[trill] TRILL OAM Requirements: Sections

[Thomas Narten <[e-mail]>]

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