Re: LLQ

Hi Experts,

Quote from Petr's post Insights on CBWFQ on the following link:
http://blog.internetworkexpert.com/2008/08/17/insights-on-cbwfq/

If you have *priority* bandwidth configured in your policy map, subtract
this value from total interface bandwidth to yield the amount of bandwidth
available to other classes. The priority queue is only rate-limited under
interface congestion, and in such case, it cannot get more bandwidth than
configured with *priority* statement.

So from what I understand, the above text is saying that this rate-limiting
will only take place under interface congestion; thus if the interface is
not congested the priority queue is not really a policer, and might take
more than what is configured with the priority command.

Thank You Edison for the testing!

Best Regards,

On Tue, Dec 8, 2009 at 9:59 PM, Edison Ortiz <edisonmortiz_at_gmail.com> wrote:

> I don't have the original testing at the moment but I quickly pull up a
> scenario.
>
>
>
> R2 <----> R0 <----> R3
>
>
>
> R0 will LLQ traffic from R2 towards R3 - for this example, I lowered the
> priority to a minimum value to observe any drops with a simple ping (size
> 1500 bytes).
>
>
>
> R0 config:
>
> class-map match-all EF
>
> match ip dscp ef
>
> !
>
> !
>
> policy-map WAN_QOS
>
> class EF
>
> priority 9
>
> !
>
> R0#sh policy-map interface
>
> FastEthernet0/1
>
>
>
> Service-policy output: WAN_QOS
>
>
>
> Class-map: EF (match-all)
>
> 0 packets, 0 bytes
>
> 5 minute offered rate 0 bps, drop rate 0 bps
>
> Match: ip dscp ef (46)
>
> Queueing
>
> Strict Priority
>
> Output Queue: Conversation 264
>
> Bandwidth 9 (kbps) Burst 225 (Bytes)
>
> (pkts matched/bytes matched) 0/0
>
> (total drops/bytes drops) 0/0
>
>
>
> Class-map: class-default (match-any)
>
> 1 packets, 74 bytes
>
> 5 minute offered rate 0 bps, drop rate 0 bps
>
> Match: any
>
>
>
> Generate some traffic from R2
>
>
>
> R2#ping
>
> Protocol [ip]:
>
> Target IP address: 10.1.1.2
>
> Repeat count [5]: 10000
>
> Datagram size [100]: 1500
>
> Timeout in seconds [2]:
>
> Extended commands [n]: y
>
> Source address or interface:
>
> Type of service [0]: 0xB8
>
> Set DF bit in IP header? [no]:
>
> Validate reply data? [no]:
>
> Data pattern [0xABCD]:
>
> Loose, Strict, Record, Timestamp, Verbose[none]:
>
> Sweep range of sizes [n]:
>
> Type escape sequence to abort.
>
> Sending 10000, 1500-byte ICMP Echos to 10.1.1.2, timeout is 2 seconds:
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
>
>
> On R0:
>
>
>
> R0#sh policy-map interface
>
> FastEthernet0/1
>
>
>
> Service-policy output: WAN_QOS
>
>
>
> Class-map: EF (match-all)
>
> 697 packets, 1055258 bytes
>
> 5 minute offered rate 27000 bps, drop rate 1000 bps
>
> Match: ip dscp ef (46)
>
> Queueing
>
> Strict Priority
>
> Output Queue: Conversation 264
>
> Bandwidth 9 (kbps) Burst 225 (Bytes)
>
> (pkts matched/bytes matched) 2/3028
>
> (total drops/bytes drops) 2/3028
>
>
>
> You will notice some drop rate on the output and some drop was noticed on
> R2
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>
> !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!
>
>
>
> but the flow was not completely dropped like a policer.
>
>
>
> Let's test with a policer..
>
>
>
> On R0:
>
>
>
> class-map match-all EF
>
> match ip dscp ef
>
> !
>
> !
>
> policy-map WAN_QOS
>
> class EF
>
> police 9000
>
>
>
> On R2:
>
>
>
> ...
>
> ..........................
>
>
>
>
>
> Feel free to perform your own test as well.
>
>
>
> Edison Ortiz
>
> Routing and Switching, CCIE # 17943
>
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Tony
> Varriale
> Sent: Tuesday, December 08, 2009 2:23 PM
> To: 'Cisco certification'
> Subject: RE: LLQ
>
>
>
> I'm aware of what the docs say. I thought this was discussed here and
> found
>
> that anything over the priority statement was dropped. I could be
>
> remembering incorrectly.
>
>
>
> Do you have any of your testing that you care to share publically?
>
>
>
> Tony Varriale
>
> Flamboyan, Inc.
>
> C: 630.546.7610
>
> F: 815.717.9436
>
> tvarriale_at_flamboyaninc.com
>
>
>
>
>
> -----Original Message-----
>
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>
> Edison Ortiz
>
> Sent: Tuesday, December 08, 2009 12:32 PM
>
> Cc: 'Cisco certification'
>
> Subject: RE: LLQ
>
>
>
> The documentation and my testing say otherwise:
>
>
>
>
>
>
>
> "When the device is not congested, the priority class traffic is allowed to
