Update comments.

core/federated/RTI/rti_common.c

@@ -462,7 +462,7 @@ void update_all_downstreams(scheduling_node_t* node) {
   }
 }
 
-tag_t get_dnet_candidate(tag_t received_tag, tag_t minimum_delay) {
+tag_t get_dnet_candidate(tag_t next_event_tag, tag_t minimum_delay) {
   // (A.t, A.m) - (B.t - B.m)
   // B cannot be NEVER_TAG as (0, 0) denotes no delay.
   // Also, we assume B is not FOREVER_TAG because FOREVER_TAG delay means that there is no connection.
@@ -475,13 +475,13 @@ tag_t get_dnet_candidate(tag_t received_tag, tag_t minimum_delay) {
   //     ii)  If A.t >= B.t > 0 and A.m >= B.m return (A.t - B.t, UINT_MAX)
   //     iii) If A.t >= B.t > 0 and A.m < B.m return (A.t - B.t - 1, UINT_MAX)
 
-  if (received_tag.time == NEVER || lf_tag_compare(received_tag, minimum_delay) < 0)
+  if (next_event_tag.time == NEVER || lf_tag_compare(next_event_tag, minimum_delay) < 0)
     return NEVER_TAG;
-  if (received_tag.time == FOREVER)
+  if (next_event_tag.time == FOREVER)
     return FOREVER_TAG;
-  tag_t result = {.time = received_tag.time - minimum_delay.time,
-                  .microstep = received_tag.microstep - minimum_delay.microstep};
-  if (received_tag.microstep < minimum_delay.microstep) {
+  tag_t result = {.time = next_event_tag.time - minimum_delay.time,
+                  .microstep = next_event_tag.microstep - minimum_delay.microstep};
+  if (next_event_tag.microstep < minimum_delay.microstep) {
     result.time -= 1;
     result.microstep = UINT_MAX;
   } else {

core/federated/RTI/rti_common.h

@@ -256,18 +256,6 @@ tag_t earliest_future_incoming_message_tag(scheduling_node_t* e);
  */
 tag_t eimt_strict(scheduling_node_t* e);
 
-/**
- * Return true if the node is in a zero-delay cycle.
- * @param node The node.
- */
-bool is_in_zero_delay_cycle(scheduling_node_t* node);
-
-/**
- * Return true if the node is in a cycle (possibly a zero-delay cycle).
- * @param node The node.
- */
-bool is_in_cycle(scheduling_node_t* node);
-
 /**
  * For the given scheduling node (enclave or federate), if necessary, update the `min_delays`,
  * `all_upstremas`, `num_all_upstreams`, and the fields that indicate cycles.  These fields will be
@@ -286,27 +274,52 @@ void update_min_delays_upstream(scheduling_node_t* node);
 void update_all_downstreams(scheduling_node_t* node);
 
 /**
- * Find the tag g that is the latest tag that satisfies lf_tag_add(g, minimum_delay) < received_tag.
- * This function behaves like the tag subtraction, received_tag - minimum_delay.
+ * Find the tag g that is the latest tag that satisfies lf_tag_add(g, minimum_delay) < next_event_tag.
+ * This function behaves like the tag subtraction, next_event_tag - minimum_delay.
  * minimum_delay cannot be NEVER.
- * @param received_tag
- * @param minimum_delay
+ *
+ * This function is called in function downstream_next_event_tag.
+ * @param next_event_tag The next event tag of a downstream node.
+ * @param minimum_delay The minimum delay between the target upstream node and the downstream node.
+ */
+tag_t get_dnet_candidate(tag_t next_event_tag, tag_t minimum_delay);
+
+/**
+ * @brief Determine whether the specified scheduling node is needed to receive a downstream next event tag (DNET),
+ * and, if so, return the details.
+ *
+ * This function is called upon receiving a NET from one of the specified node's downstream nodes.
+ *
+ * This function calculates the minimum tag M over
+ * all downstream scheduling nodes of the most recent NET from that node minus the "after delay" (see function
+ * get_dnet_candidate). If M is earlier than the startup tag, then set the result as the NEVER_TAG.
+ *
+ * @param node The target node that may receive a new DNET.
+ * @param node_sending_new_net_id The ID of the node that sends a new NET. If this node's new NET does not
+ * change the DNET value, we can exit this function immediately. If it does, we have to look up the target node's
+ * downstream federates to compute the exact new DNET value.
+ * @return If needed, return the tag value. Otherwise, return the NEVER_TAG.
  */
-tag_t get_dnet_candidate(tag_t received_tag, tag_t minimum_delay);
+tag_t downstream_next_event_tag(scheduling_node_t* node, uint16_t node_sending_new_net_id);
 
 /**
+ * Notify a downstream next event tag (DNET) signal to the specified scheduling node.
  * @param e The target node.
  * @param tag The downstream next event tag for e.
  */
 void notify_downstream_next_event_tag(scheduling_node_t* e, tag_t tag);
 
 /**
- * @param node The target node that may receive a new DNET.
- * @param node_sending_new_net_id The ID of the node that sends a new NET. If this node's new NET does not
- * change the DNET value, we can exit this function immediately. If it does, we have to look up the target node's
- * downstream federates to compute the exact new DNET value.
+ * Return true if the node is in a zero-delay cycle.
+ * @param node The node.
  */
-tag_t downstream_next_event_tag(scheduling_node_t* node, uint16_t node_sending_new_net_id);
+bool is_in_zero_delay_cycle(scheduling_node_t* node);
+
+/**
+ * Return true if the node is in a cycle (possibly a zero-delay cycle).
+ * @param node The node.
+ */
+bool is_in_cycle(scheduling_node_t* node);
 
 /**
  * For the given scheduling node (enclave or federate), invalidate the `min_delays`,

include/core/federated/network/net_common.h

@@ -675,9 +675,10 @@ THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  * from the RTI in centralized coordination.
  * The next eight bytes will be the timestamp.
  * The next four bytes will be the microstep.
- * This message from the RTI tells the federate the tag of the earliest event on the
- * downstream federate's event queue. In other words, this federate doesn't have to send
- * LTC and NET messages earlier than this tag.
+ * This signal from the RTI tells the destination federate the latest tag that
+ * the federate can safely skip sending a next event tag (NET) signal.
+ * In other words, the federate doesn't have to send NET signals with tags
+ * earlier than or equal to this tag unless it cannot advance to its next event tag.
  */
 #define MSG_TYPE_DOWNSTREAM_NEXT_EVENT_TAG 26