Re: [bess] Robert Wilton's No Objection on draft-ietf-bess-evpn-oam-req-frmwk-08: (with COMMENT)

[Donald Eastlake <[e-mail]>]

Hi Rob,

On Thu, Apr 8, 2021 at 9:36 AM Robert Wilton via Datatracker
<[e-mail]> wrote:
>
> Robert Wilton has entered the following ballot position for
> draft-ietf-bess-evpn-oam-req-frmwk-08: No Objection
>
>...
>
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
> Hi,
>
> Thanks for this document.
>
> It's a bit unclear to me whether the descriptions/definitions of MIP/MEP/MA/MD
> are coming from CFM or RFC 6136.  Section 1.1 suggests that they are coming
> from CFM (but without a normative reference to 802.1Q), but the terminology
> implies that they are being taken from RFC 6136.

Although I have tweaked them a bit, the descriptions/definitions were
in the draft when I took up the pen along with the reference to RFC
6136. So I don't know where they came from. Surely the important thing
is their accuracy.

>  Certainly, there seem to be places in this document where more meaning of
>  these terms seems to be expected than what is provided in the terminology
>  section.   Section 2.6 refers to CCMs, but I think that a reader would only
>  understand what these are if they have read CFM.  Hence, I think that this
>  document would probably benefit from having a normative reference to 802.1Q
>  rather than informative.

I have no problem with adding more references to 802.1Q but would
moving 802.1Q from Informational to Normative require a new Last Call
since it is not an IETF Standards Track document?

> Minor comments:
>
>     2.1 OAM Layering
>
>     "and shows which devices have visibility into what OAM layer(s)."
>
> Perhaps indicate by the 'o' symbol. Otherwise the fact that the Link OAM is the
> end point of the physical links, whereas the other OAM endpoints are may cause
> confusion.

I'm not sure exactly what you are saying. The ends of the Link OAM
correspond to the ports. The other types of OAM generally run between
the central control planes of the nodes. Do you want me to add
something to the text about the 'o' symbols? ("and, as indicated by
where the "o"s line up, shows which devices have visibility into what
OAM layer(s).") Or what?

> Figure 2:

While I tried to give some hints in the details of this Figure, in
some of your comments below I think you are trying to read way too
much into fine details of this very high level diagram.

>  - Would it be helpful to move the 'o' marks to the end of the PE devices, to
>  line up with the Link OAM end points?
>
>  - Is "Service CFM" the right term here?  Does this mean "Service OAM - CFM"?

Probably should be "CFM (Service OAM)" and the PE "o" marks for it
should be moved to line up with the CE facing edge of the PE since
those ports are what are involved. Network OAM, such as BFD, logically
runs between central control planes of the PEs so having the "o"
centrally under the PE seems best to me.

>  - Probably helpful to add an informative reference to 802.3 Link OAM, which is
>  in figure 2.

OK, that can be made into a reference.

> 2.2 EVPN Service OAM
>
> - I'm not sure how clear "towards the device" is when the point is already
> within the device.

How about "towards the core of the device"? A port is one the edge of
a device so I think that saying it is "within the device" has a
slightly wrong connotation.

If you have two devices with 4 ports as follows:
  P1-Dev1-P2----------P3-Dev2-P4
CFM permits you to run tests between P1 and P2 or between P3 and P4
that test the continuity through and switching fabric of the devices
without using a link. Of course, you can also run tests from P1 to P3
or P2 to P3 or P1 to P4 or whatever. (Not all implementations of CFM
actually do all this. Some implement the MEPs/MIPs as virtual MEPs/MPs
in the ports that are actually implemented in the central control
plane of the device.)

> - The up and down arrows for the MEPS ("^" and "V") seem to potentially make
> Figure 3 more confusing.  Also "down" should be changed to "Down" in the last
> CE.

OK on the case change. So, on the ASCII art arrow heads, you think I
should just delete them?

> Nits:
>
> I'm not sure why the PE nodes are numbered by CE nodes are not.

Since these numbers are never used in the text, I'm inclined to eliminate them.

Thanks,
Donald
===============================
 Donald E. Eastlake 3rd   [phone] (cell)
 2386 Panoramic Circle, Apopka, FL 32703 USA
 [e-mail]

> Regards,
> Rob