bluuebunny/crossref_metadata_2025 huggingface dataset:
A NEW SCHEME TO PROTECT CONFIDENTIAL IMAGES
Authors: Chang Chin-Chen , Hwang Ren-Junn
Published: October 2004

A new and efficient scheme to protect confidential images is proposed in this paper. The proposed scheme does not use a secret key to protect confidential images as conventional encryption schemes do, and nor are there cipher images corresponding to the confidential images. A confidential image can be reconstructed easily by the cooperation of all the participants in a special group. Each participant of the special group holds a virtual image which can show any picture, and she/he uses this virtual image to cooperate with the other legal participants to reconstruct the confidential image. These pictures shown in the virtual images are significantly different and are irrelative to each other. Besides, they bear no relation to the confidential image either. According to our experimental results, each reconstructed confidential image which does turn out to look like the original confidential image through our human visual system and its PSNR is greater than 34 dB for 256 gray level images.
RUN-TIME ADJUSTED CONGESTION CONTROL FOR MULTIMEDIA: EXPERIMENTALS RESULTS
Authors: DE MARCO GIUSEPPE , LONGO MAURIZIO , POSTIGLIONE FABIO
Published: October 2004

Multimedia communications over Internet should achieve adequate quality of service (QoS) while maintaining 'fairness' in network resources allocation with respect to competing connections. The fairness is usually achieved by means of the congestion control, which could induce high variations on the perceived throughput and then affecting the QoS. On the other hand, the variations of throughput of the multimedia communication can be neglected if a minimum average throughput is guaranteed to the playout buffer used by the application. These considerations can be exploited to solve the conflicting requirements of fairness and QoS. The transport protocol proposed here is a modified version of the window-based datagram congestion control protocol, that implements a TCP-like congestion control mechanism wherein the multiplicative decrease of the congestion window is controlled by a non-linear function. Experimental results show that this modified congestion control algorithm, which in turn is adjusted at run-time based on the estimated mean round-trip time, is capable to provide the average throughput required by the encoding technique adopted for the multimedia data compression, while guaranteeing the required fairness with respect to competing TCP connections.
NETWORK-CENTRIC STRATEGY FOR MOBILE TRANSACTIONS
Authors: YOUNAS MUHAMMAD , AWAN IRFAN , CHAO KUO-MING
Published: October 2004

Mobile transaction technology ensures reliability, data consistency, and concurrency in mobile computing applications. Current solutions develop numerous transaction models and protocols in order to enhance the reliability and improve the performance of mobile transactions. However, they give no attention to the underlying network on which mobile transactions are carried out. This paper presents a network-centric strategy in order to improve the performance of mobile transactions. The proposed strategy is based on employing preemptive resume scheduling mechanism in mobile transactions. A cost effective analytical model for the network node with bursuty arrival traffic and prioritised scheduling mechanism has been developed using maximum entropy (ME) methodolgy. It involves rigorous analysis of a network node with finite capacity to accommodate messages, bursty arrival process to represent incoming multi-class messages, and the employment of a priority scheduling mechanism to give preferential treatment to high priority messages. This analytical solution provides closed form expressions for calculating the queuing delay per class involved in the commit processing of mobile transactions. The aim is to reduce queuing delays involved in the processing of mobile transactions at each network node. Such reduction of queuing delay significantly improves the performance of mobile transactions given the heavy network traffic and the lower network bandwidth. Several experiments have been conducted using the analytical modelling approach, which determine the impact of priority scheduling mechanism on the performance of mobile transactions. Experiments show significant performance improvements of the proposed strategy over existing approaches.
Performance Analysis of Mobile Agents in Mobile Distributed Information Retrieval System – A Quantitative Case Study
Authors: Jiao Yu , Hurson Ali R.
Published: October 2004

The traditional client/server-based distributed system design paradigm demonstrates deficiencies in the mobile computing environment because it relies on network connectivity and reliable communication. The advances in mobile agent technology alleviate these problems. The execution autonomy of mobile agents relaxes the requirement on network connectivity and provides opportunities for conserving energy. To the best of our knowledge, in spite of the large body of research in the application and exploitation of agent-based technology, a quantitative comparison of systems implemented using the client/server and agent-based models is still missing and issues related to the energy efficiency of mobile agents remain unexplored. In this paper, we present a quantitative performance evaluation of these two models in terms of response time, energy consumption, and communication cost.
Factors influencing the adoption of web-based shopping
Authors: Van Slyke Craig , Belanger France , Comunale Christie L.
Published: October 2004

