Optical transport networks have been traditionally based on ring architectures, relying on standardized ring restoration protocols such as SONET BLSR and UPSR to achieve fast restoration (50 msec). However, many carrier core networks are indeed meshed, consisting of backbone nodes interconnected by point-to- point WDM fiber links in a mesh interconnection pattern. Given this realization, and the many operational drawbacks of ring-based networks (such as provisioning across multiple rings, stranded capacity, inflexibility to handle traffic forecast uncertainties), it is therefore not a surprise that carriers have evolved, or are considering evolving, their core network architecture from ring to mesh. Such mesh networks are based on next-generation Optical Cross-Connects (OXCs) that support fast, capacity-efficient shared path restoration. There has also been interest in intermediate architectures (for example, those improving on traditional span-based restoration  or based on “p-cycles” ) that also try to achieve the speed of ring restoration in ways more closely aligned with traditional ring architectures. As mesh networks are replacing ring-based networks, operators are faced with changes in the way they operate their network. The increased efficiency and robustness of mesh networks, compared to ring-based networks, has to be managed appropriately to actually achieve those benefits. In this paper, we discuss four key economic and operational benefits from mesh optical networking. They are (1) end-to-end routing and provisioning, (2) fast and capacity-efficient restoration, (3) re-provisioning, and (4) re-optimization. They contribute in various ways to network cost savings and higher network and service reliability in mesh networks compared to traditional ring-based networks.
© 2004 Optical Society of AmericaPDF Article
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