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University: K.U.Leuven
Name of sponsoring Professor: Prof. Antoine Van de Capelle
Department: Electrical Engineering, TELEMIC Division

Current research topics at ESAT-Telemic benefitting from OPNET Modeler results

  1. Study of closed-loop effects in aggregated TCP streams
    1. Description
      Packet switched networks are increasingly important in exchanging information. The succes of the internet is widely known. The major advantage of this way of communicating is the fact that different data flows can efficiently make use of the available bandwidth. One of the drawbacks is the dimensioning of these networks. Opposed to circuit switched networks, where this was reasonably simple, dimensioning packet switched networks is a lot more complicated. The old solutions, namely overdimensioning the available capacity or solving problems when it's (almost) too late, are no longer sustainable. Network managers have to be able to make accurate predictions about the quality than can be offered by their network.

      To make such predictions, two things are important. First one has to have a clear image of the traffic that needs to be transported by the network. Second, one needs to know the amount of delay or loss induced by the different components (such as routers, switches, links, ...) in case of a certain load on the network. What is mostly forgotten is the fact that packet losses and delays can influence the amount and the pattern of traffic that has to be transported. This obviously happens when the TCP protocol is used. When packets are lost, they wil be retransmitted until their correct arrival is acknowledged. On top of that, TCP has flow control mechanisms that adapt the transmission speed of the individual flows when packets are lost. So it's obvious that both the amount and the pattern of traffic will change when congestion occurs in the network. These changes then again affect packet loss, and so on. An analysis of these closed-loop effects is thus quite important to predict delays and losses in the network.

    2. The use of OPNET Modeler
      OPNET Modeler is used to study the effects that different flow control and congestion control mechanisms have on the traffic pattern in a network.

    3. Specialized protocols used
      None

    4. PhD student working on this topic
      Kristof Sleurs

  2. Design of a reliable communication network for an electrical power grid
    1. Description
      We plan to use Modeler together with the SITL module for the project "Reaching for 100% reliable electricity services: multi-system interactions and fundamental solutions," which is a fundamental research project (id 3E051043) sponsored by our university. The multidisciplinary project involves two research divisions of our department. Our task consists of the design of a reliable, QoS-enabled, secure IP based network for communication (both information and control messages) between electrical power generators and loads. In a lab environment we want to attach several electrical power devices that support the SCADA (Supervisory Control and Data Acquisition) application (and have an Ethernet interface) to an emulation platform. We believe that OPNET Modeler combined with the SITL module offers the best platform to investigate the impact of packet latencies, packet loss, routing failures, ... inside the IP based network on the stability of the electrical power system.

    2. The use of OPNET Modeler
      OPNET Modeler is used to investigate the impact of packet latencies, packet loss, routing failures, ... inside the IP based network on the stability of the electrical power system.

    3. Specialized protocols used
      None

    4. PhD student working on this topic
      Linyu Wang

  3. Study of new mechanisms for seamless vertical handovers
    1. Description
      Mobility support in the internet is an increasing demand with the development of wireless and portable techniques. Moving between access networks of different types invokes vertical handovers. There are two things to be solved before a transparent vertical handover is possible. First the delay and packet loss caused by the handover should be carefully taken care of. Secondly, on-going sessions should adapt quickly to the conditions on the new link. The first problem can be handled by various of seamless vertical handover techniques, while the second problem needs modification or extension to the current transport mechanisms that do not support the required adaptation. In this research new mechanisms will be developed to improve the performance of on-going sessions in the transition of a vertical handover. This goal requires the combination of the former mentioned two aspects for an efficient and flexible solution.

    2. The use of OPNET Modeler
      OPNET Modeler is used to examine and evaluate new handover mechanisms in different network setups.

    3. Specialized protocols used
      None

    4. PhD student working on this topic
      Dagang Li

Former research topics at ESAT-Telemic benefitting from OPNET Modeler results (from 2006)

  1. Congestion Control for Stable Packet Switched Networks
    1. Description
      Traffic on the Internet is evolving from best effort data traffic, which the Internet was originally designed for, to a mixture of both best effort traffic and an ever increasing number of real-time multimedia traffic streams. These multimedia traffic streams are not very well handled by TCP (Transmission Control Protocol) on the transport layer, especially because of the retransmission mechanism they have no use for. This growing amount of non-TCP streams may however cause some serious problems in the near future.