Business-to-consumer electronic commerce (e-commerce), one form of which is Web-based shopping, is defined as electronic-based economic transactions conducted between individual consumers and organizations. While this form of e-commerce is forecast to grow rapidly for the foreseeable future, it still represents only a small fraction of total consumer spending. To better take advantage of and be prepared for this economic phenomenon, organizations need to identify and understand factors that may impact consumers' decisions to engage in Web-based e-commerce. Recently, the importance of trust has been discussed in both the academic and practitioner press. The impact of trust on the use of e-commerce has been established empirically. The research reported here builds on those findings by establishing that not only is trust in Web merchants significantly related to purchase intentions via the Web, but this significance holds even when other, more traditional perceptions are considered. A survey of consumers was conducted and results indicate that trust in Web merchants is positively related to intentions to make purchases from Web merchants, even when the impact of other perceived innovation characteristics are considered. The research also contributes to the literature on technology adoption by verifying the impact of perceived innovation characteristics on adoption intentions.
'Why didn't somebody tell me?'
Authors: Keil Mark , Smith H. Jeff , Pawlowski Suzanne , Jin Leigh
Published: October 2004

The reluctance to transmit bad news is a problem that is endemic to many organizations. When large projects go awry, it often takes weeks, months, and sometimes even years, before senior management becomes fully aware of what has happened. Accurate communication concerning a project and its status is therefore critical if organizations are to avoid costly and embarrassing debacles. This paper describes the results of an experiment designed to explore some key variables that may influence an individual's willingness to report bad news in an information systems project context. We extend a basic theoretical model derived from the whistle-blowing literature by considering relevant constructs from agency theory. We then test the entire model using a controlled experiment that employs a role-playing scenario. The results explain a significant portion of the variance in the reluctance to report negative status information. Implications for research and practice are discussed, along with directions for future research.
Microprogrammed random access stored program machines
Authors: Smith Carl H. , van Leeuwen J.
Published: October 2004

We present a typical framework for microprogramming using a well-known theoretical computer-model.
Notes on "A note on the transitive closure of a boolean matrix"
Authors: Yelowitz Lawrence
Published: October 2004

The row-oriented algorithm in [1] for obtaining transitive closure is Dijkstra's algorithm [2] (for obtaining all nodes reachable from a single node) applied to each row in turn. Furthermore, [1] does not work properly in the acyclic case unless the matrix is in triangular form initially. In general, it may be necessary to renumber the nodes (and correspondingly rearrange the matrix) to bring an acyclic adjacency matrix into triangular form (a technique such as topological sorting [3] can be used). Finally, if interest is in obtaining the nonredundant digraph of an acyclic digraph, [4] appears to be a more efficient algorithm than [5].
Algebraic implementation of abstract data types
Authors: Ehrig H. , Kreowski H. J. , Padawitz P.
Published: October 2004

A new concept for the implementation of abstract data types is proposed: Given algebraic specifications SPECO and SPEC1 of abstract data types ADTO and ADT1 an implementation of ADTO by ADT1 is defined separately on the syntactical level of specifications and on the semantical level of algebras. In addition to a short overview a simple example is provided.
On folk theorems
Authors: Harel David
Published: October 2004

We suggest criteria for a statement to be a folk theorem and illustrate the ideas with a detailed example.
Cryptographic technology
Authors: Diffie Whitfield
Published: October 2004

This paper examines the forces driving public development of cryptography today and projects the course of the field over the next fifteen years with attention to the possible influence of government regulation.This paper was prepared, under contractual arrangements to CRC Systems, in support of the Commerce Department (National Telecommunications and Information Administration, Special Projects Office) response to a White House Office of Science and Technology Policy request that the secretaries of the Departments of Commerce and Defense propose a national policy on cryptography.
Iterative vs. regular factor algebras
Authors: Guessarian Irène , Parisi-Presicce Francesco
Published: October 2004

We characterize the free regular algebra in any variety of regular algebras as a factor algebra and prove that no similar characterization can be obtained for varieties of iterative or continuous algebras.
The effect of paged memory upon algorithm performance
Authors: Moffat Alistair
Published: October 2004

We investigate the effect of a common memory management scheme on the running times of some simple algorithms. We find that some otherwise comparable algorithms have markedly different performance under this new algorithm metric.
The game of academe
Authors: Coren Stanley
Published: October 2004

A game simulating the progress of a professor through the ranks of academe is offered. This simulation includes many of the most relevant aspects of university life, such as teaching, administration and research. Because it is faithful to the rules of the real life academic situation, its actual playability is somewhat suspect.
An artificial intelligence technique to generate self-optimizing experimental designs
Authors: Findler Nicholas V. , Cromp Robert F.
Published: October 2004

