Autonet is a self-configuring local area network composed of switches interconnected by 100 Mbit/second, full-duplex, point-to-point links. The switches contain 12 ports that are internally connected by a full crossbar. Switches use cut-through to achieve a packet forwarding latency as low as 2 microseconds per switch. Any switch port can be cabled to any other switch port or to a host network controller.A processor in each switch monitors the network's physical configuration. A distributed algorithm running on the switch processors computes the routes packets are to follow and fills in the packet forwarding table in each switch. This algorithm automatically recalculates the forwarding tables to incorporate repaired or new links and switches, and to bypass links and switches that have failed or been removed. Host network controllers have alternate ports to the network and fail over if the active port stops working.With Autonet, distinct paths through the set of network links can carry packets in parallel. Thus, in a suitable physical configuration, many pairs of hosts can communicate simultaneously at full link bandwidth. The aggregate bandwidth of an Autonet can be increased by adding more links and switches. Each switch can handle up to 2 million packets/second. Coaxial links can span 100 meters and fiber links can span two kilometers.A 30-switch network with more than 100 hosts is the service network for

Remote procedure calls (RPC) appear to be a useful paradig m for providing communication across a network between programs written in a high-level language. This paper describes a package providing a remote procedure call facility, the options that face the designer of such a package, and the decisions ~we made. We describe the overall structure of our RPC mechanism, our facilities for binding RPC clients, the transport level communication protocol, and some performance measurements. We include descriptioro~ of some optimizations used to achieve high performance and to minimize the load on server machines that have many clients.

Remote procedure calls (RPC) appear to be a useful paradig m for providing communication across a network between programs written in a high-level language. This paper describes a package providing a remote procedure call facility, the options that face the designer of such a package, and the decisions ~we made. We describe the overall structure of our RPC mechanism, our facilities for binding RPC clients, the transport level communication protocol, and some performance measurements. We include descriptioro~ of some optimizations used to achieve high performance and to minimize the load on server machines that have many clients.

Grapevine is a multicomputer system on the Xerox research internet. It provides facilities for the delivery of digital messages such as computer mail; for naming people, machines, and services; for authenticating people and machines; and for locating services on the internet. This paper has two goals: to describe the system itself and to serve as a case study of a real application of distributed computing. Part I describes the set of services provided by Grapevine and how its data and function are divided among computers on the internet. Part II presents in more detail selected aspects of Grapevine that illustrate novel facilities or implementation techniques, or that provide insight into the structure of a distributed system. Part III summarizes the current state of the system and the lesson learned from it so far.

Most commodity flash disks exhibit very poor performance when presented with writes that are not sequentially ordered. We argue that performance can be significantly improved through the addition of sufficient RAM to hold data structures describing a fine-grain mapping between disk logical blocks and physical flash addresses. We present a design that accomplishes this.

Software Transactional Memory (STM) is an attractive basis for the development of language features for concurrent programming. However, the semantics of these features can be delicate and problematic. In this paper we explore the tradeoffs between semantic simplicity, the viability of efficient implementation strategies, and the flexibility of language constructs. Specifically, we develop semantics and type systems for the constructs of the Automatic Mutual Exclusion (AME) programming model; our results apply also to other constructs, such as atomic blocks. With this semantics as a point of reference, we study several implementation strategies. We model STM systems that use in-place update, optimistic concurrency, lazy conflict detection, and roll-back. These strategies are correct only under non-trivial assumptions that we identify and analyze. One important source of errors is that some efficient implementations create dangerous "zombie" computations where a transaction keeps running after experiencing a conflict; the assumptions confine the effects of these computations.

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A network object is an object whose methods can be invoked over a network. This paper describes the design, implementation, and early experience with a network objects system for Modula-3. The system is novel for its overall simplicity. The paper includes a thorough description of realistic marshaling algorithms for network objects.