[c-nsp] Maximum spannig tree instances

[Gert Doering]

Hi,

On Fri, Jul 17, 2009 at 09:05:57AM -0400, Ross Vandegrift wrote:
> > > I completely disagree - it's what comes out of solving problems
> > > related to the LAN - the LOCAL area network.  In virtualized LANs,
> > > there's typically only a few possible physical topologies that can
> > > exist.  MST seeks to exploit this to lower the amount of processing
> > > power that is required.
[..]
> I think you've misunderstood me - by "virtualized LAN" I meant VLAN,
> not VPLS.  It didn't take years for these designs to come up - the
> datacenter we run is a bog-standard, utterly uninteresting case of a few
> thousand servers, in a few thousands VLANs, with a pair of HSRP
> routers.

See my e-mail with the description of our topology.  VLAN usage doesn't
mean "trivial topology".

[..]
> I'll go a step further - I doubt that there's a substantially more
> optimal way to compute only the valid topologies.

Computers in the year 2009 shouldn't require humans to bow for them to
make life easy for the computer.

MST with automatic vlan->instance assignment, auto-creating a new instance
for every distinct VLAN topology encountered, would be a *good* protocol.
Save redundant computing effort, while providing maximum flexibility.

(Another nuisance of MST is that if you are forced to interoperate PVSTP
and MST boxes, there seems to be no way to tell the MST cloud "no, you are 
not the root of the STP", which brings great pain if all you want to do 
is "hook a management link from one of your switches into a customer setup 
that needs to run MST".  I can see that this makes sense if there is more
than one switch in the MST cloud, or topological diversity, but for
"there is a single port in this VLAN, only used for managment access to
the switch itself", this is just pain)

gert
-- 
USENET is *not* the non-clickable part of WWW!
                                                           //www.muc.de/~gert/
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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