Catalyst Multilayer QoS - issues with Skype for Business Video calls

[steffen.bodensohn]

Hello everybody,

we want to implement Skype for Business and detected that the Video streams are not working properly. 

It seems that our switches (2960-S and X) have problems when streaming skpye video from a Gigabit port to a FA Port.

Commonly we only use priority queueing for Voice. 

The rest is default as i´m not a big fan of "Auto QoS".

For testing purpose we configured a port with queue-set 2 with max. threshold -> Video is working well withpout output drops.

This output drop counter only increases when sending UDP Skype traffic...

Did someone experience the same problem ? 

Does anyone know "best practice" values for the queue-set to configure and why is it only dropping by transmitting UDP Video traffic ? 

Anyway i want to merge the skype Video/Voice traffic in PQ together with the C-Voice stuff.

Guess this will fix the problem but i want to understand what the problem is... 

Can someone explain this behaviour? 

Best regards,

Steffen

[Nicolas Blancpain · Accepted solution]

Hi

We have had this problem (for HD only).

More than the qset-2, we've solved the issue by reserving even more buffers (60%) for the video. In my understanding, the burst of the video codec (HD) can't be handled properly with standard buffers. Notice that we can't reproduce the issue with 3750X or other higher end plateform.

Nicolas B

[steffen.bodensohn]

Yes, we mark Skype Traffic with AF41 and switch it in priority queue. 

We changed the buffer to 3200.

This also fixed the issue. 

[Nicolas Blancpain]

Here is the config we've applied, any comments are welcome :

mls qos queue-set output 1 threshold 1 2000 3000 100 3200
mls qos queue-set output 1 buffers 60 10 20 10

buffers big permanent 1000
buffers big max-free 1400
buffers big min-free 300

buffers tune automatic

ip access-list extended Kickle
 permit udp any any range 50000 59999
 permit udp any  range 50000 59999 any
 permit udp any any eq 3478
 permit udp any  eq 3478 any

class-map Kickle
 match access-group name Kickle

policy-map Kickle
 class Kickle
  set dscp 32
 

interface range fa1/0/1-48
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 service-policy input Kickle

[steffen.bodensohn]

Hi,

this is how we did it and it also seems to work :-)

mls qos map cos-dscp 0 8 16 24 32 46 48 56
mls qos srr-queue output cos-map queue 1 threshold 1 4
mls qos srr-queue output dscp-map queue 1 threshold 1 34 36
mls qos queue-set output 1 threshold 1 3200 3200 100 3200
mls qos queue-set output 1 buffers 25 65 5 5
mls qos

interface GigabitEthernet

 priority-queue out 
 mls qos trust dscp

---------

sh mls qos map

  Dscp-outputq-threshold map:
     d1 :d2    0     1     2     3     4     5     6     7     8     9 
     ------------------------------------------------------------
      0 :    02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 
      1 :    02-01 02-01 02-01 02-01 02-01 02-01 03-01 03-01 03-01 03-01 
      2 :    03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 
      3 :    03-01 03-01 04-01 04-01 01-01 04-01 01-01 04-01 04-01 04-01 
      4 :    01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 04-01 04-01 
      5 :    04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 
      6 :    04-01 04-01 04-01 04-01 

[Nicolas Blancpain]

Your config makes sense, configuring queue 1 threshold 1 for video cos 4  / dscp 34

But isn't your output wrong, showing the video packets marked AF41/DSCP34 put in queue 4 threshold 1, whereas queue 1 is the priority queue you want them in ?

sh mls qos map

  Dscp-outputq-threshold map:
     d1 :d2    0     1     2     3     4     5     6     7     8     9 
     ------------------------------------------------------------
      0 :    02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 
      1 :    02-01 02-01 02-01 02-01 02-01 02-01 03-01 03-01 03-01 03-01 
      2 :    03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 
      3 :    03-01 03-01 04-01 04-01 01-01 04-01 01-01 04-01 04-01 04-01 
      4 :    01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 04-01 04-01 
      5 :    04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 
      6 :    04-01 04-01 04-01 04-01 

[steffen.bodensohn]

Hi Nicolas,

I think the table is not in a correct format because of copy and paste:

sh mls qos map

  Dscp-outputq-threshold map:
     d1 :d2    0     1     2     3     4     5     6     7     8     9 
     ------------------------------------------------------------
      0 :    02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 02-01 
      1 :    02-01 02-01 02-01 02-01 02-01 02-01 03-01 03-01 03-01 03-01 
      2 :    03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 03-01 
      3 :    03-01 03-01 04-01 04-01 01-01 04-01 01-01 04-01 04-01 04-01 
      4 :    01-01 01-01 01-01 01-01 01-01 01-01 01-01 01-01 04-01 04-01 
      5 :    04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 04-01 
      6 :    04-01 04-01 04-01 04-01 

Best regards,

Steffen

[Nicolas Blancpain]

Steffen,

Thank you, that seems good.

Another thing : do you have a Skype server on-premise ? or are you 100% online ?

We are 100% online, and we have issues with HD conferences, I guess this is because the internet has no QOS, but we are still struggling because it seems that our infrastructure could be involved.

Nicolas

[steffen.bodensohn]

Hi Nicolas,

we have some locations that use MPLS (any-to-any) to connecto to our DC´s.

Our DC´s are also interconnected with MPLS.

But most locations are connected by regional DMVPN clouds via Internet. 

Skype connection are always done through the internal network when a devise is connected to our network. 

If the Device is not connected to the network it will connect to an S4B edge server located in one of our DMZ´s.

Further we want to Re-Design our WAN to use only Internet based DMVPN connection instead of any MPLS. My plan is to rollout "inner" tunnel QoS to priories S4B within a CB Queue. 

Also we already have some locations that can breakout to the Internet directly instead of using our centralized DC proxies.

We now want to decide if S4B conference traffic should stay within our network or connect directly to a conference server in one of our DMZ´s. 

But I´m not aware of problems regarding HD Conferences.

[Joseph W. Doherty]

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Posting

Like Steffen's thresholds, unless you really intend to have early tail drops at WTD1 and WTD2, I usually set them to be the same as max.

I've found if different ports are busy as different times, you can do (I believe) even better working more from a common pool model.  i.e. instead of reserving 100 of the bandwidth, reserve as little as possible.  This also often allows you to use the default buffer settings too unless you really need to push the max threshold higher than 320% of 25%.

[Nicolas Blancpain]

what would be your overall config then ?

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

mls qos queue-set output 1 threshold 1 3200 3200 1 3200
mls qos queue-set output 1 threshold 2 3200 3200 1 3200
mls qos queue-set output 1 threshold 3 3200 3200 1 3200
mls qos queue-set output 1 threshold 4 3200 3200 1 3200