R&D&I

Multilayer optical networking is an enabling technology to support the exponential growth of traffic and its dynamicity, with sustainable costs. However, automation and collaboration between IP and optical layers are still on an early stage. One of the reasons is the absence of pure multilayer planning and management solutions considering the network as a whole entity, where layers cooperate with each other, instead of the sum of individual layers providing isolated services. Consequently, operators are typically structured into two different departments to manage IP and optical infrastructures. Moreover, to minimize the interaction between these departments, IP/MPLS networks are often over-provisioned and based on static configurations. In this chapter, we will provide readers a reference framework and methodologies to explore real-world multilayer optical networking techniques in order to analyze their networks, perform "what if??" simulations, and so on.  

The core of the chapter is divided into three main parts. First, the reader will be introduced into the world of multilayer elastic optical networks. On the one hand, a general model for multilayer elastic optical networks will be presented, starting from a generic technology-agnostic. On the other hand, a methodology for network analysis will be discussed, including aspects such as offline vs online scenarios, ILP models vs (meta-)heuristics, and so on. Second, several variants of the multilayer problem will be introduced (regenerator placement, contention-awareness, adaptive modulation, IP routing protocols, survivability, energy-efficiency and so on), giving some tips about modeling of each specific problem, including some pseudo-code for clarification. Finally, some exercises, followed by their solutions, will be proposed in order to validate the knowledge acquired.  

To conclude, the reader will be provided with a corpus of theoretical and practical tools and tips to model and evaluate almost any kind of variant of (single-layer or multilayer) network scenarios, driven through several examples and practical exercises. All software will be released as open-source in sites like GitHub, as an accompanying resource to the chapter. Therefore, practitioners will be able to use this software as a baseline framework to develop their own solution. In fact, one of the key points of the chapter is that, for the first time ever, authors present a framework to model and develop multilayer network scenarios rather than presenting a specific solution for a specific problem, as usual in scientific publications

Software-defined networking (SDN), a present-day alternative to manage and operate data center Ethernet networks, is also considered a promising choice for operating other infrastructures like access, metro and core networks. In this paper, we present the development of an ad-hoc SDN system built up as an extension to the Net2Plan planning tool, targeted to a real-life scenario in a tier-2 network carrier. Architectural decisions taken concerning the use or not of existing controllers (ODL, ONOS) and SDN protocols (OpenFlow, NETCONF) are addressed and we discuss the experience gained from the deployment and pilot test in a real production network.

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 the IP flows is challenging in multilayer IP-over-WDM networks, since traffic routed over IP links depend on the actual sequences of 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 the cases, as 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 a maximum end-to-end latency for IP flows in any of such 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.