Efficient Configuration of Protocol Software for Multiprocessors

Efficient implementation of communication software is of crucial importance for high-speed networks. One way to improve the runtime performance of protocol implementations in the network nodes is the use of parallelism. Formal description techniques like Estelle improve the specification process in many respects and allow for semiautomatic code generation. Therefore, they are now widely accepted. We present a code generator for Estelle that compiles and automatically configures protocol software for a multiprocessor. Software modules are distributed over the available processors and executed concurrently. We report performance results on a KSR1 with 28 available processors under the OSF/1 operating system

Applying Formal Methods to Networking: Theory, Techniques and Applications

Despite its great importance, modern network infrastructure is remarkable for the lack of rigor in its engineering. The Internet which began as a research experiment was never designed to handle the users and applications it hosts today. The lack of formalization of the Internet architecture meant limited abstractions and modularity, especially for the control and management planes, thus requiring for every new need a new protocol built from scratch. This led to an unwieldy ossified Internet architecture resistant to any attempts at formal verification, and an Internet culture where expediency and pragmatism are favored over formal correctness. Fortunately, recent work in the space of clean slate Internet design---especially, the software defined networking (SDN) paradigm---offers the Internet community another chance to develop the right kind of architecture and abstractions. This has also led to a great resurgence in interest of applying formal methods to specification, verification, and synthesis of networking protocols and applications. In this paper, we present a self-contained tutorial of the formidable amount of work that has been done in formal methods, and present a survey of its applications to networking.Comment: 30 pages, submitted to IEEE Communications Surveys and Tutorial

Hardware/Software Co-design of Communication Protocols

An important aspect in providing high performance distributed systems such as multimedia systems is the combined use of hardware and software in the end systems. System design techniques should allow hardware/software co-design to integrate both means of implementation. In this paper, we show how the standardized formal language Estelle can be used to facilitate co-design. The system will first be designed in Estelle. At the point in time of final decision on which parts to implement in software and which in hardware, the original specification will be split into several partial specifications. The software parts are translated into C code, while the hardware parts are translated into VHDL code for further analysis and development. We present a tool environment which supports the protocol developer in the design and implementation process. A simple Video-on-Demand example shows the usefulness of the tool environment

Leistungsbewertung automatisch generierter Protokollimplementierungen mit Estelle

Formale Beschreibungstechniken (FDTs) erlauben durch ihre formale Syntax und Semantik eine präzise Systembeschreibung und sind Grundlage für die formale Verifikation. Bei der Implementierung von Systemen wird jedoch nach wie vor von Hand implementiert, selbst wenn ausgereifte Werkzeuge zur automatischen Generierung von Kode direkt aus der formalen Spezifikation existieren. Die Ursache dafür liegt in dem Ruf dieser Werkzeuge, Kode mit extrem geringer Leistungsfähigkeit zu erzeugen. Es gibt jedoch kaum quantitative Leistungsvergleiche zwischen manuell und automatisch generierten Implementierungen, die dieses Vorurteil stützen oder widerlegen könnten. In diesem Beitrag wird ein solcher Leistungsvergleich anhand des Hochleistungsprotokolls XTP und der FDT Estelle vorgestellt. Er liefert eine Bestandsaufnahme des momentanen Entwicklungsstandes bei der automatischen Generierung von Kode aus Estelle-Spezifikationen im direkten Vergleich zu gut optimierten Handimplementierungen. Es zeigt sich, daß in dem betrachteten Fall eines komplexen Protokolls die Handimplementierung zwar merklich leistungsstärker ist. Dieser Leistungsvorteil wird jedoch durch einen sehr hohen Implementierungsaufwand sowie die Schwierigkeit, die Korrektheit bzgl. der Spezifikation sicherzustellen, erkauft. Im einzelnen Anwendungsfall kann es daher trotz der Leistungseinbußen durchaus vorteilhaft sein, automatisch Kode zu erzeugen, zumal in der Bestandsaufnahme festgestellt wurde, daß automatisch generierte Implementierungen z.T. besser abschneiden als erwartet. Zudem besteht - anders als bei der bereits umfassend optimierten Handimplementierung - noch ein erhebliches ungenutztes Potential zur Leistungsverbesserung der automatisch generierten Implementierung

Hardware/Software Codesign

The current state of the art technology in integrated circuits allows the incorporation of multiple processor cores and memory arrays, in addition to application specific hardware, on a single substrate. As silicon technology has become more advanced, allowing the implementation of more complex designs, systems have begun to incorporate considerable amounts of embedded software [3]. Thus it becomes increasingly necessary for the system designers to have knowledge on both hardware and software to make efficient design tradeoffs. This is where hardware/software codesign comes into existence

Addressing performance requirements in the FDT-based design of distributed systems

The development of distributed systems is generally regarded as a complex and costly task, and for this reason formal description techniques such as LOTOS and ESTELLE (both standardized by the ISO) are increasingly used in this process. Our experience is that LOTOS can be exploited at many stages on the design trajectory, from requirements specification to implementation, but that the language elements do not allow direct formalization of performance requirements. To avoid duplication of effort by using two formalisms with distinct approaches, we propose a design method that incorporates performance constraints in an heuristic but effective manner

Specifying agent interaction protocols with UML activity diagrams

In this paper, we will demonstrate how the Unified Modeling Language (UML) can be used to describe agent interaction protocols. The approach that is presented in this paper does not propose major enhancements or completely new diagrams but instead it relies on existing UML elements that are part of the standard. This conformity with the base UML is a major advantage of the idea as it prevents a diversification of the UML into different potentially incompatible dialects. The practical use of the method is demonstrated in the specification of a realistic agent interaction protocol

Real-Time Estelle

Estelle is one of the standardized Formal Description Techniques for the specification of communication protocols and distributed systems. Unfortunately, Estelle is not capable to express real-time requirements or characteristics of services or protocols which is especially important in the context of distributed multimedia systems. In this paper, we introduce an extension to Estelle called Real-Time Estelle that allows to describe real-time systems. We introduce the syntax of the new language and propose both an operational and a descriptive semantics. Examples show the usefulness of the approach. We also discuss ways to implement Real-Time Estelle specifications

Estelle-based test generation tool

A test design tool for functional analysis and test derivation of protocols formally specified using an extended finitestate machine model is presented. The formal description language supported is Estelle. The tool's main components include a compiler, a normalizer, a multiple module transition tour generator and several interactive programs. The tool is based on a static analysis of Estelle called normalization, which is explained in detail with various examples. The normalized specification facilitates graphical displays of the control and data flow in the specification by the interactive tools. Next discussed is test generation, which is based on verifying the control and data flow. First the data flow graph must be decomposed into blocks where each block represents the data flow in a protocol function. From the control graph the tool generates transition tours, and then test sequences are derived from the transition tour to test each function. The performance of the tool on various applications is also included. © 1991

On the Suitability of Estelle for Multimedia Systems

Formal Description Techniques have been widely used for the specification of traditional networked applications. They have not been applied to the specification of new applications such as multimedia systems yet. In this paper, we examine the FDT Estelle with respect to its suitability for multimedia system specification and automatic derivation of efficient implementations. We show that it is possible to specify certain aspects of multimedia systems, but that Estelle is not sufficient for others. The derived implementations often perform badly. We show the reasons and propose to use a slightly modified Estelle syntax and semantics to solve the problems. The implemented solution was tested successfully