On Mon, Apr 6, 2015 at 3:03 PM, Juliusz Chroboczek <j...@pps.univ-paris-diderot.fr> wrote: >> Babel (dont know about OLSR) finds a "usable" path, then tunes to a >> better one, but each tuning step (particularly at high rates) can lose >> packets, which cause rate reductions. Ideally would like to never lose >> packets while tuning happens. > > I agree, but I would like to know how many packets we lose. Since the > remove/insert happen in quick succession, I'd expect it to be very few.
My own noted issue is that at high rates, on cheezy routers, we run out of cpu, while forwarding packets. One daemon, hostapd, wants to run at a pretty high rate, and falls behind its desired rate... and the context switch and what little work it does alone - costs 80Mbits of forwarding, currently, on the archer tplink c7 v2. (can send along a graph) You would hope that there would be no significant processing between syscalls in babel but it is hard to measure, and the easiest thing for me would merely to have been measuring the loss between atomic changes and not during the optimization phase. As it is I will try to setup some artificial benchmarks showing how much packet loss there really is when going from a wan connection to ethernet, as opposed to reordering. It might be interesting to show how windows behaves here as it as not yet got any decent mechanisms for handling reordering and slows down a lot. And I will keep touching the wet paint. A 4 phase commit seems feasible: add new route with metric 1025 del old route metric 1024 add same route metric 1024 del same route metric 1025 But dang it a single syscall should be doable, and if it isnt then the kernel APIs need to be fixed. And I do wish more of the routing folk out there tested their stuff at saturating workloads and differing RTTs such as what I do with netperf-wrapper rrul, rtt_fair, and rrul_be tests. I need to get on formalizing those tests for battlemesh. > -- Juliusz -- Dave Täht We CAN make better hardware, ourselves, beat bufferbloat, and take back control of the edge of the internet! If we work together, on making it: https://www.kickstarter.com/projects/onetswitch/onetswitch-open-source-hardware-for-networking _______________________________________________ Babel-users mailing list Babel-users@lists.alioth.debian.org http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/babel-users