Apparatus and method for generating decoding instructions for a decoder for decoding data packets from a telecommunications network, each of the data packets having a plurality of fields formatted in a predetermined protocol defined by a protocol specification. The apparatus comprises an input, an instruction generator and an output, the instruction generator receiving an enhanced protocol specification having the protocol specification and application operations attached thereto. The instruction generator analyzes the enhanced protocol specification to determine which fields in a data packet formatted in the corresponding protocol are required in order to enable the application operations to be executed and generates instructions for controlling the decoder to decode the required fields and to execute the particular application instruction.