Stylianos Georgoulas

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Student: Stylianos Georgoulas
Title: Admission Control and Bandwidth Management in IP

Differentiated Services Networks

Affiliation: UniS
Supervisor: George Pavlou
Start: 2002
End: 2006
Funding: Centre for Communication Systems Research,

University of Surrey


Stylianos Georgoulas was admitted to the Department of Electrical and Computer Engineering at the University of Patras in Greece and received his Diploma in 2001. He subsequently got his PhD degree in Networking at the Department of Electronic Engineering, University of Surrey, UK, in 2006. He is currently a post-doctoral Research Fellow at the Center for Communication Systems Research (CCRS), University of Surrey. During his time at Surrey he has been involved in the EU IST MESCAL, ENTHRONE, and EMANICS projects. His research interests are in the area of admission control and bandwidth management/ traffic engineering for QoS-enabled IP networks.

PhD project description

The ever increasing importance of IP networks to home and business users, the steadily growing number of devices and services that run on them and the evolution of Internet towards the global multiservice network of the future make the efficient utilization of resources an issue of great importance and the capability to provide Quality of Service (QoS) an important challenge. It is widely accepted that the current Internet, using the simple best effort service model, is not able to support in a satisfactory fashion emerging services and market demands, such as Voice over IP (VoIP), Videoconferencing and real-time traffic in general. The latter has QoS requirements that the current best effort Internet cannot provide in a resource and, consequently, cost efficient manner, e.g. without massive overprovisioning. Differentiated Services (DiffServ) are seen as the emerging technology to support QoS in IP networks without the inherent scalability problems of Integrated services (IntServ). This is achieved by grouping traffic with similar QoS requirements into a finite number of traffic classes, allocating bandwidth to these classes, and differentiating their forwarding treatment in the network. However, by simply providing forwarding differentiation, DiffServ does not fundamentally solve the problem of controlling congestion. If the amount of traffic injected in a given class is not controlled through admission control, overload situations will occur and all traffic flows in that class will suffer a potentially harsh QoS degradation. The main objectives of this thesis are to investigate issues related to bandwidth allocation for provisioning real-time traffic classes and to propose admission control functions that can prevent overload situations so that the designated QoS guarantees are provided, while at the same time improving the allocated resources utilization under any offered traffic load conditions. We begin by investigating certain bandwidth management related issues with respect to bandwidth allocation and admission control schemes for the support of real-time traffic in DiffServ networks, related to the performance of the schemes as a function of topological placement and assumed multiplexing gains. We validate our study using simulations with the publicly available ns-2 simulator. Taking into account the implications of our bandwidth management study we then proceed to present our approach towards admission control for real-time traffic in DiffServ network domains, covering both the case where the traffic originates and terminates within the same domain (intra-domain traffic) as well as the case where the traffic has to traverse a sequence of domains before reaching its destination (inter-domain traffic). By means of simulations we show that our proposed schemes perform very well and that they compare favourably against other schemes found in the literature.

Key words: Admission Control, Bandwidth Management, Differentiated Services (DiffServ), Quality of Service (QoS), Real-time traffic.


  1. S. Georgoulas, G. Pavlou, K. Ho and P. Trimintzios, “An Integrated Bandwidth Allocation and Admission Control Framework for the Support of Heterogeneous Real-time Traffic in Class-based IP Networks”, submitted to Elsevier Computer Communications (please note that this one is undergoing reviewing, so maybe it cannot be included in the published papers list)
  2. S. Georgoulas, P. Trimintzios, G. Pavlou and K. Ho, “On the Location-awareness of Bandwidth Allocation and Admission Control for the Support of Real-time Traffic in Class-based IP Networks”, IEEE/IFIP MMNS 2006.
  3. S. Georgoulas, P. Trimintzios, G. Pavlou and K. Ho, “Heterogeneous Real-time Traffic Admission Control in Differentiated Services Domains”, IEEE GLOBECOM 2005.
  4. S. Georgoulas, P. Trimintzios, G. Pavlou and K. Ho, “Measurement-based Admission Control for Real-time Traffic in IP Differentiated Services Networks”, IEEE ICT 2005.
  5. S. Georgoulas, P. Trimintzios and G. Pavlou, “Admission Control Placement in Differentiated Services Networks”, IEEE ISCC 2004.
  6. S. Georgoulas, P. Trimintzios and G. Pavlou, “Joint Measurement- and Traffic Descriptor-based Admission Control at Real-Time Traffic Aggregation Points”, IEEE ICC 2004.
  7. S. Georgoulas, P. Trimintzios and G. Pavlou, “A Measurement-based Connection Admission Control Framework for Real-Time Traffic at Differentiated Services (DiffServ) Aggregation Points”, PGNET 2003.
  8. S. Georgoulas, G. Pavlou, P. Flegkas and P. Trimintzios, “Buffer and Bandwidth Management for the Expedited Forwarding Traffic Class in Differentiated Services Networks”, LCS 2002.

Additional information

External links