The paper describes a completed and independent module of a large-scale system, the Quasi-Optimizer (QO). The QO system has three major objectives: (i) to observe and measure adversaries' behavior in a competitive environment, to infer their strategies and to construct a computer model, a descriptive theory, of each; (ii) to identify strategy components, evaluate their effectiveness and to select the most satisfactory ones from a set of computed descriptive theories; (iv) to combine these components in a quasi-optimum strategy that represents a normative theory in the statistical sense.The measurements on the input strategies can take place either in a sequence of confrontations unperturbed by the QO, or, for efficiency's sake, in a series of environments specified according to some experimental design. The module completed first, QO-I, can perform the experiments either in an exhaustive manner---when every level of a decision variable is combined with every level of the other decision variables---or, in relying on the assumption of a monotonically changing response surface, it uses the binary chopping technique.The module discussed here, QO-3, does not assume monotonic response surfaces and can deal also with multidimensional responses. It starts with a (loosely) balanced incomplete block design for the experiments and computes dynamically the specifications for each subsequent experiment. Accordingly, the levels of the decision variables in any single experiment and the length of the whole sequence of experiments depend on the responses obtained in previous experiments. In general, QO-3 is an on-line, dynamic generator of experimental design that minimizes the total number of experiments performed for a predetermined level of precision.
On non-hierachical systems of binary operators
Authors: Cooke D. J.
Published: October 2004

In a previous paper [3] a system was described by which context-sensitive grammars could be used to specify balanced derivations of certain expressions; such derivations corresponding in a natural way to balanced semantic trees appropriate for parallel execution. The earlier work was only applicable to expressions involving a strictly ordered hierachy of binary operators. This note shows how under certain "
reasonable
" algebraic constraints the method can be extended to less well-behaved situations.
Survey on classes of interpretations and some of their applications
Authors: Guessarian Irène
Published: October 2004

We introduce classes of interpretations. We characterize the free and Herbrand interpretations for a class. We define the algebraic, equational, relational and first-order classes of interpretations, study their properties and relate them to the literature. We apply this study to derive complete proof systems for deducing (in some (in) equational logic) all (in) equalitions valid in a class.
Midwest theory of computation symposium
Authors: Hakimi S. Louis , Kariv Oded
Published: October 2004

Bounds are given on the number of colors required to color the edges of a graph (multigraph) such that each color appears at each vertex v at most m(v) times. The known results and proofs generalize in natural ways. Certain new edge-coloring problems, which have no counterparts when m(v) = 1 for all vεV, are studied.
Ada as a preprocessor language
Authors: Baker P. L.
Published: October 2004

Preprocessors are components of a software development environment that can increase productivity by providing semantic capabilities for expressing certain source language statement s concisely and directly which would otherwise be expressed indirectly and verbosely. Moreover, it is frequently necessary to reflect a single programming decision in several places in the source text; a preprocessor can propagate a single specification of such a decision to the points it affects thereby reducing effort and removing the possibility a consistency error. In traditional environments, the language of preprocessor statements differs from the underlying programming language, e.g., CPP differs from C itself. If such deviations were allowed in an Ada environment, they would impair portability and detract from the effort to provide widespread, uniform language training in pure Ada. This paper demonstrates, however, that Ada is, by itself, a viable preprocessor language provided two conventions are adopted. First, the compilation sequence of preprocessing must be used; fortunately, an Ada compiler can serve in a preprocessor step without affecting its validation under the ACVC. Second, normal and preprocessor statements are not intermixed; Ada package structure must be employed to separate contexts that would be differentiated by syntax in traditional preprocessing. The distinctive compilation sequence of Ada preprocessing is a multiple pass compilation where compilation steps are connected via Ada text, not Ada library units. The results of one compilation pass are converted to text via an execution step and then provided as text input to the next step. As an example, the paper describes a preprocessor that constructs subsystem interfaces.
UNIVERSAL_FILE_NAMES for Ada
Authors: Gail Wang Y. E.
Published: October 2004

This paper reports on UNIVERSAL_FILE_NAMES (UFN), a set of Ada components designed to provide filename portability between MS-DOS, Unix and VMS.
The form of reusable Ada components for concurrent use
Authors: Carter J.
Published: October 2004

Abstract data types are often chosen to implement reusable Ada components for sequential use. Those who have attempted to expand from sequential to concurrent considerations have frequently continued to use abstract data types for their implementation. This approach is shown to violate software engineering principles. The use of abstract state machines for concurrent components is shown to resolve these problems.
Design of a text formatter with AUTO STAR
Authors: Zhu M.
Published: October 2004

