From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Sun Sep 10 2006 - 08:49:44 ART
Late, but I think I'm missing something.
I have 2 issues with Brian's words:
> Also the LLQ is always in effect, it
> does not wait for congestion to occur. Read this document for more
> info: ...
AFAIK, LLQ only kicks in when having interface congestion, AKA tx-ring full.
That is because LLQ is part of the software based congestion scheme,
and the only case where soft based congestion is activated w/o hardware
congestion (tx-ring full) is when explicit policers are configured.
So, if there is no HW congestion, there is no LLQ (in soft), and no
policer for priority traffic. This is actually ok, because packets
actually get low latency anyways...
>> is guaranteed low latency. If there is no congestion you can exceed
> the
>> rate and you won't get policed, but traffic over 100Kbps will not get
>> low latency. If there *is* congestion traffic over 100Kbps for that
>> class will get policed.
The first part is kind of missleading. If there is no congestion, all
the traffic will get the same treatment. There are no counters engaged
for changing anything below/over 100kbps.
-Carlos
Brian McGahan @ 16/08/2006 20:19 -0300 dixit:
> No, the LLQ does have a built in policer, so traffic above the
> maximum guarantee can get dropped. Also the LLQ is always in effect, it
> does not wait for congestion to occur. Read this document for more
> info:
>
> http://www.cisco.com/warp/public/105/priorityvsbw.html#configuringthepri
> oritycommand
>
>
> HTH,
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
> 24/7 Support: http://forum.internetworkexpert.com
> Live Chat: http://www.internetworkexpert.com/chat/
>
>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
>> Paul Dardinski
>> Sent: Wednesday, August 16, 2006 5:59 PM
>> To: Victor Cappuccio; Cisco certification
>> Subject: RE: LLQ and policing
>>
>> Victor,
>>
>> Don't think the traffic ever gets policed "per-se". It just will
>> continue to be sent but won't be prioritized, so will be intermingled
>> with other traffic vs. always sent first.
>>
>> PD
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
>> Victor Cappuccio
>> Sent: Wednesday, August 16, 2006 6:14 PM
>> To: 'Brian McGahan'; 'Bob Sinclair'; 'roehsler';
> ccielab@groupstudy.com
>> Subject: RE: LLQ and policing
>>
>> Ohhhh, my bad... I think I'm starting to discard packets now.
>> LLQ kicks in when there is congestion, and if there is congestion,
> then
>> LLQ
>> would be activated... and if traffic is above the configured LLQ BW
> then
>> it
>> would be policed.... Sorry, I do not know what happened; my English
>> seems to
>> be failing sometime, I was not reading the _NO_Congestio... (Maybe
>> stressed
>> because my lab date is near)...
>>
>> Please sorry again for the SPAM and thanks to both.
>> Gracias
>> Victor.-
>>
>>
>>
>> -----Mensaje original-----
>> De: Victor Cappuccio [mailto:cvictor@protokolgroup.com]
>> Enviado el: Miircoles, 16 de Agosto de 2006 05:59 p.m.
>> Para: 'Brian McGahan'; 'Bob Sinclair'; 'roehsler';
>> 'ccielab@groupstudy.com'
>> Asunto: RE: LLQ and policing
>>
>> Brian, an example would be great. Now I'm back from the begging AKA
>> CONFUSED
>>
>> Thanks
>> Victor.-
>>
>>
>> -----Mensaje original-----
>> De: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
>> Enviado el: Miircoles, 16 de Agosto de 2006 05:52 p.m.
>> Para: Victor Cappuccio; Bob Sinclair; roehsler; ccielab@groupstudy.com
>> Asunto: RE: LLQ and policing
>>
>> It's not contradictory. Suppose you configure "priority 100"
>> for a class. This means that all traffic up to 100Kbps for that class
>> is guaranteed low latency. If there is no congestion you can exceed
> the
>> rate and you won't get policed, but traffic over 100Kbps will not get
>> low latency. If there *is* congestion traffic over 100Kbps for that
>> class will get policed.
>>
>> HTH,
>>
>> Brian McGahan, CCIE #8593
>> bmcgahan@internetworkexpert.com
>>
>> Internetwork Expert, Inc.
>> http://www.InternetworkExpert.com
>> Toll Free: 877-224-8987 x 705
>> Outside US: 775-826-4344 x 705
>> 24/7 Support: http://forum.internetworkexpert.com
>> Live Chat: http://www.internetworkexpert.com/chat/
>>
>>
>>> -----Original Message-----
>>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>> Of
>>> Victor Cappuccio
>>> Sent: Wednesday, August 16, 2006 4:34 PM
>>> To: 'Bob Sinclair'; 'roehsler'; ccielab@groupstudy.com
>>> Subject: RE: LLQ and policing
>>>
>>> Hi Bob,
>>>
>>> Please if you do not mind, can you show us an example of doing that,
>> this
>>> seems to be contradictory of what Brian just sent
>>> "it can use more than the specified bandwidth, however traffic in
>> excess
>>> of
>>> the rate is not guaranteed low latency. If there is congestion and
>>> traffic
>>> exceeds the rate it will be policed."
>>>
>>> Thanks
>>> Victor.-
>>>
>>>
>>>
>>> -----Mensaje original-----
>>> De: nobody@groupstudy.com [mailto:nobody@groupstudy.com] En nombre
> de
>> Bob
>>> Sinclair
>>> Enviado el: Miircoles, 16 de Agosto de 2006 04:58 p.m.
>>> Para: 'roehsler'; ccielab@groupstudy.com
>>> Asunto: RE: LLQ and policing
>>>
>>> David
>>>
>>> LLQ does not police if there is no congestion. This has been a
> point
>> of
>>> confusion over the years, and is "unclear" in lots of documentation.
>> You
>>> can easily verify this by configuring a policy that prioritizes ICMP
>> with
>>> a
>>> very low bandwidth. Then do an extended ping with large packet size
>> and
>>> zero timeout.
>>>
>>> If you do want to police it when not congested, add a police command
>> to
>>> the
>>> class.
>>>
>>> HTH,
>>>
>>> Bob Sinclair CCIE 10427, CCSI 30427
>>> www.netmasterclass.net
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>> Of
>>> roehsler
>>> Sent: Wednesday, August 16, 2006 4:43 PM
>>> To: ccielab@groupstudy.com
>>> Subject: LLQ and policing
>>>
>>> Hi,
>>>
>>> Just trying to nail down an understanding of LLQ.
>>>
>>> When you specify the amount of bandwidth that LLQ traffic can have
>>> prioritized, can that class of traffic utilize more available
>>> bandwidth if there is not congestion on the link? In other words is
>>> the prioritized traffic policed to that specified limit?
>>>
>>> Thanks
>>>
>>> David
>>>
>>>
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> _______________________________________________________________________
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-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
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