Subject: [trill] TRILL OAM Requirements: Sections

From: Thomas Narten <[email-masked]>
Date: Thu, 26 Apr 2012 14:13:06 -0400

draft-tissa-trill-oam-req-00.txt says;

>    Section: A section is a partial segment of a path between any two
>    given RBridges. As an example, consider the case where RB1 is
>    connected to RBx via RB2 and RB3. The segment between RB3 to RBx is
>    referred to as a Section of the path RB1 to RBx.

Where does this notion of a section come from and why do we need it in
TRILL?  AFAIK, TRILL doesn't have this notion, so this is something
that OAM is creating on its own.

Then later:

>    An RBridge SHOULD have the ability to verify the above connectivity
>    tests on sections. As an example, assume RB1 is connected to RB5 via
>    RB2, RB3 and RB4. An operator SHOULD be able to verify the RB1 to
>    RB5 connectivity on the section from RB3 to RB5. The difference is
>    that the ingress and egress TRILL nicknames in this case are RB1 and
>    RB5 as opposed to RB3 and RB5, even though the message itself may
>    originate at RB3.

I am not comfortable with this requirement. This would seem to
complicate the requirements and I'm not sure why it is needed. I'm
also a bit wary about what the implication is in terms of what sort of
functionality or mechanism would be required to be able to achieve
this requirement.

(The notion of "sections" comes up in several places in the document,
and the above applies to all of them.)

Do we really want or need sections?

Thomas

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From: "Tissa Senevirathne (tsenevir)" <[email-masked]>
Date: Thu, 26 Apr 2012 15:33:44 -0700

"Section" is a general terminology used to identify a partial segment of
the path between two end points. Please refer to RFC 5860 "Requirements
for Operations, Administration, and Maintenance (OAM) in MPLS Transport
Networks". 5860 is listed as a reference in the document.
draft-tissa-trill-oam-req assumes readers are familiar with various OAM
concept in the industry. Relevant documents are also listed as
references.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Thomas Narten
Sent: Thursday, April 26, 2012 11:13 AM
To: [email-masked]
Subject: [trill] TRILL OAM Requirements: Sections

Where does this notion of a section come from and why do we need it in
TRILL?  AFAIK, TRILL doesn't have this notion, so this is something that
OAM is creating on its own.

I am not comfortable with this requirement. This would seem to
complicate the requirements and I'm not sure why it is needed. I'm also
a bit wary about what the implication is in terms of what sort of
functionality or mechanism would be required to be able to achieve this
requirement.

Thomas

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---

From: Thomas Narten <[email-masked]>
Date: Thu, 26 Apr 2012 20:07:36 -0400

Hi Tissa.

> concept in the industry. Relevant documents are also listed as

You didn't really respond to my core point though.

Why should TRILL OAM support this notion? What value does it have in a
TRILL network?

I cannot agree to say TRILL OAM needs to support this notion because I
don't understand the implications in terms of how it will impact the
OAM mechanisms and protocols that need to be defined.

Without understanding that (in a rough, architectural sense), I cannot
support it.

I also just don't see the value. Do operators define sections? How is
that useful in a TRILL network?

Thomas