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Articles 1621 - 1650 of 1828

Full-Text Articles in Engineering

Extending Atm Networks For Efficient Reliable Multicast, Jonathan S. Turner Jan 1996

Extending Atm Networks For Efficient Reliable Multicast, Jonathan S. Turner

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One of the important features of ATM networks is their ability to support multicast communications. This facilitates the efficient distribution of multimedia information streams (such as audio and video) to large groups of receivers (potentially millions). Because ATM networks do not provide reliable delivery mechanisms, it is up to end systems to provide end-to-end reliability where it is needed. While this is straightforward for point-to-point virtual circuits, it is more difficult for one-to many and many-to-mamy virtual circuits. In this report, we propose some minimal extensions to the hardware of ATM switches that enables end systems to implement reliable multicast …

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Analysis Of Mpeg Compressed Video Traffic, Jerome R. Cox Jr., O. Matthew Beal Jan 1996

Analysis Of Mpeg Compressed Video Traffic, Jerome R. Cox Jr., O. Matthew Beal

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This paper outlines a study of MPEG compressed video sequences and simulation of multiplexed video traffic in the ATM environment. A number of statistical characteristics including autocorrelation and variance of MPEG-1 compressed video sequences are used to characterize the 16 sample traces used in this study. From these measurements, a preliminary model is developed which utilizes basic measurements of the individual component video sequences to predict bandwidth requirements and cell loss of the multiplexed video traffic.

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Design Of Nonblocking Atm Networks, J. Andrew Fingerhut, Rob Jackson, Subhash Suri, Jonathan S. Turner Jan 1996

Design Of Nonblocking Atm Networks, J. Andrew Fingerhut, Rob Jackson, Subhash Suri, Jonathan S. Turner

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This paper considers the problem of designing ATM networks that are nonblocking with respect to virtual circuit requests, subject to specified constraints on the traffic. In this paper, we focus on global traffic constraints that simply limit the total entering and exiting traffic at each switching system. After reviewing prior results for linear link costs, we introduce a more realistic link cost model, and develop a number of results using it. We also describe a technique for converting tree-structured networks to nonblocking hierarchical networks satisfying limits on the capacity of any single switch.

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Simulation Of Asynchronous Instruction Pipelines, Chia-Hsing Chien, Mark A. Franklin Jan 1996

Simulation Of Asynchronous Instruction Pipelines, Chia-Hsing Chien, Mark A. Franklin

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This paper presents the ARAS simulator with which asynchronous instruction pipelines can be modelled, simulated and displayed. ARAS allows one to construct instruction pipelines by preparing various configuration files. Using these files and a number of benchmark programs, performance of the instruction pipelines can be obtained. The performance of asynchronous instruction pipelines can also be compared to synchronous case. Thus, one can decide the optimal design for instruction pipelines in asynchornous or synchronous cases and explore the deisng space of asynchronous instruction pipeline architectures.

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Design Of A Gigabit Atm Switch, Tom Chaney, Andrew Fingerhut, Margaret Flucke, Jonathan S. Turner Jan 1996

Design Of A Gigabit Atm Switch, Tom Chaney, Andrew Fingerhut, Margaret Flucke, Jonathan S. Turner

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This report describes the design and implementation of a gigabit ATM switching system supporting link rates from 150 Mb/s to 2.4 Gb/s, with a uniquely efficient multicast switch architecture that enables the construction of systems with essentially constant per port costs for configurations ranging from 8 to 4096 ports and system capacities approaching 1- Tb.s. The system design supports many-to-one and many-to-many forms of multicast, in addition to the usual one-to-many. It also provides multicast virtual paths, constant time configuration of multicast connections and an efficient packet-level discard method, that can achieve 100% link efficiencies, without large buffers.

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On The Performance Of Early Packet Discard, Maurizio Casoni, Jonathan S. Turner Jan 1996

On The Performance Of Early Packet Discard, Maurizio Casoni, Jonathan S. Turner

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In a previous paper [3], one of the authors, gave a worst-case analysis for the Early Packet Discard (EPD) technique for maintaining packet integrity during overload in ATM switches. This analysis showed that to ensure 100% goodput during overload under worst-case conditions, requires a buffer with enough storage for one maximum length packet from every active virtual circuit. This paper refines that analysis, using assumptions that are closer to what we expect to see in practice and examines how EPD performs when the buffer is not large enough to achieve 100% goodput. We show that 100% goodput can be achieved …

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Vaudeville: A High Performance, Voice-Activated Teleconferencing Application, Jyoti K. Parwatikar, T. Paul Mccartney, John D. Dehart, Maynard Engebretson, Kenneth J. Goldman Jan 1996

Vaudeville: A High Performance, Voice-Activated Teleconferencing Application, Jyoti K. Parwatikar, T. Paul Mccartney, John D. Dehart, Maynard Engebretson, Kenneth J. Goldman

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We present a voice-activated, hands-off, ATM-based video conferencing application. The application, called Vaudeville, features high quality NTSC video, voice-activated audio transmission, audio bridging of two audio streams, and voice-activated video switching. It supports multiple simultaneous multi-party conferences using a scalable multicast mechanism. We describe how Vaudeville was built using a component-based distributed programming environment. We also describe the algorithms used to contorl the audio and video of the applciation. Audio and video are encoded in hardware using an ATM hardware multimedia interface.

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Supporting Dis Applications Using Atm Multipoint Connection Caching, Anshul Kantawala, Guru Parulkar, John Dehart, Ted Marz Jan 1996

Supporting Dis Applications Using Atm Multipoint Connection Caching, Anshul Kantawala, Guru Parulkar, John Dehart, Ted Marz

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This report describes an ATM Multipoint Connection Caching strategy (AMCC) to control the explosive growth of traffic within the network and at an endpoint in a large Distributed Interactive Simulation (DIS) application such as a battlefield simulation. For very large DIS applications with 100,000 entities, the current method of broadcasting information among entities will no longer be feasible due to computational and network bandwidth limitations. Our scheme divides the simulation space into grids and each grid square or a set of grid squares forms a multicast group. Entities join the groups within their perception range and thus, they receive state …

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Efficient User Space Protocol Implementations With Qos Guarantees Using Real-Time Upcalls, R. Gopalakrishnan, Guru M. Parulkar Jan 1996

Efficient User Space Protocol Implementations With Qos Guarantees Using Real-Time Upcalls, R. Gopalakrishnan, Guru M. Parulkar

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Real-time upcalls (RTUs) are an operating systems mechanism to provide quality-of-service (QoS) guarantees to network applications, and to efficiently implement protocols in user space with (QoS) guarantees. Traditionally, threads (and real-time extensions to threads) have been used to structure concurrent activities in user space protocol implementations. However, preemptive scheduling required for real-time threads leads to excessive context switching, and introduces the need for expensive concurrency control mechanisms such as locking. The RTU mechanism exploits the iterative nature of protocol processing to eliminate the need for locking, and reduce asynchronous preemption, while ensuring real-time operation. In addition to efficiency, eliminating the …

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Negotiation As A Resource Allocation Process, Fernando Tohme Jan 1996

Negotiation As A Resource Allocation Process, Fernando Tohme

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The main economic-theoretic approcahes to the problem of resource allocation make little if any reference to negotiation processes. These processes are fundamentally linguistic, based on the exchange of messages among agents. Communication being so fundamental in the characterization of negotiation processes, the analysis of negotiation must emphasize on the structure of the language in which the negotiations take place. Computer science and particularly Artificial Intelligence have provided interesting insights about that linguistic structure. In the first part of this work we present a brief survey of the literature on resource allocation processes in which communication among agents plays a relevant …

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A Pilot Study Of Speech And Pen User Interface For Graphical Editing, Karl E. Schmidt Jan 1996

A Pilot Study Of Speech And Pen User Interface For Graphical Editing, Karl E. Schmidt

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As computer size continues to decrease and new user interface technologies become more ubiquitous, the conventional keyboard and mouse input interfaces are becoming harder to design into newer machines and less practical for use in some applications. The pen is one input technology more suited for the upcoming generation of smaller computers using direct manipulation interfaces. However, a pen-only user interface relies on continuous gesture and handwriting tecognizers that are often slow, inaccurate, and error prone for command and text entry. Speech recognition is an input modality that can input commands quickly and potentially be a fast text entry mechanism, …

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Reconsidering Fragmentation And Reassembly, Girish P. Chandranmenon, George Varghese Jan 1996

