bluuebunny/crossref_metadata_2025 huggingface dataset:
Precision synchronization of computer network clocks
Authors: Mills David L.
Published: October 2004

This paper builds on previous work involving the Network Time Protocol, which is used to synchronize computer clocks in the Internet. It describes a series of incremental improvements in system hardware and software which result in significantly better accuracy and stability, especially in primary time servers directly synchronized to radio or satellite time services. These improvements include novel interfacing techniques and operating system features. The goal in this effort is to improve the synchronization accuracy for fast computers and networks from the tens of milliseconds regime of the present technology to the submillisecond regime of the future.In order to assess how well these improvements work, a series of experiments is described in which the error contributions of various modern Unix system hardware and software components are calibrated. These experiments define the accuracy and stability expectations of the computer clock and establish its design parameters with respect to time and frequency error tolerances. The paper concludes that submillisecond accuracies are indeed practical, but that further improvements will be possible only through the use of temperature-compensated local clock oscillators.
Normative standards for IS research
Authors: Straub Detmar W. , Ang Soon , Evaristo Roberto
Published: October 2004

Manuscript rejection rates for the top IS academic journals average 85-90%. An undesirable consequence of this level of rejection is that the IS community becomes discouraged and disaffected with the review process. Part of the reason so many manuscripts are not ready for publication may lie in the lack of agreement and understanding among IS researchers on the key criteria for evaluating IS research. The purpose of this study is to report on a survey of the perceptions of published authors, reviewers, and editorial board members about the manuscript requirements for publication in IS. Knowledge gained from the study has the potential to: (1) improve the overall quality of future submissions by focusing the researchers' time and effort on key criteria and normative standards for publishing research, as differentiated by research method, (2) reduce the number of revisions required before a manuscript gets published, and (3) suggest journal evaluation forms that more accurately reflect the standards of the IS community. The empirical results reported here provide an introspective analysis of the IS field, a set of normative standards for IS, and an action plan for IS journals.
Temporal databases
Authors: Lai Vincent S. , Kuilboer Jean-Pierre , Guynes Jan L.
Published: October 2004

This article presents a Temporal Enhanced Entity-Relationship (TEER) model, which shows how temporal information can be captured within a conceptual data model and extended to the relational data model. The time elements proposed for the TEER model include both transaction time and valid time. In order to support time-related queries, the query language SQL has been extended for definition, retrieval, and control of historical relations. For the commercialization of temporal databases, several technical and non-technical issues need to be resolved. This article provides a discussion of these issues and evaluates its progress toward commercialization.
Making greed work in networks
Authors: Shenker Scott
Published: October 2004

This paper discusses congestion control from a game-theoretic perspective. There are two basic premises: (1) users are assumed to be independent and selfish, and (2) central administrative control is exercised only at the network switches. The operating points resulting from selfish user behavior depend crucially on the service disciplines implemented in network switches. This effect is investigated in a simple model consisting of a single exponential server shared by many Poisson sources. We discuss the extent to which one can guarantee, through the choice of switch service disciplines, that these selfish operating points will be efficient and fair. We also discuss to what extent the choice of switch service disciplines can ensure that these selfish operating points are unique and are easily and rapidly accessible by simple self-optimization techniques. We show that no service discipline can guarantee optimal efficiency. As for the other properties, we show that the traditional FIFO service discipline guarantees none of these properties, but that a service discipline called
Fair Share
guarantees all of them. While the treatment utilizes game-theoretic concepts, no previous knowledge of game theory is assumed.
Reliable and efficient hop-by-hop flow control
Authors: Özveren Cüneyt , Simcoe Robert , Varghese George
Published: October 2004

Hop-by-hop flow control can be used to fairly share the bandwidth of a network among competing flows. No data is lost even in overload conditions; yet each flow gets access to the maximum throughput when the network is lightly loaded. However, some schemes for hop-by-hop flow control require too much memory; some of them are not resilient to errors. We propose a scheme for making hop-by-hop flow control resilient and show that it has advantages over schemes proposed by Kung. We also describe a novel method for
sharing
the available buffers among the flows on a link; our scheme allows us to potentially reduce the memory requirement (or increase the number of flows that can be supported) by an order of magnitude. Most of the work is described in the context of an ATM network that uses credit based flow control. However our ideas extend to networks in which flows can be distinguished, and to rate based flow control schemes.
Signaling and operating system support for native-mode ATM applications
Authors: Sharma R. , Keshav S.
Published: October 2004

