Flit
Beginner
A small chunk of data, always the same size, sent over a link.
Novice
A fixed-size block (256 bytes in PCIe 6.0) that carries packets plus error-checking bytes. Fixed sizes make it possible to add error correction.
Expert
Flow-control unit. PCIe 6.0’s 256-byte flit holds 236 B of transaction-layer packets, 6 B of data-link payload, 8 B of CRC and 6 B of FEC; CXL 1.x/2.0 uses a 68-byte flit. Flit mode drops per-packet framing and per-packet CRC.