STR application in the NTT network

Summary form only given, as follows. NTT has proposed a hybrid controlled dynamic routing scheme, state- and time-dependent routing (STR). The purpose of STR is to achieve high performance despite unpredictable real-time traffic fluctuations with minimum changes to switching software and operations systems. STR uses an appropriate combination of the two kinds of control, centralized and distributed. In the STR network, a set of alternate routes between each origin-destination node pair is determined on a time-dependent basis by a control center using a centralized control method. For call-level routing, state-dependent routing is achieved by using a distributed control method to determine an alternate route for each overflow call. Such distributed control routing schemes are now being called event-dependent routing. In 1992, the transition to a dynamic routing network, the STR network, began in the Tokyo metropolitan area. The extension of this STR network to the NTT long-distance network was completed in 1995. So far, the network has proven to be robust against traffic variation and facility failure. In the NTT long-distance network, the new network control and administration system has also been developed and implemented. This system aims at realizing efficient flow-through among control, administration and engineering processes. The processes for generating and controlling routing patterns for STR are carried out in this system. The author gives an overview of STR and the current STR network. It then describes the performance of STR with some examples from the NTT network and issues facing the STR network.