An approach to verification and validation of a reliable multicasting protocol

<p>Bang & Olufsen A/S (B&O) is a renowned manufacturer of audio and video products. Their BeoLink (BeoLink) system distributes sound and vision throughout a home via a network. In this way, e.g., while doing the cooking in the kitchen, a person can remotely select and listen to a track from a CD, loaded in the CD player situated in the living room. To resolve conflicts, synchronisation between various actions is needed, and is indeed taken care of by appropiate communication protocols.</p><p>The purpose of the project described in this paper vas to test Coloured Petri Nets (CP-nets or CPN) as a way to improve B&O's methods for specification, validation, and verification of protocols. In the main experiment, an engineer from B&O used the Desing/CPN tool to build a simulations with a familiar graphical feedback, and to formally verify crucial properties using occurrence graphs (also known as state spaces and reachability graphs/trees). The latter activity demonstrated the applicability of occurrence graphs for timed CP-nets. Moreover, CPN was used to examine important aspects of a possible future revision of Beo-Link, and to check compatibility between the new and the old version. Based on the experiments reported in this paper, CPN has been included in the set of methods for specification, validation, and verification of future protocols at B&O.</p><p> </p><p><strong>Topics:</strong> System design oand verification using nets; higher-level net models; computer tools for nets; experience with using nets, case studies; application of nets to protocols and embedded systems.</p>

The specifications and performance of RAMP a reliable adaptive multicast protocol, are presented. Initially described in IETF RFC 1458 (1993), RAMP has been enhanced for use over an all-optical, circuit-switched, gigabit network under our ARPA-sponsored testbed for optical networking (TBONE) project. RAMP uses immediate, receiver-initiated, NAK-based, unicast error notification combined with originator based unicast retransmission. The approach is motivated by the loss characteristics of the TBONE network, where extremely low bit-error rates (10/sup -12/ or better) and the absence of any store-and-forward capabilities in the switches make packet losses almost entirely a result of receiver buffer overflows. As receiver losses are largely independent, use of unicast over multicast for NAKs and retransmission eliminates unnecessary receiver processing overhead associated with reading and discarding redundant packets. Use of immediate rather than delayed NAKs further improves performance by reducing both latency and the likelihood of buffer overflow. The effectiveness of this combined error control approach has been verified by other researchers, as well as through our own investigations. Interestingly, TBONE loss characteristics resemble those of switched virtual circuit ATM networks and packet-switched networks employing reservation services. As these networks provide quality of service guarantees in the switches, the likely source of packet loss is again due to receiver errors and buffer overflows. Hence, RAMP's design is also relevant for the next generation of packet switched networks.

We highlight the advantages of dynamic wavelength allocation and path rerouting in hybrid optical flow-switched data center networks compared with static electronic packet-switched data center networks. Current electronic packet-switched networks perform routing based on lookup tables and shortest path routing over high speed optical connections. However, load balancing and path rerouting are not designed in coordination with the optical data plane. In this work, we design and analyze the performance of load balancing and resource allocation in hybrid flow data center architectures. In the hybrid flow architecture, the transport layer and control plane are responsible for load balancing, congestion control and reliable data delivery in wavelength division multiplexed networks. The transport layer abstracts the underlying network and data link layers from user applications. Applications are unaware of whether flows are transmitted via the electronic data plane, optical data plane, or both, where the relevant metric for applications is transaction delay. We show that the data center architecture that minimizes delay in the presence of elephant flows and dynamic loads is the hybrid flow architecture with dynamic resource allocation.

Applications requiring the reliable distribution of data to groups of clients would be supported perfectly by reliable multicast protocols. In many cases, the problem of congestion control (a major research issue otherwise) does not exist because downlink bandwidth is owned or can be preallocated to a particular server by independent means, but the problems of insuring reliable data delivery to larcre groups, and adaptability to heterogeneous clients, still remain. These problems can be solved at once with the use of FEC techniques. In this paper we show the design of a Reliable Multicast data Distribution Protocol (RMDP) that we have built using these techniques, and discuss the implementation tradeoffs. Experimental results show that, albeit somewhat expensive, doing encoding/decoding in software is affordable for speeds in the Mbit/s range even on low-end PCs. Slower machines can still receive at high speed, thus optimizing network usage, by taking advantage of the fact that decoding needs not to be done in real time. Finally, our RMDP can work even without any feedback from the receivers, thus making it well suited to mobile/wireless systems.