The formal development of a prototyping text formatter with the aid of AUTO STAR (AUTOmati c Specification To Ada Realization) has been introduced. This experiment shows that a large software system can be developed with a formal approach in a very easy and fast way.
A definition of lines of code for Ada
Authors: Winkler Juergen F. H.
Published: October 2004

The application of the principles and methods of modern software engineering requires the measurement of the essential factors of the software development process. One basic factor is the program size. Up to now no satisfactory definition of program size has been agreed upon. A popular definition of program size is "lines of code " (LOC) but even for this specific measure the situation is the same and there are different definitions of LOC in use. That is, for the same program we may obtain different values for its size.In this paper we report about a new definition of lines of code for Ada. This definition was developed at Siemens as part of an in-house standard, in which LOC is defined for different languages. This standard defines the number of all source lines as the gross size of a program and the number of all those lines which are essential for the correct execution of the program as the net size of a program. Furthermore, the standard distinguishes five sorts of lines which are important for a more detailed analysis of a program: statement, declaration, directive, comment, and separator lines.
Database theory column
Authors: Abiteboul Serge , Kanellakis Paris
Published: October 2004

Complex object databases have been proposed as a significant extension of relational databases, with many practical applications. In the second database theory column, we present languages for the manipulation of such databases: a many-sorted algebra and an equivalent calculus. Without attempting to standardize, we try to provide general and short definitions that highlight the two key constructors of complex objects: tuples and (finite) sets. We comment on issues, such as language expressive power and complexity, and we describe equivalent rule-based languages with fixpoint semantics. Finally, we review the state-of-the art in database complex objects and list some interesting open questions.
The current status of MAP
Authors: Foley J S , Weon-Yoon Y
Published: October 2004

MAP is a standard computer networking discipline and a unified set of communications protocols which make it possible to implement a vendor independent network of computers. MAP provides a complete service to the user or application program. The major facilities, file transfer, process to process messaging, inter-machine messaging, and directory service are supported. Virtual terminal protocol support is planned for the near future.

MAP is a subset of the internationally agreed Open Systems Interconnection computer networking architecture, protocols and supporting standards. The MAP subset of OSI Protocols was originally selected by General Motors and has been agreed by a MAP Task Force comprised of nearly 100 user and vendor corporations. MAP specifications are also agreed by the NBS/OSI Implementor's Workshop, indicating that the MAP specifications are OSI compatible.

The MAP System and Protocols are described here in sufficient detail to permit the reader to gain a general understanding of MAP against a background of OSI fundamentals. The future growth trends for MAP conclude this paper.
A comparison of two token-passing bus protocols
Authors: Rego V
Published: October 2004

A well known disadvantage of standard token-passing in ring and bus networks is the waste of channel bandwidth often seen in lightly loaded or asymmetric systems. It is possible to make use of the broadcast mechanism in token bus systems to distribute nearly up-to-date information about the state of individual stations to the entire system. One such scheme involves the determination of a randomly varying set of more active stations. These stations are given a chance to form a second logical ring above the standard logical ring that characterizes the token bus. The transmission cycles of the system can thus be made to alternate between standard token-passing and transmission cycles, and the cycles of token-passing and transmission within the logical ring of more active stations. We assume that each station makes at most one transmission when given the chance to transmit. For Poisson arrivals and otherwise general input distributions, the cycle-time distribution of the token is derived for each kind of cycle. An important random variable is the random token turnaround time seen by individual stations. For lightly loaded stations this time tends to be larger than for heavily loaded stations. The distribution of this random time, simple performance measures, and a comparative measure of stability, showing the adaptive scheme to be more stable than the standard, are obtained.
A verified sliding window protocol with variable flow control
Authors: Shankar A U
Published: October 2004

We present a verified sliding window protocol which uses modulo-
N
sequence numbers to achieve reliable flow-controlled data transfer between a source and a destination. Communication channels are assumed to lose, duplicate and reorder messages in transit. The destination's data needs are represented by a receive window whose size can vary with time. The destination entity uses acknowledgement messages to inform the source entity of the current receive window size and the sequence number of the data word next expected. The source entity responds by sending segments of data words that lie within the allowed window. Each data segment is accompanied by an identifying sequence number and the size of the data segment. The destination entity also uses selective acknowledgement and selective reject messages to inform the source entity of the reception or lack of reception, respectively, of out-of-sequence data segments. Thus, this protocol is a proper extension of the Arpanet's TCP. We have obtained the minimum value of
N
that ensures correct data transfer and flow control, in terms of the minimum message transmission time, the maximum message lifetime, and the maximum receive window size. The protocol imposes no constraints on the retransmissions of messages or on the data segment sizes; thus, any retransmission policy that optimizes the protocol's performance can be used.
Modeling a transport layer protocol using first-order logic
Authors: Lin H P
Published: October 2004

We use a hybrid model based on the first-order logic to specify and verify a transport layer protocol. In this model we specify a protocol as a set of state machines. Time expressions are used to describe the temporal relations of transitions. Given the specification of a protocol, we verify its properties by logical deduction. Reasoning techniques such as decomposition and abstraction are used to reduce the verification complexity.

