Networking technologies have recently been evolving and network applications are now expected to support flexible composition of upper-layer network services, such as security, QoS, or personal firewall. We propose a multi-platform framework called FreeNA* that extends existing applications by incorporating the services based on user definitions. This extension does not require users to modify their systems at all. Therefore, FreeNA is valuable for experimental system usage. We implemented FreeNA on both Linux and Microsoft Windows operating systems, and evaluated their functionality and performance. In this paper, we describe the design and implementation of FreeNA including details on how to insert network services into existing applications and how to create services in a multi-platform environment. We also give an example implementation of a service with SSL, a functionality comparison with relevant systems, and our performance evaluation results. The results show that FreeNA offers finer configurability, composability, and usability than other similar systems. We also show that the throughput degradation of transparent service insertion is 2% at most compared with a method of directly inserting such services into applications.

Public switching systems are intensively realtime and multi-processing, very large, long-lived, and frequently modified. Programs that control switching systems are therefore required not only to have run-time efficiency but also to be easy to maintain and extend. This paper proposes a Concurrent Object Model and an Object-Oriented Switching Program Structure. The Concurrent Object Model ensures simple and efficient real-time multi-processing. This model allows logical switching components to be implemented as "objects" in software, and the structure of the program coincides with the structure of the logical model. The program structure proposed here uses distributed call processing, which allows building-block-structured switching systems. A prototype switching program proved the effectiveness of this approach and showed that the static and dynamic overheads are within the capacity of present VLSI technology.

Wireless connections between computers and devices introduce a new problem called device migration, which is the dynamic switching of a connection between a computer and a device. This paper describes a new system called the Network Extended Device Management System (NextD), which enables users to continue using a device even if device migration occurs. NextD's functions are device tracking, remote device access, seamless switching, and providing services over network boundaries. The system supports many device types, including a human interface device (HID) and audio and voice devices over both wireless and wired connections. We have implemented NextD on Linux. Experimental results showed that NextD is capable of supporting HIDs, and audio and voice devices, and that its processing time for a device migration is sufficient enough for actual use.

Telecommunication services are becoming more and more personalized, integrated, and refined. Advanced personal and mobile telecommunication services, intelligent networks, and network management operations require cooperative network-wide distributed processing on a very large scale. Telecommunication programs must support these services with great flexibility, efficiency, and reliability. This paper proposes a new call processing model that improves the availability and flexibility of telecommunication programs. It first points out requirements, outlines the distributed processing platform PLATINA, and discusses several approaches to the enhanced call processing model. Then it explains the call processing program structure, and gives illustrations of mobile and multi- party service control as typical examples. The Caller-Callee decomposition reduces the complexity of the call processing program and enhances the call model; the separation of call and bearer enhances service flexibility and integration; distributed object-oriented techniques meet software evolution requirements. A prototype program has been implemented and has proved the effectiveness of this approach.

Most distributed systems are based on either the C/S (Client/Server) model or the P-to-P (Peer to Peer) model. In C/S based distributed systems, a client invokes a server and waits for the server reply. Because of this sequential nature, C/S based distributed systems can be implemented by the RPC (Remote Procedure Call) scheme. Most tools for developing distributed objects are based on the RPC scheme. Whereas, in P-to-P based distributed systems, each distributed objects work concurrently, by exchanging asynchronous messages, without waiting for the receiver's action. To implement these P-to-P distributed systems, the RPC scheme is not powerful enough, and the active object model using asynchronous messages is suitable. This paper explains the pure Java library CAPE for developing P-to-P based distributed active object systems.

Object caching is a common feature in the scalable distributed object systems. Fine-grained replication optimizes the performance and resource utilization in object caching by enabling a remote object-oriented application to be partially and incrementally on-demand replicated in units of cluster. Despite these benefits, the lack of common and simple implementation framework makes the fine-grained replication scheme not extensively used. This paper proposes the novel frameworks for dynamic, transparent, partial and automatically incremental replication of distributed Java objects based on three techniques that are lazy-object creation, proxy and hook. One framework enables the fine-grained replication of server-side stateful in-memory application, and the other framework enables the fine-grained replication of server-side stateless in-memory application, client-side program, or standalone application. The experimental evaluation demonstrates that the efficiency in terms of response time of both frameworks are relatively practical to the extent of a local method invocation.

In the age of pervasive computing, ubiquitous collaboration has become an every-day life paradigm. Without an ideal computing infrastructure, issues with ubiquitous collaboration, such as network unreliability, platform heterogeneity, and client's resource constraints, are inevitable. The traditional replication scheme copes with network unreliability by replicating all the objects of a shared application together at once. This is, however, suitable for neither cooperative applications nor mobile computing devices. These problems can be naturally addressed by using a fine-grained replication scheme that enables a portion of the application objects to be replicated. This paper presents an object-oriented middleware that is capable of dynamically and transparently replicating remotely shared Java applications in a partially and on-demand incremental manner. It is also able to maintain various consistency semantics and enables the coexistence of fine-grained replications and conventional remote method invocations. Empirical results indicate several practical benefits of the middleware.