| Summary: | The unexpected growth of cloud services lead to a dramatic increase in the network capital expenditure (CAPEX) and latency in geographically distributed inter-datacenter networks. In this paper, an adaptability analysis is proposed on CAPEX and forwarding delay for IP switching and optical transport network (OTN) switching in distributed inter-datacenter networks. By abstracting the switching behavior of the IP routers and OTN equipment, the IP nodes, and OTN nodes are mapped to the switching matrix of CLOS switching network. A unified network-level connection model is established based on CLOS switching network to meet the needs of connectivity. Then, the hardware costs and the forwarding delay are evaluated to find out the bandwidth threshold (BDT) which decides the most suitable switching mode for a specific switching granularity. The adaptability of IP switching and OTN switching under different switching granularities and port rates is performed based on the simulation platform in terms of hardware cost, optical port cost, and forwarding delay. Simulation results show that the BDT based on hardware cost is 280 Mbps when switching granularity is 1.25 Gb/s. For 2.5 Gb/s switching granularity, when average bandwidth between multiple datacenters is higher than 600 Mbps, OTN switching has more advantages than IP switching on capital expenditure, especially when port rate of the equipment is high. In addition, the simulation results also verify that the forwarding delay is reduced obviously with OTN switching.
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