[rbridge] WG LC draft-ietf-trill-prob-04.txt

[Francois Tallet (ftallet)]

Steve,
Actually, your email is exactly in the lines of what I think should be
corrected in the document.

| Concerning "the only current deployed protocol at Layer 2"
| 
| This is untrue, as many vendors have proprietary solutions 
| that don't involve spanning tree.  HP ProCurve has Meshing, 
| and I believe Extreme also uses some propriety stuff as well. 
|  Cisco has Their some variances of Spanning tree, and some 
| true alternatives with some of their stacking features (I'll 
| admit this is very limited, but it isn't spanning tree 
| either).  

I don't know exactly what alternate protocols you are referring to, but
I would not be surprised if they computed a spanning tree for the data
plane, unless they changed the way frames are bridged (which is not
simply a control plane change then). Even if the control protocol is not
the Spanning Tree Protocol, your data plane requires a spanning tree
because of the way frames are switched. That's what is preventing
multipathing.
That's this confusion that makes the following incorrect if you are
talking of the Spanning Tree Protocol:

|Spanning Tree is deficient in many 
| ways and forces people down paths that can be costly since a 
| tree topology causes lots of aggregation.  Many people could 
| forestall an upgrade to 10Gig with a Trill solution in a mesh 
| topology.

TRILL does much more than replacing the control protocol of current
bridges. And STP is not the reason why we don't have multipathing now in
802.1Q (actually, the first draft of 802.1aq, the 802.1 TRILL
equivalent, is based on MST).

Exaggerating the "deficiencies" of STP will just turn the bridging
community against the project. After seeing the document for the first I
read: "It's time we bring modern age routing technology to this bridging
world, that is still relying on deficient custom routing protocol". Then
insisting on the long convergence time of STP (btw, RSTP is out for
almost a decade and today 802.1D *is* RSTP) and mentioning that
transient loops are part of the normal protocol operation does not add
much credibility to the argument;-)

But most of all, I don't think it is necessary to bash STP to make the
move to TRILL or 802.1aq worthwhile for most users. There is a real
expectation for something new in the area. 

Regards,
Francois

| 
| Steve
| 
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