Two (or more) client devices engage in a chat session. Packets associated with the chat session are numbered using a predetermined pattern. When the packets are received, the receiving client device extracts signals from the packet metadata to determine whether the primary cause of packet loss during transit is network congestion or link losses. Based on the extracted signals, the receiving device sends a control message back to the other client device indicating how one or more chat parameters should be updated. On receiving the control message, the other client device updates the chat parameters accordingly.