Congestion control for virtual-connection using a Smith predictor in high-speed Gigabit Ethernet networks

Recently, FDDI (Fiber Distributed Data Interface) has come under pressure from switched Gigabit Ethernet in the enterprise backbone. In high-speed Gigabit Ethernet networks, traffic is expected to be highly bursty. In particular, whenever data flows from the high-speed link to the low-speed one, congestion commonly occurs. The Virtual-Connection Network (VCN) is a switch-based network capable of implementing cell-based connections, link-by-link flow-controlled connections, and single- or multi-destination virtual connections. Virtual connections described differ from the virtual channel in the ATM literature in that virtual connections have link-by-link flow control and can be multi-destination. VCN's support both connection-oriented and connectionless data link layer traffic. Therefore, the worst collision scenario in Ethernet CSMA/CD with virtual collision brings about end-to-end delay. The goal is to guarantee the performance with respect to bandwidth and latency for selected VCs with different propagation delay, To this end, we propose a classical proportional controller plus a Smith predictor to overcome instability accompanying increased round-trip delays as well as to avoid cell losses. The proposed control policy is illustrated by a simulation study.