Showing papers on "Communications protocol published in 1994"

Npsnet: A network software architecture for largescale virtual environments

Abstract: This paper explores the issues involved in designing and developing network software architectures for large-scale virtual environments. We present our ideas in the context of NPSNET-IV, the first 3-D virtual environment that incorporates both the IEEE 1278 distributed interactive simulation DIS application protocol and the IP multicast network protocol for multiplayer simulation over the Internet.

Analysing real-time communications: controller area network (CAN)

Abstract: The increasing use of communication networks in time-critical applications presents engineers with fundamental problems with the determination of response times of communicating distributed processes. Although there has been some work on the analysis of communication protocols, most of this is for idealised networks. Experience with single-processor scheduling analysis has shown that models which abstract away from implementation details are at best very pessimistic, and at worst lead to an unschedulable system being deemed schedulable. In this paper, we derive an idealised scheduling analysis for the CAN real-time bus, and then study two actual interface chips to see how the analysis can be applied. >

System and method for running multiple incompatible network protocol stacks

Abstract: A system and method for operating a network client machine to simultaneously utilize two protocol stacks which implement the same protocol. The system and method routes incoming packets of information into the appropriate protocol stack by prescanning the incoming packet and comparing a portion of the packet with a table in memory of sockets used for one of the two stacks. If a match exists with any entry in the table, the system and method routes the packet to the appropriate stack. If no match is found between the incoming packet and the table, the packet may then be offered to the second protocol stack. The unique socket numbers are selected by one of the protocol stacks while both stacks maintain a table of active sockets.

ASX: an object-oriented framework for developing distributed applications

Abstract: The ADAPTIVE Service eXecutive (ASX) is a highly modular and extensible object-oriented framework that simplifies the development and configuration of distributed applications on shared memory multi-processor platforms. This paper describes the structure and functionality of the ASX framework's object-oriented architecture. In addition, the paper presents the results of performance experiments conducted using ASX-based implementations of connection-oriented and connectionless protocols from the TCP/IP protocol family. These experiments measure the performance impact of alternative methods for parallelizing communication protocol stacks. Throughout the paper, examples are presented to indicate how the use of object-oriented techniques facilitate application extensibility, component reuse, and performance enhancement.

Managing and distributing data objects of different types between computers connected to a network

Abstract: A data management and distribution system has been described that includes router processes for controlling data communications between child processes running on computers connected by a network. Preferably, a router process runs on each computer, with the application processes running on the computer connected directly to the router process. As a result, all interprocess communications must pass through the routers. Each router process includes a connection table listing its connections with all other router and application processes, as well as an interest table listing the type of objects that each of the other processes are interested in receiving. Data communication is accomplished by an application process providing an object to its local router, which then distributes the object to all other interested routers. The object includes a destination list indicating which processes are to receive the object. Thus, with the use of routers, application processes that need to communicate with each other over a network need not know the intricate details (such as the communications protocol used, the exact address of the receiving process, etc.) involved in transmitting information. By placing the burden of managing the network communications on the local routers, the complexity of the application code is reduced since it has only a single connection to its local router.

Flow synchronization protocol

Abstract: Presents an adaptive flow synchronization protocol that permits synchronized delivery of data to and from geographically distributed sites. Applications include inter-stream synchronization, synchronized delivery of information in a multisite conference, and synchronization for concurrency control in distributed computations. The contributions of this protocol in the area of flow synchronization are the ability to synchronize over arbitrary topologies, the introduction of an adaptive synchronization delay, the flexibility to maintain multiple synchronization groups, and the use of a modular architecture that permits the application to tailor synchronization calculations to its service requirements. The authors take advantage of network protocols capable of maintaining network clock synchronization in the millisecond range. >

Communications signaling protocols

Abstract: A modular suite of peer-to-peer protocols that are independent of the communications network architecture supported, and the type of switching systems (packet-switched or circuit-switched), is used for a broadband and/or narrowband communications network. The protocols are comprised of client-server-oriented signaling messages that are restricted to include information and parameters associated with only one particular function of traditional call processing.

Method and apparatus for pacing communications in a distributed heterogeneous network

Abstract: A data communication method and apparatus is presented that allows communication in a distributed heterogeneous network. Communications managers reside in local processing environments and are responsible for interfacing local end users with the remainder of the heterogeneous network. Each communications manager receives distribution units from end users, the distribution units being assigned various priority levels and levels of assurance. Within each communications manager, an adjacent communications manager is determined in accordance with a communications path to a destination for the distribution unit. The distribution unit is then configured according to a network protocol stack existing between the communications manager and the adjacent communications manager, and the distribution units are transmitted according to priority. Each communications manager can have any number of adjacent communications managers each communicating through different network protocol stacks. Also described is load distribution among a complex of processors that share common functions, as well as control of information flow between adjacent communications managers.