Applications communicating over connectionless networks, such as IP, cannot obtain per-connection Quality of Service (QoS) guarantees. In contrast, the connection-oriented nature of the ATM layer and its per-virtual-circuit QoS guarantees are visible to a
native-mode ATM
application. We describe the design and implementation of operating system and signaling support for native-mode applications, independent of the semantics of the protocol layers or of the signaling protocol. The work was done in the context of a Unix-like operating system and the Xunet 2 wide-area high-speed ATM network. The IPC-based interface between an application and the signaling entity allows processes to request parameterized virtual circuits, and the signaling-kernel interface allows resources to be reclaimed from prematurely terminating processes. We also built a simple encapsulation layer over raw IP that allows any host with IP access to send AAL frames into the wide-area network with little performance degradation. Our design makes it simple to port existing TCP/IP socket applications to a native-mode ATM protocol stack and also enables interoperation of existing IP networks with our ATM network. Our experience has been positive - the design is robust, easily extendible and scales well with the number of open connections.
On optimization of polling policy represented by neural network
Authors: Matsumoto Yutaka
Published: October 2004

This paper deals with the problem of scheduling a server in a polling system with multiple queues and complete information. We represent the polling policy by a neural network; namely, given the number of waiting customers in each queue, the server determines next queue he should visit according to the output of the neural network. By using the simulated annealing method, we improve the
neural
polling policy in such a way that the mean delay of customers is minimized. Numerical results show that the present approach is especially valid for asymmetric polling systems whose analytical optimization is considered intractable.
Design and implementation of a prototype optical deflection network
Authors: Feehrer John , Sauer Jon , Ramfelt Lars
Published: October 2004

We describe the design and implementation of a packet-switched fiber optic interconnect prototype with a ShuffleNet topology, intended for use in shared-memory multiprocessors. Coupled with existing latency-hiding mechanisms, it can reduce latency to remote memory locations. Nodes use deflection routing to resolve contention. Each node contains a processor, memory, photonic switch, and packet routing processor. Payload remains in optical form from source to final destination. Each host processor is a commercial workstation with FIFO interfaces between its bus and the photonic switch. A global clock is distributed optically to each node to minimize skew. Component costs and network performance figures are presented for various node configurations including bit-per-wavelength and fiber-parallel packet formats. Our efforts to implement and test a practical interconnect including real host computers distinguishes our work from previous theoretical and experimental work. We summarize obstacles we encountered and discuss future work.
Conflict-free channel assignment for an optical cluster-based shuffle network configuration
Authors: Aly Khaled A.
Published: October 2004

A passive optical realization of large expandable shuffle networks is considered, where the general (
p, k
) shuffle function interconnects star-coupled clusters of time and/or wavelength multiplexed nodes. This configuration enables network partitioning into independent subnetworks that can emulate various indirect cube topologies on a virtual point-to-point basis. Node transmitters are assigned fixed channels and reconfiguring the partition and/or the individual sub-network topologies is achieved by monitoring the appropriate channels. The considered network configuration can function as a general-purpose optical interconnect for a variety of heterogeneous traffic sources, such as multicomputers and ATM network interface units, communicating independently within logically defined subnetworks. The paper derives a conflict-free channel partition and assignment map for a general (
p, k
) cluster shuffle using a minimal number of channel sets.
MACAW
Authors: Bharghavan Vaduvur , Demers Alan , Shenker Scott , Zhang Lixia
Published: October 2004

In recent years, a wide variety of mobile computing devices has emerged, including portables, palmtops, and personal digital assistants. Providing adequate network connectivity for these devices will require a new generation of wireless LAN technology. In this paper we study media access protocols for a single channel wireless LAN being developed at Xerox Corporation's Palo Alto Research Center. We start with the MACA media access protocol first proposed by Karn [9] and later refined by Biba [3] which uses an RTS-CTS-DATA packet exchange and binary exponential back-off. Using packet-level simulations, we examine various performance and design issues in such protocols. Our analysis leads to a new protocol, MACAW, which uses an RTS-CTS-DS-DATA-ACK message exchange and includes a significantly different backoff algorithm.
Highly dynamic Destination-Sequenced Distance-Vector routing (DSDV) for mobile computers
Authors: Perkins Charles E. , Bhagwat Pravin
Published: October 2004

