight coupling among network hardware, operating system and applications, enabling the network to be elastically adjusted based on different environments and needs. In this study, a mechanism for improving the reliability, availability and transmission performance of network was built in the SDN environment. In the proposed approach, the stochastic mechanism was applied to distribute traffic and the OpenFlow Group Tables were used to enable the automatic switch to the standby Action Bucket for uninterrupted service in case of any fault of the link so as to improve the fault tolerance and reliability of network. Experiments demonstrated that the proposed mechanism can transmit data faster and achieve more reliable network services.

In this study, we develop a hierarchical packet pre-dropping (HPPD) approach that exploits different methods to process intra-coded (I)/predictive-coded (P)/bidirectionally predictive-coded (B) video frame packets to improve the video transmission quality in heavily loaded IEEE 802.11e wireless local area networks (WLANs). It is not easy to transmit packets in WLANs with a heavy traffic load. Efficient transmission of video packets is important for improving the quality of video transmission. If the network becomes congested, important packets may be dropped. Further, video packets tend to be affected considerably more than data packets. Therefore, controlling the traffic of insignificant packets to avoid the transmission of useless data can improve the quality of video transmission. On the basis of this concept, in this paper, we propose a strategy that is different from the approaches proposed in earlier studies. First, identification of the dependence of video frames in a group of pictures (GOP) can prevent the transmission of useless data. Thus, the transmission channel resources are economized by avoiding the transmission of undecodable video frames. Second, in heavily loaded WLANs, it is not sufficient to utilize the queues to transmit important video frame packets. HPPD adopts the method of an aggressive drop of unimportant packets to retain the transmission channel resources for important video packets. Experiments have demonstrated that in heavily loaded WLANs, the Peak Signal to Noise Ratio (PSNR) for the case when the HPPD mechanism is adopted is better than that when enhanced distributed channel access (EDCA), adaptive mapping, or a novel mapping mechanism is used.

The nodes in wireless sensor networks (WSN) are typically resource constrained so that they can maintain only a few routes. More-capable nodes can insert extra routing information, i.e. source routing header (SRH), into packets to instruct the resource constrained ones to route the packet. A WSN with deeper depth requires longer SRH, thus leaving less space of a packet for the user data. We analyze the relationship between the length of the user data and the maximum depth of a WSN based on RPL and IEEE 802.15.4. The results can guide the application designers and the network administrators in selecting a suitable length of user data to guarantee that the data can be routed to each sensor nodes. Simulation results prove the correctness of our analysis.

IEEE 802.11e has been introduced to support quality of service (QoS) in WLANs by allocating different traffics to four access categories. Cross-layer design is a method to improve the transmission quality of multimedia over wireless networks. However, when the fragmented packets of a single frame are allocated to different AC queues, out-of-order delivery may occur. Then the receiving node requires more buffer space to absorb the out-of-order packets. Therefore, even with a significance classification mechanism, the quality of the video transmission may still be limited due to the occurrence of out-of-order delivery and the transmission of information that becomes useless to the receiver. Therefore, this work developed a novel mapping mechanism (NMM) to improving the quality of MPEG-4 video delivery over IEEE 802.11e networks. The NMM considers the action that was taken on packet of the video frame that had been previously transmitted to resolve the out-of-order delivery by allocating them to the same AC queue as the previously process if possible. Furthermore, the proposed mechanism NMM takes more aggressive scheme to protect more important frame packets from being dropped. In order to evaluate the quality of MPEG-4 video delivery over IEEE 802.11e networks by the proposed mechanism, this work adopted two evaluation metrics, which is called Peak to Signal Noise Ratio (PSNR) and the ratio of frames loss. The simulation results demonstrate that, in terms of both PSNR and the ratio of frames loss, the proposed scheme outperforms exiting schemes such as EDCA (Enhanced Distributed Channel Access) and adaptive mapping.

Wireless networks have a varying channel quality and a limited bandwidth. Therefore, ensuring a satisfactory video quality over wireless networks is extremely challenging. Most existing studies for enhancing the received video quality over wireless networks consider only single-hop transmission environments. Consequently, when applied to multi-hop wireless networks, such as wireless mesh networks, VANETs or wireless sensor networks, the video quality is typically rather poor. Accordingly, this study proposes a cross-layer mechanism for improving the video transmission quality in multi-hop wireless networks. The proposed scheme considers both the video frame type and the output interface queue length at the intermediate nodes while determining the drop probability during the packet forwarding process. Besides, in the event of transmission failures, the number of retransmission attempts is varied adaptively in accordance with the network conditions and the relative priority of the corresponding frame. Furthermore, the forwarding probability at each node is increased in accordance with the number of hops previously traversed by the packet. Thus, the proposed scheme improves video delivery quality by means of providing unequal protection for frames of different importance. The NS2 simulation results show that the average PSNR results obtained with the proposed scheme have significant improvements compared to that obtained with the traditional IEEE 802.11 mechanism, thereby confirming the effectiveness of the proposed scheme.

