bluuebunny/crossref_metadata_2025 huggingface dataset:
On naming considerations for networks
Authors: Madan M. S.
Published: October 2004

The basic step involved in communication across a network and inter-network is the identification and validation of entities. Normally the identification of the entity in a network takes the form of a name or an address. The naming convention and its validation can affect both the user of the system as well as the system design and communication performance. On the user side, the naming scheme can be ad hoc, difficult to understand and non-user-friendly and can lead to inefficient addressing. On the system side, the name validation may require the global information of the entity names in the network and can impose certain restrictions on the dynamic topology reconfiguration of the network. Hence the naming convention is an important issue for the network architecture and possibly for standardization. This paper examines the semantics of name with respect to the communication and users point of view. The naming convention proposed by IFIP working group 6.5 is reviewed with respect to the naming requirements on public networks.
Standards for the evolving ISDNs progress and challenges a road map
Authors: Whittle Bryan S.
Published: October 2004

Pushed by advances in telecommunications technology and pulled by increased diversification in end user requirements, the need has been created for a uniform customer access and network structure in the public communications network environment. Driven by these trends and accelerated by national and international standardization, Integrated Services Digital Networks (ISDNs) are evolving to provide such a structure.The scope of this paper is to (1) present a brief account of the driving forces for ISDNs, (2) identify the major standards forums and sources of standards information and (3) present a brief account of some key ISDN characteristics, their associated standards and some of the current standards work items and trends. While private ISDNs
are
being contemplated, this paper considers ISDNs from a public network point of view and, in particular, a North American point of view. The purpose of this paper is to provide a skeletal primer on ISDNs and their standards on to which flesh and blood can be added as acquired by the reader.
Computer networks in Japan
Authors: Teshigawara Yoshimi
Published: October 2004

This report is an introduction to computer network systems which are currently being planned or implemented in Japan. Stimulated by the ARPA Network, computer communication networks are becoming more popular and as a result, many network systems are being studied and will be established. Some of the typical systems are introduced and explained in this report with special reference to system configurations, communications and network usages.
Message link protocol (MLP)
Authors: Bochmann G. V. , Vogt F. H.
Published: October 2004

This document is a specification of the Message Link Protocol (MLP). The MLP creates a transport service between session control entities via transport connections, and some additional session control service. It is based on virtual circuits a la X.25. It is concerned with transport connection establishment and termination, and handles resets and clears to provide a reliable transport service. Furthermore it provides synchronization support related to session establishment, termination and negotiation. The allocation of transmission resources to connections is also considered. It is assumed that the flow control capabilities of the X.25 virtual circuits can be used for transport connection flow control. If, for other transmission media, flow control may not be assumed, an additional function to provide flow control at the transport service level has to be introduced.
Remarks on negotiation mechanism and attention handling
Authors: Bauwens E. , Magnee F.
Published: October 2004

Preliminary studies are at present being made for building a computer network linking the computer centres of the different Belgian Universities. This network would include:1. a packet switching network with the X25 service on top of it;2. a transport protocol;3. user level protocols (a virtual terminal protocol and a file transfer protocol).Cooperation between terminals and applications will be organized using a virtual terminal approach.Assuming a transport function offering:1. block transmission with error control on contents, error control on arrival and sequencing;2. telegram transmission with error control on contents and error control on arrival,we present the attention handling scheme proposed for the Virtual Terminal Protocol of the Belgian University Network.The proposed scheme includes a renegotiation of the data flow mode (free running or alternate).A detailed algorithmic description of the proposed attention handling scheme is given using a state diagram representation.
From the chair
Authors: Sipior Janice C. , Schatzberg Laurie , Leidner Dorothy , Lending Diane , Vowels Susan
Published: October 2004

Welcome to the new academic year! I hope you had an enjoyable summer.The transition to our newly appointed Information Director, Susan Vowels, Washington College, has been completed. Susan replaces Diane Lending, James Madison University, who has graciously agreed to serve as the next CPR (Computer Personnel Research) Committee Chair. We again thank Diane for her superior service as Information Director and her continued service as CPR Committee Chair. Fred Niederman, Saint Louis University, was presented with a plaque for his outstanding contributions as the first CPR Committee Chair at the ACM-SIGMIS CPR (Computer Personnel Research) 2004 Conference held in April in Phoenix, Arizona USAConsider sending a submission to the

SIGMIS Computer Personnel Research 2005 Conference:

Where:
Atlanta, Georgia USA

When:
April 14-16, 2005

Theme:
"Beyond the Bust: Preparing for the Boom?"