An
ad-hoc
network is the cooperative engagement of a collection of Mobile Hosts without the required intervention of any centralized Access Point. In this paper we present an innovative design for the operation of such ad-hoc networks. The basic idea of the design is to operate each Mobile Host as a specialized router, which periodically advertises its view of the interconnection topology with other Mobile Hosts within the network. This amounts to a new sort of routing protocol. We have investigated modifications to the basic Bellman-Ford routing mechanisms, as specified by RIP [5], to make it suitable for a dynamic and self-starting network mechanism as is required by users wishing to utilize ad hoc networks. Our modifications address some of the previous objections to the use of Bellman-Ford, related to the poor looping properties of such algorithms in the face of broken links and the resulting time dependent nature of the interconnection topology describing the links between the Mobile Hosts. Finally, we describe the ways in which the basic network-layer routing can be modified to provide MAC-layer support for ad-hoc networks.
A methodology for designing communication protocols
Authors: Singh Gurdip
Published: October 2004

We propose a compositional technique for designing protocols. The technique involves specifying constraints between the events of the component protocols. A constraint may either require synchronization between certain events of the component protocols or may require inhibiting an event in one protocol on the occurrence of an event in another component protocol. We find both types of constraints useful in composing protocols. We demonstrate the applicability of the technique by deriving several protocols. The technique facilitates modular design and verification. Our technique, in conjunction with the sequential composition technique, can be used to design complex protocols.
Analysis, modeling and generation of self-similar VBR video traffic
Authors: Garrett Mark W. , Willinger Walter
Published: October 2004

We present a detailed statistical analysis of a 2-hour long empirical sample of VBR video. The sample was obtained by applying a simple intraframe video compression code to an action movie. The main findings of our analysis are (1) the tail behavior of the marginal bandwidth distribution can be accurately described using “heavy-tailed” distributions (e.g., Pareto); (2) the autocorrelation of the VBR video sequence decays hyperbolically (equivalent to
long-range dependence
) and can be modeled using self-similar processes. We combine our findings in a new (non-Markovian) source model for VBR video and present an algorithm for generating synthetic traffic. Trace-driven simulations show that statistical multiplexing results in significant bandwidth efficiency even when long-range dependence is present. Simulations of our source model show long-range dependence and heavy-tailed marginals to be important components which are not accounted for in currently used VBR video traffic models.
An algorithm for lossless smoothing of MPEG video
Authors: Lam Simon S. , Chow Simon , Yau David K. Y.
Published: October 2004

Interframe compression techniques, such as those used in MPEG video, give rise to a coded bit stream where picture sizes differ by a factor of 10 or more. As a result, buffering is needed to reduce (smooth) rate fluctuations of encoder output from one picture to the next; without smoothing, the performance of networks that carry such video traffic would be adversely affected. Various techniques have been suggested for controlling the output rate of a VBR encoder to alleviate network congestion or prevent buffer overflow. Most of these techniques, however, are
lossy
, and should be used only as a last resort. In this paper, we design and specify an algorithm for
lossless
smoothing. The algorithm is characterized by three parameters:
D
(delay bound),
K
(number of pictures with known sizes), and
H
(lookahead interval). We present a theorem which guarantees that, if
K
≥ 1, the algorithm finds a solution that satisfies the delay bound. (Although the algorithm and theorem were motivated by MPEG video, they are applicable to the smoothing of compressed video in general). To study performance characteristics of the algorithm, we conducted a large number of experiments using statistics from four MPEG video sequences.
USC
Authors: O'Malley Sean , Proebsting Todd , Montz Allen Brady
Published: October 2004

USC is a new stub compiler that generates stubs that perform many data conversion operations. USC is flexible and can be used in situations where previously only manual code generation was possible. USC generated code is up to 20 times faster than code generated by traditional argument marshaling schemes such as ASN.1 and Sun XDR. This paper presents the design of USC and a comprehensive set of experiments that compares USC performance with the best manually generated code and traditional stub compilers.
Spin-block synchronization algorithm in the shared memory multiprocessor system
Authors: Seung-Ju Jang , Gil-Yong Kim
Published: October 2004

Implemmentation of efficient synchronization algorithm is imporant in the parallel processing computer. Everyone usually say that implementation of synchronization in the parallel processing computer is a necessary evil. That is, synchronization in the parallel processing computer is positively necessary when user access shared resources in the computer system. But using of the wrong synchronization algorithm makes to many troubles in the parallel processing computer. In this paper proposed new algorithm of spin-block synchronization algorithm with multiprocessor system. This is based on type of queue lock and block lock. In this paper's queue lock is modified queue lock. So this type of new lock algorithm is spin-block algorithm. The Spin-Block synchronization algorithm's performance is evaluated by statistical analysis. The Spin-Block lock algorithm is alternative possibility to spin lock or block if any case in system overload. Finally, this algorithm is evaluated by performance model among traditional other lock algorithm. In this experiment we concluded that Spin-Block lock algorithm is good response time among other traditional lock algorithms.
Linkage in the Nemesis single address space operating system
Authors: Roscoe Timothy
Published: October 2004