The transport protocol consists of an active process, a passive process, and two communication channels. Each of these components is specified by this model. An outline of verification of this protocol is given.
An architecture for a multimedia teleconferencing system
Authors: Aguilar L , Garcia-Luna-Aceves J J , Moran D , Craighill E , Brungardt R
Published: October 2004

We present an object-oriented architecture for a computer-based, real-time, multimedia conferencing system. This architecture divides the system into five functional areas: a multimedia shared workspace, a user interface, conference management, communications, and an information base. The structure and operation of the first four areas are modeled with object-based concepts that address design requirements identified during the development of a proof-of-concept prototype, that preceded the architecture specification.

The shared workspace, the most important component, is thoroughly discussed; the other components support its realization. The modeling of workspace entities emphasizes their aggregation into composed entities and the homogeneous handling of several data media. The user interface manages uniformly the man-machine interaction for both local and remote user actions. Conference management deals with session establishment, participation, and control of multiple media floors. The communication functions replicate user actions over workspace objects in all hosts participating in a conference, matching traffic types with transmission services in the process.
Structure of a LOTOS interpreter
Authors: Briand J P , Fehri M C , Logrippo L , Obaid A
Published: October 2004

LOTOS is an executable specification language for protocols and services currently being standardized within ISO. It is based on an extended version of Milner's Calculus of Communicating Systems (CCS) and ACT ONE Abstract Data Type formalism. After a brief introduction to LOTOS, we give here an account of a prototype LOTOS interpreter, which includes an interactive system that allows the user to direct the execution of a specification. The interpreter was implemented in YACC/LEX, C, and Prolog. The discussion includes the following topics: syntax and static semantics analysis; translation from LOTOS external format to internal representation; evaluation of Abstract Data Type value expressions and CCS
*
clauses.
The butterfly satellite IMP for the wideband packet satellite network
Authors: Edmond W , Bumenthal S , Echenique A , Storch S , Calderwood T
Published: October 2004

Multiprocessor computer systems have proven effective as high performance switching nodes in packet switched data communications networks. They are well suited to performing the required queuing, routing, and scheduling tasks, and can scale upward to provide higher system throughput when combined with software that exploits the parallelism provided by the hardware. This paper describes the packet switch used in the DARPA Wideband Packet Satellite Network and the Butterfly™ Multiprocessor on which it is based.
Synthesis of two-party error-recoverable protocols
Authors: Ramamoorthy C V , Yaw Y , Aggarwal R , Song J
Published: October 2004

We have developed a correct, general, and efficient procedure of synthesizing two-party error-recoverable protocols for noisy channels where messages could be lost, corrupted, and/or missequenced. The state explosion problem has been tackled by synthesizing the error-recoverable protocol (ERP) from its noiseless local entity model using certain rules. This reduction arises from the approaches of local modeling and elaboration. We expect that these two approaches will also play a major role in tackling the complexity problems in designing multi-party protocols. Measures of efficiency and functionality improvements have been discussed.
Formal specification-based conformance testing
Authors: Sarikaya B
Published: October 2004

The paper discusses the use of formal specifications for conformance testing of OSI protocols and divides the discussion in two parts: test design and tester design. A draft standard formal specification of the Class 4 transport protocol in Estelle is taken as the starting point for test design. The test design technique used to derive a conformance test suite is semi-formal based in part on the formal specification and also the informal specification. The tests obtained are expressed in natural language. In the tester design part, we discuss the distributed test architecture of ISO and give the detailed designs of upper and lower testers. It is shown that, in testing Class 4 transport implementations, a parametrized protocol implementation approach in the lower tester design, renders the tests easier to implement.
A selective repeat ARQ scheme for point-to-multipoint communications and its throughput analysis
Authors: Chandran S R
Published: October 2004