The submission deadline is October 15, 2004. Your participation is welcome! For more information, please contact the SIGMIS CPR Conference Committee:

Conference Chair:
Mike Gallivan, Georgia State University, mgalliva@gsu.edu

Program Co-Chairs:
Jo Ellen Moore, Southern Illinois University Edwardsville, joemoor@siue.edu Susan E. Yager, Southern Illinois University Edwardsville, syager@siue.edu

Local Arrangements:
Ephraim McLean, Georgia State University, emclean@gsu.edu

Treasurer:
Laurie Schatzberg, University of New Mexico, laurie@mgt.unm.edu

Publicity:
Manju Ahuja, Indiana University Bloomington, mahuja@indiana.edu Or, check our website at: http://www.acm.org/sigmis

Also, I would like you to consider hosting a future SIGMIS CPR Conference. Let's make the SIGMIS CPR Conference a continuing success!Finally, please mark your calendar now for the

Fourth Annual ACM-SIGMIS Reception:

Where:
International Conference on Information Systems (ICIS2004) Washington, D.C. USA

When:
6:00 to 8:00 pm (to be confirmed) Saturday, December 11, 2004

Who:
All ACM-SIGMIS members and their invited guests are welcome!

We encourage any comments or suggestions. Please feel free to contact any one of us. Thank you for your interest in and continued support of SIGMIS.
The evolution of IT (computer) personnel research
Authors: Niederman Fred , Mandviwalla Munir
Published: October 2004

Scholars have been publishing research on IT work and workers since at least 1965. The work is a testimony to the longevity and importance of topics concerning computer personnel, human resource management, and the information technology workforce. Human resources have consistently been noted as a top concern of MIS leaders through a series of "key issues" studies (Brancheau et al., 1996; Niederman et al., 1991; Brancheau & Wetherbe, 1987; Dickson & Wetherbe, 1984; and Ball & Harris, 1982). The research also shows that along with the evolution of information technology there is a parallel evolution of skills and capabilities; that allows IT specialists to continue designing and implementing new technologies, which enable users to introduce them into business, science, and other environments to create value. A review of the original proceedings of the special interest group on computer personnel research from 1965, shows that the field has also progressed substantially.Almost four decades ago, scholars began by producing very basic descriptive research on job analysis and job description, how to train personnel, assessment techniques, and the effects of attitudes on learning. As the old saying goes, the more things change the more they stay the same. A look at the state of IT personnel in the early part of the 21st century shows that we continue to research similar problems such as periods of high demand for IT workers punctuated with periods of slowdown (remember the doldrums of the early 1990s?), investigate approaches and techniques for increasing IT worker productivity (remember the introductions of COBOL, CASE tools, and more recently extreme programming?), and struggle with issues of diversity in the IT workplace. Even the issue of outsourcing is not new. One of the authors recalls serving as discussant in 1992 on a computer personnel research conference paper challenging IT workers to increase productivity or face the prospect of having their job outsourced!Although some of the major issues of the day seem to recur at regular intervals, others seem new or at least manifested in a new way. We believe that scholars are facing significant challenges in addressing at least four major issues that confront IT personnel:
Communicating with decision tables, flowcharts, and prose
Authors: Willoughby T. C. , Arnold A. D.
Published: October 2004

Prose, flowcharts, and decision tables are three techniques which can be used to describe process flows. Since they can be used to communicate actions and alternatives to people, one should be able to measure their effectiveness as communication aids. This study compared the ability of unsophisticated users to solve simple problems stated in each of the three forms.
IRIS
Authors: Berger Paul , Edelman Franz
Published: October 2004

Regulatory and internal requirements are creating strong and growing pressures for more effective means of managing human resources. This calls for systems support more capable than is available through traditional MIS methods. There is a crucial need to extend the customary MIS role, beyond providing regular functions and procedures to assure timeliness and integrity of raw data, to be capable of becoming an integral part of the management process itself through ad hoc inquiry and analysis. This must be a facility which is put at the direct and personal disposal of the manager. The degree to which such an information technology genuinely assists a decision maker in pursuing a train of thought is the most relevant and, in the final analysis, perhaps the only true measure of its effectiveness.Currently available data base designs, high-level analysis and inquiry languages and interactive computing have been combined into a systems architecture which makes such decision support systems a practical reality. This paper describes one such system. It is in regular daily use ina highly diverse industrial enterprise as a transaction driven data system, but is designed for the noncomputeroriented manager in a problem-solving situation as the intended ultimate end user.
Training users of a prototype DSS
Authors: Grace Barbara F.
Published: October 2004