The recent interest in single address space operating systems has resulted in a number of papers, most of which gloss over the issues of linking programs to run in multiple protection domains. Some of the confusion about 64-bit address spaces is due to the almost pervasive use of UNIX and UNIX-like operating systems (such as Mach, Chorus and Amoeba) and languages with poor enforcement of abstraction like C and C++.This paper describes some of the linkage structure of Nemesis, a multi-service operating system being developed as part of the Pegasus project. Nemesis provides a simple and efficient mechanism for program linkage which provides rich sharing of text at a level of individual object classes.
A brief survey of systems providing process or object migration facilities
Authors: Nuttall Mark
Published: October 2004

Migration is the movement of an active entity from one machine to another during execution. Such migration may be used for dynamic load balancing purposes with the aim of gaining increased performance from a group of processors than may be gained by schemes simply allocating processes to processors at run time. Schemes providing object migration also offer object persistence, improved fault tolerance and potentially more efficient remote object invocation (RPC).The survey covers systems providing process migration over both modified and unmodified UNIX and various experimental operating systems. Task migration over two modern microkernel-based operating systems is followed by a section on a number of object migration facilities with objects of varying granularity.
The shifting software development paradigm
Authors: Welke Richard J.
Published: October 2004

A thesis is put forward that there is a paradigm shift underway in how (information) systems, and the software which supports them, are developed. The shift is away from a craft-based structure in which user requirements are specified and custom solutions developed, to a market-generated, product-based approach in which users themselves select and arrange meaningful-to-them components as solutions to their requirements. There are several drivers to this shift. First, there are the numerous problems inherent in the methods now being used (expensive, time-consuming, myopic, inflexible). Second, there is a software technology objects which enables such a shift to take place. This paper examines these drivers, the ensuing development paradigm shift, and some of its many implications.
TimeBench
Authors: Buhr R. J. A. , Karam G. M. , Woodside C. M. , Casselman R. , Franks G. , Scott H. , Bailey D.
Published: October 2004

This paper provides an overview of
TimeBench
, a prototype CAD tool for designing real-time systems, as well as some experiences gained through building and using it. TimeBench aims to support a true engineering design process for real-time systems in a largely graphical working environment. The environment includes support for design synthesis, analysis, and system generation, with equal emphasis on the design of operational structure and the design of temporal behavior. Its main features include: (1) a hybrid graphical---textual design description notation (
MachineCharts, Abstract Controller Machines
, and
MachineChart Language
), (2) design experimentation through an embedded interpreter and behavior visualization tools to animate designs, (3) further design evaluation through a performance modelling tool based on fast approximate analystic methods, and (4) a code generation system than can be tailored to produce code for a desired environment.
A tool for the deterministic scheduling of real-time programs implemented as periodic Ada tasks
Authors: Giering E. W. , Baker T. P.
Published: October 2004

In this paper, we describe an experimental tool for the scheduling and execution of real-time programs on a single processor. This tool accepts a real-time program implemented as a system of periodic tasks written in a subset of Ada. It translates the program into equivalent Ada source code in which the task bodies are executed by a run-time dispatcher according to a deterministic, cyclic schedule.The schedule is represented as a table of scheduling actions describing the execution of the program for a
major cycle
, which is repeated at intervals of the
major period
of the least common multiple of all task periods. Each scheduling action covers an interval in the major cycle, and specifies a sequence of statements within a task that is to be executing during that interval. A compile-time scheduler arranges these scheduling actions within the major cycle such that all timing and rendezvous constraints will be satisfied. The periodic Ada tasks all start simultaneously (there is no task phasing), so that the schedule satisfying all constraints in the first major cycle can be repeated indefinitely.A simple example of a translation is presented, and the results of using this tool to schedule and execute some experimental task systems are described.
Interfacing Ada with verification languages
Authors: Leeson David , MacEwen Glenn , Andrews David
Published: October 2004

Ada is a general purpose programming language suitable for use in large applications and/or embedded real-time applications. However, its use in verification, i.e., the mathematical proof that a program's implementation is consistent with its specification, poses significant problems.One potential solution to this problem is to allow the integration of Ada software with other software that has been verified. The implications of integrating Ada with a verification language extend well beyond the technical challenge of developing language-heterogenous software systems. Not only must one implement a way to allow this integration, but one must do it in such a way as to not invalidate the underlying assumptions of the verification effort.The question as to whether it makes sense to integrate trusted (verified) and untrusted (Ada) software is addressed. The conclusion is that with proper decomposition, and the understanding that the goal is to verify specific properties and not entire programs, it is feasible to do this and still maintain the validity of the verification effort.Several integration approaches are presented. The most promising, separate processes communicating via remote procedure calls, is studied in more detail and a high level design for an implementation is described.
Privacy enhanced mail design and implementation perspectives
Authors: Sadok D. F. Hadj , Kelner Judith
Published: October 2004

