Showing papers on "Heterogeneous network published in 1996"

System for pacing data communications in between adjacent communications managers having different network protocol stacks in a distributed heterogeneous communications network

Abstract: A data communication method and apparatus is presented that allows communication in a distributed heterogeneous network. Communications managers reside in local processing environments and are responsible for interfacing local end users with the remainder of the heterogeneous network. Each communications manager receives distribution units from end users, the distribution units being assigned various priority levels and levels of assurance. Within each communications manager, an adjacent communications manager is determined in accordance with a communications path to a destination for the distribution unit. The distribution unit is then configured according to a network protocol stack existing between the communications manager and the adjacent communications manager, and the distribution units are transmitted according to priority. Each communications manager can have any number of adjacent communications managers each communicating through different network protocol stacks. Also described is load distribution among a complex of processors that share common functions, as well as control of information flow between adjacent communications managers.

Scalable compression and transmission of internet multicast video

Abstract: In just a few years the "Internet Multicast Backbone", or MBone, has risen from a small, research curiosity to a large scale and widely used communications infrastructure. A driving force behind this growth was our development of multipoint audio, video, and shared whiteboard conferencing applications that are now used daily by the large and growing MBone community. Because these real-time media are transmitted at a uniform rate to all the receivers in the network, the source must either run below the bottleneck rate or overload portions of the multicast distribution tree. In this dissertation, we propose a solution to this problem by moving the burden of rate-adaptation from the source to the receivers with a scheme we call Receiver-driven Layered Multicast, or RLM. In RLM, a source distributes a hierarchical signal by striping the constituent layers across multiple multicast groups. Receivers then adjust their reception rate by simply joining and leaving multicast groups. But RLM solves only half of the problem. To distribute a multi-rate flow to heterogeneous receivers using RLM, the underlying signal must be encoded in a hierarchical or layered format. To this end, we developed and present herein a layered video compression algorithm which, when combined with RLM, provides a comprehensive solution for scalable multicast video transmission in heterogeneous networks. In addition to a layered representation, our coder has low-complexity (admitting an efficient software implementation) and high error resilience (admitting robust operation in loosely controlled environments like the Internet). Our RLM/PVH framework leverages two design methodologies from two related yet often segregated fields: joint source/channel coding (JSCC) from traditional communications theory and application level framing (ALF) from computer network design. In accordance with JSCC, we combine the design of the source-coding algorithm (i.e., PVH) with the channel-coding algorithm (i.e., RLM), while in accordance with ALF, we reflect application semantics (i.e., PVH) in the design of the network protocol (i.e., RLM). In this thesis, we posit that JSSC and ALF are two manifestations of the same underlying design principle. We explore the ALF/JSSC design space with a discussion of our "Intra-H.261" video coder, which we developed specifically for MBone video transmission, and compare its performance to that of traditional designs based on independent source- and channel-coding. Finally, we bring all of the pieces of our design together into a comprehensive system architecture realized in a flexible software toolkit that underlies our widely used video application--the UCB/LBL video conferencing tool vic. Our system architecture not only integrates RLM and PVH into an autonomous video application but also provides the functionality requisite to a complete multimedia communication system, including user-interface elements and companion applications like audio and shared whiteboard. In this framework, we craft "media agents" from a common multimedia toolkit and control and configure them over a software interprocess communication bus that we call the Coordination Bus. By composing an arbitrary arrangement of media agents over the Coordination Bus and complementing the arrangement with an appropriate user-interface, we can induce an arbitrary multimedia collaboration style. Unlike previous work on layered video compression and transmission, we have implemented RLM, PVH, and our coordination framework in a "real" application and are deploying a fully operational system on a very large scale over the MBone. (Abstract shortened by UMI.)

Method and apparatus for increasing the effective band width of a digital wireless network

Abstract: A plurality of devices communicate information over a wireless network at radio frequencies. The information includes digital audio, video and data. Bandwidth among the devices is dynamically allocated, the allocation being based upon the needs of the devices. One embodiment of the wireless network is a Time Division Multiple Access network. Another embodiment is a wireless Ethernet. Yet another embodiment is a Frequency Division Multiplexed network.