The ITM (interactive training manual) is a mechanized training package which allows users to learn a prototype decision support system while interacting with an actual grapics system and data base. Decision support systems, which offer powerful, computer-based functions to professional nonprogrammers, place heavy demands upon training because users tend to have severe time constraints and a low tolerance for training. This paper describes the ITM and gives results of an experiment which compares the ITM to human tutors. Results show that the ITM decreases instructor time while maintaining or improving student performance. These results are quite encouraging since good human tutors are generally considered to provide the most effective individualized instruction.
A DSS for diagnosis and therapy
Authors: Davis Randall
Published: October 2004

This paper reviews an approach to the design and construction of a decision support system intended to function as a consultant on the question of diagnosis and therapy selection. It describes the system in terms of the nature of the decision problem involved, discusses factors which make the problem difficult and considers the design goals that have led to the construction of a system with several novel capabilities. Many of those capabilities result from representing domain-specific knowledge in the system in terms of numerous judgmental decision rules, and we examine a number of such rules. Examples of the system in operation are given to illustrate many of these issues, and performance is compared with previous approaches to automated medical decision making. Finally, we consider the domain independence and generality of the methodology and consider the potential impact the system may have as a tool for decision support.
GPLAN
Authors: Haseman William D.
Published: October 2004

The GPLAN system, an operational decision support system, is presented with a discussion of both the design and implementation details. The system allows a decision maker to ask ad hoc questions in a nonprocedural English-like query language. The questions can include both data fetching as well as data analysis, using generalized models stored within the system. The kinds of data analysis performed by the system are limited only by the set of models contained in the library.
Common data base languages
Authors: Nijssen G. M.
Published: October 2004

The concept data base is described to serve as a basis to derive data base management system requirements. The main aspects of CODASYL's common data base management languages, DDL and DML will be explained without going to details. The influence of DDL and DML on application programs will be analyzed.
Data management for decision support systems
Authors: Methlie Leif B.
Published: October 2004

In describing a DSS architecture it is common to include a database as a component in the system. However, the DSS literature pays little attention to the data management function. Emphasis is placed on model aspects and user-system interface. In this paper we shall develop some characteristics of the data management function for a DSS. They are based on data management functions in some existing management tools as well as general developments within database theory. Finally, a particular feature of data management, data extraction, is treated. Data extraction enables loading of data into a DSS from data files external to the DSS.
Measurement as an MIS foundation
Authors: Mason Richard O. , Swanson E. Burton
Published: October 2004

Seven aspects of measurement are of particular importance in terms of MIS foundations: (1) scientific and technical characteristics, (2) basic design choices, (3) level of information and decision support, (4) managerial functions supported, (5) organizational focus, (6) information system component origin, and (7) behavioral dimensions. A brief summary of these aspects is presented, and it is argued that measurement deserves recognition as one of the most important foundations of MIS.
Decision-making theory and DSS design
Authors: Bahl Harish C. , Hunt Raymond G.
Published: October 2004

A sampling of decisions of practicing managers represented by evening MBA students is reviewed to explore the applicability and the completeness of existing theories of decision-making. In response to a review of difficulties illustrated by the study, a utilitarian and descriptive model of decision-making is described. We further discuss the role of this model in the analysis and design of decision support systems (DSS).
GDOC
Authors: Ferrara Fabrizio Massimo , Batini Carlo
Published: October 2004

Release 2.1 of GDOC, a tool for computer-aided design of database applications, is described.GDOC provides for the interactive specification of the conceptual schema of the application, expressed in an enriched Entity-Relationship Model and produces the relevant documentation by means of traditional printouts, as well as allowing a graphical definition of the conceptual schema. Moreover, GDOC automatically generates the physical database and the operating programs for accessing the concepts in the schema in a dBASE II environment.Experiences of use of GDOC are discussed and further research directions are outlined.
Phased design
Authors: Dennis A. R. , Burns R. N. , Gallupe R. B.
Published: October 2004

The evolution of information technology from batch processing to on-line, database-oriented systems has spawned the use of new system development methodologies better suited to the needs of complex information systems. The increased demand for large, unstructured decision support systems (DSS) and complicated transaction processing systems has provided the impetus for the development of prototyping and "mixed" methodologies - techniques that combine prototyping with the standard systems development life cycle. The present "mixed" approaches place increased emphasis on one of these two basic methodolgies over the other. This paper contrasts the current techniques and presents a new mixed methodology that integrates prototyping and the system development life cycle into a more balanced approach that has been successfully used in the development of several application systems.
Management audit of information systems
Authors: Hoffman Alexander A. J.
Published: October 2004

