Showing papers on "Communications protocol published in 1987"

The DARPA packet radio network protocols

Abstract: In this paper we describe the current state of the DARPA packet radio network. Fully automated algorithms and protocols to organize, control, maintain, and move traffic through the packet radio network have been designed, implemented, and tested. By means of protocols, networks of about 50 packet radios with some degree of nodal mobility can be organized and maintained under a fully distributed mode of control. We have described the algorithms and illustrated how the PRNET provides highly reliable network transport and datagram service, by dynamically determining optimal routes, effectively controlling congestion, and fairly allocating the channel in the face of changing link conditions, mobility, and varying traffic loads.

An introduction to Estelle: a specification language for distributed systems

Abstract: Estelle is a Formal Description Technique, defined within ISO (International Organization for Standardization) for specification of distributed, concurrent information processing systems. In particular, Estelle can be used to describe the services and protocols of the layers of Open Systems Interconnection (OSI) architecture defined by ISO. Its present ISO status is Draft International Standard (DIS 9074). The article outlines syntactic and semantic aspects of this description technique.

The Interrogator: Protocol Secuity Analysis

Abstract: The Interrogator is a Prolog program that searches for security vulnerabilities in network protocols for automatic cryptographic key distribution. Given a formal specification of the protocol, it looks for message modification attacks that defeat the protocol objective. It is still under developement, but is has been able to rediscover a known vulnerability in a published protocol. It is implemented in LM-Prolog on a Lisp Machine, with a graphical user interface.

A Test Design Methodology for Protocol Testing

Abstract: Communication protocol testing can be done with a test architecture consisting of remote Lower Tester and local Upper Tester processes. For real protocols, tests can be designed based on the formal specification of the protocol which uses an extended finite state machine model. The specification is transformed into a simpler form consisting of normal form transitions. It can then be modeled by a control and a data flow graph. The graphs are decomposed into subtours and data flow functions, respectively. Tests are designed by considering parameter variations of the input primitives of each data flow function and determining the expected outputs. The methodology gives complete test coverage of all data flow functions and control paths in the specification. Functional fault models are proposed for functions that are not formally specified.

Automated Protocol Validation in Argos: Assertion Proving and Scatter Searching

Abstract: Argos is a validation language for data communication protocols. To validate a protocol, a model in Argos is constructed consisting of a control flow specification and a formal description of the correctness requirements. This model can be compiled into a minimized lower level description that is based on a formal model of communicating finite state machines. An automated protocol validator trace uses these minimized descriptions to perform a partial symbolic execution of the protocol to establish its correctness for the given requirements.

Interactive State-Space Analysis of Concurrent Systems

Abstract: The introduction of concurrency into programs has added to the complexity of the software design process. This is most evident in the design of communications protocols where concurrency is inherent to the behavior of the system. The complexity exhibited by such software systems makes more evident the need for computer-aided tools for automatically analyzing behavior.

The Crystal Multicomputer: Design and Implementation Experience

Abstract: This paper presents an overview of the hardware and software components of the Crystal multicomputer project. The goal of the Crystal project is to design and implement a vehicle that serves a variety of research projects involving distributed computation. Crystal can be used simultaneously by multiple research projects by partitioning the available processors according to the requirements of each project. Users can employ the Crystal multicomputer in several ways. Projects such as operating systems and database machines that need direct control of processor resources (clock, memory management, communication devices) can be implemented using a reliable communication service (the "nugget" that resides on each node processor. Projects that prefer a higher-level interface can be implemented using the Charlotte distributed operating system. Finally, users interested in Crystal principally as a cycle server can run UNIX® jobs on node machines using the "remote" unix service. Development, debugging, and execution of projects can take place remotely under the control of any of several UNIX hosts. Acquiring a partition of machines, resetting each machine, and then loading an application onto each machine is performed by invoking a UNIX-resident program (the "nuggetmaster"). Communication with node machines in a partition is facilitated by a virtual terminal and window mechanism. Crystal is fully operational and has been used to support a variety of research projects. To illustrate the flexibility provided by the Crystal environment, four of these projects are described.

