Showing papers on "Communications protocol published in 1988"

Implementing remote procedure calls

Abstract: Remote procedure calls (RPC) are a useful paradigm for providing communication across a network between programs written in a high level language. This paper describes a package, written as part of the Cedar project, providing a remote procedure call facility. The paper describes the options that face a designer of such a package, and the decisions we made. We describe the overall structure of our RPC mechanism, our facilities for binding RPC clients, the transport level communication protocol, and some performance measurements. We include descriptions of some optimisations we used to achieve high performance and to minimize the load on server machines that have many clients.Our primary aim in building an RPC package was to make the building of distributed systems easier. Previous protocols were sufficiently hard to use that only members of a select group of communication experts were willing to undertake the construction of distributed systems. We hoped to overcome this by providing a communication paradigm as close as possible to the familiar facilities of our high level languages. To achieve this aim, we concentrated on making remote calls efficient, and on making the semantics of remote calls as close as possible to those of local calls.

Internetworking with TCP/IP

Abstract: An internationally best-selling, conceptual introduction to the TCP/IP protocols andInternetworking, this book interweaves a clear discussion of fundamentals and scientificprinciples with details and examples drawn from the latest technologies. Leading authorDouglas Comer covers layering and packet formats for all the Internet protocols, includingTCP, IPv4, IPv6, DHCP, and DNS. In addition, the text explains new trends in Internetsystems, including packet classification, Software Defined Networking (SDN), and meshprotocols used in The Internet of Things. The text is appropriate for individuals interested in learning more about TCP/IP protocols,Internet architecture, and current networking technologies, as well as engineers who buildnetwork systems. It is suitable for junior to graduate-level courses in Computer Networks,Data Networks, Network Protocols, and Internetworking.

The design philosophy of the DARPA Internet Protocols

Abstract: The Internet protocol suite, TCP/IP, was first proposed fifteen years ago. It was developed by the Defense Advanced Research Projects Agency (DARPA), and has been used widely in military and commercial systems. While there have been papers and specifications that describe how the protocols work, it is sometimes difficult to deduce from these why the protocol is as it is. For example, the Internet protocol is based on a connectionless or datagram mode of service. The motivation for this has been greatly misunderstood. This paper attempts to capture some of the early reasoning which shaped the Internet protocols.

Internetworking with TCP/IP: principles, protocols, and architecture

Abstract: From the Publisher: The third edition of this all-time best-selling book is still the reference for anyone who wants to work with the TCP/IP protocol suite. TCP/IP and ATM are two of the most important networking technologies. This is the first book that shows how to use the two technologies together.

An analysis of TCP processing overhead

Abstract: The authors report a preliminary analysis of the processing overhead of the transport protocol TCP (Transmission Control Protocol) in which they estimate the possible performance range of the protocol. The analysis was performed by compiling a version of TCP and counting the number of the instructions in the common path. The analysis suggests that fewer than 200 instructions are required to process a TCP packet in the normal case. This number is small enough to support very high-speed transmission if it were the major overhead. The authors offer some speculations about the actual source of processing overhead in network protocols. >

Specialized communications processor for layered protocols

Abstract: A special purpose communications protocol processor (CPP) provides more efficient processing of layered communications protocols--e.g. SNA (Systems Network Architecture) and OSI (Open Systems Interconnection)--than contemporary general purpose processors, permitting hitherto unavailable operations relative to high speed communication links. The CPP contains special-purpose circuits dedicated to quick performance (e.g. single machine cycle execution) of functions needed to process header and frame information, such functions and information being of the sort repeatedly encountered in all protocol layers, and uses instructions architected to operate these circuits. The header processing functions given special treatment in this manner include priority branch determination functions, register bit reshaping (rearranging) functions, and instruction address processing functions. Frame processing functions so handled include CRC (cyclic redundancy check) computations, bit insertion/deletion operations and special character detection operations.

Method of controlling communication in an ID system

Abstract: A memory of a data carrier attached to an article to be identified stores a classification code indicative of the data carrier's own communication protocol Plural types of communication protocols are registered, in correspondence with the classification codes thereof, in the memory of a controller capable of communicating with the data carrier Upon receiving a classification code transmitted by the data carrier, the controller selects from its memory a communication protocol indicated by the received classification code and then executes communication with the data carrier by using the selected communication protocol

Lan with interoperative multiple operational capabilities

Abstract: Two different communication protocols are interoperatively combined for use in a local area network (LAN). An enhanced protocol can be selected as an alternative to a common protocol during communication between enhanced nodes of the LAN. Signals communicated between nodes of the LAN in the first and second protocols create the appearance of valid activity in both protocols, and always communicate at least some valid information in one of the protocols and selectively communicate additional valid information in a second protocol. Preferably the signals applied in the second or enhanced protocol include signals which are inserted in such a way that they are transparent to the first protocol. Improved network management capabilities and data transfer rates are available as a result of the information communicated in the second protocol.

