The RTO metric helps to identify packet loss and to locate the congested links. Using this information, we pinpointed the problem quickly, allowing for a nearly immediate mean time to resolution (MTTR). Because the Reveal(x) UI allows for easy drill-down, we were able to quickly determine that the majority of the RTOs could be traced to a single blade enclosure and two specific server instances. We looked at the data together, and sure enough, during traffic spikes, the RTO metric would climb to approximately eight million.
He asked us to help him validate and analyze the data. In a real-world example, we received a call from one of our customers about a very high number of RTOs on some key servers. Reveal(x) spots RTOs by simulating the TCP state machines at the endpoints of the connection and inferring when problems occur, detecting issues such as bad congestion avoidance, Nagle delays, and PAWS drops. These retransmission timeouts add up to significant problems for network and application performance and certainly require some tuning and optimization. We've seen sites that show millions of RTOs in a 24-hour window, with one million RTOs translating to 277 hours of application delay. As a result, an RTO causes, at minimum, a one-second delay on your network. After some amount of time, usually at least one second, the sender cautiously starts sending again, testing the waters with just one packet at first, then two packets, and so on.
An RTO occurs when the sender is missing too many acknowledgments and decides to take a time out and stop sending altogether. Typically, they don't pose much of a problem as the retransmission timer counts down, the packets are resent, and the network continues to hum along.Ī retransmission timeout (RTO), on the other hand, is quite a different beast. TCP retransmissions occur on the network all the time. If there is no acknowledgment for the data in a given segment before the timer expires, then the segment is retransmitted. TCP starts a retransmission timer when an outbound segment is handed down to IP. One of the most important of these performance metrics quantifies TCP retransmission timeouts (RTOs), which create havoc for network and application performance. Reaveal(x) captures a lot of application performance metrics. What are they and what can you do about them? Let's talk about retransmission timeouts (RTOs).
0 kommentar(er)
