DIFFSERV COMPATIBLE EXTENDED PAUSE (DIFFPAUSE) FOR FAIR CONGESTION CONTROL IN METRO-ETHERNET

This paper presents a novel scheme called DiffPause for congestion control that is highly scalable, robust, and compatible with the assured forwarding (AF) of the differentiated services (DiffServ) model for high-speed Metro Ethernet. The IEEE 802.3x (.3x) PAUSE message is extended to support class and color (drop precedence) of the packets for transient congestion control. The DiffPause introduces an early warning threshold (EWT) such that the upstream nodes can reduce the outgoing rate and throttle the aggressive traffic aggregates, thereby providing fair bandwidth allocation. Further, the DiffPause scheme takes into account the dominant color of packets in a congested buffer. In addition, the scheme takes advantage of per link-based back-pressure mechanism without any bandwidth reservation and is independent of the number of ongoing individual sessions, thus leading to high scalability. The simulation studies demonstrate the superior performance of the DiffPause scheme over the existing color-blind .3x. Results further show that, on an average, with less than 15% extra PAUSE messages in comparison to the .3x scheme, the DiffPause achieves substantial improvement in the fairness, throughput and low delay for lower drop precedence packets.