A systematic approach to host interface design for high-speed networks

Abstract: Optical fiber has made it possible to build networks with link speeds of over a gigabit per second; however, these networks are pushing end-systems to their limits. For high-speed networks (100 Mbits per second and up), network throughput is typically limited by software overhead on the sending and receiving hosts. Minimizing this overhead improves application-level latency and throughput and reduces the number of cycles that applications lose to communication overhead. Several factors influence communication overhead: communication protocols, the application programming interface (API). and the network interface hardware architecture. The author describes how these factors influence communication performance and under what conditions hardware support on the network adapter can reduce overhead. He first describes the organization of a typical network interface and discusses performance considerations for interfaces to high-speed networks. He then discusses software optimizations that apply to simple network adapters and show how more powerful adapters can improve performance on high-speed networks. >

Proof-Checking a Data Link Protocol

Abstract: A data link protocol developed and used by Philips Electronics is modeled and verified using I/O automata theory. Correctness is computer-checked with the Coq proof development system.

Applications of voice processing to telecommunications

Abstract: The ways in which people communicate are changing rapidly. The options are many and diverse, ranging from voice calls over wireless networks, to video calls over the conventional wired network, ISDN video, FAX, e-mail, voice mail, beeper services, data services, audio teleconferencing, video teleconferencing, and so-called scribble phone service (transmission of arbitrary handwritten input). This revolution in communications is being fueled by several sources, including the availability of low-cost, low-power, computation in both DSP and RISC chips, larger and cheaper memory chips, improved algorithms for communications (e.g., modems, signaling) and signal processing, and finally the creation of world-wide standards for transmission, signal compression, and communication protocols. The broad goal of the communications revolution is to provide seamless and high-quality communications between people (or groups of people), anywhere, anytime, and at a reasonable price. Although there are many technologies that form the bases for the communications environment of the twenty-first century, one of the key technologies for making the vision a reality is voice processing. In this paper we attempt to show, by example, how voice processing has been applied to specific problems in telecommunications, and how it will grow to become an even more essential component of the communications systems of the twenty-first century. >

A mobile networking system based on Internet protocol

Abstract: Users of portable computers would like to carry their laptops with them whenever they move from one place to another and yet maintain transparent network access through the wireless link. The existing set of network protocols do not meet this requirement since they were designed under the assumption of a stationary network topology in which hosts do not change their location over time. The authors' approach, which is based on the use of a natural model and an existing IP option, does not introduce any new protocol and achieves optimal routing. The solution is transparent to transport and higher layers, and does not require any changes to stationary hosts and routers. The model is natural, because the authors coordinate a collection of mobile hosts (MHs) as a new IP network. They route packets to the MHs by using a router. The router is special because once it receives a packet, it does special things to ensure its safe delivery to its destination (the MH). This special operation is invisible to existing hosts and routers, so all the routing difference due to movement of the hosts can be hidden and effected by mechanisms under the control of the special entities. The other part of the model, which is a very natural part of a physical wireless data communications system, is the transceiver (access point), which collects wireless packets from a MH for delivery to existing hosts along existing wired networks. This transceiver provides the reference point by which the location of the MH is known.

Software overhead in messaging layers: where does the time go?

Abstract: Despite improvements in network interfaces and software messaging layers, software communication overhead still dominates the hardware routing cost in most systems. In this study, we identify the sources of this overhead by analyzing software costs of typical communication protocols built atop the active messages layer on the CM-5. We show that up to 50–70% of the software messaging costs are a direct consequence of the gap between specific network features such as arbitrary delivery order, finite buffering, and limited fault-handling, and the user communication requirements of in-order delivery, end-to-end flow control, and reliable transmission. However, virtually all of these costs can be eliminated if routing networks provide higher-level services such as in-order delivery, end-to-end flow control, and packet-level fault-tolerance. We conclude that significant cost reductions require changing the constraints on messaging layers: we propose designing networks and network interfaces which simplify or replace software for implementing user communication requirements.

Process for automatic conversion for porting telecommunications applications from the TCP/IP network to the OSI-CO network, and module used in this process

Abstract: The invention relates to an address conversion process for porting a telecommunications application APP from the TCP/IP network to the OSI/CO network, and to an address conversion module used in this process. In a known manner, access to the networks is authorized by way of a "socket" interface (SOC) for the TCP/IP network, and an "XTI" interface for the OSI/CO network. In a notable manner, the "socket" interface calls (SC), like a plurality of system cells (SY), are in a first time period oriented, at the moment of the link editing phase prior to obtaining the executable, to a module (W) for automatic address conversion of the library type. This module (W) then performs the conversion of the addresses specific to the TCP/IP network into addresses of the OSI/CO network and enables the passage from the TCP/IP protocol to the OSI/CO protocol. After conversion, the calls are transmitted to the "XTI" interface and can be used directly in the OSI/CO network. Only the calls intended for the TCP/IP network are processed; all other calls (NT) are returned to the system.