      During the last few decades the Internet has been kept stable by the congestion avoidance and congestion control mechanisms implemented in TCP. To attain this stability TCP relies on the cooperation of all end-hosts. The validity of this assumption however is severely decreasing due to the aforementioned changing nature of the traffic on the Internet. As a consequence we may yet again experience severely decreasing network utility due to increasing load, also known as congestion collapse.

      The goal of this research project is to develop a congestion avoidance and control mechanism that can protect the network from this poor condition of congestion collapse. In order to make the stability of the network less reliant on the cooperation of the end-hosts, this mechanism will be implemented in the network itself.

      The mechanism will be developed and initially tested using OPNET Modeler, before more extensive tests are carried out, both in OPNET simulations, as with an implementation of the mechanism in our networking lab.

    2. The use of OPNET Modeler
      OPNET Modeler is used both to develop our new congestion control mechanism, as well as to test the behavior of the mechanism and its interaction with existing congestion control solutions in several scenarios.

    3. Specialized protocols used
      IPv6

    4. PhD student working on this topic
      Bart Van den Broeck

Teaching:

Current courses using OPNET Modeler

  1. B-KUL-H05J3A Telecommunication and Telematic Systems: 10 simulation labs on OPNET are given based on the Network Simulation Experiments Manual by Prof. Aboelela. The syllabus can be found here.

Current Master thesises using OPNET Modeler

Former educational networking design projects using OPNET Modeler

  1. Dimensioning a PPP link in a realistic corporate network (2003-2003): The students had to analyze a fake realistic business network, which consisted of a WAN in Brussels and whose headquarters were located in Rome. The WAN in Brussels was connected to the headquarters by a PPP link. First students had to measure background traffic and analyze an applications. Later the topology of the network wass implemented in OPNET Modeler and the background traffic and application was added, along with a VoIP application between Brussels and Rome. Then, the PPP link was dimensioned. Finally, QoS issues were investigated and priority queuing was added to some routers in the network. More information on the project and the final report of the students is available on-line.
  2. Voice over IP (VoIP) on KOTNet (2001-2002): This project focuses on the implementation of VoIP on K.U.Leuven's network infrastructure for students (KOTNet). It investigates the impact of VoIP on existing network characteristics if VoIP would be offered at all students dorms of K.U.Leuven. Extensive simulations using OPNET Modeler were performed to predict this impact. More information on the project and the final report of the students is available on-line.
  3. Wireless LANs (WLANs) in auditoria (2001-2002): This project investigates the possibility of offering WLAN to students in auditoria of K.U.Leuven. OPNET Modeler is used to simulate different scenarios depending on the students behavior. Out of the results indicating the load on the WLAN networks, the imposed delay and the traffic drops on the WLAN, conclusions were drawn. More information on the project and the final report of the students is available on-line.
  4. Video streaming on KOTNet (2001-2002): This project focuses on the offering of video services on KOTNet to students living in K.U.Leuven's student dorms. Results obtained from simulations in OPNET Modeler predicted the impact of this service on traffic and network characteristics. More information on the project and the final report of the students is available on-line.
  5. Previous projects can also be found on-line: 1999-2000 and 2000-2001.

