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München, Techn. Univ., Diss., 2004. / Erscheinungsjahr an der Haupttitelstelle: 2003. Computerdatei im Fernzugriff.

Berlin, Techn. Univ., Diss., 2004. / Computerdatei im Fernzugriff.

Hamburg, Techn. University, Diss., 2005.

München, Techn. University, Diss., 2004. / Erscheinungsjahr an der Haupttitelstelle: 2003.

In this work, we focus on congestion control mechanisms in Transmission Control Protocol (TCP) for emerging very-high bandwidth-delay product networks and suggest several congestion control schemes for parallel and single-flow TCP. Recently, several high-speed TCP proposals have been suggested to overcome the limited throughput achievable by single-flow TCP by modifying its congestion control mechanisms. In the meantime, users overcome the throughput limitations in high bandwidth-delay product networks by using multiple parallel TCP flows, without modifying TCP itself. However, the evident lack of fairness between the high-speed TCP proposals (or parallel TCP) and existing standard TCP has increasingly become an issue. In many scenarios where flows require high throughput, such as grid computing or content distribution networks, often multiple connections go to the same or nearby destinations and tend to share long portions of paths (and bottlenecks). In such cases benefits can be gained by sharing congestion information. To take advantage of this additional information, we first propose a collaborative congestion control scheme for parallel TCP flows. Although the use of parallel TCP flows is an easy and effective way for reliable high-speed data transfer, parallel TCP flows are inherently unfair with respect to single TCP flows. In this thesis we propose, implement, and evaluate a natural extension for aggregated aggressiveness control in parallel TCP flows. To improve the effectiveness of single TCP flows over high bandwidth-delay product networks without causing fairness problems, we suggest a new TCP congestion control scheme that effectively and fairly utilizes high bandwidth-delay product networks by adaptively controlling the flow’s aggressiveness according to network situations using a competition detection mechanism. We argue that competition detection is more appropriate than congestion detection or bandwidth estimation. We further extend the adaptive aggressiveness control mechanism and the competition detection mechanism from single flows to parallel flows. In this way we achieve adaptive aggregated aggressiveness control. Our evaluations show that the resulting implementation is effective and fair. As a result, we show that single or parallel TCP flows in end-hosts can achieve high performance over emerging high bandwidth-delay product networks without requiring special support from networks or modifications to receivers.

Tato prce popisuje nvrh a tvorbu testovac­ho prosted­ pro mÄen­ vkonnosti DNS server nad transportn­mi protokoly TCP a UDP. Obsahuje vsledky vkonnostn­ho mÄen­ t­ rznch implementac­ autoritativn­ch DNS server nad s­ovm provozem sloenm z rznch typ DNS dotaz zaslanch pomoc­ rznch s­ovch a transportn­ch protokol. Je provedeno srovnn­ vkonnosti tÄchto implementac­.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The usage of Internet is explosively growing. Satellite has become a choice solution breaking through the bandwidth bottleneck and the terrain limit. TCP, which is well suited to terrestrial networks, performs poorly on a satellite channel. The reduced efficiency and QoS(Quality of Service) mainly result from three characteristics of a satellite link: higher bit error rate, the high latency, asymmetry. For this issue, the paper presents connection-subsection network architecture, and brings forward S-TCP based on the architecture.

Ingeniero Civil Matemático / En la presente memoria se estudia la convergencia al equilibrio de los procesos estocásticos pertenecientes a la clase Incremento Aditivo Decremento Multiplicativo (AIMD, por sus siglas en inglés), enmarcada en el contexto de los procesos de Markov deterministas por pedazos, introducidos por M.H.A. Davis en 1984. En primer lugar se estudian los tiempos de entrada y salida de compactos de la forma [0,x_0], primero para el caso con intensidad constante y luego en el caso general. Luego, mediante la construcción de un coupling específico, se usan estos resultados para establecer la recurrencia de cierto compacto, el que depende los datos del problema. También se prueba que el tiempo de entrada a este compacto tiene momento exponencial finito de algún orden. Como consecuencia, se establece la existencia de una medida invariante y se obtiene una tasa explícita de convergencia exponencial al equilibrio. Por último, se aplica el Teorema probado al caso del proceso TCP y se compara con las tasas exhibidas por Bardet et. al en 2011.

Ngcezu, Sonwarile Arthur. Student no 0200932R. MSc Thesis. Physics. Faculty of Science. 2006. Supervisor: Prof D van der Merwe. / Purpose: A retrospective study was conducted to calculate biological objective functions [Tumor control probability (TCP) for the prostate and normal tissue complication probability (NTCP), in particular for the rectum] for patients treated at Johannesburg hospital during the years 2002 – 2003 for prostate cancer and to correlate these values with observed clinical outcome. Ultimately these results were used to evaluate the effects of dose escalation on tumor control and rectal complications following radiotherapy using conformal external beam radiotherapy. Methods and materials: To calculate the TCP and the NTCP use was made of BIOPLAN, a PC-based software. This software allows the user to evaluate a treatment plan from the point of view of the biological response of the irradiated tissue, providing at the same time flexibility in the use of models (Poisson Statistics for TCP and Lyman-Kutcher-Burman for NTCP) and parameters. The clinical analysis was based on reports from on treatment review and follow-up visits made by the patients periodically after the treatment. PSA was used as a measure of biochemical failure and correlated with calculated TCP. Also, reported complications were compared to NTCP values calculated by BIOPLAN. The follow-up data were about 2 months to 2.5 years old. Results: Complications reported after therapy were all less than grade 3 (RTOG) for the patients, which means only mild complications were reported. No patient reported having necrosis, perforation or a fistula for all the prognostic groups. The calculated average NTCP (mild complications) was 36.3 ± 33.3 % and it was 3.9 ± 3.6 % for severe complications. The calculated TCP had an average of 84.3 ± 7.4 % and no biochemical failure was detected on the follow-ups. As the total dose was elevated through 70-Gy, 72-Gy, 76-Gy, and 86-Gy (2 Gy equivalent), the average TCP increased through 76.2 ± 3.8 %, 77.7 ± 2.6 %, 81.5 ± 4 % and 92.5 ± 2.5 %, respectively. The TCP therefore increased about 22 % by increasing prescribed doses from 70 Gy to 86 Gy. The relation between rectal overlap volume and the NTCP was not obvious (scattered). Conclusions The model predictions gave a reasonable reflection of the reported clinical outcome. A more comprehensive study requires derivation and use of accurate model parameters, and more mature follow-up data.