Re: [Cake] Per-host fairness

[Georgios Amanakis <g_amanakis@yahoo.com>]

Hi Sebastian,

> I probably would try to instantiate cake not on the wan but on
> a lan interface of the router and re-do the test without the “nat”
> option just to reduce the number of tested parts. If you should do
> this, please remember that ingress and egress are per interface, so
> downloads from the internet use the LAN-egress while internet-
uploads 
> use LAN-ingress, so make sure to switch the bandwidth definitions for
> your two cake instances accordingly. 
> 	Finally could you post the results of “tc -s qdisc” before,
> during and after your bit-torrent tests for the test you just
> reported and the LAN test in case you ago that route. 

I tried what you suggested on the LAN interface (ingress: 900kbit/s,
egress: 3300kbit/s). Details follow.

> > and when doing simple
> > things (i.e. downloading from a couple of websites) the bandwidth
> > is
> > divided fair per-host, i.e 1:1 between A and B.
> 
> 	Okay, does this stay fair if one of the hosts open a bunch of
> websites at the same time? Does the download test also give per-host
> fairness if the number of downloads is massively imbalanced between
> the hosts?

There seems to be a discrepancy here. If host A is downloading a file
(e.g. kernel.org) and host B opens a bunch of websites simultaneously
(e.g. "firefox arstechnica.com; firefox in.gr; firefox phoronix.com;
firefox cnn.com; firefox theguardian.co.uk") the following happens: for
the first 20 seconds host B gets 90% of the bandwidth and then it
slowly equilibrates to 50%-50%.


> > However, when one of
> > the hosts is using bittorrent, he also gets most of the bandwidth,
> > i.e.
> > if total ingress bandwidth is 3300kbit, A is using bittorrent and
> > gets
> > 2900kbit, B is downloading from a single website and gets 400kbit.
> 
> 	Bit-torrent is a hard problem it seems, especially the cobalts
> branch that you test is supposed to better deal with it though so
> this is abit of a puzzle. How long are your tests? Are you looking
> only at a few seconds or something like >30 seconds (maybe the shaper
> needs time to reach equilibrium)? What happens in the upload during
> theses tests? I also wonder how many new torrent connections are
> established during the test or are the torrent flows long lived?
> 
I am performing this test for 5 minutes, using the torrent for ubuntu-
16.10-desktop. Regarding new established torrent connections, these are
around 50 in this 5-minute interval. You *can* browse the web from host
B but there is notable latency. Pings to 8.8.8.8 are typically 300-
400msec.


Best regards,
George