If you can immediately identify where you're losing packets and locate the congested links, pinpointing and fixing the root cause becomes a lot easier. By tapping into your wire data, you can track RTO metrics and correlate them with traffic spikes in order to quickly figure out what's causing the timeouts. (Click those links to learn more about each of these common network issues!)Īnother method is to access your environment's wire data, or all the communications on the network itself. One way to spot RTOs is to simulate the TCP state machines at their endpoints, and then infer when problems occur in order to detect issues like bad congestion avoidance, Nagle delays, PAWS drops, and excessive tinygrams. 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. 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.Īs a result, an RTO causes, at minimum, a one-second delay on your network. An RTO occurs when the sender is missing too many acknowledgments and decides to take a time out and stop sending altogether.

So What Are Retransmission Timeouts?Ī retransmission timeout (RTO), on the other hand, is quite a different beast. This actually happens all the time, and typically doesn't cause much of a problem: as the retransmission timer counts down, the packets are resent, and the network continues to hum along. When an outbound segment is handed down to an IP and there's no acknowledgment for the data before TCP's automatic timer expires, the segment is retransmitted.

TCP ( the Transmission Control Protocol) connects network devices to the internet.

What are they and what can you do about them? What Is TCP Retransmission? In an effort to rid the world of needless application and network performance slowdowns, we turn to retransmission timeouts (RTOs).

Tcp retransmission wireshark