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Communications, IEEE Transactions on

Issue 4 • Date April 1980

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Displaying Results 1 - 25 of 26
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Preface to the Special Issue

    Page(s): 409 - 412
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    Freely Available from IEEE
  • X.25 transaction-oriented features - datagram and fast select

    Page(s): 496 - 500
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    The latest proposed revisions to CCITT Recommendation X.25 for packet-switched service in public data networks now include two new capabilities suitable for transport of a small amount of data. The first provides datagram service for the transport of independent "message type" packets. The other new feature is the fast select facility which provides for the inclusion of 128 octets of user data in the call establishment packets for virtual call service. Both these new provisions greatly enhance the capability X.25 to efficiently support the broadest range of user applications. View full abstract»

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  • [Back cover]

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    Freely Available from IEEE
  • X.25 Interface and End-to-End Virtual Circuit Service Characteristics

    Page(s): 500 - 510
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    Public packet switching networks around the world use CCITT Recommendation X.25, which is the standard device-independent interface between packet networks and user devices operating in the packet-mode. Since its development in 1976 and with four years of network operational experience, the X.25 interface specification has reached a high level of maturity. A revised version of X.25 has been approved by CCITT Study Group VII at its meeting in February 1980. The revised X.25 specification is more complete than its predecessor, eliminates a number of ambiguous areas which lead to network implementation differences, and has been enhanced by the addition of new capabilities both to the X.25 interface and to the end-to-end service. This paper presents a consolidated view of the end-to-end characteristics of the virtual-circuit-based services accessible through the X.25 interface. It then discusses the characteristics of the revised X.25 interface, with emphasis on areas that have been addressed in the revised Recommendation. The revised Recommendation leads the way to greater commonality among network implementations. The increased functionality of the end-to-end virtual-circuit services has impact on the relationship of X.25 to system architectures being discussed by international standards bodies. View full abstract»

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  • DNA: The Digital Network Architecture

    Page(s): 510 - 526
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    Recognizing the need to share resources and distribute computing among systems, computer manufacturers have been designing network components and communication subsystems as part of their hardware/software system offerings. A manufacturer's general purpose network structure must support a wide range of applications, topologies, and hardware configurations. The Digital Network Architecture (DNA), the architectural model for the DECnet family of network implementations, has been designed to meet these specific requirements and to create a communications environment among the heterogeneous computers comprising Digital's systems. This paper describes the Digital Network Architecture, including an overview of its goals and structure, and details on the interfaces and functions within that structure. The protocols implementing the functions of DNA are described, including the motivations for the specific designs, alternatives and tradeoffs, and lessons learned from the implementations. The protocol descriptions include discussions of addressing, error control, flow control, synchronization, flexibility, and performance. The paper concludes with examples of DECnet operation. View full abstract»

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  • Path Control: The Transport Network of SNA

    Page(s): 527 - 538
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    A primary virtue of a communications system is transparency of the transport network to the person using the system. The layered structure of SNA provides for the separation of the transport network, called path control, from higher level functions involving the end users of the network. This paper describes the structure of the path control layer of SNA, focusing on connectivity, routing, and flow control. The end user's view of these architectural concepts is presented, as well as a discussion of the underlying formats and protocols. View full abstract»

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  • Flow Control: A Comparative Survey

    Page(s): 553 - 574
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    Packet switching offers attractive advantages over the more eonventional circuit-switched scheme, namely, flexibility in setting up user connections and more efficient use of resources after the connection is established. However, if user demands are allowed to exceed the system capacity, unpleasant congestion effects occur which rapidly neutralize the delay and efficiency advantages. Congestion can be eliminated by using an appropriate set of traffic monitoring and control procedures called flow control procedures. Flow control can be exercised at various levels in a packet network. The following levels are identified and discussed in this paper: hop level, entry-to-exit level, network access level, and transport level. For each level, the most representative techniques are surveyed and compared. Furthermore, the interaction between the different levels is discussed. View full abstract»

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  • Bit-Oriented Data Link Control Procedures

