Showing papers on "Communications protocol published in 1976"

Recoverability of Communication Protocols--Implications of a Theoretical Study

Abstract: A study is presented which permits the formal analysis and synthesis of recoverable computer communication protocols. This study is based on a formal representation of processes by a model of computation, the Petri nets (PN's). The PN model is generalized to include a representation of the possible failures, and then, the concept of "recoverability" is formally defined. A set of necessary and sufficient conditions which a process must satisfy in order to be recoverable is derived. In the PN model, the processes that satisfy these conditions are shown to have some practical limitations. A new model, the time-Petri net (TPN), is introduced to remove these limitations. This new model allows the introduction of constraints in the execution times of its part. As shown in this paper, the TPN appears to be a suitable model for the study of practical recoverable processes. Several practical communication protocols are formally designed and analyzed using this new model, and some interesting properties of these protocols are formally derived.

A Methodology for the Design and Implementation of Communication Protocols

Abstract: This paper presents a coherent method which permits the specification, check out, and implementation of communication protocols. Although this work is mainly directed towards telephone signaling in a programmable environment, the philosophy and most of the tools can be effectively used to handle the most general situations in which two entities interact by any kind of protocol. Since the proposed approach reduces the possibility of errors and inconsistencies, minimizes the programming needed, and improves the documentation and understandability, we believe that this methodology will facilitate the installation or modification of complex trunk protocols and other communication protocols.

A high-level framework for network-based resource sharing

Abstract: This paper proposes a high-level, application-independent framework for the construction of distributed systems within a resource sharing computer network. The framework generalizes design techniques in use within the ARPA Computer Network. It eliminates the need for application-specific communication protocols and support software, thus easing the task of the applications programmer and so encouraging the sharing of resources. The framework consists of a network-wide protocol for invoking arbitrary named functions in a remote process, and machine-dependent system software that interfaces one applications program to another via the protocol. The protocol provides mechanisms for supplying arguments to remote functions and for retrieving their results; it also defines a small number of standard data types from which all arguments and results must be modeled. The paper further proposes that remote functions be thought of as remotely callable subroutines or procedures. This model would enable the framework to more gracefully extend the local programming environment to embrace modules on other machines.

A study of line overhead in the Arpanet

Abstract: The form, extent, and effect of the communication line overhead in the ARPANET are considered The source of this overhead is separated into various levels of protocol hierarchy and the characteristics of each level are summarized Then the line efficiency for various models of system use is studied Some measurements of line efficiency for the ARPANET are presented and by extrapolation these measurements are used to anticipate overhead in a heavily loaded network Similar results are derived for a recently proposed network protocol and compared with those for the current system

Data communication bus structure

Abstract: A data communication bus structure where all module-to-module control information is grouped into two sets of lines, defined as sub-buses, wherein signal contents of the sub-buses change only at well-defined times, under the control of two other lines which themselves simply govern the transfer of control information relative to the communication. The bus structure is symmetrical with one type of each line driven by each of the two modules involved in the communication. Arbitrary standard error detecting/correcting encodings may be used on the bus to overcome possible bus failures with no change to the basic bus communications protocol. An independent bus monitor observes all communications over the bus, observes when an improper signaling exchange takes place, and isolates the module most responsible for the fault. Also, there is provided a simple and standard programmable interface unit which can be used to generate the appropriate control information and signaling protocol for a module that is to be tied to the bus.

An algebraic system for process structuring and interprocess communication

Abstract: An extension of regular expressions is introduced to represent the activities of synchronizing concurrent processes. A communication link is defined as an automaton (infinite) with one-to-one partial transformations, and communication protocol as an assignment of events to actions of a communication link. A synchronization problem is defined as a problem of concurrent decomposition of a process into a deadlock-free family of processes sharing a communication protocol.It is shown that it is decidable whether a finite family of sequential processes, communicating through a finite link, is deadlock-free or not.

