A SmartNIC is a programmable device that connects a server’s CPU complex to a network. A composable SmartNIC adds enhanced flexibility, which means that everything between the raw Ethernet interface and the PCI Express bus to the host CPU cores can be completely and dynamically reconfigured while packets are in flight.
Most SmartNICs or DPUs on the market are built around a single application-specific integrated circuit (ASIC), with the best examples being the NVIDIA Bluefield and Intel’s Mt. Evans. While these SmartNICs include programmable CPU cores to assist in packet processing, their architectures are fixed. As a result, their packet-processing pipelines are very well-defined, highly optimized, and cast in silicon. If composability is desired, then these approaches are too rigidly designed.