Software Defined Networking is a new networking paradigm that has emerged recently as a promising solution for tackling the inflexibility of the classical IP networks. The centralized approach of SDN yields a broad area for intelligence to optimise the network at various levels. Fault tolerance is considered one of the most current research challenges that facing the SDN, hence, in this paper we introduce a new method that computes an alternative paths re-actively for centrally controlled networks like SDN. The proposed method aims to reduce the update operation cost that the SDN network controller would spend in order to recover from a single link failure. Through utilising the principle of community detection, we define a new network model for the sake of improving the network's fault tolerance capability. An experimental study is reported showing the performance of the proposed method. Based on the results, some further directions are suggested in the context of machine learning towards achieving further advances in this research area.

Nowadays, the demand for data transmission is ever increasing with the increase of network applications. Therefore, how to enhance the performance of data transmission is an issue worthy of in-depth discussion. The throughput of single-path transmission schemes might be throttled by a congested link of its path. In contrast, multipath transmission schemes can utilize the bandwidth resource of several disjoint paths to increase the throughput. In this paper, we proposed a multipath transmission scheme to equally balance the traffic of a flow over the disjoint paths designated by the Software Defined Network (SDN) controller, which is able to learn the topology of the network and discover multiple transmission paths. Simulations were conducted with Mininet to evaluate our proposed transmission scheme. In comparison with the traditional single-path transmission scheme, which always adopts the shortest path, experimental results show that our proposed scheme achieves a significant improvement on performance in terms of transmission throughput.

Forward error correction (FEC) is a common error control technique to improve the quality of video streaming over lossy channels. To optimize the data recovery performance, frame-level FEC schemes have been proposed for streaming video to maximize playable frame rate (PFR) within transmission rate constraint on a random binary symmetric channel (BSC). However, burst loss is a commonplace in current Internet architecture, and the FEC efficacy c an be degraded since the burst data losses easily exceed the error correction capacity of FEC. Accordingly, an estimated video quality model over burst loss channels is proposed in this paper to evaluate the impact of burst loss for FEC-based video applications. In addition to th e model analysis, the simulation experiments on the NS-2 network simulator are conducted at a given estimate of the packet loss probability and average burst length. The results suggest a useful reference in designing the FEC scheme for video applications, and as the video coding and channel parameters are given, the proposed model can provide the optimal FEC solution to achieve a better reconstructed video quality than the FEC model based on a random BSC channel.

This study proposes an efficient localization scheme in wireless sensor networks. The proposed scheme utilizes mobile anchors and is based on ring overlapping. In a wireless sensor network, the nodes that know their locations are called reference nodes, and the other nodes that are without the knowledge of their locations are called blind nodes. To localize a certain blind node, by comparing the relative RSSI (Received Signal Strength Indicator) values among nodes, mobile beacons are utilized to find out the rings that are centered at a reference node and contain the blind node. These rings are called B-Rings. Since the mobile anchors and the reference nodes know their own locations, the B-Rings can be precisely derived. Moreover, by using multiple mobile beacons, the widths of the B-Rings can be further minimized; and then by overlapping them, the location of the blind nodes can be efficiently estimated. Most existing localization schemes that utilize mobile anchors let the mobile anchors move randomly. In contrast, the proposed scheme provides regular and simple movement mechanisms for the mobile anchors. Thus, the mobile anchors consume less energy than the other schemes, in which the mobile anchors move randomly. Analytical analysis and simulation results show that the proposed localization mechanism can achieve better location accuracy as well as less movement length of the mobile anchor than the other existing related approaches.

According to previous work, the performance of the Distributed Coordination Function (DCF) (i.e., the basic access method of the IEEE 802.11 protocol) is far from optimum due to use of the binary exponential backoff (BEB) scheme as its collision avoidance mechanism. There has been considerable discussion of DCF issues and its performance analysis. However, most schemes assume an ideal channel, which is contrary to realistic wireless environments. In this paper, we present a simple yet pragmatic distributed algorithm, designated the density based access method (DBM), which allows stations to dynamically optimize the network throughput based on run-time measurements of the channel status. Our simulation results demonstrate that the DBM is highly accurate. The performance in terms of throughput and fairness is nearly optimal by use of the proposed scheme.