Telecommunication switch having programmable network protocols and communications services

Abstract: A telecommunications protocol development environment which enables a user to define a separate finite state machine for each port provided by a programmable telecommunications switch. Protocols for various telecommunications applications and software layers may be developed.

Performance issues in parallelized network protocols

Abstract: Parallel processing has been proposed as a means of improving network protocol throughput Several different strategies have been taken towards parallelizing protocols A relatively popular approach is packet-level parallelism, where packets are distributed across processorsThis paper provides an experimental performance study of packet-level parallelism on a contemporary shared-memory multiprocessor We examine several unexplored areas in packet-level parallelism and investigate how various protocol structuring and implementation techniques can affect performance We study TCP/IP and UDP/IP protocol stacks, implemented with a parallel version of the x-kernel running in user space on Silicon Graphics multiprocessorsOur results show that only limited packet-level parallelism can be achieved within a single connection under TCP, but that using multiple connections can improve available parallelism We also demonstrate that packet ordering plays a key role in determining single-connection TCP performance, that careful use of locks is a necessity, and that selective exploitation of caching can improve throughput We also describe experiments that compare parallel protocol performance on two generations of a parallel machine and show how computer architectural trends can influence performance

System for executing high speed communication protocol processing by predicting protocol header of next frame utilizing successive analysis of protocol header until successful header retrieval

Abstract: Communication control equipment for connecting a computer system to a network and supporting the computer system to set a plurality of connections on the network and perform parallel communication between computers. The communication control equipment includes an interface circuit for the computer system, a microprocessor for performing communication control processing, a local memory for storing programs and work data, a buffer memory for temporarily storing transmission and reception data, a DMA transfer unit for performing data transfer between a memory in the computer system and the buffer memory and protocol header transfer between the buffer memory and the local memory, a network controller for controlling transmission and reception of data to the network, and a header retrieval unit for predicting a protocol header of a frame to be next received in correspondence to each of a plurality of connections and retrieving a header corresponding to a protocol header of a received frame transferred by the DMA transfer unit.

Network protocol sensor

Abstract: A method of determining which of plural protocols are active on a computerized local area network. Each of plural frame types are registered with a link support layer (LSL) which monitors network communications for broadcast frame packets. A frame packet which matches a first one of the frame types is provided from LSL, and protocol header information in the received frame packet is decoded so as to determine protocol used in the frame packet. The first frame type is de-registered from LSL, a first protocol stack corresponding to the determined protocol is initialized using the first frame type, the first protocol stack is loaded, and the first protocol stack registers itself with LSL so that the first protocol stack receives future frame packets which match the first frame type. Thereafter, if LSL encounters any other frame types, the above processing is repeated so as to load and register any other needed protocol stacks.

Fundamentals of Telecommunication Networks

Abstract: Introduction to Networks Queuing Systems The Data Link Layer and X.25 Flow and Congestion Control Multiple Access Communication Protocols Local Area Network Protocols and Standards Transport Layer Protocols Switching Techniques and Fast-Packet Switching.

A model of computation for the NRL Protocol Analyzer

Abstract: We develop a model of computation for the NRL Protocol Analyzer by modifying and extending the model of computation for Burrows, Abadi, and Needham (BAN) logic (M. Burrows et al., 1990) developed by M. Abadi and M. Tuttle (1991). We use the results to point out the similarities and differences between the NRL Protocol Analyzer and BAN logic, and discuss the issues this raises with respect to the possible integration of the two. >

A LOTOS extension for the performance analysis of distributed systems

Abstract: Performance analysis and formal correctness verification of computer communication protocols and distributed systems have traditionally been considered as two separate fields. However, their integration can be achieved by using formal description techniques as paradigms for the development of performance models. This paper presents a novel extension of LOTOS, one of the two formal specification languages that were standardized by ISO. The extension is specifically conceived to integrate performance analysis and formal verification. The extended language syntax and semantics are formally defined, along with a mapping from extended specifications to performance models, The mapping preserves the specified observable behavior. Two simple examples, a stop-and-wait protocol and a time-sharing system, are used to concretely demonstrate the new approach and to validate it. >

