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

A new physical model of an astronomical object - Black Hole. Presented by the equation for determining the radius of the object, based on the theory of vortex gravitation. Proposed rationale that the black hole mass does not depend on the strength of gravity on its surface. Schwarzschild solution shows a contradiction by definition radius of the Black Hole.

Keywords: Black hole, gravity, vortex, whirlwind..