Context: Nowadays one of the most beneficial business in IT area is web services with huge amount of users. The key ofsuccess in these type of services is flexibility in terms of providing same quality of services (QoS) and ability of fasttroubleshooting when number of users increase rapidly. To achieve these targets, evaluation of the user satisfaction is highlyessential. Moreover it is required to link user dissatisfaction to QoS parameters in terms of troubleshooting. Objectives: The main aim the research is to find an intelligent method for evaluation of the user satisfaction. The method isproposed to estimate quality-of-experience (QoE) without asking users to send their feed back. Connecting to this aim, thesecond target is finding the definition of function in equations of QoS=function(QoE). And finally, comparison of theimpact of QoS parameters on mobile application users and web site users is the last objective. Methods: For this research a web-server for video sharing propose is designed. The users can use it via web site or anAndroid mobile application. The three main QoS parameters (Packet-loss, delay and throughput) are changed gradually. Theusers are asked to score the mobile application and web site at the same time. In parallel the traffic of web-server is capturedand analyzed. Then based on variations in mean opinion scores (MOS) and also changes in TCP flags, the proper patternsfor each of the QoS parameters is provided. In this part the QoE is linked to transport layer. For the second objective, theQoE is directly linked to QoS. On the other words the graphs with QoE as horizontal axis and one of the QoS parameters asvertical axis are provided. And finally based on the gradient of these trends, the amount of impact of QoS parameters onmobile application users and web site users is compared. Results: Based on the results of the research, decrement in SYN and FIN flags and increment in ACK is an alarm for downgoing user satisfaction. In this situation, the problem is belongs to packet-loss. Increasing in the percentage of SYN is alsoa signal for user dissatisfaction. In this case, the problem is result of delay. And finally if the web-server problem is aboutthroughput then, SYN, FIN and ACK has up going trends. In all of the cases the rest of TCP flags has not clear up going ordecreasing trend.The correlation between QoS and QoE is formulated. The trends of MOS relative to QoS parameters for mobile phone andlaptop are very similar in case of packet-loss. For throughput the mobile phone users are a little more sensitive. The mostsignificant difference between the MOS values for mobile application and web site is belongs to delay. The increment indelay has really big negative effect on mobile application users. Conclusion: The final method for user satisfaction evaluation is based on the way of variations in the TCP flags. Among allthe flags, SYN, FIN and ACK passed the criteria to make the patterns. Moreover the method indicate the problem isbelongs to which of the QoS parameters. The correlation between QoE and QoS is formulated. And finally according tothese formulas, two separate web-servers for mobile application and web site is recommended.

Techn. Hochsch., Diss., 2000--Aachen.

Made available in DSpace on 2014-06-12T15:58:56Z (GMT). No. of bitstreams: 2 arquivo4784_1.pdf: 1130231 bytes, checksum: d522c1b7bacb28e4fac11275ecf335b5 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2004 / O GPRS (General Packet Radio Service) é uma extensão do GSM (Global System for Mobile communications) para a transmissão de dados baseada em pacotes e surgiu com o objetivo de atender à demanda por acesso sem fio à Internet. Por aproveitar toda a estrutura da rede GSM, tecnologia mais utilizada na área de comunicação celular, o GPRS vem sendo bastante adotado pelas operadoras celulares, inclusive no Brasil. Redes sem fio apresentam grandes taxas de perdas de pacotes devido a erros na sua interface aérea. Esta característica causa problemas de desempenho para o protocolo TCP (Transmission Control Protocol), que é utilizado pela maioria dos serviços de aplicação oferecidos atualmente na Internet. A perda de pacotes consiste em uma notificação implícita de congestionamento na rede para o transmissor TCP, que diminui sua taxa de transmissão. Em uma rede sem fio, como GPRS, o TCP não possui informação suficiente para distinguir entre perdas de pacote devido a erros na interface aérea e perdas causadas por descartes nas filas dos roteadores. Assim, é necessário que o seu comportamento sobre o GPRS seja cuidadosamente analisado. Alguns estudos têm sido realizados nos últimos anos sobre esse assunto, entretanto todos possuem um escopo bastante limitado. Este trabalho apresenta uma análise mais abrangente do desempenho do TCP sobre GPRS, baseada em simulação. Vários cenários distintos são avaliados, incluindo diferentes taxas de erros no meio físico de transmissão, tamanhos de pacotes e quantidades de usuários e de timeslots utilizados por usuário no sentido downlink. Além disso, um aspecto inovador é analisado: o uso de um modelo adaptativo para configurar dinamicamente os cenários de codificação (CS) do GPRS. Dentre as contribuições deste trabalho, destacam-se ainda os vários ajustes e acréscimos ao código do simulador utilizado visando tornar os resultados mais confiáveis. Palavras-chave: GPRS, TCP, análise de desempenho

