Re: [Isis-wg] I-D Action:draft-ietf-isis-layer2-05.txt

Donald -

> -----Original Message-----
> From: isis-wg-bounces@ietf.org [mailto:isis-wg-bounces@ietf.org] On
> Behalf Of Donald Eastlake
> Sent: Wednesday, May 05, 2010 6:29 AM
> To: Ralph Droms
> Cc: isis-wg@ietf.org
> Subject: Re: [Isis-wg] I-D Action:draft-ietf-isis-layer2-05.txt
> 
> Hi Ralph,
> 
> The existing table in draft-ietf-isis-layer2-05 in Section 5, split
> across pages 56 and 57, has an "LSP" column and an "MGROUP LSP"
column.
> By implication, those protocols indicated in the TRILL/IEEE/OTV column
> for an TLV/sub-TLV with an X in the MGROUP LSP column are specified in
> that draft as using the MGROUP set of PDUs. However, I, along with
many
> others, think the MGROUP cluster of three PDUs is unnecessary and
> should just be eliminated from the draft.
> 
> That leaves three other PDUs, the TRILL Hello, MTU-probe, and MTU-ack.
> 
> Not surprisingly, the "TRILL Hello" PDU is used by TRILL but it is a
> separate PDU only out of an abundance of caution. TRILL
implementations
> never use the "LAN Hello" used at Layer 3 and non-TRILL
implementations
> of IS-IS never issue a TRILL Hello. (Both use the same P2P Hello on
P2P
> links.) Since TRILL and Layer 3 frames are distinguished by using
> different multicast addresses and by using Area Addresses which are in
> practice, if not in theory, completely disjoint. Thus there are
already
> 2 means of separating "LAN Hellos" frames from "TRILL Hellos" and, as
I
> say, using a different PDU number for TRILL Hellos was suggested only
> out of an abundance of caution.

If such caution is needed for LAN IIHs, why is it not also needed for
P2P Hellos, LSPs, CSNPs, and PSNPs?

The answer that because there is new TLV information in TRILL Hellos
seems inadequate as there is clearly also new TLV information in LSPs
when used for L2.

I would also point out that in
http://tools.ietf.org/id/draft-ietf-isis-mi-02.txt wherein multiple
instances of Layer 3 would be operating on the same link, no new PDUs
are specified. 

The presence of different multicast destination addresses seems quite
robust. If it is known that both L2 and L3 are operating on the same
link different system IDs can be used for the two instances. This
provides additional protection in the case that a neighboring legacy L3
instance mistakenly processes L2 PDUs. Since the L2 instance will not
form an adjacency w the L3 instance, no two way connectivity will ever
be achieved.

I see no need for a new PDU for "TRILL Hellos".

   Les

> 
> The MTU-probe and MTU-ack provide a simple one-hop request-response
way
> to test link MTU. Implementation of MTU-probe is optional but a TRILL
> implementation receiving an MTU-prove must respond with an MTU-ack.
MTU
> is a loop safety consideration for TRILL. This MTU facility, and the
> ability to report MTUs with the extended IS reachability MTU sub-TLV,
> could also be used, for example, by Layer-3 IS-IS to collect
> information on which to base traffic engineered routes meeting some
> minimum MTU requirement.
> 
> Thanks,
> Donald
> 
> On Wed, May 5, 2010 at 8:36 AM, Ralph Droms <rdroms.ietf@gmail.com>
> wrote:
> 
> 
> 	John - I understand that OTV is a proprietary protocol.  My
> questino was asked to find out about applicability of those PDUs -
> which protocols require which PDUs, and what is the motivation for
> including each of those PDUs in draft-ietf-isis-layer2-05.txt.
> 
> 	- Ralph
> 
> 
> 	On May 5, 2010, at 8:21 AM 5/5/10, John E Drake wrote:
> 
> 
> 
> 		Ralph,
> 
> 		I think the point is that unlike TRILL, and IEEE
802.1aq,
> OTV is proprietary - nobody other than its designers has any idea how
> it works.
> 
> 		Publishing a few of its TLVs does absolutely nothing
> regarding interoperability.
> 
> 		Thanks,
> 
> 		John
> 
> 
> 
> 			-----Original Message-----
> 			From: isis-wg-bounces@ietf.org [mailto:isis-wg-
> bounces@ietf.org] On Behalf
> 			Of Ralph Droms
> 			Sent: Wednesday, May 05, 2010 5:07 AM
> 			To: isis-wg@ietf.org
> 			Subject: Re: [Isis-wg] I-D
Action:draft-ietf-isis-
> layer2-05.txt
> 
> 			Which of TRILL, IEEE 802.1ag and OTV use each of
the
> PDUs defined in
> 			draft-ietf-isis-layer2-05.txt?  Is it possible
to
> devise an
> 			applicability or usage table, similar to the
table
> for TLVs in section
> 			5, for the new PDUs?
> 
> 			- Ralph
> 
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