Protection of the existing investment for Multi-Service Transport Platform(MSTP) equipment and smooth evolution from MSTP networks to Packet Transport Networks(PTN) platform are common concerns for telecom operators.In connection with this issue
this paper investigates the packetization of the existing MSTP equipment to upgrade it to an enhanced MSTP(MSTP+) with dual-plane functions of TDM and PTN
and analyzes the system architecture of dual-core MSTP+ and the scheme for its networking with PTN equipment.The conclusion is that the hybrid networking of dual-core MSTP+ backward compatible with PTN is the optimal solution to the protection of the existing network investment.