[c-nsp] QoS - questions

[Murilo Antonio Pugliese]

Folks.

You already may know it, but I'm sending just in case 

Comparing the bandwidth and priority Commands of a QoS Service Policy
http://www.cisco.com/en/US/customer/tech/tk543/tk757/technologies_tech_note09186a0080103eae.shtml#

A doubt, if you want grant a class with LLQ without restricting its bandwidth,
how come you don't use PQ?

Priority Queueing
http://www.cisco.com/en/US/customer/docs/ios/12_1/qos/configuration/guide/qcdpq.html

Yours Truly.

Murilo Pugliese 
Data communication engineer / IP Network 
Diveo do Brasil Telecomunicações Ltda. 

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-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Jeff Tantsura
Sent: Tuesday, August 21, 2007 8:51 AM
To: 'Oliver Boehmer (oboehmer)'; 'Tim Franklin'
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] QoS - questions

Hi Oli,

Thanks for your answers!!!

Another question :)

Migrating QoS config from 12K (12.0S) to 7200 (12.4T) I've found that configuration of LLQ class with "priority" without bandwidth keyword is not allowed anymore.
Is this a trend we will see in later IOS releases?

Thanks,
Jeff

P.S. Common, you are not that old, it's the feature sets growing more and more :)


> -----Original Message-----
> From: Oliver Boehmer (oboehmer) [mailto:oboehmer at cisco.com]
> Sent: dinsdag 21 augustus 2007 13:27
> To: Tim Franklin; jeff.tantsura at sscplus.nl
> Cc: cisco-nsp at puck.nether.net
> Subject: RE: [c-nsp] QoS - questions
> 
> Tim Franklin <mailto:tim at pelican.org> wrote on Tuesday, August 21, 
> 2007
> 12:26 PM:
> 
> > On Tue, August 21, 2007 10:36 am, Jeff Tantsura wrote:
> >
> >> class LLQ
> >>  priority "bandwidth"
> >> policer would kick in only in case of congestion while in class LLQ  
> >> priority  police "bandwidth"
> >> policer would drop any traffic above the bandwidth specified.
> >
> > I'd go further than that - the behaviour I've seen to date, and 
> > would expect, is that in the first case even with congestion there 
> > is no policer.  Rather the LLQ gets a proportionate share of any 'free'
> > bandwidth above assigned minimum, just like any of the other CBWFQ 
> > queues.
> >
> > I've definitely pushed more than 'priority bandwidth' worth of 
> > priority traffic through a congested link before now.
> >
> >> Thanks in advance for clarification.
> >
> > Seconded, I'd like to know how this is *supposed* to work.
> 
> Thanks for your input, made me look at the MQC specs again (and will 
> have to revise my statement made earlier.. guess I'm getting old ;-)
> 
> the tocken bucket configured within the "priority" command is used to 
> tell if the router needs to guarantee low-latency for the packets. If 
> the traffic rate exceeds the configured rate, it will be sent right 
> away if the link is uncongested at the time of excess traffic arrival, 
> and will be dropped otherwise. I guess how this is exactly being 
> implemented is somewhat platform/queuing-infrastructure-dependant..
> Either way: You don't want to send more LLQ traffic than configured 
> there, otherwise you *might* drop packets.
> 
> priority without any cir/bw argument can result in all bandwidth being 
> used by this class, so a policer confirmed in addition (the 2nd 
> example
> above) would unconditionally drop packets above the configured 
> policer's rate.
> 
> 	oli

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