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[83.245.240.147]) by smtp.gmail.com with ESMTPSA id v28sm1064319lfi.33.2019.04.11.11.28.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Apr 2019 11:28:52 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) From: Jonathan Morton In-Reply-To: Date: Thu, 11 Apr 2019 21:28:51 +0300 Cc: Mikael Abrahamsson , "bloat@lists.bufferbloat.net" Content-Transfer-Encoding: quoted-printable Message-Id: <6889A853-52F2-4554-9450-F59F9CB6B91A@gmail.com> References: <8301D679-FB99-4CB8-8A58-E83B3BA0007D@gmail.com> To: "Holland, Jake" X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Bloat] datapoint from one vendor regarding bloat X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 11 Apr 2019 18:28:54 -0000 > On 11 Apr, 2019, at 9:00 pm, Holland, Jake = wrote: >=20 > MBS =3D maximum burst size > PIR =3D peak information rate > CBS =3D committed burst size > CIR =3D committed information rate Ah, this is enough to map the terms onto my prior knowledge of TBFs. = (In my considered opinion, TBFs are obsolete technology for shaping - = but there is a lot of deployed hardware still using them.) So what this boils down to is a two-stage TBF policer. =46rom idle, = such a system will let a burst of traffic through unfiltered, then start = dropping once the bucket is empty; the bucket is refilled at some = configured rate. The two-stage system allows implementation of = "PowerBoost" style policies. The practical effect is that if there's a 10ms burst permitted, there = may be 10ms of traffic collecting in some downstream dumb FIFO. This = depends on fine details of the network topology, but this is the main = reason I implemented a deficit-mode "virtual clock" shaper in Cake, = which has no initial burst. With that said, 10ms isn't too bad in = itself. A question I would ask, though, is whether that 10ms automatically = scales to the actual link rate, or whether it is pre-calculated for the = fastest rate and then actually turns into a larger time value when the = link rate drops. That's a common fault with sizing FIFOs, too. > Pages 1185 thru 1222 of the referenced doc* are actually really = interesting reading > and an excellent walk-through of their token bucket concept and how to = use it. Nearly 40 pages? I have work to do, y'know! I did just glance through it, and it looks like exactly the sort of = arcane system which ISPs would *want* to leave well alone in its default = configuration, or make only the simplest and easiest-to-understand = changes to. There's obviously a lot of support for Diffserv designed = into it, but nobody really knows how to configure a given Diffserv = implementation to work well in the general case, simply because Diffserv = itself is under-specified. - Jonathan Morton