JOUR 601 Lecture Notes - Lecture 45: Degree Distribution, Average Path Length, Network One
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Network Robustness and Resilience
Robustness and criticality are often thought of in terms of a systems capacity to maintain
functionality in the face of external perturbations.
Ecological networks that persist despite extreme environmental changes
o Communications networks like the internet can often deal with malfunction errors and
attacks without these local events leading to catastrophic global failures
We also see the opposite where some small failure (in a financial system for example) can
propagate to affect the whole system.
Trying to understand how and why this happens is the study of network robustness
Robustness can be correlated with connectivity in connectivity enabled systems integration
Without connectivity, parts to the system may become disconnected and disintegrated
When we are talking about robustness and resilience, we are asking what will happen to the
networks overall connectivity and integration if we remove some components or connections
and how will this failure spread within the network system
Node percolation: we can think about failure either with the respect to the networks nodes
asking what will happen if we remove a certain amount.
Edge percolation: failure in terms of removing edges. The key here is whether the attack is
random or strategic
When we talk about robustness with nodes in the network, then a key factor is the degree of
distribution between the nodes
o The higher degree of distribution, meaning more hubs, the more valuable it is to
o If it is a random attack, then the degree distribution is not so important
As these hubs that are a part of centralized networks will be particularly vulnerable to strategic
Distributed networks will be robust to strategic attack, but scale-free centralized networks are
particularly susceptible to attacks of these kind
A strategic attack on large hubs will drastically reduce the number of connections within the
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