The introduction of public key crypto-systems has opened the way to using security in distributed applications without imposing huge management overhead. Electronic mail is one area where security is important. Privacy Enhanced Mail is emerging as a de-facto international standard for the interchange of secure e-mail.This paper discusses some of the current problematic issues of PEM and introduces a PEM User Agent developed to test some of its concepts. A number of PEM design and implementation issues are explained and a conclusion on the future directions of PEM and other related work is given.
Minimising packet copies in multicast routing by exploiting geographic spread
Authors: Kadirire James
Published: October 2004

Routing connections in a point-to-point network is typically treated as a shortest path problem in a graph. Nodes represent switching systems, edges represent links and the edge lengths represent the costs associated with using a link. With multicast routing, one is interested in the shortest subtree of the network containing a given set of hosts. This is essentially a Steiner Tree problem in graphs and is known to be NP-complete [Karp]. Traditionally, the multicast routing algorithms proposed for packet switched networks like asynchronous transfer mode (ATM) networks have been aimed at minimising the total link cost of the Steiner tree [Waxman88], [Jaffe83] and do not take the geographical spreading of the connections into account. A dynamic point-to-multipoint routing algorithm is proposed, which takes into account the concept of geographic spread (also defined) of the connections and its performance is evaluated against the KMB near optimal heuristic algorithm for solving the Steiner tree problem [Kou].
A scalable and efficient intra-domain tunneling mobile-IP scheme
Authors: Aziz Ashar
Published: October 2004

Several schemes have recently been proposed in order to solve the problem of routing IP packets to a Mobile Host (MH). Some of these schemes have problems of compatibility with existing networks. The scheme that has the least compatibility problems, has efficiency problems in scaling the scheme to large and wide-area networks. This paper proposes extensions to the more compatible mobile IP scheme in order to provide better scaling properties to wide-area networks and large campus environments.
Exception Handling in Ada-94
Authors: Gauthier Michel
Published: October 2004

This paper is intended as a study of the new Ada features about exceptions, as compared to the initial requests of the Ada community. We have only considered :•the initial requests, summarized in the document "Ada 9X Revision Requests • August 1989".•the requirements of the project managing team, built from the users' requests, expressed by the document "Ada-9X Requirements • December 1990".•the final draft standard submitted to ISO ballot "Reference Manual for the Programming Language Ada • Version 5.0 • June 1994".•and the corresponding "Rationale".No attempt at a historical view on intermediate stages has been made.Some comments, suggestions of use and relations to concepts follow. However, it should be clear that exceptions remain a language feature which is suitable for implementing operation reports, and that the problems and difficulties raised by the general report concept are not considered here in full depth, but only as a survey of a few useful principles.Note: this paper is not targeted to Ada lawyers, but rather to programmers who ask what is new with exceptions.
CLANGER
Authors: Roscoe Timothy
Published: October 2004

C
langer
is a powerful, yet simple, command language for the Nemesis operating system. It uses runtime type information to interface directly with operating system components. C
langer
is a combination of command-line interpreter, scripting language, debugger and prototyping tool. This paper describes why such a language is possible, how it is being implemented, and outlines the language as it currently stands.
Adaptable object migration
Authors: Lux Wolfgang
Published: October 2004

Migration is one example of the insufficiently used potentials of distributed systems. Although migration can enhance the efficiency and the reliability of distributed systems, it is still rarely used. Two limitations contained in nearly all existing migration implementations prevent a widespread usage: migration is restricted to processes and the migration mechanism, i.e. the way state is transferred, is not adaptable to changing requirements.In our approach, migration is an operation provided by every object of any type. Triggered by higher level migration policies, the object migrates itself using an object-specific migration mechanism. Changing requirements are handled by higher level migration policies that adapt migration by exchanging the object's mechanisms.Adaptable migration was implemented within the BirliX operating system. Different migration mechanisms are accomplished by different meta objects, which can be attached to other objects. If an object has to be migrated, the meta object does the migration. Changing environmental requirements are handled by exchanging the meta object. As a result, each object has its own migration mechanism. The approach has been examined by implementing a couple of well-known migration mechanisms via meta objects. This paper describes the meta object implementation of the Charlotte migration mechanism.
The satanic notations
Authors: Hemaspaandra Lane A. , Vollmer Heribert
Published: October 2004

