Flit – Flow control unit or digit – this is a unit of data that is a packet of data in a packet-switched network connection between nodes (network routing points) when the message is being transmitted at link level. A header flit, which contains the packet’s destination address, is followed by body flits containing the data payload, and a final tail flit. This contains information used to close the connection between the two nodes.

A flit can be accepted or rejected at the receiving node based on a flow control protocol and the size of the receiving buffer.