IP metropolitan area network is a multimedia communication network with high bandwidth, multi-function and multi-service access, which is based on IP and ATM telecom technology, and uses optical fiber as the transmission medium, and integrates data, voice and video services.

The metropolitan area network is divided into 3 levels: core layer, convergence layer and access layer:

Core layer: mainly providing high bandwidth service bearer and transmission, and the interconnection with existing network (such as ATM, FR, DDN, IP network), characterized by broadband transmission and high-speed scheduling.

Convergence layer: the main function is to provide the service access nodes to collect and distribute the user service data, and to realize the service level classification of the service.

Access layer: using a variety of access technologies, bandwidth and service allocation, to achieve user access, access node equipment to complete multiplexing and transmission of multiple services.