Method for determining link characteristics of a network link including: selecting or configuring one or more existing network traffic packets with one or more requirements when necessary, wherein the one or more requirements include a receiving network node having knowledge about the packets it should receive; transmitting the selected one or more network traffic packets from a transmitting network node to the receiving network node; and examining the transmitted selected one or more network traffic packets to determine the link characteristics of a network link between the transmitting network node and the receiving network node, according to said knowledge about the packets.