Subject: [rbridge] Draft-gray-trill-rbridge-arch-01.txt

From: Donald.Eastlake at motorola.com (Eastlake III Donald-LDE008)
Date: Wed, 9 Aug 2006 23:56:21 -0400

Hi,

I think this should be a working group draft. Below are some thoughts;

Here are some comments on draft-gray-trill-rbridge-arch-01.txt from me
in my capacity as a working group member:

Abstract: I'm not familiar with the term "cross-section bandwidth".
Suggest "... to provide higher aggregate throughput and more robust
behavior under link interruption or rapidly varying topologoy than an
..."

Page 4, 3rd paragraph, next to last line, suggest replacing "all
available" with "optimized".

Page 6, 2nd paragraph, 1st & 2nd line: do we want to say "bridge
learning"? How about "attached MAC address learning" or something?

Page 7, 2nd bullet, 3rd line. Is "some or all" correct? What if it is an
frame addressed to a MAC address in the Bridging PDU range of addresses
(BPDU, PAUSE, ...)? What if it is a unicast frame received on the port
that the learning bridge thinks it needs to send it back out on, would
all bridges send it back out in such a "misconfigured" case? How about
just replacing "some or all" with "a subset"? Similarly, at the end of
this bullet, should it say "... being forwarded except certain bridge
control frames."?

Page 7, 3rd bullet, 2nd & 3rd line: suggest replacing "determines" with
"learns" and inserting "unicast" between "incoming" and "frame".

Page 8, 2nd bullet, 3rd line. Suggest replacing "layer 2" with "802.1D".

Page 9, last bullet, 1st line. Replace "the" with "an".

Page 10, 1st bullet, 2nd line. After "CRED" insert "(see section 2.2)".

Page 10, 2nd bullet. Actually, I think it would be nice if we could drop
all occurrences of "Switch" since it seems to randomly be used for
bridges and routers and who knows what. I think of it as more a
marketing than a technical term. At the end of this item, did you
actually mean "exclude"? Or "execute"? Or how about "exclude or
execute"? ;-)

Page 11, 1st bullet. I found this paragraph hard to parse. Perhaps
replace the text on the 4th, 5th and 6th lines with "...encapsulated
within the outer received L2 header. The outer L2 header in this case
..."

Page 13, section 3.1, 2nd paragraph, last line. Insert "active" between
"all" and "ports".

Page 14, section 3.2.2, 1st line. Does "special-case" really add
anything? How about dropping it?

Page 16, section 3.2.3, 1st paragraph: looks like the first "see
Section" refers to Section 3.1. Not so sure about the 2nd reference...

Page 17, last paragraph. Although it is pretty obvious, 'r' isn't
specified, so I suggest, in line 3, adding ", shown as 'r'" after
"...are replaced by Bridges". Also, I suggest inserting somewhere, such
as at the end of this paragraph, a sentence something like: "Note that
the former b8-b9 path, which is b8-r9 in Figure 2 and had been disable
by the hypothetical spanning tree in Figure 1, is now usable."

Page 19, section 4.2, 2nd paragraph: This can be read to imply that the
discovery protocol messages are flooded. How about changing the first
sentence to read "The discovery mechanisms must use protocol messages
which propagate information through ..."

Page 20, 3rd & 4th paragraphs, beginning "Rbridges must..." and "Note
that...": Both paragraphs include the phrase "same type" which I don't
understand in the context...

Page 20, 5th paragraph. Reference seems to be to "section 4.8".

Page 20, last paragraph, 4th & 5th lines: TTL's don't eliminate loops.
Suggest "...is limited by loop protection mechanisms...".

And here are some even less important quibbles:

Page 6, 1st paragraph, last line, suggest dropping "exclusively". Maybe
you can manually configure some if you want in some implementations...
(In general, absolute terms like "exclusively", "any", and "all" make me
nervous in a relatively high level architectural paper. There is
commonly some niggly exception in some rare or optional case...)

Page 6, section 2.1, first bullet. Actually, the official name of the
current 802 document (802-2001) is "IEEE Standard for Local and
Metropolitan Area Networks: Overview and Architecture". I suggest at
least inserting "architecture" so it reads "802: IEEE specification for
the Ethernet architecture ..."

Page 7, 1st bullet, add Informational reference for ARP [RFC 826].

Page 7, "Broadcast Domain" bullet. Suggest deleting the word "any".

Page 15, 3rd paragraph from the bottom starting "Each entry..." and
ending "... Egress Rbridge": I think this should somehow be broken into
two or more sentences.

Page 21, 1st bullet, and page 31 at top: do we want to say "protocol" or
"Ethertype"? I think Ethertype is better. Also, I'm not sure IANA would
be involved in getting an Ethertype from IEEE.

Page 22, last paragraph before section 4.5, 1st line. Suggest adding
something to the end of the 1st sentence, like "...not complete as new
information continues to be learned and old information may be timed out
and discarded."

Page 24, section 4.6.1, 3rd paragraph, 3rd line, suggest inserting
"entry" after "CFT".

I'll probably send some comments on sections 4.8 and 5 in a separate
message...

Thanks,
Donald