Long-lifetime capacity upgrades of ring networks for unpredictable traffic

Traffic forecasting is an important means to facilitate network capacity planning by predicting necessary link upgrades and link additions, but it is generally unable to take into account events that are hard to predict, e.g., breaking news, denial-of-service attacks, and failures. These events, which may be typically short-lived but whose impact on the network traffic load is significant, together with the hard to predict traffic due to the server farm based architecture of the Internet will increase the amount of unpredictable traffic. The so-called network lifetime metric, which measures the ability of a network to sustain unexpected changes and shifts in traffic load, is becoming increasingly important. Very recently reported preliminary results show that the widely deployed bidirectional rings provide the smallest network lifetime, whereas chordal rings perform best in terms of network lifetime. In this paper, we first provide extensive numerical investigations of the network lifetime of bidirectional rings for realistic initial traffic scenarios. We then provide more detailed insights into the network lifetime of chordal rings and show that chordal rings not necessarily outperform bidirectional rings. Finally, we examine meshed rings and a novel hybrid ring-star network which clearly outperform not only bidirectional but also chordal rings in terms of network lifetime for a wide range of unexpected traffic changes and shifts