+Flow descriptions should be in \fBnormal form\fR. This means that a
+flow may only specify a value for an L3 field if it also specifies a
+particular L2 protocol, and that a flow may only specify an L4 field
+if it also specifies particular L2 and L3 protocol types. For
+example, if the L2 protocol type \fBdl_type\fR is wildcarded, then L3
+fields \fBnw_src\fR, \fBnw_dst\fR, and \fBnw_proto\fR must also be
+wildcarded. Similarly, if \fBdl_type\fR or \fBnw_proto\fR (the L3
+protocol type) is wildcarded, so must be \fBtp_dst\fR and
+\fBtp_src\fR, which are L4 fields. \fBovs\-ofctl\fR will warn about
+flows not in normal form.
+.PP