Andrew S. Tanenbaum

Distributed operating systems

In the past five years, distributed operating systems research has gone through a consolidation phase. On a large number of design issues there is now considerable consensus between different research groups. In this paper, an overview cf recent research in distributed systems is given. In turn, the paper discusses overall system structure, protection issues, file system designs, problems and solutions for fault tolerance and a mechanism that is rapidly becoming very important for efficient distributed systems design: hints. An attempt was made to provide sufficient references to interesting research projects for the reader to find material for more detailed study.

Programming languages for distributed computing systems

When distributed systems first appeared, they were programmed in traditional sequential languages, usually with the addition of a few library procedures for sending and receiving messages. As distributed applications became more commonplace and more sophisticated, this ad hoc approach became less satisfactory. Researchers all over the world began designing new programming languages specifically for implementing distributed applications. These languages and their history, their underlying principles, their design, and their use are the subject of this paper. We begin by giving our view of what a distributed system is, illustrating with examples to avoid confusion on this important and controversial point. We then describe the three main characteristics that distinguish distributed programming languages from traditional sequential languages, namely, how they deal with parallelism, communication, and partial failures. Finally, we discuss 15 representative distributed languages to give the flavor of each. These examples include languages based on message passing, rendezvous, remote procedure call, objects, and atomic transactions, as well as functional languages, logic languages, and distributed data structure languages. The paper concludes with a comprehensive bibliography listing over 200 papers on nearly 100 distributed programming languages.

Orca: a language for parallel programming of distributed systems

A detailed description is given of the Orca language design and the design choices are discussed. Orca is intended for applications programmers rather than systems programmers. This is reflected in its design goals to provide a simple, easy-to-use language that is type-secure and provides clean semantics. Three example parallel applications in Orca, one of which is described in detail, are discussed. One of the existing implementations, which is based on reliable broadcasting, is described. Performance measurements of this system are given for three parallel applications. The measurements show that significant speedups can be obtained for all three applications. The authors compare Orca with several related languages and systems. >

Group communication in the Amoeba distributed operating system

Primitives for broadcast communication that have been integrated with the Amoeba distributed operating system are introduced. The semantics of the broadcast primitives are simple and easy to understand, but are still powerful. The proposed primitives, for example, guarantee global ordering of broadcast messages. The proposed primitives are also efficient: a reliable broadcast can be done in just slightly more than two messages, so the performance is comparable to a remote procedure call. In addition, the primitives are flexible; user applications can, for example, trade performance against fault-tolerance.<<ETX>>

Globe: a wide area distributed system

The authors present an object-based framework for developing wide-area distributed applications. The World Wide Webs current performance problems illustrate the benefit of encapsulating state, operations, and implementation strategies on a per-object basis. The authors describe how distributed objects can implement worldwide scalable Web documents.

An efficient reliable broadcast protocol

Many distributed and parallel applications can make good use of broadcast communication. In this paper we present a (software) protocol that simulates reliable broadcast, even on an unreliable network. Using this protocol, application programs need not worry about lost messages. Recovery of communication failures is handled automatically and transparently by the protocol. In normal operation, our protocol is more efficient than previously published reliable broadcast protocols. An initial implementation of the protocol on 10 MC68020 CPUs connected by a 10 Mbit/sec Ethernet performs a reliable broadcast in 1.5 msec.

Is your cat infected with a computer virus

RFID systems as a whole are often treated with suspicion, but the input data received from individual RFID tags is implicitly trusted. RFID attacks are currently conceived as properly formatted but fake RFID data; however no one expects an RFID tag to send a SQL injection attack or a buffer overflow. This paper is meant to serve as a warning that data from RFID tags can be used to exploit back-end software systems. RFID middleware writers must therefore build appropriate checks (bounds checking, special character filtering, etc.), to prevent RFID middleware from suffering all of the well-known vulnerabilities experienced by the Internet. Furthermore, as a proof of concept, this paper presents the first self-replicating RFID virus. This virus uses RFID tags as a vector to compromise backend RFID middleware systems, via a SQL injection attack

RFID guardian: a battery-powered mobile device for RFID privacy management

RFID tags are tiny, inexpensive, inductively powered computers that are going to replace bar codes on many products, but which have many other uses as well. For example, they will allow smart washing machines to check for incompatible clothes (e.g., white shirts and red socks) and smart refrigerators to check for milk that is too old to be consumed. Subdermal tags with medical information are already being implanted in animals and people. However, a world in which practically everything is tagged and can be read at a modest distance by anyone who wants to buy an RFID reader introduces serious security and privacy issues. For example, women walking down the street may be effectively broadcasting the sizes of their RFID-tagged bras and medical data without realizing it. To protect people in this environment, we propose developing a compact, portable, electronic device called an RFID Guardian, which people can carry with them. In the future, it could be integrated into PDAs or cell phones. The RFID Guardian looks for, records, and displays all RFID tags and scans in the vicinity, manages RFID keys, authenticates nearby RFID readers, and blocks attempted accesses to the user’s RFID tags from unauthorized readers. In this way, people can find out what RFID activity is occuring around them and take corrective action if need be.

The evolution of RFID security

As RFID technology progresses, security and privacy threats also evolve. By examining RFIDs history, we can learn from past mistakes, rediscover successful solutions, and inspire future research.

The Design of a Capability-Based Distributed Operating System

Fifth-generation computer systems will use large numbers of processors to achieve high performance. In this paper a capability-based operating system designed for this environment is discussed. Capability-based operating systems have traditionally required large, complex kernels to manage the use of capabilities. In our proposal, capability management is done entirely by user programs without giving up any of the protection aspects normally associated with capabilities. The basic idea is to use one-way functions and encryption to protect sensitive information. Various aspects of the proposed system are discussed.