Chapter 4 How to Model and Enumerate Geographically Correlated Failure Events in Communication Networks Balazs´ Vass, Janos´ Tapolcai, David Hay, Jorik Oostenbrink, and Fernando Kuipers Abstract Several works shed light on the vulnerability of networks against regional failures, which are failures of multiple pieces of equipment in a geographical region as a result of a natural or human-made disaster. This chapter overviews how this in- formation can be added to existing network protocols through defining Shared Risk Link Groups (SRLGs) and Probabilistic SRLGs (PSRLGs). The output of this chap- ter can be the input of later chapters to design and operate the networks to enhance the preparedness against disasters and regional failures in general. In particular, we are focusing on the state-of-the-art algorithmic approaches for generating lists of (P)SRLGs of the communication networks protecting different sets of disasters. 4.1 Introduction The Internet is a critical infrastructure. Due to the importance of telecommunication services, improving the preparedness of networks to regional failures is becoming a key issue [5, 6, 9, 10, 11, 13, 14, 21, 22, 23, 28, 41]. The majority of severe network outages happen because of a disaster (such as an earthquake, hurricane, tsunami, tornado, etc.) taking down a lot of (or all) equipment in a given geographical area. Such failures are called regional failures. Many studies have touched the problem of Balazs´ Vass J anos´ Tapolcai MTA-BME· Future Internet Research Group, High-Speed Networks Laboratory (HSNLab) and Budapest University of Technology and Economics, Budapest, Hungary e-mail: vb, tapolcai @tmit.bme.hu { } David Hay Hebrew University, School of Engineering and Computer Science, Jerusalem, Israel, e-mail:
[email protected] Jorik Oostenbrink Fernando Kuipers Delft University of· Technology, Delft, The Netherlands e-mail: J.Oostenbrink, F.A.Kuipers @tudelft.nl { } 1 2 B.