Reconsidering Fragmentation And Reassembly, Girish P. Chandranmenon, George Varghese

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We reconsider several issues related to fragmentation and reassembly in IP. We first reconsider reassembly. We describe a simple expected case optimization that improves reassembly performance to 38 instructions per fragment if the fragments arrive in FIFO order (the same assumption made in header prediction) which has been implemented in the NetBSD kernel. Next, we introduce the new idea of Graceful Intermediate Reassembly (GIR), which is a generalization of the existing IP mechanisms of destination and hop-by-hop reassembly. In GIR, we coalesce the fragments at an intermediate router in order to use the largest sized packets on its outgoing interface. …

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Continuous Compilation For Software Development And Mobile Computing, Michael P. Plezbert Jan 1996

Continuous Compilation For Software Development And Mobile Computing, Michael P. Plezbert

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Software developers typically must choose between interpreted and compiled environments for their programming activities. However, the current trends toward mobile computing and platform independence suggest moving to a new continuous compilation paradigm that integrates the advantages of each environment. Movement in this direction can already be seen in the development of Sun Microsystems' Java environment. The resulting continuous compiler operates not as a prelude to, but rather in tandem with, program execution. In this thesis we present the results of experiments that compare the performance of the continuous compilation model with a more traditional model and show that a performance …

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The Apic Approach To High Performance Network Interface Design: Protected Dma And Other Techniques, Zubin D. Dittia, Guru M. Parulkar, Jerome R. Cox Jr. Jan 1996

The Apic Approach To High Performance Network Interface Design: Protected Dma And Other Techniques, Zubin D. Dittia, Guru M. Parulkar, Jerome R. Cox Jr.

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We are building a very high performance 1.2 Gb/s ATM network interface chip called the APIC (ATM Port Interconnect Controller). In addition to borrowing userful ideas from a number of research and commercial prototypes, the APIC design embraces several innovative features, and integrates all of these pieces into a coherent whole. This paper describes some of the novel ideas that have been incorporated in the APIC design with a view to improving the bandwidth and latency seen by end-applications. Among the techniques described, Protected DMA and Protected I/O were designed to allow applications to queue data for transmission or reception …

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Alchourron's Defeasible Conditionals And Defeasible Reasoning, Fernando Tohme, Ronald P. Loui Jan 1996

Alchourron's Defeasible Conditionals And Defeasible Reasoning, Fernando Tohme, Ronald P. Loui

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No abstract provided.

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Building Distributed Applications With Design Patterns, Gruia-Catalin Roman, James C. Hu Jan 1996

Building Distributed Applications With Design Patterns, Gruia-Catalin Roman, James C. Hu

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Design patterns are a topic of great current interest within the object-oriented programming community. The motivation is both economical and intellectual. On one hand, there is the hope of establishing a common culture and language that fosters communicatino and growth in the software engineering field. While a community dominated by empiricism is seeking to achieve higher levels of formality by capturing its experiences in the form of catalogs of design patterns, another community, deeply rooted in formal thinking, is seeking to make its mark on the every day workings of the software engineering process. Distributed algorithms and the heuristics used …

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Mobile Unity Coordination Constructs Applied To Packet Forwarding For Mobile Hosts, Peter J. Mccann, Gruia-Catalin Roman Jan 1996

Mobile Unity Coordination Constructs Applied To Packet Forwarding For Mobile Hosts, Peter J. Mccann, Gruia-Catalin Roman

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With recent advances in wireless communication technology, mobile computing is an increasingly important area of research. A mobile system is one where independently executing components may migrate through some space during the course of the computation, and where the pattern of connectivity among the components changes as they move in and out of proximity. Mobile UNITY is a language and logic for specifying and reasoning about mobile systems, the components of which must operate in a highly decoupled way. In this paper it is argued that Mobile UNITY contributes to the modular development of system specifications because of the declarative …

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End-User Construction And Configuration Of Distributed Multimedia Applications, Terrance Paul Mccartney Jan 1996

End-User Construction And Configuration Of Distributed Multimedia Applications, Terrance Paul Mccartney

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Distributed multimedia applications supported by a global electronic infrastructure have tremendous potential for providing users with customized communication and computation environments. Since communication and computation requirements vary by context and change dynamically, it is unlikely that off-the-shelf applications will anticipate the needs of all users. Therefore, empowering end-users to create their own customized applications for both communication and computation is an important challenge. This dissertation presents several mechanisms that enable end-users to create and configure distributed multimedia applications, including end-users construction direct manipulation graphical users interface (GUIs) and application management of distributed multimedia applications over the Internet.