Selective repeat automatic-repeat-request (ARQ) schemes with finite receiver buffer have been studied and analyzed extensively for point-to-point communications. In this paper, we propose a selective repeat ARQ scheme for point-to-multipoint communications where each receiver has a finite buffer size. A lower bound on the throughput efficiency of the proposed scheme is obtained. Computation of the lower bound and simulation of the scheme reveal that the ARQ scheme performs quite satisfactorily, particularly for channels with large round-trip delay and high data rate like the satellite channel. The proposed scheme outperforms the full-memory go-back-N scheme proposed by Gopal, et al. [13]. The scheme seems ideally suited for the case of a satellite operating in broadcast mode with many receivers.
A message-based fault diagnosis procedure
Authors: Agre J R
Published: October 2004

A new diagnostic message protocol that provides fault diagnosis capabilities for the communications in a distributed system environment is described. The protocol is designed to operate in conjunction with a standard end-to-end communication protocol and uses special messages to determine the system fault state. A diagnosis message is represented using a test dependency model that is derived from the system topology. These messages are used by an adaptive strategy designed to achieve specific objectives such as reduced testing cost. Using the test dependency model, a general purpose algorithm is developed for generating these strategies based on an information theory criterion. Specific properties of the protocol are discussed, and several examples of strategies for a distributed system topology are provided.
A study of dynamic load balancing in a distributed system
Authors: Hac A , Johnson T
Published: October 2004

This paper presents a study of a distributed system consisting of a number of hosts connected by a local area network. The system model is based on the LOCUS distributed file system. The LOCUS file system allows replicated files, and the synchronization policy is enforced by the use of the Centralized Synchronization Sites (CSS). All requests to open a file for access must be sent to the file's CSS which checks for access conflicts. Our simulation model allows process migration. The focus of this study is on load balancing as applied to optimal process and read site placement. An algorithm is proposed that increases system performance through load balancing. This algorithm uses data collected by the system on which to base its decisions. The characteristics of the algorithm and their effects on system performance are analyzed and discussed.
A resilient distributed protocol for network synchronization
Authors: Cimet I A , Srikanta Kumar P R
Published: October 2004

We present a resilient distributed protocol that enables a synchronous algorithm to run on an asynchronous network. The protocol is resilient in the sense that it can continue providing network synchronization in the presence of topological changes in the underlying communication network of a distributed system. These changes are caused by link/node failures and recoveries that occur while running the protocol. In general, the protocol is a useful tool in the design of resilient distributed algorithms as it isolates the algorithm from the characteristics of the communication network.
A turnable protocol for symmetric surveillance in distributed systems
Authors: Walter B
Published: October 2004

In distributed systems surveillance protocols are used for monitoring the status of remote sites. A remote site is regarded as being available as long as messages are received from this site, otherwise it is regarded as being unavailable. If a site becomes unavailable, this will be reported to other sites and recovery actions can be initiated. Using an example it will be shown that in certain cases it is necessary, that whenever some site S1 detects the unavailability of some other site S2, within a fixed amount of time S2 must also have detected an unavailability of S1. Unfortunately, this cannot be guaranteed by existing surveillance protocols. Another problem with existing protocols is, that remote sites are usually reported as being unavailable after being timed out only once, i.e. the loss of just one message might cause complete systems to back out.

Two versions of a protocol for so-called symmetric surveillance are presented. Both guarantee, that if S1 detects the unavailability of S2 at time t0, then S2 (provided that S2 has not crashed) will become aware of this fact at t1 such that [t1 - t0] < Δ. This property is of special interest for handling network partitionings. Additionally, one of the versions is tunable, i.e. it can be specified, how many timeouts may occur before a site is regarded as being unavailable.
Design issues of protocols for computer mail
Authors: Garcia-Luna-Aceves Jose J. , Kuo Franklin F.
Published: October 2004

In this paper we present major design considerations for the development of international computer mail protocols. A simplified functional model for computer mail systems is introduced to serve as the basis of the discussion of the protocols. The general framework of the Reference Model for Open System Architecture proposed by the ISO is followed in the description of the computer mail protocol and design issues involved at each layer of the computer mail protocol are examined. The computer mail protocol is aimed at non-interactive communication between message system users.
Insights into the implementation and application of heterogeneous local area networks
Authors: Lidinsky William P.
Published: October 2004

The ideal local area network is a mechanism which provides concurrent high speed error-free data paths over a limited geographical area and between any computational entities on the network. A computational entity may be a program running on any type of computer, any intelligent device, or any terminal. This means that such an ideal network must be able to support systems of cooperating processes within disjoint and dissimilar host environments.

Achieving such an ideal heterogeneous network (referred to as an “open” network with respect to the ISO Reference Model for Open Systems Interconnection) may be impossible in the limit. However, the ideal shows promise of being approachable. Recent work in local area networks, protocols, and multiprocessor operating systems looks promising for attacking the problem.

