Malleswara Talla

A novel congestion control in hybrid ATM/TDMA networks

A new congestion control scheme is analyzed for an ATM multiplexer node. This scheme is based on the leaky bucket and virtual leaky bucket techniques, and utilizes the interaction between the ATM and higher layers, in a hybrid asynchronous transfer mode/time division multiple access (ATM/TDMA) network. The transport users are assumed to be generic ATM sources, who modulate their end-to-end flow control parameters, i.e. protocol data unit size in case of video and voice users, and window size in case of data users, based on the congestion status. Simple analytical formulas are derived for congestion criteria, to represent the required bandwidth to support various classes of service, i.e. video, voice, data, etc. with their own performance requirements. An ATM multiplexer node buffer is analyzed using a modulated poisson process queuing model with bulk arrival and bulk service of cells. The ATM multiplexer node congestion performance criteria, i.e. the mean probabilities of ATM multiplexer node congestion, cell generation, cell discarding, buffer content and buffer overflow, are evaluated with and without the congestion control schemes.

RISK REDUCTION OF THE SUPPLY CHAIN THROUGH POOLING LOSSES IN CASE OF BANKRUPTCY OF SUPPLIERS USING THE BLACK-SCHOLES-MERTON PRICING MODEL

In recession times, slower demand, shrunk liquidity, and increasing pressure on cost can lead to bankruptcy of suppliers. The risks due to supplier bankruptcy include (a) losses due to supply chain disruption, (b) delayed or stopped finished goods shipments, (c) difficulty in finding cost-effective alternate suppliers and sourcing contracts, (d) emergency procurements, (e) loss of reputation and market share loss, etc. Bankruptcy models can be used to estimate the probability that a supplier may go bankruptcy, and a level of probability can be established that triggers the risks. This paper uses the Black-Scholes-Merton option pricing model for estimating the probability of bankruptcy of supplier by extracting and examining the riskiness in stock market price of supplier. The paper uses the pooling arrangements among companies that source from multiple suppliers as a way to reduce the risk due to supplier bankruptcy.

An Implementation of ITIL Guidelines for IT Support Process in a Service Organization

Service level management (SLM) is a challenge in a distributed systems environment because all processes should provide a consistent, reliable, and predictable service delivery. Early 1990s, most organizations established few service-level agreements (SLA) as the key performance indicators (KPI) but it was difficult to measure or monitor them in a distributed systems environment. The strength of Information Technology Infrastructure Library (ITIL) is the approach of integrating the SLM with the support processes at strategic, tactical, and operational levels. This paper focuses on implementing ITIL guidelines at an operational level for service desk, incidents, problems, and change management. The ITIL framework only provides guidelines, so a service organization needs to explore a methodology for evaluating existing service support processes and implementing ITIL guidelines for improvements. To this end, we investigate upon how to apply the ITIL framework for reengineering of IT service support process in an organization. The approach is actually implemented at a dentalcare service provider with ten dental clinics connected in Wide Area Network (WAN) and the data is collected into a central server in the main dental center. We first started with the process mapping, and then moved towards reengineering following ITIL guidelines, while collecting the results in key performance areas before and after the process reengineering. This paper used questionnaires, document reviews, archival records and observation techniques for collecting the data. The results demonstrated improvements in differing magnitudes. Some statistical analysis such as mean and variance together with t-value distribution and null hypothesis were also developed to determine the quality of results. The paper is cautious about the limited scope of audience and the questionnaire which may compromise the results; however, the approach is useful in obtaining significant improvements when a company invests in integrating ITIL guidelines in to service support processes.

ITIL-based IT service support process reengineering

The Information Technology Infrastructure Library ITIL supports best practices, reengineering activities and IT service support processes. ITIL framework only provides recommendations, and companies need to utilize this framework to improve their IT service support processes and establish best practices. This study provides a methodology on how to apply the ITIL framework for evaluating the IT service support processes, its reengineering and alignment to best practices, and subsequent integration into a decision support system framework. A case study approach was used to identify a set of Key Performance Indicators KPI which were monitored by a decision support system DSS for triggering on-going reengineering of IT service support processes. This paper focuses on the implementation of the ITIL guidelines at the operational level, improvement of the service desk, and incident, problem, change, release, and configuration management. It also presents the implementation of the ITIL guidelines at the tactical level for the improvement of the service level, capacity, IT service continuity, service availability, and security management. We conclude by providing recommendations for future research.

Global congestion control in hybrid ATM/TDMA networks

A new global congestion control scheme is analyzed for the ATM multiplexer node. This scheme is based on the leaky bucket and virtual leaky bucket techniques. It prioritizes transit traffic over local traffic. It ensures quality of service (QOS) to several classes of traffic (i.e., video, voice and data, etc.). A new global congestion control algorithm is designed using the congestion criteria of the adjacent nodes. Early warning cells are transmitted periodically to all adjacent nodes to communicate congestion criteria. The transport users are assumed to be generic ATM sources. The transport users modulate end-to-end flow control parameters, i.e., protocol data unit size in case of video and voice users, and window size in case of data users, based on global congestion status. Simple analytical formulas are derived for global congestion criteria, to represent the required bandwidth to support various traffic classes of service.

