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QOS Explanation

sreeraj.murali
Level 3
Level 3

Hi,

Request expert assistance in understanding below QOS configuration works. I have highlighted the applied QOS settings.

 

Can anyone suggest is it possible to apply similar QOS configuration, for different vlan, for prioritising Internet traffic. Please guide.

 

 

qos wireless-default-untrust

!

table-map AutoQos-4.0-Trust-Cos-Table

 default copy

table-map policed-dscp

 map from 0 to 8

 map from 10 to 8

 map from 18 to 8

 map from 24 to 8

 map from 46 to 8

 default copy

 

 class-map match-any AutoQos-4.0-Output-Multimedia-Conf-Queue

  match  dscp af41  af42  af43

  match cos  4

class-map match-any AutoQos-4.0-Output-Bulk-Data-Queue

  match  dscp af11  af12  af13

  match cos  1

class-map match-any AutoQos-4.0-Output-Priority-Queue

  match  dscp cs4  cs5  ef

  match cos  5

class-map match-any AutoQos-4.0-Output-Multimedia-Strm-Queue

  match  dscp af31  af32  af33

class-map match-any AutoQos-4.0-Voip-Data-CiscoPhone-Class

  match cos  5

class-map match-any AutoQos-4.0-Voip-Signal-CiscoPhone-Class

  match cos  3

class-map match-any non-client-nrt-class

  match non-client-nrt

class-map match-any AutoQos-4.0-Default-Class

  match access-group name AutoQos-4.0-Acl-Default

class-map match-any AutoQos-4.0-Output-Trans-Data-Queue

  match  dscp af21  af22  af23

  match cos  2

class-map match-any AutoQos-4.0-Output-Scavenger-Queue

  match  dscp cs1

class-map match-any AutoQos-4.0-Output-Control-Mgmt-Queue

  match  dscp cs2  cs3  cs6  cs7

  match cos  3

!

policy-map port_child_policy

 class non-client-nrt-class

    bandwidth remaining ratio 10

policy-map AutoQos-4.0-Output-Policy

 class AutoQos-4.0-Output-Priority-Queue

    priority level 1 percent 30

 class AutoQos-4.0-Output-Control-Mgmt-Queue

    bandwidth remaining percent 10

   queue-limit dscp  cs2 percent 80

   queue-limit dscp  cs3 percent 90

   queue-limit dscp  cs6 percent 100

   queue-limit dscp  cs7 percent 100

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Multimedia-Conf-Queue

    bandwidth remaining percent 10

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Trans-Data-Queue

    bandwidth remaining percent 10

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Bulk-Data-Queue

    bandwidth remaining percent 4

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Scavenger-Queue

    bandwidth remaining percent 1

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Multimedia-Strm-Queue

    bandwidth remaining percent 10

    queue-buffers ratio 10

 class class-default

    bandwidth remaining percent 25

    queue-buffers ratio 25

policy-map AutoQos-4.0-Trust-Cos-Input-Policy

 class class-default

   set cos cos table AutoQos-4.0-Trust-Cos-Table

policy-map AutoQos-4.0-CiscoPhone-Input-Policy

 class AutoQos-4.0-Voip-Data-CiscoPhone-Class

   set dscp ef

    police cir 128000 bc 8000

      conform-action transmit

      exceed-action set-dscp-transmit dscp table policed-dscp

 class AutoQos-4.0-Voip-Signal-CiscoPhone-Class

   set dscp cs3

    police cir 32000 bc 8000

      conform-action transmit

      exceed-action set-dscp-transmit dscp table policed-dscp

 class AutoQos-4.0-Default-Class

   set dscp default

!

 

 

!

!

!

!

 

 

interface GigabitEthernet1/0/6

 description SRI-CABIN

 switchport access vlan 40

 switchport mode access

 trust device cisco-phone

 auto qos voip cisco-phone

 spanning-tree portfast

 service-policy input AutoQos-4.0-CiscoPhone-Input-Policy

 service-policy output AutoQos-4.0-Output-Policy

 

Thanks

Sreeraj

3 Replies 3

Joseph W. Doherty
Hall of Fame
Hall of Fame
"Request expert assistance in understanding below QOS configuration works. I have highlighted the applied QOS settings."

That's a rather broad question - as books have been written about QoS. Could you elaborate on what you don't understand?

"Can anyone suggest is it possible to apply similar QOS configuration, for different vlan, for prioritising Internet traffic. Please guide."

Yes, applying a similar policy might be possible, although much depends on the platform. Further, generally speaking, the Internet doesn't support QoS.

Thank you Sir for your response.

 

The topology looks as below.

