With the development of the whole services

especially the rapid growth of group customer service

the CMCC trunk networking faces new challenge.The traditional SDH（Synchronous Digital Hierarchy） networking mode cannot adjust to the packet service requirements

and the PTN（Packet Transport Network） is capable to adapt IP-based services and inherit the maintenance conception of SDH.However

the PTN is mainly used in MAN（metropolitan area network）.Therefore

constructing a "high-bandwidth

low-cost

strong-performance" network

covering metropolitan and provincial area

is necessary

which can resolve the E2E transport of group customer service

and achieve the high-quality IP-based service bearing requirement.