Subject: RE: [Diffserv] Modeling of Policing component.

From: "ravikumarb" <[email-masked]>
Date: Mon, 1 Jul 2002 19:19:11 +0530

> 
> But acording to RFC 3290 in section 3.3, it says that policing can be modeled as a concatenation of an Algorithmic Dropper with a Scheduler. But I guess this should be the model for shaping rather than for policing.
> 
> Am I missing something here?

Please read the text more carefully:

   ...Policing is
   modeled as either a concatenation of a Meter with an Absolute Dropper
   or as a concatenation of an Algorithmic Dropper with a Scheduler.

and (in 7.1.3)

   An Algorithmic Dropper is an element which selectively discards
   packets that arrive at its input, based on a discarding algorithm.

I don't really see a problem here. The scheduler is not part of the policer,
so maybe it should have been mentioned in brackets, but in real life
it will always be there. This is an *informal* model.

We can have an Algorithmic Dropper as part of Policer, but not a Scheduler. The moment we have a Scheduler, what we are doing is Shaping not policing.

Regards,

- Ravi

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From: Brian E Carpenter <[email-masked]>
Date: Mon, 01 Jul 2002 17:41:33 +0200

> We can have an Algorithmic Dropper as part of Policer, but not a Scheduler. The moment we have a Scheduler, what we are doing is Shaping not policing.

As I said, this is an *informal* model.

   Brian

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From: "Andrew Smith" <[email-masked]>
Date: Mon, 1 Jul 2002 09:28:29 -0700

I disagree: if you follow an Algorithmic Dropper by a Scheduler (there's
an implied Queue in there somewhere), when the Queue starts to get full
due to "excess" traffic (arrival - departure > 0 over appropriate time
intervals), the Dropper will kick in. That is "policing" (it's doing
shaping at the same time of course). 

Meter->AbsoluteDropper is the more conventional way to think about
policing, I agree, but AlgorithmicDropper->Scheduler is also valid.

Andrew Smith

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of ravikumarb
Sent: Monday, July 01, 2002 6:49 AM
To: Brian E Carpenter
Cc: [email-masked]
Subject: RE: [Diffserv] Modeling of Policing component.
...
We can have an Algorithmic Dropper as part of Policer, but not a
Scheduler. The moment we have a Scheduler, what we are doing is Shaping
not policing.