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<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial
size=2>Simple: It is a major design goal for STP to avoid temporary loops. It
not one for routing protocols and TRILL. This is partly because L3 and TRILL
have a loop mitigation mechanism in the data plane that does not
currently exist at L2 and a different forwarding scheme. I hope you can agree on
that. I'll let you word this adequately as I'm again not a native English
speaker. </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial size=2>I
have the same kind of emotional reaction as yours when I see some of those
routing vs. bridging presentations that emphasize how normal it is for bridged
networks running STP to experience transient loops. And for now, your draft is
explicitly written to stress that, by quoting the bogus result from this
research paper and putting side by side the fact that transient loops are
possible with STP and the expectation for TRILL in this regard. This is wrong.
</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial size=2>I
don't think it is diminishing the merit of L3 protocols or TRILL to quote that
they don't have the same requirement as STP. I'm including below the link to two
recent papers from Mick Seaman, who has been attempting to put the same level of
loop prevention as STP in a link state based control protocol for L2. That will
give a perspective of what is missing in TRILL to reach the same level as STP in
this regard. Of course, if anyone has a simpler way of doing this, please let us
know. I'm not saying this ironically, it would be
really great.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial
size=2><A
href="http://www.ieee802.org/1/files/public/docs2008/aq-seaman-link-state-bridging-0508.pdf">http://www.ieee802.org/1/files/public/docs2008/aq-seaman-link-state-bridging-0508.pdf</A></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial
size=2><A
href="http://www.ieee802.org/1/files/public/docs2008/aq-seaman-link-state-bridging-part2-0708.pdf">http://www.ieee802.org/1/files/public/docs2008/aq-seaman-link-state-bridging-part2-0708.pdf</A></FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial
size=2></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=120360620-21082008><FONT face=Arial
size=2>Francois</FONT></SPAN></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT size=2></FONT> </DIV><BR>
<BLOCKQUOTE dir=ltr
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left>
<HR tabIndex=-1>
<FONT face=Tahoma size=2><B>From:</B> Donald Eastlake
[mailto:d3e3e3@gmail.com] <BR><B>Sent:</B> Thursday, August 21, 2008 12:16
PM<BR><B>To:</B> Francois Tallet (ftallet)<BR><B>Cc:</B>
rbridge@postel.org<BR><B>Subject:</B> Re: [rbridge] WGLC comments on problem
and applicability statement<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=ltr>
<DIV>
<DIV>
<DIV>See below:</DIV>
<DIV><BR>
<DIV class=gmail_quote>On Thu, Aug 21, 2008 at 2:03 PM, Francois Tallet
(ftallet) <SPAN dir=ltr><<A
href="mailto:ftallet@cisco.com">ftallet@cisco.com</A>></SPAN> wrote:<BR>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV>
<DIV dir=ltr align=left><SPAN><FONT face=Arial size=2>Just a comment on
section 3.3's summary:</FONT></SPAN></DIV>
<DIV>
<DIV class=Ih2E3d>
<P style="MARGIN: 0px; FONT: 13px Arial"><EM><STRONG>Section
3.3:</STRONG></EM></P>
<P style="MARGIN: 0px; FONT: 13px Arial"><EM><STRONG>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.</STRONG></EM></P></DIV>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR><SPAN><FONT
size=2>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;-)</FONT></SPAN></P></DIV></DIV></BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>[dee3] Of course I can't actually tell what is in some else's mind or
what their motivations are but I've heard many statement that would give many
people the false impression that there can never be temporary loops with any
version of spanning tree. I've seem presentations comparing spanning tree with
"routing" that give the false impressions that no version of spanning tree can
ever have a transient loop but that "routing protocols" routinely have
persistent loops.</DIV>
<DIV> </DIV>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV>
<DIV>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><SPAN><FONT
size=2></FONT></SPAN></P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><SPAN><FONT
size=2>The real comment is that the draft is using what can be considered
<STRONG>exceptional </STRONG>STP failure scenarios to justify
TRILL's <STRONG>normal</STRONG> way of
operation.</FONT></SPAN></P></DIV></DIV></BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>[dee3] This document is not the protocol specification. It is the problem
statement and applicability document. It sets only very broad bounds on how
whatever TRILL protocol is adopted would work. If you want to claim that it
would <SPAN class=Apple-style-span style="FONT-WEIGHT: bold">allow</SPAN> such
a "way of operation", fine. But I don't see it as specifying or justifying any
particular "normal way of operation".<BR></DIV>
<DIV><BR></DIV>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV>
<DIV>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><SPAN><FONT
