With the rapid development of the network, how to effectively reduce the dynamic delay and improve the performance of the network is an important and challenging problem. Specifically, network congestion is one of the key factors that hurt the network performance, so real-time detection of the network congestion is critical for recovering the network failure quickly. Current research in congestion detection mainly faces the problems of occupying extra bandwidth, decreasing the ratio of the effective payload of the packet, increasing the burden of the switches, etc. In this paper, we apply flow watermarking to network congestion detection and propose a fine-grained network congestion detection method based on flow watermarking. We also combine it with the eBPF (extended Berkeley Packet Filter) to improve the performance of congestion detection. Theoretical analysis and experimental results show that the changes in network status can be reflected in real-time and accurately in the watermark decoding information. The network congestion detection based on flow watermarking can detect network status on a small time scale and realize low-overhead and easily deployed congestion detection.

The hierarchical structure of the data center network is more and more unsuitable for increasing east-west traffic from virtual machines. Reconfigurable circuit switching is utilized to reduce regional hotspots, which causes the problem of routing oscillation. We propose a stratospheric network of the data center, which combines virtual circuit switching and Tor switches. It acts as a supplement to tropospheric transmission across the hierarchical structure to alleviate global hotspots. The link of VCS (Virtual Circuit Switching) is divided into virtual channels by time division, and packets are sliced into cells to be transmitted at a specific time slot. Via the direct connection and the relaying of VCS modules, the stratospheric network could support not only the sharing of uplinks between Tor switches but also dynamical forwarding. Experiments of parameter servers demonstrate that it accelerates the transmission of data, which could provide a direct and fast path, especially for east-west traffic.

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