The FIX protocol is a standard for messages about trading (orders, executions, quotes, market data, allocations) between firms, maintained by the FIX Trading Community, with a session layer that delivers them in order and without loss. In its tag-value encoding a message is a sequence of fields tag=value, each ended by the byte SOH (value 1), where the tag is a number from the protocol’s dictionary and the value is text.
| standing for the SOH delimiter. BodyLength and CheckSum are computed over the spans shown; a receiver recomputes both and rejects the message if either differs.