Abstract

The rapid increase in development of digital communication networks in the mid-1970s started with the introduction of light-wave systems for transmission. Since that time, services have evolved from voice and fax at 64 Kbit/s to Ethernet and to the next Generation of SDH/SONET which offer more such as resiliency, reliability, scalability, built-in protection, management and rerouting which are sometime called Multiservice Provisioning Platforms (MSPP), can offer a combination of data interfaces such as Ethernet, 8B/10B, MPLS or RPR, without removing those for SDH/PDH from its legacy system. This paper overview the evolution PDH/SDH-SONET networks, services, frame formats, difference between PDH/SDH-SONET and next generation SDH-SONET. Keywords: SDH-SONET, PDH/SDH-SONET, communication networks