We explore the potentially "off-by-one" nature of the definitions of counting (#P versus #NP), difference (DP versus DNP), and unambiguous (UP versus UNP; FewP versus FewNP) classes, and make suggestions as to logical approaches in each case. We discuss the strangely differing representations that oracle and predicate models give for counting classes, and we survey the properties of counting classes beyond #P. We ask whether subtracting a #P function from a P function it is no greater than necessarily yields a #P function.
Fragmentation considered harmful
Authors: Kent Christopher A. , Mogul Jeffrey C.
Published: October 2004

Internetworks can be built from many different kinds of networks, with varying limits on maximum packet size. Throughput is usually maximized when the largest possible packet is sent; unfortunately, some routes can carry only very small packets. The IP protocol allows a gateway to
fragment
a packet if it is too large to be transmitted. Fragmentation is at best a necessary evil; it can lead to poor performance or complete communication failure. There are a variety of ways to reduce the likelihood of fragmentation; some can be incorporated into existing IP implementations without changes in protocol specifications. Others require new protocols, or modifications to existing protocols.
Intelligent congestion control for ABR service in ATM networks
Authors: Siu Kai-Yeung , Tzeng Hong-Yi
Published: October 2004

The emergence of asynchronous transfer mode (ATM) technology has generated new challenging problems for computer network designers. One of these challenges lies in the efficient management of ATM traffic so that the communication bandwidth of the network can be optimally utilized. Considerable standardization efforts in recent ATM Forum activities have been centered on the traffic management of available bit rate (ABR) service. In this paper, we examine congestion control schemes for ABR service in ATM networks. We describe a rate-based scheme that is now referred to by the ATM Forum as 'intelligent congestion control' and is currently considered as one of the most promising approaches. Moreover, we present analytical and simulation results illustrating the characteristics of the proposed scheme.
An efficient and secure authentication protocol using uncertified keys
Authors: Kao I.-Lung , Chow Randy
Published: October 2004

Most authentication protocols for distributed systems achieve identification and key distributions on the belief that the use of a uncertified key, i.e. the key whose freshness and authenticity cannot be immediately verified by its receiving principal while being received, should be avoided during the mid-way of an authentication process. In this paper we claim that using a uncertified key prudently can give performance advantages and not necessarily reduces the security of authentication protocols, as long as the validity of the key can be verified at the end of an authentication process. A nonce-based authentication protocol using uncertified keys is proposed. Its total number of messages is shown to be the minimal of all authentication protocols with the same formalized goals of authentication. The properties which make the protocol optimal in terms of message complexity are elaborated, and a formal logical analysis to the protocol is performed. The protocol is extended to counter the session key compromise problem and to support repeated authentication, in a more secure and flexible way without losing its optimality.
The information transfer specialist in successful implementation of decision support systems
Authors: Welsch Gemma M
Published: October 2004

This research investigates the role of the information transfer specialist as a technical intermediary and integrating agent in the acceptance and effective utilization of decision support systems (DSS). A multi-dimensional measure of perceived DSS implementation success is presented as the dependent variable, and the facilitative and technical functions of the specialist are specified as the independent variables. Measurement scales are developed for both sets of variables and the psychometric properties of the scales are tested using hierarchic cluster analysis for scale construction and Chronbach's alpha for scale reliability. Forty-five mature decision support systems served to field test the measurement scales and the research hypotheses. The findings show a positive correlation between the presence of an information transfer specialist and perceived DSS implementation success.
Multicast and multiprotocol support for ATM based Internets
Authors: Armitage G. J.
Published: October 2004

Both the Internet Engineering Task Force (IETF) and ATM Forum are addressing the issue of building higher layer networks using ATM. The IETF's focus is on IP, while the ATM Forum has expanded its vision to include all common Network layer protocols. The task faced by both organizations is to develop solutions that will cause minimal interoperability problems, both for users and network architects.

This paper focuses on the solutions coming out of the IETF's IP over ATM working group, including the author's proposal for flexible, high performance IP multicast over ATM. The emerging Next Hop Resolution Protocol from the IETF's Routing Over Large Cloud group is briefly examined, and its possible conflict with the ATM Forum's Multiprotocol Over ATM'work is also discussed. The author finishes by noting how current IETF work could support 'multiprotocol' networks.
Design principles and performance analysis of SSCOP
Authors: Henderson Thomas R.
Published: October 2004

