Efficient Network Switching Hierarchy

History and economics have set the stage for the move to grooming at 2.5 Gbps granularity in the core of optical mesh networks. The evolution of core grooming speeds to the STS-48 granularity level is a continuation of a cycle that began with the introduction of narrowband cross-connects into the network over 20 years ago. Since then, cross-connect grooming granularity has increased from 64 Kbps, to 1.5 Mbps, 51.8 Mbps, and finally to 2.5 Gbps with the introduction of ultra-broadband cross-connects in 2000. History has shown that switching and grooming speeds increase as transport speeds increase (Figure 1). The primary reasons for scaling grooming speeds with transport speeds are improved network scalability, performance and, most importantly, cost. History has also shown that product designs are specialized in terms of capacity, scalability, reliability, performance and cost, for particular segments of the network. Network segmentation and specialization is why products designed for the edge do not perform well in the core. Based on the facts stated in this paper, many carriers and industry experts have concluded that an optimal network architecture supports hierarchical transport and grooming speeds, with faster switching (granularity) speeds in the core of the network than at the edge. A hierarchical architecture, with segment specialized products, will persist in the network future just as it has in the past. Figure 1: History has shown that switching and grooming speeds increase as transport speeds increase