Configuring Quality of Service

This chapter includes the following sections:

Quality of Service

Cisco UCS provides the following methods to implement quality of service:


  • System classes that specify the global configuration for certain types of traffic across the entire system

  • QoS policies that assign system classes for individual vNICs

  • Flow control policies that determine how uplink Ethernet ports handle pause frames

System Classes

Cisco UCS uses Data Center Ethernet (DCE) to handle all traffic inside a Cisco UCS instance. This industry standard enhancement to Ethernet divides the bandwidth of the Ethernet pipe into eight virtual lanes. Two virtual lanes are reserved for internal system and management traffic. You can configure quality of service for the other six virtual lanes. System classes determine how the DCE bandwidth in these six virtual lanes is allocated across the entire Cisco UCS instance.

Each system class reserves a specific segment of the bandwidth for a specific type of traffic. This provides a level of traffic management, even in an oversubscribed system. For example, you can configure the Fibre Channel Priority system class to determine the percentage of DCE bandwidth allocated to FCoE traffic.

The following table describes the system classes that you can configure:

Table 1 System Classes

System Class

Description

Platinum

Gold

Silver

Bronze

A configurable set of system classes that you can include in the QoS policy for a service profile. Each system class manages one lane of traffic.

All properties of these system classes are available for you to assign custom settings and policies.

Best Effort

A system class that sets the quality of service for the lane reserved for Basic Ethernet traffic.

Some properties of this system class are preset and cannot be modified. For example, this class has a drop policy that allows it to drop data packets if required. You cannot disable this system class.

Fibre Channel

A system class that sets the quality of service for the lane reserved for Fibre Channel over Ethernet traffic.

Some properties of this system class are preset and cannot be modified. For example, this class has a no-drop policy that ensures it never drops data packets. You cannot disable this system class.

Quality of Service Policies

QoS policies assign a system class to the outgoing traffic for a vNIC or vHBA. This system class determines the quality of service for that traffic.

You must include a QoS policy in a vNIC policy or vHBA policy and then include that policy in a service profile to configure the vNIC or vHBA.

Flow Control Policy

Flow control policies determine whether the uplink Ethernet ports in a Cisco UCS instance send and receive IEEE 802.3x pause frames when the receive buffer for a port fills. These pause frames request that the transmitting port stop sending data for a few milliseconds until the buffer clears.

For flow control to work between a LAN port and an uplink Ethernet port, you must enable the corresponding receive and send flow control parameters for both ports. For Cisco UCS, the flow control policies configure these parameters.

When you enable the send function, the uplink Ethernet port sends a pause request to the network port if the incoming packet rate becomes too high. The pause remains in effect for a few milliseconds before traffic is reset to normal levels. If you enable the receive function, the uplink Ethernet port honors all pause requests from the network port. All traffic is halted on that uplink port until the network port cancels the pause request.

Because you assign the flow control policy to the port, changes to the policy have an immediate effect on how the port reacts to a pause frame or a full receive buffer.

Configuring QoS System Classes

The type of adapter in a server impacts the maximum MTU supported. Network MTU above the maximums may cause the packet to be dropped for the following adapters:


  • The Cisco UCS CNA M71KR adapter supports a maximum MTU of 9216.

  • The Cisco UCS 82598KR-CI adapter supports a maximum MTU of 14000.

Procedure
Step 1   In the Navigation pane, click the LAN tab.
Step 2   In the LAN tab, expand LAN > LAN Cloud .
Step 3   Select the QoS System Class node.
Step 4   In the Work pane, click the General tab.
Step 5   Update the following properties for the system class you want to configure to meet the traffic management needs of the system:
Note   

Some properties may not be configurable for all system classes.
Name Description

Enabled check box

If checked, the associated QoS class is configured on the fabric interconnect and can be assigned to a QoS policy.

If unchecked, the class is not configured on the fabric interconnect and any QoS policies associated with this class default to Best Effort or, if a system class is configured with a Cos of 0, to the Cos 0 system class.

Note   

This field is always checked for Best Effort and Fibre Channel.

Cos field

The class of service. You can enter an integer value between 0 and 6, with 0 being the lowest priority and 6 being the highest priority. We recommend that you do not set the value to 0, unless you want that system class to be the default system class for traffic if the QoS policy is deleted or the assigned system class is disabled.

Note   

This field is set to 7 for internal traffic and to any for Best Effort. Both of these values are reserved and cannot be assigned to any other priority.

Packet Drop check box

If checked, packet drop is allowed for this class. If unchecked, packets cannot be dropped during transmission.

This field is always unchecked for the Fibre Channel class, which never allows dropped packets, and always checked for Best Effort, which always allows dropped packets.

Weight drop-down list

This can be:


  • An integer between 1 and 10. If you enter an integer, Cisco UCS determines the percentage of network bandwidth assigned to the priority level as described in the Weight (%) field.

  • best-effort.

  • none.

Weight (%) field

To determine the bandwidth allocated to a channel, Cisco UCS:


  1. Adds the weights for all the channels

  2. Divides the channel weight by the sum of all weights to get a percentage

  3. Allocates that percentage of the bandwidth to the channel

MTU drop-down list

The maximum transmission unit for the channel. This can be:


  • An integer between 1500 and 9216. This value corresponds to the maximum packet size.

