Negative packetloss happens when your packets are being received out of order, timewise. You send data to the server as a series of packets, each packet has a time stamp which tells the receiving service (either the server or the client, depending on which originally sent it) when the packet was sent. So your client sends a packet to the server, it doesn't wait for the server to receive and confirm it, it just sends the next packet as though the previous had been received as normal. So the first packet goes through the internet along a different path than the second packet. assume that the first packet is taking a longer route to the server than the second. The client has not yet received confirmation of the server recieving the first packet, so it decides to send it again. This second packet goes along the path of the second of the original 2 packets. Eventually the server receives all 3 packets. In the client's eyes, it sent 3 packets when only 2 were needed in the server's eyes, so technically it's not LOSING packets, its actually gaining them along the way. In this example, you would experience -50% packetloss. But chances are that your packets are being received out of order, so the server can't really use them as efficiently or possibly as accurately and you may experience lag if the difference is large.