    Page(s): 455 - 467
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    The rapid growth of data communications in recent years, coupled with a movement from batch-oriented to transaction-oriented (interactive) type of operation, generated the need for a new, more efficient, more reliable, more flexible form of data link control procedure. A bit-oriented approach to data link control that has become the generally accepted standard around the world is discussed in this paper. The basic elements and structure of the procedure are described, some typical examples of operation reviewed, and a "crystal-balling" of the future is offered. View full abstract»

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  • Physical Level Protocols

    Page(s): 433 - 444
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    The physical level is the most basic protocol level in the hierarchy of data communication protocols. This level covers the physical interface between devices and the rules by which bits are passed from one to another. These devices may be, for example, a data terminal equipment (DTE) and a data circuit-terminating equipment (DCE, e.g., a modem). This paper describes the physical level and the national and international standards that have been developed for this level. Included are insights into the development of recently adopted physical level protocols. View full abstract»

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  • Protocol Representation with Finite-State Models

    Page(s): 632 - 643
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    A three-layer model of a computer network is used to introduce the concept of interface and of end-to-end protocols. Using a simple interface protocol as example, finite state automaton and Petri nets are introduced. The idea of an interface machine is rejected and the problems related to the transmission medium are approached. End-to end protocols request a global model which includes two local models and a transmission medium model. However, the local model has to be generalized. This eventually leads to the association of the state of the automaton with a context. Petri nets have also to be expanded. Models presented here have been successfully used for modeling transport protocols. View full abstract»

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  • SNA Function Management

    Page(s): 594 - 603
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    The path control network of Systems Network Architecture (SNA) supports communication between pairs of network addressable units called logical units, usually referred to as LU's. When communicating, information flows between LU's over a logical connection called a session. SNA defines three categories of messages which flow on LU-to-LU sessions-- session control, data flow control, and function management data. Thispaper discusses the structui'e and semantics of messages and protocols used by one LU to manage functions performed by a remote LU. The relatio.nship between distribution of function, the nature of the information, the technology, and the architecture of the data stream will be discussed. The data Streams used by SNA printers and 3270 displays will be used as examples. The paper concludes with a discussion of the possible impact of advancing electronic technology on data stream architecture. View full abstract»

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  • Terminal Protocols

    Page(s): 585 - 593
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    Terminal protocols provide basic services for the users of computer networks. This paper presents a survey of the architecture and mechanisms used in current terminal protocols. The paper disusses both parametric terminal protocols such as the CCITT X.3, X.28, and X.29 and virtual terminal protocols, such as the ARPANET TELNET protocol. Many of the problems encountered in terminal protocols recur in more complex forms in the more sophisticated protocols. View full abstract»

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  • OSI Reference Model--The ISO Model of Architecture for Open Systems Interconnection

    Page(s): 425 - 432
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    Considering the urgency of the need for standards which would allow constitution of heterogeneous computer networks, ISO created a new subcommittee for "Open Systems Interconnection" (ISO/ TC97/SC 16) in 1977. The first priority of subcommittee 16 was to develop an architecture for open systems interconnection which could serve as a framework for the definition of standard protocols. As a result of 18 months of studies and discussions, SC16 adopted a layered architecture comprising seven layers (Physical, Data Link, Network, Transport, Session, Presentation, and Application). In July 1979 the specifications of this architecture, established by SC16, were passed under the name of "OSI Reference Model" to Technical Committee 97 "Data Processing" along with recommendations to start officially, on this basis, a set of protocols standardization projects to cover the most urgent needs. These recommendations were adopted by T.C97 at the end of 1979 as the basis for the following development of standards for Open Systems Interconnectlon within ISO. The OSI Reference Model was also recognized by CCITT Rapporteur's Group on "Layered Model for Public Data Network Services." This paper presents the model of architecture for Open Systems Interconnection developed by SC16. Some indications are also given on the initial set of protocols which will-likely be developed in this OSI Reference Model. View full abstract»

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  • DCNA Higher Level Protocols

