information providers act as sources of information consisting of a plurality of variable length messages and issue control packets , enabling / disabling packets and data packets . each data receiver has a unique address as a permanent attribute . the enabling / disabling packets selectively enable or disable a specific data receiver or a specific group of data receivers . therefore to avoid that the loss of the enabling / disabling packet leads to the loss of the corresponding whole set of packets , each data receiver stores data packets for later use in the re - establishment of the entire set of transmission packets . however , only data packets provided by any friend information provider are managed by the data receiver . then when , during a re - transmission , a enabling / disabling packet related to the information stored into the data receiver is received , such information is immediately made available to the user of the data receiver , without waiting for its complete re - transmission .