PrePrint: Decentralized NIC-switching Architecture Using SR-IOV PCIe Network Device In order to increase the flexibility and bandwidth of intra-rack communication, we propose a decentralized NIC-switching architecture to enable rack-level network bandwidth disaggregation. This is the first solution that uses the built-in switch of SR-IOV-compliant PCIe NICs in Data Center environments to handle the traffic of a rack. We design a decentralized switching topology where a pool of virtual NICs (vNICs) from several SR-IOV-compliant PCIe NICs can be shared among multiple servers in a rack instead of each being permanently designated to a server. To take full advantage of this new architecture, we also develop a mechanism to dynamically assign vNICs to each server and distribute the traffic from each server into the vNICs allocated to it. Utilizing the high bandwidth of PCIe technology, the new architecture provides higher switching capacity and more flexibility than the traditional ToR-centric architecture. In addition, the dynamic allocation of vNICs to servers enables flexible bandwidth adjustment for servers according to traffic demands. As the preliminary stage, this paper focuses on exploiting the unique design point and implements an FPGA prototype to prove the technical feasibility of the proposed architecture.