    Page(s): 575 - 584
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    This paper explains a philosophy for modeling the higher level communication functions into a network architecture for heterogeneous computer networks called Data Communication Network Architecture (DCNA), the logical structure of the architecture, and several protocols based on it. To specify higher level protocols among computers of different types, DCNA defines a logical model of a computer network consisting of three submodels: the basic model, the logical network model, and the virtual network model. The basic model represents a logical view of the network resources, e.g., processing power, files, data bases, I/O devices, and a layered structure for the basic mechanisms for accessing such resources, which incorporate the concept of sublevels as well as levels. The logical network model describes the mechanisms for unified management of network resources. The virtual network model describes the mechanisms for using network resources. The. common use of network resources, by several sets of interrelated applications is made easier by treating the logical network and the virtual network separately. These models form the basis for the stipulation of higher level protocols, such as network management protocols, message transfer protocols, virtual terminal protocols, and virtual file system protocols. View full abstract»

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  • Towards Analyzing and Synthesizing Protocols

    Page(s): 651 - 661
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    The production of error-free protocols or complex process interactions is essential to reliable communications. This paper presents techniques for both the detection of errors in protocols and for prevention of errors in their design. The methods have been used successfully to detect and correct errors in existing protocols. A technique based on a reachability analysis is described which detects errors m a design. This "perturbation technique" has been implemented and has successfully detected inconsistencies or errors in existing protocol designs including both X.21 and X.25. The types of errors handled are state deadlocks, unspecified receptions, nonexecutable interactions, and state smbiguities. These errors are discussed and their effects considered. An interactive design technique is then described that prevents design errors. The technique is based on a set of production rules which guarantee that complete reception capability is provided in the interacting processes. These rules have been implemented in the form of a tracking algorithm that prevents a designer from creating unspecified receptions and nonexecutable interactions and monitors for the presence of state deadlocks and ambiguities. View full abstract»

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  • Executable Description and Validation of SNA

    Page(s): 661 - 677
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    The definition of IBM's Systems Network Architecture (SNA) has evolved into a specification of a node in the form of a metaimplementation using formal, state-oriented descriptive techniques. This evolution is traced here, and the different formal techniques are described. The culmination of this process has been the development of a PL/I-based programming language, Format and Protocol Language (FAPL), as a descriptive tool. Using FAPL, the architects now define SNA by a programmed meta-implementation of a node. In this form, it is precise, readily accessible to the implementing product designers and programmers, and structurally close to the implementations. The essential features of the meta-implementation and of FAPL are described, along with the implications and advantages of describing the architecture in an executable form. One major benefit, already being realized, is the capability to test the logical consistency and completeness of the executable description itself. The current status of the validation of the executable description and sample results obtained are described. View full abstract»

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  • Routing Techniques Used in Computer Communication Networks

    Page(s): 539 - 552
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    An overview is provided in this paper of the routing procedures used in a number of operating networks, as well as in two commercial network architectures. The networks include TYMNET, ARPANET, and TRANSPAC. The network architectures discussed are the IBM SNA and the DEC DNA. The routing algorithms all tend to fall in the shortest path class. In the introductory sections, routing procedures in general are discussed, with specialization to shortest path algorithms. Two shortest path algorithms, one appropriate for centralized computation, the other for distributed computation, are described. These algorithms, in somewhat modified form, provide the basis for the algorithms actually used in the networks discussed. View full abstract»

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  • Procedures for Circuit-Switched Service in Synchronous Public Data Networks

    Page(s): 489 - 496
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    X.21 specifies a simple character-oriented procedure used to establish a transparent connection through a synchronous Public Data Network. The architecture of call establishment for X.21 is the same as that for call (virtual) establishment of X.25; in this regard, their functionality is nearly identical. This paper describes the background that went into the development of the Recommendation, discusses the architectural relationships, and presents the details of the X.21 circuit-switching protocol. View full abstract»

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  • Character-Oriented Data Link Control Protocols

    Page(s): 445 - 454
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    Character or byte-oriented data link control protocols have had a profound influence on the rapid and successful development of data communications networks. Although subject to certain limitations which led to the development of the now emerging bit-oriented protocols, character-oriented protocols have served our industry very well. Because of widespread implementation, they can be expected to continue this service into the foreseeable future. This paper offers an overview of characteroriented protocols and their place in the communications hierarchy. It examines these protocols from a historical and evolutionary perspective. It provides details, with examples, of the structure, functions, characteristics, and operation of the family of character-oriented link protocols. View full abstract»

