Showing papers on "Shared resource published in 1987"

Spatial reuse in multihop packet radio networks

Abstract: Multihop packet radio networks present many challenging problems to the network analyst and designer. The communication channel, which must be shared by all of the network users, is the critical system resource. In order to make efficient use of this shared resource, a variety of channel access protocols to promote organized sharing have been investigated. Sharing can occur in three domains: frequency, time, and space. This paper is mostly concerned with sharing and channel reuse in the spatial domain. A survey of results on approaches to topological design and associated channel access protocols that attempt to optimize system performance by spatial reuse of the communication channel is presented.

User and application program transparent resource sharing multiple computer interface architecture with kernel process level transfer of user requested services

Abstract: A computer network (FIG. 1) comprises a plurality of personal computers (PCs 10), groups of which are each logically connected to a different one of a plurality of intermediate computers (11). At least one of the intermediate computers is connected to a mainframe computer (12). File and resource serving and locking services are provided transparently to PC user programs (200). Certain user service requests ("open file" and "exit" calls) on each PC to the PC operating systems means (20,22) are trapped by an operating system kernel-level patch (21), and corresponding requests are sent to a kernel-level driver (31) on the associated intermediate computer. The driver collects requests from all PCs associated with the intermediate computer and funnels them to a user level request server (32) on the intermediate computer. The request server performs requested file and resource serving and locking services in an effort to make requested files or resources available on or through the intermediate computer to the PC's operating system. The request server calls upon a NETSVR process (33) to find requested files and resources on other intermediate computers and to transfer requested files to its intermediate computer. The request server calls upon an APISVR process (34) to obtain requested files unavilable on intermediate computers (11) from a database (13) of the mainframe computer. The request server returns notices of its successor failure to the patch through the driver. In response to the notices, the patch forwards the trapped user requests to the PC operating system to service the requests. The PC operating system views and uses the associated intermediate computer as a peripheral device to satsify user file or resource requests.

Location Independent Remote Execution in NEST

Abstract: We consider a computing environment consisting of a network of autonomous, yet cooperating personal computer workstations and shared servers. Computing cycles in such an environment can be shared by creating a pool of compute servers in the network that may be used by the workstations to supplement their computing needs. Some processors may be permanently designated to be the compute servers. In addition, through an advertisement mechanism, any workstation may make itself temporarily available for a specific duration of time to be used as a compute server. In this paper, we present the design and implementation of a scheme for augmenting the UNIX® operating system with the location independent remote execution capability. This capability allows processes to be offloaded to the compute servers and preserves the execution environment of these processes as if they were still executing locally at the originating machine. Our model provides execution location independence of processes by preserving the process view of the file system, parent-child relationships, process groups, and process signaling across machine boundaries in a transparent way. We also present our scheme that allows processors to advertise themselves as available to some or all nodes in the network and withdraw as a compute server in a distributed manner. The scheme is robust in presence of node failures.

System for accessing shared resource device by intelligent user devices

Abstract: A shared resource system (20) is disclosed wherein multiple user devices (24) share a resource device such as a disk drive (36). The multiple user devices (24) are interconnected to the resource device by high speed synchronous serial data links (26). Each of the user devices (24) include a serial to parallel/parallel to serial converter means (22) for converting and transmitting on the high speed synchronous serial data links (26) user device requests to access the resource device. The resource device includes a serial to parallel/parallel to serial converter means (30) for converting and transmitting such user device requests on a parallel data bus to the resource device. The resource device converter means (30) including multiple access ports (54) to enable multiple user devices (24) to access the resource device, the converter means (30) individually and periodically polling each of the access ports (54).

A Resource Sharing System for Personal Computers in a LAN: Concepts, Design, and Experience

Abstract: RM is an experimental prototype that supports the use of distributed services by personal computers in a LAN. Using a service request model, RM allows any PC on the LAN to offer and use services, which can be user-written or off-the-shelf applications. A user can start several activities that proceed concurrently and that use services offered by different machines. Program interfaces are provided for the development of distributed applications. Remote execution is supported within the service-request framework. The paper considers issues in resource sharing and discusses the choices that were made for RM. It provides an overview of RM concepts, design, and implementation, and reviews experience using the system.

Multiple CPU program management

Abstract: A procedure which allows users of a computer system comprising a plurality of computers connected in a local area network to share both file resources and application programs on the local area network without modification to existing programs which were designed to run in a non-network environment is disclosed. The local area network comprises a server computer and at least one remote computer. Starting the network comprises an initial program load of the operating system for each of the computers, loading the local area network control program, and then loading a hypervisor or "node enabler" program. At each of the remote computers, a request to load a program or access a data file is converted by the "node enabler" to a file sharing and record locking protocol message with is transmitted to the server computer. The server computer stores a program matrix with entries indicating which programs can be run on the network without conflicts with other systems including the server computer. The server computer also maintains a list of currently running programs and accessed data files. By comparing the remote computer request with the program matrix and the list of currently running programs and accessed data files, a decision to grant a remote computer's request is made. In addition, by recording a unique identification number for each remote computer signed on to the network at the server computer, control of access to licensed programs is maintained.

