A congestion control scheme called dual-layer congestion control (DLCC) is proposed for use when transporting Internet traffic over optical-packet-switched networks. It further reduces the core optical buffering requirement over existing proposals; indeed each optical core switch is assumed in the modeling work to have a shared optical buffering capacity of only 20 optical packets for all ports. Furthermore, it does not depend for its operation on having a certain number of Transmission Control Protocol (TCP) flows carried over each link. The scheme is designed to operate in conjunction with an edge-smoothing algorithm that segments IP datagrams into fixed-length optical slots to be carried by the core. It expedites the response of TCP to congestion in the optical core network, both by reducing the rate of packet transmission over the optical packet core and by throttling TCP sources via the transmission of additional triple duplicate ACK segments. Packet loss performance and edge-buffering capacity requirements are evaluated through mathematical analysis, showing that the packet loss rate can be decreased through the use of DLCC by a factor of up to six times and also showing that electronic edge-buffering requirements are reduced through the use of DLCC. Furthermore, simulation modeling shows that DLCC yields a TCP goodput improvement of between 2 and 10 times, depending on the volume of background User Data Protocol (UDP) traffic and the round-trip time. This demonstrates that DLCC is viable and enhances network performance.
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