FYI, when I looked at Steam traffic a few years ago it was very bursty, meaning that there is nothing transmitted for a short period and then there's a burst that uses up all link bandwidth for a short while. Internet was unusable without limiting Steam downloads quite a lot.
Now I don't have that problem anymore. Cake's ingress mode works almost as well as I have expected (still need to set bw about 1Mbps lower on a 20Mbps link - but that's ok). Maybe the Steam CDN now also uses a saner network scheduler (like fq with pacing). I'd guess so anyway. On 22 Apr 2017 11:36, "Jonathan Morton" <chromati...@gmail.com> wrote: > >> So please add “atm overhead 32" to cake on eth0 or “atm overhead 40” to > cake instances on pppoe (these packets do not have the PPPoE header added > yet and hence appear 8 bytes to small). > > > > Thanks for your help, will definitely use them. Just wondering if I use > "pppoe-vcmux/bridged-llcsnap" on eth0 or "pppoe-llcsnap" on pppoe0 would > have the same effect? Or are there some other "under-the-hood" changes when > using them? > > On the pppoe interface, use pppoe-vcmux if your modem is set to use > VC-MUX, or pppoe-llcsnap if it’s set to use LLC-SNAP (they might be > described using slightly different terms, but should still be recognisable > as one or the other). This probably depends on your ISP, and may further > vary regionally within the same ISP. > > I really prefer to use the self-explanatory keywords (which is why I added > them in the first place) instead of opaque magic numbers. This is a point > on which Sebastian has long disagreed with me. > > >> Question: if you set the shaper’s to 50% of line rate (8.75/0.5?) do > you still see that unfairness? And if you add “atm overhead 40” to cake on > pppoe0 and set the shaper to 90% of line rates (15.75/0.9) how does the > Steam affect per-host fairness? Also how transient are these connections > team uses? > > > > Actually did more testing about this and it seems that as far I have set > the bandwidth to ~15Mbps (so ~15% less of my max speed) and use the "nat" > parameter, the per-host fairness works even without the "dual-host" and > "overhead" parameters. I definitely find this very interesting, is this > behaviour caused by the way Steam downloads games? > > By default, Cake uses triple-isolate mode, which uses information about > both source and destination hosts to perform per-host isolation; this > usually works well regardless of which side of the connection has the LAN > hosts. The “dual” modes let you specify that fact explicitly, making it a > little more robust and predictable. > > Without overhead compensation, Cake will actually use more of the physical > link than it thinks it does - by default it only accounts for raw IP or > Ethernet packets, depending on the type of interface it’s attached to. > With full-size packets as in a bulk download, the difference is relatively > small, so the 15% margin is just about sufficient to make things work. But > with small packets mixed in, the difference grows, such that Cake might no > longer control the bottleneck with some traffic mixes. > > The “conservative” keyword I recommended earlier (which is exactly > equivalent to Sebastian’s recommendation of “atm overhead 48”) reverses > that situation; Cake will then always end up using *less* of the physical > link than it accounts for, which is safe for troubleshooting with. The > keyword is there specifically so that we do’t have to figure out the > precise overhead profile before tackling more substantive issues. > > At any rate, it has nothing to do with Steam specifically. > > >> As far as I can tell cake can drill down to the required IP/TCP/UDP > fields independent of whether there are VLAN tags or PPPoE headers so cake > should not care (except for the different overhead specifications you need > to add as stated above). BUT if instantiated on eth0 cake will see pppoe > LCP packets and might decide to drop them, which can take down the link, so > out of caution I would still instantiate on pppoe in your case. > > > > Yeah, with further testing it seems the interface wasn't the culprit but > I'll still do all my testing on pppoe0 just to be safe. > > > > Anyway I was wondering if there's some kind of manual for Cake and the > various parameters, I'm looking to set it up best way possible but there > are some parameters which I'm not sure what they do (one of them being > "ingress”). > > With the correct version of iproute2 installed, just issue “man tc-cake”. > That’s the official documentation. > > Currently it doesn’t have the ingress keyword yet. That’ll be fixed soon. > > > Also while reading on the bufferbloat.net Cake page I noticed a > possible "fix" for BitTorrent (by setting it as "background", > https://www.bufferbloat.net/projects/codel/wiki/Cake/#diffserv-support), > I'm wondering if this can be done with Steam too? > > It’s possible, if you can figure out which traffic is Steam in the first > place, and write filters to match on it. This is complicated by the fact > that Valve runs a sophisticated CDN to handle their rather impressive > bandwidth load. > > - Jonathan Morton > > _______________________________________________ > Cake mailing list > Cake@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/cake >
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