Quality of Service

This chapter describes how to identify and resolve problems related to Quality of Service (QoS).

This chapter includes the following sections:

Information About Quality of Service

QoS lets you classify network traffic so that it can be policed and prioritized in a way that prevents congestion. Traffic is processed based on how you classify it and the QoS policies that you put in place. Classification, marking, and policing are the three main features of QoS.

  • Traffic Classification—Groups network traffic based on defined criteria.
  • Traffic Marking—Modifies traffic attributes such as DSCP, COS, and Precedence by class.
  • Policing —Monitors data rates and burst sizes for a particular class of traffic. QoS policing on a network determines whether network traffic is within a specified profile (contract).

For detailed information about QoS, refer to the Cisco Nexus 1000V Quality of Service Configuration Guide, Release 4.2(1)SV2(1.1).

QoS Configuration Limits

Table 16-1 land Table 16-2 list the configuration limits for QoS.

Table 16-1 QoS Configuration Limits
Item
DVS Limit
Per Server Limit

Class map

1000

64 (with policies)

Policy map

128

16

Service policy

–

128

Table 16-2 QoS Configuration Limits
Item
Limit

Match criteria per class map

32

Class maps per policy map

64

QoS Troubleshooting Commands

The commands listed in this section can be used on the VSM to see the policies that are configured and applied on the interfaces.

Use the following commands to display configured policies and class-maps:

  • Show policy-map [policy-map-name]
  • Show class-map [class-map-name]

Use the following command to display installed policies:

  • Show policy-map interface brief

Use following commands on the VSM to see run-time information of the QOSMGR and ACLCOMP during configuration errors.

The commands to collect QOSMGR process run-time information configuration errors are as follows:

  • show system internal ipqos event-history errors
  • show system internal ipqos event-history msgs
  • show system internal ipqos port-node
  • show system internal ipqos mem-stats (to debug memory usage and leaks)
  • show system internal ipqos status
  • show system internal ipqos log (to show aborted plan information)
  • show system internal ipqos

The commands to collect ACLCOMP process run-time information configuration errors are as follows:

  • show system internal aclcomp event-history errors
  • show system internal aclcomp event-history msgs
  • show system internal aclcomp pdl detailed
  • show system internal aclcomp mem-stats (to debug memory usage and leaks)

Troubleshooting the VEM

The commands listed in this section can be used to display configured QoS policies on the VEM.

Use the following command to list all class maps and polices in use on the server:

  • module vem module-number execute vemcmd show qos node
~ # module vem 3 execute vemcmd show qos node
nodeid type details
-------- -------- --------
0 policer
cir:50 pir:50
bc:200000 be:200000
cir/pir units 1 bc/be units 3 flags 2
1 class op_AND
DSCP
2 class op_DEFAULT
 

Use the following command to list all the installed policy maps in use on the server:

  • module vem module-number execute vemcmd show qos policy
~ # module vem 3 execute vemcmd show qos policy
policyid classid policerid set_type value
-------- -------- -------- -------- --------
0 1 -1 dscp 5
2 0 dscp 0
 

Use the following command to list all service policies installed on the server:

  • module vem module-number execute vemcmd show qos pinst
~ # module vem 3 execute vemcmd show qos pinst
 
 
id type
-------- --------
17 Ingress
class bytes matched pkts matched
-------- -------------------- --------------------
1 0 0
 
2 85529 572
0
policer stats: conforming (85529, 572)
policer stats: exceeding (0, 0)
policer stats: violating (0, 0)

Debugging Policing Verification Errors

To debug a policy verification failure caused by processing on the VSM, follow these steps:

Step 1 Enter the debug aclmgr all command if the policy references an ACL.

Step 2 Enter debug ipqos all command.

Step 3 Enter the debug aclcomp all command.

Step 4 Enter the service-policy command which will execute the command once again with debug traces output to the console. This command allows you to collect logs for all operations.

Step 5 Save the Telnet SSH session buffer to a file.

 

If you are debugging a policy on a port profile, it may be easier to first install it directly on an interface.

To debug a policy verification failure on the VEM, follow these steps:

Step 1 Enter the module vem module-number execute vemdpalog clear command.

Step 2 Enter the module vem module-number execute vemdpalog sfqosagent all command.

Step 3 Enter module vem module-number execute vemdpalog start command.

Step 4 Enter the service-policy command which will execute the command once again with the DPA debug traces output to vemdpalog.

Step 5 Enter module vem module-number execute vemdpalog stop command.

Step 6 Enter the module vem module-number execute vemdpalog show all command to see the logs on console.

The output will look similar to the following:

calling add policy 81610ac len 220 classmaps 3- --> Session actions
…
Adding classmap 1 (108) with op 1 and 2 filters
…
Adding classmap 2 (116) with op 2 and 2 filters
…
Adding classmap 3 (56) with op 0 and 0 filters
…
init pinst ltl 11 policy id 0 if_index 1a020200 --> Service-policy being applied
installing pinst type 0 17 for policy 0
dpa_sf_qos_verify returned 0
…
Session commit complete and successful --> Session ending