17. Slope QoS policies

This chapter provides information to configure slope QoS policies using the command line interface.

This chapter is applicable to the 7210 SAS-Sx/S 1/10GE (standalone and standalone-VC mode), 7210 SAS-Sx 10/100GE (standalone mode), and 7210 SAS-T (network mode and access-uplink mode).

See Queue management policies for more information about configuring slope policies on the 7210 SAS-Mxp, 7210 SAS-R6, and 7210 SAS-R12.

17.1. Overview

Slope policies define WRED parameters used to manage congestion at queuing points in the network.

17.1.1. Configuration guidelines

This section provides configuration guidelines for slope QoS policies.

17.1.2. WRED support on 7210 SAS-T access-uplink and network mode, 7210 SAS-Sx/S 1/10GE, and 7210 SAS-Sx 10/100GE

Two WRED slopes are supported per queue, one each for in-profile or high-priority traffic and out-of-profile or low-priority traffic.

The hardware supports a limited amount of profiles, out of which some are reserved for system internal use and the rest is available for user configuration. It is not possible to allocate a unique profile for each and every queue available on platform. Multiple queues will need to share the same WRED profile. Software manages the allocation of hardware WRED profiles based on user configuration. It automatically allocates a single WRED hardware profile if multiple queues use the same slope parameters (that is, max-average, start-average, drop probability and time average factor). Only if these parameters differ, it allocates a different hardware WRED profile for use by the queue. A WRED profile (that is, each high-slope and low-slope) allows the user to specify the slope parameters, such as maximum average, start average, drop probability, and time average factor (TAF).

Note:

Though the WRED profile is shared among queues, the WRED state (for example, average queue size) is maintained independently for each queue in the hardware.

17.1.3. Basic configurations

A basic slope QoS policy must conform to the following:

  1. Each slope policy must have a unique policy ID.
  2. High slope, low slope and non-TCP slope are shut down (default).
  3. Default values can be modified but parameters cannot be deleted.

17.1.3.1. Create a slope QoS policy

Configuring and applying slope policies is optional. If no slope policy is explicitly applied to a port, a default slope policy is applied.

To create a new slope policy, define the following:

  1. a slope policy ID value
    The system will not dynamically assign a value.
  2. include a description
    The description provides a brief overview of policy features.
  3. The high slope for the high priority Random Early Detection (RED) slope graph.
  4. The low slope for the low priority Random Early Detection (RED) slope graph.
  5. The time average factor (TAF), a weighting exponent used to determine the portion of the shared buffer instantaneous utilization and shared buffer average utilization used to calculate the new shared buffer average utilization.

Use the following CLI syntax to configure a slope policy for 7210 SAS-T, 7210 SAS-Sx/S 1/10GE and 7210 SAS-Sx 10/100GE:

CLI Syntax:
config>qos
slope-policy name
description description-string
high-slope
start-avg percent
max-avg percent
max-prob percent
no shutdown
low-slope
start-avg percent
max-avg percent
max-prob percent
no shutdown
time-average-factor taf

The following displays the slope policy configuration for 7210 SAS-T, 7210 SAS-Sx/S 1/10GE and 7210 SAS-Sx 10/100GE:

*A:hw_sass_duth>config>qos>slope-policy# info detail
----------------------------------------------
            no description
            queue "1"
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
# 

17.1.3.2. Applying slope policies

Apply slope policies to the egress buffer pool on the access and network ports.

17.1.3.2.1. Ports

The following CLI syntax examples may be used to apply slope policies to ports:

CLI Syntax:
config>port>access>egress>pool>slope-policy name
config>port>network>egress>pool>slope-policy name

17.1.4. Default slope policy values

The default access egress and network egress policies are identified as policy-id “default”. The default policies cannot be edited or deleted. The following table displays default policy parameters:

 
A:ALA>config>qos# slope-policy default 
A:ALA>config>qos>slope-policy# info detail 
----------------------------------------------
            description "Default slope policy."
            queue "1" 
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit                      
            queue "2" 
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "3" 
                high-slope            
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "4" 
                high-slope
                    shutdown
                    start-avg 70      
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "5" 
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75       
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "6" 
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope             
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "7" 
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50      
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "8" 
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75       
                exit
                time-average-factor 7
            exit
----------------------------------------------
A:ALA>config>qos>slope-policy#

17.2. Service management tasks

17.2.1. Deleting QoS policies

A slope policy is associated by default with access and network egress pools. A default policy may be replaced with a non-default policy, but a policy cannot be entirely removed from the configuration. When a non-default policy is removed, the policy association reverts to the default slope policy policy-id default. A QoS policy cannot be deleted until it is removed from all ports where it is applied or if the policies are using the slope-policy.

ALA-7>config>qos# no slope-policy slopePolicy1
MINOR: QOS #1902 Slope policy has references
ALA-7>config>qos#

17.2.1.1. Ports

The following CLI syntax examples can be used to remove slope policies from ports:

CLI Syntax:
config>port>access>egress>pool# no slope-policy name
config>port>network>egress>pool# no slope-policy name

17.2.1.2. Remove a policy from the QoS configuration

To delete a slope policy, enter the following command:

CLI Syntax:
config>qos# no slope-policy policy-id
Example:
config>qos# no slope-policy slopePolicy1

17.2.2. Copying and overwriting QoS policies

You can copy an existing slope policy, rename it with a new policy ID value, or overwrite an existing policy ID. The overwrite option must be specified or an error occurs if the destination policy ID exists.

CLI Syntax:
config>qos> copy {slope-policy} source-policy-id dest-policy-id [overwrite]

The following output displays the copied policies for:

 
A:ALA-7210M>config>qos#
----------------------------------------------
...
      description "Default slope policy."
            queue "1"
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "2"
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "3"
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "4"
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
            queue "5"
                high-slope
                    shutdown
                    start-avg 70
                    max-avg 90
                    max-prob 75
                exit
                low-slope
                    shutdown
                    start-avg 50
                    max-avg 75
                    max-prob 75
                exit
                time-average-factor 7
            exit
...
----------------------------------------------
A:ALA-7210M>config>qos#
 

17.2.3. Editing QoS policies

You can change existing policies and entries in the CLI or NMS. The changes are applied immediately to all services where this policy is applied. To prevent configuration errors copy the policy to a work area, make the edits, and then write over the original policy.