  • fc—A predefined packet size of 2240.

  • normal—A predefined packet size of 1500.

Note   

This field is always set to fc for Fibre Channel.

Multicast Optimized check box

If checked, the class is optimized to send packets to multiple destinations simultaneously.

Note   

This option is not applicable to the Fibre Channel.

Step 6   Click Save Changes.

Creating a QoS Policy

Procedure
Step 1   In the Navigation pane, click the LAN tab.
Step 2   In the LAN tab, expand LAN > Policies .
Step 3   Expand the node for the organization where you want to create the pool.

If the system does not include multi-tenancy, expand the root node.

Step 4   Right-click QoS Policy and select Create QoS Policy.
Step 5   In the Create QoS Policy dialog box, complete the following fields:
Name Description

Name field

The name of the policy.

This name can be between 1 and 16 alphanumeric characters. You cannot use spaces or any special characters, and you cannot change this name after the object has been saved.

Priority drop-down list

The priority assigned to this QoS definition. This can be:


  • best-effort—Do not use this priority. It is reserved for the Basic Ethernet traffic lane. If you assign this priority to a QoS policy and configure another system class as CoS 0, Cisco UCS Manager does not default to this system class. It defaults to the priority with CoS 0 for that traffic.

  • bronze—Use this priority for QoS policies that control vNIC traffic only.

  • fc—Use this priority for QoS policies that control vHBA traffic only

  • gold—Use this priority for QoS policies that control vNIC traffic only.

  • platinum—Use this priority for QoS policies that control vNIC traffic only.

  • silver—Use this priority for QoS policies that control vNIC traffic only.

Burst field

The normal burst size for servers which use this policy. This field determines how large traffic bursts can be before some traffic is considered to exceed the rate limit. The default is 10240. The minimum value is 0, and the maximum value is 65535.

Rate field

The expected average rate of traffic. Traffic that falls under this rate will always conform. The default is line-rate, which equals a value of 0 and specifies no rate limiting. The minimum value is 0, and the maximum value is 10,000,000.

Host Control field

Whether Cisco UCS controls the class of service (CoS). This can be:


  • None—Cisco UCS uses the CoS value associated with the priority selected in the Priority drop-down list regardless of the CoS value assigned by the host.

  • Full—If the packet has a valid CoS value assigned by the host, Cisco UCS uses that value. Otherwise, Cisco UCS uses the CoS value associated with the priority selected in the Priority drop-down list.

Step 6   Click OK.
What to Do Next

Include the QoS policy in a vNIC or vHBA template.

Deleting a QoS Policy

If you delete a QoS policy that is in use or you disable a system class that is used in a QoS policy, any vNIC or vHBA which uses that QoS policy is assigned to the Best Effort system class or to the system class with a CoS of 0. In a system that implements multi-tenancy, Cisco UCS Manager first attempts to find a matching QoS policy in the organization hierarchy.

Procedure
Step 1   In the Navigation pane, click the LAN tab.
Step 2   On the Servers tab, expand Servers > Policies > Organization_Name.
Step 3   Expand the QoS Policies node.
Step 4   Right-click the QoS policy you want to delete and select Delete.
Step 5   If Cisco UCS Manager GUI displays a confirmation dialog box, click Yes.

Creating a Flow Control Policy

Before You Begin

Configure the network port with the corresponding setting for the flow control that you need. For example, if you enable the send setting for flow-control pause frames in the policy, make sure that the receive parameter in the network port is set to on or desired. If you want the Cisco UCS port to receive flow-control frames, make sure that the network port has a send parameter set to on or desired. If you do not want to use flow control, you can set the send and receive parameters on the network port to off.


Procedure
Step 1   In the Navigation pane, click the LAN tab.
Step 2   On the LAN tab, expand LAN > Policies.
Step 3   Expand the root node.

You can only create a flow control policy in the root organization. You cannot create a flow control policy in a sub-organization.
Step 4   Right-click the Flow Control Policies node and select Create Flow Control Policy.
Step 5   In the Create Flow Control Policy wizard, complete the following fields:
Name Description

Name field

The name of the policy.

This name can be between 1 and 16 alphanumeric characters. You cannot use spaces or any special characters, and you cannot change this name after the object has been saved.

Priority field

This can be:


  • auto—Cisco UCS and the network negotiate whether PPP is used on this fabric interconnect

  • on—PPP is enabled on this fabric interconnect

Receive field

This can be:


  • off—Pause requests from the network are ignored and traffic flow continues as normal

  • on—Pause requests are honored and all traffic is halted on that uplink port until the network cancels the pause request

Send field

This can be:


  • off—Traffic on the port flows normally regardless of the packet load.

  • on—Cisco UCS sends a pause request to the network if the incoming packet rate becomes too high. The pause remains in effect for a few milliseconds before traffic is reset to normal levels.

Step 6   Click OK.
What to Do Next

Associate the flow control policy with an uplink Ethernet port or port channel.

Deleting a Flow Control Policy

Procedure
Step 1   In the Navigation pane, click the LAN tab.
Step 2   On the LAN tab, expand LAN > Policies > Organization_Name.
Step 3   Expand the Flow Control Policies node.
Step 4   Right-click the policy you want to delete and select Delete.
Step 5   If Cisco UCS Manager GUI displays a confirmation dialog box, click Yes.