As semiconductor device manufacturing processes are reducing feature sizes ever smaller, the manufacturing processes are becoming ever more complex. This complexity is having significant impacts on data communications between device design teams and manufacturing process teams. With current manufacturing process constraints, the constraints placed on a design team are difficult to conceptualize, communicate and enforce. This study describes a new type of process model, referred to as a focus sensitivity model that is capable of speeding up the model based analysis of design patterns for manufacturing robustness. The FSM is a difference model based on the photolithography process model. The FSM produces information about multiple process states in one pass. It also produces interpreted data, which removes the need to understand the performance of individual process states. Finally, FSM is capable of analyzing drawn patterns without optical proximity correction applied to determine pattern manufacturability

In the past, support for design has largely concentrated on specific design problems. The great challenge for many designers and design managers working on complex problems is to understand the connections between different aspects of design represented by different types of design models. Designs comprise connected components, and processes comprise linked tasks, but tasks are also connected to components. Each design project is embedded in the context of other projects. This paper discusses an on-going research project into design process improvement, which is centred on the use of process models and product models, designed to show important aspects of connectivity. These models are inevitably provisional due to the uncertain nature of design. The process model describes tasks and their linking parameters; the product model incorporates a probabilistic measure of the risk of change to one component spreading to others in terms of likelihood and impact. Planning and scheduling activities before the project begins can support the allocation of resources and indicate critical points in the process. Change prediction can aid change planning and decision making about possible design moves. Explicit models of connectivity enable designers to question each other’s assumptions and aid communication in design teams. However, the challenge lies in building sufficiently accurate models cost effectively.

Managing the Construction of the Alaska Highway Gas Pipeline Project

In a complex construction industry, such as that in the UK, the building process is predominantly that of assembling components made off-site. This requires that all the components are detailed, together with the methods of fixing, sufficiently early to ensure that the components are delivered to site at the right time. The effect of this has been to increase the number of drawings produced by the design team, for a typical project, to between 500 and 5000. Frequently this process fails because its complexity is not understood nor managed sensibly.

Co-designing your company’s future with your customers is imperative to ensuring continuing innovation. Make your lead customers part of your design team and take advantage of their inventions and insights as you work on your next-generation of products, services, process, and business models. In this self-assessment guide, you can see how far along your company is in taking advantage of customer co-design.

Data routing is an essential operation in working of a MANET. Many researchers have proposed novel routing protocols for MANET. Working of the routing protocols differs with each other. Each routing protocol follows a set of rules and has different characteristics. Various network simulators are popularly used to test performance and working of the novel routing protocols. However, there is a need to formally verify working of any novel routing protocol and to statistically validate experimental results collected from simulation. Our last research contribution proposed a novel trust-based opportunistic routing protocol, viz. ORPSN. This paper presents formal verification of ORPSN protocol using analytical proofs. The paper gives analytical proofs about optimality of the algorithm and loop freedom. The paper uses t-test to validate experimental results and observations. It compares performance of ORPSN and CORMAN opportunistic routing protocols in various test conditions. After statistical validation of experimental results, it is observed that performance of ORPSN is significantly better than CORMAN.

PurposeFinancial information about costs and return on investments are of key importance to strategic decision making but also in the context of process improvement or business engineering. The purpose of this paper is to propose a value‐oriented approach to business process modeling based on key concepts and metrics from operations and financial management, to aid decision making in process re‐design projects on the basis of process models.Design/methodology/approachThe paper suggests a theoretically founded extension to current process modeling approaches, and delineates a framework as well as methodical support to incorporate financial information into process re‐design. The paper uses two case studies to evaluate the suggested approach.FindingsBased on two case studies, the paper shows that the value‐oriented process modeling approach facilitates and improves managerial decision making in the context of process re‐design.Research limitations/implicationsThe paper presents design work and two case studies. More research is needed to more thoroughly evaluate the presented approach in a variety of real‐life process modeling settings.Practical implicationsThe paper shows how the approach enables decision makers to make investment decisions in process re‐design projects, and also how other decisions, for instance in the context of enterprise architecture design, can be facilitated.Originality/valueThis paper reports on an attempt to integrate financial considerations into the act of process modeling, in order to provide more comprehensive decision‐making support in process re‐design projects.

Computer simulation of patient flow has been used extensively to assess the impacts of changes in the management of surgical care. However, little research is available on the utility of existing modeling techniques. The purpose of this paper is to examine the capacity of Statecharts, a system of graphical specification, for constructing a discrete-event simulation model of the perioperative process. The Statecharts specification paradigm was originally developed for representing reactive systems by extending the formalism of finite-state machines through notions of hierarchy, parallelism, and event broadcasting. Hierarchy permits subordination between states so that one state may contain other states. Parallelism permits more than one state to be active at any given time. Broadcasting of events allows one state to detect changes in another state. In the context of the peri-operative process, hierarchy provides the means to describe steps within activities and to cluster related activities, parallelism provides the means to specify concurrent activities, and event broadcasting provides the means to trigger a series of actions in one activity according to transitions that occur in another activity. Combined with hierarchy and parallelism, event broadcasting offers a convenient way to describe the interaction of concurrent activities. We applied the Statecharts formalism to describe the progress of individual patients through surgical care as a series of asynchronous updates in patient records generated in reaction to events produced by parallel finite-state machines representing concurrent clinical and managerial activities. We conclude that Statecharts capture successfully the behavioral aspects of surgical care delivery by specifying permissible chronology of events, conditions, and actions.