User-process communication performance in networks of computers

Abstract: The authors present a study of the performance achieved by user processes when using the IPC mechanisms as implemented in Berkeley Unix 4.2BSD in Ethernet based environments. The authors assess not only the impact that different processors, network hardware interfaces, and Ethernets have on the communication across machines, but also the effect of the loading of the hosts and communication media that participate in the interprocess communication mechanism. The measurements highlight the ultimate bounds on performance that may be achieved by user process applications communicating across machines, and serve as a guide in designing performance-critical applications. A detailed timing analysis is presented of the dynamic behavior of the TCP/IP and the UDP/IP network communication protocols' implementation in Berkeley Unix 4.2BSD. >

Algorithms for Automated Protocol Validation

Abstract: This paper studies the four basic types of algorithm that, over the last ten years, have been developed for the automated validation of the logical consistency of data communication protocols. The algorithms are compared on memory usage, CPU time requirements, and the quality, or coverage, of the search for errors. It is shown that the best algorithm, according to above criteria, can be improved further in a significant way, by avoiding a known performance bottleneck. The algorithm derived in this manner works in a fixed size memory arena (it will never run out of memory), it is up to two orders of magnitude faster than the previous methods, and it has superior coverage of the state space when analyzing large protocol systems. The algorithm is the first for which the search efficiency (the number of states analyzed per second) does not depend of the size of the state space: there is no time penalty for analyzing very large state spaces. The effectiveness of the new algorithm is illustrated with the validation of a protocol of a realistic size: the ANSI/IEEE Standard 802.2 for logical link control.

Design of the x-kernel

Abstract: The x-kernel is a configurable operating system kernel designed to support experimentation in interprocess communication and distributed programming. The x-kernel's underlying architecture provides a rich set of abstractions that are used to construct and compose communication protocols. The architecture is interesting because the abstractions are both general enough to accommodate a wide range of protocols and efficient enough to provide a useful testbed in which protocol performance can be accurately measured.

Network protocol translator including method and apparatus for reducing interprocess communication and data exchange overhead

Abstract: An method for interprocess communication and data exchange within a computer's software operating system executing on a computer network protocol translator having a central processing unit and associated memory, which includes encapsulating the message or data to be exchanged within certain header and footer information which defines the context of the transmission. Certain program routines are executed in conjunction with this context information which enable the software processes within the operating system to exchange data and to acknowledge the receipt of messages without having to generate and transmit return messages or pre-empt the operating system's execution sequence.

Survey of protocol verification techniques based on finite state machine models

Abstract: A survey is presented of techniques for verifying correctness properties of communications protocol design based on finite-state-machine (FSM) models. The conventional reachability analysis is first described, giving advantages and limitations. One major limitation is the so-called state-space explosion problem. To approach this and other problems, a survey of different approaches is presented. The author classifies the various techniques into categories. These include closed covers, localized protocol verification, divide-and-conquer, modified reachability analysis, and partial state exploration. Each technique is described in detail, including an analysis of its strengths and weaknesses. Based on this analysis, one technique is proposed as the basis for further work on a protocol verifier and analyzer workstation which is being designed as a protocol development tool. >

A system and method for version level negotiation

Abstract: The system and method of this invention enables a plurality of nodes (A,...., E) in a network to communicate with each other through a communication protocol that will be understood by any node that is a party to the present conversation. Each node may utilize a different version level of a distributed services program that allows nodes to communicate in a distributed environment. At the time a connection is initiated with another node in the network, the highest version level that both nodes have in common is determined. This common version level is then used as the protocol for any further communication.