This paper first discusses data paths and the dilemma of heterogeneous data communications. Existing local area networks, their functionality, shortcomings, and relationship to networking standards are described. Commercial LANs are discussed and classified. Standards, high level protocols, and operating system concepts are discussed and related to networks. Finally some possible approaches to the implementation of hetergeneous networks are discussed.
Some cryptographic principles of authentication in electronic funds transfer systems
Authors: Meyer C. H. , Matyas S. M.
Published: October 2004

One essential requirement of an Electronic Funds Transfer (EFT) system is that institutions must be able to join together in a common EFT network such that a member of one institution can initiate transactions at entry points in the domain of another institution. The use of such a network is defined as
interchange
. Cryptographic implementations are developed for such a network in such a way as to keep personal verification and message authentication processes at different institutions completely separate. This is accomplished through the combined use of user-remembered personal identification numbers (PINs), secret system keys, and intelligent secure (bank) cards on which are recorded secret personal cryptographic keys.
A study of protocol analysis for packet switched network
Authors: Tsukamoto K. , Itoh T. , Nomura M. , Tanaka Y.
Published: October 2004

Communication failures may occur because of residual hardware or software implementation flaws, operator errors, transmission noises and transient or permanent machine failures. For packet switched network operation, some means are necessary to detect the errors and to analyze the phenomena to identify the causes of the errors, since, generally, it is almost impossible to predict errors or to implement systems without errors or failures.

This paper describes general aspects of communication protocol analysis, protocol analysis technologies for CCITT X.25 and the protocol analyzer to be used in DDX packet switched network operation.
A versatile queueing model for data switching
Authors: Laue Richard V.
Published: October 2004

In a data network, when messages arrive at a switch to be served (transmitted) on a line, it seems reasonable to assume that the arrival process can be described as a Poisson (random) process. However, when messages are divided into a number of packets of a maximum length, these packets arrive bunched together. This gives rise to what is referred to as “peaked” traffic. The degree of peakedness depends on 1) the interarrival time of packets associated with a particular message and 2) the distribution of the number of packets per message. In this paper we describe a queueing model which accounts for the non-Poissonian nature of the packet arrival process as a function of these two factors. Since packets are of a fixed maximum length, the model assumes that the packet service time is constant, as opposed to the mathematically more tractable but less realistic assumption of exponentially-distributed service time.

This queueing model is then used to describe the network delay as affected by:

1. Message switching versus packet switching,

2. A priority discipline in the queues,

3. Packet interarrival time per message, which is probably controlled by the line speed at the packet origination point, and

4. A network which carries only short inquiry-response traffic as opposed to a network which also carries longer low-priority printer traffic.

The general conclusions are that the peakedness in the arrival process caused by a short interarrival time of packets per message and the longer printer traffic would cause excessive delays in a network. If inquiry-response traffic with a short response-time requirement is also to be carried on the same network a priority discipline has considerable value. Message switching for such a combination of traffic should be avoided.
An analysis of link level protocols for error prone links
Authors: Miller Leslie Jill
Published: October 2004

This paper analyzes the maximum throughput across a full duplex link, under three link level protocols. The three protocols all assume cumulative acknowledgements, but the sender's retransmission policy and the destination's policy on retaining correctly received packets which arrive before an expected retransmission do differ. The results quantify the throughput advantages in retaining all correctly received packets, for the two different retransmission policies. A retention policy on the part of the destination is most advantageous when the link is quite error-prone.
Demand assigned multiple access systems using collision type request channels
Authors: Choudhury Gagan L. , Rappaport Stephen S.
Published: October 2004

Demand Assigned Multiple Access (DAMA) schemes in which requests for communication channels are transmitted over collision type channels to a master controller and in which messages of different priorities are present is analyzed. Priority use of the request channels is achieved by having users select among those channels according to a priority dependent probability distribution. Two important schemes of this class are considered. Additionally, three schemes for priority assignment of message channels are treated; two are non-preemptive and one is preemptive. Trade offs among bandwidth utilization and delay are considered as well as optimization of system parameters.
Bidirectional token flow system
Authors: Ulug M. E. , White G. M. , Adams W. J.
Published: October 2004

Over the last few years there has been an avalanche of technical literature on techniques for allowing nodes to access and share one of the most valuable resources of a computer communication network, i.e., the bandwidth of the communication media.
1
This report describes the design of a new type of Local Area Computer Network called BID that uses a bidirectional token flow as a form of token passing.
2
The design of BID not only allows it to process messages having various properties but also makes it possible to operate simultaneously in a packet and circuit-switching mode. This latter mode, using minipackets, enables BID to be used for those applications having real-time response requirements.