 

                                                                     (For Voice/Data traffic to US
                                                                     |-----MPLS Router-------    

                                                                     |

       ---------3850 Switch---------------
        (QOS Applied for MPLS Voice traffic      |
                                                                     |----Cisco ASA Fw-----
                                                                         (For Internet traffic)

 

->>Trying to understand, how the QOS parameter which is applied on Cisco 3850 switch, is giving priority for Cisco IP Phone traffic, and the traffic is passing through the next hop 2900 MPLS router after that.Below is the QOS specific config on 3850 switch

 

policy-map AutoQos-4.0-Output-Policy

class AutoQos-4.0-Output-Priority-Queue

    priority level 1 percent 30

 class AutoQos-4.0-Output-Control-Mgmt-Queue

    bandwidth remaining percent 10

   queue-limit dscp  cs2 percent 80

   queue-limit dscp  cs3 percent 90

   queue-limit dscp  cs6 percent 100

   queue-limit dscp  cs7 percent 100

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Multimedia-Conf-Queue

    bandwidth remaining percent 10

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Trans-Data-Queue

    bandwidth remaining percent 10

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Bulk-Data-Queue

    bandwidth remaining percent 4

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Scavenger-Queue

    bandwidth remaining percent 1

    queue-buffers ratio 10

 class AutoQos-4.0-Output-Multimedia-Strm-Queue

    bandwidth remaining percent 10

    queue-buffers ratio 10

 class class-default

    bandwidth remaining percent 25

    queue-buffers ratio 25

 

policy-map AutoQos-4.0-CiscoPhone-Input-Policy

 class AutoQos-4.0-Voip-Data-CiscoPhone-Class

   set dscp ef

    police cir 128000 bc 8000

      conform-action transmit

      exceed-action set-dscp-transmit dscp table policed-dscp

 class AutoQos-4.0-Voip-Signal-CiscoPhone-Class

   set dscp cs3

    police cir 32000 bc 8000

      conform-action transmit

      exceed-action set-dscp-transmit dscp table policed-dscp

 class AutoQos-4.0-Default-Class

   set dscp default

 

interface GigabitEthernet1/0/6

 description SRI-CABIN

 switchport access vlan 40

 switchport mode access

 trust device cisco-phone

 auto qos voip cisco-phone

 spanning-tree portfast

 service-policy input AutoQos-4.0-CiscoPhone-Input-Policy

 service-policy output AutoQos-4.0-Output-Policy

 

--->After 3850, we have also Cisco ASA Firewall as next hop for Internet traffic. and we have 2, 3 vlans configured. Is it possible to have QOS config for prioritising Internet traffic

 

Please comment.

Thanks

Sreeraj

 

 
Everyone's tags (0)
  • Data Classification:
  • Cisco Public
 
 

 

Ok, first do you understand that to provide better treatment of some traffic over other traffic (such a providing priority for VoIP traffic) you need to recognize the difference between traffic types (classification) and then "do something" that treats traffic differently?

Both classification and traffic treatment might be done upon ingress or egress. Classification is often, "by the book" done during traffic ingress, but Cisco QoS often allows classification to be done when directing traffic to an egress treatment policy. Treatment is most often done upon egress (as traffic often congests on egress ports) but some treatment, such as bandwidth enforcement might be done upon ingress.

Traffic classification can be complex and resource intensive. To diminish load upon network devices, traffic can be "tagged" with a QoS marking to ease classification. For example, rather than doing deep inspection of a packet's content, a packet can have its ToS byte set to indicate how it should be treated.

I mention the foregoing, because much of such is being done by your posted QoS policies. I.e. your 3850 is examining DSCP markings, enforcing bandwidth caps for some traffic, remarking DSCP markings, and providing different egress bandwidth guarantees and setting different drop limits. (All, it appears, part of Cisco's AutoQoS policies - which may be overly complicated for your needs and possibly even detrimental to your service requirements.) You might read Cisco's QoS material (e.g. https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoS-SRND-Book.html?dtid=osscdc000283) which should explain, at length, Cisco's QoS model.

"Trying to understand, how the QOS parameter which is applied on Cisco 3850 switch, is giving priority for Cisco IP Phone traffic, and the traffic is passing through the next hop 2900 MPLS router after that.Below is the QOS specific config on 3850 switch"

Again, unless you can be more specific, I doubt a short answer is going to help you much understand Cisco's AutoQoS implementation as their books run into hundreds of pages trying to explain it.

As to next hops, each network device is an "QoS island". You need to examine the configuration of every device, along the traffic's path, to determine how each network device will treat your traffic.
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