The technologies, architectures, and methodologies traditionally used to develop distributed applications exhibit a variety of limitations and drawbacks when applied to large scale distributed settings (e.g., the Internet). In particular, they fail in providing the desired degree of configurability, scalability, and customizability. To address these issues, researchers are investigating a variety of innovative approaches. The most promising and intriguing ones are those based on the ability of moving code across the nodes of a network, exploiting the notion of mobile code. As an emerging research field, code mobility is generating a growing body of scientific literature and industrial developments. Nevertheless, the field is still characterized by the lack of a sound and comprehensive body of concepts and terms. As a consequence, it is rather difficult to understand, assess, and compare the existing approaches. In turn, this limits our ability to fully exploit them in practice, and to further promote the research work on mobile code. Indeed, a significant symptom of this situation is the lack of a commonly accepted and sound definition of the term "mobile code" itself. This paper presents a conceptual framework for understanding code mobility. The framework is centered around a classification that introduces three dimensions: technologies, design paradigms, and applications. The contribution of the paper is twofold. First, it provides a set of terms and concepts to understand and compare the approaches based on the notion of mobile code. Second, it introduces criteria and guidelines that support the developer in the identification of the classes of applications that can leverage off of mobile code, in the design of these applications, and, finally, in the selection of the most appropriate implementation technologies. The presentation of the classification is intertwined with a review of the state of the art in the field. Finally, the use of the classification is exemplified in a case study.

This paper discusses the challenges in computer systems research posed by the emerging field of pervasive computing. It first examines the relationship of this new field to its predecessors: distributed systems and mobile computing. It then identifies four new research thrusts: effective use of smart spaces, invisibility, localized scalability, and masking uneven conditioning. Next, it sketches a couple of hypothetical pervasive computing scenarios, and uses them to identify key capabilities missing from today's systems. The paper closes with a discussion of the research necessary to develop these capabilities.

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This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in TCP/IP-based internets. In particular, it defines objects for managing remote network monitoring devices. Table of Contents 1. The Network Management Framework ...................... 2 2. Overview .............................................. 3 2.1 Remote Network Management Goals ...................... 3 2.2 Textual Conventions .................................. 5 2.3 Structure of MIB ..................................... 5 2.3.1 The Ethernet Statistics Group ...................... 6 2.3.2 The History Control Group .......................... 6 2.3.3 The Ethernet History Group ......................... 6 2.3.4 The Alarm Group .................................... 6 2.3.5 The Host Group ..................................... 6 2.3.6 The HostTopN Group ................................. 7 2.3.7 The Matrix Group ................................... 7 2.3.8 The Filter Group ..........

World-Wide Web server over the course a year and a half. This paper presents a longitudinal look at various network path properties, as well as the implementation status of various protocol options and mechanisms. In particular, this paper considers how WorldWide Web clients utilize TCP connections to transfer web data; the deployment of various TCP and HTTP options; the range of round-trip times observed in the network; packet sizes used for WWW transfers; the implications of the measured advertised window sizes; and the impact of using larger initial congestion window sizes. These properties/mechanisms and their implications are explored. An additional goal of this paper is to provide information to help researchers better simulate and emulate realistic networks.

Historical Perspective ............................... 2 3. Columnar Objects ..................................... 3 3.1 Row Deletion ........................................ 4 3.2 Row Addition ........................................ 4 4. Defining Objects ..................................... 5 4.1 Mapping of the OBJECT-TYPE macro .................... 7 4.1.1 Mapping of the SYNTAX clause ...................... 7 4.1.2 Mapping of the ACCESS clause ...................... 8 4.1.3 Mapping of the STATUS clause ...................... 8 4.1.4 Mapping of the DESCRIPTION clause ................. 8 4.1.5 Mapping of the REFERENCE clause ................... 8 4.1.6 Mapping of the INDEX clause ....................... 8 4.1.7 Mapping of the DEFVAL clause ...................... 10 4.1.8 Mapping of the OBJECT-TYPE value .................. 11 4.2 Usage Example ....................................... 11 5. Appendix: DE-osifying MIBs .....................

Internet backbone networks are under constant flux in order to keep up with demand and to offer new features. The pace of change in features and technology often outstrips the pace of introduction of the associated fault monitoring capabilities that are built into today’s IP protocols and routers. Moreover, some of these new technologies cross networking layers, raising the potential for unanticipated interactions and service disruptions, which the built-in monitoring capabilities in each layer may not detect. In these instances, operators typically employ higher-layer monitoring techniques such as end-to-end liveness probing to detect lower- or cross-layer failures, but lack tools to precisely determine where a detected failure may have occurred. In this paper, we evaluate the effectiveness of using risk modeling to translate high-level failure notifications into lower-layer root causes. We show that a simple greedy heuristic works with accuracy exceeding 80 % for many failure scenarios in realistic topologies, while delivering extremely high precision (greater than 80%). We further report our operational experience using risk modeling to isolate optical component and MPLS controlplane failures in a tier-1 ISP.

... This paper introduces Smart Packets and describes the Smart Packets architecture, the packet formats, the language and its design goals, and security considerations.

The Tempest framework allows the dynamic introduction and modification of network services at two levels of granularity. First, the switchlet and associated virtual network concepts enable the safe introduction of alternative control architectures into an operational network. The timescales over which such new control architectures can be introduced might vary from, for example, a video conferencing specific control architecture, which is active only for the duration of the conference, to a new version of a general purpose control architecture, which might be active for several months or longer. Second, the Tempest framework allows refinement of services at a finer level of granularity by means of the connection closure concept. In this case modification of services can be performed at an application specific level. These attributes of the Tempest framework allows service providers to effectively become network operators for some well defined partition of the physical network...

Our goal is to design a traffic model for non congested Internet backbone links, which is simple enough to be used in network operation, while being as general as possible. The proposed solution is to model the traffic at the flow level by a Poisson shot-noise process. In our model, a flow is a generic notion that must be able to capture the characteristics of any kind of data stream. We analyze the accuracy of the model with real traffic traces collected on the Sprint IP (Internet Protocol) backbone network. Despite its simplicity, our model provides a good approximation of the real traffic observed in the backbone and of its variation. Finally, we discuss the application of our model to network design and dimensioning.