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The upper three OSI layers support the communication requirements of applications, while the lower four layers provide reliable transmission of data. This article describes the lower four layers. First, though, a brief overview of the layered model is presented including a summary of the upper three layers. Then a description of the lower three layers is followed by a discussion of data communication standards associated with specific layers. Architectural concepts are then explored: hierarchy and abstraction within the layers, levels of dialogue, internetworking, end‐to‐end communication, analysis of layer four, and a discussion of connection‐oriented, connectionless, and message‐oriented protocols and applications. The article concludes with a comparison of OSI and the de facto industry protocols, TCP/IP, which are currently used within the Internet.

The purpose of this paper is to analyze the environmental impact of distribution network design.

Typical distribution networks are identified and modeled through interviews with logistics companies in Korea. CO₂ emission is calculated for the distribution network models to evaluate the environmental impact of different network designs. In addition, economic and customer service performances are evaluated to provide realistic and balanced solutions to supply chain managers.

It is suggested that hybrid networks combining Hub-and-Spoke (HS) and Point-to-Point (PP) networks with a small number of sub-terminals are the most effective in both environmental and customer service aspects, whereas HS network is the most cost-effective.

The analysis in this study is based on certain assumptions, and hence full application of these results to specific cases is limited. The combination of PP network with HS network is suggested, forming a hybrid network, and CO₂ mitigation policies need to consider support schemes that can influence a firm’s decision making in relation to network design.

Little attention, however, has been paid to the environmental impact of distribution network design in the exiting literature. This study is a rare attempt at evaluating the environmental impact of distribution network design and may provide valuable implications to policy-makers and practitioners in logistics and manufacturing companies.

We investigate the relationship between airline network structure and airport congestion. More specifically, we study the ways in which airlines adjust capacity to delays depending on the network type they operate. We find some evidence suggesting that airlines operating hub-and-spoke structures react less to delays than airlines operating fully connected configurations. In particular, network airlines have incentives to keep frequency high even if this is at the expense of a greater congestion at their hub airports. We also show that airlines in slot-constrained airports seem to react to higher levels of congestion by using bigger aircraft at lower frequencies; thus, we conclude that conditioning the number of available slots on the levels of delays at the airport seems an effective measure that creates the right incentives for airlines to reduce the congestion they generate.

The purpose of this paper is to examine the efficacy of diversification-based learning (DBL) in expediting the performance of simulated annealing (SA) in hub location problems.

This study proposes a novel diversification-based learning simulated annealing (DBLSA) algorithm for solving p-hub median problems. It is executed on MATLAB 11.0. Experiments are conducted on CAB and AP data sets.

This study finds that in hub location models, DBLSA algorithm equipped with social learning operator outperforms the vanilla version of SA algorithm in terms of accuracy and convergence rates.

Hub location problems are relevant in aviation and telecommunication industry. This study proposes a novel application of a DBLSA algorithm to solve larger instances of hub location problems effectively in reasonable computational time.

To the best of the author’s knowledge, this is the first application of DBL in optimisation. By demonstrating its efficacy, this study steers research in the direction of learning mechanisms-based metaheuristic applications.

Strategic management and marketing.

Executive education; postgraduate; undergraduate.

By 2004, the low-cost carrier model had just recently been introduced to Southeast Asia. Airlines under this model quickly began taking market share. Singapore's first budget carrier, Valuair, finds itself in fierce competition between two rapidly emerging competitors in the second half of 2004. Valuair needs to expand in order to remain competitive. However, for this to happen the company needs additional access to capital. The CEO, Sim Kay Wee, has begun pitching to investors that his company is a smart low-risk investment. Is Sim right, given Valuair's competitive position and the market environment in which it operates?

Students will be able to apply strategic frameworks in order to develop an understanding of Valuair's market position and use this understanding to advice investment decisions.

Teaching notes are available for educators only. Please contact your library to gain login details or e-mail support@emeraldinsight.com to request teaching notes.