Probabilistic Verification of Communication Protocols

Abstract: Complete behavior of a communication protocol can be very large. It is worth investigating whether partial exploration of the behavior generates reasonable results. We present such a procedure which performs partial exploration using most-probable-first search. Some of the ideas used in this procedure are based on a convolutional decoding procedure due to Jelinek and a performance evaluation procedure due to Rudin. Multiple trees of protocol behavior are constructed. Some results on estimating the probability of encountering an unexplored state in a finite run of a protocol are also presented.

Semiautomatic Implementation of Communication Protocols

Abstract: The use of formal specifications in software development allows the use of certain automated tools during the specification and software development process. Formal description techniques have been developed for the specification of communication protocols and services. This paper describes the partial automation of the protocol implementation process based on a formal specification of the protocol to be implemented. An implementation strategy and a related software structure for the implementation of state transition oriented specifications is presented. Its application is demonstrated with a much simplified Transport protocol. The automated translation of specifications into implementation code in a high-level language is also discussed. A semiautomated implementation strategy is explained which highlights several refinement steps, part of which are automated, which lead from a formal protocol specifieation to an implementation. Experience with several full implementations of the OSI Transport protocol is described.

Spanner: A Tool for the Specification, Analysis, and Evaluation of Protocols

Abstract: SPANNER is a software package for the specification, analysis, and evaluation of protocols. It is based on a mathematical model of coordinating processes called the selection/resolution model.

Communication networks management

Abstract: Network protocols models of dynamics networks transmission via unreliable path reductions transmission via unreliable unreliable network security functions.

Distributed Transaction Processing and The Camelot System

Abstract: This paper describes distributed transaction processing, a technique used for simplifying the construction of reliable distributed systems. After introducing transaction processing, the paper presents models describing the structure of distributed systems, the transactional computations on them, and the layered software architecture that supports those computations. The software architecture model contains five layers, including an intermediate layer that provides a common set of useful functions for supporting the highly reliable operation of system services, such as data management, file management, and mail. The functions of this layer can be realized in what is termed a distributed transaction facility. The paper then describes one such facility — Camelot. Camelot provides flexible and high performance commit supervision, disk management, and recovery mechanisms that are useful for implementing a wide class of abstract data types, including large databases. It runs on the Unix-compatible Mach operating system and uses the standard Arpanet IP communication protocols. Presently, Camelot runs on RT PC’s and Vaxes, but it should also run on other computers including shared-memory multiprocessors.

Network Protocols and Tools to Help Produce Them

Abstract: Protocols are the nervous system of computer-communication systems. They provide communication between remote as well as co-located pro­ cesses; they synchronize component tasks working towards a common goal. There are three reasons for the growing interest in protocols. First, now that it is economically feasible to build small processing units, distributed systems have become attractive for most applications. Protocols hold distributed systems together. Second, there is a growing desire to provide communication between heretofore independent information-handling systems. These systems are apt to function in different ways and have different internal languages, protocol conversion bridges the gaps. Third, as systems-even single-processor systems-provide more and more func­ tion, the only chance of containing complexity is to partition that function, using protocols to integrate the partitions. Most teleprocessing-equipment manufacturers have long since recog­ nized that to be able to interconnect their various products efficiently, they must define and abide by a well-defined architecture. Such an architecture defines (a) the format and structure of the messages that flow between the various system components, and (b) the protocols, the rules according to

Experimental analysis of layered Ethernet software

Abstract: We conducted a series of experiments contrasting the performance of a standard communications protocol with the performance of modified versions of the protocol. The results of these experiments divide the communications delay in Sun's implementation of UDP/IP on a 10 megabit per second Ethernet into categories such as buffer copying, context switching, protocol layering, internet address translation, and checksum computation. We also describe the implementation of our own simple Ethernet protocol which propagates messages in slightly less than half the time required by UDP/IP. Our experimental results indicate that the most expensive of these are socket layering and connection, even though most of the layering in the UDP/IP implementation is incidental to the protocol.

