MAE West

Mon Jul 14 06:38:50 UTC 1997

> 	Are you telling me that the GigaSwitch, unlike every other bridge
> since well before I became involved in networking, is incapable of spanning
> tree?  I find that hard to believe.  Could anyone on the list from DEC
> please confirm or deny this absurdity?

The GIGAswitch/FDDI does spanning tree. 

As Lance Tatman pointed out, load-balancing only works between
circuits joining the same two switches. This would certainly be a
factor in planning what kind of wide-area connectivity to use to join
two groups of switches. A single 400Mb/s aggregate might perform much
better than a pair of 200Mb/s aggregates.

Spanning tree plus wide-area connectivity implies that either you send
bits farther than they have to go (like from one switch at 55
S. Market to another via Ames), or you have wide area connectivity
sitting idle until a spanning tree recalculation decides to use it.

I'll check my firmware release notes to see if there are any issues or
restrictions regarding load-balancing and spanning tree in the last
couple revisions. 

Stephen
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Stephen Stuart				stuart at pa.dec.com
Network Systems Laboratory
Digital Equipment Corporation