[rbridge] WGLC comments on problem and applicability statement
Francois Tallet (ftallet)
ftallet at cisco.com
Thu Aug 21 11:03:21 PDT 2008
Just a comment on section 3.3's summary:
There was one comment that there are no transient loops in Spanning
Tree. This is incorrect. Transient loops, however unlikely, are possible
with Spanning Tree.
You actually made the comment that some people were claiming there could
not ever be a loop with STP (I will never make that claim as I would
have a hard time justifying what I'd been working on for 10 years;-)
The real comment is that the draft is using what can be considered
exceptional STP failure scenarios to justify TRILL's normal way of
operation. I'll be happy if your next draft simply acknowledges that
TRILL does not attempt to prevent temporary loops the way STP does.
From: rbridge-bounces at postel.org
[mailto:rbridge-bounces at postel.org] On Behalf Of Donald Eastlake
Sent: Wednesday, August 20, 2008 8:43 PM
To: rbridge at postel.org
Subject: [rbridge] WGLC comments on problem and applicability
Below is my summary of the Working Group Last Call comments on
There appears to be a rough consensus that the draft is
excessively critical of spanning tree and this should be corrected in
There were a number of complaints about the abstract; however
the abstract is reasonably consistent with the body. Rather than
considering such complaints twice, any problems with the body should be
fixed and then the abstract adjusted to be consistent with the revised
Comments in the draft concerning spanning tree slow convergence
need, at a minimum, to be qualified to indicate they generally do not
apply to RSTP.
There were complaints when 802.1Q was referenced, saying that
previous amendment that were incorporated such as 802.1s should be
referenced instead. And there were complaints when amendments such as
802.1s were referenced in other parts of the document saying that they
no longer exist and no amendments that have been rolled into the 802.1Q
base document should be mentioned separately.
In the normal case, when not otherwise qualified,
"802.1Q" should refer to the current IEEE 802.1Q standard at the time
this draft is published and as specified in the References section;
however, there is no particular harm in referring to earlier amendments
that have been rolled into 802.1Q as long as their status is mentioned.
There was one comment that thicknet, thinnet, and hubs should
not be mentioned because they no longer exist but the reference to them
is historical and there are still hubs, at least, in use.
There is a statement in the draft intended to compare ECMP
link-state with non-ECMP link state which may appear to be a comparison
between ECMP link-state with STP. This should be clarified.
The referenced paper (reference  in the draft) contains
serious errors and should probably not be referenced. But, as Francois
Tallet said, "RSTP can indeed suffer from the usual count to infinity
issue specific to distance vector protocols that can delay the
convergence by few seconds."
That there are actually 65 trees available with MSTP and that
each is used for forwarding a non-overlapping set of VLANs should be
There was one comment that there are no transient loops in
Spanning Tree. This is incorrect. Transient loops, however unlikely, are
possible with Spanning Tree.
One missing reference.
Donald E. Eastlake 3rd +1-508-634-2066 (home)
155 Beaver Street
Milford, MA 01757 USA
d3e3e3 at gmail.com
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