OTN and PTN joint networking model is an advanced model to achieve the unified bearing of 3G and full-services

witch has become the major solution in building the next generation metro transport network

especially for some small and medium sized metro transport networks. However

in the face of large or super-scaled MAN（Metropolitan Area Network）

the original model reveals certain limitations. According to the development needs of MAN

a few bottlenecks of the original model are analyzed in this paper

some new ideas

such as RNC partition

the addition of core dispatching equipments are proposed to optimize the original model structure and enhance its scalability

maintainability and manageability for operators

which provides a strong reference for the formation of large and super-scaled metro transport networks.