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.

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
>>>
>>> _______________________________________________
>>> Isis-wg mailing list
>>> Isis-wg@ietf.org
>>> https://www.ietf.org/mailman/listinfo/isis-wg
>>>
>>
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