In this paper, we present a comprehensive performance evaluation of TCP NewReno and TCP Vegas with and without ACK thinning for static multihop wireless IEEE 802.11 networks. Opposed to previous studies, we consider not only IEEE 802.11 operating in ad hoc mode with 2 Mbit/s bandwidth, but also with 5.5 Mbit/s and 11 Mbit/s bandwidths. Simulation results using ns-2 show that TCP Vegas achieves between 15% and 83% more goodput and between 57% and 99% fewer packet retransmissions than TCP NewReno. Considering fairness among multiple TCP flows, we show that using TCP Vegas results in between 21% and 95% fairness improvement compared to TCP NewReno. The reduced amount of packet retransmissions of TCP Vegas also leads to significant savings of energy consumption. The paper gives insight on the particular reasons for such performance advantages of TCP Vegas in comparison to TCP NewReno.

The aim of this work is to get familiar with operating system FreeRTOS and its usage in device design. It also explains usage of SW module LwIP (TCP/IP stack) and Free-MODBUS. Consequently is designed example device, simple operational panel. The panel communicates through ethernet interface using Modbus TCP protocol with connected PLCs on separate network. Its meet function of webserver, HID and also source of real time.

O aumento da popularidade da Internet e a criação de novos meios de transmissão estimulam um explosivo crescimento da taxa de transmissão de dados sobre a Internet. Assim, o processamento TCP/IP baseado em software torna-se um gargalo por não processar os pacotes na velocidade das linhas de transmissão, em especial os pacotes da camada de transporte. Conseqüentemente, surge a necessidade de implementação em hardware do processamento TCP/IP, o que traria vantagens como aceleração do processamento do fluxo de dados. Neste sentido, este trabalho apresenta a arquitetura do iNetCore, descrita em VHDL, para processamento dos protocolos das camadas de rede e transporte em hardware. Duas implementações desta arquitetura foram elaboradas, buscando explorar o espaço de projeto e analisar os resultados obtidos na síntese para a tecnologia ASIC e FPGA, e o desempenho no processamento de pacotes. Uma arquitetura HW/SW contendo o iNetCore foi prototipada sobre a placa Virtex- II Pro Development System. Em conjunto com essa arquitetura, foi implementada uma interface de comunicação com o barramento OPB, tornando possível a implementação de softwares da camada de aplicação que queiram usar a pilha TCP/IP desenvolvida em hardware. Por fim, foram efetuados experimentos para avaliar o desempenho da arquitetura HW/SW no processamento de segmentos TCP. A arquitetura HW/SW em conjunto com o iNetCore alcançou um throughput de até 1,45 Gbps, possibilitando o uso da arquitetura para processamento de pacotes TCP/IP na plenitude de banda disponíveis em redes gigabit. / The advent of new transmission lines stimulates an explosive increase of the Internet data-transmission rate. Thus, the TCP/IP processing based on software became a bottleneck, because it cannot reach the transmission line speed required, specially in the transmission of transport layer packets. This limitation brings the necessity of implementation of the TCP/IP processing in hardware, what it would bring advantages in the acceleration of data flow processing. In this way, this work presents the iNetCore architecture, described in VHDL, able to process the transport and network layers protocols in hardware. Two implementations of this architecture were implemented. The objective is to explore the design space and to analyze the results in ASIC and FPGA technology synthesis. Also, a simulation environment was built to analyze the performance in the packets computation. A HW/SW architecture containing the iNetcore was prototyped on Virtex-II Pro Development System board. In conjunction with this architecture, it was implemented a communication interface with OPB bus, which makes possible the development of application layer softwares that may use the hardware TCP/IP stack developed. Finally, experiments were realized in order to evaluate the HW/SW architecture performance in the TCP segments processing. The HW/SW architecture together with the iNetCore reached a throughput of about 1.45 Gbps in the TCP/IP packets processing. It proves its potential to use available bandwidth in gigabit networks.

The forwarding delay and throughput of a proxy server play significant role in the overall network performance. It is widely known that the forwarding delay of proxy¡¦s application layer is much larger than that of lower layers. This is because for a general purpose operating system, the receiving or sending data in application layer needs to move data through the TCP/IP stack and also cross the user/kernel protection boundaries. TCP Splice can forward data directly in TCP layer without going up to the application layer. This can be achieved by modifying the packet headers of one TCP connection from the original server to the proxy so that the TCP connection can be seamlessly connected to another TCP connection from the proxy to the client. To maintain the caching ability of proxy, TCP Tap can duplicate packets before they are forwarded by TCP Splice. The duplicated packets are copied into a tap buffer, so the application layer can read data from the tap buffer. We fully utilize the original TCP receive queue as the tap buffer and allow application layer to read data as usual. We chose Linux as the platform for experiment. The TCP Splice and Tap are implemented as Linux modules. Finally, we develop an HTTP proxy to test and verify our implementation. It is shown that the performance of proxy in terms of lower forwarding delay, higher throughput, and increased CPU utilization, can be improved significantly.

