The Open System Interconnection (OSI) protocol suite is comprised of numerous standard protocols that are based on the OSI reference model. These protocols are part of an international program to develop data-networking protocols and other standards that facilitate multivendor equipment interoperability. The OSI program grew out of a need for international networking standards and is designed to facilitate communication between hardware and software systems despite differences in underlying architectures.
The OSI specifications were conceived and implemented by two international standards organizations: the International Organization for Standardization (ISO) and the International Telecommunication Union-Telecommunications Standards Sector (ITU-T).
Optical Transport Networks are widely deployed. Originally used to provide high-capacity links between major network nodes or few end users with large bandwidth capacity, optical is now flooding metropolitan and residential networks. The Optical Transport networks become more and more a mass market. The management of such equipment has been built using the network based on an ISO implementation between NMS (network managmenent system) and NEs (Network Elements).
The Legacy SONET/SDH equipment or NMS Platform are so largely deployed that telecom manufacturer still required support, upgrade or evolution of a complete OSI solution.