Periodic review of the information systems function is necessary to determine if costs are in line with services provided, if the users are satisfied with services, and if computer power is effectively used to meet the demands of management. The purpose of this paper is to propose and introduce a new concept: Management Audit of Information Systems. An audit is defined as an "official" examination or review implying reference to some standard such as Generally Accepted Practice (GAP) as is used by accountants. Since there are no proposed or official standards in information processing, the term review is used instead of audit. As a result, conclusions reached in a review tend to be subjective and reflect the emphasis of the reviewer. A methodology is proposed for performing a standardized review (e.g., audit) of Information Systems with a view toward development of Information Systems Standards which could be adopted and promulgated by an appropriate professional organization. A Management Audit of Information Systems could then be conducted by qualified individuals to determine the extent of compliance with Generally Accepted Practice.
Measurement of computer system/information system performance
Authors: Hoplin Herman P. , Suresh B. A.
Published: October 2004

This paper reports the results of a field study conducted to obtain managers perceptions of their Management Information Systems (MIS). The basic study involved responses from over 100 MIS/DP managers, users, and other business professionals. The research sampled the perspectives of both MIS and non-MIS personnel and found no great disparities in either the favorable quality of services provided or in the ranking of tasks contributing to system productivity.
Protected records, time management and distribution
Authors: Baker Ted
Published: October 2004

This is a summary of the discussions on three requirement areas:

Protected Records;

Time Management;

Distribution.
Asynchronous and stand-alone entries
Authors: Powers Richard
Published: October 2004

This report summarizes the discussions held on asynchronous and stand-alone entries.
Asynchronous transfer of control in Ada 9X
Authors: Burns A. , Wellings A. J. , Davies G. L.
Published: October 2004

The Taft proposal is described in detail. It involves introducing a new "and" clause into the select statement thereby providing a means of programming asynchronous transfer of control without the use of the abort facility. An evaluation of the proposal considers some of its limitations, the major one of which is the possibility of deadlock if a group of tasks use the facility to affect each other. Ways of removing this difficulty are considered. The model is then compared with the alternative of introducing asynchronous exceptions. Finally a unified model is presented that combines the advantages of the Taft proposal and asynchronous exceptions.
Prioritized asynchronism in Ada 9X
Authors: Elsom K. C.
Published: October 2004

This paper discusses the semantics for asynchronous message passing between prioritized tasks including the case where the messages may themselves be given explicit priority. A highly flexible scheme results that is applicable to a wide range of scheduling algorithms. The impact in the case of a simple priority-inheritance scheduler is explored.
Predictable real-time avionics design using Ada tasks and Rendezvous study
Authors: Locke C. D. , Vogel D. R. , Mesler T. J.
Published: October 2004

As a part of the Software Engineering Institute's Real-Time Software in Ada project, personnel from IBM, the Naval Weapons Center, and SEI carried out an effort to construct a realistic hard real-time avionics application using Ada, including Ada tasking and rendezvous. In this joint study, an important goal was to determine how to use the Ada language
as it was designed to be used
in a hard real-time system, rather than continuing the current practice of avoiding the very constructs Ada's designers created to meet real-time requirements. In this paper, we present the avionics problem considered, as well as a high-level overview of an Ada solution to the problem which uses Ada tasking and rendezvous, resulting in a solution fully capable of predictably meeting its time constraints.
CCITT recommendation X.25 as part of the ISO reference model of open systems interconnection
Authors: Jacobsen Tom , Thisted Peder
Published: October 2004

The CCITT Recommendation X.25 is discussed in view of the ISO Reference Model of Open Systems Interconnection. It is stated, that X.25 may serve as an access method of layer 3, 4 as well as 5, depending of the actual architecture. The flow-control principles of X.25 are discussed and a clarification is recommended.
Proposal for a connection-oriented internetwork protocol
Authors: Callon Ross
Published: October 2004

Current OSI approaches to internetworking occur at the network layer, and can be split into two main divisions [1,2]: connectionless internetwork protocol intended for use over dissimilar networks, and relay approaches intended for interconnection of networks offering identical, reliable, connection-oriented service.

This article briefly introduces these two approaches and discusses the need for a somewhat different approach: a connection-oriented internetwork protocol. I discuss the reasons for defining such a protocol, and considering these reasons, I propose a general design. I conclude that the present connectionless internetwork protocol should be augmented by a complementary connection-oriented protocol of a much simpler design than traditional connection-oriented protocols.
Selection of a local area network for the Cronus distributed operating system
Authors: Pogran Kenneth T.
Published: October 2004

The Cronus Distributed Operating System, under development at Bolt Beranek and Newman Inc., employs high-bandwidth local area network technology to interconnect processing elements that are members of a Cronus "cluster." One requirement imposed upon the Cronus development was that the system employ "commercial, off-the-shelf" local area network technology. This paper describes the requirements we established for the Cronus local area network and the selection process we employed, and gives our reasons for choosing ETHERNET technology.
Steady-state analysis of a slotted and controlled Aloha system with blocking
Authors: Metcalfe Bob
Published: October 2004

