RE: LLQ from Tony Varriale on 2009-12-08 (Ccielab archives 12/2009)

From: Tony Varriale <tvarriale_at_flamboyaninc.com>
Date: Tue, 8 Dec 2009 16:06:58 -0600

Is this supposedly the same in 12.4 main and T?

I have a couple 2800s with a T1 running 12.4(22)T that I will test tonight.

From: Narbik Kocharians [mailto:narbikk_at_gmail.com]
Sent: Tuesday, December 08, 2009 2:47 PM
To: Tony Varriale
Cc: Cisco certification
Subject: Re: LLQ

The LLQ threshold kicks in ONLY if there are congestion, if there are NO
congestion, the traffic assigned to that class will go through but it won't
be Low Latency queued. If you like to limit the traffic to the value
referenced in the "Priority" command, regardless of congestion. You MUST
ALSO Police the traffic.

On Tue, Dec 8, 2009 at 12:36 PM, Tony Varriale <tvarriale_at_flamboyaninc.com>
wrote:

I think based on SOME of the testing that's been posted here that's not
necessary. Hence, my post for clarification.

Simply restating what the docs say is easy. Anyone tested this on IOS?
Maybe try 12.4T and 12.4 mainline?

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of

Edison Ortiz
Sent: Tuesday, December 08, 2009 2:24 PM
To: 'Cisco certification'
Subject: RE: LLQ

"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."

Correct. If you want to police a class with LLQ under all conditions
(congestion or not) - as Narbik noted add the police command under that
class as well.

Edison Ortiz

Routing and Switching, CCIE # 17943

_____

From: karim jamali [mailto:karim.jamali_at_gmail.com]
Sent: Tuesday, December 08, 2009 3:17 PM
To: Edison Ortiz; Cisco certification
Subject: 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

> >

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> >

> > _______________________________________________________________________

> > Subscription information may be found at:

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> >

> --

> Narbik Kocharians

> CCSI#30832, CCIE# 12410 (R&S, SP, Security)

> www.MicronicsTraining.com <http://www.micronicstraining.com/>
<http://www.micronicstraining.com/>

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Received on Tue Dec 08 2009 - 16:06:58 ART

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