QOS Explanation

sreeraj.murali · ‎05-31-2018

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

Joseph W. Doherty · ‎05-31-2018

"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.

sreeraj.murali · ‎05-31-2018

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

Joseph W. Doherty · ‎06-04-2018

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.