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Leap Forward Virtual Clock: An O(Loglogn) Fair Queuing Scheme With Guaranteed Delays And Throughput Fairness, Subhash Suri, George Varghese, Girish P. Chandranmenon Jan 1996

Leap Forward Virtual Clock: An O(Loglogn) Fair Queuing Scheme With Guaranteed Delays And Throughput Fairness, Subhash Suri, George Varghese, Girish P. Chandranmenon

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We describe an efficient fair queuing scheme, Leap Forward Virtual Clock, that provides end-to-end delay bounds almost identical to that of PGPS fair queuing, along with throughput fairness. Our scheme can be implemented with a worst-case time O(loglogN) per packet guaranteed delay and throughput fairness. As its name suggests, our scheme is based on Zhang's virtual clock. While the original virtual clock scheme does not achieve throughput fairness, we can modify it with a simple leap forward mechanism that keeps the server clock from lagging too far behind the packet tags. We prove that our scheme guarantees a fair share …

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Designing Minimum Cost Nonblocking Communication Networks, J. Andrew Fingerhut, Subhash Suri, Jonathan S. Turner Jan 1996

Designing Minimum Cost Nonblocking Communication Networks, J. Andrew Fingerhut, Subhash Suri, Jonathan S. Turner

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This paper addresses the problem of topological design of ATM (and similar) communication networks. We formulate the problem from a worst-case point of view, seeking network desings that, subject to specified traffic constraints, are nonblocking for point-to-point and multicast virtual circuits. Within this model we give various conditions under which star networks are optimal or near-optimal. These conditions are approximately satisfied in many common situations making the results of practical significance. An important consequence of these results is that, where they apply, there is no added cost for nonblocking multicast communication, relative to networks that are nonblocking for point-to-point traffic …

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Pac Learing Of One-Dimensional Patterns, Paul W. Goldberg, Sally A. Goldman, Stephen D. Scott Jan 1995

Pac Learing Of One-Dimensional Patterns, Paul W. Goldberg, Sally A. Goldman, Stephen D. Scott

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Developing the ability to recognize a landmark from a visual image of a robot's current location is a fundamental problem in robotics. We consider the problem of PAC-learning the concept class of geometric patterns where the target geometric pattern is a configuration of k points on the real line. Each instance is a configuration of n points on the real line, where it is labeled according to whether or not it visually resembles the target pattern. To capture the notion of visual resemblance we use the Hausdorff metric. Informally, two geometric patterns P and Q resemble each othe runder the …

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A Survey Of Network Signaling, Dakang Wu Jan 1995

A Survey Of Network Signaling, Dakang Wu

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Abstract Network signaling is the process of transferring control information among components of a communication network to establish, maintain, and release connections, and to pass the network management information. The rapid evolution in the field of telecommunications has led to the rapid evolution of network signaling. In this paper, we review the evolution of network signaling. We emphasize the concepts and protocols used in modern fast packet switching networks especially in emerging ATM networks.

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Reasoning About Program Interactions In The Presence Of Mobility, Gruia-Catalin Roman, Peter J. Mccann Jan 1995

Reasoning About Program Interactions In The Presence Of Mobility, Gruia-Catalin Roman, Peter J. Mccann

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Mobile computing is emerging as an important new paradigm which has the potential to reshape our thinking about distributed computation. Mobility has far-reaching implications on what designers and users can assume about communication patterns, resource availability, and applciation behaviors as components move from one location to another while joining or leaving groups of other components in their vicinity. New distributed algorithms are likely to be required as the nature of applications shifts with the emergence of this new kind of computing environment. Formal methods have an important role to play in the midst of these developments both in terms of …

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A Single-Stroke Orientation-Orient Gesture System, Yike Hu Jan 1995

A Single-Stroke Orientation-Orient Gesture System, Yike Hu

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No abstract provided.