Very high speed and high capacity packet switching for broadband ISDN

Abstract: The authors discuss and propose a very-high-speed and high-capacity packet-switching (HPS) architecture for a future broadband ISDN (integrated-services digital network). The HPS network accommodates various communication services, such as voice, high-speed data, high-speed still picture, and video services. The proposed architecture has three significant principles: a high-speed oriented simple network protocol, separation of signaling and network control from data transfer, and hardware switching. These principles provide fast- and high-throughput transmission for data packets and reliable transmission and processing for call-control packets. The HPS protocol structure is addressed, which provides high flexibility for various communications services as well as high-speed capability. A 3-Gb/s capacity and building-block-structured packet-switching system architecture, using bus- and loop-type switch fabric, is also presented. >

Communication system supporting remote operations

Abstract: A communication system for implementing remote operations between a PABX and a host computer, conforming to Open Systems Interconnect (OSI) communication protocol. Circuitry is provided in each of the PABX and host computer for generating and encoding invoke, return result, error and reject operation protocol data unit signals, for transmission between application layer entities of the PABX and host computer. In order to support invoking of asynchronous telephony operations, invoke address and server address fields are incorporated within the argument sequence and the result sequence of the invoke and return result operation protocol data unit signals, respectively.

Knowledge-based monitoring and control: an approach to understanding behavior of TCP/IP network protocols

Abstract: Complex, dynamic, and evolving network environments present difficult challenges for monitoring and control. We have encoded some of the expertise of human networking experts into a knowledge-based system that uses production rules and opportunistic scheduling, and have been using this system to better understand the behavior of the TCP/IP protocols and the applications that use them. Novel aspects of this research include understanding how to encode knowledge from this domain, and how to reason efficiently on real networking problems. The prototype system—KNOBS/TCP—can correctly identify many common problems that network experts would normally be required to find (e.g., improper or inefficient retransmission and ACK strategies, silly-window-syndrome, a subset of reset and connection closing anomalies, and basic problems with auxiliary protocols such as address resolution, and routing). Preliminary measurements indicate that the resulting system is reasonably fast and will scale well. In some important test cases, speedup of two orders of magnitude over analogous manual and partially automated techniques has been observed.

Experiments in SR with different upcall program structures

Abstract: This paper explores program designs for layered systems such as communication protocols and server/client systems that do not exhibit a strict hierarchy in their control flow. Clark has proposed structuring such systems, where both upward and downward control flow are required, to use efficient synchronous procedure calls between the layers whenever possible. The term upcall is used by Clark to describe this synchronous upward communication from server to client.Several techniques are possible for structuring such programs using upcalls. Comparisons are made by implementing a communication protocol described by Clark in three different ways. The first method implements all the protocol routines in a single large module. The second method structures the routines into modules occupying vertical slices of the protocol layers, and the third method structures the routines into modules corresponding to the protocol layers.Comparisons are made on two fronts: Preservation of modularity, in order to determine which method shows fault-tolerance and ease of programming, and program performance, which is a key motivation for the upcalls programming style. We conclude that the vertically layered protocol design is to be preferred unless there are many shared variables between the send-side and receive-side, as it is very efficient and provides the best protection of clients from each other. The horizontally layered design is the least efficient, but it is the easiest to program.

Image-capable interprocessor link communications protocol

Abstract: An image-capable interprocessor link communications protocol, includes a generalized set of communications rules designed to handle the large amounts of transmitted data and the high transfer speeds often associated with image-capable communications. These rules are designed to facilitate the exchange of image information across an interprocessor link without modifying or massaging it and without adding extraneous control information to it.

Source modelling for packet video

Abstract: Fast packet switching or asynchronous time division (ATD) networks have been proposed for integrated-services broadband communication systems because diversified services can be offered using unified protocols. Variable-rate video-encoding techniques are usually used in these communication systems to maintain constant video quality and to take advantage of the flexible nature of the ATD network. Since the bit rate is no longer a constant, statistical models are developed to measure the characteristics of the bit-rate sequence. A first-order Markov representation is proposed to describe the probabilistic behavior of the coded video sources. Based on these models, the ATD network protocol can be designed and analyzed. A general model is proposed for the coded source rate, and several special cases of the general model for different applications are described. The related issues of video coding in ATD networks are also discussed. >

Distributed reachability analysis for protocol verification environments

Abstract: A topic of importance in the area of distributed algorithms is the efficient implementation of formal verification techniques. Many such techniques are based on coupled finite state machine models, and reachability analysis is central to their implementation. SPANNER is an environment developed at AT&T Bell Laboratories, and is based on the selection/resolution model (S/R) of coupled finite state machines. It can be used for the formal specification and verification of computer communication protocols. In SPANNER, protocols are specified as coupled finite state machines, and analyzed by proving properties of the joint behavior of these machines. In this last step, reachability analysis is used in order to generate the “product” machine from its components, and constitutes the most time consuming part of the verification process. In this paper we investigate aspects of distributing reachability over a local area network of workstations, in order to reduce the time needed to complete the calculation. A key property which we exploit in our proposed design is that the two basic operations performed during reachability, the new state generation, and the state tabulation, can be performed asynchronously, and to some degree independently. Furthermore, each of these operations can be decomposed into concurrent subtasks. We provide a description of the distributed reachability algorithm we are currently in the process of implementing in SPANNER, and an investigation of the scheduling problems we face.

