> 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’. 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 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) > > 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. > 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 GPG fingerprint: 012C ACB2 28C6 C53E 9775 9123 B3A2 389B 9DE2 334A
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