Showing papers on "Server published in 1993"

System to facilitate efficient utilization of network resources in a computer network

Abstract: In a method and system for monitoring the performance of servers across a network and for suggesting an appropriate server to a client requesting a service, a plurality of probes are placed in various clients in the network by a Broker-Performance Mechanism. The probes request that the servers perform various network functions and measure the response times of the servers in satisfying those requests. The Broker-Performance Mechanism retrieves, analyzes, and stores the response time data. The stored data can be made available to a user for system diagnostic purposes. In addition, when a particular client requests a particular service, the Broker-Performance Mechanism examines the analyzed data and determines which server is best suited, at that particular time, to provide the requested service to the requesting client.

Designing a multiuser HDTV storage server

Abstract: The authors present a quantitative study of designing a multiuser HDTV server, and they present efficient techniques for storing multiple HDTV videos on disk and servicing multiple subscriber requests simultaneously, both under the constraint of guaranteeing HDTV playback rates. They develop a model that relates disk and device characteristics to the HDTV playback rate and derive a storage pattern for HDTV video streams that guarantees their real-time retrieval. Given multiple HDTV streams, mechanisms for merging their individual storage patterns are developed. Merging algorithms that yield a large improvement in space utilization over storing each of the streams independently are proposed. Policies such as round robin and quality proportional for servicing multiple subscribers simultaneously are studied. These studies provide a quantitative demonstration of the technological feasibility and economic viability of HDTV-on-demand servers on metropolitan area networks (MANs). >

Internet Relay Chat Protocol

Abstract: The IRC protocol was developed over the last 4 years since it was first implemented as a means for users on a BBS to chat amongst themselves. Now it supports a world-wide network of servers and clients, and is stringing to cope with growth. Over the past 2 years, the average number of users connected to the main IRC network has grown by a factor of 10.

System for processing handwriting written by user of portable computer by server or processing by the computer when the computer no longer communicate with server

Abstract: A computer arrangement that offloads computationally intensive tasks from portable computer devices to larger servers is disclosed. A portable computer device that relies on handwriting or speech for input is equipped with a wireless communication subsystem. When a user writes on the display or speaks into the portable computer device, the central processing unit passes the handwriting or speech information to the wireless communication subsystem. While the user is still inputting information, the wireless communication subsystem transmits received information to a communication server. The communication server routes the handwriting or speech information to a server that performs handwriting or speech recognition to translate the information into encoded text. The communication server then transmits the encoded text information back to the portable computer device.

LH: Linear Hashing for distributed files

Abstract: LH* generalizes Linear Hashing to parallel or distributed RAM and disk files. An LH* file can be created from objects provided by any number of distributed and autonomous clients. It can grow gracefully, one bucket at a time, to virtually any number of servers. The number of messages per insertion is one in general, and three in the worst case. The number of messages per retrieval is two in general, and four in the worst case. The load factor can be about constant, 65-95%, depending on the file parameters. The file can also support parallel operations. An LH* file can be much faster than a single site disk file, and/or can hold a much larger number of objects. It can be more efficient than any file with a centralized directory, or a static parallel or distributed hash file.

Automated System Monitoring and Notification With Swatch

Abstract: This paper describes an approach to monitoring events on a large number of servers and workstations. While modern UNIX systems are capable of logging a variety of information concerning the health and status of their hardware and operating system software, they are generally not configured to do so. Even when this information is logged, it is often hidden in places that are either not monitored regularly or are susceptible to deletion or modification by a successful intruder. Also, a system administrator must often monitor several, perhaps dozens, of systems. To address these problems, our approach begins with the modification of certain system programs to enhance their logging capabilities. In addition, our approach calls for the logging facilities on each of these systems to be configured in such a way as to send a copy of the critical system and security related information to a dependable, secure, central logging host system. As one might expect, this central log can see a megabyte or more of data in a single day. To keep a system administrator from being overwhelmed by a large quantity of data we have developed an easily configurable log file filter/monitor, called swatch. Swatch monitors log files and acts to filter out unwanted data and take one or more user specified actions (ring bell, send mail, execute a script, etc.) based upon patterns in the log.