ARNS: a new link layer protocol

Abstract: A new link-layer communications protocol is presented for a packet switched, low-altitude, multiple-satellite network. The adaptive receive node scheduling (ARNS) protocol accommodates large numbers of low-cost satellites in nongeosynchronous orbits where global synchronization is not possible, as well as numerous terminals. Theoretical analysis and computer simulation of the protocol show that a satellite operating at a throughput of 1 Mb/s and maintaining simultaneous crosslinks with four neighboring satellites realize an average delay per packet of 11 ms. The 95% of delay figure is 22 ms. >

A methodology for constructing communication protocols with multiple concurrent functions

Abstract: A methodology is presented for the construction of communication protocols which perform several distinct functions simultaneously. The construction of such a multi-function protocol consists of three steps: (1) the development of component protocols for the different functions, (2) the integration of component protocols into a merged protocol, and (3) the specification of operational relationship among the component protocols. The conditions required for the resulting merged protocol to retain the safety properties, such as freedom from unspecified receptions, freedom from deadlocks, and boundedness, of the component protocols are discussed. The methodology is simple and facilitates the reuse of existing protocols. Two examples are given to illustrate its usage: a full-duplex data transfer protocol and another data transfer protocol with pipelining and flow control.

The synthesis of communication protocols

Abstract: We define a notation (specification language) for describing desired patterns of communication among components of a distributed system through multiport, unreliable channels. Our language specifies the network topology, and the kinds of information transmission desired. We give a polynomial-time algorithm for determining whether a specification is satisfiable; our algorithm can actually construct a protocol that achieves the specified exchange of information, optimized with respect to two possible criteria. Examples suggest that our method can automatically synthesize reasonably complex protocols.

On the effects of feedback in dynamic network protocols

Abstract: A framework is introduced that provides a unified way for proving correctness as well as analyzing performance of a class of communication protocols called (asynchronous) reset protocols. They are logarithmic transformers, converting protocols working in a static asynchronous network into protocols working in a dynamic asynchronous network. The design of reset protocols is a classical problem in communication networking, renowned for its complexity. A paradigm is developed that gives fresh insight into this complicated problem. This additional insight leads to the development of reset protocols with complexities bounded by the communication complexity of the original protocol. >

On the effects of feedback in dynamic network protocols (Preliminary Version)

Abstract: This paper introduces a new framework which provides a unified way for proving correctness as well as analyzing performance of certain, quite important, class of communication protocols, called (asynchronous) Reset Protocols. Those are algorithmic transformers, converting protocols working in a static asynchronous network into protocols working in a dynamic asynchronous network. Design of Reset protocols is a classical problem in communication networking, and is renowned for its complexity. This paper develops a new paradigm, which gives new insight into this complicated problem. This additional insight enables to develop new Reset protocols, whose complexities are bounded by communication complexity of the original protocol.

PROSPEC: an interactive programming environment for designing and verifying communication protocols

Abstract: The PROSPEC software environment for designing and verifying communication protocols is described. It integrates several tools that implement methods for protocol verification and construction (i.e., fair reachability analysis, multiphase construction, and protocol projection). The system provides a unified graphical interface to facilitate the application of these methods and creates an interactive environment for specifying, verifying, and designing communication protocols. PROSPEC was used successfully to design and verify versions of BSC, X.21, X.25, and Telnet document transfer protocols. >

Guaranteeing Performance for Real-Time Communication in Wide-Area Networks

Abstract: : The increasing importance of distributed multimedia applications and the emergence of user interfaces based on digital audio and digital video will soon require that computer communication networks offer real-time services. This paper argues that the feasibility of providing performance guarantees in a wide-area network should be investigated, and describes a possible approach. We present a model of the network to be studied, and discuss its generality, as well as the presumable limits to its validity in the future. We also give a careful formulation of the problem, including a precise definition of the guarantees to be provided and a provably correct scheme for the establishment of real-time connections with deterministic, statistical, and best-effort delay bounds.