Mathematics of Information Technology and Complex Systems Complex Adaptive Networks for Computing and Communication (CANCCOM)


Project Highlights


Team Members

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Project Highlights
            - Optical/IP Network Performance

As part of a subproject on IP congestion control, we studied the benefits of Explicit Congestion Notification (ECN) and Backward Explicit Congestion Notification (BECN) on a test bed with different TCP modifications. Both ECN and BECN showed considerable improvements over traditional methods of congestion control in IP networks. The evaluation of BECN showed further improvement over ECN. Furthermore, we studied different active buffer management schemes for Assured Forwarding Per Hop Behavior (AF-PHB) in a differentiated services (DiffServ) environment. Important results related to buffer management schemes for AF PHB have been derived and published.

The work already performed has shown positive results in favor of explicit congestion control (ECN and BECN). Further study for improvement is being done with BECN and Multi-Level BECN initially using the ns simulator. The project was recently completed. The student Akujobi has completed his masters thesis and is now employed by Carleton University (Department of Computing and Communication Services). The research is in the area of comparison of BECN and ECN and optimal adjustment of the BECN control parameters for minimizing congestion in IP routers. A paper was published in IEEE Globecom 2002. Furthermore, the student Yi has extended similar results for congestion control in gateways, completed his masters thesis and submitted a research publication in October 2003. The student Adegboyega is also working in this area and he is expected to complete his thesis in early January 2004.

Turning to the project on video multicasting over IP, we modeled and developed a software realization of an MPEG4 video traffic generator (which was contributed to the ns community and can be found at using the Transform Expand Sample (TES) methodology. The implementation was done in C++ and OTcl and was integrated in the network simulator ns. We investigated problems with multi-rate (layered) approaches for video multicast congestion control. We identified the source of unfair behavior of a layered approach to congestion control for video multicasting. We showed the effect of three factors on fairness: the flow/congestion control used by the video transport protocols for multicast applications, the traffic rate distribution across the video layers and third, the burstiness of the video source. ECN for video multicasting was developed based on RED buffer management. This research was motivated by and is connected with the first part of the project on IP congestion control. We proposed the use of different forms of explicit congestion notification (ECN, BECN and MECN) to avoid congestion while it is being developed in a network. Some of these techniques have already been in use in the case of unicast traffic (in the first part of our project). We proposed its extension to the multicast case. We have done a performance study of end-to-end architectures using network support from different ECN techniques for the multicasting of MPEG4 over IP.

The student Matrawy has further elaborated in the areas of explicit congestion notification and performance study of end-to-end architectures using Diffserv based QoS for video multicasting. A number of publications have been accepted to referred IEEE journals. He successfully defended his doctoral thesis and awarded the degree in the summer 2003 convocation.

Regarding the sub-project in the area of optical networks performance the research has developed in two main areas. We have studied the extension of the Border Gateway routing Protocol (BGP) to optical networks. The BGP has been used in the Internet for interdomain routing. However, contrary to packet networks (such as the Internet) optical networks need to open end-to-end connections (lightpaths), since routing cannot be done on a hop-by-hop manner (as in the Internet) if optical to electrical conversion is not used (which is expensive, slow and therefore not desirable). Modifying BGP in order to be used in optical networks and operate by setting up lightpaths in an end-to-end fashion is a major task. Simulations in OPNET enabled us to propose the necessary modifications and transform BGP to Optical BGP (OBGP). Furthermore, performance analysis of routing protocols in optical networks has been initiated in collaboration with researchers from the faculty of the School of Mathematics and Statistics at Carleton University. One doctoral student, co-supervised by Prof. Lambadaris and Prof. Zhao, has investigated the performance of OBGP under different wavelength availability/distribution schemes for establishing end-to-end lightpaths. Numerical approximations and simulations using OPNET are in close agreement.
In terms of student training The student Francisco has completed his masters thesis on OBGP and is defending in January 2004. The students Li and Pezoulas have successfully defended their masters degree in the area of optical network routing. The student Zhang has successfully defended his masters in the area of path protection in optical networks.

Finally, the following extensions to the research are as follows: For the sub-project in IP congestion control we are currently investigating MPEG 4 video multicasting and related security issues over MPLS networks. In the area of optical networks we are investigating optimal wavelength allocation in WDM networks and scheduling in optical resilient packet rings.


                                                        Maintained by Jeyanthi Hall     Copyrights@CANCCOM 2003    Last modified: Monday October 18, 2004