The Service Specific Connection Oriented Protocol (SASCOP) has been approved recently as a new B-ISDN ATM Adaptation Layer (AAL) protocol standard, initially for use in the Signaling ATM Adaptation Layer (SAAL), but also for support of certain types of use data transfer. SSCOP is a new type of protocol, embodying several design principles for high speed link and transport layer protocols. In this paper, the basic operation of SSCOP is described and the SSCOP design is compared with other similar protocols. Next, the relationships between key protocol parameters (protocol window, control message transmission interval) and maximum achievable throughput effieiency are explored. In particular, approximate performance equations are derived for predicting the maximum throughput efficiency of SSCOP basedon the selected environment and parameter eettings. The equations can be used to determine how much buffer capacity and/or what protocol timer settings allow SSCOP to operate at high performance. The analytical results are confirmed through comparison with simulation results. In addition, simulation results illustrate the high throughput performance achievable when using SSCOP in a highly errored or loosy environment.
The ATM physical layer
Authors: Rao Sailes K. , Hatamian Mehdi
Published: October 2004

In this article, we present an overview of the physical layer specification of the emerging Asynchronous Transfer Mode (ATM) networks. These specifications concern the complete details of how to ship 53-byte ATM cells from Point A to Point B over a physical medium on a Local Area Network (WAN). While the task of defining the interfaces and line coding of the transceivers over different physical media is ongoing, the primary underlying theme has been the leveraging of existing standards and practices to the maximum extent possible.
Perspectives on ATM switch architecture and the influence of traffic pattern assumptions on switch design
Authors: Simcoe Robert J. , Pei Tong-Bi
Published: October 2004

Switch designs and the uniform distribution traffic pattern that has been the basis of much switch design analysis are discussed. In particular it is shown that head of line blocking is not the major cause of switch and link underutilization. Switch fabric and buffer system input bandwidth tradeoffs are described. For client server applications it is shown that having the majority of switch buffers on the input side of a switch reduces overall switch buffering.
Optimal Mutex policy in Ada 95
Authors: Abu-Ras Jim
Published: October 2004

Priority inversion is any situation where low priority tasks are served before higher priority tasks. It is recognized as a serious problem for Real-Time Systems. In this paper, we present some of the important features of the Real-Time Annex of Ada 95. We also implement the
Optimal Mutex Policy (OMP)
in Ada 95 to better illustrate Ada's new usefulness for Real-Time programming. A detailed discussion of this protocol and other related issues are presented.
Performance problems in BSD4. 4TCP
Authors: Brakmo Lawrence S. , Peterson Larry L.
Published: October 2004

This paper describes problems in the BSD 4.4-Lite version of TCP (some of which are also present in earlier versions, such as the Net2 implementation of TCP) and proposes fixes that result in a 21% increase in throughput under realistic conditions.
Diffusion of innovation theory
Authors: Prescott Mary B.
Published: October 2004

Innovation diffusion theory has been widely applied to the study of information technology (IT) innovations for more than the last decade and has provided insight into the adoption, implementation, infusion, and diffusion of IT innovations. This stream of research has strong potential for contributing both to the development of innovation diffusion theory and to providing pragmatic guidance to practitioners faced with the often difficult task of successfully introducing a new information technology or method to the workplace. Brief summaries are included of the five articles in this special issue of the
DATA BASE for Advances in Information Systems,
which is devoted to information technology adoption, implementation, and diffusion.
Adoption intention in GSS
Authors: Chin Wynne W. , Gopal Abhijit
Published: October 2004

Models used to study information technology (IT) adoption were adapted and applied to the group support systems (GSS) domain to determine their applicability and to assess the relative importance of beliefs about GSS in the context of adoption. The beliefs examined were relative advantage, ease of use, compatibility, and enjoyment. Four methods of measuring the relative importance of the belief constructs in predicting GSS adoption intention were evaluated. The methods involved Likert-scaled measures, conjoint measures, direct ratings of importance, and paired comparisons. Compositional analyses using three distinct models, regression, molar, and molecular, were conducted to examine the data collected under the first method. The results of the study demonstrated that the models and constructs used in other IT domains are indeed applicable in the GSS context. The relative importance of the beliefs did not converge across methods, although there was some agreement among the three compositional approaches as well as among the conjoint, direct rating, and paired comparison methods. The results point to the need for caution in utilizing and interpreting regression results and demonstrate the viability of alternative methods of studying adoption.
Telework
Authors: Ruppel Cynthia P. , Harrington Susan J.
Published: October 2004

