The demands for very high bandwidth transmission equipment and customers' emphasis on network reliability have driven many Telecommunications companies to employ  Synchronous Optical Network (SONET) Rings . SONET technology coupled with physical  self-healing ring  topologies have vastly increased networks' transmission capacities and made network restoration virtually transparent to the customer. This introduction of SONET Rings has created a new phase of telecommunication network design. With the unique characteristics of rings and the highly nonlinear relationship between the demands and the ring capacity required to carry the demands, ring network design is a very challenging problem.
['Victor A. Clincy']
The SONET ring transport planning problem