Tour/schedule generation for a force management system

Abstract: A method for planning, scheduling and managing personnel in an environment in which there is a varying workload by time of day and by day of week to be staffed with a team having a variable number of servers. The method defines one or more tour templates, each describing a bounded work shift having work rules and operating constraints. Per-server preferences for particular kinds of work schedules within the limits imposed by the tour templates are also defined, as are various selection policy rules for determining which servers work when the number of servers exceeds the demand therefor. After generating a forecast of an event load expected to occur during a forecast time period and a number of servers required to service the expected event load during the forecast time period, the method correlates the tour templates with the forecast to generate a set of optimal tours, each tour defining a daily work schedule for the forecast time period for a theoretical server. Then, the individual servers are automatically scheduled to the generated tours according to the preferences and the selection policy rules.

Increasing availability and security of an authentication service

Abstract: Authentication, the process by which one satisfies another about one's claim of identity, is typically provided by an authentication server via an authentication protocol. Compromise of the authentication service can lead to the compromise of the whole system, and the service is a performance bottleneck because many activities cannot proceed unless the identities of concerned parties can be satisfactorily established. Therefore, a desirable authentication service should be both highly secure and highly available. A general solution in which the authentication server is replicated so that a minority of malicious and colluding servers cannot compromise security or disrupt service is proposed. Some unusual features of such a distributed authentication service, including the tradeoff between availability and security, are discussed. Such a distributed service is also useful when clients cannot identify or agree upon trusted servers prior to authentication. For example, in some cooperative or federated systems, clients simply cannot all trust the same set of servers. >

Video application server

Abstract: A local area network for supporting video applications comprises a transmission medium, one or more data file servers connected to the transmission medium for supporting data applications in the local area network, a dedicated video server for supporting video applications in the local area network and one or more clients connected to the local area network. The server includes software for managing multiple simultaneous video streams transmitted across the LAN. The client includes software for accessing the dedicated video server across the LAN to transmit video to the server or receive video from the server.

How Networks Work

Abstract: From the Book: More than 80 percent of the personal computers used in business and education are connected to a network or the Internet. The chances are good that you'll have to interact with a network soon if you don't already. This book helps you understand computer networks in several ways. It helps to scratch the intellectual itch you might have about where the data resides and what goes on inside the cable, equipment, and software. If you understand the basic structure and operation of a network, you can be more efficient in your job. The information in this book is an excellent foundation for growth if you want to learn more about networking. Finally, you can use this book as a training tool for working on networked computers. Computer networking didn't just emerge as a unique and independent technology. Networking depends on many things you've seen or are familiar with already. In fact, modern networks have roots in the early telegraph and telephone systems. In this book, we take advantage of those historical ties to explain and illustrate the underlying technology of networks in a simple graphic format. Then, we move into modern networking and explain the relationships between the hardware and software in networks. Our illustrations detail packets, network interface cards, servers, routers, management software, and many other aspects of networking. Our constant goal is to provide useful information in an easily understood manner. The information in this book isn't specific to any particular type of computer or network operating system. We illustrate models of operation and tell you how some popular products fit into the models. Whether your computer is an IBM PC, DEC VAX, or anApple Macintosh; whether your network operating system is NetWare, LANtastic, or UNIX; and whether your cabling is copper or fiber-optic, the information in this book applies to your network.

Method and apparatus for allocating server access in a distributed computing environment

Abstract: In a distributed computing environment (DCE), a scheduler process executes on every DCE processor. The schedulers mediate all remote procedure calls (RPCs) made by client processes to server processes using a scheduler and/or namespace accessible by the DCE processor. The scheduler database stores interfaces of single-thread servers, and the namespace stores interfaces of multi-thread servers. The scheduler, in response to receiving an identity of an interface from a client process searching the scheduler database and namespace to locate the interface. Upon locating the interface, the interface is provided to the client process so that client and server processes can be bound.