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  • Internetwork Protocol Approaches

    Page(s): 604 - 611
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    The motivation for interconnecting networks is to provide one or more consistent services to the set of users of the interconnected networks. To provide these services either new end-to-end service protocols must be defined or the service protocols of the individual networks must be made to interwork. In either case the issues of addressing, routing, buffering, flow control, error control, and security must be considered. Two examples of interconnection strategy are examined: the interconnection of X.25 networks, and the interconnection of ARPA research networks. The models for interconnection of networks and the role of internetwork protocols are discussed. View full abstract»

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  • A General Transition Model for Protocols and Communication Services

    Page(s): 643 - 650
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    Different approaches have been used for the formal specification and verification of communication protocols. This paper explains the approach of nsing a general transition model which combines aspects of finite state transition diagrams and programming languages. Different ways of structuring a protocol into separate modules or functions are also discussed. The main part of the paper describes a method for exactly specifying the communication service provided by a protocol. Two aspects of a service specification are distinguished: 1) the local properties which characterize the interface through which the service may be accessed, and 2) the global properties which describe the "end-to-end" communication characteristics of the service. It is shown how the specification method is related to the general transition model for protocol specification. Verification is discussed briefly with emphasis on the use of invariant assertions in the context of finite state as well as programming language protocol descriptions. The discussed topics are demonstrated with examples based on the HDLC classes of procedures and the X.25 Virtual Circuit data transmission service. View full abstract»

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  • Multiaccess Protocols in Packet Communication Systems

    Page(s): 468 - 488
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    The need for multiaccess protocols arises whenever a resource is shared by many independent contending users. Two major factors contribute to such a situation: the need to share expensive resources in order to achieve their efficient utilization, or the need to provide a high degree of connectivity for communication among independent subscribers (or both). In data transmission systems, the communication bandwidth is often the prime resource, and it is with respect to this resource that we view multiaccess protocols here. We give in this paper a unified presentation of the various multiaccess techniques which we group into five categories: 1) fixed assignment techniques, 2) random access techniques, 3) centrally controlled demand assignment techniques, 4) demand assignment techniques with distributed control, and 5) mixed strategies. We discuss their applicability to different enivironments, namely, satellite channels, local area communication networks and multihop store-and-forward broadcast networks, and their applicability to different types of data traffic, namely stream traffic and bursty traffic. We also present the performance of many of the multiaccess protocols in terms of bandwidth utilization and message delay. View full abstract»

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  • Formal Methods in Communication Protocol Design

    Page(s): 624 - 631
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    While early protocol design efforts had to rely largely on seat-of-the-pants methods, a variety of more rigorous techniques have been developed recently. This paper surveys the formal methods being applied to the problems of protocol specification, verification, and implementation. In the specification area, both the service that a protocol layer provides to its users and the internal operations of the entities that compose the layer must be defined. Verification then consists of a demonstration that the layer will meet its service specification and that each of the components is correctly implemented. Formal methods for accomplishing these tasks are discussed, including state transition models, program verification, symbolic execution, and design rules. View full abstract»

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  • Pup: An Internetwork Architecture

    Page(s): 612 - 624
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    Pup is the name of an internet packet format (PARC Universal Packet), a hierarchy of protocols, and a style of internetwork communication. The fundamental abstraction is an end-to-end media-in dependent internetwork datagram. Higher levels of functionality are achieved by end-to-end protocols that are strictly a matter of agreement among the communicating end processes. This report explores important design issues, sets forth principles that have guided the Pup design, discusses the present implementation in moderate detail, and summarizes experience with an operational internetwork. This work serves as the basis for a functioning internetwork system that provides service to about 1000 computers, on 25 networks of 5 different types, using 20 internetwork gateways. View full abstract»

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Aims & Scope

IEEE Transactions on Communications focuses on all telecommunications including telephone, telegraphy, facsimile, and point-to-point television by electromagnetic propagation.

 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Robert Schober
University of British Columbia