A new communication protocol for accessing data networks: the international packet-mode interface

Abstract: Public packet switching networks are at various stages of development around the world, notably in the U.S., Canada, France, the United Kingdom and Japan. The success of these networks is highly dependent on the use of an agreed-upon standard device-independent interface between the packet networks and the user devices operating in the packet-mode. This interface consists of far more than the data link control procedure (i.e., HDLC), which administers the physical transmission medium between the data terminal equipment (DTE) and the network. The specification of the packet-mode interface defines a set of conventions governing the manner in which DTEs establish, maintain and clear calls, format control information and data into packets and manage the flow of data for many calls over a single circuit to and from the packet network.This paper describes the International Packet-Mode Interface, developed jointly by Telenet Communications Corp., the Trans-Canada Telephone System (TCTS), the United Kingdom Post Office and the French PTT. This interface has been designed to enable DTEs such as computers, programmable terminal controllers and intelligent terminals to gain access to public packet networks throughout the world. The present status of international standardization of this interface within the CCITT is also covered.Standardization of the International Packet-Mode Interface is to the advantage of teleprocessing users, manufacturers of data processing and terminal equipment and common carriers.

Datapac Network Protocols.

Abstract: The Ministry of Health and Long-Term Care no longer accepts new Health Card Validation (HCV) enrolments or new Electronic Data Transfer (EDT) enrolments (claims submissions/ overnight batch eligibility checking) that require Bell Canada's Datapac service as a connection method to the ministry. The following options are available to replace Datapac connections.

The present status and future trends in computer/communication technology

Abstract: This paper reviews some aspects of computer communication network design in the light of recent research. The paper first concentrates on local distribution systems that use demand shared transmission lines. Then there is a discussion of communication protocol and the impact that it has on network performance. Finally there is some discussion of issues that face the designer of a general-purpose data network.

A network-oriented multiprocessor front-end handling many hosts and hundreds of terminals

Abstract: The authors discuss the design of a large-scale front-end computer in terms of system requirements, available technology, and the authors' experience with the ARPANET. The design is contrasted with that of the ARPANET TIP. Issues discussed include the choice of hardware configuration (CPU requirements, reliability, modularity, terminal interface units), what facilities to provide in the front-end, the communications protocol between front-end and Host, flow control on various inter-computer data paths, and data buffering strategies. The resulting system is being installed at the Research Computer Center at Bolt Beranek and Newman Inc.

A Research Program in Computer Technology

Abstract: : This program is aimed at applying computer science and technology to areas of high DoD/military impact. Research areas include: Specification Acquisition from Experts--study of acquiring and using program knowledge for making informal program specifications more precise; Military Message Experiment--development of an experimental user-oriented message service for potential large-scale military use; Program Verification--logical proof of program validity; Network Secure Communication--work on low-bandwidth, secure voice transmission using an asynchronous packet-switched network; Command and Control Graphics--development of a device-independent graphic system and graphics-oriented command and control applications programs; Autopsy--research program on source-to-source program translation combining automatic techniques with an interactive system to provide the human manager complete control over the translation process; Programming Research--development of a major time- shared microprogramming facility with an extension for emulation of microprocessors; Protection Analysis--methods of assessing the viability of security mechanisms of operating systems; Distributed Sensor Networks-- developing algorithms and communication protocols to support the operation of geographically distributed sensors; and Internetwork Concepts--exploring aspects of protocols for the interconnection of computer communication networks, specifically the design and prototype implementation of an internetwork computer message system and the design of internetwork host and gateway protocols.

Terminal-to-Host Protocol Specification.

Abstract: : This is the specification of the Terminal-to-Host Protocol (THP) which serves as both the terminal-to-terminal and terminal-to-process protocol for the AUTODIN II network. The AUTODIN II system provides the capability for geographically distributed computers, called hosts, to communicate with each other. The hosts are a diverse set of computers of differing manufacture, speed, word size, and operating system. The AUTODIN II system provides a mechanism for communication between hosts, the Transmission Control Protocol (THP) specifies how the hosts use this mechanism to provide communication services to processes, and finally, the THP provides a mechanism for offering services to human users. The reader of this document is assumed to be familiar with the concepts of the AUTODIN II system, TCP, and operating system concepts. In particular, the reader is expected to have read the AUTODIN II Specification and the TCP Specification. It is intended that the information presented here be sufficiently complete enough to allow a competent system programmer to implement a program module to carry out this protocol. This document draws heavily from the ARPA Network protocol documents on the Telnet Protocol. We wish to acknowledge the efforts of the many contributors to that collection. (Author)