63 research outputs found
Traffic regulation and control in the Manhattan street network
No full textThe Manhattan Street Network (MSN) with the Clockwork Routing scheme has been proposed as a particularly suitable candidate for use in optical networks. However, without any medium access control (MAC), the success of the MSN with Clockwork Routing in optical networks would be inhibited by the destination-release protocol, since the protocol provides no guarantee of fair access or bounded traffic delay requirements of access nodes. Hence, new traffic regulation schemes providing medium access control are required to ensure fair access between network nodes and satisfy stringent quality of service (QoS) requirements of applications. This paper introduces a new scheme for medium access that supports fairness between competing access nodes while limiting the delay in the network. A ring model based on the return-to-trail property of the MSN is used to realise the logical behaviour of the MSN and connection services are regulated using a distributed view of the network loading
Digital culture change
No full textDigital culture change is not a one-size-fits-all approach but rather a dynamic way to engage people and technology within a transformative framework that enhances stakeholder learning within higher education (HE) and organisational effectiveness. The Covid-19 pandemic underscored the need for flexible digital strategies, highlighting challenges related to digital inequity and the limitations of uniform transformation models. To drive a meaningful approach to change, senior leadership at the University for the Creative Arts (UCA) created a Digital Enabling Strategy to support decision-making, efficiency and stronger connections for delivery and academic success. Creating the strategy included commissioning institutional research guided by Jisc, a digital technology agency, and a strategic leadership review to replace previous Information Technology (IT) planning. This staged approach involved engaging the broader community of academics, students, professional and technical staff as stakeholders in change. Key principles that surfaced from the research included creating a more collaborative digital culture, strengthening existing technology structures, fostering leadership for change, and resisting regression to outdated models. The leadership review supported implementing an enabling three-level framework (centralised, distributed, and distinctive) that could tap into the institution’s unique value propositions for both campus and online experiences. It is encouraging that the institution has, through this process, been able to reassess core creative and business aspirations through a digital lens, identifying opportunities for innovation and mixed modes of participation, planning and engagement. By embracing an enabling strategy that set out to appraise and reset digital readiness in a small specialist higher education institution, distributed leadership can now build a digital culture that is inclusive yet adaptive and robust enough for competitive change
A multi-level TCP model with heterogeneous RTTs
No full textThis paper studies TCP performance focusing on the mean flow transfer delay and the average number of concurrent flows in the system. This is done for a dynamic population of users, rather than a static number of permanent flows. The modeling approach relies on using idealized processor sharing models as a starting point and modifying their properties to take into account some of TCPs non-ideal behavior. To this end, a model is derived that incorporates the effect of packet losses and RTTs on the goodput, as well as limited sending rates. Also, the unequal sharing of bandwidth between flows with different RTTs can be treated. The delay estimates take into account the initial slow start. Extensive ns2 simulations are used to verify the accuracy of the models. The references of this article are secured to subscribers
Potential and limitations of a teleteaching environment based on H.323 audio-visual communication systems
No full textThe effective support of teleteaching services requires the development of multimedia collaboration systems that are capable of providing real-time and high quality audio-visual communication among distributed instructors and students. In the absence of such specialised systems, technologies tailored to other services are being considered for teleteaching services as well. Such a technology is the H.323 audio-visual communication technology developed to support video communication over IF. Although teleteaching and videoconferencing have similar QoS requirements, teleteaching functional requirements are a superset of those of videoconferencing. In this paper, the suitability of H.323 technology and currently available products to support teleteaching services is investigated, based on experience gained during a related deployment at the University of Athens. (C) 2000 Elsevier Science B.V. All rights reserved
Distributed control of broadcast channels with acknowledgement feedback: Stability and performance
No full textMulti-objective Egress Router Selection Policies for Inter-domain Traffic with Bandwidth Guarantees
No full textThe next generation Internet is designed to accommodate flows that span across multiple domains with quality of service guarantees, in particular bandwidth. In this context, destinations for inter-domain traffic may be reachable through multiple egress routers within a domain. In this paper, we formulate a bandwidth guaranteed egress router selection problem. The objective is to, for each aggregated inter-domain traffic flow, select an egress router that satisfies the end-to-end bandwidth requirement while optimizing the network resource utilization by which we consider three objective functions: minimizing the total bandwidth consumption, improving intra-domain and inter-domain load balancing in the network. We propose a heuristic algorithm with five egress router selection policies to solve this problem. The evaluation of these egress router selection policies through simulation benefits ISPs by choosing the one that fits their target objectives.</p
Performance modelling and evaluation of firewall architectures for multimedia applications
No full textFirewalls are a well-established security mechanism to restrict the traffic exchanged between networks to a certain subset of users and applications. In order to cope with new application types like multimedia applications, new firewall architectures are necessary. The performance of these new architectures is a critical factor because Quality of Service (QoS) demands of multimedia applications have to be satisfied. We show how the performance of firewall architectures for multimedia applications can be determined. A model is presented which can be used to describe the performance of multimedia firewall architectures. This model can be used to dimension firewalls for usage with multimedia applications. In addition, we present the results of a lab experiment, used to evaluate the performance of a distributed firewall architecture and to validate the model
- …