Η δομή της εργασίας χωρίζεται σε πέντε μέρη. Στο πρώτο κεφάλαιο γίνεται μια παρουσίαση των δικτύων υπολογιστών και του μοντέλου αναφοράς OSI που χρησιμοποιείται για την περιγραφή τους. Στο δεύτερο κεφάλαιο παρουσιάζεται το πρωτόκολλο επικοινωνίας TCP και αναλύονται οι μηχανισμοί και οι υπηρεσίες που παρέχει. Στο τρίτο κεφάλαιο μελετάται η υλοποίηση του πρωτοκόλλου TCP στον πυρήνα του λειτουργικού συστήματος Linux και προτείνονται μέθοδοι εκτενούς παρακολούθησης της λειτουργίας του σε πραγματικό χρόνο χρησιμοποιώντας τις δυνατότητες που παρέχει ο πυρήνας του λειτουργικού συστήματος. Το τέταρτο κεφάλαιο περιλαμβάνει την πειραματική διαδικασία. Μέσα από συγκεκριμένα σενάρια που υλοποιούνται σε ένα οικιακό τοπικό δίκτυο, εξετάζεται και αξιολογείται η λειτουργία πέντε διαφορετικών αλγορίθμων συμφόρησης του πρωτοκόλλου TCP, οι οποίοι αποτελούν κομμάτι του πυρήνα του λειτουργικού συστήματος. Τέλος στο πέμπτο κεφάλαιο παίρνοντας σαν αφορμή τα αποτελέσματα της συγκριτικής αξιολόγησης των πέντε αλγορίθμων προτείνονται μικρές τροποποιήσεις στον κώδικα του ενός από αυτούς με στόχο την βελτίωση της λειτουργίας του στο συγκεκριμένο τοπικό δίκτυο. / Η δομή της εργασίας χωρίζεται σε πέντε μέρη. Στο πρώτο κεφάλαιο γίνεται μια παρουσίαση των δικτύων υπολογιστών και του μοντέλου αναφοράς OSI που χρησιμοποιείται για την περιγραφή τους. Στο δεύτερο κεφάλαιο παρουσιάζεται το πρωτόκολλο επικοινωνίας TCP και αναλύονται οι μηχανισμοί και οι υπηρεσίες που παρέχει. Στο τρίτο κεφάλαιο μελετάται η υλοποίηση του πρωτοκόλλου TCP στον πυρήνα του λειτουργικού συστήματος Linux και προτείνονται μέθοδοι εκτενούς παρακολούθησης της λειτουργίας του σε πραγματικό χρόνο χρησιμοποιώντας τις δυνατότητες που παρέχει ο πυρήνας του λειτουργικού συστήματος. Το τέταρτο κεφάλαιο περιλαμβάνει την πειραματική διαδικασία. Μέσα από συγκεκριμένα σενάρια που υλοποιούνται σε ένα οικιακό τοπικό δίκτυο, εξετάζεται και αξιολογείται η λειτουργία πέντε διαφορετικών αλγορίθμων συμφόρησης του πρωτοκόλλου TCP, οι οποίοι αποτελούν κομμάτι του πυρήνα του λειτουργικού συστήματος. Τέλος στο πέμπτο κεφάλαιο παίρνοντας σαν αφορμή τα αποτελέσματα της συγκριτικής αξιολόγησης των πέντε αλγορίθμων προτείνονται μικρές τροποποιήσεις στον κώδικα του ενός από αυτούς με στόχο την βελτίωση της λειτουργίας του στο συγκεκριμένο τοπικό δίκτυο.

Darbe tiriamas didelių failų perdavimo efektyvumas kliento-serverio sistemoje. Apibūdinami TCP ir UDP transportavimo lygmens protokolai, skirtingi kompiuterių sujungimo tipai – naudojant tarpinį įrenginį ir be jo. Eksperimentiniam tyrimui sukurta programinė įranga leidžianti siųsti failus: * Kliento-serverio sistema veikianti TCP protokolo pagrindu; * Kliento-serverio sistema veikianti UDP protokolo pagrindu. Eksperimentiškai nustatoma didelių failų perdavimo efektyvumo priklausomybė nuo kompiuterių sujungimo tipo, transporto lygmens protokolų bei tų protokolų parametrų. / Efficiency of sending big files over networked client-server system is examined at this work. TCP and UDP transport layer protocols and different computer connection types, using intermediate device and without it, are overviewed. Software for experimental research was created: * Client-server system using TCP protocol; * Client-server system using UDP protocol. Performing experiments dependence of computer connection type, transport layer protocols ad parameter of those protocols were determined.