size=2>I'll be happy if your next draft simply acknowledges that TRILL does
not attempt to prevent temporary loops the way STP
does.</FONT></SPAN></P></DIV></DIV></BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>[dee3] It seems unlikely that the TRILL protocol will do much of anything
the same way STP does and I think that is pretty clear from the document. As
is always the case when you are requesting a change in a draft, it would be
good to provide a specific wording change suggestion.</DIV>
<DIV> <SPAN class=Apple-style-span
style="FONT-FAMILY: Arial"> </SPAN></DIV>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV>
<DIV>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><SPAN><FONT
size=2>Regards,</FONT></SPAN></P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><SPAN><FONT
size=2>Francois</FONT></SPAN></P></DIV></DIV></BLOCKQUOTE>
<DIV><BR></DIV>
<DIV>Donald</DIV>
<DIV> </DIV>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<DIV>
<DIV>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><SPAN><FONT
size=2></FONT></SPAN></P></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV lang=en-us dir=ltr align=left>
<HR>
<FONT face=Tahoma size=2><B>From:</B> <A
href="mailto:rbridge-bounces@postel.org"
target=_blank>rbridge-bounces@postel.org</A> [mailto:<A
href="mailto:rbridge-bounces@postel.org"
target=_blank>rbridge-bounces@postel.org</A>] <B>On Behalf Of </B>Donald
Eastlake<BR><B>Sent:</B> Wednesday, August 20, 2008 8:43 PM<BR><B>To:</B>
<A href="mailto:rbridge@postel.org"
target=_blank>rbridge@postel.org</A><BR><B>Subject:</B> [rbridge] WGLC
comments on problem and applicability statement<BR></FONT><BR></DIV>
<DIV>
<DIV></DIV>
<DIV class=Wj3C7c>
<DIV></DIV>
<DIV dir=ltr>
<DIV>
<P style="MARGIN: 0px; FONT: 13px Arial">Hi,</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Below is my summary of the
Working Group Last Call comments on draft-ietf-trill-prob-04.txt.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">General:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">There appears to be a rough
consensus that the draft is excessively critical of spanning tree and this
should be corrected in several places.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Abstract:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">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 body.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Introduction:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">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.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Section 2:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">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.</P></DIV>
<BLOCKQUOTE
style="BORDER-RIGHT: medium none; PADDING-RIGHT: 0px; BORDER-TOP: medium none; PADDING-LEFT: 0px; PADDING-BOTTOM: 0px; MARGIN: 0px 0px 0px 40px; BORDER-LEFT: medium none; PADDING-TOP: 0px; BORDER-BOTTOM: medium none"><SPAN
style="FONT-FAMILY: Arial">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.</SPAN><BR></BLOCKQUOTE>
<DIV>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Section 2.1:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">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.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Section 2.2:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">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.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Section 2.3:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">The referenced paper (reference
[5] 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."</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Section 2.5:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">That there are actually 65 trees
available with MSTP and that each is used for forwarding a non-overlapping
set of VLANs should be clarified.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Section 3.3:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">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.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Section 3.4:</P>
<P style="MARGIN: 0px; FONT: 13px Arial">One missing reference.</P>
<P style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 13px Arial"><BR></P>
<P style="MARGIN: 0px; FONT: 13px Arial">Thanks,</P>
<P style="MARGIN: 0px; FONT: 13px Arial">Donald (co-chair)</P>
<P style="MARGIN: 0px; FONT: 13px Arial">=============================</P>
<P style="MARGIN: 0px; FONT: 13px Arial">Donald E. Eastlake 3rd
+1-508-634-2066 (home)</P>
<P style="MARGIN: 0px; FONT: 13px Arial">155 Beaver Street</P>
<P style="MARGIN: 0px; FONT: 13px Arial">Milford, MA 01757 USA</P>
<P style="MARGIN: 0px; FONT: 13px Arial; COLOR: #0018ea"><SPAN
style="TEXT-DECORATION: underline"><A href="mailto:d3e3e3@gmail.com"
target=_blank>d3e3e3@gmail.com</A></SPAN></P>
<P
style="MARGIN: 0px; FONT: 13px Arial; COLOR: #0018ea"><BR></P></DIV></DIV></DIV></DIV></BLOCKQUOTE></DIV></BLOCKQUOTE></DIV>=============================<BR>Donald
E. Eastlake 3rd +1-508-634-2066 (home)<BR>155 Beaver Street<BR>Milford, MA
01757 USA<BR><A
href="mailto:d3e3e3@gmail.com">d3e3e3@gmail.com</A><BR></DIV></DIV></DIV></DIV></BLOCKQUOTE></BODY></HTML>