Date: Wed, 7 Mar 2018 15:35:11 +0000 From: "Cui, Cheng" <Cheng.Cui@netapp.com> To: "freebsd-transport@freebsd.org" <freebsd-transport@freebsd.org> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: why not enable tcp_pmtud_blackhole_detect in default Message-ID: <E103DBC6-CDF9-4E8C-8069-502261C7158E@netapp.com>
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Dear all, Reading through the tcp blackhole detection code (support RFC 4821) in FreeBSD including the recent bug fixes, I am wondering why is it still not enabled in default? Given the fact that this implementation was a merge from xnu, and the xnu has enabled it in default, do we have a plan to enable it in default? Or is there any concern about the side-effect from it as performance regression against some false positive blackhole event like a temporary link flap, which is long enough to trigger a lower MSS but shorter than 6 RTO? https://opensource.apple.com/source/xnu/xnu-1456.1.26/bsd/netinet/tcp_timer.c.auto.html << enabled in macOS 10.6 https://reviews.freebsd.org/rS322967 << bug fixes https://reviews.freebsd.org/rS272720 << merge from xnu Thanks, --Cheng Cui NetApp Scale Out Networking https://netapp-meeting.webex.com/meet/chengc
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