Congestion Control In Resilient Packet Ring

Using IP as the generic protocol and high-speed links for transmission, has become the trends of network communication. As the junction of WAN and Access Network, MAN has to meet the requirement of them. A packet-based network is relatively facility, efficient and cheap. Its application is moving from LAN into WAN. There are several hopeful technologies for new MAN: IP over ATM, Gbits/10Gbits Ethernet, IP over SDH, and Resilient Packet Ring (RPR). As a new MAN technology, RPR solves the problems faced by SDH and Ethernet successfully, and becomes the research focus. The packet ADM nodes in RPR use fibers with Spatial Reuse mechanism, and eliminate the demand for reserved protection bandwidth, therefore highly improve bandwidth utility. Since RPR allocates bandwidth at the level of entire ring, not individual node, it implements a global fairness easily. RPR have a natural resiliency advantage because of its good restore mechanism. It supports QoS and ensures the transmission delay of real-time services.Realizing spatial reuse and fairness allocation simultaneously is a main object of RPR. Congestion control has variable mechanisms because of the diversity of environments. And RPR pays special requirements on congestion control algorithms. The existing algorithms have some defects of performance. This paper presents a new algorithm DFAR-BF. This algorithm achieves fairness and high utilization, as well as quickly convergence. It also resists oscillation under unbalance flow scenarios.According to the trend of MAN development and the cases we faces, the paper summarizes the key demands of MAN designing, and provides a design. This design uses two fibers to transmit packets, supports a large quantity of nodes, and has an extensible topology. It capsulates data as Ethernet->SRP->GFP, and eliminates SDH layer. As an experiment of EoF (Ethernet over Fiber), it achieves high performance with modest price. The design has 4 level QoS levels, ensuring the transmission of real-time services. With IPS mechanism, it realizes restoration less than 50 ms.Finally, we discuss the design of the core chip. This chip realizes packet ADM functions for Ethernet and serial data, ensures the QoS of real-time services, gets a high bandwidth utility of outer SSRAM, so it can work stably even under the situations that all ports reach their peak rates.