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Community Member

QoS issue

Dear all,

i have an issue here which gives me a lot of headakes.

We have one Catlayst 6509 and one 6506. This two are linked over a 10Mbit/fdx WAN connection.

In both locations we have a Codian Lifesize Videoconference System.

This systems are marking the IP packets

voice: 101110 (EF)

video:100010 (AF41) so that i trust on all ports the dscp value (from Layer 2 to the Layer 3 interfaces). Now i have o both sides following configuration:

class-map match-all CLASSIFY-VOICE

match access-group name CLASSIFY-VOICE

class-map match-all CLASSIFY-OTHER

match access-group name CLASSIFY-OTHER

!

policy-map QoS-10Mbit

class CLASSIFY-VOICE

trust dscp

class CLASSIFY-OTHER

police 7000000 125000 125000 conform-action set-dscp-transmit default exceed-action drop

ip access-list extended CLASSIFY-OTHER

permit ip any any

ip access-list extended CLASSIFY-VOICE

permit ip any any dscp ef

permit ip any any dscp af41

!

Now to test that Qos is working we made a huge filetransfer between this locations and held in the same time a conference. The bandwith was occupying those 7Mbit as in the policy-map. The problem was that the sound and video was distorted.

Now here is the output of sh mls qos ip from both switches:

Switch 1:

sw-20-cd01#sh mls qos ip

QoS Summary [IPv4]: (* - shared aggregates, Mod - switch module)

Int Mod Dir Class-map DSCP Agg Trust Fl AgForward-By AgPoliced-By

Id Id

-------------------------------------------------------------------------------

Gi3/42 5 In CLASSIFY-V 0 1 dscp 0 800333710 0

Gi3/42 5 In CLASSIFY-O 0 2 No 0 29606082264 473387588

All 5 - Default 0 0* No 0 447495963416 0

Switch 2:

sw-10-cd01#sh mls qos ip gig1/43

[In] Policy map is QoS-10Mbit [Out] Default.

QoS Summary [IPv4]: (* - shared aggregates, Mod - switch module)

Int Mod Dir Class-map DSCP Agg Trust Fl AgForward-By AgPoliced-By

Id Id

-----------------------------------------------------------------------------------

Gi1/43 5 In CLASSIFY-V 0 1 dscp 0 1897936817 0

Gi1/43 5 In CLASSIFY-O 0 2 No 0 4534286636 4917207

I don't understand why qos doesn't work in my case. Any help/hint are much appreciated.

Thank you,

Chris

2 ACCEPTED SOLUTIONS

Accepted Solutions
Hall of Fame Super Bronze

Re: QoS issue

Your mappings are wrong, they should be:

0 8 16 26 34 46 48 56

AF41 = DSCP 34

EF = DSCP 46

Both of those values are not being mapped properly when going from COS-to-DSCP hence they aren't matching the ACL.

As illustrated in the article I posted, the internal DSCP mapping takes place when a packet enters the switchport on a 6500. If the mapping isn't correct, you won't get the expected results.

I agree with my colleagues about using priority instead of police for VoIP traffic but before addressing that subject, we need to get the markings right.

HTH,

__

Edison.

Hall of Fame Super Blue

Re: QoS issue

Chris

Remember that queueing only comes into effect at times of congestion. So if there is no other traffic on the link then there is no reason why your'e file transfer cannot use the whole link.

Jon

25 REPLIES
Hall of Fame Super Bronze

Re: QoS issue

Did you modify the switch's internal dscp-cos mappings?

What version of IOS are you running?

There are some caveats as to how dscp is trusted in the 6500.

Please take a moment and read this document:

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/qos.html#wp1705197

I believe the answer is there.

HTH,

__

Edison.

Super Bronze

Re: QoS issue

I would suggest you want to change your QoS model. Instead of policing non-realtime traffic to 70% of the link, absolute prioritize (e.g. LLQ) the realtime traffic.

Community Member

Re: QoS issue

Thank you for your responses.

Jospehdoherty, MQC/LLQ is not possible on the switch. So that commands like shape, bandwith,priority are not supported.

We have the WS-X6748-GE-TX 10/100/1000 Linecard and the SUP720B, SUP720A respectively.

Edison, no we have the default qos-dscp mapping on the switch:

Cos-dscp map:

cos: 0 1 2 3 4 5 6 7

------------------------------------

dscp: 0 8 16 24 32 40 48 56

and following IOS:

Version 12.2(33)SXH2

and

Version 12.2(18)SXF1

Chris

Hall of Fame Super Blue

Re: QoS issue

Community Member

Re: QoS issue

Hello Jon, thank you for your time. Does this mean that at the moment the port doesn's support any queing?

Take a look at the sh queing output:

sw-10-cd01#sh queueing int gig1/44

Interface GigabitEthernet1/44 queueing strategy: Weighted Round-Robin

Port QoS is enabled

Trust state: trust DSCP

Extend trust state: not trusted [COS = 0]

Default COS is 0

Queueing Mode In Tx direction: mode-cos

Transmit queues [type = 1p3q8t]:

Queue Id Scheduling Num of thresholds

-----------------------------------------

01 WRR 08

02 WRR 08

03 WRR 08

04 Priority 01

WRR bandwidth ratios: 100[queue 1] 150[queue 2] 200[queue 3]

queue-limit ratios: 50[queue 1] 20[queue 2] 15[queue 3] 15[Pri Queue]

queue tail-drop-thresholds

--------------------------

1 70[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

2 70[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

3 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

queue random-detect-min-thresholds

----------------------------------

1 40[1] 70[2] 70[3] 70[4] 70[5] 70[6] 70[7] 70[8]

