1. An input/output (I/O) device that provides congestion management for processing nodes, the I/O device comprising: a management controller interface to provide managed services for a plurality of processing nodes coupled to the I/O device; a plurality of network switching interfaces to provide network accessibility for the processing nodes; a storage interface to provide data storage for the processing nodes; a component controller interface to provide legacy functionality for the processing nodes; and a plurality of Peripheral Component Interconnect Express (PCIe) multifunction modules, wherein the multifunction modules are enumerated as a PCIe multifunction device of a particular bus in a PCIe configuration space of an associated processing node, wherein the multifunction modules include: a processing node interface including a PCIe interface enumerated in the PCIe configuration space as the particular bus and that provides a single I/O access point for the associated processing node; a first PCIe endpoint enumerated in the configuration space as a first PCIe function number of the PCIe multifunction device and coupled to the management controller interface, such that the management controller interface provides managed services for the associated processing node; a second PCIe endpoint enumerated in the PCIe configuration space as a second PCIe function number of the PCIe multifunction device and coupled to one of the plurality of network switching interfaces, such that the one network switch into provides network accessibility to the associated processing node; a third PCIe endpoint enumerated in the PCIe configuration space as a third PCIe function number of the PCIe multifunction device and coupled to a remote direct memory access (RDMA) block, such that the RDMA block provides node-to-node accessibility to the associated processing node; a fourth PCIe endpoint enumerated in the PCIe configuration space as a fourth PCIe function number of the PCIe multifunction device and coupled to the storage interface, such that the storage interface provides a storage capability for the associated processing node; and a fifth PCIe endpoint enumerated in the PCIe configuration space as a fifth PCIe function number of the PCIe multifunction device and coupled to the component controller interface, such that the component controller interface provides a legacy functionality for the associated processing node.