Seamless access to multiple wireless data networks. A wireless data network infrastructure at Carnegie Mellon University

Abstract: In order to support mobile computing research, including the development of software which will allow seamless access to multiple wireless data networks, a wireless data network infrastructure is being built at Carnegie Mellon University. This infrastructure will allow researchers and other members of the campus community to use mobile computers to gain access to data networks while they are on-campus, or off-campus in the greater Pittsburgh area. The infrastructure will initially include two different types of wireless networks, a low-bandwidth wide area system and a high-bandwidth local area system, each of which will provide access to the campus computer network. Since the campus network is called "Andrew" (after Andrew Carnegie and Andrew Mellon), the new wireless infrastructure has been dubbed "Wireless Andrew". The article describes the Wireless Andrew infrastructure being built. An overview of the infrastructure and the characteristics of the two types of wireless networks used are presented. Each of these networks is then described in more detail. The technology used, its implementation in the wireless network infrastructure, and deployment experience are discussed.

Handling mobility in a wireless ATM network

Abstract: The world of wireless telecommunications is rapidly changing. The capabilities of wireless networks are improving at a steady pace. This paper presents a protocol implementation for providing mobility in an asynchronous transfer mode (ATM) network. The vision of the authors is of one "ATM-based wireless telecommunications network" that is capable of supporting a variety of today's applications with room to grow for advanced applications of the future. The next generation wireless networks are called personal communication services (PCS) networks and will provide for global user mobility, a life-long user identification numbering system and the ability to accommodate varying data rates.

ECO: Efficient Collective Operations for communication on heterogeneous networks

Abstract: PVM and other distributed computing systems have enabled the use of networks of workstations for parallel computation, but their approach of treating all networks as collections of point-to-point connections does not promote efficient communication-particularly collective communication The Efficient Collective Operations (ECO) package contains programs which solve this problem by analyzing the network and establishing efficient communication patterns This paper describes ECO and gives performance results of using ECO to implement the collective communication in CHARMM, a widely used macromolecular dynamics package ECO substantially improves the performance of CHARMM on a heterogeneous network ECO's approach gives a programmer the ability to use the available networks to their full potential without acquiring any knowledge of the network structure

Wireless Data Network Infrastructure at Carnegie Mellon University

Abstract: In order to support mobile computing research, including the development of software which will allow seamless access to multiple wireless data networks, we are building a wireless data network infrastructure at Carnegie Mellon University. This infrastructure will allow researchers and other members of the campus community to use mobile computers to gain access to data networks while they are on-campus or while they are off-campus in the greater Pittsburgh area. The infrastructure will initially include two different types of wireless networks, a low-bandwidth wide area system and a high-bandwidth local area system, each of which will provide access to our campus computer network. Since our campus network is called “Andrew” (after Andrew Carnegie and Andrew Mellon), the new wireless infrastructure has been dubbed “Wireless Andrew.” This article describes the Wireless Andrew infrastructure we are building. We begin with an overview of the infrastructure and the characteristics of the two types of wireless networks we are using. Next, we describe in more detail each of these networks. We discuss the technology used, our implementation of it in our wireless network infrastructure, and our current deployment experience. Finally, we summarize the lessons we have learned and present conclusions.

Hierarchical video distribution over Internet-style networks

Abstract: IP-based networks such as the Internet traverse paths of widely ranging bandwidths and load factors. Several investigators have proposed the use of hierarchical video as a solution for dissemination of video across heterogeneous networks of this sort. In particular, such approaches avoid some the "least common denominator" problems inherent in single-layer heterogeneous multicast. We describe an experimental video delivery system that makes use of several new Internet technologies such as the resource reservation protocol (RSVP), integrated services (IntServ), the realtime transport protocol (RTF) and the IP multicast to control the dissemination of a hierarchical media streams across heterogeneous IP multicast networks.

