Active network monitoring based on Boolean network tomography is a promising technique to localize link failures instantly in transport networks. However, the required set of monitoring trails must be recomputed after each link failure has occurred to handle succeeding link failures. Existing heuristic methods cannot compute the required monitoring trails in a sufficiently short time when multiple-link failures must be localized in the whole of large-scale managed networks. This paper proposes an approach for computing the required monitoring trails within an allowable expected period specified beforehand. A random walk-based analysis estimates the number of monitoring trails to be computed in the proposed approach. The estimated number of monitoring trails are computed by a lightweight method that only guarantees partial localization within restricted areas. The lightweight method is repeatedly executed until a successful set of monitoring trails achieving unambiguous localization in the entire managed networks can be obtained. This paper demonstrates that the proposed approach can compute a small number of monitoring trails for localizing all independent dual-link failures in managed networks made up of thousands of links within a given expected short period.

A framework for deploying application-specific overlay networking is presented. It enables network protocols for transmitting data and agents to be naturally facilitated as mobile agents. It can also implement the deployment of mobile agent-based protocols within mobile agents. It can customize the deployment of network protocols as well as data transmission by migrating and replacing corresponding mobile agent-based protocols. It provides a self-deployment mechanism for the overlay network. This paper describes the system and its prototype implementation, which uses Java as both the implementation language and the protocol development language.

An active network has the advantage of being able to accept new protocols quickly and easily. The cluster-based active router can provide sufficient computing power for customized computations. In the router architecture, load balancing is achieved by the efficient distribution of packets. We present a packet distribution scheme according to estimated processing time.

As the Internet has become the infrastructure for the global communication, the quality degradation due to network failures and illegal traffic such as DDoS (Distributed Denial of Service) have become a serious problem. In order to solve the problem, a network monitoring system that monitors the traffic of Internet in real time is strongly desired. Traffic monitors that collect the statistics from captured packets play a key roll in the system; however, they are not flexible enough for being used in the rapidly changing Internet. The traditional approach such that a new traffic monitor is developed for a new requirement results in a long turn around time of the development. Therefore, we have proposed a flexible network monitoring system that consists of programmable traffic monitors. Traffic monitors are made programmable by introducing active network techniques; therefore, we call the network monitoring system as the programmable monitor network. This paper describes the implementation of the programmable monitor network and its application to DDoS (Distributed Denial of Service) attack detection.

Real-world IP networks are heterogeneous in terms of server and link capacities. A sophisticated and comprehensive load balancing method is essential if we are to avoid congestion in the servers and links of heterogeneous networks. If such a method is not available, network throughput is limited by bottleneck servers or links. This paper proposes an anycast technique that achieves load balancing under heterogeneity. The proposed method well suits implementation on active networks. By taking advantage of the processing ability provided by active nodes, the method can decide packet routes flexibly on the basis of various criteria to realize a variety of load balancing schemes. Some of these schemes can successfully prevent the congestion of heterogeneous networks by tackling bottlenecks in both server and link capacities. The method is also advantageous given its light control load even when using many mirrored servers. Computer simulations confirm the effectiveness of these features.

Distributed Denial of Service (DDoS) attacks are a pressing problem on the Internet as demonstrated by recent attacks on major e-commerce servers and ISPs. Since the attack is highly distributed, an effective solution must be formulated with a distributed approach. Recently, some solutions, in which intermediate network nodes filter or shape congested traffic, have been proposed. These solutions may decrease the congested traffic, but they still cause "collateral victims problem," that is, legitimate packets may be discarded mistakenly. In this paper, we propose Active Countermeasure Platform to minimize traffic congestion and to address the collateral victim problem using the Active Networks paradigm, which incorporates programmability into intermediate network nodes. Our platform can prevent overloading of the target and consuming the network bandwidth of both the backbone and the protected site autonomously. In addition, it can improve the collateral victim problem based on user policy. This paper shows the concept of our platform, system design and evaluation of the effectiveness using a prototype.

This paper proposes a credit-based congestion control scheme for multicast communication which employs application-specific processing at intermediate network nodes. The control scheme was designed not only to take advantage of credit-based flow control for unicast communication, but also to achieve flexibility supported by active network technology. The resultant active multicast congestion control scheme is able to meet the different requirements of various multicast applications in terms of reliability and end-to-end latency. The performance of the proposed control scheme was evaluated using both discrete-event simulations and experiments on a prototype active network implementation. The results show that the proposed scheme performs very well in terms of fairness, responsiveness, and scalability. The implementation experiences also confirmed the feasibility of the scheme in practice.

We present a simple framework for multicasting video in an active network, in which we overcome heterogeneity in the quality requests by filtering the video stream at some properly located active nodes. The framework includes the requirements for the underlying active network and outlines the video multicast application. We then introduce a heuristic algorithm for electing the filtering nodes to conform a multicast distribution tree, in which we use an objective function to, for example, minimize the required bandwidth. We evaluate the performance of our algorithm comparing it with simulcast and layered encoded transmission through simulation experiments, showing some advantages of using active filtering.

