What is a NIC?
A Network Interface Card (NIC) implements the Physical layer (L1) and part of the data link layer (L2).
It processes packets to and from the CPU, by turning packets → bits through PCIe on Egress, and bits → Packets over PCIe.
| Part | End Host |
|---|---|
| CPU | Application |
| CPU | Transport |
| CPU | Network |
| CPU/NIC | Data Link |
| NIC | Physical |
However, CPUs haven’t gotten faster at processing packets (Linux can process about 1M pps), but links are around 400 Gbps now, and they’re lagging behind NICs speed.
Smart NICs
Smart NICs eschew that with a Programmable Domain-Specific Hardware Processor on the NIC.
Currently, they are generally
- Field Programmable Gate Arrays (FPGAs)
- Multi-core Systems on chip (SoCs)
FPGAs have small configurable logic and memory boards, which can be assembled to meet a certain workload. This requires a bit of a different model of programming than other popular software programming.
SoCs have a small computer on a chip, which has small processing cores and a memory hierarchy, and moreso resembles a computer.
| FPGAs | Multi-Core SoCs | |
|---|---|---|
| Hardware Architecture | Reconfigurable | Fixed |
| Programming Model | Verilog | C-like |
| Performance | Higher throughput lower latency | Lower throughput higer latency |