From owner-freebsd-net@freebsd.org Wed Mar 7 20:33:58 2018 Return-Path: Delivered-To: freebsd-net@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8A7EDF2DE42 for ; Wed, 7 Mar 2018 20:33:58 +0000 (UTC) (envelope-from kevin.bowling@kev009.com) Received: from mail-it0-x234.google.com (mail-it0-x234.google.com [IPv6:2607:f8b0:4001:c0b::234]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 19FEB6CA91 for ; Wed, 7 Mar 2018 20:33:57 +0000 (UTC) (envelope-from kevin.bowling@kev009.com) Received: by mail-it0-x234.google.com with SMTP id e64so5061844ita.5 for ; Wed, 07 Mar 2018 12:33:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kev009.com; s=google; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=tHTZgNc1ofQDcImm2Vf8mE8hJzGHHIprG9RoOGs/SNI=; b=Fyr8J/JGSFOTQ8zQdJ8UvjlixJNkjRraaSmU7IC98t414UHqndq2Zriipsmxn7oFzR abVaFJGdjkH44jlnyESE5YF9QqLSOljBHqxIxo4wSkcO698cEY+mAVRCJgNgXDHhaW8x l5vYd69/fTqRr4/hD0ot3c9Ob3o7KNy3ao6SM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=tHTZgNc1ofQDcImm2Vf8mE8hJzGHHIprG9RoOGs/SNI=; b=B5l6viJgci7OBGsClwMVWQpzioOb38k48FPNvwggJ6PVNjI97YYz6QCHENh/tt0jEW Kflioy5lbnuSEyUkeKvjHi1bO4S5cuVCpP//qMECiIlD1HrwDKvBGaeYCudhx9HWl1+C qgUHsIv6HPOcwsKUSOlbqOB29qE9EkcG975BKUEomav+SH6+6AUcCd9Du6x3tEGHPPlg J6qD+6tDxXBrsYf4mzYKbGyUM7ferYdm5cXxSOFOUeipsAqs5O+CF3Jg0mWy8MOojyyR lK6OjOmNAJ43sMeZImOh1T6PAVg9Jec2jZXIiV278RcfQsZHOO0buHDtTx7HMZdq5FqT RP/Q== X-Gm-Message-State: AElRT7EEJJojAmorOdU7EOfV/5RdB5xmYCbCIWMRNQgOh6dgqzTsVAmA 5ENNbmqjpDIOC47CCJrJQoPbExAWdxpJTZuvXEr5SQ== X-Google-Smtp-Source: AG47ELu+oaRBJeQETM3n45BF5wxcCJxCeRkz7Yd40H34Vo8PYp3CCP03OKS3PXr9I78lWuTSp9yQFcYorHtwJ/rBkMI= X-Received: by 10.36.250.70 with SMTP id v67mr23334450ith.99.1520454837210; Wed, 07 Mar 2018 12:33:57 -0800 (PST) MIME-Version: 1.0 Received: by 10.2.181.72 with HTTP; Wed, 7 Mar 2018 12:33:56 -0800 (PST) In-Reply-To: References: From: Kevin Bowling Date: Wed, 7 Mar 2018 13:33:56 -0700 Message-ID: Subject: Re: why not enable tcp_pmtud_blackhole_detect in default To: "Cui, Cheng" Cc: "freebsd-transport@freebsd.org" , "freebsd-net@freebsd.org" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 07 Mar 2018 20:33:58 -0000 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 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"