Support for heterogeneity in the global distributed operating system

Abstract: Heterogeneity in distributed systems is potentially the major restricting factor to effective resource utilisation. In the global distributed operating system, where resource sharing crosses many organisational boundaries on a world-wide scale, this problem is increased. The approach to solving the heterogeneity problem is to provide a simple, coherent and consistent base on which to build services. The global distributed operating system provides support for remote heterogeneous service access. Supporting existing services is an important aspect that is aimed at minimising the changeover effort and cost from the old operating system to the new global distributed operating system.

An algorithm for technology choice in local area network design

Abstract: Technological advances in both the manufacturing and office sectors have emphasized the need to link processors and communications equipment into Local Area Networks LANs to facilitate communication and promote resource sharing. Interviews with designers and users of LANs revealed that a primary problem in the acquisition of a LAN is making technology choices in a cost effective manner when the available technologies and their costs are constantly changing. Since no standards for technology choice currently exist and user demand is expected to increase, system flexibility is also an important concern. The problem of technology choice is formulated as a dynamic integer program. Because of the numerous combinations of technology and network configuration pairings, the Sweeney-Tatham reduction method is utilized to reduce the problem to a computationally tractable size. Finally, the formation is applied to the actual case of an institutional user seeking to network 29 buildings. The resulting reduced problem can be solved on a microcomputer as a shortest path problem.

A distributed channel-sense non-preemptive static priority ring for local area computer networks and its performance

Abstract: In a Local Area Computer Network (LAN), a set of independent distributed users compete for access to a single, shared resource which is the communication channel Thus there arises the need for rules to control access to the communication channel Such rules are generally called protocols or more specifically, Medium Access Control (MAC) procedures This dissertation describes one such MAC procedure called the Distributed Channel-Sense Priority Ring (DCPR) which has been implemented on a ring topology A formal protocol specification language called SAN (State Architecture Notation) is used for such a description A performance model of DCPR is presented Studies of it and suggestions of an improved DCPR protocol called IDCPR is provided Performance comparison of DCPR and IDCPR with well-known medium access control protocols is further provided

Shared resource access guard system among plural host computers

Abstract: PURPOSE:To switch shared resources quickly and to sufficiently guard shared resources against access as well by allowing each host to generate closing information based on a logical host number inputted to the host itself and shared resource information and to check this generated information to decide whether access is permitted or not. CONSTITUTION:A logical host number input means 5 inputs a logical host number. An information input means 7 reads in shared resource definition information stored in a shared resource definition information storage area 13. A closing means 8 generates the closing information of shared resources, which the host itself cannot access, in accordance with the logical host number from the means 5 and shared resource definition information from the means 7 and registers this generated information in a closing information storage area 12. It is checked whether this registration is terminated normally or not, and the processing is terminated if it is terminated normally, but the error processing is performed if it is terminated abnormally.

Criteria for the evaluation of library networks

Abstract: The relatively recent growth of library networks has focused on establishing, organizing, and maintaining systems for facilitating resource sharing. This paper samples some evaluation measures found in the literature regarding evaluating various types of networks: large-scale multi-type library networks (bibliographic utilities), regional networks, single-type and local systems. The paper concludes with a discussion of proposed criteria which may be useful for all types of library networks.

Hardware Support for the Distributed Operating System of the Heidelberg Polyp Processor

Abstract: A multiprocessor consisting of independent processing elements with local memory and local system and application software is a special case of a distributed computer system (DCS). This paper describes such a system, the Heidelberg Polyp polyprocessor [1], its distributed operating system (DOS), and hardware support for distributed resource sharing. Current versions use 30 clusters with one or a few 32 bit microprocessors each [2,3]. Depending on the configuration, clusters may be general purpose or specialized servers. Clusters offering the same server functions can be grouped into pools of identical resources. Clusters using specialized hardware set up static pools. General purpose processor clusters can be specialized by software and can be assigned to pools dynamically. Hardware support is provided for handling pools independent of their sizes. Thus, adding new members to pools for speed up or shut-down of faulty members can be done software transparently. All processing clusters are interconnected by multiple buses for data transfers and interrupts. The system is managed decentrally by a DOS. A copy of this DOS is stored locally in each cluster. DOS requests may be executed in parallel and operate on common, but distributed system tables. The basic function of the DOS is to assign tasks with certain requirements to clusters supplying these functions and to establish communication between them. Some of the DOS functions may be time critical for certain applications. For that, hardware support is offered, e.g. for setting up an optimal dynamic load distribution within a heterogeneous DCS [4]. Pool-size independent system management as well as hardware scheduling is done via two resource sharing interconnection networks (RSIN) [5]. One of them, the Polybus system [6] allows to address pools as a whole and to request random selection of a member by hardware. The other RSIN, the Syncbus, allows to distribute priority queues of waiting tasks and uses a nonempty queue status as a distributed programmed interrupt to a certain pool. Application of boths RSINs is discussed in detail.