The Effect of the Buffer Size in QoS for Multimedia and bursty Traffic: When an Upgrade Becomes a Downgrade

This work presents an analysis of the buffer features of an access router, especially the size, the impact on delay and the packet loss rate. In particular, we study how these features can affect the Quality of Service (QoS) of multimedia applications when generating traffic bursts in local networks. First, we show how in a typical SME (Small and Medium Enterprise) network in which several multimedia flows (VoIP, videoconferencing and video surveillance) share access, the upgrade of the bandwidth of the internal network may cause the appearance of a significant amount of packet loss caused by buffer overflow. Secondly, the study shows that the bursty nature of the traffic in some applications traffic (video surveillance) may impair their QoS and that of other services (VoIP and videoconferencing), especially when a certain number of bursts overlap. Various tests have been developed with the aim of characterizing the problems that may appear when network capacity is increased in these scenarios. In some cases, especially when applications generating bursty traffic are present, increasing the network speed may lead to a deterioration in the quality. It has been found that the cause of this quality degradation is buffer overflow, which depends on the bandwidth relationship between the access and the internal networks. Besides, it has been necessary to describe the packet loss distribution by means of a histogram since, although most of the communications present good QoS results, a few of them have worse outcomes. Finally, in order to complete the study we present the MOS results for VoIP calculated from the delay and packet loss rate

Can a Wi-Fi WLAN support a first person shooter?

In corporate and commercial environments, the deployment of a set of coordinated Wi-Fi APs is becoming a common solution to provide Internet coverage to moving users. In these scenarios, real-time services as online games can also be present. This paper presents a set of experiments developed in a test scenario where an end device moves between different APs while generating game traffic. A WLAN solution based on virtual APs is used, in order to make the handoffs transparent for Layer 3. The results show that it is possible to maintain an acceptable level of subjective quality during the handoff. At the same time, it is set clear that the fact of having a gamer in an AP could be taken into account by radio resource management algorithms, in order to provide a better quality

Small-Packet Flows in Software Defined Networks: Traffic Profile Optimization

This paper proposes a method for optimizing bandwidth usage in Software Defined Networks (SDNs) based on OpenFlow. Flows of small packets presenting a high overhead, as the ones generated by emerging services, can be identified by the SDN controller, in order to remove header fields that are common to any packet in the flow, only during their way through the SDN. At the same time, several packets can be multiplexed together in the same frame, thus reducing the overall number of frames. The method can be useful for providing QoS while the packets are traversing the SDN. Four kinds of small-packet traffic flows are considered (VoIP, UDP and TCP-based online games, and ACKs from TCP flows). Both IPv4 and IPv6 are studied, and significant bandwidth savings (up to 68 % for IPv4 and 78 % for IPv6) can be obtained for the considered kinds of traffic. The optimization method is also applied to different public Internet traffic traces, and significant reductions in terms of packets per second are achieved. Results show that bandwidth consumption is also reduced, especially in those traces where the percentage of small packets is high. Regarding the effect on QoS, the additional delay can be kept very low (below 1 millisecond) when the throughput is high, but it may become significant for low- throughput scenarios. Thus, a trade-off between bandwidth saving and additional delay appears in those cases

Rendimiento de Papa en Funcion de Epidemia por Tizon Tardio (Phytophthora infestans Mont. de Bary)

SEE ARTICLE FOR ABSTRACT IN SPANISH. English Abstract: In order to study the quantitative relationship between tuber yield of two potato (Solanum tuberosum L.) cultivars (‘Alpha’, susceptible, and ‘Zafiro’, moderately resistant to late blight), and severity of the pathogen in Toluca, México, managed by weekly foliar sprays of 0.575 kg i.a ha⁻¹, 1.15 kg i.a ha⁻¹, and without application of the fungicide Clorothalonil. There were statistical differences between cultivars and among treatments within each cultivar (P < 0.05). The relationship between yield and disease severity was described by linear regression models. Yield by commercial standards (classes 1, 2 and 3) depended on the accumulated severity 80 d after planting in cv. ‘Zafiro’, and at 58 d in ‘Alpha’ for class 1 and for total yield, at 65 d for class 2, and at 94 d for class 3. The determination coefficient varied between 54 and 78 % in the selected models for ‘Alpha’, while in ‘Zafiro’ the range was from 54 to 75 %. Yield loss was less in ‘Zafiro’, for its epiphytotics were less intense until start of tuberization. It is concluded that it is necessary to consider tuber iniciation as the critical point. The previous period is the most important to reduce losses. Hence, handling should focus on the delay of the epiphytotic iniciation (Yo) and intensity in this period (r[subscript k])

Functionalization of 3D scaffolds with protein-releasing biomaterials for intracellular delivery

[EN] Appropriate combinations of mechanical and biological stimuli are required to promote proper colonization of substrate materials in regenerative medicine. In this context, 3D scaffolds formed by compatible and biodegradable materials are under continuous development in an attempt to mimic the extracellular environment of mammalian cells. We have here explored how novel 3D porous scaffolds constructed by polylactic acid, polycaprolactone or chitosan can be decorated with bacterial inclusion bodies, submicron protein particles formed by releasable functional proteins. A simple dipping-based decoration method tested here specifically favors the penetration of the functional particles deeper than 300 &#956;m from the materials' surface. The functionalized surfaces support the intracellular delivery of biologically active proteins to up to more than 80% of the colonizing cells, a process that is slightly influenced by the chemical nature of the scaffold. The combination of 3D soft scaffolds and protein-based sustained release systems (Bioscaffolds) offers promise in the fabrication of bio-inspired hybrid matrices for multifactorial control of cell proliferation in tissue engineering under complex architectonic setting-ups.We are indebted to MINECO (BFU2010-17450), AGAUR (2009SGR-0108 and SGR2009-516), DGI (CTQ2010-19501) and CIBER de Bioingenieria, Biomateriales y Nanomedicina (CIBER-BBN, Spain) for funding our research on Inclusion bodies. CIBER-BBN is an initiative funded by the VI National R&D&i Plan 2008-2011, and Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. EGF is supported by the Programa Personal de Tecnico de Apoyo (Modalidad Infraestructuras cientifico-tecnologicas, MICINN). We also thank technical assistance from the Servei de Cultius Celulars, Produccio d'Anticossos i Citometria (SCAC) Laboratori de Luminescencia i Espectroscopia de Biomolecules (LLEB) and Servei de Microscopia, all at the Universitat Autonoma de Barcelona (UAB). We are also indebted to the Protein Production Platform (CIBER-BBN) for helpful technical assistance and for protein production and purification services (http://bbn.ciber-bbn.es/programas/plataformas/equipamiento). AV received an ICREA ACADEMIA award.Seras-Franzoso, J.; Steurer, C.; Roldan, M.; Vendrell, M.; Vidaurre-Agut, C.; Tarruella, A.; Saldana, L.... (2013). Functionalization of 3D scaffolds with protein-releasing biomaterials for intracellular delivery. Journal of Controlled Release. 171(1):63-72. https://doi.org/10.1016/j.jconrel.2013.06.034S6372171