QoS (calss-map, policy-map CHILD and Parent) Please help!!!

[ohforce55]

Hi,

I'm trying to replace 3825 router to 4331 router for circuit router.

I wonder if it's okay to config the QoS part exactly the same as the old router (3825) to the new router (4331).

My manager told me to use the QoS standard config from other router but what I heard is that

the QoS config has to be the exactly the same (even numbers) as the QoS config on PE router (Service Provider) side... 

Then I shouldn't change any QoS config?

Is it true?

And

When I looked at the config on the router that my manager asked me to use, the config is a little different... I know numbers should be different but there is a little difference still..

This is the QoS router that my manager told me to use:

policy-map VZB_ALAN_QOS_CHILD
 class ClassMapEF
  priority
  police 460500 conform-action transmit exceed-action set-dscp-transmit af31
class ClassMapVideo
 bandwidth remaining percent 40
 queue-limit 1024 packets
class ClassMapCritical
 bandwidth remaining percent 30
 class ClassMapBusiness
bandwidth remaining percent 20
 class ClassMapStandard
bandwidth remaining percent 5
 class class-default
bandwidth remaining percent 5
 set ip dscp default
 random-detect dscp-based
 random-detect dscp 0 512 1024
 queue-limit 1024 packets

policy-map VZB_ALAN_QOS_PARENT
 class class-default
  shape average 100000000 400000 0 account user-defined 24
   service-policy VZB_ALAN_QOS_CHILD

I will very appreciate if you can tell me how I should config the QoS to the new router.

Thank you!!!

This is QoS config on the old router (3825).

class-map match-any ClassMapEF
 match ip dscp cs5 ef cs6 cs7
class-map match-any ClassMapStandard
 match ip dscp cs1 af11 af12
class-map match-any ClassMapBusiness
 match ip dscp cs2 af21 af22
class-map match-any ClassMapCritical
 match ip dscp cs3 af31 af32
class-map match-any ClassMapVideo
 match ip dscp cs4 af41 af42
!
!
policy-map ATT_ALAN_QOS_CHILD
 class ClassMapEF
   priority 3000
      police 3000000 conform-action transmit exceed-action set-dscp-transmit af31
class ClassMapVideo
 bandwidth remaining percent 20
 queue-limit 1024
class ClassMapCritical
 bandwidth remaining percent 50
 class ClassMapBusiness
bandwidth remaining percent 20
 class ClassMapStandard
 bandwidth remaining percent 5
class class-default
 fair-queue
 queue-limit 1024
 set ip dscp default
policy-map ATT_ALAN_QOS_PARENT
class class-default
shape average 28200000 112800 0
service-policy ATT_ALAN_QOS_CHILD
!

[e.ciollaro · Accepted solution]

Hi ohforce55

heard is that the QoS config has to be the exactly the same (even numbers) as the QoS config on PE router (Service Provider) side...

First: ehat do you mean with numbers ? Which numbers ? DSCP, bandwidth, queue-limit ?

Qos has not always to be exactly the same on CE and PE, many time there are difference for many reason: queue-limit is related to hardware so many time is different, you could have asymmetric link so you could use different shaping/policing values on CE and PE, in upload you could have different traffic flows marked with the same DSCP  but, for some reason, you could shape some of them and probably PE wouldn't because traffic is already shaped on CE (and usually provider shape just based on DSCP)  and so one. For sure you have to mark using DSCP used by your provider.

Regarding the config they are different (note that you didn't post the class map for the new router but I suppose they are the same); the CIR in ClassMapEF is different, the bandwidth for the other class is different so they'll have different amount of bandwidth in case of congestion and, finally, class default in new config has WRED.

I can't tell you which is the right config, it depends on your goal; what I can say is that they are different and ave different effect.

Bye,

enrico

PS: please rate if useful

[ohforce55]

Hi enrico,

Thank you so much for your help!

Sorry that  I wasn't specifically explain.

Yes, the number I meant was regarding DSCP, bandwidth, and queue-limit. 

Even if I don't use the old config from 3825 to the new router but use the other router that my boss told me to look, that should be fine? 

[e.ciollaro · Accepted solution]

Hi,

Yes, the number I meant was regarding DSCP, bandwidth, and queue-limit. 

• DSCP must agree with the DSCP used by ISP otherwise you can't obtain the required QoS (ofte ISP drop packets with wrong DSCP)
• bandwidth: usually CE and PE have the same bandwidth but, as I wrote, in case of asymmetric links they should be different 
• queue-limit: its hardware specific so usually must be tuned based on your hardware and traffic

Even if I don't use the old config from 3825 to the new router but use the other router that my boss told me to look, that should be fine? 

It could be but I don't know what it is supposed to do so I can't say if it is right; the only thing I noted is the you have a priority queue with policing. As far as I know policing in a priority queue is used when you have multiple level priority queue (Multi-Level Priority Queues), in that case policing is used to avoid starvation. In this config there is just one priority queue so I think policing is useless: in case of congestion the amount of bandwidth used by priority queue will not exceed the config rate. 

Bye,

e

[ohforce55]

Thank you so much!