Protection of RPR strict order traffic

Resilient packet ring (RPR, IEEE 802.17) is designed with a protection mechanism aiming at restoring traffic on the ring within 50 ms in case of a link or node failure. However, the total experienced disruption time often exceeds this if strict order delivery of packets is required, since a 40 ms (configurable from 10 ms to 100 ms) topology stabilisation timer is used to avoid packet reordering. In this article, we present three alternative ways to avoid packet reordering for strict order traffic in RPR networks. The three suggested methods are discussed analytically, and simulations are used to compare their performance. Our simulation results suggest that the new methods give up to 90% reduction in packet loss during a failure situation compared to the current RPR standard