A survey of heterogeneous computing: concepts and systems

Abstract: This survey of heterogeneous computing concepts and systems is based on the recently proposed by the authors "EM/sup 3/ " (Execution Modes/Machine Models) taxonomy of computer systems in general. The taxonomy is based on two criteria: the number of execution modes supported by the system and the number of machine models present in the system. Since these two criteria are orthogonal, four classes exist: Single Execution mode/Single machine Model (SESM), Single Execution modes/Multiple machine Models (SEMM), Multiple Execution modes/Single machine Model (MESM), and Multiple Execution modes/Multiple machine Models (MEMM). In Section II, heterogeneous computing concepts are viewed through three phases of the compilation and execution of any heterogeneous application: parallelism detection, parallelism characterization and resource allocation. Parallelism detection phase discovers fine-grain parallelism inside every task. This phase is not an exclusive feature of heterogeneous computing, so it will not be dealt with in greater detail. The assignment of parallelism characterization phase is to estimate the behavior of each task in the application on every architecture in the heterogeneous system. In the parallelism characterization domain, one original taxonomy is given. This taxonomy contains scheme classes such as vector and matrix static and dynamic, implicit and explicit, algorithmic and heuristic and numeric and symbolic. Resource allocation phase determines the place and the moment for execution of every task to optimize certain performance measure related to some criteria. In the resource allocation domain, the existing Casavant-Kuhl taxonomy is extended and used. This well known taxonomy is supplemented with scheme classes such as noncooperative competitive, noncooperative noncompetitive, and load sharing. In Section III, heterogeneous systems characterized with multiple execution modes ("fully" heterogeneous systems falling in the MESM and the MEMM class) are surveyed. The MESM class systems are described and illustrated with three case studies, two of which support SIMD/MIMD and one supports scalar/vector combination of execution modes. The MEMM class systems are described and illustrated with two representative examples of fully heterogeneous networks supporting multiple execution modes. The system software for heterogeneous computing systems is presented according to an original three-dimensional (3-D) taxonomy whose criteria rely on the level of heterogeneity support implementation, the programming approach, and the data access technique applied. In Section III, several representative heterogeneous applications are described with their computation requirements and the systems used for their execution. Each topic covered in the paper contains several concise examples.

Autonomous and Adaptive Agents that Gather Information

Abstract: We have designed and implemented autonomous software agents. Our agents are programs that can move independently through a heterogeneous network of computers. They can sense the state of the network, monitor software conditions, and interact with other agents. The network-sensing tools allow our agents to adapt to the network configuration and to navigate under the control of reactive plans. In this paper we illustrate the intelligent and adaptive behavior of autonomous agents in distributed information-gathering tasks.

A wireless network in MosquitoNet

Abstract: An emerging technology for wireless connectivity provides one of the best combinations of bandwidth, coverage area, and cost for a wireless data network. It also teaches important lessons about software-hardware interface design. To support this vision of ubiquitous connectivity, we are studying issues of wireless and mobile computing at the network, system, and application levels. Our two main goals are to provide seemingly continuous connectivity for mobile hosts, and to support system- and application-level adaptation to dynamically changing network characteristics. We are investigating changes and extensions to standard networking application program interfaces (APIs) that will allow well-written applications to deal gracefully with widely varying network characteristics. When switching between available services, network characteristics can change significantly, even while an application is running.

Economic-Based Dynamic Load Distribution in Large Workstation Networks

Abstract: Dynasty is a scalable hierarchical system for dynamic load distribution of general divide&conquer applications on large heterogeneous networks of workstations. It is based on economical principles with prices as the basic instrument for regulating offer and demand. The performance of Dynasty is evaluated by a Finite Element application running on up to 96 workstations.

