Cisco Nexus 7000 Series NX-OS Quality of Service Configuration Guide, Release 5.x

Ingress Queuing

You use the ingress queuing to partition the port ingress buffers that are 1.25 MB and an additional 256 KB (a total of 1.5 MB) to absorb the frames in transit after pause has been sent. This buffer is partitioned among the eight CoS values. The number of partitions is fixed for a given network qos template. The incoming CoS values are mapped to each partition. Each buffer partition is considered as an ingress queue.

There is a high threshold and a low threshold at which the pause or resume frames are generated when a threshold is met. This requirement is applicable to the no-drop CoS only. The frames that are in transit are absorbed by a skid buffer after a pause is generated. If the number of frames exceed the skid buffer threshold, the frames are tail dropped. There are three thresholds for drop eligible (DE), non-DE, and Bridge Protocol Data Unit (BPDU) frames for dropping. For the drop CoS, the high and low thresholds are the same.

The default policy ingress queues are created as follows:

• Different queues per drop class:

Drop queue =70% buffers; no-drop queue = 30% buffers

• Different queues for priority and nonpriority CoS in a given drop class:

Nonpriority queue= 90% buffers; priority queue = 10% buffers.

Each network qos policy has a corresponding default ingress queuing policy (template) and is automatically activated for the system. They are default-4q-8e-in-policy, default-4q-7e-in-policy, default-4q-6e-in-policy, and default-4q-4e-in-policy.

The predefined class map names (queue names) for ingress queuing are described in Table 9-1 .

Note ● The naming conventions of the queue are similar to the M1 modules. Also, the process for referring to queuing class maps and changing cos to queue maps is also similar to M1 modules.

• When a port becomes part of a port channel, the port inherits the policy of the port channel. When the port is moved out of the port channel, the default system queuing policy gets activated on the port.

The default queuing policy maps the priority and non-priority CoS values of the same class into different queues. However, you can configure a different CoS to queue mapping as needed. You can configure the CoS to queue map on the default VDC but the configuration is applicable system wide.

For example, in an 8e template, the network-admin may want to treat CoS 7 as a non-priority CoS and map it to the non-priority queue.

In the ingress class-map, you can modify the match cos value using the match cos command to configure the desired cos to queue mapping.

Note Modifying the default queuing policy maps is a disruptive operation and it may can cause frame drops.

You can assign a bandwidth percentage to each ingress queue. The CoS values (priority group) of each queue and its bandwidth are relayed to the peer using the DCBXP.

With the Enhanced Transmission Selection (ETS; specifies scheduling of queues based on priority) implementation, when you define both the drop and no-drop classes in a non-8e network qos policy template, the queuing follows a hierarchical pattern. In a hierarchical queuing pattern, queues within a class are configured with respect to the buffer at the first level, and buffers across the queuing groups are configured at the second level.

You use the queue-limit command to tune the ingress queue sizes (buffers). You can define the percentage of the total buffer to be allocated to the queue. For more information about the queue-limit command, see the Cisco Nexus 7000 Series NX-OS Quality of Service Command Reference, Release 5.x.

You use the bandwidth command to control the bandwidth allocated to the traffic classes (CoS) in the ingress queue. The bandwidth allocated to a traffic class in the ingress queue does not impact the switch. Instead, it sends the bandwidth information to the peer as an indication of the bandwidth for the traffic classes (CoS) that the peer sends. For more information about the bandwidth command, see the Cisco Nexus 7000 Series NX-OS Quality of Service Command Reference, Release 5.x.

You use the set cos command only on the default queue to make a port that is untrusted on the default queue.

Egress Queuing

You use egress queuing to determine how to schedule the traffic from the egress queues out of a port. The class map names represent queues and match cos represents the CoS values mapped to them. You can modify the egress class-map and match cos to achieve the desired CoS-to-queue mapping.

Note CoS remapping is supported only in strict F1 VDCs. It is not supported in F1/M1 mixed VDCs.

Each egress port has about 0.7 MB of buffers that are distributed equally among the 8 CoS values. A CoS has approximately 0.1 MB of buffers.

The default policy egress queues are created as follows:

• The drop and no-drop CoS must be mapped to different queues.
• The priority CoS is mapped to a strict priority (SP) queue. All the nonpriority CoS values are mapped to an (DWRR) queue.
• For all the non 8e templates, second level scheduling is used.

Note ● Egress queues are of fixed size and are not user configurable.

• There are four queues in the egress port.

Each network qos policy has a corresponding default egress queuing policy (template) and is automatically activated for the system. They are the default-4q-8e-out-policy, default-4q-7e-out-policy, default-4q-6e-out-policy, and default-4q-4e-out-policy. The flexible egress queues configuration is based on these queue types—1p3q1t-8e, 1p3q1t-7e, 3p1q1t-6e, and 2p2q1t-4e.

The predefined class map names (queue names) for egress queuing are described in Table 9-2 .

You can modify an egress CoS to queue map irrespective of the ingress CoS to queue map. using the match cos command to configure the desired cos to queue mapping.

An egress queue follows a hierarchical scheduling pattern when both drop classes are present. For more information, see the “Ingress Queuing” section. For a given network qos template, the egress queuing configuration (the number of DWRR queues, number of priority queues, the scheduling hierarchy) are fixed. You can modify the bandwidth percentage, priority level, and shaper for a given port.

You use the bandwidth command to control the bandwidth allocated to an egress queue (traffic class). For more information about the bandwidth command, see the Cisco Nexus 7000 Series NX-OS Quality of Service Command Reference, Release 5.x.

Note Bandwidth and priority are mutually exclusive on a class map (queue).

