Date: Wed, 7 Mar 2018 13:33:56 -0700 From: Kevin Bowling <kevin.bowling@kev009.com> To: "Cui, Cheng" <Cheng.Cui@netapp.com> Cc: "freebsd-transport@freebsd.org" <freebsd-transport@freebsd.org>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: why not enable tcp_pmtud_blackhole_detect in default Message-ID: <CAK7dMtAGK_ZLO-06WZAJ4qH5io81mjP4B63hbq_9=hHcth_q2g@mail.gmail.com> In-Reply-To: <E103DBC6-CDF9-4E8C-8069-502261C7158E@netapp.com> References: <E103DBC6-CDF9-4E8C-8069-502261C7158E@netapp.com>
next in thread | previous in thread | raw e-mail | index | archive | help
Cheng, We run this in production at Limelight Networks (i.e toward a broad spectrum of Internet hosts) and must to deal with some uncommon network topology. There are currently some limitations as you point out. Like you say the signaling is not perfect and we do often clamp MSS unnecessarily. There is also no probing to see if we can expand the MSS later. I think those issues should be fixed up before it's enabled by default and I don't know anyone working on it at the moment. Regards, On Wed, Mar 7, 2018 at 8:35 AM, Cui, Cheng <Cheng.Cui@netapp.com> wrote: > Dear all, > > Reading through the tcp blackhole detection code (support RFC 4821) in Fr= eeBSD including the recent bug fixes, I am wondering why is it still not en= abled 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 perfor= mance regression against some false positive blackhole event like a tempora= ry 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_tim= er.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 > > > _______________________________________________ > freebsd-net@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAK7dMtAGK_ZLO-06WZAJ4qH5io81mjP4B63hbq_9=hHcth_q2g>