Retrieving quality video across heterogeneous networks. Video over wireless

Abstract: The article addresses the issues that arise in delivering video across Wireless Andrew. Wireless Andrew is the Carnegie Mellon University (CMU) heterogeneous networking environment. It interconnects wideband and narrowband wireless and wired networks using off-the-shelf technologies. The authors design a video system where video servers distributed across the network deliver, upon request, video clips to clients scattered around the campus. The main novelty of the article is generative video (GV), a content-based meta representation for video that is well suited for the heterogeneous dynamic environment of Wireless Andrew. GV provides a framework for graceful degradation as end-to-end network throughput varies. GV reduces the video sequence to a small set of still images and side information needed to reconstruct the original sequence. The authors have demonstrated for three real live video sequences that GV delivers compression ratios in the range of 1000-10000 with good perceptual quality They develop a scalable implementation for the GV coder/decoder (codec). Scalability coding avoids duplicating the encoding of each video clip when servicing a wide range of throughputs, as in heterogeneous networks. They discuss the video delivery requirements, the video system architecture, the system implementation, and the trade-offs needed to ensure graceful degradation under real-life network operating conditions.

Providing video conferencing for the mobile user

Abstract: This paper describes how video conferences can be provided across fixed and mobile networks. Using video conference systems employed today on fixed networks as a starting point, solutions are proposed how to extend these services to cover the requirements imposed by wireless networks. A layered architecture of an appropriate video mobility gateway is described which allows the transmission of video streams in heterogeneous networks comprising wireless and wired subnetworks.

Digital video in a fading interference wireless environment

Abstract: Much research and development related to digital video has targeted storage, wired backbone, and broadcast wireless transport environments. We address video transport in a heterogeneous network, especially with interference- and fading dominated wireless access, such as a cellular local-area or wide-area network. It is expected that multimedia (including video) will be an important application for desktop computers, and this suggests offering similar wireless capabilities. We note a number of deficiencies in existing video compression standards such as MPEG for this environment, and identify a number of challenging new research issues.

Network architecture for mobile and wireless ATM

Abstract: There is an emergent interest in providing mobile users with ubiquitous wireless access to multimedia information. In this paper we present a network architecture and protocols to achieve this goal and describe their implementation in a prototype network called SWAN. Our network model assumes end to end ATM connectivity. Thus, the key question we address is how best to enhance ATM to support host mobility and wireless access.

Transparent fault tolerance for parallel applications on networks of workstations

Abstract: This paper describes a new method for providing transparent fault tolerance for parallel applications on a network of workstations We have designed our method in the context of shared object system called SAM, a portable run-time system which provides a global name space and automatic caching of shared data SAM incorporates a novel design intended to address the problem of the high communication overheads in distributed memory environments and is implemented on a variety of distributed memory platforms Our fundamental approach to providing fault tolerance is to ensure the replication of all data on more than one workstation using the dynamic caching already providedby SAM The replicated data is accessible to the local processor like other cached data, making access to shared data faster and potentially offsetting some of the fault tolerance overhead In addition, our method uses information available in SAM applications on how processes access shared data to enable several optimizations which reduce the fault-tolerance overhead We have built an implementation of our fault-tolerance method in SAM for heterogeneous networks of workstations running PVM3 In this paper, we present our fault-tolerance method and describe its implementation in detail We give performance results and overhead numbers for several large SAM applications running on a cluster of Alpha workstations connected by an ATM network Our method is successful in providing transparent fault tolerance for parallel applications running on a network of workstations and is unique in requiring no global synchronizations and no disk operations to a reliable file server

Parallel processing on heterogeneous networks for GIS applications

Abstract: The use of network-based parallel computing is gaining an increasing popularity for different reasons. Its exploitation depends on the availability of simple but effective methodologies to parallelize applications, and the availability of portable and efficient communication libraries to develop parallel programs. These two items are necessary to obtain performance advantages, and to ensure software portability and reusability. In this paper we present our experience in parallelizing, in a systematic way, a class of Geographical Information Systems applications. We discuss the use of two well-known communication libraries (PVM and Linda). Performance results are also reported.

