On Wed, 19 Oct 2022 14:33:28 -0700 (PDT) David Lang via Bloat <bl...@lists.bufferbloat.net> wrote:
> On Wed, 19 Oct 2022, Stuart Cheshire via Bloat wrote: > > > On Mon, Oct 17, 2022 at 5:02 PM Stuart Cheshire <chesh...@apple.com> wrote: > > > >> Accuracy be damned. The analogy to common experience resonates more. > > > > I feel it is not an especially profound insight to observe that, “people > > don’t like waiting in line.” The conclusion, “therefore privileged people > > should get to go to the front,” describes an airport first class checkin > > counter, Disney Fastpass, and countless other analogies from everyday life, > > all of which are the wrong solution for packets in a network. > > the 'privileged go first' is traditional QoS, and it can work to some extent, > but is a nightmare to maintain and gets the wrong result most of the time. A lot of times when this is proposed it has some business/political motivation. It is like "priority boarding" for Global Services customers. Not solving a latency problem, instead making stakeholders happy. > AQM (fw_codel and cake) are more the 'cash only line' and '15 items or less' > line, they speed up the things that can be fast a LOT, while not > significantly > slowing down the people with a full baskets (but in the process, it shortens > the > lines for those people with full baskets) > > >> I think the person with the cheetos pulling out a gun and shooting > >> everyone in front of him (AQM) would not go down well. > > > > Which is why starting with a bad analogy (people waiting in a grocery > > store) inevitably leads to bad conclusions. > > > > If we want to struggle to make the grocery store analogy work, perhaps we > > show > > people checking some grocery store app on their smartphone before they > > leave > > home, and if they see that a long line is beginning to form they wait until > > later, when the line is shorter. The challenge is not how to deal with a > > long > > queue when it’s there, it is how to avoid a long queue in the first place. > > only somewhat, you aren't going to have people deciding not to click on a > link > because the network is busy, and if you did try to go that direction, I would > fight you. the prioritization is happening at a much lower level, which is > hard > to put into an analogy > > even with the 'slowing' of bulk traffic, no traffic is prevented, it's just > that > they aren't allowed to monopolize the links. > > This is where the grocery store analogy is weak, the reality would be more > like > 'the cashier will only process 30 items before you have to step aside and let > someone else in', but since no store operates that way, it would be a bad > analogy. Grocery store analogies also breakdown because packets are not "precious" it is okay to drop packets. A lot of AQM works by doing "drop early and often" instead of "drop late and collapse". > > >> Actually that analogy is fairly close to fair queuing. The multiple > >> checker analogy is one of the most common analogies in queue theory > >> itself. > > > > I disagree. You are describing the “FQ” part of FQ_CoDel. It’s the “CoDel” > > part of FQ_CoDel that solves bufferbloat. FQ has been around for a long > > time, > > and at best it partially masked the effects of bufferbloat. Having more > > queues > > does not solve bufferbloat. Managing the queue(s) better solves bufferbloat. > > > >> I like the idea of a guru floating above a grocery cart with a better > >> string of explanations, explaining > >> > >> - "no, grasshopper, the solution to bufferbloat is no line... at all". > > > > That is the kind of thing I had in mind. Or a similar quote from The > > Matrix. > > While everyone is debating ways to live with long queues, the guru asks, > > “What > > if there were no queues?” That is the “mind blown” realization. > > In a world where there is no universal scheduler (and no universal knowlege > to > base any scheduling decisions on), and where you are going to have malicious > actors trying to get more than their fair share, you can't rely on voluntary > actions to eliminate the lines. > > There are data transportation apps that work by starting up a large number of > connections in parallel for the highest transfer speeds (shortening slow > start, > reducing the impact of lost packets as they only affect one connection, etc). > This isn't even malicious actors, but places like Hollywood studios sending > the raw movie footage around over dedicated leased lines and wanting to get > every bps of bandwidth that they are paying for used. > > David Lang _______________________________________________ Cake mailing list Cake@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/cake
