Marking algorithm of distinguishing three traffic load states with two encoding states for pre-congestion notification

Pre-congestion notification (PCN) gives an early warning of congestion by marking packets to protect the quality of service of inelastic flows. PCN defines two rates per link: admissible rate (AR) and supportable rate (SR), which divide the PCN traffic load into three states, “no pre-congestion,” “AR pre-congestion,” and “SR pre-congestion.” PCN admission control and flow termination control operate in accordance with these three states. However, only two PCN encoding states, unmarked and PCN marked, can be used due to the requirement of PCN encoding to survive tunneling through a currently used IPsec tunnel. We propose a marking algorithm, which uses the two encoding states, for distinguishing the three states of PCN traffic load. We also propose new admission and flow termination controls, which are based on the proposed marking algorithm, and evaluate their performance. Markings that require fewer PCN encoding states are preferable because the remaining encoding state can be used for a newly added PCN-based control in the future. Furthermore, distinguishing more states with fewer encoding states benefits not only PCN but also general marking techniques because header fields are limited; thus, valuable.