The Role of Switching in Reducing Network Port Counts

We consider the role of switching in minimizing the number of electronic ports (e.g., SONET ADMs) in an optical network that carries sub-wavelength traffic. Providing nodes with the ability to switch traffic between wavelengths, such as through the use of SONET cross-connects, can reduce the required number of electronic ports. We show that only small switches at multiple switching nodes are needed for significant reductions in the number of ports. We provide a lower bound on the number of electronic ports that is a function of the number of switching nodes. We show that our lower bound is relatively tight by providing routing and grooming algorithms that nearly achieve the bound. For uniform traffic, we show that the number of electronic ports is reduced when the number of switching nodes used is approximately equal to the number of wavelengths of traffic generated by each node. Finally, we provide a general upper bound on the amount of switching required in the network. For uniform traffic, our bound shows that as the size of the network increases, each traffic stream must be switched at most once (at one of the switching nodes) in order to achieve the minimum port count.