research group

Network Architectures and Services (NAS)

Department of Intelligent Systems

Area: Complex networks, e.g. road-traffic networks and the Internet, biological, brain, social, and financial sector networks. Focus on data communications and Internetworking

Our society depends more strongly than ever before on large, complex networks such as the Internet, telephony networks, transportation networks, social networks and power grids, while our health needs understanding of biological networks (metabolic, DNA, brain networks). Surely, complex networks surround us, but, do we understand how they really operate?

Around 2000, several remarkable, quite universal phenomena in complex networks gave birth to a new wave of network research that is still continuing and expanding from physics and mathematics to engineering, biology, medical sciences, social sciences, and even finance. For over 10 years, this new wave has led to innovative research with high potential impact and is still increasing (measured in the number of papers published). NAS has early-on recognized the opportunities in complex networks research and has extended its scope beyond merely computer networks to encompass complex network in general. The focus is on Network (theory), Architecture (testing), and Services (applications).

Research Themes

  1. Network: Our goal is to understand complex networks by studying graph metrics, spectral and topological properties, link weights or strengths, asymptotic scaling laws, the relation between the processes on and the underlying network itself (such as self-organized criticality, phase transitions and percolation), and the way biological networks evolve. An example of the coupling between process and network is virus spread: in addition to taking medicines (anti-virus software), we avoid contacts (change the network). Our understanding of how biological processes in nature achieve such an amazing adaptivity and resilience against external factors or which topological processes (such as rewiring, creation, deletion of links) are determining the network structure during the lifetime of an organism has direct applications when translated to man-made networks.
  2. Architectures: The Internet, on which we all rely, should be robust against “external perturbations” such as congestion, denial of service attacks, malware, power failures, etc. In our network laboratory, we study under which circumstances (usage patterns, external influences) a network breaks down. The interaction between (malicious) usage patterns and algorithms that are designed to cope with them (rerouting algorithms, congestion avoidance, anti-virus programmes etc) plays a major role.
  3. Services: Although NAS has a strong theoretical approach to networking that makes it a fairly unique player in the Netherlands, NAS underlines the importance of industrial collaboration and valorisation. Our work with industry covers energy efficient or robust network design for SURFnet, KPN, and Heerema, measurements with our test network, data mining of large-scale (online social) networks, as well as designing and analysing smart (power) grids with Alliander and TNO. Similarly, we work with the VU medical center on the robustness of the brain network. “Given a network, is it robust?” If not, what needs to be changed to achieve the desired level of robustness? For example, is a patient with a headache seriously ill (tumor, brain defect) or is an “aspirin” sufficient to help him or her. Based on MEG and EEG, the functional brain network is measured and “robustness” defined in terms of measurable quantities. This work allows to detect Alzheimer’s disease in an earlier stage.


The group is involved in the following courses:
CS4055High performance data networking5 ECdetails
EE2T21Telecommunications B5 ECdetails
EE4C06Networking5 ECdetails
EE8001Telecommunication networks (refresher course)2 ECdetails
ET4034Telecom architectures and business models4 ECdetails
ET4285Measuring and simulating the internet4 ECdetails
ET4389Complex networks from nature to man-made networks4 ECdetails
ET4397INNetwork security5 ECdetails
IN4253ET"Hacking lab" applied security analysis5 ECdetails
IN4341Performance analysis of communication networks and systems5 ECdetails


The group is involved in the following projects: