Re: Performance without QoS better than with QoS

schoerlin · ‎05-30-2011

Hi,

we have a Citrix Thin Client environment. Therefore we configured QoS for port 1494 to the QoS class "GOLD-APPS". If we make a trace with Wireshark, we see that the colouring of the traffic works.

Unfortunately the performance of Videos is like a slide show and the audio performance is really poor.

If I deactivate the QoS for port 1494, the performance of both are good.

In the attachment (QoS settings.txt) you see an extract of the switch config where all QoS settings are listed. Do someone find if something was configured wrong that is maybe rsponsible for the bad performance.

Thanks and best regards

Frank

paolo bevilacqua · ‎05-30-2011

QoS is rarely needed in LAN / gigabit environments.

True statement as you can find yourself running without it.

So keep you switches clean of confusing statements messing with the queuing defaults, that are perfectly fine for 99% of the applications.

Joseph W. Doherty · ‎05-30-2011

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.

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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

There's not enough information to suggest what specifcally might be "wrong". It's not clear, to me, when you contrast Citrix performance with explicity QoS tagging for that traffic, whether QoS is totally enabled/disabled or if enabled what DSCP settings map to which queues.

What you need to determine is whether the Citrix traffic is getting sufficient bandwidth, low jitter, low latency and low drops, when QoS is enabled.

You might check your MLS stats for drops.

You didn't mention what series switch you're using, but on the 3650/3750 series, default QoS buffers settings seem to often drop packets prematurely.

schoerlin · ‎05-30-2011

Thank you very much for your answer!

If I use the attached Qos configuration the following happens:

Acces List 104 gets true:

access-list 104 permit tcp any any eq 1494
access-list 104 permit tcp any eq 1494 any

The citrix traffic is classified into the class "GOLD-APPS"

class-map match-all GOLD-APPS
match access-group 104

The Citrix traffic gets a dscp value of "26" and is rewrited to value "af31".

policy-map QOS
class PLATINUM-VOICE
set dscp ef
class PLATINUM-VIDEO
set dscp af41
class GOLD-SIG
set dscp cs3
class GOLD-APPS
set dscp af31
class SILVER
set dscp af21
class SCAVENGER
set dscp cs1
class class-default
set dscp default

This seems to work fine, but the performace if you watch an video or listen to an audio stream is really poor.

After this we made a second test. Therefore we deleted one row in access list 104. The new access list configuration 104 ist:

access-list 104 permit tcp any any eq 149

After this the Citrix traffic is categorized to the default class and the video and audio files have a good performance.

We use Cisco Blade Switch 3020 for this. Not all QoS buffers are default values:

mls qos srr-queue output dscp-map queue 1 threshold 3 46
mls qos srr-queue output dscp-map queue 2 threshold 1 18 34
mls qos srr-queue output dscp-map queue 2 threshold 2 24 26
mls qos srr-queue output dscp-map queue 2 threshold 3 48
mls qos srr-queue output dscp-map queue 3 threshold 3 0
mls qos srr-queue output dscp-map queue 4 threshold 1 8
mls qos queue-set output 1 threshold 2 70 80 100 400
mls qos queue-set output 1 threshold 4 40 100 100 400
mls qos queue-set output 1 buffers 10 30 30 30
mls qos

I can`t find any drops, but I`m not sure if I use the correct command...

Thanks and best regards

Frank

schoerlin · ‎05-30-2011

Okay, I found the missconfiguration on my own.

We replaced the following row

mls qos queue-set output 1 threshold 2 70 80 100 400

with this value

mls qos queue-set output 1 threshold 2 70 250 100 400

But what does these values exactly mean? Threshold1, Threshold2....

lamav · ‎05-30-2011

Frank, I hate to do this to you, but check out this link on configuring QoS on the Cisco 3020.

http://www.cisco.com/en/US/docs/switches/blades/3020/software/release/12.2_25_sef1/configuration/guide/swqos.html

Read it in its entirety and then see if you have any questions.

Victor

Thotsaphon Lueangwattanaphong · ‎05-30-2011

Victor,

Long time no see

Good link anyway! 5p

Toshi

lamav · ‎05-30-2011

Hey, Toshi. How are you?

Yes, very long time.

I have been real busy lately and these days I have a sales engineering position, so I am not pounding the keyboard anymore. I miss it, but sales is very interesting, too. I come on here every now and then so I don;t get too rusty. :-)

VL

Thotsaphon Lueangwattanaphong · ‎05-30-2011

Victor,

I'm good. Thanks. Hope you're good too. I just got back to work with Netpro again. Nice to see you here.

Poster,

Sorry ,I'm out of topic.

Toshi

Joseph W. Doherty · ‎05-30-2011

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

schoerlin wrote:

Okay, I found the missconfiguration on my own.

We replaced the following row

mls qos queue-set output 1 threshold 2 70 80 100 400

with this value

mls qos queue-set output 1 threshold 2 70 250 100 400

But what does these values exactly mean? Threshold1, Threshold2....

I recall(?) that's the setting for taildrops for different markings in the same queue. Victor's reference should have all the details.