* Malkus Lindroos <malkus at iki.fi> [2007-08-21 15:51:51]: > Matthew Toseland wrote: > > On Tuesday 21 August 2007 00:13, Matthew Toseland wrote: > >> On Monday 20 August 2007 21:59, Malkus Lindroos wrote: > >>> Of course it depends on what the ping time is supposed to reflect? At > >>> least for my nodes it seems to reflect the load of the network the node > >>> is connected to, not the load of the node or its internet connection. > >> It's a combination of the round trip time under ideal conditions (<0.2ms > >> on > > my > >> LAN), and the effect of the traffic on the links between the nodes > > (including > >> rate limiting). > > > > Sorry, not just network load, ping time is highly sensitive to CPU load on > > both ends too. This is why it's such a useful metric; we can't easily > > directly measure CPU load, and even if we create platform specific hacks, > > we'd be fooled by idle-time processes etc. > > OK - so there comes the problem. My node CPU load is only about 5-10%. > It has clearly idle time, and the maxpingtime is the primary limiter. > Some connected nodes have lower ping times than others - while many > nodes have ping times of 3000-4000 ms, some stay at 500. My node also > has plenty of free bandwidth and its hard disk is not overloaded. > > So in effect, the average ping is reflecting the CPU loads, bandwiths, > disk usage, etc. of my node + the nodes is connected to. This eliminates > load distribution among the nodes, as my node does not take more work > from the overloaded nodes because the overloaded nodes are limiting it. > When the load of the neighbouring nodes worsens, they also limit my > nodes ability to take load. I.e. the main problem in the ping times is > that it is determined not only by my node, but also the nodes that it is > connected to. In addition, the ping time is determined by a principle of > the weakest link - the ping time of a node becomes high if only one of > the nodes is overloaded. > > This also provides a possibility for a denial of service attack against > the 0.7 network - from the code it is not too difficult for someone > wishing to impede free speech (or the 0.7 against 0.5 networks) to > create bogus nodes that report way too high ping times. This would > severely hurt the 0.7 network from reaching its potential.
Using the median insteed of the mean solves that problem... Moreover really high ping times are not possible because there is a timeout. > > Because of this, there should at least be an option to disable the use > of maxpingtimes in the config for now and see if the network would > become faster. > Again, it's not a problem unless most of your peers are missbehaving... And as you choose them it's up to you. NextGen$ -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 189 bytes Desc: Digital signature URL: <https://emu.freenetproject.org/pipermail/tech/attachments/20070821/75f69741/attachment.pgp>