/**
- * Queue and pass message to core when possible.
+ * @brief Queue and pass message to core when possible.
+ *
+ * If type is payload (UNICAST, TO_ORIGIN, MULTICAST) checks for queue status
+ * and accounts for it. In case the queue is full, the message is dropped and
+ * a break issued.
+ *
+ * Otherwise, message is treated as internal and allowed to go regardless of
+ * queue status.
*
* @param cls Closure (type dependant).
* @param type Type of the message, 0 for a raw message.