From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Furniss Date: Sun, 30 May 2004 07:40:25 +0000 Subject: Re: [LARTC] HTB MPU Message-Id: <40B98FE9.7010408@dsl.pipex.com> List-Id: References: <40A37E1B.8060604@dsl.pipex.com> In-Reply-To: <40A37E1B.8060604@dsl.pipex.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org Jason Boxman wrote: > On Friday 28 May 2004 14:54, Andy Furniss wrote: > > >>Reading your other post I see your small traffic is ~100b - this would >>use three cells, so as a temporary kludge you could set your mpu to 159 >>and see how it goes. >> >>AFAIK the author of the HTB patch is looking into modifying it to do the >>sums properly for DSL. There isn't one answer though - Eds' formula is >>fine doing the cells bit, but before this you need to add a ppp overhead >>to the IP packet length and this varies with pppoa+vc mux/pppoe/bridged >>pppoe and probably other varieties of dsl implementations. > > > But there's no tried and true method of determining that information? > > You mention at least three methods of mangling PPP with Ethernet/ATM. And the > overhead of each kind of setup also would vary depending on the specifics of > that setup? (i.e., knowing you have bridged PPPoE doesn't instantly qualify > you as having an overhread of 123i.) > > Sounds particularly complicated. > > But the overhead would be a fixed cost, no? If that is the case you can play > whack-a-mole with that until you find a 'good' number. But, as I see it, > without a realtime ATM cost scheduler, even if I figure out my true > 'overhead' it won't make much difference. > > Thoughts, anyone? You can find it by experementation - if you get a cell count from your modem it's easy. If you are on BT in the UK using pppoa/vc mux it's 10 (you can't even look that up - the RFC says 9 or 10). ping -s 10 uses 1 cell -s 11 2. 10 data + 20 IP + 8 ICMP = 38, ATM cell data size = 48 so ppp overhead is 10. Like ED I haven't really looked at the code - but will eventually If it doesn't get done by anyone else first :-) Andy. _______________________________________________ LARTC mailing list / LARTC@mailman.ds9a.nl http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/