Transmission Control Protocol (TCP) is the dominant transport protocol in the Internet and supports many of the most popular Internet applications, such as the World Wide Web (WWW), file transfer and e-mail. TCP congestion control algorithms dynamically learn the network bandwidth and delay characteristics of a network and adapt its performance to changes in traffic so as to avoid network collapse. TCP is designed to perform well in traditional wireline networks with the assumptions that packet losses are mainly due to network congestion and random bit error rate (BER) is negligible. However, networks with wireless links suffer from significant packet losses due to random bit errors and handoffs. Hence TCP performs poorly in networks with wireless links because it treats any packet loss in the network to be a result of network congestion and slows down its transmission rate, or even cause the TCP sender to experience unnecessary timeouts, further reducing its performance. The development of advance wireless networks, such as WiFi, UMTS and WiMAX, make it necessary to find ways to improve TCP's efficiency and resource utilization, as well as improve the user's experience and reduce latency times. In order to find effective solutions to this effect, packet losses across wireless links should be distinguished from congestion related packet losses. In this thesis, we concentrate on two main strategies for enabling the TCP congestion control mechanism to determine the cause for a packet loss. One is a proxy-based mechanism that monitors the radio network interface and sends radio network feedback (RNF) to the TCP sender with the status of the wireless link. The other one is an end-to-end mechanism, in which the packet error pattern is used as the system metric to fine-tune the congestion control mechanism. It also presents an analytical model of TCP with enhanced recovery mechanism for wireless environments. In a proxy-based mechanism, TCP sender is explicitly informed of any effects caused by wireless links. However, the implementation technique is network dependent. We have proposed and developed three proxy-based schemes; the radio network feedback (RNF) scheme over an 802.11 WLAN network, the radio network controller (RNC) feedback over a UMTS network and a wireless enhancement proxy (WENP) over both the 802.11 WLAN and UMTS networks. The RNF scheme is introduced at the 802.11 WLAN base station that monitors the TCP packet flows over the wireless links, detects wireless packet losses and provides feedback to the TCP sender using one of the TCP header reserved control bits, called RNF flag. TCP Reno is modified to utilize the radio network feedback to distinguish the losses due to wireless effects form the congestion and fine-tuned to perform wireless enhanced fast retransmit and fast recovery mechanisms. The RNF scheme is implemented using the OPNET tool, and the simulation results show that the TCP performance is significantly improved. The RNC feedback mechanism, similar to the RNF scheme, is developed and implemented in a UMTS network. The GPRS Tunneling Protocol (GTP) layer of the UMTS Radio Network Control (RNC) protocol stack was modified to detect and notify the TCP sender of the wireless packet losses, which is the main difference between the RNF and RNC mechanisms. The simulation results shows that the RNC feedback mechanism significantly improves the TCP performance compared to that of standard TCP over UMTS. The wireless enhancement proxy (WENP) is developed to minimize spurious TCP timeouts over wireless networks and implemented in both 802.11 WLAN and UMTS networks. WENP extends the proposed RNF and RNC feedback mechanisms to detect both wireless packet losses and large delays across the wireless link, and to notify the TCP sender of these events with the aid of two reserved bits in the TCP header. TCP Reno is further modified to utilize the WENP feedback to distinguish both wireless packet losses from congestion losses and spurious timeouts from normal timeouts. It is also fine-tuned to perform both the wireless enhanced fast retransmit and fast recovery mechanism and the timeout mechanism. The simulation results demonstrate that the proposed scheme markedly improves the TCP performance compared to that of standard WLAN and UMTS implementations. An end-to-end early packet loss recovery (EPLR) mechanism that modifies the TCP Reno fast retransmit algorithm to detect packet losses early and to speed up the packet recovery process to reduce the number of TCP timeouts over networks with heavy packet losses, such as wireless networks is also presented. TCP Reno with EPLR scheme is implemented in a UMTS network and its performance is compared with that of TCP Reno and New Reno. Simulation results shows that Reno with EPLR improves the TCP performance and application response time significantly compared to that of both Reno and New Reno by reducing the TCP timeouts, which is the main cause of degradation of the TCP performance in a wireless environment. Finally, we develop an analytical TCP throughput model with enhanced TCP Reno fast retransmit algorithm to avoid timeouts. The model captures the TCP fast retransmit mechanism and expresses the steady state congestion window and throughput as a function of network utilization factor, round trip time (RTT) and loss rate. Another new feature added to the model is dynamic adjustment of the congestion window size depending on the packet drop rates. This speeds up the packet recovery process and reduces the number of TCP timeouts over networks with heavy packet losses. The proposed model is implemented over a UMTS network and its performance is compared with that of TCP Reno. Simulation results show that the proposed model reduces the TCP timeouts and improves the TCP performance compared to that of TCP Reno. It is also found that the model provides a very good match to the steady-state congestion window behavior.