Subject: [trill] Comments on draft-ietf-trill-cmt-00

From: Donald Eastlake <[email-masked]>
Date: Sat, 13 Oct 2012 11:15:53 -0400

There are my personal comments on draft-ietf-trill-cmt-00. I suggest
that after these and the few other comments have been handled, the -01
version be WG Last Called.

- Some acronyms need to be spelled out on first use.

- I think Figure 1 and Figure 2 are a bit muddled and should be
clarified to show separate connections from each RBk to each CEn. It
is also not clear to me why "DRB" occurs in the figures and I think it
should be dropped.

- The draft should be clear that when doing the RPFC for a
multi-destination TRILL Data packet ingressed with a virtual RBridge
nickname, the RPFC must assume that the TRILL Data packet might use
any of the trees that any of the RBk might use.

- The could be problems if a virtual RBridge nickname was taken away
by a real RBridge somewhere else in the campus that is higher priority
to hold a nickname. Perhaps the draft should suggest that virtual
RBridge nicknames are usually configured  and should be held with
maximum priority with with configured or unconfigured priority ranges,
as appropriate...

- I think it should be possible to use the Affinity Sub-TLV to change
the structure of multi-destination distribution trees in places other
than at the edge. So they should be valid as long as they do not
conflict even if the requested child is a real RBridge. But, of
course, the requested child has to be an adjacent RBridge and the
draft should say what it would mean if some RBridge lists, as a
requested child for some tree, its parent in that tree.

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA
 [email-masked]

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From: gayle noble <[email-masked]>
Date: Sat, 13 Oct 2012 21:55:54 -0700

>Thanks,Donald
These are the acronyms I noticed. Maybe they could listed be at the 
start of the document ??
Appointed Forwarder (AF)
Customer Edge (CE)
Coordinated Multicast Trees (CMT)
Intermediate System-to-Intermediate System (IS-IS)
(logical) Link Aggregation Group (LAG)
Link State Packet (LSP)
Media Access Control (MAC)
Routing Bridge (Rbridge)
Reverse Path Forwarding (RPF)
Shortest Path First (SPF)
Type Length Value (TLV)
Transparent Interconnect of Lots Of Links (TRILL)
Virtual Local-Area Network (VLAN)

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From: [email-masked]
Date: Mon, 15 Oct 2012 11:34:11 +0800

Hi Donald，

> any of the trees that any of the RBk might use.

Do you mean that RBn ignores the egress nickname in a received 
multi-destinaion TRILL data packet with a virtual RBridge nickname
when it does RPFC for that packet in that case? Or if I am wrong, 
please give a clearer explanation on that sentence by using an example.

Best Regards,
Zhai Hongjun
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
 Protocol Development Dept.VI, Central R&D Institute, ZTE Corporation
 No. 68, Zijinghua Road, Yuhuatai District, Nanjing, P.R.China, 210012
 
 Zhai Hongjun
 
 Tel: +86-25-52877345
 Email: [email-masked]
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

Donald Eastlake <[email-masked]> 
发件人:  [email-masked]
2012-10-13 23:15

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[trill] Comments on draft-ietf-trill-cmt-00

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA
 [email-masked]
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trill mailing list
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https://www.ietf.org/mailman/listinfo/trill

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From: Donald Eastlake <[email-masked]>
Date: Wed, 17 Oct 2012 23:41:15 -0400

Hi,

> please give a clearer explanation on that sentence by using an example.

One way to look at the RPFC is that at each RBridge port there is a
table of pairs of acceptable { ingress nickname, tree } where tree is
the egress nickname in a multi-destination TRILL Data packet. Say RB1
is not going to use all of the distribution trees being computed for a
campus. Then RB1 can optionally list the tress it is going to use.
This will reduce the amount of RPFC state at all the other RBridges in
the campus because instead of having an entry for some port for
ingress RB1 paired with every tree it only needs entries for ingress
RB1 paired with the trees RB1 says it might use.

Say a virtual RBridge RBv is in use as in the CMT draft. Then the edge
group RBridges, when converting a frame off the link to a TRILL Data
packet, will use RBv as the ingress nickname. Say you have 8 trees
being calculated for a campus and three edge group RBridges each using
two different trees. So the edge group RBridges all together only use
6 different trees. Then you need RPFC entries at every other RBridge
for ingress RBv and those 6 tree. You don't need entries for RBv and 8
tree, which wastes RPFC state. And if you only have entries for RBv
and less than 6 trees, some TRILL Data packets will be improperly
discarded due to the RPFC.

Thanks,
Donald

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From: [email-masked]
Date: Thu, 18 Oct 2012 20:00:29 +0800

Hi Donald,

Thanks for your explanation.

> Then you need RPFC entries at every other RBridge
> tree, which wastes RPFC state. 

I agree you on this point.

> And if you only have entries for RBv and less than 6 trees, some TRILL 
> Data packets will be improperly discarded due to the RPFC.

I think you are right. Now my question is whether or not there are 6 
acceptable RPFC entries for RBv at each RBridge port at a given other 
RBridge, each entry for RBv and each of those 6 trees. In my mind, 
no same acceptable RPFC entries for an ingress RBridge (neither a physical 

RBridge nor RBv) are permitted existing at different ports at one given 
RBridge.

Best Regards,
Zhai Hongjun
 
 Zhai Hongjun
 
 Tel: +86-25-52877345

2012-10-18 11:41

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Re: [trill] Comments on draft-ietf-trill-cmt-00

Hi,

Thanks,
Donald

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From: Donald Eastlake <[email-masked]>
Date: Thu, 18 Oct 2012 16:33:58 -0400

Hi Hongun,

> RBridge nor RBv) are permitted existing at different ports at one given

Right.

If you view the information at a port as just a table of the allowed
combinations of ingress nickname and tree at that port, then there are
six entries for RBv and the trees. But these six entries could be one
each at six different ports or all at one port or anything in between
depending on the topology and tree structures. Most likely, if you
have many ports on a TRILL switch, most of them would have no RPFC
entries for RBv ingress in this case.

Thanks,
Donald