A method for determining a transmission parameter at an interface between nodes of a transmission system for a specific channel, where there exist a plurality of channels between the nodes serving either for communication between the nodes or for communication with a subscriber, first determines whether the transmission parameter relates to a protocol for communication between nodes or a protocol for communication with the subscriber. If the protocol is for communication between nodes, then the particular protocol is determined by analyzing octets of data and awarding points to one or the other of such protocols, the protocol with the most points corresponding to the transmission parameter. If the protocol is for communication with the subscriber, then the particular protocol corresponding to the transmission parameter is determined by analyzing length of header information data, direction of data flow and number of bits in a specified location.