Efficient Transport Protocol for Networked Haptics Applications

The performance of haptic application is highly sensitive to communication delays and losses of data. It implies several constraints in developing networked haptic applications. This paper describes a new internet protocol called Efficient Transport Protocol (ETP), which aims at developing distributed interactive applications. TCP and UDP are transport protocols commonly used in any kind of networked communication, but they are not focused on real time application. This new protocol is focused on reducing roundtrip time (RTT) and inter packet gap (IPG). ETP is, therefore, optimized for interactive applications which are based on processes that are continuously exchanging data.ETP protocol is based on a state machine that decides the best strategies for optimizing RTT and IPG. Experiments have been carried out in order to compare this new protocol and UDP

Disturbance Rejection and Control in Web Servers

An important factor for a user of web sites on the Internet is the duration of time between the request of a web page until an answer has been returned. If this response time is too long, the user is likely to abandon the web site and search for other providers of the service. To avoid this loss of users, it is important for the web site operator to assure that users are treated sufficiently fast. On the other hand, it is also important to minimize the effort to optimize profit. As these objectives often are contradictory, an acceptable target response-time that can be formulated. The resources are allocated in a manner that ensures that long response times do not occur, while, at the same time, using as little resources as possible to not overprovision. The work presented in this doctoral thesis takes a control-theoretic perspective to solve this problem. The resources are considered as the control input, and the response time as the main output. Several disturbances affect the system, such as the arrival rate of requests to the web site. A testbed was designed to allow repeatable experiments with different controller implementations. A server was instrumented with sensors and actuators to handle requests from 12 client computers with capability for changing work loads. On the theoretical side, a model of a web server is presented in this thesis. It explicitly models a specific sensor implementation where buffering occurs in the computer prior to the sensor. As a result, the measurement of the arrival rate becomes state dependent under high load. This property turns out to have some undesirable effects on the controlled system. The model was capable of predicting the behavior of the testbed quite well. Based on the presented model, analysis shows that feed-forward controllers suggested in the literature can lead to instability under certain circumstances at high load. This has not been reported earlier, but is in this doctoral thesis demonstrated by both simulations and experiments. The analysis explains why and when the instability arises. In the attempt to predict future response-times this thesis also presents a feedback based prediction scheme. Comparisons between earlier predictions to the real response-times are used to correct a model based response time prediction. The prediction scheme is applied to a controller to compensate for disturbances before the effect propagates to the response time. The method improves the transient response in the case of sudden changes in the arrival rate of requests. This doctoral thesis also presents work on a control solution for reserving CPU capacity for a given process or a given group of processes on a computer system. The method uses only existing operating-system infrastructure, and achieves the desired CPU capacity in a soft real-time manner

End-to-end congestion control protocols for remote programming of robots, using heterogeneous networks: A comparative analysis

There are many interesting aspects of Internet Telerobotics within the network robotics context, such as variable bandwidth and time-delays. Some of these aspects have been treated in the literature from the control point of view. Moreover, only a little work is related to the way Internet protocols can help to minimize the effect of delay and bandwidth fluctuation on network robotics. In this paper, we present the capabilities of TCP, UDP, TCP Las Vegas, TEAR, and Trinomial protocols, when performing a remote experiment within a network robotics application, the UJI Industrial Telelaboratory. Comparative analysis is presented through simulations within the NS2 platform. Results show how these protocols perform in two significant situations within the network robotics context, using heterogeneous wired networks: (1) an asymmetric network when controlling the system through a ADSL connection, and (2) a symmetric network using the system on Campus. Conclusions show a set of characteristics the authors of this paper consider very important when designing an End-to-End Congestion Control transport protocol for Internet Telerobotics

Congestion Control for Streaming Media

The Internet has assumed the role of the underlying communication network for applications such as file transfer, electronic mail, Web browsing and multimedia streaming. Multimedia streaming, in particular, is growing with the growth in power and connectivity of today\u27s computers. These Internet applications have a variety of network service requirements and traffic characteristics, which presents new challenges to the single best-effort service of today\u27s Internet. TCP, the de facto Internet transport protocol, has been successful in satisfying the needs of traditional Internet applications, but fails to satisfy the increasingly popular delay sensitive multimedia applications. Streaming applications often use UDP without a proper congestion avoidance mechanisms, threatening the well-being of the Internet. This dissertation presents an IP router traffic management mechanism, referred to as Crimson, that can be seamlessly deployed in the current Internet to protect well-behaving traffic from misbehaving traffic and support Quality of Service (QoS) requirements of delay sensitive multimedia applications as well as traditional Internet applications. In addition, as a means to enhance Internet support for multimedia streaming, this dissertation report presents design and evaluation of a TCP-Friendly and streaming-friendly transport protocol called the Multimedia Transport Protocol (MTP). Through a simulation study this report shows the Crimson network efficiently handles network congestion and minimizes queuing delay while providing affordable fairness protection from misbehaving flows over a wide range of traffic conditions. In addition, our results show that MTP offers streaming performance comparable to that provided by UDP, while doing so under a TCP-Friendly rate

Bandwidth Problem in High Performance Packet Switching Network

Pre-print of "Bandwidth Problem in High Performance Packet Switching Network". The final publication is available at www.springerlink.comHigh performance packet switching networks are being deployed to provide sufficient data bandwidth for end users 3G services such as video streaming and broadband like data services. The use of high performance networks is, therefore, essential to the success of any 3G service. However, in practice, the deployment of High performance packet switching networks is hindered due to the improper congestion control which consequently results longer delays. In this paper, we propose a new method that can effectively improve the congestion control in high performance packet switching networks. Our numerical and simulation results demonstrate that the proposed method can be implemented for both lightly and heavily loaded networks. Simulation results show that the transmission delays can also be reduced significantly that improves the over all performance of high performance packet switching networks.http://link.springer.com/chapter/10.1007/978-1-4020-8737-0_9