EROS is a capability-based operating system for commodity processors which uses a single level storage model. The single level store's persistence is transparent to applications. The performance consequences of support for transparent persistence and capability-based architectures are generally believed to be negative. Surprisingly, the basic operations of EROS (such as IPC) are generally comparable in cost to similar operations in conventional systems. This is demonstrated with a set of microbenchmark measurements of semantically similar operations in Linux.The EROS system achieves its performance by coupling well-chosen abstract objects with caching techniques for those objects. The objects (processes, nodes, and pages) are well-supported by conventional hardware, reducing the overhead of capabilities. Software-managed caching techniques for these objects reduce the cost of persistence. The resulting performance suggests that composing protected subsystems may be less costly than commonly believed.

In a computer system, the integrity of lower layers is typically treated as axiomatic by higher layers. Under the presumption that the hardware comprising the machine (the lowest layer) is valid, the integrity of a layer can be guaranteed if and only if: (1) the integrity of the lower layers is checked and (2) transitions to higher layers occur only after integrity checks on them are complete. The resulting integrity "chain" inductively guarantees system integrity. When these conditions are not met, as they typically are not in the bootstrapping (initialization) of a computer system, no integrity guarantees can be made, yet these guarantees are increasingly important to diverse applications such as Internet commerce, security systems and "active networks". In this paper, we describe the AEGIS architecture for initializing a computer system. It validates integrity at each layer transition in the bootstrap process. AEGIS also includes a recovery process for integrity check failures, and we show how this results in robust systems.

Communication latency can be reduced by increasing bandwidth via a sender-based anticipation technique called Parallel Communication. The authors apply this method to anonymous FTP. Their analysis of log files indicates that latency can be reduced to 2 round-trip times, as small as 0.6 round-trip time/file, for a 7x increase in bandwidth. This technique applies to up to 95% of the FTP traffic. This method is expected to be especially useful in reducing latency in automated FTP access. Such as in the World-WideWorld-Wide Web.>

AURORA is one of five US testbeds charged with exploring applications of, and technologies necessary for, networks operating at gigabit per second or higher bandwidths. The authors provide an overview of the goals and methodologies employed in AURORA and report preliminary results from the first year of research. AURORA is an experiment in collaboration, where government support has spurred interaction among centers of excellence in industry, academia, and government. The emphasis of the AURORA testbed is research into the supporting technologies for gigabit networking. The targets include new software architectures, network abstractions, hardware technologies, and applications. The AURORA testbed will provide a platform in which researchers can explore business and scientific applications of gigabit networks, while evolving the network architecture to meet the needs of these emerging applications.>

We believe that many distributed computing systems of the future will use distributed shared memory as a technique for interprocess communication. Thus, traffic generated by memory requests will be a major component of the traffic for any networks which connect nodes in such a system. In this paper, we study memory reference strings gathered with a tracing program we devised. We study several models. First, we look at raw reference data, as would be seen if the network were a backplane. Second, we examine references in units of “blocks”, first using a one-block cache model and then with an infinite cache. Finally, we study the effect of predictive prepaging of these “blocks” on the traffic. We provide a novel representation of memory reference data which can used to calculate interarrival distributions directly. Integrating communication with computation can be used to control both traffic and performance.

Changes made to a distributed shared memory that runs of Sun workstations under SunOS 4.0 operating systems, called Mether, are outlined. Protocols developed to use Mether and that minimize host load, network load, and latency are discussed. The changes to Mether involve exposing an inconsistent store to the applications and making access to the consistent and inconsistent versions very convenient, providing both demand-driven and data-driven semantics for updating pages, and allowing the user to specify that only a small subset of a page needs to be transferred.>

Memnet is a shared-memory local area network under development at the University of Delaware that provides close coupling to the processors of a physically distributed multiprocessor system. The Memnet local network appears as memory in the physical address space of each processor (host) on the network.

Noahnet is an experimental flood local area network with features such as high reliability and high performance. Noahnet uses a randomly connected graph topology with four to five interconnections per node and a flooding protocol to route messages.

The advent of packet-switched networks has led to increased use of computers for sending text messages (memos) between people. However, attachment to common carrier or equivalent packet networks is expensive and/or restricted by organizational policies. In addition, use of several networks creates the need for relaying memos between them. The work described here is designed to free users from dependence upon any particular communication environment and to provide a memo distribution facility which can employ whatever communication channels are available. It will support variable-network structures, emulation of network attachment, and inter-network memo forwarding.

A study is presented which permits the formal analysis and synthesis of recoverable computer communication protocols. This study is based on a formal representation of processes by a model of computation, the Petri nets (PN's). The PN model is generalized to include a representation of the possible failures, and then, the concept of "recoverability" is formally defined. A set of necessary and sufficient conditions which a process must satisfy in order to be recoverable is derived. In the PN model, the processes that satisfy these conditions are shown to have some practical limitations. A new model, the time-Petri net (TPN), is introduced to remove these limitations. This new model allows the introduction of constraints in the execution times of its part. As shown in this paper, the TPN appears to be a suitable model for the study of practical recoverable processes. Several practical communication protocols are formally designed and analyzed using this new model, and some interesting properties of these protocols are formally derived.

In Hough [1], Duda and Hart [2], and Griffith [3] procedures were proposed for detecting lines in pictures and in [2] Duda and Hart extended their method for more general algebraic curve, fitting. This correspondence shows how this method can be used to detect any given curve in a specific orientation. The procedure presented here con be easily implemented and can be efficiently implemented in a parallel machine.

SNOBOL is a programming language for the manipulation of strings of symbols. A statement in the SNOBOL language consists of a rule that operates on symbolically named strings. The basic operations are string formation, pattern matching and replacement. Facilities for integer arithmetic, indirect referencing, and input-output are included. In the design of the language, emphasis has been placed on a format that is simple and intuitive. SNOBOL has been implemented for the IBM 7090.