This paper proposes an Active Networks architecture for VoIP gateway. In the proposed architecture, instead of procedural language, declarative language is used to describe the up-loaded program. This allows for a reduction in size of the up-loaded program, and increases the flexibility for describing the up-loaded program. VoIP gateway can then provide highly flexible services. An experimental system was implemented for feasibility studies. Specification of the declarative language used for describing the up-loaded program, basic functionalities of an interpreter for the language, and execution control program which executes components programs stored the node beforehand were confirmed.

In server load balancing where replicated servers are dispersed geographically and accesses from clients are distributed to replicated servers, a way of distributing the accesses from clients to an adequate server plays an important role from the viewpoint of load balancing. In the paper, we propose a new network paradigm for server load balancing using active anycast. In active anycast, an end user only sends its request to group of servers using an anycast address. When this request arrives at an active router, it selects an adequate server from the viewpoint of load balancing and changes the anycast address of a packet to the unicast address of the selected server. The decision which server is the best one from the viewpoint of server load balancing is made by an active router rather than an end user, so active anycast is a network-initiated method. Simulation results show that active anycast can accomplish efficient server load balancing, even when a small part of routers are equipped with active network technology.

In order to increase the flexibility and the extensibility for packet transmission, the active network approach, that makes network nodes programmable, is very promising. Every packet includes a program specifying behavior of the packet at network nodes, and the network nodes only have the functions to execute programs of the packet. In an active network, network congestion management is achieved more flexibly and intelligently than that in the conventional internet. A number of mechanisms for congestion management are easily developed because various network functions such as QoS routing and congestion detection are easily combined in the same network nodes. By executing different routing protocols that use different levels of the link information, a congestion management scheme can be customized by users. This paper shows how QoS routing and congestion detection achieve a congestion management over an active internetwork system.

Processes in image recognition include target detection and shape extraction. Active Net has been proposed as one of the methods for such processing. It treats the target detection in an image as an energy optimization problem. In this paper, a problem of the conventional Active Net is presented and the new Active Net is proposed. The new net is improved the ability for detecting a target. Finally, the validity of the proposed net is confirmed by experimental results.

This paper presents a design and implementation of a ATM multicast service based on programmable and active network concepts. It aims to address the design and implementation issues of creating new network services--multicast in this case--through a set of corba-based network interfaces, and with a java based user codes injection mechanism for supporting customization of network services. We demonstrate the feasibility of our prototype through the implementation of a wavelet video multicast application with active filters implanted at intermediate nodes for supporting heterogeneous receivers and the implementation of a congestion control scheme. The performance of the prototype over an ATM test-bed is measured and evaluated.

In this paper, we propose a method to detect a road sign from a road scene image in the daytime. In order to utilize color feature of sign efficiently, color distribution of sign is examined, and then color similarity map is constructed. Additionally, color similarity shown on the map is incorporated into image energy of an active net model. A road sign is extracted as if it is wrapped up in an active net. Some experimental results obtained by applying an active net to images are presented.

Active net is a deformable model which utilizes the network analogy of a physical region. In the model, the region of a target is detected by minimizing the energy defined for the sample points of the model. The region of the target is extracted using fixed network topology in the orginally proposed algorithm. In this paper, we introduce the network reconfiguration mechanisms such as tearing and division to realize multiple objects detection and complex object detecion. The introduced algorithm dynamically unlinks the arcs of the network when their strain value exceeds predefined threshold level. In the method, we propose a new image energy which improves the position sensitivity of edges without increasing computation cost. Experimental results for images taken by video camera show the validity of our approach.

This paper proposes a new circuit configuration for realizing a type 1 mutator using two current conveyor (CCIIs) and a network with a suitable current transfer function. The advantage of the proposed circuit configuration is that any impedance functions which are proportional to the realizable current transfer function can be simulated.

This paper treats the synthesis of immittance floatator using nullors. Eight sets of circuit equations for realizing immittance floatators and their nullor (nullator-norator) representations are given. By replacing nullors with active elements such as biporlar junction transistors (BJTs), current conveyors (CCIIs), operational amplifiers (OAs) and operational transconductance amplifiers (OTAs), the immittance floatators can be derived. The development is important because it enables one to convert the present wealth of knowledge concerning grounded immittance simulation networks into floating immittance simulation networks. Using immittance floatators, we can obtain not only the floating form of 1-port but also that of 2-port networks. Novel circuits use solely minus-type norators. Using one-type (minus- or plus-type) norators greatly simplifies the simulation circuit. In the case of an immittance floatator using CCIIs as the active elements, the effects of nonideal CCIIs and sensitivities are given. Many circuits can be systematically derived using nullor technique.