qos cbwfq+wred doubts

reaven · ‎07-15-2016

I have a doubt i am implementing qos on my network from different remote sites to my hq connected through MPLS. the parent policy is applied to the output of two subinterfaces. the markingTraffic policy is appied to the input of the lan interface

do I have to or benefit from enable wred on each class ?

by this configuration does my classes get "priority" over the default class and the drop mechanisms is based on the dscp classification ?

ip access-list extended voip
 permit udp any any range 16384 32767
 permit tcp any any eq 1720
ip access-list extended first-Traffic
 permit tcp any any range 34560 34567
ip access-list extended second-Traffic
 permit tcp any any eq 81234
 permit tcp any any range 65432 65439
!
class-map match-any VOIP
 match access-group name voip
 match ip dscp ef
 match protocol h323
 match protocol rtp audio
class-map match-any FT
 match access-group name first-Traffic
class-map match-any ST
 match access-group name second-Traffic
!
!
policy-map outTraffic
 class VOIP
 priority percent 10
 class FT
 bandwidth percent 30
 random-detect dscp-based
 class ST
 bandwidth percent 30
 random-detect dscp-based
 class class-default
 fair-queue
 random-detect dscp-based
!
policy-map parent
 class class-default
 shape average 1000000
 service-policy outTraffic
!
policy-map markingTraffic
 class VOIP
 set ip dscp ef
 class FT
 set ip dscp af31
 class ST
 set ip dscp af31
 class class-default
 set ip dscp default

Joseph W. Doherty · ‎07-15-2016

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Posting

Different IOS versions (and sometimes platform differences) impact how CBWFQ apportions bandwidth. As you didn't name what platforms and IOS versions you're using, cannot say how non-default classes will compete with class-default, especially as the latter is using FQ (which operates quite a bit differently based on IOS version).

Your WRED settings apply to the class they are configured on. (BTW, unless you're a QoS expert, I suggest you don't use WRED. [In theory it's great - in practice, it's very often not so great.])

reaven · ‎07-15-2016

Cisco c881

Cisco IOS Software, C880 Software (C880VOICE-UNIVERSALK9-M), Version 15.1(4)M4

so you recommend leave it with tail drop

Joseph W. Doherty · ‎07-16-2016

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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 wha2tsoever (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

With your router and software, my recommendation would be to use FQ per class. That supports per flow tail drop.

reaven · ‎07-16-2016

You mean drop wred and use fair queue per class ?

Can you briefly explain why

i know my implementation seems simple compared to others but will wred make problems in this case ?

Joseph W. Doherty · ‎07-16-2016

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 wha2tsoever (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

You mean drop wred and use fair queue per class ?

Correct.

Can you briefly explain why

"briefly" - not easily.

Conversely could you briefly explain how WRED will serve your QoS goals?

I see you've only enabled WRED, so your router's default WRED settings are best possible for you?

i know my implementation seems simple compared to others but will wred make problems in this case ?

Unsure how your implementations compares to other implementations matters - what usually matters is does it do what you need it to do for you.

Will WRED make problems? Difficult to say. It might, it might not.