There are provided a transparent performance enhancing proxy, a method for operating a transparent performance enhancing proxy between a source device and a destination device, and corresponding computer program product. The method includes preserving, without translation, packet header information of a header for a packet received from the source device to be forwarded to the destination device. The method further includes during a transmission control protocol connection setup phase for the packet, preserving transmission control protocol connection semantics. The method also includes during a transmission control protocol data transfer phase for the packet, running a transmission control protocol by masquerading as the source device to the destination device and masquerading as the destination device to the source device to transmit the packet to the destination device with the preserved packet header information.