1. A system for accessing and transmitting data frames of different types in a digital transmission network, comprising: at least one user-network interface coupled with a user-network; at least one network-network interface coupled with the digital transmission network to transfer data; at least one mapping/demapping device; a virtual interface device coupled with said at least one user-network interface and with said at least one network-network interface via said at least one mapping/demapping device; and a control device coupled with said virtual interface device to control other corresponding devices to perform different types of data frame processing flows, said control device comprising: a data processing and dispatching device, comprising: at least one inter-device interface for inputting and outputting data frames; a data processing and dispatching unit coupled with said inter-device interface for inputting and outputting data frames; a processing flow database, storing a plurality of processing flows, coupled with said data processing and dispatching unit, wherein each processing flow comprises data frame type number and inter-device interface number; and a control interface unit coupled with said processing flow database and said data processing and dispatching unit so as to control a virtual private processing unit and a rule database to process the data frames; wherein said data processing and dispatching device is adapted to: extract type number from received data frames; search for corresponding processing flows in said processing flow database corresponding with the extracted type number; determine the retrieval result, discarding the data frames if it is blank and ending the process; if the search result is not blank, then an inter-device interface number is extracted from the search result; and the data frames are output via the inter-device interface with said inter-device interface number; and wherein the correspondence between said processing flows and data frame types is 1:1, and the data processing and dispatching unit is adapted to find the corresponding processing flows according to the data frame types and informs said corresponding devices to process the data frames according to the corresponding processing flows.