This thesis deals with the transmission of information over the Ethernet network. In this work a suitable microcontroller and a communication module were selected. The Module provides data transfer from Ethernet to SPI bus. Furthermore an optimal digital temperature sensor DS1820 was chosen. Theoretically it describes the model TCP / IP and the Ethernet type network . In this thesis a block circuit diagram is created, further an electrical wiring diagram and a printed circuit board were constructed. In the programming environment BascomAVR a program is compiled, which is used to transfer information from the microcontroller via Ethernet to a website.

This thesis solves possibility of using entropy for anomaly detection in data communication and especially for security attacks. The main advantage of using entropy is ability to identify unknown attacks because entropy detects changes in network traffic but not the content as existing methods. In this work was tested the suitability of different models entropy (Shannon, Renyi, Tsallis). Also been tested the effect of Renyi and Tsallis parameter on resulting entropy. From the resulting values, I found that all tested entropy achieve good result in the identification of anomalies in network traffic.

In this paper, we introduce a clean-slate architecture for improving the delivery of data packets in IEEE 802.11 wireless mesh networks. Opposed to the rigid TCP/IP layer architecture which exhibits serious deficiencies in such networks, we propose a unitary layer approach that combines both routing and transport functionalities in a single layer. The new Mesh Transmission Layer (MTL) incorporates cross-interacting routing and transport modules for a reliable data delivery based on the loss probabilities of wireless links. Due to the significant drawbacks of standard TCP over IEEE 802.11, we particularly focus on the transport module, proposing a pure rate-based approach for transmitting data packets according to the current contention in the network. By considering the IEEE 802.11 spatial reuse constraint and employing a novel acknowledgment scheme, the new transport module improves both goodput and fairness in wireless mesh networks. In a comparative performance study, we show that MTL achieves up to 48% more goodput and up to 100% less packet drops than TCP/IP, while maintaining excellent fairness results.

We introduce an adaptive pacing scheme to overcome the drawbacks of TCP in wireless mesh networks with Internet connectivity. The pacing scheme is implemented at the wireless TCP sender as well as at the mesh gateway, and reacts according to the direction of TCP flows running across the wireless network and the Internet. TCP packets are transmitted rate-based within the TCP congestion window according to the current out-of-interference delay and the coefficient of variation of recently measured round-trip times. Opposed to the majority of previous work which builds on simulations, we implement a Linux prototype of our approach and evaluate its feasibility in a real 20-node mesh testbed. In an experimental performance study, we compare the goodput and fairness of our approach against the widely deployed TCP NewReno. Experiments show that our approach, which we denote as Mesh Adaptive Pacing (MAP), can achieve up to 150% more goodput than TCP NewReno and significantly improves fairness between competing flows. MAP is incrementally deployable since it is TCP-compatible, does not require cross-layer information from intermediate nodes along the path, and requires no modifications in the wired domain.

Theme of the Master's thesis is issue of backup power units and its attributes. There is also complete proposal of UPS power unit which can be used to control and monitor backup batteries. Power supply is fully controlled via Ethernet interface using TCI/IP protocol. The other chapter describes complete development of TCI/IP GSM unit which can be used for communication interface between GSM and Ethernet protocol. UPS and GSM modules are developed in details. The Master.s thesis includes all needed information for HW unit development and also for controlling software as well. Universal solution of the modules allows number possibilities of further development.

Multi-transport devices are becoming more common, but sophisticated software is needed to fully realize the advantages of these devices. In this paper, we examine the performance of dynamic transport switching, which selects the best available transport for communication between two devices. We simulate transport switching within the Quality of Transport (QoT) architecture and show that it can effectively mitigate the effects of congestion and interference for connections between two multi-transport devices. We then evaluate dynamic transport switching overhead to characterize its effect on application throughput. Based on these insights, we identify several limitations of the QoT architecture and present solutions to improve performance.

