[Olsr-users] OLSRv2: default ethernet link speed

[Henning Rogge]

On Sun, Jun 19, 2016 at 6:06 PM, Lars Kruse <(spam-protected)> wrote:
> Hi,
>
> I am currently setting up OLSRv2 on a number of (openwrt-based) routers in my
> wireless community. After connecting 15 nodes I took a look at their estimated
> link speeds:
>
> (spam-protected):~# echo /olsrv2info edge | nc ::1 2009
> 2001:67c:1400:2432:15:6dff:fe80:931     2001:67c:1400:2432:24a4:3cff:fe86:3a59
> 1689    0       ff_dat_metric   120.47Mbit/s    17
> 2001:67c:1400:2432:15:6dff:fe80:97b     2001:67c:1400:2432:15:6dff:fe80:8f3
> 54329   0       ff_dat_metric   73.142Mbit/s    28
> 2001:67c:1400:2432:15:6dff:fe80:97b     2001:67c:1400:2432:27:22ff:fe44:c32f
> 54329   0       ff_dat_metric   1020bit/s       2105088
> 2001:67c:1400:2432:15:6dff:fe80:97b     2001:67c:1400:2432:24a4:3cff:fe86:3a59
> 54329   0       ff_dat_metric   97.523Mbit/s    21
> 2001:67c:1400:2432:15:6dff:fec5:c2b2    2001:67c:1400:2432:27:22ff:fe44:c1aa
> 26703   0       ff_dat_metric   1020bit/s       2105088
> 2001:67c:1400:2432:15:6dff:fec5:c2b2    2001:67c:1400:2432:5054:ff:fea0:3100
> 26703   0       ff_dat_metric   1020bit/s       2105088
> 2001:67c:1400:2432:15:6dff:fec5:c2b2    2001:67c:1400:2432:dc9f:dbff:fef4:34a9
> 26703   0       ff_dat_metric   1020bit/s       2105088
>
> As you can see in the (mangled) output above: some links are estimated with
> many MBit/s (these are the wifi links) and some other are estimated with 1020
> Bit/s (these are the ethernet links).
> Thus it seems like the default behavior regarding the estimation of the link
> speed of ethernet interface is not optimal.
> In order to work around this situation I added the "eth_listener" plugin to the
> list of statically compiled plugins. Afterwards the values for ethernet links
> reached reasonable values for my setup.

Yes, for some time I had the ethernet listener as a default plugin...
but people were concerned that it would detect 100 MBit/s links as
Gigabit and the other way around because of switching in between. But
I have yet to hear a better solution.

> Regarding this topic I went through a discussion of Bastian and Henning from
> May 2014 [1]. The conclusion of this thread seems to indicate that the
> "eth_listener" plugin is not conceived as a solution for the future but more as
> an intermediate hack. The "link_config" plugin was suggested as an alternative
> that allows static (configurable) bitrates for each interface [2].

I don't like manual configuration... maybe someone wants to build a
small plugin that can measure a link speed? ;)

> Now I am not sure how to proceed.
> Do these two plugins ("eth_listener" and "link_config") conflict with each
> other?
At the moment they would influence each other, but I will look for a
way to make the ethernet_listener to detect manual set values.

> Is the current estimation result (1020 Bit/s) for an interface without
> further configuration (e.g. via link_config) a reasonable default or is it
> supposed to force/remind the user to configure the bandwidth of the interfaces?
> Personally, I would prefer a setup that does not require configuration and
> works reasonably for the majority (but certainly not all) use cases.

1024 bit/s is just the minimal raw bitrate the metric can handle... I
use it as a very conservative default.

Henning