Distributed computing systems, devices, and associated methods of packet routing are disclosed herein. In one embodiment, a computing device includes a field programmable gate array (“FPGA”) that includes an inbound processing path and outbound processing path in opposite processing directions. The inbound processing path can forward a packet received from the computer network to a buffer on the FPGA instead of the NIC. The outbound processing path includes an outbound multiplexer having a rate limiter circuit that only forwards the received packet from the buffer back to the computer network when a virtual port corresponding to the packet has sufficient transmission allowance. The outbound multiplexer can also periodically increment the transmission allowance based on a target bandwidth for the virtual port.