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An Interactive Model Of Teaching, H. David Mathias Jan 1995

An Interactive Model Of Teaching, H. David Mathias

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Previous teaching models in the learning theory community have been batch models. That is, in these models the teacher has generated a single set of helpful examples to present to the learner. In this paper we present an interactive model in which the learner has the ability to ask queries as in the query learning model of Angluin [1]. We show that this model is at least as powerful as previous teaching models. We also show that anything learnable with queries, even by a randomized learner, is teachable in our model. In all previous teaching models, all classes shown to …

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Aras: Asynchronous Risc Architecture Simulator, Chia-Hsing Chien, Mark A. Franklin, Tienyo Pan, Prithvi Prabhu Jan 1995

Aras: Asynchronous Risc Architecture Simulator, Chia-Hsing Chien, Mark A. Franklin, Tienyo Pan, Prithvi Prabhu

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In this paper, an asynchronous pipeline instruction simulator, ARAS is presented. With this simulator, one can design selected instruction pipelines and check their performance. Performance measurements of the pipeline configuration are obtained by simulating the execution of benchmark programs on the machine architectures developed. Depending on the simulation results obtained by using ARAS, the pipeline configuration can be altered to improve its performance. Thus, one can explore the design space of aynchronous pipeline architectures.

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Assertional Reasoning About Pairwise Transient Interactions In Mobile Computing, Gruia-Catalin Roman, Peter J. Mccann, Jerome Plun Jan 1995

Assertional Reasoning About Pairwise Transient Interactions In Mobile Computing, Gruia-Catalin Roman, Peter J. Mccann, Jerome Plun

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Mobile computing represents a major point of departure from the traditional distributed computing paradigm. The potentially very large number of independent computing units, a decoupled computing style, frequent disconnections, continuous position changes, and the location-dependent nature of the behavior and communication patterns of the individual components present designers with unprecedented challenges in the areas of modularity and dependability. This paper describes two ideas regarding a modular approach to specifying and reasoning about mobile computing. The novelty of our approach rests with the notion of allowing transient interactions among programs which mobe in space. In this paper we restrict our concert …

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Transient Data Sharing Among Mobile Programs, Jerome Plun, Gruia-Catalin Roman Jan 1995

Transient Data Sharing Among Mobile Programs, Jerome Plun, Gruia-Catalin Roman

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Mobile computing represents a major point of departure from the traditional distributed computing paradigm. The potentially very large number of independent computing units, a decoupled computing style, frequent disconnections, continuous position changes, and the location-dependent nature of the behavior and communication patterns present designers with unprecedented challenges in the areas of modularity and dependability. This paper describes a modular approach to specifying and reasoning about of mobile computing. Its novelty rests with the notion of allowing transient (location-dependent) data sharing among programs which move in space. The notation is a direct extension of that used in UNITY and reasoning about …

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Real-Time Upcalls: A Mechanism To Provide Real-Time Processing Guarantees, Raman Gopalakrishna, Guru M. Parulkar Jan 1995

Real-Time Upcalls: A Mechanism To Provide Real-Time Processing Guarantees, Raman Gopalakrishna, Guru M. Parulkar

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Real-time upcalls (RTUs) are an operating systems mechanism that can be used by applications to efficiently schedule code segments (or handlers) that must execute periodically. While the mechanism was conceibed to support protocol processing with quality-of-service guarantees for networked multimedia applicatoins it is general enough to be applicable in other domains like real-time image processing. Until now real-time threads have been the only mechanism for implementing protocols in user space with QoS guarantees. The RTU mechanism avoids the implementation complexity of the thread based approach while retaining its ability to ensure real-time behavior. In addition, our design simplifies protocol code, …

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Load Balance Properties Of Distributed Data Layouts For Clustered Mod Servers, Milind M. Buddhikot, Guru Parulkar Jan 1995

Load Balance Properties Of Distributed Data Layouts For Clustered Mod Servers, Milind M. Buddhikot, Guru Parulkar

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Large scale storage servers that provide location transparent, interactive access to hundreds or thousands of concurrent, independent clients will be important components of hte furture information super-highway infrastructure. Two key requirements of such servers are as follows: support high parallelism and concurrency in data access to allow large number of access to the same or different data. Second, support independent interactive playout control operations such as fast-forward, rewind, slow-play, pause, resume, random access etc. with minimal latency. This paper assumes a distributed storage server architecture consisting of several high performance storage nodes interconnected by a high speed desk area network …

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