We assume the reader is somewhat familiar with the ongoing
development of Aloha techniques as described briefly in Abramson's
FJCC 7 0 paper and Roberts's SJCC72 paper. In short, an Aloha
system permits the (hopefully) occasional interference of data
packet transmissions in a multi-access channel and provides for the
retransmission of lost packets after some randomly distributed
interval. The purposes behind permitting interference and providing
recovery are (1) reduced central communication control to improve
reliability and (2) improved use of communication facilites under
bursty loads as found in interactive computer communication. Aloha
techniques are finding applicability in various communication
contexts (e.g., satellites), but here the emphasis is on
large
populations of (potentially mobile)
interactive
terminals.

Slotted
. In a
slotted
Aloha system, all terminals
begin their packet (re)transmissions at the ' tick of some global
clock. Slotting has been advocated by Roberts as a simple way to
improve the limiting thruput of an Aloha channel by a factor of 2.
Global ticking can be implemented in a (hopefully positive) number
of ways and its feasibility is assumed in this paper. We rely on
slotting to simplify our analysis, but suggest that the stability
and control phenomena studied are characteristic of Aloha systems
in general.

Controlled
. The notion of an optimal retransmission delay
was introduced by Roberts. We extend the notion to include dynamic
control of retransmission delay. A
controlled
Aloha system
has the property that its terminals adjust their retransmission
behavior as a function of perceived channel utilization. It will be
shown that such adjustments are implementable in at least one way
and that they improve system performance under heavy loads.

Blocking and Thinking
. When a user's terminal has a ready
packet, it is assumed that no new packets can be generated. The
user is said to be
blocked
. When a user is not blocked, he
is said to be
thinking
. This assumption about user behavior
departs from Abramson 's analysis and is thought to produce more
realistic solutions. Recall that Abramson (in FJCC70) modelled
users as unperturbable, realtime, Poisson sources of new packets.
By adding blocking to an Aloha model, transmission delays feed back
(as in real life) on the generation of transmission requests. User
sessions are said to be
dilated
by transmissions delays.

It is intended that
think
time account for (1) delays in
central system response, (2) return transmission delays, (3) real
user thinking time, and (4) type-in time.
Block
time
accounts only for delays due to transmissions through the
multi-access channel.

The following analysis rests on some (very) simplifying
assumptions about an Aloha system in equilibrium, in steady state.
While having a large population of users tends to support our
steady-state arguments, the dynamics do indeed require more
detailed investigation.
Political and economic issues for internetwork connections
Authors: Kuo F. F.
Published: October 2004

In this paper we will attempt to outline some of the political and economic issues which must be addressed before meaningful network interconnections can come about. The issues we discuss are: Bilateral versus Multilateral Agreements, Standards, The Viewpoint of the Common Carriers, Network Accounting, Tariffs and Excises, Privacy and Security. Our main purpose is to present the problems and issues but not to offer any solutions.
Source routing in computer networks
Authors: Sunshine Carl A.
Published: October 2004

As plans for network interconnection develop, the problems of internet routing and addressing become increasingly important. In one popular model of internet addressing, a hierarchical form of network and local (within network) address is used, with the source providing only the destination address while the intermediate network(s) and/or Gateways between networks take care of routing packets to that destination by various paths. This and related techniques requiring some form of routing table and knowledge at intermediate nodes are more fully discussed in [1,2,3].

This paper considers another technique for internet routing in which the source of internet packets specifies the complete internet route. When the entire route accompanies each internet packet, no routing decisions or tables are required at Gateways, but the packet format is complicated and overhead increases. In particular, the packet must carry a varying number of intermediate addresses depending on the path and destination [4]. This overhead may be reduced by setting up a fixed route with connection tables [1] when a connection is established.
Proposal for a scroll mode virtual terminal
Authors: Schicker P. , Zimmermann H.
Published: October 2004

The scope of this document is to present the concepts of a Virtual Terminal and to define in detail that portion of the Virtual Terminal Protocol which is adequate to support a basic Scroll Mode Virtual Terminal.
Symmetry and attention handling
Authors: Dünki A. , Schicker P.
Published: October 2004

Synchronization, attentions, and negotiation are basic elements of most protocols. We can develop these concepts and techniques within the framework of the terminal-application model. This does not mean that we should import the asymmetry of this model into the protocol where it is not necessary, and where it precludes the use of this protocol in more general situations.
A virtual terminal protocol based on the use of zones
Authors: Barber D. L. A.
Published: October 2004

Companion papers have considered the concept of the Virtual Terminal in the context of a network (ref 1) and as an interface between users and computers (ref 2). These papers give a background for the present paper which proposes a Virtual Terminal protocol for use between an applications program and a remote terminal handler, based on the concept of the dynamic assignment of zones, introduced by Luca (ref 3).

