Self-healing Network Applications

Network down-time can be very expensive to business customers like those in the financial world. Self-Healing Networks (SHNs) immediately detect service-affecting problems and respond to ensure service continuity to minimize the down-time experienced by a customer. Three approaches to SHNs are in use: route diversity, dualfed rings, and reconfigurable rings. Route diversity uses the protection switching capabilities integrated in the hardware of AT&T's lightwave systems (like FT Series G and DDM-1000 in asynchronous networks and FT-2000 and DDM-2000 in SONET networks) to provide instantaneous restoration hm performance degradation or facility failures by routing the Service and protection lines on physically diverse paths. Dud-fed rings also provide instantaneous restoration from performance degradation or facility failures on a DS1 or DS3 basis independent of the transport rate and format, and the vendor of the lightwave system. In reconfigurable rings, digital cross-connect systems (such as AT&T's DACS III-2000 and DACS IV2000) are used to reroute the tr& around failures. Reconfigurable rings provide SHNs in today's asynchronous network as well as in mixed async/SONEI' and multivendor networks by managing "gateway" vehicles. Operations of a multi-location multi-vendor network in the present and evolving SONET environment will be greatly facilitated through the use of a network management and control system such as DACScanm 2000 controller, both for day-today centralized provisioning and maintenance, and for restoration from network disasters. SHN capabilities become more important in the SONET network which is by definition fiber-based and canies higher bit rates than today. The SHN approaches must be easily deployed during the transition to SONET as well as in full SONET networks. AT&T's 2000 Product Family provides complete interworking with network elements currently deployed and maintains transparency for today's SHN features in the SONET network. SHN capabilities will be improved in the SONET network by leveraging off the SONET standard itself. Examples of additional capabilities that enhance the present self-healing network in the 2000 Product Family include faster restoral time, end to end performance monitoring, and enhanced fault isolation capabilities. Other capabilities, such as