- Cisco Employee,
1. Why do we need qos offload?
The ICL link between the satellite and the ASR9K may be oversubscribed by the access interfaces on the satellite box. Hence it is required to provide configurable QoS capabilities on the Satellite itself so that the satellite can do traffic management on its own & avoid losing high priority traffic due to congestion on the ICL.
With QoS offload we enable the host to “offload” QoS policies configured through the Host’s(ASR9000) manageability interface so that they can be programmed on the satellite switch hardware
2. What is the scope of QOS Offload functionality?
We support following as part of QoS offload functionality:
- Offload Class-map Configuration to the Satellite
- Offload Policy-map Configuration to the Satellite
- Offload Service policy to the Satellite
- Retrieve qos stats from Satellite & display on Host.
3. What satellite topologies support QoS offload?
- Hub and Spoke
- Dual Home
- Simple Ring
- L2 Fabric.
4. What interfaces are supported for QoS offload in IOS-XR 5.1.1 release?
QOS offload is supported on following Satellite interfaces:
- ICL physical
- Access physical interface.
- Access bundle interfaces.
5. In Which direction do we support QoS offload?
Qos Offload is supported for traffic flowing from satellite to host direction.
Following are supported:
- Ingress direction of Sat-access port
- Egress direction of satellite ICL port towards the host
6. In Which direction QoS offload is not supported?
Qos Offload is not supported for traffic flowing from Host to Satellite direction.
Following are not supported:
- Egress direction of Sat-access port
- Ingress direction of satellite ICL port towards the host
7. Do we support QoS Offload on Satellite interface egress and ICL ingress ?
No, we do not support qos offload for Host to satellite traffic, regular MQC can be used on the satellite access interface on the host which are programmed on the host itself.
For H&S satellite , 3 level Qos Policies are supported while for new topologies (Simple Ring and L2 Fabric only 2 level qos policies are supported)
8. Do we support QOS Offload on sub interface?
9. Do we support HQOS for Offloading on 9000V?
No, this will be supported in later releases.
10. How do we verify whether policy-map has got offloaded properly?
We can check it using “show qos status interface <interface> nv” command. If the state of the interface is “ACTIVE” then the policy-map is successfully offloaded
11. Do we get any commit failure message if certain policy-map does not get offloaded properly?
No. The only way to check this is using “show qos status interface <interface> nv”
12. What are the different Status available & what does each represent?
Policy-map is successfully offloaded.
Policy-map is not successfully offloaded due to any unsupported configuration
We land into this state when due to some reason (satellite connection lost, LC WAIT etc.), even with supported configuration policy-map does not get offloaded. It is an intermediate state of “Active” & “Inactive”
13. What are the different types of “Last operation attempted “?
Service policy is offloaded newly.
Service policy is removed.
- IN-PLACE MODIFY:
In-place modification is done to an offloaded policy
14. How to offload a service policy?
A service-policy is offloaded only if it is configured under “nv interface configuration mode”
QoS offload config for sat-access port:
interface <sat-access interface>
service-policy input policy1
QoS offload config for ICL interface
interface tenGigE <>
nv satellite-fabric-link satellite <>
service-policy output policy_test
15. How to get qos-stats information for offloaded policy-map?
“Show policy-map interface <> [input | output] nv” gives the qos-stats for offloaded policy-map
16. What is the time interval for QOS stats update?
The QoS stats are updated every 30 secs on the host
17. How to clear the stats for offloaded QOS Policies?
“clear qos counters interface <interface name> nv” clears the qos stats of offloaded policies
18. Do we get the cleared stats just after executing the clear command?
The show command doesn’t shows the cleared counters immediately after “clearing the stats”. The stats are updated once the next updated stats are available from satellite(< 30 secs)
The “show policy-map” command will have following o/p till the updated stats are received from satellite:
RP/0/RSP1/CPU0:tailnode#show policy-map interface gigabitEthernet 1000/0/0/0 nv
GigabitEthernet1000/0/0/0 direction input: Service Policy not installed
GigabitEthernet1000/0/0/0 direction output: Service Policy not installed
19. How does traffic management takes place at bundle sat-access link. Is it per Bundle or Per member link?
When any policy is offloaded on a bundle, then traffic management happens as per the policy map on per member link basis.