The paper by Luca contains an excellent discussion of the concept and use of zones, which seem well suited for a Virtual Terminal protocol although this was not considered in his paper. Some simplification of Luca's work is appropriate because he is concerned both with the interface between an application and the terminal handler, which he calls the programmable communications controller (PCC), and with the mapping between the PCC and a real terminal. The first aspect only will be considered here as the basis of a simple applications level protocol for a Virtual Terminal. However, Luca's paper is also a useful guide for the designers of the terminal handler and users who are concerned with mapping the Virtual Terminal onto particular real terminals.

This paper draws on the ideas contained in the earlier papers reviewed in Appendix 1 of ref 2, and uses the notation introduced in Appendix 2 of ref 2. The zones concept is similar to the idea of the Communication Unit introduced by Schulze (ref 4) and this has also influenced the proposals set out below.
An RJE protocol for a resource sharing network
Authors: Day John , Grossman Gary R.
Published: October 2004

For many users of networks like the ARPANET, an RJE protocol is probably as important in terms of utility as the TELNET (or Virtual Terminal) protocol. In fact, the facilities provided by a TELNET and an RJE protocol are probably of most interest to the majority of users of computer networks. For these users, the network provides a fast, cheap telephone surrogate to a variety of computers for RJE and terminal access. The collection (and layers) of protocols that are used to provide these services must be organized to efficiently support a wide variety of applications and user needs. They should not pose an undue software burden on the user.

The "official" NETRJE protocol for the ARPANET is built on top of the Telnet and File Transfer Protocols (FTP). A user of NETRJE establishes a Telnet connection using the User NETRJE program on his local host to a Server NETRJE process at the host where he wishes to submit a job (see Figure 1). The user then sends to the Server process appropriate commands to log in, to describe where the job is that is to be submitted, to describe how the job is to be transferred, and to describe what is co be done with output when the job is completed. The Server NETRJE process on the foreign host then uses the FTP to transfer the input file to the foreign host, and then may use FTP again later to send the output back to the user. This protocol is very general and allows a user to submit his input from one host, process it at a second, and send the output to a third.
X.25 link access procedure
Authors: Cosell Bernard , Nemeth Alan , Walden David
Published: October 2004

We prepared this description of the X.25 link access protocol for a commercial packet-switching network installation in which we participated. Our goal was to provide the network's users with a version of the link access procedures specification which was easier to read and understand than the X.25 specification documents available at the time. No attempt was made to change or improve the X.25 link access procedure; we merely attempted to write the procedure down more clearly.

We have written the description in terms of "Nodes" and "Hosts", terms which are in common use in the packet-switching network field. Others desiring to adopt this description may decide to use the CCITT terms "DCE" and "DTE", or still other terms, for the same functional entities.

The X.25 specification of its link access procedure includes a detailed description of the mechanisms used to provide bit error detection and data transparency on the link, i.e., a specific 16-bit checksum and a method of inserting and later deleting additional 1-bits which provides the equivalent of the BSC escape character mechanism. We do not view the detailed specification of these aspects of the (presumably hardware) interface as fundamental to the X.25 link access procedure. Both the error control and transparency functions must be provided, but it is easiest to use whichever specific mechanisms are provided in the communications interface line of the vendor of the Host computer rather than requiring the X.25 specification to be used.

We were aided in learning the X.25 link access procedure by Marie Rousseau. Our colleague, Alex McKenzie, provided important editorial assistance and guidance regarding the presentation of this description, and by rights he should be considered a co-author.
A problem with the X.25 link access procedure
Authors: Gostl Jack
Published: October 2004

In the first half of 1977 I was involved in the design and implementation of a network control program (NCP) which interfaced a PDP-11/70 Host computer to a packet switching network (similar to ARPANET (1)). The NCP was responsible for both Host to Host message control and Host to network link control. The Host to network interface used a subset of X.25 (2) for its Link Access Pro cedure (LAP).

During the development and debugging of the NCP, it was discovered that the Host-network link could get into a deadlock condition which could not be rectified by any mechanism specified in the current X.25 protocol. The LAP, the problem and several possible solutions are described.
Some problems with the X.25 packet level protocol
Authors: Belsnes Dag , Lynning Ejvind
Published: October 2004

During the last year recommendation X.25 [1] of the CCITT specifying a packet mode interface between a DTE and a DCE has been the subject of study and discussion. X.25 defines a link access and a packet level protocol the latter of which is of interest here. According to X.25 a number of logical connections, called virtual calls, may share one physical link between DTE and DCE. The sharing is achieved by asynchronous time-division multiplexing of so-called logical channels. For each channel, call setup and clearing, data transfer, and flow control takes place by the exchange of packets. There are different types of packets for the different tasks mentioned. A scheme involving a number of states for logical channels is used in the protocol.