Signatures for a network protocol stack: a systems application of Standard ML

Abstract: Advanced programming languages such as Standard ML have rarely been used for systems programming tasks such as operating systems and network communications. In order to understand more fully the requirements of systems programming, we have implemented a suite of industry-standard network communication protocols in a completely type-safe extension of Standard ML. While the implementation has only recently become operational, we already observe acceptable communications throughput. We make careful use of the Standard ML modules system, with the core component of the implementation being a signature which is generic to all communications protocols. This generic protocol is then specialized for specific protocols, and these are implemented by functors parameterized by generic protocols. This leads naturally to a layered system structure and also provides an important and useful “mix-and-match” capability in composing protocols into complex networking systems.We have found the advanced features of Standard ML, in particular the modules system, static typing, and higher-order functions, to be extremely useful in building complex communications systems. The type compatibility of the various components of a system is guaranteed by the compiler. Furthermore, we find it significant that most of the information needed to understand the structure and interactions in our code can be obtained from a study of the signatures alone. Perhaps most important is that we have been able to use the expressive power of Standard ML modules to give concrete expression to previously ad hoc system-structuring concepts developed by other researchers in the field of network communications. For language designers and implementors, our experience has also pointed out specific areas for further work that may lead to advanced languages that are useful for systems programming.

The simple book : an introduction to internet management

Abstract: This text focuses on the technology used to manage large communications/network infrastructures based on TCP/IP known as "internets". In the last few years, the rapid growth of the number and size of these interconnected networks has made their management problematic. This edition has been updated to reflect the changes in internet management since 1990 and focuses on Version 2 of the Simple Network Management Protocol (SNMPv2) to which Rose has been the leading contributor. Topics covered include: overview of TCP/IP suite of protocols, managed objects, access policies, protocol operations and a complete working implementation of SNMP.

Network protocols for frequency-hop packet radios with decoder side information

Abstract: Reliable data distribution within spread-spectrum packet radio networks requires high performance from the network protocols. This paper describes research in forwarding and routing protocols that are designed specifically for slow-frequency hop (SFH) packet radio networks in which some of the radios are subjected to excessive interference. It is shown that information extracted from the decoder can be used to aid the network protocols. New metrics are introduced that use this information to give a quantitative assessment of the interference environment experienced by the receiver in an SFH radio. Forwarding protocols are developed that can react quickly to local sources of interference, and the metrics that are introduced permit the routing algorithm to react to changes in the interference conditions in the network. >

Network protocols for the cellular packet switch

Abstract: Future wireless information networks will employ dense grids of base stations to support a high user population. While small cells mitigate capacity problems, lengthen battery life, and improve signal quality, the frequent movement of users across cell boundaries imposes new burdens on network controllers. Previous work suggests that a cellular packet switch, based on distributed network control, can support high density personal communications. This paper proposes an allocation of control functions to elements of the cellular packet switch and specifies the flow of information within the switch. Message flows, defined for key procedures, form the foundation of a network layer protocol. Functionality is divided into the categories of call processing (set up and release), mobility management (location updates, handover, and path optimization), and radio resource management. Central office switches perform call processing. Mobility management and radio resource management are performed by interface units of the metropolitan area network at the heart of the cellular packet switch. This architecture delivers advanced services with minimal impact on central office switch software. It also relies on distributed, rather than centralized mobility management to provide prompt, accurate communications as users move about. >

IP on ATM local area networks

Abstract: ATM offers increased bandwidth and greater flexibility and manageability. However, ATM's success as a LAN technology depends on its ability to provide LAN-like services compatible with existing protocols and applications. The authors address the various issues in the design and implementation of the Internet Protocol (IP) in the evolving ATM LANs. >

Global control synthesis for an MIMD/FPGA machine

Abstract: Embedding a FPGA circular array into MIMD architectures allows one to synthesize fine-grain circuits for global computation support. These circuits operate concurrently with the distributed applications. They provide specific speed-up or additional services, such as communication protocols or global controllers. This article describes an architectural model for such controllers with practical examples implemented on the ArMen FPGA-multiprocessor. A multi-assignment language derived from the UNITY formalism is proposed, to implement the controllers with a high degree of parallelism. Their hardware synthesis principles are given. >

General purpose data communications protocol converter

Abstract: A data communications protocol converter for interfacing manufacturing process equipment with a host computer comprises a controller that converts the messages transmitted by the host computer and equipment into messages that meet the protocol of the receiving side A data acquisition system coupled between the controller and equipment provides a parallel interface to the process equipment and allows the converter to check for/activate logic signals from/to the process equipment A user interface circuit provides the controller with a user friendly interface that enables the user to set any message parameters and conversation scheme and to interactively communicate with each attached device and edit and re-transmit previously send messages A software support workstation coupled to the controller through a network provides capability for remote target machine access, software maintenance and configuration modification via the network

Method and apparatus for controlling device temperature during transmissions

Abstract: A communication device (200) supporting transmissions provides transmission related device temperature control The communication device (200) has a particular portion (244) subject to an increase in temperature resulting from the transmissions A message is provided for transmission by the communication device (200) which has a data communication protocol (224) governing message transmission Temperature control is effected by determining temperature information for the particular portion (244) of the communication device (200) and by modifying operation of the data communication protocol (224) based in part on the temperature information