Guaranteeing traffic survivability and latency awareness in multilayer network design

The massive adoption of real-time Internet services (e.g., online gaming or video streaming) is threatening the way in which operators and service providers design and operate their networks. New requirements, such as maximum latency, are becoming de facto indicators to measure network quality, complementing the classical requisites of fault tolerance to increase network availability. However, finding fault-tolerant designs that also limit the end-to-end latency of IP flows is challenging in multilayer IP-over-WDM networks, since traffic routed over IP links depends on the actual sequences of the traversed fibers and how they change in each failure state. Despite its practical importance, the research on joint optimization of end-to-end latencies and fault tolerance in multilayer optical networks is minimal. In this context, this paper presents a planning algorithm for multilayer IP-over- WDM (with OSPF-ECMP routing in the IP layer), considering both survivability and end-to-end latency awareness. Three versions of the algorithm are provided, assuming three different recovery mechanisms in the optical layer: 1 + 1 lightpath protection, unprotected lightpaths, and lightpath restoration. In all cases, as is customary, the optical layer is assumed to react first to the failures, and after that, the IP/OSPF layer adapts to the surviving topology. The aim of our algorithm is to design minimum cost networks that guarantee not only 100% survivability under some representative failure states, but also the maximum end-to-end latency for IP flows in the case of any failures. According to our results, a careful and holistic design may achieve both objectives simultaneously, without, in most cases, noticeable side effects in terms of cost and/or throughput. In its turn, we see that, when end-to-end latencies are not considered, designs tend to produce very high latencies in some flows and failure states.