A Framework for Agreement

Abstract: Over the years, the Byzantine Generals Problem has become notorious for the complexity of its solutions. This is particularly true for protocols with the early-stopping property. Moreover, minor changes in the fault model resulted in drastically different protocols. In this paper, we expose a fundamental technique that underlies most of these protocols. We then derive a simple, intuitive, failure-model-independent scheme for solving the Byzantine Generals Problem. The derivation reveals when it is possible to stop early. Using this result, we extend the basic framework into one that yields simple, early-stopping protocols for the Eventual Byzantine Agreement problem. We demonstrate the utility of our results by deriving an early-stopping protocol.

Transaction commitment at minimal communication cost

Abstract: We consider the communication protocol for transaction commitment in a distributed database. Specifically, the connection between the structure of communication among the participating sites, and the communication network topology is investigated. In order to do so, the cost of transaction commitment is defined as the number of network hops that messages of the protocol must traverse. We establish the necessary cost for transaction commitment, and show that it is also sufficient. A simple distributed algorithm is presented to prove sufficiency. Our algorithm is also time-efficient, and in order to prove that we show that the timing of our algorithm is optimal within a natural class of commit-protocols.

A fault tolerant replicated storage system

Abstract: One way of achieving high availability of data in a distributed system is to replicate the data on several nodes. We present an algorithm for a replicated storage system which takes advantage of the high reliability of ETHERNET local area networks and their broadcast capability. The algorithm is both simple and efficient. It does not use reliable communication protocols and does not require a separate recovery procedure or knowledge of the current status (up or down) of the other nodes in the network. It guarantees that all transactions will be completed within a finite time and that no record will be locked indefinitely. We discuss the properties of the algorithm and some extensions to it. We also compare it with some other methods of managing replicated storage systems.

The IC system for protocol development

Abstract: The realization of a new protocol is a long and complicated procedure whose inherent technical difficulty is exacerbated by the scarcity of useful tools. This paper discusses the initial use of a system that is being developed by Bell Communication Research to help in the specification, analysis, and implementation of communications protocols. This paper describes the application of this system to the specification and implementation of an industry standard protocol.

Communication protocols in instrumentation

Abstract: Consideration is given to the concept of the 'intelligent transducer' with particular reference to the expected capabilities of an instrument incorporating local signal processing. The implications of devolving the tasks of instrument management and data transmission to separate processing elements are explored. The use of communication protocols within instrumentation systems is discussed both in the context of techniques currently in use and proposed future standards. A three-layer instrumentation protocol model consisting of physical link, transport mechanism and application data layers is defined together with a consideration of the individual layers. The networking of power and data within distributed instrumentation systems is considered with a view to the commercial implications of the multiplicity of techniques both existing and proposed.

Internet protocol implementation experiences in PC-NFS

Abstract: A team at Sun Microsystems East Coast Division has been engaged in developing and supporting a PC implementation of Sun's Network File System (NFS™) protocols. In the course of this work we were faced with the problem of implementing Internet protocol software within the PC environment. Our experiences revealed that there are some unique obstacles to be overcome in this kind of system, and indicate that further work is needed in the development of protocols to manage networks of low-end machines.

Advanced Map For Real-Time Process Control

Abstract: MAP, a communications protocol for factory automation proposed by General Motors [1], has been accepted by users throughout the world and is rapidly becoming a user standard. In fact, it is now a LAN standard for factory automation. MAP is intended to interconnect different devices, such as computers and programmable devices, made by different manufac­ turers, enabling them to exchange information. It is based on the OSI intercomputer com­ munications protocol standard under development by the ISO. With progress and standardi­ zation, MAP is being investigated for application to process control fields other than factory automation [2]. The transmission response time of the network system and central­ ized management of data exchanged with various devices for distributed control are import­ ant in the case of a real-time process control with programmable controllers, computers, and instruments connected to a LAN system. MAP/EPA and MINI MAP aim at reduced overhead in protocol processing and enhanced transmission response. If applied to real-time process control, a protocol based on point-to-point and request-response transactions limits throughput and transmission response.This paper describes an advanced MAP LAN system applied to real-time process control by adding a new data transmission control that performs multicasting communication voluntarily and periodically in the priority order of data to be exchanged.

Automated Analysis of Discrete Communication Behavior

Abstract: An objective methodology for the specification and analysis of communicating processes is presented. It is based on an algebraic theory that is a formalization of a particular state machine model. The approach recognizes the fact that the complexity of system interactions is such that computer aid is not only appropriate but necessary for any practical design methodology.