When used in a wireless mesh network, TCP has shortcomings in the areas of throughput and fairness among traffic flows. Several methods have been proposed to deal with TCP's weakness in a wireless mesh, but most have been evaluated with simulations rather than experimentally. We evaluate several major enhancements to TCP – pacing, conservative windows, and delayed ACKs – to determine whether they improve performance or fairness in a mesh network operating in the BYU Computer Science building. We also draw conclusions about the effectiveness of wireless network simulators based on the accuracy of reported simulation results.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Broadband wireless access (BWA) is a promising emerging technology. In the past, most BWA systems were based on proprietary implementations. The Institute of Electrical and Electronics Engineers (IEEE) 802.16 task group recently standardized the physical (PHY) and medium-access control (MAC) layers for BWA systems. To operate in a wide range of physical channel conditions, the standard defines a robust and flexible PHY. A wide range of modulation and coding schemes are defined. While the standard provides a framework for implementing link adaptation, it does not define how exactly adaptation algorithms should be developed. This thesis develops a link adaptation algorithm for the IEEE 802.16 standard's WirelessMAN air interface. This algorithm attempts to minimize the end-to-end delay in the system by selecting the optimal PHY burst profile on the air interface. The IEEE 802.16 standard recommends measuring C/(N+I) at the receiver to initiate a change in the burst profile, based on the comparison of the instantaneous the C/(N+I) with preset C/(N+I) thresholds. This research determines the C/(N+I) thresholds for the standard specified channel Type 1. To determine the precise C/(N+I) thresholds, the end-to-end(ETE) delay performance of IEEE 802.16 is studied for different PHY burst profiles at varying signal-to-noise ratio values. Based on these performance results, we demonstrate that link layer ETE delay does not reflect the physical channel condition and is therefore not suitable for use as the criterion for the determination of the C/(N+I) thresholds. The IEEE 802.16 standard specifies that ARQ should not be implemented at the MAC layer. Our results demonstrate that this design decision renders the link layer metrics incapable of use in the link adaptation algorithm. Transmission Control Protocol (TCP) delay is identified as a suitable metric to serve as the link quality indicator. Our results show that buffering and retransmissions at the transport layer cause ETE TCP delay to rise exponentially below certain SNR values. We use TCP delay as the criterion to determine the SNR entry and exit thresholds for each of the PHY burst profiles. We present a simple link adaptation algorithm that attempts to minimize the end-to-end TCP delay based on the measured signal-to-noise ratio (SNR). The effects of Internet latency, TCP's performance enhancement features and network traffic on the adaptation algorithm are also studied. Our results show that delay in the Internet can considerably affect the C/(N+I) thresholds used in the LA algorithm. We also show that the load on the network also impacts the C/(N+I) thresholds significantly. We demonstrate that it is essential to characterize Internet delays and network load correctly, while developing the LA algorithm. We also demonstrate that TCP's performance enhancement features do not have a significant impact on TCP delays over lossy wireless links. / Master of Science

Transmission Control Protocol (TCP) is considered one of the most important protocols in the Internet. An important mechanism in TCP is the congestion control mechanism which controls TCP sending rate and makes TCP react to congestion signals. Nowadays in heterogeneous networks, TCP may work in networks with some links that have lossy nature (wireless networks for example). TCP treats all packet loss as if they were due to congestion. Consequently, when used in networks that have lossy links, TCP reduces sending rate aggressively when there are transmission (non-congestion) errors in an uncongested network. One solution to the problem is to discriminate between errors; to deal with congestion errors by reducing TCP sending rate and use other actions for transmission errors. In this work we investigate the problem and propose a solution using an end-to-end error discriminator. The error discriminator will improve the current congestion window mechanism in TCP and decide when to cut and how much to cut the congestion window. We have identified three areas where TCP interacts with drops: congestion window update mechanism, retransmission mechanism and timeout mechanism. All of these mechanisms are part of the TCP congestion control mechanism. We propose changes to each of these mechanisms in order to allow TCP to cope with transmission errors. We propose a new TCP congestion window action (CWA) for transmission errors by delaying the window cut decision until TCP receives all duplicate acknowledgments for a given window of data (packets in flight). This will give TCP a clear image about the number of drops from this window. The congestion window size is then reduced only by number of dropped packets. Also, we propose a safety mechanism to prevent this algorithm from causing congestion to the network by using an extra congestion window threshold (tthresh) in order to save the safe area where there are no drops of any kind. The second algorithm is a new retransmission action to deal with multiple drops from the same window. This multiple drops action (MDA) will prevent TCP from falling into consecutive timeout events by resending all dropped packets from the same window. A third algorithm is used to calculate a new back-off policy for TCP retransmission timeout based on the network¿s available bandwidth. This new retransmission timeout action (RTA) helps relating the length of the timeout event with current network conditions, especially with heavy transmission error rates. The three algorithms have been combined and incorporated into a delay based error discriminator. The improvement of the new algorithm is measured along with the impact on the network in terms of congestion drop rate, end-to-end delay, average queue size and fairness of sharing the bottleneck bandwidth. The results show that the proposed error discriminator along with the new actions toward transmission errors has increased the performance of TCP. At the same time it has reduced the load on the network compared to existing error discriminators. Also, the proposed error discriminator has managed to deliver excellent fairness values for sharing the bottleneck bandwidth. Finally improvements to the basic error discriminator have been proposed by using the multiple drops action (MDA) for both transmission and congestion errors. The results showed improvements in the performance as well as decreases in the congestion loss rates when compared to a similar error discriminator. / Ministry of Higher Education and King Saud University in Saudi Arabia.