Mobile wireless data communications system

Abstract: In order for the user to perform a transmission of packet data to a desired communication counterpart on a virtual network across a wireless circuit exchange type network system and a LAN without being bothered by address exchange between an address of a physical network and an address of a virtual network, an exchange (10a) performs an address exchange necessary for establishing a communication channel between the terminal equipments within the system using a conversion table, in a mobile wireless data communication system in which a wireless circuit type network system comprising a wireless mobile station (30a), a wireless connection equipment (20a) and the exchange (10a) is connected to a LAN (40a) through a TA (60a) and a router (50a).

Dynamically reconfigurable wireless communicator

Abstract: A method and apparatus is provided for communicating on a wireless network which offers a selected service In accordance with the method, a wireless communicator is tuned to a first signaling control channel broadcast by a wireless network The first channel identifies one or more services provided over that network This procedure is repeated for successive signaling control channels until a wireless network providing the selected service is identified Once this has been identified, communication is conducted between the wireless communicator and the network

Wireless Networking Handbook

Abstract: From the Publisher: After a complete overview of wireless networking techniques; the Wireless Networking Handbook guides you through the step-by-step process of deploying and supporting wireless networks for maximum mobile use Organizations currently using paper-based methods will save time and effort accessing centralized data using wireless networks This handy resource explores local, metropolitan, and wide area networks (LANs, MANs, and WANs), then takes you through analyzing, implementing, and supporting a wireless network A thorough description of wireless products and vendors rounds out this practical reference to the exciting world of wireless networks!

Infrastructure support for adaptive mobile applications

Abstract: Recent growth in the number and quality of wireless network technologies has led to an increased interest in mobile computing. Furthermore, these technologies have now advanced sufficiently to allow 'advanced applications' to be engineered. Applications such as these are characterised by complex patterns of distribution and interaction, support for collaboration and multimedia data, and are typically required to operate over heterogeneous networks and end-systems. Given these operating requirements, it is the author's contention that advanced applications must adapt their behaviour in response to changes in their environment in order to operate effectively. Such applications are termed adaptive applications. This thesis investigates the support required by advanced applications to facilitate operation in heterogeneous networked environments. A set of generic techniques are presented that enable existing distributed systems platforms to provide support for adaptive applications. These techniques are based on the provision of a QoS framework and a supporting infrastructure comprising a new remote procedure call package and supporting services. The QoS framework centres on the ability to establish explicit bindings between objects. Explicit bindings enable application requirements to be specified and provide a handle through which they can exert control and, more significantly, be informed of violations in the requested QoS. These QoS violations enable the applications to discover changes in their underlying environment and offer them the opportunity to adapt. The proposed architecture is validated through an implementation of the framework based on an existing distributed systems platform. The resulting architecture is used to underpin a novel collaborative mobile application aimed at supporting field workers within the utilities industry. The application in turn is used as a measure to gauge the effectiveness of the support provided by the platform. In addition, the design, implementation and evaluation of the application is used throughout the thesis to illustrate various aspects of platform support.

Practical Experience in the Dangers of Heterogeneous Computing

Abstract: Special challenges exist in writing reliable numerical library software for heterogeneous computing environments. Although a lot of software for distributed memory parallel computers has been written, porting this software to a network of workstations requires careful consideration. The symptoms of heterogeneous computing failures can range from erroneous results without warning to deadlock. Some of the problems are straightforward to solve, but for others the solutions are not so obvious, or incur an unacceptable overhead. Making software robust on heterogeneous systems often requires additional communication.

