Network interface cards (NICs) are fundamental componentsof modern high-speed networked systems, supporting multi-100 Gbpsspeeds and increasing programmability. Offloading computation from aserver’s CPU to a NIC frees a substantial amount of the server’s CPU resources, making NICs key to offer competitive cloud services.

Therefore, understanding the performance benefits and limitations of offloading anetworking application to a NIC is of paramount importance.In this paper, we measure the performance of four different NICs fromone of the largest NIC vendors worldwide, supporting 100 Gbps and200 Gbps. We show that while today’s NICs can easily support multihundred-gigabit throughputs, performing frequent update operations ofa NIC’s packet classifier — as network address translators (NATs) andload balancers would do for each incoming connection — results in adramatic throughput reduction of up to 70 Gbps or complete denial ofservice. Our conclusion is that all tested NICs cannot support high-speednetworking applications that require keeping track of a large number offrequently arriving incoming connections. Furthermore, we show a variety of counter-intuitive performance artefacts including the performanceimpact of using multiple tables to classify flows of packets.