Summary The Precision Time Protocol (PTP) is a widely used protocol for high‐precision time synchronization, but it requires hardware or driver support for network interface card. Therefore, we propose a portable time synchronization method that is independent of them. Our method uses eBPF to synchronize time by recording timestamps of PTP packets in the kernel. eBPF is provided by the kernel and is backward‐compatible, making it independent of hardware or other software. To demonstrate the portability and high‐precision time synchronization capabilities of our method, we compared the time synchronization precision in physical environment and virtual machine. We also modified server settings that could affect time synchronization precision, and clarified the effects of these changes. The experiments showed that our method can achieve the similar level of time synchronization precision as conventional methods while remaining portable and independent of other components.

Telemetry is a new generation network monitoring technology, which could reduce the loads of probes by setting the frequency of probes and target of monitoring to switches. In-band Network Telemetry (INT) is a technique of telemetry which enables precise monitoring without reducing the traffic rate. It embeds the telemetry headers including information and instructions of INT processes, then INT enabled switches respond to the instructions in hardware-level. However, if all INT compatible switches simply respond the instruction, it will cause explosive growth of amount of collecting information and makes the load of analysis much heavier. In this paper, we discuss about design and implementation of selective telemetry mechanism which is fully controllable from edge-side. Using the proposed mechanism, administrators can select the switches which is required to be analyzed, then reduce the cost of monitoring. In our proposed mechanism, types of information and list of target switches are marked in the INT header, and only the target INT-enabled switches process the INT operation according to the instruction in the INT header of each packet. Our proposed approach will increase the controllability of telemetry and enhance the flexibility of management of large-scale network.

To reduce the computational cost of particle swarm optimization (PSO) methods, research has begun on the use of Graphics Processing Units (GPUs) to achieve faster processing speeds. However, since PSO methods search based on a global best value, they are hampered by the frequent need for communication with global memory. Even using a standard PSO that uses a local best value does not solve this problem. In this paper, we propose a virtual global best method that speeds up computations by defining a time-delayed global best as a virtual global best in order to reduce the frequency of communication with low-speed global memory. We also propose a method that combines decomposition-based multi-objective PSO (MOPSO/D) with a virtual global best method to speed up multi-objective particle swarm optimization by running it in parallel while maintaining search accuracy, and we demonstrate the effectiveness of this approach by using a number of unimodal/multimodal single objective benchmark test functions and three classical benchmark test functions with two objectives.

This paper describes methods for controlling routing points of VLAN domains using binary particle swarm optimization (BPSO) and angle modulated particle swarm optimization (AMPSO). Virtual LAN (VLAN) is a technique for virtualizing data link layer (or L2) and can construct arbitrary logical networks on top of a physical network. However, VLAN often causes much redundant traffic due to inappropriate deployments of network-layer (L3) routing capabilities in VLAN networks. We propose two methods using BPSO and AMPSO, and show that they can adaptively select the routing points dynamically in accordance with the observed traffic patterns and thus reduce the redundant traffic. The convergence features are compared with those of the conventional method on the basis of a statistical method. Then we also show that the scalability of the algorithm using AMPOS is high and thus we can expect that it is applicable to practical large VLAN environments.

This paper investigates the macroscopic behavior of unwanted traffic (e.g., virus, worm, backscatter of (D)DoS or misconfiguration) passing through the Internet. The data set we used are unwanted packets measured at /18 darknet in Japan from Oct. 2006 to Apr. 2009 that included the recent Conficker outbreak. The traffic behavior is quantified by the entropy of ten packet features (e.g., 5-tuple). Then, we apply PCA (principal component analysis) to a ten dimensional entropy time series matrix to obtain a suitable representation of unwanted traffic. PCA is a well-known and studied method for finding out normal and anomalous behaviors in Internet backbone traffic, however, few studies applied it to darknet traffic. We first demonstrate the high variability nature of the entropy time series for ten packet features. Next, we show that the top four principal components are sufficiently enough to describe the original traffic behavior. In particular, the first component can be interpreted as the type of unwanted traffic (i. e., worm/virus or scanning), and the second one as the difference in communication patterns (e. g., one-to-many or many-to-one). Those two components account for 63.8\% of the original data set in terms of the total variance. On the other hand, the outliers in the higher components indicate the presence of specific anomalies although most of mapped data to the components have less variability. Furthermore, we show that the scatter plot of the first and second principal component scores provides us with a better view of the macroscopic unwanted traffic behavior.

In this paper, we introduce the probabilistic awardee selection strategy, under which awardee is selected with a fixed probability, into the award phase of contract net protocol. We then point out that, by changing the probabilities in this strategy according the local workload, the overall performance can be considerably improved.

