This for Vivek:
SNCP and MSSP are the protections schemes in SDH.
SNCP – SubNetwork Connection Protection –> is a dedicated protection mechanism that can be used to protect a protion of a path (between two NE) or the full end-to-end path.
MSSPRing – Multiplex Section Shared Protection (could be 2Fibre or 4Fibre) Ring –> In this mode, instead of one section, the whole ring is duplicated (both Tx and Rx) in order to have protection. By doing so, the equipments effective usable capacity will be reduced to half.
if you need more, try to read some white papers, articles or the main source ITU-T recommendation G841 – protection structures. The ITU-T paper is not a free one.