Content accessibility in optical cloud networks under targeted link cuts

One of the key enablers of the digital society is a highly reliable information infrastructure that can ensure resiliency to a wide range of failures and attacks. In cloud networks, replicas of various content are located at geographically distributed data centers, thus inherently enhancing cloud network reliability through diversification and redundancy of user accessibility to the content. However, cloud networks rely on optical network infrastructure which can be a target of deliberate link cuts that may cause service disruption on a massive scale. This paper investigates the dependency between the extent of damage caused by link cuts and a particular replica placement solution, as a fundamental prerequisite of resilient cloud network design that lacks systematic theoretical quantification and understanding. To quantify the vulnerability of optical cloud networks based on anycast communication to targeted link cuts, we propose a new metric called Average Content Accessibility (ACA). Using this metric, we analyze the impact of the number and the placement of content replicas on cloud network resiliency and identify the best and the worst case scenarios for networks of different sizes and connectivity. We evaluate the efficiency of simultaneous and sequential targeted link cuts, the latter reassessing link criticality between subsequent cuts to maximize disruption. Comparison with Average Two-Terminal Reliability (A2TR), an existing robustness measure for unicast networks, shows great discrepancy in the vulnerability results, indicating the need for new measures tailored to anycast-based networks.