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You don't need 5% packet loss on a high latency 1Gbps link to trash performance. Even .1% packet loss is enough to cut throughput massively on long fat networks
by Scaevolus 7y ago
You don't need 5% packet loss on a high latency 1Gbps link to trash performance. Even .1% packet loss is enough to cut throughput massively on long fat networks (LFNs).
Erasure coding helps, but it demands much more CPU than simply having a very wide window for retransmits. For bulk data transfer of files, retransmitting any part of a 1GB window is trivial.
- traverseda 7y agoYou mean with raptorQ 5% loss trashes performance by more than 5%?
- phonon 7y agoNo, the overhead is fairly minimal. A 5% packet loss (which is very bad) on a gigabit link where the sender is thousands of miles away might have an effective throughput of 930 mbits per second with RaptorQ. With regular TCP you would get only a few megabits/s, as it would back down until the loss rate was nearly zero.
- phonon 7y agoYes, of course--even a low rate of packet loss where the bandwidth delay product is high will cause you to end up with throughout dropping to critically terrible levels. Tweaking TCP can help, but a high performance RaptorQ system can work at packet loss levels that TCP could never handle.