20. When a policy-map is offloaded on ingress direction of sat-access port to mark the traffic with a qos-group value (other than 0,6 & 7) & in the egress direction of the ICL if we don’t have a class with matching criteria for that qos-group value then will that traffic be accounted under class default ?
There is a one to one mapping between marked qos-group value & egress queuing on ICL , So only the traffic with qos-group 0 hits class default, so even if the traffic does not matches any other class it will not be accounted under class-default as it is marked with some non-zero qos-group value.
21. Do we have SNMP Support for QOS Offload?
22. Do we have XML support for QOS offload, if yes what all operation can be performed?
Yes, We support XML for QOS Offload. Config, show & clear command can be executed from XML for QOS offload.
23. Is the extra 4 byte added by satellite in case of H&S considered to calculate the qos stats on the egress direction of the ICL?
Yes. So, there are chances to see the QOS traffic rate going beyond the Line rate of the ICL.
24. How do we treat IPV6 traffic for QOS Offload?
We don’t do any classification for IPv6 traffic & it will be accounted under Default class.
25. How do we treat Multicast traffic for QOS Offload?
No classification done explicitly on basis of multicast traffic , however if any multicast traffic matches any other supported classification like Prec , DSCP etc. then it will get accounted under the corresponding class.
26. How many queues are there & what is the distribution in case of QOS Offload?
There are total 8 queues:
Queue Number Qos-group Value Reserved For
Queue-0 qos-group 0 Default Class
Queue-1 qos-group 1 User defined
Queue-2 qos-group- 2 User defined
Queue-3 qos-group-3 Priority Action
Queue-4 qos-group-4 User defined
Queue-5 qos-group-5 User defined
Queue-6 qos-group 6 Control Packet
Queue-7 qos-group 7 SDAC Packet
27. What is the reserved B/W for queue 6 & queue 7?
Following is the minimum & maximum B/W reservation for both queue 6 & 7
Queue number Minimum Reserved B/W Maximum Reserved B/W
Queue 6 1Gbps 2.5Gbps
Queue 7 50 Mbps 50 Mbps
28. How the traffic management happens for control traffic (entering through sat-access interface where qos policy is offloaded), in the egress direction of the ICL?
We cannot mark control traffic entering the sat-access port with qos-group 6. Thus we need to explicitly prioritize the control traffic, so that it is not dropped
29. Do we see any warning message during “Resource Exhaustion” case?
Yes, when all the available FP entries are used then we will get following Inactive message for any further QOS Policy offload.
Last Operation Attempted : ADD
Status : INACTIVE
Failure description : Apply Servicepolicy: policy: policy29 -- Err -1: FP resource (86) not available for the policy.
30. When we execute “show policy-map interface” command for any Bundle interface, does it display the combined stats of all member links?
When we execute “show policy-map interface” command for any Bundle interface, it displays the combined stats of all member links.
31. When we execute “clear qos stats” command for any bundle interface, does it clear the stats for all member links as well?
When we execute “clear qos stats” command for any bundle interface, it clears the stats for all member links as well.
32. When we execute “clear qos stats “command for any member link of a bundle interface, does it clear the stats for bundle interface as well?
When we execute “clear qos stats” command, it only clears the stats for that member link.
33. In Case of a Dual Home or Simple Ring, Can we have different QOS policy configuration for offload on both the Host?
No. For Dual Home and Simple Ring it is required that both the Host should be having same QOS policy configuration. It is the user responsibility to make sure both hosts have the same policy configured.
34. In case of a ring topology, how do we see the qos status & qos stats for each satellite?
“satellite ID” argument can be used to retrieve the stats, clear the stats & get the status of offloaded QOS policy per satellite wise.
35. On which interface do we support queuing action?
Only for ICL
36. What Queuing actions are supported?
Shaping and Bandwidth only
37. Which kind of policy map is supported on ICL?
Only Offloaded policymap to satellite is supported, non-offload policies are not supported on ICL.
38. What is the significance of qos-group set via QoS offload on satellite access port?
qos-group classification is an internal classification and it is local to the device where it is configured. In case of QoS offload, the qos-group will be significant for satellite only.
S/W Engineer, ASR9000
S/W Engineer, ASR9000
Santosh Sharma, CCIE #40773
S/W Engineer, ASR9000