A case for caching file objects inside internetworks

Abstract: This paper presents evidence that several, judiciously placed file caches could reduce the volume of FTP traffic by 42%, and hence the volume of all NSFNET backbone traffic by 21%. In addition, if FTP client and server software automatically compressed data, this savings could increase to 27%. We believe that a hierarchical architecture of whole file caches, modeled after the existing name server's caching architecture, could become a valuable part of any internet.We derived these conclusions by performing trace driven simulations of various file caching architectures, cache sizes, and replacement policies. We collected the traces of file transfer traffic employed in our simulations on a network that connects the NSFNET backbone to a large, regional network. This particular regional network is responsible for about 5 to 7% of NSFNET traffic.While this paper's analysis and discussion focus on caching for FTP file transfer, the proposed caching architecture applies to caching objects from other internetwork services.

Design and Implementation of DDH: A Distributed Dynamic Hashing Algorithm

Abstract: DDH extends the idea of dynamic hashing algorithms to distributed systems. DDH spreads data across multiple servers in a network using a novel autonomous location discovery algorithm that learns the bucket locations instead of using a centralized directory.

System for automatically generating efficient application - customized client/server operating environment for heterogeneous network computers and operating systems

Abstract: A high level virtual computer in a heterogeneous hardware and software environment. A user specifies the hardware and software configuration of a virtual computer employing multiple coarse grain single instruction, multiple data (SIMD); multiple instruction, multiple data (MIMD); and pipelined parallel computing elements into a configurator, which activates a distributed process controller and supporting components in the desired virtual computer. Each processor in the virtual computer is equipped with a language injection library and runtime servers, i.e. daemons. The language injection library facilitates transference of data among the processors in the system during the execution of an application program, and isolates the details of coordinating the heterogeneous hardware and software in the virtual computer.

An Access Control Protocol, Sometimes Called TACACS

Abstract: This RFC documents the extended TACACS protocol use by the Cisco Systems terminal servers. This same protocol is used by the University of Minnesota's distributed authentication system. This memo provides information for the Internet community. It does not specify an Internet standard.

Internetworking with TCP/IP vol. III: client-server programming and applications

Abstract: This is the Second Edition of Vol. III BSD Socket Version from one of the most popular TCP/IP Internetworking series ever published. This new edition includes code in ANSI C throughout. This is the only book available who's central theme is software design that teaches designers how to structure clients and servers. The server designs are directly applicable to WWW and other applications. The authors present the most complete coverage of server technology that allows designers to understand the costs and benefits of advanced server technologies. In addition, the Second Edition discusses the use of application gateways to allow client-server communication across heterogeneous protocols.

Handling mobile clients: a case for indirect interaction

Abstract: Networking protocols are being modified to handle mobility of hosts. This paper argues that there is a need to make mobility explicit at every level of the OSI model - even above the network level through user or application level. Further, it is proposed that the mobile host and the first hop (wireless link) of communication be handled differently than the rest of the network. Hence, in networks with mobile hosts, we propose a radical approach of indirect interaction between clients and servers. >

Feedback Techniques for Intra-Media Continuity and Inter-Media Synchronization in Distributed Multimedia Systems

Abstract: Future advances in networking and storage will make it feasible to build multimedia on-demand servers that provide services similar to those of a neighbourhood videotape rental store over metropolitan area networks such as B-ISDN. Such multimedia servers can support real-time retrieval of multimedia objects by users onto their ISDN videophones and audiophones for playback. The design of techniques and protocols for providing continuous and synchronous access to multimedia services constitutes the subject matter of this paper

ActorSpace: an open distributed programming paradigm

Abstract: We present a new programming paradigm called ActorSpace. ActorSpace provides a new communication model based on destination patterns. An actorSpace is a computationally passive container of actors which acts as a context for matching patterns. Patterns are matched against listed attributes of actors and actorSpaces that are visible in the actorSpace. Both visibility and attributes are dynamic. Messages may be sent to one or all members of a group defined by a pattern. The paradigm provides powerful support for component-based construction of massively parallel and distributed applications. In particular, it supports open interfaces to servers and pattern-directed access to software repositories.

