Hi Kevin, hi Mark, Kevin is 100% right!
> On Dec 17, 2017, at 20:23, Kevin Darbyshire-Bryant > <[email protected]> wrote: > > > >> On 17 Dec 2017, at 15:23, Sebastian Moeller <[email protected]> wrote: >> >> Hi Mark, >> >>> On Dec 17, 2017, at 11:45, Mark Captur <[email protected]> wrote: >>> >>> My setup is as follows >>> >>> vdsl2 modem doing pppoe itself and nat to 10.x.x.x -> lede master eth0.2 >>> (wan static ip in modem's DMZ) eth0.1 (lan) doing nat to 192.168.1.x >>> >>> Here is my current SQM config >>> config queue 'eth1' >>> option debug_logging '0' >>> option verbosity '5' >>> option qdisc 'cake' >>> option qdisc_advanced '1' >>> option ingress_ecn 'ECN' >>> option egress_ecn 'NOECN' >>> option qdisc_really_really_advanced '1' >>> option script 'layer_cake.qos' >>> option interface 'eth0.2' >>> option enabled '1' >>> option eqdisc_opts 'nat rtt 50000 bridged-ptm dual-srchost diffserv4' >>> option upload '2400' >>> option linklayer 'ethernet' >>> option overhead '8' >>> option squash_dscp '1' >>> option squash_ingress '1' >>> option iqdisc_opts 'nat rtt 50000 bridged-ptm dual-dsthost' >>> option download '0' >>> >>> config queue >>> option debug_logging '0' >>> option verbosity '5' >>> option download '0' >>> option qdisc 'cake' >>> option script 'layer_cake.qos' >>> option qdisc_advanced '1' >>> option squash_dscp '0' >>> option squash_ingress '0' >>> option ingress_ecn 'ECN' >>> option qdisc_really_really_advanced '1' >>> option egress_ecn 'ECN' >>> option interface 'eth0.1' >>> option enabled '1' >>> option eqdisc_opts 'nat rtt 50000 bridged-ptm dual-dsthost diffserv4' >>> option upload '30000' >>> option linklayer 'ethernet' >>> option overhead '8' >>> >>> Is the overhead correct? should i use the bridged-ptm keyword (or should i >>> use pppoe-ptm). > > > Beware of using option linklayer ‘ethernet’ without option > linklayer_advanced ‘1’ & option linklayer_adaptation_mechanism ‘default’. Or > use linklayer ‘none’. I guess "linklayer cake" would be better than none... > Failure to do so will make sqm-scripts use STAB for the link accounting (in > essence it lies to cake about the size of packets being passed through it). > Better to use cake’s built-in compensation - fewer modules, less code. I agree, even though for ptm this is less dire than for ATM; still use linklayer default or linklayer cake. > > I was bitten by this myself very recently, lost 4 hours of my life & many > recompiles before I realised an innocent looking setting (linklayer_advanced) > was messing with the packet size (seen by looking at max_len from tc) I am beginning to wonder whether the attempt to hide complexity behind linklayer_advanced is not simply misguided and should be jettisoned... > >> >> The overhead certainly seems confusing. Personally, I dislike the >> overhead related compound keywords like *-ptm and would recommend the >> following: >> 1) remove the bridged-ptm from the eqdisc/iqdisc fields >> 2) add "mpu 64" to the eqdisc/iqdisc fields >> 3) set overhad to 8+18+4 = 30 bytes (you will need to account for everything >> added on the bottleneck, so your packets will be MTU 1492, to leave room for >> the PPPoE header that the modem adds). > MTU 1492 ain’t necessarily so - some vdsl modems in bridge mode support RFC > 4638 with baby jumbo frames, thus supporting the normal ethernet MTU of 1500 > (and obviating the need to TCP MSS clamping) - ie. if you can do it, you > should ;-). You still need to account for the 8 byte PPPOE overhead of > course. And again, Kevin is correct; my rationale might have been faulty but the recommendation still was correct though ;)... >> 4) DO not set the ptm keyword at all, instead make sure to set the shaper >> bandwidth to <= sync bandwidth * 64/65 = sync bandwidth * 0.984615384615 (to >> account for ptm's 64/65 encoding _without_ incurring needless operations per >> packet). >> >> 4) tell us about your ISP and plan ;) >> > Cheers, > > Kevin D-B Thanks for your input, as always very much appreciated! Best Regards Sebastian > > GPG fingerprint: 012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A _______________________________________________ Cake mailing list [email protected] https://lists.bufferbloat.net/listinfo/cake