Formal description techniques: communication tools for data communication specialists. Formal specification and implementation of a file transfer protocol

Abstract: The ISO has developed two Formal Description Techniques to describe precisely data communication protocols. One of these namely ESTELLE, has been used to specify a subset of the Network Independent File Transfer Protocol, also called Blue Book, promoted by the Joint Network Team in the United Kingdom. An implementation in the C programming language is currently being derived from this partial specification. Some difficulties have been encountered during both the process of building the specification and the process of building the corresponding implementation. They are listed and explained. Some of them are suprisingly not due to the problem but result from the use of the solving tool!

Directed Network Protocols

Abstract: We present a uniform approach to the description and validation of several known and unknown distributed algorithms for solving control problems in computer networks using unidirectional communication. After introducing two basic protocols, we use these to build algorithms for Resynch [Fi79], Connectivity, Min Hop Routing and Distributed Infimum Approximation [Te86]. All protocols are extended in a uniform way to cope with changing network topology and the failure of nodes and links. The protocols are all optimal in time complexity.

Protocol conversion system for line switching network

Abstract: PURPOSE:To apply automatically protocol conversion without large sized subscriber-interface-circuit by providing a holding function of attribute information to a line terminator and reconnecting it to a protocol converter based on the discrimination of the possibility of direct communication between subscriber terminals. CONSTITUTION:The user of the subscriber terminal devices 4, 5 uses attribute input circuits 25, 35 so as to change or register the attribution information at the introduction of the subscriber terminal device and at the change of the communication protocol used for the subscriber terminal device and holding circuits 23, 33 hold the attribute information when the registration is conducted once. When it is discriminated that the direct communication is disabled, the controller 12 sets newly a communication path B to the protocol converter 14 in a channel switch 13. When the protocol converter 14 receives the information and number, then the protocol converting function is selected according to the attribute information and the controller 12 has a command to set the communication path C to the subscriber terminal device 5 in the channel switch 13.

Communication protocol converter

Abstract: PURPOSE:To simplify a job by inputting a communication protocol expressed by a Petri net language, by using an interaction input/output device, generating a Petri net data by using a Petri net language processor, and generating a communication protocol converting program from the Petri net data of two kinds of communication protocols which have been inputted CONSTITUTION:An operator 22 inputs a communication protocol 13 which gas been expressed by a Petri net language, to a protocol converter 14 by using an interaction input/output device 15 This input is edited by a Petri net editor 16 and stored in a Petri net data file 19 Next, the contents of the Petri net data file 19 are translated to an execution object program by a Petri net language processor 8, and stored in a file 20 In order to execute a protocol conversion between two communication protocols, a protocol conversion processor 18 reads out an execution object program of two communication protocols from the file 20 and executes its coupling and editing

The Empirical Evaluation of a Security-Oriented Datagram Protocol

Abstract: Performance considerations played an important role in the design of the Authenticated Datagram Protocol (ADP), a subtransport-level host-to-host datagram protocol that contains cryptographic mechanisms for end-to-end authentication and, optionally, privacy of messages. Several performance-motivated features were introduced into ADP. This paper describes the first phase of a measurement-based study of ADP intended to determine the actual effects of each of these features on the protocol''s performance. The experiments were trace-driven, and took place between two workstations in a laboratory setting. The results in every case demonstrated the usefulness of the features in question, but not always for the reasons that motivated their introduction into the design.

Subtransport Level: The Right Place for End-to-End Security Mechanisms

Abstract: We argue that end-to-end authentication and privacy in loosely-coupled distributed systems are not only achievable by mechanisms at the host-to-host (i.e., subtransport) level under generally satisfiable conditions, but that this solution can be more advantageous than those based on security mechanisms at higher levels of the protocol hierarchy in terms of both functionality and performance. We introduce a model of communication security and a subtransport-level protocol called ADP the Authenticated Datagram Protocol, which provides end-to-end authentication and privacy consistently with the definitions of the model. We then discuss the advantages of the subtransport approach, and present some experimental results from the measurement of a prototype of ADP that confirm the expected performance benefits of this approach.