Personal website of

Prof. Dr.-Ing. habil. Falko Dressler

End-to-End Quality of Service Analysis


  • Regional Computing Center Erlangen, University of Erlangen-Nuremberg


  • Dr. Falko Dressler (coordination)
  • Dr. Ursula Hilgers
  • Dr. Peter Holleczek


  • internal project

Project Time

  • 01.06.1995 - 31.12.2003


e2eQoS - End-to-End Quality of Service Analysis
The primary goal of this project is to investigate end-to-end internet connections regarding their quality of service demands. Additionally, the network is being analyzed for its QoS characteristics such as the currently available QoS, service quality provisioning, and guaranteed quality levels. The research results are used to build frameworks for quality of service measurements as well as to create models allowing a more detailed simulation of the behavior of well-known networks. Typical application scenarios for the research results are QoS measurements and predictions for forthcoming applications, primarily real-time multimedia transmissions such as video conferences or multimedia streamings.

mediaServ - Distributed Multimedia Services
The project mediaServ was initiated in order to analyze and test environments for distributed media server in the internet. It is a common approach to replicate mission-critical content to distributed servers for several reasons. Examples are high-availability solutions, an efficient load-balancing, and the opportunity to offer different paths through the network from the servers towards the clients. A primary goal of this project is to define selection criteria which can be employed by the clients to allow them a more sophisticated selection of a particular server for a forthcoming distribution of multimedia content. The main focus is on the currently available quality of service in the network between the server and the client. Mechanisms are developed and analyzed which allow one such a meaningful selection process.

tmt4atm - Transmit delay Measurement Tool for ATM
tmt4atm (Transmit delay Measurement Tool for ATM) is a tool to measure transmission delays in ATM based networks. The delay is a very interesting QoS (quality of service) parameter of a network. Primarily, it depends on the transmission speed of the carrier (mostly fiber, sometimes copper) and on the capabilities and efficiency of the switches (routers). Most SLAs (service level agreements) with ISPs (internet service providers) include definitions of the QoS. An example is the German broadband educational network (B-WiN) for which the program has been developed. The contract between the DFN e.V. and the Deutsche Telekom defines a maximum acceptable delay but also an minimum reliability of the network. tmt4atm sends ATM cells over the network to measure the transmit delay and (if there is no answer) network failures. The hardware which has been chosen for the implementation is a Sun SPARC Station in combination with the SunATM board. The first version of tmt4atm was the result of the Pre-Master's Thesis (Studienarbeit) of Falko Dressler. Unfortunately, this version has not met all requirements, i.e., it was too slow to measure delays in the range of some milliseconds due to the implementation as a user process in the UNIX environment. A full redesign of the code was necessary. Since version 2.0 the real measurement of the transmit delay happend in kernel mode (with a patched driver for the Sun ATM board) and only calculations and control functions are implemented in user mode. The last version developed by Falko Dressler in 1997 is tmt4atm V2.2c. This version was employed for measurements in the German research network (B-WiN) for several years (1996-2000) in order to control the available quality of service in the ATM backbone network.

Selected Publications

  • Falko Dressler, "A Metric for Numerical Evaluation of the QoS of an Internet Connection," Proceedings of 18th International Teletraffic Congress (ITC18), vol. 5b, Berlin, Germany, August 2003, pp. 1221–1230. [DOI, BibTeX, PDF and Details...]
  • Falko Dressler, "An Approach to Select a Best Suitable Video Server," Proceedings of International Conference on Advances in Infrastructure for Electronic Business, Education, Science, Medicine, and Mobile Technologies on the Internet (SSGRR 2003w), L'Aquila, Italy, January 2003. [BibTeX, PDF and Details...]
  • Falko Dressler, "QoS considerations on IP multicast services," Proceedings of International Conference on Advances in Infrastructure for Electronic Business, Education, Science, and Medicine on the Internet (SSGRR 2002w), L'Aquila, Italy, January 2002. [BibTeX, PDF and Details...]
  • Ursula Hilgers and Falko Dressler, "Echtzeit-Datenverkehr über IP-basierte Datennetze," Proceedings of Echtzeitkommunikation und Ethernet/Internet: Fachtagung der GI-Fachgruppe 4.4.2 Echtzeitprogrammierung (PEARL 2001), Boppard, Germany, November 2001, pp. 29–39. [BibTeX, PDF and Details...]