rtDVT using MPEG2 [4 : 2 : 2] compression and a bandwidth of 40 Mb/s did not effectively differ from the original video images in routine tele-endoscopy. The qualitative requirements in diagnostic video endoscopy, however, are obviously much higher than previously assumed, since experienced endoscopists detected a loss of image quality and a reduction in diagnostic usability with any reduction in the technical specification. Modern methods of data compression, broadband networks and a network protocol with good quality-of-service guarantees are therefore prerequisites for diagnostic rtDVT.

With the continuous increase of network capacities, video transmissions in medicine are becoming an effective tool for second opinion diagnosis, archiving and teaching environments. This study investigates video compression delay times and transmission impairments for different compression formats and describes the resulting picture qualities. For the evaluation endoscopic video sequences were produced with different compression formats and bandwidth requirements. In a second step an impairment tool was used to introduce error rates to the video material to simulate network behavior. A group of medical experts evaluated the video sequences rating visibility of errors, artifacts, sharpness, overall picture quality and suitability for a medical diagnosis. The results clearly establish lower boundaries for picture quality deteriorated by compression and network impairments, and introduce limits for medical assessments.

The Internet, undoubtedly, is the most influential\ud technical invention of the 20th century\ud that affects and constantly changes all aspects\ud of our day-to-day lives nowadays. Although it\ud is hard to predict its long-term consequences,\ud the potential future of the Internet definitely\ud relies on future Internet research. Prior to\ud every development and deployment project, an\ud extensive and comprehensive research study\ud must be performed in order to design, model,\ud analyze, and evaluate all impacts of the new\ud initiative on the existing environment. Taking\ud the ever-growing size of the Internet and the\ud increasing complexity of novel Internet-based\ud applications and services into account, the\ud evaluation and validation of new ideas cannot\ud be effectively carried out over local test beds\ud and small experimental networks. The gap\ud which exists between the small-scale pilots in\ud academic and research test beds and the realsize\ud validations and actual deployments in production\ud networks can be bridged by using\ud virtual infrastructures. FEDERICA is one of\ud the facilities, based on virtualization capabilities\ud in both network and computing resources,\ud which creates custom-made virtual environments\ud and makes them available for Future\ud Internet Researchers. This article provides a\ud comprehensive overview of the state-of-the-art\ud research projects that have been using the virtual\ud infrastructure slices of FEDERICA in\ud order to validate their research concepts, even\ud when they are disruptive to the test bed’s infrastructure,\ud to obtain results in realistic network\ud environments.Postprint (published version

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Measuring packet delay and packet loss through dedicated test packet streams in computer networks allows for the assessment of Quality of Service on the path the probes traverse. For this reason, active IP performance measurements have been carried out in X-WiN, Germany's National Research and Educational Network, and GÉANT2, its European counterpart, by the WiN-Labor Group of the University of Erlangen-Nuremberg for many years. This paper provides an overview of how network measurements can be interpreted using a variety of statistical concepts in order to gain insight into the state of monitored connections. The focus here is set on the analysis of One-Way Delay (OWD); the approach demonstrates how OWD can be used for the identification of network congestions and can serve as a basis for network alert systems by statistically categorizing changes in the performance metric.