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 how, in large-scale multi-agent systems, each agent's adaptive selection of peer agents for collaborative tasks affects the overall performance and how this performance varies with the workload of the system and with fluctuations

We describe a new method to estimate the relevance of two items (such as products and works of art) on the basis of the relationship between the corresponding user (blogger) groups on a blogspace, where a user group refers to a collection of users interested in an item. We estimated the strength of the relationship between user groups on the basis of their proximity on the blogspace. We validated our approach through experimental studies using actual data. In developing the method for estimating relevance among items, we introduced a new technique for measuring the proximity of two groups of vertices on a network, which can be thought of as an extension of conventional co-occurrence analysis.

In this paper, we investigate temporal and spatial correlations of time series of unwanted traffic (i.e., darknet or network telescope traffic) in order to estimate statistical behavior of unwanted activities from a small size of darknet address block. First, from the analysis of long-range dependency, we point out that TCP time series has a weak temporal correlation though UDP time series without huge flooding is well-modeled using a Poisson process. Next, we analyze the spatial correlation between two traffic time series divided by different sized darknet address blocks. We confirm that a TCP SYN traffic time series (e.g, virus or worm) has a clear spatial correlation in the arrival of packets between two neighboring address blocks. Indeed, this spatial correlation remains in traffic time series 1,000 addresses far from the target time series, even if a darknet address block is small (e.g., /26). On the other hand, TCP SYNACK traffic (e.g., backscatter) and UDP traffic (e.g., virus or worm) have less spatial correlation between two adjacent large address blocks. Finally, we estimate the average propagation delay of global unwanted activities appearing in TCP SYN traffic by using the generalized inter-correlation coefficient.

We studied the problem of finding a subspace of Web pages that is contextually consistent for co-occurrence analysis. We looked at blogs and proposed blogger-based co-occurrence analysis, which assumes that two items are relevant to each other if they appear in any of the blog entries posted by the same blogger. We show that (1) blogger-based analysis outperforms conventional page-based analysis in solving context-sensitive problems and that (2) analysis focused on bloggers forming a community yields better performance compared with that focused on isolated bloggers.

The performance features of a massively multiagent system (MMAS) when applying the contract net protocol (CNP) are examined. The recent growth in the volume of e-commerce on the Internet is increasing the opportunities for coordinated transactions by agents, concurrently occurring everywhere. Because of limited CPU and network resources, running many interactive tasks among agents can lower the quality or efficiency of MMASs. Although CNP is a widely used negotiation protocol that can allocate tasks and resources to appropriate agents, it is unclear how effectively CNP works in an MMAS where thousands of agents work together and interfere with each other. The performance of CNP in such an MMAS, especially the overall efficiency and the reliability of promised completion times, is investigated by using an MAS simulation environment. The results show that only managerside control of CNP can improve performance in an MMAS.

Embedded computers pervade our lives. There are increasing opportunities for them to adopt embedded operating systems as they are required to have high functionality and complexity. Unfortunately, the reliability of such embedded systems is insufficient to support our lives in 24/7. Therefore, we propose the fine-grain proactive recovery (FPR) of operating system components. FPR enables an operating system to periodically restart its modules and thus to keep their states clean.

This paper presents personal networks, which integrate a VPN and the per-VPN execution environments of the hosts included in the VPN. The key point is that each execution environment called a portspace is bound to only one VPN, i.e., single-homed. Using this feature of portspaces, personal networks address several problems at multi-homed hosts that use multiple VPNs. Information flow is separated by personal networks so that it is not mixed at multi-homed hosts. IP addressing in a personal network is independent of the other personal networks, even the base network, and therefore does not conflict with those of other networks at multi-homed hosts. In addition, personal networks provide facilities for easy bootstrapping so that the end-users can construct such isolated networks easily. Inheritance of portspaces supports the creation of new portspaces based on existing portspaces. Self-construction of personal networks enables end-users to construct personal networks without help from the base network.

In this paper, we describe the design and implementation of an extended concurrent object model for distributed and multiuser systems called the Multiversion Concurrent Object (MCO). In this model, an object executes multiple methods concurrently within itself, but is handled as a concurrent object. Each MCO makes a copy of its own state, called a version, for executing a method that is not interleaved with other similar copies during execution. The results of concurrent execution are merged at termination of each method. The MCO increases programmability, because it does not require any synchronization statements inside its methods. Using this model for shared objects, we can construct a system in which each user can work freely without being negatively impacted by others. Finally, a prototype implementation of MCO and performance evaluations are presented.