+.IP \fBdec_ttl\fR
+Decrement TTL of IPv4 packet or hop limit of IPv6 packet. If the
+TTL or hop limit is initially zero, no decrement occurs. Instead,
+a ``packet-in'' message with reason code \fBOFPR_INVALID_TTL\fR is
+sent to each connected controller that has enabled receiving them,
+if any. Processing the current set of actions then stops.
+However, if the current set of actions was reached through
+``resubmit'' then remaining actions in outer levels resume
+processing.
+.