// if sequence numbers are unexpected.
	FlagStateless

	// FlagPayloadIsErr can be used by individual ops to signify that
	// The payload is a string error converted to byte slice.
	FlagPayloadIsErr

	// FlagPayloadIsZero means that payload is 0-length slice and not nil.
	FlagPayloadIsZero

	// FlagSubroute indicates that the message has subroute.
	// Subroute will be 32 bytes long and added before any CRC.
	FlagSubroute
)