DSS Based IT Service Support Process Reengineering Using ITIL: A Case Study

The Information Technology Infrastructure Library (ITIL) is readily available for establishing the best practices, reengineering and improving the IT service support process. However, the ITIL framework only provides recommendations, and a company needs to explore a methodology for improving the IT service support process and adopting the best guidelines of ITIL framework. To this end, this chapter investigates upon how to apply the ITIL framework can be used for evaluating the current IT service support process and its reengineering. A set of Key Performance Indicators (KPI) were established which are monitored by a decision support system (DSS) for triggering on-going reengineering of IT service support process. A case study methodology is used for an effective reengineering of IT service support process. This chapter focuses on implementing the ITIL guidelines at an operational level, improving the service desk, incident management, problem management, change management, release management, and configuration. It also focuses on implementing the ITIL guidelines at a tactical level, improving the service level management, capacity management, IT service continuity management, service availability, and security management. The chapter describes a methodology and an experience in implementing process reengineering techniques following ITIL framework.

QOS based performance of selective repeat transport user in hybrid ATM/TDMA networks

The selective repeat (SR) transport user end-to-end throughput and delay characteristics are analyzed in a hybrid asynchronous transfer mode/time division multiple access (ATM/TDMA) network. The SR transport user is assumed with an underlying cell-level global congestion control in the ATM multiplexer node. The analysis is based on the interaction of packet level control with the queue management at the ATM cell level. The end-to-end transport users are assumed over an M-node virtual circuit (VC) to derive the throughput and delay using Norton equivalent queueing model. The transport service characteristic of the model is obtained from the end-to-end protocol efficiency. The ATM layer is assumed with a leaky bucket (LB), virtual leaky bucket (VLB), modified LB (mLB), or modified VLB (mVLB) congestion control. A global congestion control scheme prioritizes transit traffic over local traffic and ensures the quality of service (QOS) to several classes of traffic. Based on global congestion status, the transport users modulate their end-to-end flow control parameters, i.e., packet size for video and voice users and window size for data users. The probability of cell-loss at the ATM layer is reflected at the transport layer to derive the effective throughput and delay characteristics. The mVLB scheme consistently provided better end-to-end throughput and delay performance for SR transport user.

Throughput and delay performance of transport user in congestion controlled hybrid ATM/TDMA networks

The end-to-end throughput and delay performance characteristics are analyzed for a virtual circuit (VC) transport user in a hybrid asynchronous transfer mode/time division multiple access (ATM/TDMA) network. An automatic repeat request (ARQ) transport user is assumed with an underlying ATM cell-level global congestion control in an ATM multiplexer node. The analysis is based on the interaction of packet level control with the queue management at the ATM cell level. The transport user is assumed over M-node VC to analyze the throughput and delay using Norton equivalent queueing model. The transport layer service characteristic of the model is obtained from the end-to-end protocol efficiency of Go-Back-N (GBN) and selective repeat (SR) ARQ schemes. The ATM layer is assumed with a leaky bucket (LB), virtual leaky bucket (VLB), modified LB (mLB), or modified VLB (mVLB) congestion control scheme. A global congestion control scheme prioritizes transit traffic over local traffic, and ensures quality of service (QOS) to several classes of service. Based on the global congestion status, the transport users modulate their end-to-end flow control parameters, i.e., packet size in case of video and voice users, and window size in case of data users. The probability of cell-loss at the ATM layer is reflected at the transport layer to derive the effective throughput and delay characteristics. The mVLB scheme consistently provided better end-to-end throughput and delay performance for both GBN and SR transport users.

Reengineering of Legacy Systems into Supply Chain Systems: Traditional Data Oriented versus Process Oriented Approaches

The paper presents data oriented and process oriented models of legacy systems. It discusses the details of systems development and evolution models mainly aiming at an ongoing reengineering of legacy systems into supply chain systems. It proposes few strategies for reengineering of both data oriented model and process oriented models. The legacy systems often miss automatic interfaces to supply chain systems, so the article presents a strategy focusing on automatic update of data of the system. Likewise, the article also presents a strategy for process reengineering in order to integrate these legacy systems into supply chain systems. Finally, a legacy system is envisioned as a comprehensive mix of both data and process oriented, while proposing a gradual ongoing reengineering of both data structures and process methods.

Information Systems Reengineering for Modern Business Systems: ERP, Supply Chain and E-Commerce Management Solutions

Businesses must constantly adapt to a dynamically changing environment that requires choosing an adaptive and dynamic information architecture that has the flexibility to support both changes in the business environment and changes in technology. In general, information systems reengineering has the objective of extracting the contents, data structures, and flow of data and process contained within existing legacy systems in order to reconstitute them into a new form for subsequent implementation.Information Systems Reengineering for Modern Business Systems: ERP, Supply Chain and E-Commerce Management Solutions covers different techniques that could be used in industry in order to reengineer business processes and legacy systems into more flexible systems capable of supporting modern trends such as Enterprise Resource Planning (ERP), supply chain management systems and e-commerce. This reference book also covers other issues related to the reengineering of legacy systems, which include risk management and obsolescence management of requirements.