Proxy stripping: a performance-enhancing technique for optical metropolitan area ring networks

Metropolitan area ring networks can be categorized into metro edge and metro core rings. The traffic characteristics of metro edge and metro core rings are quite different. While metro edge rings exhibit a strongly hubbed traffic pattern (hot spots), traffic demands in metro core rings are much more uniform. We examine the throughput-delay performance of a buffer insertion ring with destination stripping and shortest path routing, which is the favored network type in the new high-performance standard for metropolitan area ring networks, IEEE 802.17 Resilient Packet Ring (RPR), and we investigate the ring's performance limitations under different traffic characteristics by means of analysis and simulation. Our probabilistic analysis considers arbitrary propagation delays, packet length distributions, and traffic matrices. In our numerical investigations we consider uniform, hot-spot, symmetric, and asymmetric traffic demands. Our findings show that the throughput-delay performance of buffer insertion rings deteriorates significantly under hot-spot traffic compared with uniform traffic. To mitigate this drawback, we propose and investigate the novel performance-enhancing proxy-stripping technique. Proxy stripping is used by a subset of ring nodes to send traffic across shortcuts of a dark-fiber star subnetwork. Our results show that proxy stripping dramatically improves the throughput-delay performance of buffer insertion rings not only under uniform traffic but also, in particular, under hot-spot traffic. Finally, we address the trade-offs of the proxy-stripping technique.