Despite predictions over the years that many employees would soon be teleworking from their homes, neither employees in general nor information systems (IS) professionals in particular, whose work is especially appropriate for telework, have begun teleworking to any large extent. The reasons for this lack of telework growth are empirically untested. Yet an understanding of why organizations and IS departments are not joining the telework bandwagon is critical if predictions of improved flexibility and productivity through telework are to be realized.This study used innovation theory to suggest key variables that may be related to telework use among IS programmer/analysts. A national survey of IS executives was used to obtain information on the variables relevant to IS telework assimilation. The survey resulted in responses from 252 IS departments describing their telework arrangements.Key variables related to both the adoption stage and the infusion stage of IS teleworking were middle management support for telework, administrative intensity, and professionalism. A variable significantly related only to the adoption decision was centralization. The key variable related only to the infusion stage was size. The variables that were not related to either adoption or infusion were specialization and formalization, suggesting that bureaucracy alone is not an obstacle to telework.Overall, the findings suggest a bottom-up initiation of telework; i.e., that programmer/analysts are initiating telework arrangements. Lack of middle management support for telework has a strong negative effect on the assimilation of telework. Thus, this study suggests that future research may wish to investigate further the reasons for lack of managerial support. Moreover, the lack of organizations getting on the telework bandwagon, together with the variables found significant in this study, suggest fruitful areas for future research may be an analysis of the type of publicity describing telework arrangements, managerial knowledge of telework arrangements, the nature of IS work appropriate for telework, and the managerial skills demanded by telework.
Adoption of computer aided software engineering (CASE) technology
Authors: Premkumar G. , Potter Michael
Published: October 2004

This study examines the impact of various organizational and technology characteristics on the adoption of computer aided software engineering (CASE) technology. Based on research in innovation adoption and IS implementation, the study develops a research model comprised of seven factors that are important for the successful adoption of CASE technology. The data for the study were collected through a field survey of IS managers in the midwest area and 90 responses were received. The results of discriminant analysis reveal that of the seven predictor variables, five are important to differentiate adopters from non-adopters. They are the existence of a product champion, strong top management support, lower IS expertise, perception that CASE technology has greater relative advantage over other alternatives, and a conviction of the cost effectiveness of the technology. The results are consistent with findings in innovation adoption literature as well as case studies of many firms' experience on CASE implementation.
A measurement-based admission control algorithm for integrated services packet networks
Authors: Jamin Sugih , Danzig Peter B. , Shenker Scott , Zhang Lixia
Published: October 2004

Many designs for integrated service networks offer a bounded delay packet delivery service to support real-time applications. To provide bounded delay service, networks must use admission control to regulate their load. Previous work on admission control mainly focused on algorithms that compute the worst case theoretical queueing delay to guarantee an absolute delay bound for all packets. In this paper we describe a
measurement-based
admission control algorithm for
predictive
service, which allows occasional delay violations. We have tested our algorithm through simulations on a wide variety of network topologies and driven with various source models, including some that exhibit long-range dependence, both in themselves and in their aggregation. Our simulation results suggest that, at least for the scenarios studied here, the measurement-based approach combined with the relaxed service commitment of predictive service enables us to achieve a high level of network utilization while still reliably meeting the delay bound.
Two issues in reservation establishment
Authors: Shenker Scott , Breslau Lee
Published: October 2004

This paper addresses two issues related to resource reservation establishment in packet switched networks offering real-time services. The first issue arises out of the natural tension between the local nature of reservations (i.e., they control the service provided on a particular link) and the end-to-end nature of application service requirements. How do reservation establishment protocols enable applications to receive their desired end-to-end service? We review the current one-pass and two-pass approaches, and then propose a new hybrid approach called one-pass-with-advertising. The second issue in reservation establishment we consider arises from the inevitable heterogeneity in network router capabilities. Some routers and subnets in the Internet will support real-time services and others, such as ethernets, will not. How can a reservation establishment mechanism enable applications to achieve the end-to-end service they desire in the face of this heterogeneity? We propose an approach involving replacement services and advertising to build end-to-end service out of heterogeneous per-link service offerings.
Software support for outboard buffering and checksumming
Authors: Kleinpaste Karl , Steenkiste Peter , Zill Brian
Published: October 2004

Data copying and checksumming are the most expensive operations when doing high-bandwidth network IO over a high-speed network. Under some conditions, outboard buffering and checksumming can eliminate accesses to the data, thus making communication less expensive and faster. One of the scenarios in which outboard buffering pays off is the common case of applications accessing the network using the Berkeley sockets interface and the Internet protocol stack. In this paper we describe the changes that were made to a BSD protocol stack to make use of a network adaptor that supports outboard buffering and checksumming. Our goal is not only to achieve "single copy" communication for application that use sockets, but to also have efficient communication for in-kernel applications and for applications using other networks. Performance measurements show that for large reads and writes the single-copy path through the stack is significantly more efficient than the original implementation.