Hi Jesper,
On June 11, 2015 1:16:15 PM GMT+02:00, Jesper Dangaard Brouer <[email protected]> wrote: > >On Sat, 6 Jun 2015 16:29:15 +0200 Sebastian Moeller <[email protected]> >wrote: > >> On Jun 6, 2015, at 15:38 , Kevin Darbyshire-Bryant ><[email protected]> wrote: >> >[...] >> > The problem I have is setting outbound rate limiting. I was hoping >> > that 'cake' without the 'bandwidth' parameter would work on the >> > 'backpressure' from the ATM(?) driver, sadly this wasn't the case >> > and so setting a bandwidth limit (I'm not in a position to test the >> > new keywords for ATM encapsulation etc yet) was the only way >> > forward. >> >> This is rather important to get right, ATM’s arcane 48/53 >> encapsulation only leaves 100*48/53 = 90.5% of the sync rate for >> useable bits, and even those need to contain all the headers specific >> to your line (plus AAL5’s unfortunate choice of fitting each packet >> into an integer number of ATM cells), mean that without AQM taking >> the link layer encapsulation into account you need to aim for roughly >> 80-85% of the sync rates on and ATM link. With a link that disappears >> often I currently would recommend sqm-scripts as weapon of choice >> (you should be able to get cake into sqm-scripts) as the IFB needs to >> be set up again after the “connected” interface reappears, which >> current sqm-scripts should do for you... > >That is true, the ATM overhead on ADSL is very important to get right >for your ratelimiting work as intended (that is you gain control over >the queue). > I want to add that Jesper was essential in teaching the Linux kernel to properly account for all the quirks in the ATM/aal5 Linklater. So we are standing on his shoulders, so to speak ;) to be able to see as far as we do... His original thesis is still findable under http://www.adsl-optimizer.dk/ and certainly worth reading for ATM "sufferers". >The iproute2 "tc" have supported option "linklayer atm" and "overhead" >for quite some time now (since 2008). All the rate_tables based >schedulers (e.g. HTB, TBF) have these options. > >There is also the more generic "stab" that allow linklayer adaptation >to >work for any qdisc. See man tc-stab [1] Cake has its own independent implementation of per-packet-overhead and atm-celling accounting, in the spirit of making shaper setup easy for mortals. Sqm-scripts allows to select which of the link layer accounting methods to use and calls them htb_private and tc_stab I believe. Best Regards Sebastian -- Sent from my Android device with K-9 Mail. Please excuse my brevity. _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