Scalable video coding over heterogeneous networks

Abstract: Heterogeneous networks mix wired and wireless technologies, exhibiting well over three orders of magnitude of throughputs. Mobility adds the challenge of dynamic abrupt changes in the throughput experienced by a user. We describe in this paper a video service architecture that accommodates these widely different operating environments while providing graceful degradation as conditions change dynamically for mobile users. The video service is designed in the context of CMU's wireless Andrew. Key to our architecture is Generative Video (GV), a meta representation for video sequences. GV reduces video to still images, the world images, and ancillary data. The world images integrate the information about the background and about all moving objects present in the sequence. World images `lossless' compress the video sequence by at least two orders of magnitude. When coupled with spatial compression of these still images, the total compression ratio can easily exceed three orders of magnitude, well beyond the possibilities of current technologies. Scalable encoding of GV reduces to scalable encoding of still images. We discuss three alternatives, frequency scalability, signal to noise ratio scalability, and spatial scalability. We present results with a real video clip of 20 seconds duration, illustrating compression ratios of forty five hundred with acceptable (VHS type) quality. Due to the different nature and role played by the two types of GV data, we choose two transport protocols: TCP/IP for the transmission of the world images, and UDP/IP for the transport of the ancillary data. The paper describes the video system architecture and several design choice and optimizations that improve the overall performance of the video service.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Design and implementation of indirect protocols for mobile wireless environments

Abstract: Host mobility within the largely stationary internetwork has been treated thus far as a routing problem, to be solved entirely within the network layer of the ISO/OSI protocol model. However, mobility of host machines from one attachment point to another affects transport and higher layer protocols as well. In addition, the use of wireless links by mobile computers for attachment to the fixed network infrastructure, gives rise to performance problems due to low bandwidth and high error rates that are typical of wireless environments. The existing network protocols do not provide any mechanism to deal with the problems arising out of host mobility and wireless access. Widespread use of mobile and wireless capable computers is also likely to create a demand for new applications that utilize the mobile user's location for accessing information sources. Applications used in mobile wireless environments may also need to adapt to the changes in the characteristics of the wireless medium. In this dissertation, we consider the problem of supporting distributed applications on mobile wireless computers that need to communicate with peer applications and servers on the wired internetwork. We present the design and implementation of Indirect Protocols, which allow the use of specialized network protocols for the wireless medium and mobile hosts in a way that is backward compatible with the existing protocols used over the wired internetwork. Indirect protocols are based on two key ideas: (i) Special treatment of wireless links and mobile computers in an internetwork and (ii) Use of mobility support routers (MSRs) as multi-protocol intermediaries. Mobility support routers provide the necessary support to ensure inter-operability with the existing wired network protocols. We show that the use of indirection results in improved performance at the transport layer and provides enhanced functionality at the remote procedure call (RPC) layer.

Resource allocation as an evolving strategy

Abstract: The efficient utilization of resources is an issue of essential importance in modern network management. The emergence of increasingly complicated and continuously changing network services requires softer and fuzzier methods in network management. In this paper we demonstrate how evolutionary game theory can be used for an efficient allocation of service requirements onto an ensemble of heterogeneous network components. By incorporating differentiated pricing structures into a system utility function, network agents are encouraged to increase their usage of those components that are presently badly utilized. It is demonstrated how this approach can enhance network utilization significantly. Some new results regarding evolutionarily stable strategies in nonlinear evolutionary games are also reported.

System architecture of a home wireless ATM network

Abstract: Issues concerning the design of a wireless ATM (WATM) network for the home user are described. Low cost, plug-and-play, and flexibility of the system architecture form the cornerstones of this design.

IN in the hybrid broadband network: the intelligent web

Abstract: Explores the role of intelligent networks (INs) in a mega-heterogeneous network. Such a network is built up using a mixture of many different technologies, both for switching user-to-user information and for signalling. The present contribution focusses on the "traditional" public network (i.e. B-ISDN as the next version of PSTN and ISDN), and the upcoming networks getting more and more global attention (i.e. Internet and CATV). Each of the networks has its own history, and was originally intended for its own specific user-group. Hence, there are different architectures used in the different networks, especially for the service-network. All these technologies have the same basic goal: providing connectivity between the end-users of the system. And the more the world's community get access to all these networks, the more important the end-users, and their wishes, are relevant to these networks. This contribution identifies what INs may teach other networks, but also what other networks may teach INs.

Packet video for heterogeneous networks using CU-SeeMe

Abstract: Software based desktop videoconferencing tools are developed to demonstrate techniques necessary for video delivery in heterogeneous packet networks. Pyramidal compression, congestion avoidance, end-to-end delivery, and predictive rate control results are presented.