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Some fuzzy thinking in here. "A heartbeat sent from a node in California to a monitor in Virginia might take 80 milliseconds under normal conditions, but could
by jeffbee 1y ago
Some fuzzy thinking in here. "A heartbeat sent from a node in California to a monitor in Virginia might take 80 milliseconds under normal conditions, but could spike to 200 milliseconds during periods of congestion." This is not really the effect of congestion, or at best this sentence misleads the reader. The mechanism that causes high latency during congestion is dropped frames, which are retried at the protocol level based on timers. You can get a 200ms delay between two nodes even if they are adjacent, because the TCP minimum RTO is 200ms.
- toast0 1y agoCongestion manifests as packet queueing as well as packet dropping. 120 ms would be a lot of queuing, especially if we assume the 1000 node cluster is servers on high bandwidth networks, but some network elements are happy to buffer that much without dropping packets. You could also get a jump to 200 ms round trip if a link in the path goes down and a significantly less optimal route is chosen. Again, 120 ms is a large change, but routing policies don't always result in the best real world results; and while the link status propagates, packets may take longer paths or loop.