Situations when RTO occurs even though packets reach receiver

When the ACK sent by the receiver lost and sender could not get the ACK then the RTO occurs. If there is a delay in arriving ACK to the sender due to some reasons (as described below) than RTO occurs even though packets reach receiver. For example, on a low-bandwidth link the arrival of competing traffic (possibly with higher priority), or some other change in available bandwidth, can cause a sudden increase of the RTT. This may cause a RTO. If the communication takes place from a low latency path to a high latency path, it may suddenly increase the RTT beyond the current RTO value.