Samuel T. Chanson

Process groups and group communications: classifications and requirements

Different distributed applications are examined and their requirements for group communication support are outlined. The concept of a process group is defined. On the basis of internal structures and external behavior, groups are classified into different categories and their properties are discussed. Group communication is an OS-level abstraction that offers convenience and clarity to the programmer.<<ETX>>

Distributed, object-based programming systems

The development of distributed operating systems and object-based programming languages makes possible an environment in which programs consisting of a set of interacting modules, or objects, may execute concurrently on a collection of loosely coupled processors. An object-based programming language encourages a methodology for designing and creating a program as a set of autonomous components, whereas a distributed operating system permits a collection of workstations or personal computers to be treated as a single entity. The amalgamation of these two concepts has resulted in systems that shall be referred to as distributed, object-based programming systems. This paper discusses issues in the design and implementation of such systems. Following the presentation of fundamental concepts and various object models, issues in object management, object interaction management, and physical resource management are discussed. Extensive examples are drawn from existing systems.

A unified approach to protocol test sequence generation

The authors present an approach that combines control flow and data flow analysis techniques to generate unified test sequences (UTSs) for testing protocols modeled as an extended finite-state machine (EFSM). The UTS has the same fault detection capability as the characterizing sequence (UIO, DS, or W) methods for the control part, and at the same time covers all paths that connect variable definitions and uses (all du-paths) for data flow testing. A transition dependence graph is proposed to represent the dependence relations between transitions needed to construct the test sequences. The executable UTS is then selected using constraint satisfaction problem (CSP) solution techniques and transition loop analysis.<<ETX>>

Reliable group communication in distributed systems

The design and implementation of a reliable group communication mechanism is presented. The mechanism guarantees a form of atomicity in that the messages are received by all operational members of the group or by none of them. Since the overhead in enforcing the order of messages is nontrivial, the mechanism provides two types of message transmission: one guarantees delivery of the messages in the same order to all members of a group, and the other guarantees only atomicity with messages delivered in some arbitrary order. The message-ordering property can be used to simplify distributed database and distributed processing algorithms. The mechanism can survive despite process, host, and communication failures.<<ETX>>

On tools supporting the use of formal description techniques in protocol development

Abstract FDT tools support protocol development by making certain activities feasible, easier to be performed, more reliable, and faster. This paper discusses the desirable properties of FDT tools and classifies them according to the different stages of the protocol development cycle. An assessment of the tools available so far and projections (or suggestions) of the tools to come are given. A list of the tools that have appeared since the mid 1980s is also included.

On ferry clip approaches in protocol testing

Abstract The context of this paper is protocol testing, i.e. testing communications protocol implementations against the relevant protocol standards or recommendations. This paper presents a framework for the realization of the ferry clip — a generalized application of the ferry principle in protocol testing. The framework has been developed through experience gained in the design and implementation of prototype ferry clip test systems. Different ferry clip test approaches are explored and analyzed. A refined ferry control protocol is proposed and pertinent issues in defining such protocols are discussed.

Cartesian authentication codes from functions with optimal nonlinearity

In this paper, we present several classes of authentication codes using functions with perfect nonlinearity and optimum nonlinearity. Some of the authentication codes are optimal. On the other hand, these authentication codes are easy to implement due to their simple algebraic structures.

Automatic protocol test suite derivation

In this paper, an automatic protocol test case generator that generates both test sequence and test data is presented. The underlying model is an extended finite state machine (EFSM) and Estelle is used as the formal description language. First, test sequences are generated using a combined control and data flow testing method. A set of path conditions associated with each test sequence is obtained using symbolic execution techniques. By solving the path conditions as a group of constraints, test data are then automatically generated. A prototype system implementing the above procedures has been built. The system has been used to generate test cases for real protocols such as TP0, FDDI and LAPB, and has been integrated in the UBC protocol testing environment.<<ETX>>

Failure transparency in remote procedure calls

A model of remote procedure call (RPC) which reflects certain generic properties of the application layer that can be exploited by the RPC layer during failure recovery is presented. A technique of adopting orphans caused by failures, which is based on the model, is described. The technique minimizes the rollback which may be required in orphan-killing techniques. Algorithmic details of the adoption technique are described, and a quantitative analysis is presented. The model is implemented as a prototype on a local area network. The simplicity and generality of the failure recovery renders the RPC model useful in distributed systems, particularly those that are large and heterogeneous and hence have complex failure modes. >

Fragmentation in store-and-forward message transfer

The advantages of store-and-forward (S/F) message transfer at the application layer and problems with existing systems are discussed. Current systems suffer from the limitation that if an intermediate message transfer agent (MTA), the entity responsible for storing and forwarding messages, cannot store a message in its entirety due to insufficient buffer space, then the transfer fails. A mechanism is introduced, called message fragmentation, to transfer messages too large to be completely stored on an intermediate MTA automatically and efficiently. In addition to letting a large message pass through the network, fragmentation improves performance in an S/F message-based system. Schemes developed for flow control, deadlock prevention, and buffer management in packet-switched networks are described, and their suitability for use in the message-handling environment is discussed. Several novel schemes for buffer management in the message-handling environment are presented. The EAN X.400-based S/F message-handling system developed at the University of British Columbia is briefly cited as an example.<<ETX>>