From: Darby Weaver (ccie.weaver@gmail.com)
Date: Mon Dec 01 2008 - 19:57:32 ARST
Now an interesting option is available after the priority command:
RTR(config-pmap-c)#pri 7000 ?
<32-2000000> Burst in bytes
<cr>
But I'll have to agree with Solie on this one and have to ask at what point
should one expect that a class of traffic that is effectively policed at
7168 allowed to burst to yet a higher rate.
I think you will find this example mentioned by Szigetti in End-to-End QoS.
On Mon, Dec 1, 2008 at 4:36 PM, Darby Weaver <ccie.weaver@gmail.com> wrote:
> Then the answer of the question would be that the priority command
> effectively carves out a chunk of bandwidth for the class in question.
> This means if you have 7Mbps to Voice and were using the priority command to
> police the traffic, then congested or not, this is the amount of traffic
> Voice would be limited to. No matter the bandwidth of the link or the state
> of link with regard to congestion.
>
>
>
>
> On Mon, Dec 1, 2008 at 3:40 PM, shank shank <shankshink@yahoo.com> wrote:
>
>> i guess what i was trying to understad that is when the priority command
>> is
>> applied to certain calss can we think of this as a way to limit the
>> bandwidth
>> to that class to whatever bandwidth configured. i thnk this what anthony
>> confirmed. or is it conditioned on the congestion status of the interface?
>> ________________________________
>> From: Scott M Vermillion
>> <scott_ccie_list@it-ag.com>
>> To: paul cosgrove <paul.cosgrove@gmail.com>
>> Cc:
>> Anthony Sequeira <asequeira@internetworkexpert.com>; shank shank
>> <shankshink@yahoo.com>; CCIE Group <ccielab@groupstudy.com>
>> Sent: Monday,
>> December 1, 2008 3:00:46 AM
>> Subject: RE: Priority command
>>
>>
>>
>> > The link
>> mentions that "During
>> congestion conditions, a priority class cannot use any
>> excess bandwidth".
>> Perhaps that is what you are thinking of.
>>
>>
>> That s
>> precisely what I was thinking of Paul!
>> ;-)
>>
>> Now
>> this whole thing gets
>> interesting when you really ponder the definition of congestion.
>> It s
>> tempting to think that 129 kbps of traffic presenting to an
>> interface clocked
>> at 128 kbps equals/leads to congestion (which it obviously
>> does) and leave it
>> at that. But congestion actually occurs
>> in scenarios where you haven t even
>> reached your interface clock
>> rate! As I understand things, anyway. For the
>> purposes of QoS,
>> congestion means that your TxRing is full and has backed up
>> into the configured
>> SW queue(s). Depending on TxRing s depth and the
>> burstiness of the
>> traffic, it may well fill quickly (and recall that the very
>> act of configuring
>> a SW queue on an interface automatically results in its
>> TxRing being truncated
>> so as to invoke the SW queue more readily).
>>
>> So
>> I
>> think if you had an interface running at 100 Mbps and you configured a
>> priority class of 10 Mbps, then presented nothing but the priority class
>> of
>> traffic to that interface, you d likely see greater than 10 Mbps of
>> throughput
>> but less than 100 Mbps, depending on the nature of the traffic itself
>> (and to
>> an extent I can see there being platform-specific and interface
>> type-specific
>> differences). I would expect the SW queue to be invoked at
>> some point, the
>> priority-class to be policed, and then the SW queue to be
>> released for a
>> period, so on and so on
>>
>> (may
>> just be a good lab to put together at some
>> point)
>>
>>
>> -----Original Message-----
>> From: nobody@groupstudy.com
>> [mailto:nobody@groupstudy.com] On Behalf Of
>> Anthony Sequeira
>> Sent: Sunday,
>> November 30, 2008 12:25 PM
>> To: shank shank
>> Cc: CCIE Group
>> Subject: Re:
>> Priority command
>>
>> Yes - the priority command is used with Low Latency Queuing
>> (LLQ) and
>> it specifies the amount of priority bandwidth to provide to a type
>> of
>> traffic (typically Voice). This command also causes a POLICING to the
>> amount of bandwidth specified..
>>
>> This is a mechanism to guard against queue
>> starvation for other
>> traffic forms.
>>
>> Anthony J. Sequeira, CCIE #15626, CCSI
>> #23251
>> Senior CCIE Instructor
>>
>> asequeira@internetworkexpert.com
>>
>> Internetwork
>> Expert, Inc.
>> http://www.InternetworkExpert.com <http://www.internetworkexpert.com/>
>> Toll Free: 877-224-8987
>> Outside
>> US: 775-826-4344
>>
>> On Nov 30, 2008, at 1:33 PM, shank shank wrote:
>>
>> > hello,
>> >
>> quick question experts: does the priority command apply a
>> > maximum limit when
>> specifying a bandwidth? or is it applying the
>> > minimum bandwidth certain
>> class can get in the policy?
>> >
>> > so does this command priority 100 means that
>> the maximum bandwidth
>> > the class will get is 100k?
>> >
>> >
>> > according to this
>> link
>> http://www.ciscosystems.com/application/pdf/paws/10100/priorityvsbw.pdf
>> >
>> it does both. can anyone clarify this to me. thanks,
>> >
>> >
>> > Blogs and organic
>> groups at http://www.ccie.net
>> >
>> >
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