Cost Savings and Robustness Improvements in IP-over-DWDM Core Networks by Employment of CD-ROADMs and Advanced Multilayer Survivability Schemes

Abstract:
Today’s IP Core Networks typically use A/B-Plane protection for all service classes (disregarding best effort and high-QoS classes). Enabled by Colorless and Directionless Remotely Configurable Optical Add/Drop Multiplexers (CDROADMs) new technologies offer increased flexibility on the optical layer. In addition to reducing operational expenditures, the flexible optical layer can be used to offer differentiated multilayer resilience combining classical IP protection with optical restoration in IP-over-Optical networks. In this paper the authors evaluate IP-over-DWDM core network architectures. Four scenarios are considered: (i) an adjacent IP core network as today’s reference with opaque lightpath termination at any intermediate WDM terminal, (ii) a fully meshed IP core network with transparent lightpaths between all IP node pairs, and (iii) a multilayer optimized network with selective bypass between node pairs. These three network scenarios are assumed to use a classical IP A/B-plane network design, where links in each plane are loaded with maximum 50%, so that in case of any failure in a single plane, the traffic can be rerouted over the surviving plane. Compared to the above three scenarios is (iv) a novel multilayer resilience scheme, where IP A/B-plane protection is combined with optical layer restoration. The IP protection is employed for high-quality traffic, whereas the slower optical restoration is used for the best-effort traffic survivability. The four scenarios are evaluated based on a 14 node German reference network defined in [2]. In addition to guidelines for the cost-efficient IP topology design of multilayer IP-over- DWDM core networks, the authors show that in case of the German backbone reference network the combination of IP A/B-plane protection with optical restoration requires 24 - 27% fewer line interfaces compared to the multilayer optimized bypass network design.