Detection and resolution of resource deadlocks in a distributed data processing system

Abstract: A distributed data processing system includes a distributed resource manager which detects dependencies between transactions caused by conflicting lock requests. A distributed transaction manager stores a wait-for graph with nodes representing transactions and edges connecting the nodes and representing dependencies between the transactions. Each edge is labelled with the identities of the lock requests that caused the dependency. The distributed transaction manager propagates probes through the wait-for graph, to detect cyclic dependencies, indicating deadlock. A deadlock message is then sent to the resource manager identifying a particular lock request as a victim for deletion to resolve the deadlock. Resilience to failure is achieved by duplicating between agents and servers, rather than by duplicating the servers. As a result, the number of messages between agents and servers in normal operation is not increased.

The role of alcohol providers in prevention: an evaluation of a server intervention programme

Abstract: Server intervention is a relatively new approach in the attempt to reduce the incidence of drinking and driving. Although a number of evaluations have suggested that the approach may be effective, there have been few comprehensive evaluations of such programmes. The present study utilized process evaluation techniques to assess reactions to a programme developed by the Addiction Research Foundation, and a quasi-experimental design to determine the impact of the programme on the serving practices of servers. Actors portrayed behaviours often faced by servers, and observers rated the reactions of the servers, who were unaware of the simulations, to these situations. The programme appears to have been effective in changing behaviour, in that trained servers exhibited less inappropriate responses than did untrained servers. In addition the results suggested that the programme increased servers' knowledge about their obligations and potential strategies for dealing with these situations. The implications of these findings for future implementations of such programmes are discussed.

Client/server communication system utilizing a self-generating nodal network

Abstract: Method for building a self-generating nodal network for communicating in a client/server system wherein the method includes the steps of creating a server nodal network tree which includes the steps of generating a server root node which includes both process steps for communicating to an operating system and service nodes, and process steps for building service nodes which correspond to servers within the client/server system, each service node includes both process steps for advertising a service to the server root node and process steps for building a topic node which includes both process steps for accessing a server and process steps for building a job node for storing a job request. The method also includes the step of creating a client nodal network tree which includes the steps of generating a client root node which includes both process steps for communicating to an operating system and client service nodes, and process steps for building client service nodes corresponding to each service node of the server nodal network tree, each client service nodes includes both process steps for communicating to an application program and process steps to create a job request in accordance with a job request designated by the application program, wherein the client service node is receiving a job request from the application program propagates the request back through the client nodal network tree to the server nodal network tree for execution.

Method and apparatus for delegated communications in a computer system using trusted deputies

Abstract: An apparatus and a method are disclosed whereby a client application can use a trusted "Deputy" application to execute operation calls on several servers on behalf of the client, the Deputy application being able to convince the servers that the deputy application is representing the original client application, and the client thereby reducing the risk of being contaminated by uncontrolled access to an unknown server, while at the same time being able to obtain the desired processing results regardless of the number or location of servers involved in providing the results. The Deputy application is authenticated by the server as representing a user, not a user on a predetermined workstation or as a predetermined member of a particular work group.

Method and apparatus providing for hunt groups in an ATM network of the like

Abstract: An asynchronous transfer mode (ATM) network or the like providing for formation of resource hunt groups. The hunt groups are formed by devices of the same class (e.g., servers such as multicast servers) by devices registering with a central management supervisor (also referred to herein as a hunt group manager) through communication of hunt group registration requests over the virtual service path of the switches to which devices are attached. The central management supervisor communicates with an acknowledgement message back to the requesting device, again over the virtual service path. After formation of a hunt group, devices requiring the services of a device registered in the hunt group can communicate a request for establishment of a communication path to the central management supervisor. The central management supervisor then establishes a communication path with an available one of the devices in the hunt group.

