Omni-Path Fabric uses the Flow Control Digit (FLIT) as its smallest transmission unit. FLITs function as either data FLITs, which carry messages, or control FLITs, which manage various fabric operations.

The system does not transmit data FLITs individually; instead, it groups them into Link Transfer Packets (LTP) containing sixteen FLITs and a CRC field. This approach optimizes bandwidth by requiring only the first FLIT to carry header information and also enhances link reliability through Forward Error Correction and Link Level Retry mechanisms.

Forward Error Correction detects and corrects message errors as they pass through the fabric, preventing packet loss. If an error is unrecoverable, Link Level Retry enables the sending port to resend only the affected LTP from its buffer instead of retransmitting the entire message. This prevents significant performance penalties, as messages often span multiple LTPs.