Findings of a comparison of five filing protocols

Filing protocols are essential for the management and dissemination of shared information within computer systems. This is a survey of the current state of the art in filing protocols. Five popular filing protocols were selected and subjected to a rigorous comparison. FTAM, FTP, UNIX rep, XNS Filing, and NFS are compared in the following areas: exported interface, concurrency control, access control, error recovery, and performance. The coverage of background material includes a taxonomy and a brief history of filing protocols

User Interface Implementation for Network License Management System

This paper describes a project to understand and enhance a distributed application - the Applied Science Microlab Network License Management System(NLMS1, and to design and implement an improved user interface for that system. The NLMS utilizes a client-server architecture, the TCPIIP network protocol suite, and the Remote Procedure Call (RPC) facility for the program to interface to the network. The new user interface is based on X WindowslMot~foUr NIX client and Microsoft Windows for PC client. In addition, management reports are added to the system and expected to provide the package usage statistics to aid in future software purchase plans. The goals of my project are to do some developmental work in the UNZX environment; to understand more about network programming; to learn how to write distributed applications; and to learn to programming X Windows/Motif and Microsoft Windows. In my opinion, I have accornplished these goals

Performance analysis of network based file systems

The performance of multi-user workstations that access files over a local area network is studied. Such file systems, called distributed file systems, provide access of remote file systems with a great degree of transparency. The main objectives are To study the principles of distributed file systems. specifically NFS from Sun Microsystems and RFS from AT&T. To investigate a methodology to evaluate the performance of such file systems. To evaluate the performance of these network based file systems and study the effect of various implementation issues on their performance. The major conclusions drawn are Allowing larger block transfers from a remote resource to clients over the network improves performance. The benefits, however, are limited to disk block sizes of 12-16 Kbytes data. Performance can also be improved by proper layout structure on the disk. Enhancements of the server prove to be more cost effective than those of the client. Network contention is not the major bottleneck when a high speed network is being used. A configuration of computers sharing file systems over a LAN can have satisfactory performance in a software development environment

Lightweight Communications and Marshalling for Low-Latency Interprocess Communication

We describe the Lightweight Communications and Marshalling (LCM) library for message passing and data marshalling. The primary goal of LCM is to simplify the development of low-latency message passing systems, targeted at real-time robotics applications. LCM is comprised of several components: a data type specification language, a message passing system, logging/playback tools, and real-time analysis tools. LCM provides a platform- and language-independent type specification language. These specifications can be compiled into platform and language specific implementations, eliminating the need for users to implement marshalling code while guaranteeing run-time type safety. Messages can be transmitted between different processes using LCM's message-passing system, which implements a publish/subscribe model. LCM's implementation is notable in providing low-latency messaging and eliminating the need for a central communications "hub". This architecture makes it easy to mix simulated, recorded, and live data sources. A number of logging, playback, and traffic inspection tools simplify common development and debugging tasks. LCM is targeted at robotics and other real-time systems where low latency is critical; its messaging model permits dropping messages in order to minimize the latency of new messages. In this paper, we explain LCM's design, evaluate its performance, and describe its application to a number of autonomous land, underwater, and aerial robots

Design and Implementation of ORFA

ORFA is a user-level protocol that aims at providing an efficient remote file system access. It uses high bandwidth local networks and their specific API to directly connect user programs to data in the remote server. The ORFA model and its first implementation are described in this paper. The client is an automatically preloaded shared library that transparently overrides glibc I/O calls and redirect them to the server if concerned files are remote. The server may be a user program implementing a custom memory file system, or accessing native file systems