The Shark continuous-media file server

Abstract: Shark, a network file server for digital video and other continuous media data being developed at the IBM Almaden Research Center, is described. The high data rate and stringent time constraints of real-time video place heavy demands on a file server, and Shark implements a variety of novel features that enable it to efficiently handle video data. The Shark server runs on an RS/6000 workstation; implementations of the Shark client run on both AIX and OS/2. >

A store-and-forward architecture for video-on-demand service

Abstract: The authors present store-and-forward architecture that can provide video-on-demand (VOD), as well as other data-based services. They assume a B-ISDN network to be in place. The four major elements in this architecture are the information provider warehouse (IPw) where video material is archived; the central office (CO) server which contains a processor responsible for the service management and a video buffer that interacts directly with network customers; and, finally, the customer premise equipment. A requested video program is provided in a real-time fashion from the CO server to the customer. However, at the information provider, the video program is retrieved from the archival storage in blocks, and with transfer rates much faster than real time. Subsequently, it is sent in a bursty mode to the CO servers via high-speed trunks.

Multimedia network file servers: multi-channel delay sensitive data retrieval

Abstract: Delay sensitive media such as audio and video are becoming integrated in the standard user interface. In this paper we consider simultaneous multiple access, such as would be performed by a multimedia network file server. To simplify the discussion, we consider only audio retrieval. The extension to storage and other delay sensitive data types is straightforward. This paper builds on the necessity of avoiding starvation of the consumer, and the assumption that certain sets of reads lead to a net increase in the number of samples buffered, to establish a theoretical framework for studying simultaneous multiple access. Our approach allows the possibility of splitting data into sorting sets for the purpose of reducing disk latencies, and gives an optimal algorithm for the reduction. It explicitly handles both contiguous and non-contiguous file layouts. Lower bounds on read amounts and buffer requirements are proved. Using the theoretical framework, designers can evaluate the approach that is best suited to their situation.

Adaptation of geographic information systems for transportation

Abstract: This report documents and presents a top-level design and implementation plan for geographic information systems (GISs) for transportation. The basis for the design and implementation plan has been first an assessment of the current state of the art of GIS for transportation (GIS-T) through interviews with DOTs and MPOs and through a survey of GIS vendors, and second a projection of technological developments through the next five to ten years. A GIS-T may be thought of as a union of a GIS and a transportation information system, with enhancements to the GIS software and to the transportation data. A central significance of GIS-T technology is in its potential to serve as the long-sought data and systems integrator for transportation agencies. Given that so many transportation data are or can be geographically referenced, the GIS-T enabled and managed concept of location provides a basis for integrating databases and information systems across almost all transportation agency applications. In order to realize the greatest benefits of GIS-T, DOTs should develop agency-wide strategic plans that comprehend not only GIS technology adoption and application, but also concurrent adoption and application of open-systems standards and of a wide range of imminent complementary technologies, from computer networking and distributed computing, through new data storage media and database architectures, through computer-aided software engineering, to computer-based graphics and computer-aided design. The plans should address a full range of application scales, because GIS has the potential to become ubiquitous throughout all functional areas of transportation agencies. The recommended approach is top down for system design, then bottom up for application development. A GIS-T server-net architecture with computational and data management labor divided among different kinds of servers is recommended. (Fifteen kinds are suggested as a plausible first iteration for the required design.) Implementation of the server net can be incremental with a conceptual architecture in place as an organizing principle before complete physical realization is feasible, just as the concept of location can serve as a conceptual integrator for data schemas before the GIS enabled and managed spatial databases required for actual integration are fully available and as they are being incrementally constructed.

Online load balancing and network flow

Abstract: In this paper we study two problems that can be viewed as on-line games on a dynamic bipartite graph. The first problem is on-line load balancing with preemption. A centralized scheduler must assign tasks to servers, processing on-line a sequence of task arrivals and departures. Each task is restricted to run on some subset of the servers. The scheduler attempts to keep the load well-balanced. If preemptive reassignments are disallowed, Azar et al. [3] proved a lower bound of Ω(n1/2) on the ratio between the maximum load achieved by an on-line algorithm and the optimum off-line maximum load. We show that this ratio can be greatly reduced by an efficient scheduler using only a small amount of rescheduling.