A method of performing a real-time classification of a data stream exchanged between a client and a server over a telecommunications network, comprises: receiving a data segment of the data stream indicating a data offset; updating a bitmap table with the received data segment, wherein the bitmap table comprises a number of blocks of data, the data blocks being ordered by block sequence numbers in the bitmap table; after updating the bitmap table, performing measurements on a complete data block to obtain at least one measurement result without waiting for all the data blocks having block sequence numbers that are lower than the first block sequence number to be completed; performing a statistical analysis based on measurement results obtained for several complete blocks; classifying the data stream into one group among a plurality of groups, based on the performed statistical analysis at least.