2 40[1] 70[2] 70[3] 70[4] 70[5] 70[6] 70[7] 70[8]

3 70[1] 70[2] 70[3] 70[4] 70[5] 70[6] 70[7] 70[8]

queue random-detect-max-thresholds

----------------------------------

1 70[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

2 70[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

3 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

WRED disabled queues:

queue thresh cos-map

---------------------------------------

1 1 0

1 2 1

1 3

1 4

1 5

1 6

1 7

1 8

2 1 2

2 2 3 4

2 3

2 4

2 5

2 6

2 7

2 8

3 1 6 7

3 2

3 3

3 4

3 5

3 6

3 7

3 8

4 1 5

Queueing Mode In Rx direction: mode-cos

Receive queues [type = 1q8t]:

Queue Id Scheduling Num of thresholds

-----------------------------------------

01 WRR 08

WRR bandwidth ratios: 100[queue 1]

queue-limit ratios: 100[queue 1]

queue tail-drop-thresholds

--------------------------

1 100[1] 100[2] 100[3] 100[4] 100[5] 100[6] 100[7] 100[8]

queue thresh cos-map

---------------------------------------

1 1 0 1 2 3 4 5 6 7

1 2

1 3

1 4

1 5

1 6

1 7

1 8

Packets dropped on Transmit:

BPDU packets: 0

queue dropped [cos-map]

---------------------------------------------

1 738 [0 1 ]

2 0 [2 3 4 ]

3 0 [6 7 ]

4 0 [5 ]

Packets dropped on Receive:

BPDU packets: 0

queue dropped [cos-map]

---------------------------------------------

1 10 [0 1 2 3 4 5 6 7 ]

Do i have to reconfigure the 1P3Q8T queue on the line card?

Hall of Fame Super Blue

Re: QoS issue

The port has 4 transmit queue available to it, from the output

Queueing Mode In Tx direction: mode-cos

Transmit queues [type = 1p3q8t]:

Queue Id Scheduling Num of thresholds

-----------------------------------------

01 WRR 08

02 WRR 08

03 WRR 08

04 Priority 01

Queue 4 is your priority queue so you need to map your voice traffic to that queue and ensure that that queue has the bandwidth you need for the voice traffic.

Jon

Super Bronze

Re: QoS issue

Correct, that it's often the case you cannot use MQC/LLQ as you would on router, however that's why I recommended absolute priorization (like LLQ). Jon's post provides links to "how to".

Hall of Fame Super Bronze

Re: QoS issue

Your mappings are wrong, they should be:

0 8 16 26 34 46 48 56

AF41 = DSCP 34

EF = DSCP 46

Both of those values are not being mapped properly when going from COS-to-DSCP hence they aren't matching the ACL.

As illustrated in the article I posted, the internal DSCP mapping takes place when a packet enters the switchport on a 6500. If the mapping isn't correct, you won't get the expected results.

I agree with my colleagues about using priority instead of police for VoIP traffic but before addressing that subject, we need to get the markings right.

HTH,

__

Edison.

Community Member

Re: QoS issue

Hi Edison,

thank you again. I've set the right markings now on every switch (also on the Cat 2950 Edge switches)

Now the point is, that i can test the settings only on friday when the video conference room is free. Once i can test this szenario i will post the results right here.

Chris

Hall of Fame Super Bronze

Re: QoS issue

Chris,

That's great. Now, please follow my colleagues' advice and allocate priority queueing for VoIP and Bandwidth guaranteed for Video.

HTH,

__

Edison.

Community Member

Re: QoS issue

Hi Edison,

ok, so let me see if i can follow you:

now i have to allocate with following commands the priority queuing for VOIP/Video as stated in this example:

http://www.cisco.com/en/US/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoSDesign.html#wp1002136

Once i've configured it, i do not need to police the traffic with DSCP 0

Please bear with me if i do not see this things right.

Chris

Community Member

Re: QoS issue

There's something else i don't understand. From the example abowe there is following line:

CAT6500-PFC3-IOS(config-if)# wrr-queue bandwidth 5 25 70

! Sets the WRR weights for 5:25:70 (Q1:Q2:Q3) bandwidth servicing

So if i do the math the three queues Q1+Q2+Q3 are allocating 100% of the bandwith but whats the deal with the SP Queue? Q4?

Hall of Fame Super Bronze

Re: QoS issue

PFC QoS can be quite painful.

Queue4 is the priority queue and DSCP 46 / COS 5 will automatically go into that queue once you have the correct internal mappings.

I recommend reading this document on PFC QoS

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/qos.html#wp1465326

It covers most of this in detail.

HTH,

__

Edison.

Re: QoS issue

hi there

just try to make somthing like

interface GigabitEthernet3/4

wrr-queue queue-limit 40 30

wrr-queue random-detect min-threshold 1 40 80

wrr-queue random-detect min-threshold 2 70 80

wrr-queue random-detect max-threshold 1 80 100

wrr-queue random-detect max-threshold 2 80 100

wrr-queue cos-map 1 1 1

wrr-queue cos-map 1 2 0

wrr-queue cos-map 2 1 2 3 4

wrr-queue cos-map 2 2 6 7

mls qos trust dscp

switchport

switchport trunk encapsulation dot1q

switchport mode trunk

switchport nonegotiate

make sure to have the correct dscp-cos maping

and to use the right linecard config becuase each one has diffrent queues but the idea the same

good luck

HTH

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