On Mon, Sep 18, 2017 at 2:29 PM, hiren panchasara <hi...@strugglingcoder.info> 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). just to be clear: 3-dupack (aka RFC3517) is still enabled with RACK enabled. I am experimenting a patch set to disable 3-dupack approach completely.
>> > >> > 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. > > Thanks for your help! > Cheers, > Hiren