There is a strong academic and professional interest in the changing business model of LCCs in Europe. Recently, even Ryanair which is often considered a European LCC role model has departed from the point-to-point paradigm by offering transfers within its own network. We first provide a general overview of recent changes in the business model of airlines that used to be categorized as LCCs. We then add to existing studies on LCC network strategies toward building connections. While we distinguish different approaches to accommodate transfer passengers, our analysis focuses on mesh networks as an airline network topology other than hub-and-spoke networks to provide online connections. A schedule analysis of Ryanair’s direct and indirect services at its base at Porto airport exemplifies that a mesh network might allow LCCs to go beyond stand-alone operations to become network carriers without requiring a complete transition of the generic LCC business strategy.

Outlines the efforts of the State Library of North Carolina to provide access to the Internet and to electronic information resources for libraries in the state. The major challenge of finding a cost‐effective alternative to its statewide network, which was terminated by a 1993 legislative mandate, has led to opportunities to provide better services and resources by switching public libraries to point‐to‐point protocol (PPP) accounts and by migrating the State library’s information resources to an Internet‐accessible workstation.

The future scenario presented in this article offers a view of true facilities‐based competition in 2010. By this date, the continued investment in infrastructure development had ensured an increased rate in bandwidth provision and gradual extension of broadband service to the home across the USA, while end point technologies and conduits to the desktop proliferated. This scenario envisions two types of entrants: new forward‐thinking green‐field entrepreneurs and facilities owners who had previously not been involved in the communications provision (eg gas, water, electrical utilities). The main conclusion of the article is a recognition that competition requires open standards and interoperability. Facilities‐based competition requires clearly defined interface points where new competitors can connect customers. In this scenario two physical points of interconnection (at the curb and at the IXC/IAP) are envisioned. A policy prediction which is embedded in the scenario as an enabler of open interconnection is that economic necessity spurs democratic leaders to shorten the extension of copyright, and declare overly broad software patents void. An understated assumption is that political and economic leaders address the conflicts between information as property, as privacy (private information), and as speech (political information) in a timely and balanced manner. Luckily only the provision of interconnection is necessary for the scenario to be feasible. The well‐noted reality that the information industry will not approach its potential until issues of security, reliability and privacy are adequately addressed underlies this scenario. Some battles will remain in 2010: concepts of ownership and autonomy with respect to information adequate to the information revolution are being challenged by the genetics revolution.

Following deregulation, the airline industry has dramatically changed. In addition to numerous mergers and bankruptcies, the industry has also seen an influx of small, “low-cost” carriers who offer differentiated competition to the traditional legacy carriers. These low-cost carriers traditionally avoided the hub-and-spoke networks of legacy carriers, offering point-to-point service often on adjacent routes. However, events of the past 10–15 years, including the terrorist attacks of 9/11, rising fuel prices, and economic recessions, have led to a shift in the operations of these airlines. The legacy carriers have unbundled many of their services, most notably through baggage fees, seeking to improve efficiency. Low-cost carriers have expanded services into major airports and have shifted to more direct route level competition with the legacy carriers as they use their cost efficiency advantages to their advantage. In this chapter, we examine airport and route choice decision to serve by legacy and low-cost carriers over time. Our descriptive and econometric models point to convergence of operations in terms of the airports and routes that low-cost and legacy carriers serve, with the implication that the current competitive atmosphere improves efficiency as the distinctions between legacy and low-cost carriers have become less obvious.

The Hub and Spoke system (H&S), initially applied to the airline industry, is an innovative distribution approach which has proved to be successful especially in transportation systems dealing with several origins and destinations and with balanced good flows in both directions. This paper provides an overview of Hub and Spoke theory and proposes some possible improvements to this practice for freight transportation (trucking industry). In particular, the re allocation of transportation resources and the direct connection between pairs of nodes in the distribution network (short cut) have been applied in a case study involving the SKF European distribution network. All aspects of feasibility have been discussed and alternative solutions have been compared to the present configuration in terms of average lead times, goods flow, truck utilisation rate and transportation costs. The results confirm the effectiveness of the proposed interventions, mainly in terms of cost reduction and system flexibility.