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From: Robert Watson <rwatson@freebsd.org>
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To: Lowell Gilbert <freebsd-current-local@be-well.no-ip.com>
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cc: Julian Elischer <julian@elischer.org>
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Subject: Re: RFC: ported NetBSD if_bridge
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On Sat, 17 Apr 2004, Robert Watson wrote:

> On 17 Apr 2004, Lowell Gilbert wrote:
> 
> > They're referring to IEEE 802.1d.  This is an important feature for
> > building large bridged networks. 
> 
> And it's an important part of many ethernet-layer redundancy solutions,
> since it allows fail-over when one bridging element or graph edge goes
> offline.  It's something we really missed in some research work I was
> working on to build link layer filters, since it was an easy way to
> provide basic fail-over in the presence of ethernet link failures (and
> they happen a lot!) 

Just as a followup for those not familiar with spanning tree in the
context of ethernet, here's a URL in one of Cisco's product manuals:

  http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/config/spantree.htm

It talks a bit about how the spanning tree algorithm applies to ethernet,
and applications of spanning tree.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert@fledge.watson.org      Senior Research Scientist, McAfee Research