With the advent and applications of Generalized Multi-Protocol Label Switching (GMPLS: an optical extension to traditional Multi-Protocol Label Switching), today's optical networks evolve towards Intelligent Optical Network (ION). In this paper we firstly describes a novel IP-Centric optical network architecture called Hierarchical Optical Routing Switching Architecture (HORSA) based on GMPLS--a flexible, highly scalable IP over WDM optical network architecture for the delivery of public network IP services. Two kinds of node including Optical Core Router (OCR) and Optical Edge Router (OER) are involved in this optical network architecture. In this section we also discuss some issues such as routing, signaling and management of HORSA. Secondly, we mainly focus on the design issues of OCR and OER including multi-granularity switching fabrics, intelligent OTU, control plane software and etc. Finally, we reach conclusions that HORSA based on GMPLS is suitable for current hybrid network environment and optimistic for IP traffic transfer, it can be scaled to pure optical IP over WDM architecture based on Optical Packet Switch (OPS).
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