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Re: Protocol for TCP heartbeats?

2010-06-25 13:37:53
Rémi Denis-Courmont wrote:

What I had in mind whether there ever been an attempt to define dynamic
keepalive algorithm that adjusts keepalive intervals according to the
observed throughput and roundtrip latency figures (dynamic in the same
way as CC dynamically adjusts throughput).

Any ideas?

You can probably change the values. But I don't really see the statistical correlation of throughput and round trip time to the probability that the peer will fail within a certain time interval.

I mean, you can probably establish a weak correlation between them, or at least between the variation of the bandwidth and RTT to the probability of failure. But I somehow doubt it will be sufficiently strong a correlation that that a very clever algorithm would be significantly better than a plain dumb ping-pong at constant or exponential backoff interval.

What I meant was that long timespan between consecutive packets can mean either:

1. Sender is sending data sparsely.
2. There's congestion on the network and packet loss causes decrease in throughput.

In both cases you want to increase the heartbeat interval as none of them means the peer is dead.

Dead peer or unreachable peer is rather identified by sharp decrease in throughput -- actually no packets from the peer for unexpectedly long time.

Martin


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