Transport Protocols Research Papers - Academia.edu (original) (raw)

The telecommunications industry has undergone major paradigm shifts in previous years. One of these is the shift from circuit-switched networks towards packet-switched networks. There is hardly any doubt that IP will be the ubiquitous... more

The telecommunications industry has undergone major paradigm shifts in previous years. One of these is the shift from circuit-switched networks towards packet-switched networks. There is hardly any doubt that IP will be the ubiquitous transport protocol for multimedia of the future. At present, the work towards Internet telephony has attracted a lot of attention. Two standards have been developed: SIP (session initiation protocol) by the Internet Engineering Task Force (IETF) and H.323 by the International Telecommunications Union (ITU). The rapid deployment of services on top of SIP is hindered by a well known problem, feature interactions, also well known in traditional telephony networks. In this paper, the technological changes in SIP compared to the traditional telephony network are highlighted as well as the impact of the changed business environment. In a multi-service provider environment (as encouraged by a SIP environment), the feature interaction problem is regarded to be an even more pressing issue. Services of different providers from a multitude of service creators are likely to interwork. This in turn leads to the fact that the ad-hoc approaches to service interaction handling, commonly applied in the industry today, will not be sufficient any more. In this paper, a new approach addressing these changes is introduced and the results of a case study are presented

This paper presents the design, simulation and real-time implementation of an aircraft longitudinal control system using a test platform constituted of a dedicated microprocessor and the X-Plane flight simulator. Initially, the concepts... more

This paper presents the design, simulation and real-time implementation of an aircraft longitudinal control system using a test platform constituted of a dedicated microprocessor and the X-Plane flight simulator. Initially, the concepts of longitudinal motion of a rigid body are studied. The dynamic equations of aircraft were determined using the aerodynamic stability coefficients and the longitudinal derivates. With the aircraft dynamic equation, the altitude and vertical speed continuous controllers were designed using the inner loop pitch attitude and pitch rate feedback and the forward speed controller was designed using an engine throttle model. The continuous controllers designed were discretized. Then, the digital controllers were implemented in the microprocessor. Using the X-Plane flight simulator and the algorithm implemented in the dedicated microprocessor, the digital controllers were tested and validated into the model similar to real aircraft, minimizing risks and increasing flexibility for design changes. Basically, this experimental framework employs the microprocessor running the digital flight controllers to be tested, and a PC running the X-Plane flight simulator contained the aircraft to be commanded. These resources are interconnected through data buses in order to exchange information. The interconnection between autopilot hardware and the X-Plane host is made through data communication bus based on network protocol, Uniform Datagram Protocol (UDP) available in both systems. The X-Plane has the built-in capability of transmitting flight parameters and receiving command for aircraft flight control surfaces over Ethernet using UDP. The results show that the developed system structure is appropriate to test the longitudinal controllers. Matlab environment was used to visualize the values of the updates pitch attitude, altitude, vertical and forward speed in graphics plotted in real time. It permites to observe that the designed controllers impleme- - nted in experimental framework reaches the specified requirements successfully.

HTTP has been the protocol for transferring web traffic over the Internet since the 90s. However, over the past 20 years websites have evolved so much that today this protocol does not provide optimal delivery over the Internet and became... more

HTTP has been the protocol for transferring web traffic over the Internet since the 90s. However, over the past 20 years websites have evolved so much that today this protocol does not provide optimal delivery over the Internet and became a bottleneck in decreasing page load times. Google is pioneering in finding better solutions for downloading web pages and they implemented two new protocols: SPDY in 2009 and QUIC in 2013. Since the wide range deployment of SPDY clients and servers it has been revealed that in some scenarios SPDY can negatively affect the page transfer time mainly due to the fact that the protocol is working over TCP. To tackle these obstacles QUIC uses its own congestion control and based on UDP in the transport layer. Since QUIC is a very recent protocol, this paper could help further understand its operation and performance in a wide range of network scenarios. We present a comprehensive study about the performance of QUIC, SPDY and HTTP particularly about how they affect page load time. We found that none of these protocols is clearly better than the other two and the actual network conditions determine which protocol performs the best.

This paper describes an approach to detecting distributed denial of service (DDoS) attacks that is based on fundamentals of Information Theory, specifically Kolmogorov Complexity. A theorem derived using principles of Kolmogorov... more

This paper describes an approach to detecting distributed denial of service (DDoS) attacks that is based on fundamentals of Information Theory, specifically Kolmogorov Complexity. A theorem derived using principles of Kolmogorov Complexity states that the joint complexity measure of random strings is lower than the sum of the complexities of the individual strings when the strings exhibit some correlation. Furthermore, the joint complexity measure varies inversely with the amount of correlation. We propose a distributed active network-based algorithm that exploits this property to correlate arbitrary traffic flows in the network to detect possible denial-of-service attacks. One of the strengths of this algorithm is that it does not require special filtering rules and hence it can be used to detect any type of DDoS attack. We implement and investigate the performance of the algorithm in an active network. Our results show that DDoS attacks can be detected in a manner that is not sensitive to legitimate background traffic.