In describing BID this report defines the basic concepts of the implicit token, token carrier, token generator, and token wait time. It also describes a new preemption technique which reduces the walk time normally associated with token and polling systems.

A GPSS computer simulation was made of the BID system to determine the average delay times experienced by the various priority classes of messages. An analytical model using a single priority class of messages is presented, and the results of the computer simulation are compared with this. The simulation results also indicate the uniformity of the average delays experienced by the Bus Interface Units across the bus resulting from the use of bidirectional flow of tokens.
A theoretical performance analysis of polling and carrier sense collision detection communication systems
Authors: Arthurs E. , Stuck B. W.
Published: October 2004

A set of stations wish to transmit messages to one another over a shared link. Messages are generated either according to so called
finite source
or
infinite source
arrival statistics. The message lengths are independent identically distributed random variables. Two policies for arbitrating contention are compared:
polling,
and
carrier sense collision detection.
The maximum mean throughput rate and mean message delay is calculated as a function of model parameters.
A virtual circuit switch as the basis for distributed systems
Authors: Luderer G. W.R. , Che H. , Marshall W. T.
Published: October 2004

A communication system is presented which consists of a switch (Datakit [Fraser 1979]) with associated control and interface hardware and software. The switch offers virtual circuit service which is internally implemented through packet switching. The users of the communication system are operating systems; using our communication system, we have implemented a network of UNIX
TM
systems and a new distributed operating system derived from UNIX. Our work concentrated on the performance of the subscriber-switch interface; on the reliability and recoverability of the switching service; and on the exploitation of the circuit concept for operating system design.
X.75 internetworking of Datapac and Telenet
Authors: Unsoy Mehmet S. , Shanahan Theresa A.
Published: October 2004

In 1980, agreement was reached by CCITT defining a standard for the interconnection of public data networks. As a result, networks have been able to proceed with the establishment of international services using CCITT Recommendation X.75. This paper discusses the methodology used and the operating experience gained by the introduction of an X.75 interface between the GTE Telenet and Datapac public packet switching networks.
Impact of satellite technology on transport flow control
Authors: Tenney Richard L. , Falk Gilbert , Hunt Douglas H.
Published: October 2004

We present a framework for considering the impact of satellite communications on high level computer communication protocols. Within that framework, we present a model for analyzing these effects, and using that model, we derive some bounds on the amount of data that may be transferred over a communication channel which contains a satellite link. As our example, we use the flow control mechanism of an early version of a planned NBS transport protocol.
An experiment on high speed file transfer using satellite links
Authors: Huitema C. , Valet I.
Published: October 2004

One of the first applications of satellite telecommunication systems being studied within the NADIR pilot project is high speed (several Mbits/s) file transfer. After a short description of the French “TELECOM 1” satellite communication system, the paper points out that usual protocols such as HDLC cannot be simply adapted to fit satellite transmission requirements (high bandwidth, long propagation delay and various error rates). Specific problems, such as choice of frame length, error correction procedure, numbering scheme, and flow control mechanism are discussed, and a set of feasible solutions to be experimented are proposed.
Connectionless data transmission
Authors: Chapin A. Lyman
Published: October 2004

The increasingly familiar and ubiquitous Reference Model of Open Systems Interconnection, currently being considered by the International Organization for Standardization (ISO) as a Draft International Standard (DIS), is based on the explicit assumption that a "connection" -- an association between two or more communication entities, possessing certain characteristics over and above those possessed by the entities themselves - is required for the transfer of data in an Open Systems Interconnection (OSI) environment. Although the connection-oriented model of communications behavior has proven to be an extremely powerful concept, and has been applied successfully to the design and implementation of protocols and systems covering a wide range of applications, a growing body of research and experience suggests that a complementary concept - connectionless data transmission - is an essential part of the Open Systems Interconnection architecture, and should be embraced as such by the OSI Reference Model. This paper explores the concept of connectionless data transmission and its relationship to the more familiar concepts of connection-oriented data transfer, developing a rationale for the inclusion of the connectionless concept in the Reference Model as an integral part of the standard description of the OSI architecture.
A collision resolution algorithm for random-access channels with echo
Authors: Borgonovo F. , Fratta L.
Published: October 2004

In this paper random access algorithms for packet broadcast channels are considered. It is shown that utilizing channels with a central repeater as for instance a satellite channel more information is available to resolve conflicts than that utilized in Capetanakis type tree algorithms. Based on this extra information, a new class of collision resolution algorithms is presented. Only preliminary results on maximum achievable trhoughput are given and it is shown that this can approach. 673.