http://www.networkdictionary.com/networking/de.php "The physical layer in computer B receives the information unit and passes it to the data link layer. The data link layer in computer B then reads the control information contained in the header prepended by the data link layer in computer A. The header and the trailer are then removed, and the remainder of the information unit is passed to the network layer. Each layer performs the same actions: The layer reads the header and trailer from its peer layer, strips it off, and passes the remaining information unit to the next higher layer." above is a group of sentences in the link . now , "The header and the trailer are then removed" , WHICH HEADER AND TRAILER INFO ? YEAH I SUPPOSE I UNDERSTOOD! look : at layer 2 at the receiving end (for example assume router received the data) transmitting end layer 2 : layer2 header , ip header , tcp/udp header , upper layer headers , upper layer (application) data , layer 2 footer receiving end layer 2 (assume router) : layer 2 header and layer 2 footer ARE STRIPPED OFF then carried to network layer as : ip header , tcp/udp header , upper layer headers , upper layer (application) data and at network layer ip header is stripped off , so THERE IS STILL tcp/udp header , upper layer headers , upper layer (application) data now reliable data communication is possible! AM I RIGHT?