The Hybrid ARQ (HARQ) mechanism is the well-known error packet recovery solution composed of the Automation Repeat reQuest (ARQ) mechanism and the Forward Error Correction (FEC) mechanism. However, the HARQ mechanism neither retransmits the packet to the receiver in time when the packet cannot be recovered by the FEC scheme nor dynamically adjusts the number of FEC redundant packets according to network conditions. In this paper, the Adaptive Hybrid Error Correction Model (AHECM) is proposed to improve the HARQ mechanism. The AHECM can limit the packet retransmission delay to the most tolerable end-to-end delay. Besides, the AHECM can find the appropriate FEC parameter to avoid network congestion and reduce the number of FEC redundant packets by predicting the effective packet loss rate. Meanwhile, when the end-to-end delay requirement can be met, the AHECM will only retransmit the necessary number of redundant FEC packets to receiver in comparison with legacy HARQ mechanisms. Furthermore, the AHECM can use an Unequal Error Protection to protect important multimedia frames against channel errors of wireless networks. Besides, the AHECM uses the Markov model to estimate the burst bit error condition over wireless networks. The AHECM is evaluated by several metrics such as the effective packet loss rate, the error recovery efficiency, the decodable frame rate, and the peak signal to noise ratio to verify the efficiency in delivering video streaming over wireless networks.

Traditional Forward Error Correction (FEC) mechanisms can be divided into Packet level FEC (PFEC) mechanisms and Byte level FEC (BFEC) mechanisms. The PFEC mechanism of recovering from errors in a source packet requires an entire FEC redundant packet even though the error involves a few bit errors. The recovery capability of the BFEC mechanism is only half of the FEC redundancy. Accordingly, an adaptive Sub-Packet FEC (SPFEC) mechanism is proposed in this paper to improve the quality of video streaming data over wireless networks, simultaneously enhancing the recovery performance and reducing the end-to-end delay jitter. The SPFEC mechanism divides a packet into n sub-packets by means of the concept of a virtual packet. The SPFEC mechanism uses a checksum in each sub-packet to identify the position of the error sub-packet. Simulation experiments show the adaptive SPFEC mechanism achieves high recovery performance and low end-to-end delay jitter. The SPFEC mechanism outperforms traditional FEC mechanism in terms of packet loss rate and video Peak Signal-to-Noise Ratio (PSNR). SPFEC offers an alternative for improved efficiency video streaming that will be of interest to the designers of the next generation environments.

According to the latest version of the IEEE 802.11 standard, the backoff parameters of its collision avoidance mechanism are far from optimal, especially in a heavy load or error-prone WLAN environment. This strategy has a high collision probability and channel utilization is degraded in bursty arrivals or congested scenarios. Besides, the standard backoff mechanism may treat noise corruption as packet collisions. In this paper, we identify the relationship between backoff parameters, contention level, and channel BER in order to propose a simple, but yet well-performing distributed algorithm that allows a station to dynamically adjust its contention window size based on turn-around-time measurement of channel status. In addition to theoretical analysis, simulations are conducted to evaluate its performance. The proposed scheme works very well in providing a substantial performance improvement in heavy loaded and error-prone WLAN environments.

This paper proposes a Random Early Detection Forward Error Correction (RED-FEC) mechanism to improve the quality of video delivered over Wireless Local Area Networks (WLANs). In contrast to previous FEC schemes, in which the rate determination information is fed back from the receiver side, in our proposed method, the redundancy rate is calculated directly at the wireless Access Point (AP) in accordance with the network traffic load, as indicated by the AP queue length. An analytical model is developed to predict the effective packet loss rate of a video stream delivered over a WLAN with RED-FEC protection. The numerical results show that the proposed RED-FEC mechanism consistently achieves higher recovery efficiency than a conventional FEC scheme under high and low network loading conditions.

The main purpose of this article is to provide researchers or practitioners with greater flexibility to analyze their proposed designs for network, protocol, or video coding of MDC video transmission without being obliged to consider a particular tool set for each kind of video-quality evaluation. Therefore, a generalized simulation and evaluation frame work for video transmission is an important and useful tool to the video-coding of networking was found by research community. On the one hand, for video-coding studies, one can simulate the effects of a more realistic network on video sequences resulting from their coding schemes. On the other hand, in networking analysis, one can evaluate the impact of real video streams on proposed network protocols

This paper develops a hierarchical packet pre-dropping (HPPD) approach that exploits different methods to process I (intra-coded)/P (predictive-coded) /B (bidirectionally predictive-coded) video frame packets to improve the video transmission quality over IEEE 802.11e Wireless Local Area Networks (WLANs). HPPD refers to the dropping of arriving packets if the preceding video frame packets in the same Group of Pictures (GOP) have been dropped. The simulation results demonstrate that, in terms of PSNR, the proposed scheme outperforms exiting schemes such as EDCA (Enhanced Distributed Channel Access) and adaptive mapping and novel mapping mechanism, suggesting that the resource of access channel in WLANs is not wasted in the transmission of useless video data.