On 09/18/17 at 02:29P, hiren panchasara wrote: > On 09/18/17 at 02:18P, Eric Dumazet wrote: > > On Mon, 2017-09-18 at 13:14 -0700, hiren panchasara wrote: > > > Hi all, I am trying to disable rack to see 3dupacks in action during > > > loss-detection but based on the pcap, I see that it's still trigger > > > loss-recovery on the first SACK (as if RACK is still enabled/active). > > > > > > Here is what I did to disable rack: > > > net.ipv4.tcp_recovery = 0 > > > > > > I've also disabled metrics: > > > net.ipv4.tcp_no_metrics_save = 1 > > > And also flushed existing entries with 'ip tcp_metrics flush' just to be > > > on a safer side. > > > > > > Not really relevant here but I've also switched to reno. > > > > > > I am on: 4.10.0-33-generic > > > pcap: https://transfer.sh/mfoiN/reno_no_rack.pcap > > > > > > What am I missing? I can provide any additional info. > > > > > > Cheers, > > > Hiren > > > > > > A single SACK can contains enough information to trigger a retransmit. > > Bah, right. FACK! > > > > If you absolutely want to see the old 3 dupack in action, you also want > > to disable SACK. > > I believe net.ipv4.tcp_fack = 0 would achieve that without disabling > sack.
Ah, what you probably meant was that this could still be < 3 dupacks triggering loss-recovery based on reordering. I believe I got what I was looking for. Thanks a ton, Hiren
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