Subject: Re: [6lo] WGLC of draft-ietf-6lo-lowpan-mib-01

From: Ulrich Herberg <[email-masked]>
Date: Tue, 6 May 2014 10:30:11 -0700

Hi,

I agree with Jürgen's argument that the current solution with the
interface table and a conformance group allows devices to not
implement per-interface statistics if they don't need/want to. This
saves the space for devices that are either too constrained or that
only have one interface. As Jürgen pointed out, in the first case they
could still sum things up. In some cases the sum may be sufficient,
but I could imagine that for debugging it may be helpful to know
counters for a specific interface.
If I am not mistaken, the current specification allows already what
Peter suggests, namely to use the sum instead of individual interface
counters, if so desired.

Best regards
Ulrich

On Wed, Apr 30, 2014 at 5:02 AM, Juergen Schoenwaelder
<[email-masked]> wrote:
> On Wed, Apr 30, 2014 at 01:34:24PM +0200, peter van der Stok wrote:
>> Hi Juergen,
>>
>> Thanks for introducing the sequences with interface separation.
>> To reduce storage space I want to propose a modification.
>> I see that objects are defined with name lowpanObject, and that a
>> SEQUENCE lowpanIfStatsTable with
>> sequence attributes lowpanIfObject is defined.
>>
>> I wonder whether the lowpanObjects cannot be suppressed because their
>> contents is the same as the value of all lowpanIfObjects summed over all
>> interfaces.
>>
>> Given that for small devices only one interface is present this
>> modification would save quite some space for those.
>> For larger devices the extra transport of the value of all interfaces
>> instead of the sum seems acceptable to me.
>
> But then you require that _all_ implementations support per interface
> statistics. The current setup allows per interface statistics but does
> not require them. Note that you can sum things up in the agent if you
> happen to have per interface statistics and hence additional storage
> is not required for the counters.
>
> /js
>
> --
> Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
> Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>
>
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---

From: Ulrich Herberg <[email-masked]>
Date: Thu, 8 May 2014 09:28:47 -0700

Hi Jürgen,

I have an additional question:

On Wed, Apr 30, 2014 at 5:02 AM, Juergen Schoenwaelder
<[email-masked]> wrote:
[...] Note that you can sum things up in the agent if you
> is not required for the counters.

Allowing this "sum" of interface counters (and explicitly mentioning
that this is possible) could be useful as addition to support of the
more verbose per-interface counters. In this case, do you think we
need some flag to indicate that the counter values are actually a sum
of multiple interface counters (or maybe an integer of the number of
interfaces the counters are summed up)? Otherwise, an NMS could not
differentiate whether a counter is from a single interface or the sum
of multiple. This could become relevant if, e.g., failure counters
trigger some kind of alarm when being higher than a certain threshold.
Using the sum of multiple would surpass that threshold much quicker
evidently.

Best regards
Ulrich

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Thu, 8 May 2014 19:38:10 +0200

Hi,

since these are different objects, I think the semantics of the
counters are always clear. The rest is an implementation detail
(whether you keep separate counters or not).

/js