On 2013-01-09, at 8:44 AM, Johnny Billquist <bqt at softjar.se> wrote:
A big part of the general problem is that all these numbers are local for each end of
connections, so that you can get very asymetrical setups.
Also, the metrics are set on the circuit, and not individual destinations. While this
worked more or less ok for DEC back in the day, with the bridge, the cost of two different
destinations over the same circuit could in reality be very different.
In the end, it boils down to a couple of things for tweaking the costs.
1. Preference of tunnel or bridge. If you prefer using the bridge, then just set the
ethernet circuit cost lower than the tunnel. The tunnel can be either a multinet tunnel,
or a tunnel on the cisco.
2. If the rest of your network isn't on the same ethernet as the bridge is, then you
can use tweaks and control to your hearts content.
3. If the rest of your network don't have some other path out, then it don't
matter if the ethernet circuit cost is high, so still feel free to tweak it as needed.
I think that you should be able to tweak the costs freely almost all the time, without any
issues. However, you will sometimes not get the results you are looking for if the other
end, and all intermediate nodes have also set their costs based on similar views as
yours.
Johnny
If this was a production network with large volumes of data travelling across it, careful
selection of metrics would be very important for performance. However, what we have is
an ad-hoc network with islands controlled by individuals. These individuals have
differing skill levels, hardware collections, and requirements from the network. There
is no 'backbone' provider or administrator, so the metrics end up being all over
the place.
In my case, if I had a link to a US area, who also had a link to a second US area, I would
want to take the path from the first to the second, instead of going through Sweden and
back (although I'm sure Sweden is beautiful this time of year). Assigning a fixed
cost to the path type doesn't take in to account the real latency of that path.
What would be ideal is if the mapping project that is currently underway could show the
metrics of the links (in both directions, because they could be assymetrical). If the
map could also show relative geographical locations, that would also be a good proxy for
latency estimates on links.
But you know what? This is the fun part of Hecnet. None of us are doing this because
it's a mission-critical network (for some of us, that's probably what our day jobs
are anyway) - we're doing it because it's fun, and we can play with
'what-if' without breaking anything important.
Sometimes the tone in here gets a little serious. I'd just like to say Thank You to
everyone on the network for giving us all this huge plaything that we all dreamed of
playing with a quarter of a century ago :)
Ian
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