Former Master thesises using OPNET Modeler

  1. Linyu Wang (2007-2008): Design of a reliable communication network for an electrical power grid: We plan to use Modeler together with the SITL module for the project "Reaching for 100% reliable electricity services: multi-system interactions and fundamental solutions," which is a fundamental research project (id 3E051043) sponsored by our university. The multidisciplinary project involves two research divisions of our department. Our task consists of the design of a reliable, QoS-enabled, secure IP based network for communication (both information and control messages) between electrical power generators and loads. In a lab environment we want to attach several electrical power devices that support the SCADA (Supervisory Control and Data Acquisition) application (and have an Ethernet interface) to an emulation platform. We believe that OPNET Modeler combined with the SITL module offers the best platform to investigate the impact of packet latencies, packet loss, routing failures, ... inside the IP based network on the stability of the electrical power system.
  2. Ye Guan (2002-2003): Implementation of an Advanced Traffic Model in OPNET Modeler: Traditional traffic models like the Poisson model are inappropriate to accurately model the bursty behavior of real network traffic. Performance analysis based on these models can lead to a severe underestimation of packet delay or loss, with badly dimensioned networks as a result. Telemic developed a new traffic model, which is based on a hierarchical scheme of Bernoulli sources and was presented at ICC2003. Contrary to most other self-similar traffic models, this model allows to efficiently generate traffic of which the mean, the variance and the Hurst parameter can be set in an easy way. This master thesis implemented the generator based on this new traffic model in OPNET Modeler. The benefits of the method were made clear by means of a case study in which our model is compared to the models available in the Raw Packet Generator (RPG).
  3. Bert Rodiers (2001-2002): Analysis and simulation of the K.U.Leuven network: The aim of the thesis was to make a simulation model in OPNET Modeler of the backbone at the K.U.Leuven, Belgium. The backbone consists of five Cisco Catalyst 5500 switches in a ring topology interconnected by full-duplex Gigabit Ethernet links. Accurate real-life measurements are used to add background traffic to this topology. The use of VLANs to separate traffic generated by students and personnel adds extra difficulties (the traffic is routed at different locations).

Authored papers

  1. J. Theunis, J. Potemans, M. Teughels, E. Van Lil, A. Van de Capelle, "Project Driven Network Education", Proc. to the International Conference on Networking ICN '01, Colmar, France, pp. 790-802, 2001. Click here to download PDF.
  2. J. Potemans, J. Theunis, M. Teughels, E. Van Lil and A. Van de Capelle, "Student Network Design Projects Using OPNET", OPNETWORK 2001, Washington D.C., USA, 2001. Click here to download PDF.
  3. J. Theunis, J. Potemans, P. Leys, B. Van den Broeck, E. Van Lil, A. Van de Capelle, "OPNET in Advanced Networking Education", OPNETWORK 2002, Washington D.C., USA, 2002.  Click here to download PDF.
  4. J. Potemans, J. Theunis, B. Rodiers, B. Van den Broeck, P. Leys, E. Van Lil, A. Van de Capelle, "Simulation of a Campus Backbone Network, a case-study", OPNETWORK 2002, Washington D.C., USA, 2002.  Click here to download PDF.
  5. B. Van den Broeck, P. Leys, J. Potemans, J. Theunis, E. Van Lil, A. Van de Capelle, "Validation of Router Models in OPNET", OPNETWORK 2002, Washington D.C., USA, 2002. Click here to download PDF.
  6. P. Leys, J. Potemans, B. Van den Broeck, J. Theunis, E. Van Lil, A. Van de Capelle, "Use of the Raw Packet Generator in OPNET", OPNETWORK 2002, Washington D.C., USA, 2002. Click here to download PDF.
  7. J. Theunis, P. Leys, J. Potemans , B. Van den Broeck, E. Van Lil and A. Van de Capelle, "Advanced Networking Training for Master Students Through OPNET Projects", OPNETWORK 2003, Washington D.C., USA, 2003. Click here to download PDF.
  8. J. Potemans , B. Van den Broeck, Y. Guan, J. Theunis, E. Van Lil and A. Van de Capelle, "Implementation of an Advanced Traffic Model in OPNET Modeler", OPNETWORK 2003, Washington D.C., USA, 2003. Click here to download PDF.
  9. Y. Guan, B. Van den Broeck, J. Potemans, J. Theunis, D. Li, E. Van Lil, A. Van de Capelle, "Simulation Study of TCP Eifel Algorithms", OPNETWORK 2005, Washington D.C., USA, 2005. Click here to download PDF.
  10. K. Sleurs, J. Potemans, B. Van den Broeck, J. Theunis, D. Li, E. Van Lil, A. Van de Capelle, "Importing Binned Background Traffic Flows into OPNET", OPNETWORK 2006, Washington D.C., USA, 2006. Click here to download PDF.

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