+ *
+ * The guarantee we have with timestamps is that all the events in a
+ * packet are included (inclusive) within the begin/end timestamps of
+ * the packet. Another guarantee we have is that the "timestamp begin",
+ * as well as the event timestamps, are monotonically increasing (never
+ * decrease) when moving forward in a stream (physically). But this
+ * guarantee does not apply to "timestamp end", because it is sampled at
+ * commit time, which is not ordered with respect to space reservation.