Re: improvements

[David Young <dyoung%pobox.com@localhost>]

On Sat, Sep 28, 2013 at 07:02:30PM -0400, Thor Lancelot Simon wrote:
> On Sun, Sep 29, 2013 at 08:32:01AM +1000, Darren Reed wrote:
> > 
> > Agreed, supporting VLANs with bridge(4) would be very useful.
> > 
> > From a certain perspectice, swconfig(8) is nothing more than the means
> > throughwhich the hardware is programmed.
> > 
> > How does brconfig need to change in order for swconfig to not be required?
> > 
> > Or are further changes required, such as the device model where we have
> > a"switch" that attaches to mvls0 and a "switch" that attaches to some
> > softwarebridge?(Both switches would be managed using the same commands.)
> 
> That sounds right to me.  brconfig (which would become a bit of a misnomer)
> should control an arbitrary L2 backend, which might be implemented by a
> driver for a hardware bridge (or switch) or might be implemented by a
> driver that itself implements a software bridge/switch.  This would entail
> splitting the current bridge(4) driver in half.

I find it useful to think of layer-2 forwarding domains (commonly
they're called VLANs, but VLAN also is taken to mean a kind of
encapsulation, so I call it a "forwarding domain" to be clear),
each domain with one or more ports belonging to it, and "tagged" or
"untagged" being a property of the port's domain membership.

I've described something like this before,
<http://mail-index.netbsd.org/tech-net/2011/05/11/msg002614.html>.
Others have given this question a much more thoroughgoing treatment than
I have.

I think that the configuration as seen and modified by the operator
should reflect the logical network topology, not the hardware topology.
So, while I think the kernel should try its best to optimize for the
cases where two forwarding domain member ports attach directly to the
same switch matrix, I don't think that you need to burden the operator
with the switching topology.  I figure an operator who is interested in
such details can derive them from their dmesg, besides.

Dave

-- 
David Young
dyoung%pobox.com@localhost    Urbana, IL    (217) 721-9981