During data packet transmission, data pack ets can be damaged or not forwarded by overloaded routers. Other data packets cannot be delivered to the recipient or only after considerable delay times. Such damaged data packets are discarded and do not bring their useful data to the recipient.
Especially in real-time services such as Internet telephony or video conferencing, delayed data packets or packet loss degrade image and voice quality. Subsequent insertion of delayed data packets is not possible in real-time applications. In voice and video transmission, the loss of individual data packets is not necessarily perceptible, but it does degrade voice quality. The same applies to the delay of data packets. For voice transmission, the ITU-T has specified the packet loss rate( PLR) for voice quality in Recommendation G.114. According to this, a packet loss rate of up to 5% is hardly noticed.
There are various techniques to compensate for packet loss and the resulting consequences. One of these techniques is Forward Error Correction( FEC), which is used at the physical layer and the network layer. The other is Packet Order Correction( POC), which ensures that data packets arrive in the correct order. However, there are also applications that must operate completely lossless and where no data packets may be discarded. For example, backups in storage systems. Such applications are realized with Lossless Ethernet.