A new explicit congestion notification scheme for satellite IP networks

Longer transmission delay and higher link errors affect data communication performance over satellite links. The problem gets compounded in case a congestion occurs in the corresponding data path. Taking preventive measures before a congestion actually occurs can help in avoiding such situations. Irrespective of the network characteristics, Explicit Congestion Notification (ECN) either through ICMP messages or through marking packets aims to achieve this objective. However, use of ICMP messages for explicit congestion notification leads to vulnerability to attacks by malicious hosts. On the other hand, use of conventional marking schemes that mark data packets in the forward direction can be slow as they have to traverse the satellite links. In this manuscript, we propose a new mechanism of ECN for an even faster notification of an incipient congestion over satellite IP networks. Our proposal, Mark-Reverse ECN, marks packets corresponding to acknowledgement (ACK) segments in the reverse direction to the sender. This leads to a reduction of the latency between detection and actual notification. As such, our mechanism leads to a more accurate and effective approach to congestion control. In addition, our proposed mechanism is free from vulnerability to malicious attacks. We also develop a new analytical model for Mark-Reverse ECN on TCP Reno for performance prediction and validation of simulation outcomes. Simulation results show that our proposed mechanism (i) leads to up to 25% improvement of TCP performance, (ii) reduces packet loss at the congested router by down to about 0% and (iii) helps to improve the performance of conventional TCP when deployed together.