You use the priority command to specify that a class of traffic has low latency requirements with respect to other classes. You can configure the priority level to a traffic queue as high or low. Use the priority command to define multiple levels of a strict priority service model. For more information about the priority command, see the Cisco Nexus 7000 Series NX-OS Quality of Service Command Reference, Release 5.x.

The shaper can be configured with a percentage value and it can be enabled on any queue. You use the shape command to specify that a class of traffic has a maximum rate imposed on it and the outgoing traffic has a smooth output rate. In order to achieve a smooth output rate, the excess packets are retained in the queue and then scheduled for transmission later. For more information about the shape command, see the Cisco Nexus 7000 Series NX-OS Quality of Service Command Reference, Release 5.x.

Note A shaper delays excess traffic, which do not confirm to the profile, by queuing it in a buffer, to shape the flow.

Configuring an Ingress Queuing Policy

You need to modify the ingress queuing policy only if you want to change the default policy that the port inherited from the system default.

You can configure an ingress queuing policy by following steps given below.

The example in this section assumes that you are copying an 8e template queuing policy.

SUMMARY STEPS

1. qos copy policy type queuing default-4q-8e-in-policy {prefix prefix | suffix suffix}

2. (Optional) show policy-map type queuing [policy-map-name]

3. configure terminal

4. policy-map type queuing [policy-map-name]

5. class type queuing [2q4t-8e-in-q-default | 2q4t-8e-in-q1]

6. queue-limit percent [1-100]

7. bandwidth percent [1-100]

8. exit

9. service-policy type queuing input [policy-map-name]

10. (Optional) show policy-map type queuing [policy-map-name]

11. (Optional) show policy-map interface ethernet [slot/port]

DETAILED STEPS

	Command	Purpose
Step 1	qos copy policy type queuing [default-4q-8e-in-policy {prefix prefix | suffix suffix} Example: switch# qos copy policy type queuing default-4q-8e-in-policy prefix my_ switch#	Copies a system-defined queuing policy and renames it with a prefix or suffix. The policy is renamed as my_4q-8e-in-policy in this example.
Step 2	show policy-map type queuing [policy-map-name]   Example:   switch# show policy-map type queuing my_4q-8e-in	(Optional) Displays the queuing policy that you copied and renamed.
Step 3	configure terminal   Example: switch# configure terminal switch(config)#	Enters configuration mode.
Step 4	policy-map type queuing [ policy-map-name ] Example: switch(config)# policy-map type queuing my_4q-8e-drop-in switch(config-pmap-que)#	Configures the policy map of type queuing and enters policy-map mode for the policy map name that you specify. The policy map names can contain alphabetic, hyphen, or underscore characters, are case sensitive, and can be up to 40 characters.
Step 5	class type queuing [2q4t-8e-in-q-default | 2q4t-8e-in-q1]   Example: switch(config)# class type queuing 2q4t-8e-in-q-default	Configures the class map of type queuing and then enters policy-map class queuing mode.
Step 6	queue-limit percent [1-100]   Example 1: switch(config)# class type queuing 2q4t-8e-in-q-default switch(config-pmap-c-que)# queue-limit 40 Example 2: switch(config)# class type queuing 2q4t-8e-in-q1 switch(config-pmap-c-que)# queue-limit 60	Sets the queue limit for the queue. The range is from 1 to 100. Note The total queue limit for all the queues in the policy cannot exceed 100. In this example, the queue limit is set to 40 percent in the 2q4t-8e-in-q-default and 60 percent in 2q4t-8e-in-q1.
Step 7	bandwidth percent [1-100]   Example: switch(config-pmap-c-que)# bandwidth percent 10 switch(config-pmap-c-que)#	Allocates the bandwidth to the CoS values mapped to the queues for exchanging with the peer. The range is from 1 to 100. The bandwidth is set to 10 percent in this example.
Step 8	exit   Example: switch(config-cmap-que)# exit switch(config)#	Exits policy-map queue mode and enters configuration mode.
Step 9	service-policy type queuing input [policy-map-name]   Example: switch(config)# interface ethernet 5/5 switch(config-if)# service-policy type queuing input my_4q-8e-in switch(config-if)#	Applies a policy to an interface.
Step 10	show policy-map type queuing [ policy-map-name]   Example: switch# show policy-map type queuing default-4q-4e-in-policy	(Optional) Displays information about all configured policy maps or a selected policy map of type queuing.
Step 11	show policy-map interface ethernet [slot/port]   Example: switch# show policy-map interface ethernet 1/5	(Optional) Displays information about the service policy on an Ethernet interface.

Configuring an Egress Queuing Policy

You can configure an egress queuing policy.

The example in this section assumes that you are copying a 4e template queuing policy.

SUMMARY STEPS

1. qos copy policy type queuing default-4q-8e-out-policy | {prefix prefix | suffix suffix}

2. show policy-map type queuing [policy-map-name]

3. configure terminal

4. policy-map type queuing [ policy-map-name ]

5. class type queuing [1p3q1t-8e-out-pq1 | 1p3q1t-8e-out-q-default | 1p3q1t-8e-out-q2 | 1p3q1t-8e-out-q3]

6. bandwidth [percent {1-100} | remaining]

7. priority level{1 | 2}

8. shape [average | percent {1-100} ]

9. exit

10. service-policy type queuing output [policy-map-name]

11. (Optional) show policy-map type queuing [policy-map-name]

DETAILED STEPS

Ingress Queuing Policy Configuration Example

The following example shows how to configure an ingress queuing policy:

Egress Queuing Policy Configuration Example

The following example shows how to configure an egress queuing policy:

Hierarchical Queuing Policy Configuration Example