Cloud-Edge Continuum Computing Platform hosts real-time applications over edge and cloud resources. The execution time of real-time applications composed of micro-services is increased by the communication latency, which is the time between a packet entering and leaving the network. To keep the execution time small, a latency-guaranteed network, which determines an upper bound of the latency, will be effective. Motivated by this requirement, we have been enhancing Deterministic Networking (DetNet), a protocol suite that builds a latency-guaranteed network over Wide-Area Networks (WAN).

Congestion control algorithms using recurrent neural network (RNN) for bandwidth prediction are expected to improve throughput. Previous studies involving performance evaluations were conducted only using simulated data. However, simulation and real-world environments are largely different and rarely provide equivalent prediction accuracy. Therefore, we will verify whether our proposed method provides better prediction accuracy in a real-world environment. We measured communications in a real environment and generated training data by converting packet captured data with measurement of prediction accuracy on the generated data. The results showed that the maximum percentage of correct responses was 79.71%, which was comparable to the results obtained using simulated data.

Popular data concentration is a widely accepted storage energy-saving technique which places frequently-accessed data on a small subset of hard disks and spins-down other infrequently-accessed disks. Many previous studies use intuitive heuristic algorithms for data placement that promote the imbalance in the access frequencies across hard disks. However, the relevance and the optimality of such file placements have not been rigorously investigated. In this paper, we formally define the energy-saving file placement problem under the capacity and performance constraints as a combinatorial optimization problem and show the theory of the optimal file placement where the file access rates in the next period are given. Our analysis based on a stochastic process of disk state transitions gives the theoretical support for the common heuristic placement method. To examine the effectiveness of the optimal file placement, we experimentally evaluate the energy-efficiency of a test storage system using the file access rates generated from the real access traces from Flickr. The experimental results show that the energy consumption can be reduced by 31.8 percent with the optimal file placement compared to the evenly distributed file placement. We also conduct simulation experiments to confirm the energy-saving impacts in larger-scale storage systems.

Prompt acknowledgment (ACK) of received packets is key to achieving high throughputs in the Transmission Control Protocol (TCP) data flows. This also applies to Multipath TCP (MPTCP), a variant of TCP that bundles multiple paths into a single logical flow. However, the original MPTCP takes advantage of multiple paths only when sending data packets, not ACK packets. In the original MPTCP, an ACK packet goes through the same path that its originating packet has come through, even if a better path is available. The path that the originating packet came through is not always an appropriate path because the characteristics of the path (RTT, bandwidth, etc.) can be diverse. However, it is possible to improve the promptness of ACKing if we can select the appropriate path that an ACK packet goes through, regardless of what path the original data packets came through. In this study, we propose a method for improving MPTCP throughputs by improving the promptness of receiving ACK. The method is referred to as HayACK. HayACK returns an ACK packet via a path with the lowest round-trip time (RTT), even if it is not a path that received a data packet. To examine the effectiveness of our proposal, we conducted experiments in Linux using our modified version of a MPTCP protocol stack. The evaluation results show that HayACK can improve MPTCP throughputs by a maximum of 1.74x, and by 1.52x on average.

Bandwidth and latency are two major factors that contribute the most to network application performance. Between each pair of switches in a network, there may be multiple paths connecting them. Each path has different properties because of multiple factors. Traditional shortest-path routing does not take this knowledge into consideration and may result in sub-optimal performance of applications and underutilization of network. We proposed a concept of "bandwidth and latency aware routing". The idea is that we could improve overall performance of the network by separating application into bandwidth-oriented and latency-oriented application and allocate different route for each type of application accordingly. We also proposed a design of this network system implemented using Open Flow. Routes are calculated from monitored information using Dijkstra algorithm and its variation. To support our design, we show a use case in which our design performs better than traditional routing as well as evaluation results.

In the era of cloud computing, data centers that accommodate a series of user-requested jobs with a diversity of resource usage pattern need to have the capability of efficiently distributing resources to each user job, based on individual resource usage patterns. In particular, for high-performance computing as a cloud service which allows many users to benefit from a large-scale computing system, a new framework for resource management that treats not only the CPU resources, but also the network resources in the data center is essential. In this paper, an SDN-enhanced JMS that efficiently handles both network and CPU resources and as a result accelerates the execution time of user jobs is introduced as a building block technology for such a HPC cloud. Our evaluation shows that the SDN-enhanced JMS efficiently leverages the fat-tree interconnect of cluster systems running behind the cloud to suppress the collision of communications generated by different jobs.

Recently, the concept of Software-Defined Network (SDN), which allows us to administer and configure a network in a centralized and software-programming manner, has gathered network engineers' and researchers' attention rapidly. In particular, the expectation and concern to OpenFlow as an implementation of the SDN is remarkable. As a result, research activities, which include prototyping, implementation, demonstration and experiments, conducted over OpenFlow networks have been a worldwide tendency. In such research activities, however, the difficulty in understanding network topology, traffic amount and an actual path of a network flow on the OpenFlow network, and the intricacies in debugging software designed for OpenFlow are serious problems in the development process of OpenFlow controller. This research aims to realize a visualization software that facilitates researchers to perform OpenFlow controller development and demonstration experiments performed on an actual OpenFlow network. In this paper, the authors summarize the achievement of their research work in progress as well as the future direction.

We generally utilize high-speed transport protocols to transfer and share large-scale data in long-distance broadband networks. However, the difference in performance between protocols when some kinds of protocols share the same link increases. Consequently, we propose a control method of discarding packets corresponding to protocol types that takes into consideration high-speed performance and fairness of flows. We evaluated the efficiency of our method in simulations. As a result, we found that it could allocate bandwidth equally while retaining high link utilization.

Advanced Layer-3 (L3) switches achieve high-speed IP packet forwarding by storing parts of the header information from transmitted packets into the flow cache in the switch fabric when relaying the IP packets between subnets. When IP traffic is overloaded on an L3 switch, the flow cache is easily exhausted, decreasing the IP packet forwarding performance. Virtual LAN (VLAN), a virtualization technology at the data-link layer, is widely used for the internal networks of many organizations because it allows network configurations to be changed easily and provides design flexibility. In a VLAN-based local area network with multiple L3 switches, the relaying point for each VLAN can be placed on any of the L3 switches. We developed a new network control scheme called distributed virtual routing, which dynamically controls the packet exchange points for each VLAN to suppress the consumption of flow caches. We describe the basic concept and then evaluate the reduction of the relaying flows through the simulation using the real network data.

This paper describes a framework for developing mobile software robots by using the PLANET mobile object system, which is characterized by a language-neutral layered architecture, the native code execution of mobile objects, and asynchronous object passing. We propose an approach to implementing mobile Web search robots that takes full advantage of these characteristics, and we base our discussion of its effectiveness on experiments conducted in the Internet environment. The results show that the PLANET approach to mobile Web search robots significantly reduces the amount of data transferred via the Internet and that it enables the robots to work more efficiently than the robots in the conventional stationary scheme whenever nontrivial amounts of HTML files are processed.