The paper describes two conceptual designs of coal-burning AFBC demonstration heating plant planned for Atlantic Canada. The designs were prepared under contract by two separate teams of designers of which one drew upon British, the other upon American technology. The demonstration plant will consist of two boilers each generating 18 Mg/h of medium-pressure steam. The design fuel is high-volatile bituminous coal containing approximately 20% ash and 5% sulphur. Wood chips have been specified as a supplementary fuel to provide up to 30% of the heat input. Additional design criteria call for overbed feeding of 50 mm x 0 coal, special provisions to deal with wet and frozen coal, 4.5 to 1 turndown range, and emission limits on SO2, NO x and particulates. The two conceptual boiler designs differ substantially. One proposes four identical bed sections with forced circulation bed cooling and overbed feed of coal, limestone and wood chips by means of water-cooled screw conveyors. The other design proposes spreader-firing of the fuel onto two bed sections, one being a preferential bed having only peripheral cooling, the other being a secondary bed with in-bed as well as peripheral cooling. This design uses natural circulation throughout. Some data from pilot-scale tests with the design coal and limestone are also present. The same design teams are now preparing detailed designs and firm price proposals, which are to be submitted in January, 1981. One system will then be selected for construction, and commissioning is expected in 1982 or 1983.

Applying directional antennas in wireless ad hoc networks can theoretically achieve higher spatial multiplexing gain and, thus, higher network throughput. However, in practice, deafness, hidden-terminal, and exposed terminal problems are exaggerated with directional antennas, and they cause the degradation of the overall network performance. Although there are several random-access-based medium-access control (MAC) protocols being proposed in the literature for networks with directional antennas, the deafness, hidden-terminal, and exposed terminal problems have yet to be fully solved. In this paper, we present a new MAC protocol called the dual-sensing directional MAC (DSDMAC) protocol for wireless ad hoc networks with directional antennas. Different from existing protocols, the DSDMAC protocol relies on the dual-sensing strategy to identify deafness, resolve the hidden-terminal problem, and avoid unnecessary blocking. The integrity of the DSDMAC protocol is verified and validated using , which is a formal protocol verification and validation tool. We further develop an analytical framework to quantify the performance of the DSDMAC protocol and conduct extensive simulations, which verify the accuracy of the analysis. The protocol verification, analysis, and simulation results show the robustness and superior performance of the DSDMAC protocol, which can achieve a much higher network throughput and lower delay utilizing the spatial multiplexing gain of the directional antennas. The results presented in this paper show that the proposed DSDMAC protocol can substantially outperform the state-of-the-art protocols.

and Modeling such a process requires design decisions about the granularity of the ,process activities, about the degree of prescription defined within those activities, and about the policies that govern the triggering and termination of the activities and that define the nature of interaction and communication among the programmers evolving the system. Whatever choices are made for these issues, the resulting process is of necessity one with concurrent, independent, and asynchronous activities - that is, there will be multiple and different activities acting on the multiple and different states of the product. The critical issue is that of coordinating and synchronizing these independent activities. The general goals in Interact and Intermediate are to support goal-directed process modeling in such a way to maximize concurrency of activities and to minimize control of the human element in the process. To do this, I have separated the model specification from the enaction - that is, I have separated the modeling from the support and and in doing so have separated the (mostly) static aspects of process modeling from the (mostly) dynamic aspects of model enactment. Interact provides facilities for defining objects, policies, and activities: object definitions are used to model both the product and the project; policies definitions are used to model various facts and relationships about both the product and the project as well as to define synchronization (or interaction) abstractions; activity definitions are used to model the process activities that transform the product and project from one state to another. Activities are defined in terms of the activating policies, the defined goals and resulting obligations. Where desired, the process designer may bind the user to a particular implementation of the activity by supplying some structure to what is normally considered a primitive entity. Object declarations include type definitions, type instances, and object delinitions. Types and type instances enable the process designer to define the appropriate abstractions that are necessary for the model and to define the values for those abstractions. Objects have types and may assume the values defined for those types, For example, the model of software artifact serves as the coordinating object for the various activities that transform the product from one state to another; the model of the project defines the objects by which non-product related communications take place. Of paramount importance, however, are the policy definitions. They define the relationships among objects in several ways. First, policies may be primitive. These serve as base abstraclions which are asserted as results of activities. Second, policies may encapsulate logical expressions that relate (in various ways) base