In this paper we discuss two aspects of the packet level protocol which we feel are insufficiently or erroneously specified in X.25. First, the insufficient description of the DTE-to-DTE packet level protocol which X.25 implies. Second, some problems relating to the states and state transitions for logical channels as specified by X.25. These problems we consider to be the result of erroneous design, and repair is suggested.
A file transfer protocol and implementation
Authors: Butscher B. , Heinze W.
Published: October 2004

This paper presents a file transfer service in a heterogeneous computer network (HMINET). The basic architecture models are presented, the file transfer protocol is described and the implementation in the HMINET is shown with the functional capabilities and the command structure.

A transfer of files between different computer system can be regarded as a service, which is divided into four steps:

A: access to a file, which is administrated in a File Management System (FMS), residing on one computer system

B: transfer the file data by any transport medium

C: creation of a file copy in another EMS

D: additional operations on the transferred file, e.g. print out or conversion

The usual case of file transfer (FT) between different computer systems is an offline transport by means of any storage medium (disks, tapes, etc.). Some disadvantages arise by this method:

- offline transfer takes a long time

- incompatibility of peripheral devices, storage medium and dat a representation can make file transfer impossible or lead to an additional overhead

- for step A and C the user must be familiar with the control languages of every participated operating and file management system

- additional operations on the transferred file must be organised under the system control of the destination host

A lot of advantages offers a File Transfer Service, integrated in a network, which links together the above mentioned computer systems (hosts):

- with a reliable transport system in the network a fast online transfer of the file data can satisfy step B

- step A and C are controlled by the File Transfer Service with only one standard interface to the user

- additional operations on the copied file can he managed during the transfer of the data (conversion of file structure, file dat a and subsequent operations e.g. print)

- peripheral device support by involved operating and file management system under File Transfer Service control

The HMINET is a private star-shaped, heterogeneous network, which connects 22 process control computers and 3 mainframes. One basic function in that computer network is such a file transfer service. Typical applications of this service are:

Copy of data files from and to mainframes and process control computers

Transfer of programms and runable modules

Remote Job Entry and remote spool services, etc.
Encoding CCITT X.409 presentation transfer syntax
Authors: Pope Arthur R.
Published: October 2004

CCITT Draft Recommendation X.409 [1] defines a manner of encoding information for communication among computer systems. This scheme includes not only an encoding syntax--rules by which communicated bits and octets are assigned meaning--but also a language for describing the form and content of communicated information in a human-readable notation. In this notation one may define the form of a protocol data unit (PDU), specifying how the PDU is composed of individual fields of integer values, bit flags, characters, etc. One may also use the notation to define specific instances of PDUs: a PDU containing the integer value 3, the bit flag "on" and the character "A", for example. From the notational description of the PDU one may directly infer its encoded representation by applying the rules of the encoding syntax.

As a language for documenting the encoding of standard protocols, the notation is intended primarily for human consumption. Being a formal language, however, it is also well suited to automated processing. This paper describes some software tools developed at BBN for processing the notation. The principle purpose of the tools is to permit rapid construction of PDU encoding and decoding software from notational descriptions of PDUs.

The next section of this paper contains a brief overview of the X.409 notation and syntax for those not already familiar with the Draft Recommendation. The following section describes the tools and their method of operation. Some notes about the implementation and its performance complete the paper.
ALOHA packet system with and without slots and capture
Authors: Roberts Lawrence G.
Published: October 2004

This paper was originally distributed informally as ARPA Satellite System Note 8 on June 26, 1972. The paper is an important one and since its initial limited distribution, the paper has been frequently referenced in the open literature, but the paper itself has been unavailable in the open literature. Publication here is meant to correct the previous gap in the literature.

As the paper was originally distributed only to other researchers intimately familiar with the area covered by the paper, the paper makes few concessions to the reader along the lines of introductory or tutorial material. Therefore, a bit of background material follows.

ALOHA packet systems were originally described by Abramson ("The ALOHA System--Another Alternative for Computer Communication," Proceedings of the AFIPS Fall Joint Computer Conference, Vol. 37, 1970, pp. 281--285). In an ALOHA a single broadcast channel is shared by a number of communicating devices. In the version originally described by Abramson, every device transmits its packets independent of any other device or any specific time. That is, the device transmits the whole packet at a random point in time; the device then times out for receiving an acknowledgment. If an acknowledgment is not received, it is assumed that a collision occured with a packet transmitted by some other device and the packet is retransmitted after a random additional waiting time (to avoid repeated collisions). Under a certain set of assumptions, Abramson showed that the effective capacity of such a channel is 1/(2e).

