Subject: RE: [Diffserv] DiffServ MIB Counters + PIB counters

From: GARBISU Jean-Pierre FTRD/DMI/CAE <[email-masked]>
Date: Tue, 19 Dec 2000 18:58:26 +0100

sorry for this late answer to a previous mail 

thinking of one of the last comments of F.Baker on an accounting tool for
SLA I think it was one of the main idea behind my questions i.e. how much
the MIB will help to verify SLS, and also give infos to TE tools for CoS   

for this I guess we need more careful counting than for best effort traffic,
possibly at the main stages of forwarding plane identified in the model
on your previous answers :
OK :  on 1 and 2
3 : policed datagrams refer to droppped datagrams (by absolute droppers)so
no count is envisioned it seems.
4 : it's an agreement
5 : OK but I know people/projects who would like this info for e.g. Traffic
Engineering optimisation purposes. I heard that some linux boxes do have
this type of info (but I don't strongly affirm it and want to stay in
diffserv charter ;-) 
6 : it seems clear that there is a necessary trade-off between counters
richness and all performance issues, unnecessary counters etc. but at this
point I don't really see what is the recommended way for a service provider
to evaluate the efficiency of weights attribution to queues in various
schedulers i.e. the conf of the PHB if some counters don't give info on
average use of queues?
7: datagrams dropped due to maximum service rate in a queue are certainly
dropped by absolute droppers not by algorithmic droppers (they are out of
profile in their queue) (please think, secretly, of VoIP implementations
:-)) 
8 : OK
9 : OK 

best regards

[email-masked] 

-----Message d'origine-----
De : Kwok-Ho Chan [mailto:[email-masked]]
Envoyé : jeudi 16 novembre 2000 21:09
À : GARBISU Jean-Pierre FTRD/DMI/CAE
Cc : [email-masked]'
Objet : Re: [Diffserv] DiffServ MIB Counters + PIB counters

Jean-Pierre:
Please find response embedded.
Please let me know if this answers/resolved the issues you indicated.
Thanks!
-- Kwok --

At 02:38 PM 11/13/00 +0100, GARBISU Jean-Pierre FTRD/DMI/CAE wrote:
>Hi
>herafter you 'll find a few questions on Counters related to the diffserv
>MIB draft (+ one question on the PIB)
>sorry if some of these questions were already asked
>best regards.
>
>In §3.3.2 it's written
>"Count Actions are used to count the traffic passing along a particular
>path through the model. If specified, they are likely to be placed
>first, before other types of Action. For example, when both a Count and
>an Absolute Dropper Action are specified, the Count Action needs to
>count the traffic stream before any traffic gets dropped.  Note that
>there are counters contained directly in Algorithmic Dropper elements to
>indicate the amount of traffic dropped by those elements."
>
>Can you confirm/comment the following :
>
>1. there are no specific diffserv counters counting all datagrams received
>before classification stage. 
>1bis. this information is available through MIB II interface counters. Is
it
>totally unnecessary to "repeat this info" in the diffserv MIB for any kind
>of optimization purpose?

It was the view of the authors that the info are already available in other
counters and no need to be repeated within DiffServ counters.
But the Model does not limit an implementation to create a Counter-Only-TCB
and place this TCB as the first TCB to process DiffServ data flow, if a
specific
implementation requires such setup.
Do you see any cases this will not work?

>2. you recommend to count datagramms (per BA) after classification stage
(at
>this point DSCP is not attributed; it's going to be in the following action

>stage i.e. marking).

The Count Action in this case is immediately before the Mark Action, with
the same packets/bits flowing thru both, hence the order of the Actions is
not important in this case.
 
>3. why absolute droppers must/should not count policed datagrams? at this
>point it seems one must get meter configuration information to retrieve
this
>information, if needed.

Please reference Model-04 draft section 8 for the following discussion.
By "policed datagrams" I take you mean Metered, with some datagrams
conforming, and some non-conforming.
In Model (constructable in MIB) draft, Metering stage happens before the
Action stage, hence Metered/policed datagrams are counted.
The manager does need to know which Count Action entry represent the
conforming and non-conforming branches of the Meter.

>4. you recommend to count datagramms dropped (per BA) per algorithmic
>droppers.

Please clarify, is this a question, agreement, comments?
There are counters in algorithmic dropper.

>5. there is no recommended diffserv counters defined for average occupancy
>of the BA queues.

In previous WG discussions, it was decided that queue average occupancy
need not be accessible outside of a device.
 
>6.  there is no recommended diffserv counters defined for unused bandwidth
>re-attribution between queues. 
>6bis. shouldn't be valuable to count this re-attribution in any way to
allow
>any kind of subsequent weights optimization of the concerned schedulers?  

The MIB does not limit one to add implementation specific Action stages
to do some of the things you are talking about.
One may say the MIB is too flexible.  Do you value such flexibility?

>7. do you recommend any counters for datagramms dropped due to maximum
>service rate in a queue?

I think that is taken care of by Algorithmic Dropper's counters, please
let me know if you think otherwise.

>8. how far the diffserv MIB specification is supposed to indicate the
>optional or mandatory counting or no counting stages?

The MIB recommends at least one Count Action after each branch of
Meter.  Note this is a recommendation, not a requirement.  Any additional
counters are up to implementation needs and capability.

>
>9. one of the main functional "differences" between MIB and PIB
>specifications seems to be the absence of counters in the PIB spec (both
MIB
>and PIB covering the configuration of the TCB). Is it a current issue? Is
>there any plan for specifying appropriate counters in the PIB spec.

The DiffServ PIB is for provisioning only, not monitoring, hence no counters
are defined there.  Another PIB can be defined for counting purpose.  Such
a PIB "Accounting PIB" is being developed in the RAP WG, which is general
purpose Accounting info, not just DiffServ.

>
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>
>
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