>
> exceed its allocated bandwidth. When the device is congested, the priority
>
> class traffic above the allocated bandwidth is discarded."
>
>
>
>
>
>
>
>
> http://www.cisco.com/en/US/docs/ios/qos/command/reference/qos_n1.html#wp1048
>
> 842
>
>
>
>
>
>
>
>
>
>
>
> Edison Ortiz
>
>
>
> Routing and Switching, CCIE # 17943
>
>
>
>
>
>
>
> -----Original Message-----
>
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>
> Ahmed Elhoussiny
>
> Sent: Tuesday, December 08, 2009 1:19 PM
>
> To: Tony Varriale
>
> Cc: Cisco certification
>
> Subject: Re: LLQ
>
>
>
>
>
>
>
> Dear all,
>
>
>
> if LLQ is used for VOIP, it will get dropped/policed in case
>
>
>
> the traffic exceeds the LLQ size.
>
>
>
> And this in case there is congestion and same if there is no congestion.`
>
>
>
> LLQ got nothin to do with congestion, this is based on IOS & IOS XR
>
>
>
> features & also my testing while designing QOS for my Mobile operator.
>
>
>
>
>
>
>
> In some references you may find LLQ congestion aware....but this didn't
>
>
>
> successfully being implemented till now...
>
>
>
>
>
>
>
> WHY ?
>
>
>
> simply imagine u have an LLQ class with 1 M , and no interface BW
>
>
>
> congestion.
>
>
>
> VOIP traffic increased to reach 2 M, and no drops cuz of no congestion due
>
>
>
> to not used BW on other classes...
>
>
>
> SO what if the traffic in other queues increased, and reached its 100 %,
> now
>
>
>
> the LLQ will decrease to reach 1 M, and all VOIP calls will get some
> packets
>
>
>
> dropped which will affect most of VOIP calls...
>
>
>
>
>
>
>
> Hope this might help
>
>
>
>
>
>
>
> Thanks & B.regards
>
>
>
> Ahmed Elhoussiny,2x CCIE# 21988 (R&S-SP)
>
>
>
> Network Consultant & Cisco Academy Instructor
>
>
>
>
>
>
>
> On Tue, Dec 8, 2009 at 6:54 PM, Tony Varriale
>
> <tvarriale_at_flamboyaninc.com>wrote:
>
>
>
>
>
>
>
> > I thought the priority queue won't use the general bucket when it's over
>
>
>
> > its
>
>
>
> > defined number? Hence, all packets will get dropped.
>
>
>
> >
>
>
>
> > tv
>
>
>
> >
>
>
>
> >
>
>
>
> > -----Original Message-----
>
>
>
> > From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>
>
>
> > Narbik Kocharians
>
>
>
> > Sent: Tuesday, December 08, 2009 10:20 AM
>
>
>
> > To: Wouter Prins
>
>
>
> > Cc: jack daniels; Cisco certification
>
>
>
> > Subject: Re: LLQ
>
>
>
> >
>
>
>
> > If you like the voice traffic to get 1M and 1M ONLY, then, provide LLQ
> and
>
>
>
> > Police that traffic at the same time. Very common.
>
>
>
> >
>
>
>
> > On Tue, Dec 8, 2009 at 8:10 AM, Wouter Prins <wp_at_null0.nl> wrote:
>
>
>
> >
>
>
>
> > > Hello Jack,
>
>
>
> > >
>
>
>
> > > What do you think would happen to the other traffic if the voice
> traffic
>
>
>
> > > was
>
>
>
> > > allowed to burst to 2M in a LLQ?
>
>
>
> > >
>
>
>
> > > Depending on whether the interface is congested or not, the traffic
>
> would
>
>
>
> > > be
>
>
>
> > > dropped if it exceeds the bw you specify in the priority command. It's
>
>
>
> > sort
>
>
>
> > > of a conditional policer. The traffic will not end up in the default
>
>
>
> > class.
>
>
>
> > >
>
>
>
> > > 2009/12/8 jack daniels <jckdaniels12_at_gmail.com>
>
>
>
> > >
>
>
>
> > > > Hi guys,
>
>
>
> > > >
>
>
>
> > > > Please help me with the understanding of LLQ -
>
>
>
> > > >
>
>
>
> > > > If I have a link of 2 MB
>
>
>
> > > >
>
>
>
> > > > and I reserve 1 MB for VOICE ( LLQ) the if voice exceeds 1 MB will it
>
>
>
> > be
>
>
>
> > > > droppped or be sent in default class.
>
>
>
> > > >
>
>
>
> > > >
>
>
>
> > > >
>
>
>
> > >
>
>
>
> > > --
>
>
>
> > > Wouter Prins
>
>
>
> > > wp_at_null0.nl
>
>
>
> > > CCIE #25628
>
>
>
> > >
>
>
>
> > >
>
>
>
> > > Blogs and organic groups at http://www.ccie.net
>
>
>
> > >
>
>
>
> > > _______________________________________________________________________
>
>
>
> > > Subscription information may be found at:
>
>
>
> > > http://www.groupstudy.com/list/CCIELab.html
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> > >
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> > >
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> > >
>
>
>
> > >
>
>
>
> > >
>
>
>
> > >
>
>
>
> > >
>
>
>
> >
>
>
>
> >
>
>
>
> > --
>
>
>
> > Narbik Kocharians
>
>
>
> > CCSI#30832, CCIE# 12410 (R&S, SP, Security)
>
>
>
> > www.MicronicsTraining.com <http://www.micronicstraining.com/>
>
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