Roberts in the present paper investigates methods of increasing the effective channel capacity of such a channel. One method he proposes to gain in capacity is to consider the channel to be slotted into segments of time whose duration is equal to the packet transmission time, and to require the devices to begin a packet transmission at the beginning of a time slot. Another method Roberts proposes to gain in capacity is to take advantage of the fact that even though packets from two devices collide in the channel (i.e., they are transmitted so they pass through the channel at overlapping times), it may be possible for the receiver(s) to "capture" the signal of one of the transmitters, and thus correctly receive one of the conflicting packets, if one of the transmitters has a sufficiently greater signal than the other. Roberts considers the cases of both satellite and ground radio channels.
Unification of underlying concepts in different office models
Authors: Desai Sandhya M.
Published: October 2004

Several office models based on different perspectives of offices have been published in the literature. Most of the models emphasize a particular aspect of an office and consequently do not capture all the nuances of offices. We study eight representative office models with regards to their expressive power and underlying concepts.From the set of concepts embedded in these models we arrive at a minimal set of three concepts, namely,
office information, office work and office agents
. These are the essential aspects to be captured in a model reflecting all the complexities of offices. Based on this minimal set, three basic entities --
object, activity and role
-- are proposed. An outline of an office model in terms of its basic entities is presented. The existing models are analysed with reference to the characteristics of the basic entities.
Extending the MERCURY system to support teams of Ada programmers
Authors: Micallef Josephine , Kaiser Gail E.
Published: October 2004

The M
ERCURY
system generates multi-user language-based environments from attribute grammars. The AG specifies the interface checking among modular units, to be applied by the environment to inform programmers of errors introduced by interface changes. Since AGs assume a monolithic program, we extended the formalism to support separate compilation units. Our previous work was based on an ideal language where programs consist of an unordered set of monolithic compilation units. We now augment our extensions to support Ada, to allow multiple kinds of compilation units and nested compilation units. We describe how these extensions are used to detect naming errors, determine compilation unit context, and check compilation order as mandated by Ada.
VADS APSE
Authors: Matthews Ed , Burns Greg
Published: October 2004

During the 1980's, the United States Department of Defense developed the Ada language to combat the growing "software crisis," while software companies developed Computer-Aided Software Engineering (CASE) tools to enhance software development productivity. Ada and CASE are beginning to merge, but the disjoined solutions offered by individual CASE vendors to this point are lacking in two key areas: (1) exploitation of program information available as a by-product of compiling an Ada program; and (2) integration of individual tools to produce synergistic benefits over a broader range of the software development cycle.To remedy these shortcomings, Verdix Corporation has begun development of an Integrated Ada Programming Support Environment, VADS APSE. VADS APSE represents a significant departure from previous APSE development efforts in that it is built on an environment framework from commercially available software and it exploits the capabilities of powerful, low-cost, networked engineering workstations. While VADS APSE represents an instance of an environment built upon a framework, it also represents, through extensions to the underlying framework, an Ada-specific environment framework that can be tailored to meet the needs of a specific software development activity.
High speed networking at Cray research
Authors: Nicholson Andy , Golio Joe , Borman David A. , Young Jeff , Roiger Wayne
Published: October 2004

For many years, ethernet has been the mainstay for TCP/IP and local area networking, and issues specific to wide area and long haul networks have not been adequately addressed. The advent of FDDI and HIPPI standards, which are, respectively, one and two orders of magnitude faster then Ethernet, and high speed cross country links, are causing what used to be experimental issues to become everyday problems. This paper will cover some of these issues, as they relate to the TCP/IP protocols, and the work that has happened at Cray Research in the development of the UNICOS† operating system to address these issues.
Scheduling and IPC mechanisms for continuous media
Authors: Govindan Ramesh , Anderson David P.
Published: October 2004

Next-generation workstations will have hardware support for digital "continuous media" (CM) such as audio and video. CM applications handle data at high rates, with strict timing requirements, and often in small "chunks". If such applications are to run efficiently and predictably as user-level programs, an operating system must provide scheduling and IPC mechanisms that reflect these needs. We propose two such mechanisms:
split-level CPU scheduling
of lightweight processes in multiple address spaces, and
memory-mapped streams
for data movement between address spaces. These techniques reduce the the number of user/kernel interactions (system calls, signals, and preemptions). Compared with existing mechanisms, they can reduce scheduling and I/O overhead by a factor of 4 to 6.