arXiv:2504.04404v3 Announce Type: replace Abstract: Hardware accelerators are essential for meeting microsecond-scale demands in distributed applications, but invoking them over the network remains bottlenecked by host software. Host-mediated paths (RPC, RDMA) still rely on the CPU to reassemble requests and launch accelerators, which dominates end-to-end latency, while packet-level offload on SmartNICs lacks any notion of a complete request. We introduce the Remote Accelerator Call (RAC) paradigm, in which transport ingestion, request reassembly, dispatch, and accelerator invocation are handled entirely in hardware. We build fRAC, a hostless prototype that implements this network-to-accelerator interface as a lightweight shim on an FPGA hosting multiple virtualized accelerators, reconfigurable at runtime in a few milliseconds. Serverless functions backed by fine-grained accelerators are a natural fit, since host-mediated invocation overhead can match or exceed their short execution times. fRAC achieves under 7.8us end-to-end latency while sustaining application throughput of up to 90 Gbps. Compared to highly optimized DPDK-based CPU and DPU baselines, it achieves at least 80% lower latency under saturation, while consuming 85% less power.